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Full text of "The chemistry of the non-benzenoid hydrocarbons and their simple derivatives"

CORNELL 

UNIVERSITY 

LIBRARY 




FROM 



Y.Earapetoff 



Er:G!NEERlNG 



_ Cornell University Library 

QD 305.H5B87 



The chemistry of the non-benzenoid hydro 




3 1924 004 631 168 




Cornell University 
Library 



The original of tiiis bool< is in 
tine Cornell University Library. 

There are no known copyright restrictions in 
the United States on the use of the text. 



http://www.archive.org/details/cu31924004631168 



THE CHEMISTRY OF 

THE NON-BENZENOID 
HYDROCARBONS 

And Their Simple Derivatives 



BY 
BENJAMIN T. BROOKS, Ph.D. 



First Edition 



BOOK DEPARTMENT 
The CHEMICAL CATALOG COMPANY, Inc. 

ONE MADISON AVENUE, NEW YORK, U. S. A. 
1922 



CoPTKiQHT, 1922, By 

The CHEMICAL CATALOG COMPANY. Inc. 

All Rights Reserved 



Press ol 

J, J. Little & Ives Oompany 

New York. U. S. A. 



PEEFACB 

The beautiful, interesting, and often facile chemistry of the benzene 
hydrocarbons has somewhat overshadowed the chemistry of the ali- 
phatic open chain and cyclic non-benzenoid hydrocarbons. Certainly 
the chemistry of the former series has been much more fully rounded 
out. Judging from the customary method of treatment accorded them 
in our textbooks, there is some confusion in the arrangement of subject 
matter which does not give the student a proper idea of the close re- 
lationships and similarity of chemical behavior possessed by all the 
non-benzenoid hydrocarbons. Mr. Wells, in his "Outline of History," 
says: "There is a natural tendency in the human mind to exaggerate 
the differences and resemblances upon which classification is based, to 
suppose that things called by different names are altogether different, 
and that things called by the same name are practically identical. 
This tendency to exaggerate classification produces a thousand 
evils, . . ." This tendency, which Mr. Wells deplores, is well shown by 
the use of the term "hydro-aromatic" hydrocarbons and the classifi- 
cation of cyclohexane and its derivatives with benzene. This term is 
still employed for cyclohexane and its simple derivatives, although 
its behavior is almost identical with that of normal hexane. The same 
applies to cyclopentane and its simple derivatives as compared with 
normal pentane, yet cyclopentane cannot be termed a "hydro-aromatic" 
hydrocarbon. Cycloheptane, cyclooctane, cyclononane, cyclobutane 
and cyclopropane should certainly be classed and described together 
with cyclohexane, as indeed Aschan and a few others have done. The 
differences in chemical properties between benzenoid ring systems and 
NON-BENZENOID hydrocarbons are well established, but in spite 
of the enormous amount of work done, have not yet received adequate 
explanation. 

'' As regards the aliphatic hydrocarbons proper, these fare very badly 
in most works on organic chemistry, particularly in the briefer text- 
books. Usually, the entirely erroneous statement, or implication, is 
made that the so-called type reactions given for the first two or three 
members of the methane series hold good for the higher members. •' Be- 
yond the fact that all of them may be completely burned to carbon 

3 



4 PREFACE 

dioxide and water, such statements are hardly in accord with the 
known facts. We note that the chemistry of the first five members of 
the methane series and also the ten carbon atom or terpene group, 
mostly cyclic hydrocarbons, have been much more extensively and 
carefully studied than the remainder. Some of the reasons for this 
are fairly apparent. Thus, the essential oils afford a convenient source 
of substances of the terpene group which may generally be isolated 
easily in a state of purity. The natural fatty glycerides or other con- 
venient sources readily yield a limited number of fatty acids, nearly 
all of them normal, i. e., acids of one, two, three, four, five, six, eight, 
ten, twelve, fourteen, sixteen, eighteen, and twenty-four carbon atoms. 
Research in many of these special fields has accordingly been greatly 
facilitated by the availability of suitable material and has often been 
much stimulated by an intimate relation to industry. 

It may also be pointed out that while in the aromatic series a rich 
variety of raw materials may easily be isolated or prepared, crystal- 
line derivatives are almost the rule, permitting easy purification, iden- 
tification, and manipulation in small quantities; that substitution re- 
actions are usually capable of control to form chiefiy one product or 
a very limited number of products or isomers; but in the aliphatic 
series this is not the case. Petroleums probably contain all of the nor- 
mal parafiine hydrocarbons up to CagHg^ and perhaps farther in the 
series, and perhaps hundreds of naphthenes which are for the most 
part yet unknown. Not only is it at present impossible to isolate pure 
individual substances from this complex raw material, but few methods 
of synthesis applicable to the higher members of the aliphatic series 
or the more complex naphthenes have been developed. 

The reader seeking only material of industrial interest may object 
to the inclusion of much subject matter which is solely of theoretical 
interest and the searcher who scorns industrial processes will find much 
in the present volume that is unorthodox. The author desires to make 
no apology for the inclusion of both classes of subject matter; the de- 
scription of any special subject of science should be systematic if we 
are to retain our conception of science as classified knowledge, and the 
author does not feel that descriptions of industrial processes and refer- 
ences to patent literature detract from the value of the compilation, 
considered as a scientific monograph. In a treatise of purely industrial 
purpose the checker-board plan, in which economic value determines 
exclusion or inclusion of subject matter, may perhaps be justified, but 
the author believes that the best results will be obtained by broader 



PREFACE 5 

scientific treatment of industrial subjects. The author is well aware 
that patent literature, in spite of oaths and notaries' seals, is not bound 
by the same standards of truth that govern the publication of purely 
scientific papers and has accordingly treated such matter critically and 
with caution. 

The mechanical art and engineering of petroleum refining has been 
perfected to a degree which, measured by profit and general utility, 
deserves commendation, but it is a development which has been very 
little dependent upon chemical knowledge. More thorough knowledge 
of the chemistry of the non-benzenoid hydrocarbons will surely re- 
sult in better and less wasteful methods of refining and may lead to the 
conversion of petroleum hydrocarbons into other useful products by 
chemical methods. In the present state of our knowledge, it would be 
rash to prophesy what may be accomplished in this direction; but be- 
fore much work of this kind can be done, a great deal of painstaking, 
systematic research in the field of thenon-benzenoid hydrocarbons must 
be carried out which may never be utilized directly in an industrial 
process. The writer does not urge research in this field solely on the 
ground of the utility of the possible results. Those who attempt to 
justify scientific research by financial returns do not always have a 
very strong case, and to attempt to balance any particular industry 
upon the point of an original scientific discovery is to leave out of ac- 
coimt the contributions of a host of other people, which the scientist 
seldom appreciates. Such arguments convince nobody and often arouse 
the resentment of engineers and business men and others who know 
better. The upbuilding of a great mass of information and generaliza- 
tions, new experimental methods and. new substances, in the field of 
the non-benzenoid hydrocarbons, will enable industry to select certain 
bits of knowledge suited to further progress and our everyday welfare. 
Every original investigator making real contributions to the fabric of 
knowledge is thus a contributor to the common weal. This, while 
not the sole justification of research, is the correct form of the argu- 
ment of the utility of scientific investigation. 

This point of view has a very direct bearing on the question of re- 
search in the field of the non-benzenoid hydrocarbons. The petroleum, 
rubber, turpentine and essential oil industries stand in need of further 
systematic theoretical research in this field of chemistry. Work along 
broad lines, involving the work of a great many investigators for a 
great many years, is required. American chemists have heretofore 
played a singularly insignificant part in this field of research and to 



6 PREFACE 

realize this it is only necessary to mention the names of Wallach, Sir 
William H. Parkin, Jr., Semmler, Engler, Grignard, Sabatier and the 
Russian group, Ipatiev, Kishner, Markownikow, Wagner, Konowalow, 
Zelinsky, Aschan, Bredt, Ostromuislenski, Lebedev, Gustavson, Char- 
itschkov, and others. All of these men have exercised their influence 
in universities or technical schools, and the inference may accordingly 
be drawn that we must look to our American universities, rather than 
to the petroleum or other industrial interests, to initiate and carry on 
such research in America. And if the American petroleum industries 
second their efforts, as the Nobel Brothers have done in Russia, a vast 
amount of work of permanent scientific and potential industrial value 
can be done. 

The present monograph is not a catalog of all the hydrocarbons 
which might be described. The writer has endeavored to show the 
close relationships which hold generally throughout the chemistry of 
the non-benzenoid hydrocarbons and, on the other hand, to point out 
that the chemical behavior of the more complex hydrocarbons of the 
paraffine series and the alicyclic hydrocarbons cannot be assumed from 
the chemical behavior of a few of the simpler hydrocarbons. The chem- 
istry of the ethylene bond is emphasized because of its great impor- 
tance and because most of our knowledge of its behavior under dif- 
ferent circumstances and influences is empirical. 

Much important work has been done since the appearance about 
twenty years ago of Aschan's "Alicyclische Verbindungen" and Semm- 
ler's admirable volumes on the terpenes and this work has been briefly 
reviewed and the attempt has been made to treat it in such a way that 
will be helpful in wider fields of organic research. 



TABLE OF CONTENTS. 

PAGE 

Chapter I. The Pakaffines 13 

1. Occurrence of the parafiSnes in nature. — a. Natural gas; 
composition, behavior under pressure ; separation of the con- 
stituents. — b. Petroleum: difficulty of isolating simpler 
members of the paraffine series: paraffines produced by bio- 
logical processes; general character and probable mode of 
origin of petroleums. — c. Other natural sources of paraffines. ' 
— 2. Formation of the paraffines. — a. Pyrolysis of organic 
matter; effects of heat on non-benzenoid hydrocarbons; oil 
gas; formation of aromatic hydrocarbons; the gasoline prob- 
lem. — b. Synthesis of the paraffines.- — Alkyl halides and 
metallic couples; the Grignard reaction; reduction of alco- 
hols or alkyl iodides by hydriodic acid; catalytic hydro- 
genation of olefines; miscellaneous special methods. 

Chapter II. Chemical Properties of Saturated Hydro- 
carbons 52 

1. Oxidation; conversion of paraffine wax to fatty acids by 
air oxidation; hardening of petroleum residuums by blowing 
with air. — Other oxidizing reagents: 2. Behavior to nitric 
acid; nitration with dilute nitric acid. — 3. Alkyl halides. — 
General methods for preparing alkyl chlorides, bromides and 
iodides; dissociation of the simpler alkyl halides by heat; 
behavior of alkyl halides to alcoholic alkali; general reac- 
tions. 

Chapter III. The Paraffine Hydrocarbons .... 76 
1. Methane; oxidation; inflammability; chlorination ; syn- 
thesis from water gas or carbon monoxide. — 2. Ethane, 
propane, butanes. — 3. The pentanes; hexanes; heptanes. — 
4. Octanes; synthesis of octanes as typical of methods now 
known; nonanes and decanes. — 5. Paraffines CioHjj to 
CeoHiaa; paraffine wax from petroleum. — 6. Table: Physi- 
cal properties of the paraffines. — 7. Notes on the refining of 
petroleum distillates. 

Chapter IV. The Ethylene Bond Ill 

1. Recent conceptions of valence and the ethylene bond; 
Baeyer's strain theory; stability of the ethylene bond and 

7 



TABLE OF CONTENTS 

carbocyclic structures. — 2. Chemical properties of unsatu- 
rated substances of the ethylene type. — a. Modification of 
the chemical behavior of the ethylene bond by substituents ; 
influence of the double bond on the chemical behavior of 
substituents. — b. Addition reactions, halogens, halogen 
acids, hypochlorous acid, aqueous mineral acids and the 
addition of water. — c. Unsaturated hydrocarbons and sul- 
furic acid; refining of petroleum oils. — d. Auto-oxidation. — 
e. Reaction with sulfur and sulfur chloride; vulcanization 
of rubber. — f. Ozonides: Use of ozone in determining con- 
stitution. — g. Properties of the HC = CH — CO group.— 
h. Addition reactions frequently used for identification of 
unsaturated hydrocarbons; nitrosyl chloride, nitrous acid; 
use of nitrosyl chloride for the synthesis of ketones. — 
i. Other substances which combine with the ethylene bond, 
aniline, urea, hydrogen - sulfide, hydrocyanic acid, etc. — 
3. The preparation of unsaturated hydrocarbons: Decom- 
position of saturated hydrocarbons, alcohols and organic 
halides by heat; barium soaps and sodium eth oxide; the 
Grignard reaction; exhaustive methylation of amines. 



Chapter V. The Acyclic Unsaturated Hydrocarbons . . 158 

1. Ethylene, physical properties, chemical behavior; pro- 
duction from acetylene, from ethyl alcohol; coal gaa, oil 
gas; catalytic oxidation to formaldehyde; PP-dichloroethyl 
sulfide; reaction with sulfuric acid and the industrial syn- 
thesis of alcohol; Hofmann and Sand's ethanol compounds. 
— 2. Propylene; physical properties and general chemical 
behavior and rules of addition; industrial propyl alcohols. 
— 3. Butylenes and amylenes; chemical behavior. — 4. Ole- 
fines, six to nine carbon atoms; diflBculty of synthesis or 
separation, of pure hydrocarbons. — 5. Decene's and ali- 
phatic terpenes; myrcene, ocimene and allo-ocimene. — 6. 
Derivatives of 2 . 6-dimethyl-octane ; the citral group; gera- 
niol and citral a nerol and citral b; linalool; citronellol; 
a- and P-ionone; irone. — 7. Sesquicitronellene ; spinacene. — 
8. Cholesterylene and its relation to cholesterol. 



Chapter VI. Polymerization of Hydrocarbons . . . 210 

1. Substituted ethylenes and the effect of substituents on 
polymerization; the conjugated dienes, their chemical be- 
havior and the synthesis of rubbers. — 2. The constitution of 
rubber, its depolymerization; review of research on the syn- 
thesis of rubber; raw materials and the question of indus- 
trial synthesis.— -3. Methods of polymerization. 



TABLE OF CONTENTS 9 

PAOB 

Chapter VII. Cyclic Non-benzenoid Hydrocaebons . . 233 

1. General methods of synthesis. — ^By polymerization of un- 
saturated hydrocarbons; decomposition of calcium and 
barium salts of dicarboxylic acids; condensation of dicar- 
boxylic acid esters by sodivun; by sodium and malonic acid 
ester; the Grignard reactions; dihalogen derivatives and 
sodium; disodium derivatives of carboxylic acids and iodine 
or bromine ; ring closing by elimination of water from alde- 
hydes; diazoacetic ester and the synthesis of cyclopropane 
derivatives; condensation of nitriles by sodium ethylate to 
imino compounds and their hydrolysis; Kishner's hydrazine 
method; hydrogenation of benzenoid hydrocarbons. — 2. 
Cyclopropane and its simple derivatives. — 3. Cyclobutane 
and its simple derivatives.— -4. Cyclopentane and its simple 
derivatives. — a. Syntheses from cyclopentanone. — b. Naph- 
thenic acids, synthetic and from petroleums. — c. Substi- 
tuted cyclopentanes. 

Chapter VIII. Cyclic Non-benzenoid Hydrocaebons: The 

Cyclohexane Series 278 

1. The hydrogenation of benzene; catalytic production of 
cyclohexanols and cyclohexanone ; cyclohexene and cyclo- 
hexadienes. — 2. Alkyl derivatives of cyclohexane, synthetic 
and from petroleum; cantharene. — 3. Mono-cyclic sesqui- 
terpenes. 

Chapter IX. Cyclic Non-benzenoid Hydrocarbons: The 

Para-menthane Series 315 

1. Limonene and dipentene; carvomenthene ; para-men- 
thane; the constitution of limonene; syntheses of limonene 
and the terpineols. — 2. Terpinolene and the terpinenes; 
Semmler's carvenene. — 3. Crithmene. — 4. The oxides; gen- 
eral behavior of oxides; 1.8-cineol, 1.4-cineol, pinol and 
ascaridol. — 5. Other menthenols. — 6. Menthol; stereochem- 
istry of menthol and menthone; the menthenones, piperi- 
tone and pulegone; Buchu camphor; carvone. — 7. The phel- 
landrenes. 

Chapter X. Cyclic Non-benzenoid Hydrocarbons: Ortho- 

AND MeTA-MENTHANE DERIVATIVES 384 

1. Sylvestrene; Its synthesis from carvone; Perkin's syn- 
thesis. — 2. Ortho-menthane derivatives; synthesis by Per- 
kin. 



10 TABLE OF CONTENTS 



PAOE 



Chapter XI. Cyclic Non-benzenoid Hydrocarbons: Bicyc- 

Lic AND Tricyclic Hydrocarbons 396 

1. Santene. — 2. Sabinene, thujene and carene. — 3. Tetra- 
hydro and decahydronaphthalene. — 4. Hydrogenation of 
indene, anthracene and phenanthrene. — 5. Nomenclature of 
bicyclic and tricyclic hydrocarbons. — 6. Bicyclic and tri- 
cyclic sesquiterpenes. 

Chapter XII. Bicyclic Non-benzenoid Hydrocarbons: The 

Pinenes and Fenchenes 420 

1. Character of commercial turpentines. — 2. Constitution of 
a-pinene; chemical reactions of a-pinene. — 3. Beta-pinene; 
synthesis and constitution. — 4. Bornyl chloride and its de- 
composition products. — 5. Pinolene; tricyclene; the fen- 
chenes. 

Chapter XIII. Bicyclic Non-benzenoid Hydrocarbons : Cam- 

phene, Bornylene and Camphor 453 

1. Review of research of the constitution of camphene and 
bornylene. — 2. a. Camphor; constitution of camphor and 
its oxidation products; camphoric and related acids. — 
b. Epicamphor. — c. Derivatives of camphor. — 3. Synthetic 
camphor. — a. Plantation camphor vs. synthetic camphor. — 
b. The preparation of bornyl chloride; conversion of bornyl 
chloride to camphene, bornyl acetate and borneol; hydra- 
tion of camphene to borneol. — c. Other processes for the 
conversion of pinene to borneol; the Thurlow and similar 
processes. — d. Oxidation of the borneols; impurities in syn- 
thetic bomeols and camphor. 

Chapter XIV. Cyclic Non-benzenoid Hydrocarbons: Cyclo- 
heptane, Cyclo-octane, Cyclononanb and Polynaph- 
thenes 511 

1. Cycloheptane ; cycloheptene, cycloheptadiene and cyclo- 
heptatriene. — 2. Cycloheptanone ; eucarvone. — 3. Cyclo- 
octane; cyclo-octotetrene. — 4. Cyclononane. — 5. Polynaph- 
thenes; lubricating oils. 

Chapter XV. Rearrangements 624 

Cyclobutane and cyclopentane derivatives; a-pinene and 
bornyl chloride; cyclobutyl amine to cyclopentanol ; cyclo- 
pentane and cyclohexane derivatives; Meerwein's researches 
on pinacones; borneol and camphene. 



TABLE OF CONTENTS 11 

PAGE 

Chapter XVI. Physical Propeeties 538 

1. Density and molecular volume; melting-point and boil- 
ing-point. — 2. Optical properties; absorption of light, color 
and fluorescence; molecular refraction and influence of 
structure on ref ractivity ; molecular dispersion; magnetic 
rotation; optical activity and methods of synthesis of opti- 
cally active hydrocarbons; optical activity of petroleum. — 
3. Thermochemistry of the non-benzenoid hydrocarbons; 
specific heat; latent heat of vaporization; heat of combus- 
tion. — 4. Dielectric constants; static charges of oils pro-V* 
duced by friction; transformer oils. — 5. Viscosity; effect of \ 
ring closing on viscosity; viscosity of petroleum oils; vis- 
cosity and lubrication; effect of dissolved paraffine on vis- 
cosity of oils. — 6. Solubility; petroleum fractions in other 
solvents; parafiine wax in various solvents; terpene hydro- 
carbons in dilute alcohol; solubility of methane and other 
gases in oils; sulfur in petroleum oils; dissolved sulfur in 
rubber; liquid sulfur dioxide as a solvent for unsaturated 
hydrocarbons and Edeleanu's refining process. — 7. Colloids; 
greases and jellies; emulsions; adsorption and the use of 
fuller's earth; fractional separation of hydrocarbons by 
fuller's earth. 

Chapter XVII. Physiological and Related Properties . 591 

1. Odor. — 2. Physiological effects; narcotic action of the 
simpler hydrocarbons; terpene alcohols and ketones; nat- 
ural and synthetic camphor; halogen derivatives of the 
paraffines. 



Chapter I. The Paraffin es 

In any systematic treatment of the non-benzenoid hydrocarbons, 
it is difficult to subdivide the subject matter into divisions or chapters, 
which do not unduly emphasize minor class differences. Thus cyclo- 
hexane is not ordinarily considered as a paraffine or saturated hydro- 
carbon although its chemical behavior might very properly place it in 
this class. On the other hand, the cyclopropane ring frequently ex- 
hibits properties of unsaturation which are nearly identical with those 
characteristic of the ethylene bond. However, since a discussion of the 
hydrocarbons of the series CnHgn+a may rationally serve as a ground 
work, this series will be considered first. 

Occurrence of the Paraffines. 

From the economic standpoint by far the most important natural 
sources of the paraffine hydrocarbons are natural gas ^ and petroleum. 
The industrial utilization of natural gas has been practically limited 
to the United States, although the Chinese may claim priority as re- 
gards its first industrial use since old Chinese writings describe its 
collection from shallow dug wells, piping through tubes of bamboo and 
burning for the evaporation of brine. 

Since practically all the natural gas produced in the United States 
is consumed as fuel or burned for the production of carbon black, very 
little attention has been paid to its chemical composition. In rare in- 
stances natural gas contains as much as 95 per cent methane but an 
average gas contains about 85 per cent methane, 1.0 to 3 per cent 
nitrogen and 12 to 15 per cent ethane and other paraffines. Unusual 
geological conditions, but little understood, result in gases containing 
large percentages of nitrogen, hydrogen sulfide or carbon dioxide. Hy- 
drogen sulfide is normally not a constituent of natural gas but is fre- 
quently encountered in gases in the Gulf Coast territory. Nitrogen 
occurs in the gas of the northern Texas fields to the extent of about 38 
per cent and it is of interest to note that this gas also contains helium 

• In 1917 the consumption of natural gas In the United States was 795 billion 
cubic feet. (Northrop in Westcotts' "Handbook of Natured Gas," p. 106.) 

13 











B.T.U.per 










ou. ft. 


aa 


CO. 


N. 


0, 


(760 mm. 


% 


% 


% 


% 


o-c.) 


0.0 


0.8 


3.2 


0.0 


1,022 


6.2 


0.8 


6.2 


0.0 


1,040 


4.5 


0.8 


3.4 


0.0 


1,066 


15.2 


0.0 


4.9 


0.0 


1,134 


18.1 


0.0 


1.5 


0.0 


1,193 


20.6 


0.1 


9.9 


0.0 


1,062 


4.1 


0.4 


3.4 


0.0 


1,057 


20.7 


0.3 


12.5 


0.0 


1,093 


10.4 


0.1 


38.2 


0.0 


740 


0.9 


, , 


11.2 


, , 


. • • • 



14 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

in amounts sufficient for its extraction on a large scale for filling dirig- 
ible balloons. The composition of natural gas is usually reported in 
terms of methane and ethane, these percentages being derived by cal- 
culation from the results of combustion in an explosion pipette. That 
hydrogen does not occur in natural gas is now generally accepted, 
Philipps ^ having shown that the early analyses in which hydrogen 
was reported, were faulty. Typical analyses reported by Burrell and 
Oberfell ^ are as follows: 

Typical Analyses op Natural Gas. 



CH4 
Source of Gas % 

Texarkana, Ark 96 

Noblesville, Ind. ....... 86.8 

Leavenworth, Kan 91.3 

Erie, N. Y 79.9 

Columbus, 80.4 

Guthrie, Okla 69.4 

Muskogee, Okla 92.1 

Pawhuska, Okla 66.5 

Fort Worth, Tex.* 51.3 

Bow Island, Canada* ... 87.6 

The percentages of methane, ethane, propane and higher methane 

homologues can be determined accurately by fractional distillation at 

low temperatures.^ Thus a sample of natural gas supplied to the city 

of Pittsburgh in 1915 was shown to have the following composition: 

Methane 84.7 per cent. 

Ethane 9.4 '_' ''_ 

Propane 3.0 

Butane and other hydrocarbons 1.3 " " 

Nitrogen 1-6 " 

In recent years the practice of removing the light gasoline vapors, 
mostly butane, pentane and hexane, by absorption and compression 
methods has become almost universal, at least where large gas supplies 
are available. High pressure gas from new fields contains relatively 
very little gasoline vapor, the highest yields being obtained from low 
pressure gas associated with petroleum.^ The removal of gasoline va- 

'Am. Chem. J. JS, 406 (1894). 

»U. S. Bur. Mines. Techn. Paper 109. , ,., ^ , u . 

» This gas in northern Texas contains about 0.9% helium which Is being separated 
at the U. S. Government plant at Petrolia, Texas. The Canadian gas contains 0.33% 

* "'"Burrell, Selbert & Robertson. U. S. Bur. Mines. Techn. Paper lOi (1915). 

• The yield of gasoline obtained by absorption methods from so-called dry gas 
Is from 5 to 0.75 gallons per 1000 cubic feet. When the initial gas pressure Is 
300 to 500 pounds per square inch the yield of gasoline by the absorption method 
Is about 3 gallon per 1000 cubic feet. The compression method alone is not employed 
when the gas contains less than 0.75 gallons of gasoline per thousand cubic feet 
of gas. 



THE PARAFFINES 15 

pors slightly lowers the fuel value of the gas, normally one gallon of 
gasoline per 1000 cubic feet lowering the calorific value of the gas 
about 5 per cent/ The yield of carbon black is considerably dimin- 
ished by the removal of gasoline vapors from the gas. In common 
practice the average yield of carbon black was about 1 pound per 750 
cubic feet when very rich, low pressure gas was employed for this pur- 
pose. The behavior of natural gas under pressure is of industrial im- 
portance from another standpoint, i. e., the measuring or metering of 
gas under pressure. Although the gas pressure of new wells in new 
fields may be as high as 1600 pounds per square inch, it is usually 
necessary to compress the gas from lower pressures to about 650 pounds 
per square inch for transmission through long pipe lines. Methane 
deviates considerably under pressure, from the behavior of a perfect 
gas and Amagat ° has shown that at 40 atmospheres it is about 9 per 
cent more compressible and at 100 atmospheres is 17 per cent more 
compressible than a perfect gas. Burrell and Robertson " have shown 
that the average natural gas is considerably more compressible than 
pure methane, at 35.5 atmospheres this deviation amounting to about 
15 per cent as compared to the compressibility of a perfect gas. 

The fuel value of natural gas is commonly given as 1000 B.T.U. 
per cubic foot measured at 0°C but owing to the presence of ethane 
(1719 B.T.U. per cubic foot) and other hydrocarbons, the value 1100 
B.T.U. is a better average value. Since in ordinary fuel practice the 
water formed in the combustion is practically never condensed, the 
latent heat of evaporation of this water should be deducted to give a 
net heating value.^" 

Ethane, propane and butane may easily be separated from natural 
gas in conjunction with the removal of gasoline vapors and, as Burrell 
and Robertson have shown, each of these hydrocarbons may be 
isolated in a very pure state by fractional distillation at low tempera- 
tures. In view of the low cost of the separation of oxygen and nitro- 
gen by liquid air methods, it is certain that pure ethane, propane and 
butane could be made available in large quantities at very low cost. 
These hydrocarbons are not now utilized (other than as fuel), but 
research in the direction of their chemical utilization is in progress. 

'Dow. U. S. Bur. Mines. Techn. Paper 2SS (1920). 

' Landolt &. Bomstein. Physikaliache Tabellen, 190S, 65. 

•U. S. Bur. Mines, Techn. Paper lOi (1915). 

"Richards, "Metallurgical Calculations," Ed. 1918, p. 25, gives the net heating 
value of 970 B. T. TJ. for methane, the water formed remaining uncondensed. Cf 
Waidner & Mueller, "Industrial Calorimetry," tJ. S. Bur. Standards, Techn. Paper Se 
(1914). 



16 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The deviation of ethane, propane and butane from the behavior of 
a perfect gas is, of course, greater than is the case with methane, and 
when compressing gas mixtures containing all of these hydrocarbons, 
as in the separation of gasoline from natural gas by compression, the 
behavior is the resultant of many factors and the most efficient method 
of operating a compression plant for the production of gasoline can, 
at the present time, be determined only by experiment." According 
to well understood principles, when the pressure on a gas, containing 
condensable vapors is increased, the partial pressure of the vapor in- 
creases until its saturation pressure is reached at which point conden- 
sation to liquid begins. Thus if a gas is saturated with pentane vapor 
at atmospheric pressure, compression to two atmospheres will, liquefy 
one-half of the pentane; if the partial pressure of the pentane is origi- 
nally one-tenth the saturation pressure, then compression to ten atmos- 
pheres will be required to reach the saturation point and this pressure 
must then be doubled, i.e., to twenty atmospheres, to liquefy one- 
half the pentane. But when other condensable hydrocarbons are pres- 
ent, these simple relations no longer hold true. The importance of re- 
moving the heat resulting by compression is indicated by the accom- 
panying figures showing the vapor pressure curves of the simpler nor- 
mal paraffine hydrocarbons. See also vapor pressure curves of the 
simpler parafiBnes on page 88. 

Few petroleums consist mainly of hydrocarbons of the paraffine 
series, but the lighter, low boiling fractions of most petroleums consist 
of these hydrocarbons almost exclusively. Particularly is this true of 
light Pennsylvania oil. Since much of the earlier chemical work on 
petroleum was carried out with distillates of this particular oil, it is 
often erroneously stated that "American" petroleum consists of paraf- 
fines and "Russian petroleum" consists of naphthenes and polynaph- 
thenes of the series CnH2n,CnH2n_ a, etc. Generally it may be said that 
the petroleums of no two producing regions are the same. Although 
the petroleum typical of the Pennsylvania field probably contains the 
largest per cent of paraffines, the higher boiling, viscous fractions of 
this crude contain but a few per cent of G^Jl^n+z hydrocarbons and 
these are removed by chilling, thus manufacturing the "paraffine wax" 
of commerce. Lubricating oil derived from Pennsylvania and other 
petroleums consists chiefly of hydrocarbons of the class CaHan-s/^ but 
their structure is unknown and no pure individual hydrocarbons have 

"Mabery, Am. Ohem. J. 1905, 231. 

" Anderson, J. Ind. & Eng. Chem. IB, 547 (1920) ; Dykema, U. S. Bur. Mines. 
Bull. ISl (1918). 



THE PARAFFINES 



17 



been isolated from them. Vaseline isolated from Pennsylvania pe- 
troleum, is a mixture of hydrocarbons of the empirical formulae 

Ceerees Fahrenheit. 

-13 +32 77 122 167 212 257 302 347 392 437 432 527 572 
50 



45 



u 30 



20 









*■ Critical Zi.i" 50 At. 

1 fCrltlcol 102° 46,3 At. 




















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625 




































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c 


























588 
551 
514 
478 
441 
404 
367 
331 
7Q1) 






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9 










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/ 




JO 1 
^ 1 




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Crlllcnl 235° 30 At. 






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/ Critical 267°26.9 At 






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-50 -25 



25 50 



75 100 125 150 175 200 225 250 275 300 
Degrees Centigrade. 



Vapor pressure curves of the simpler parafflne hydrocarbons. (W. O. Snelling 
In Hamor and Padgett's "Examination of Petroleum.") 



C.H,„_, and CJl, 



Petroleums from certain American fields con- 



tain no paraffines, for examples, Coates " has shown that the lighter 
distillates of the oil from the Jennings, Louisiana, field consist exclu- 
sively of cyclic hydrocarbons of the CJl^n series. 

"J. Am. Ohem. Soc. 28^ 384 (1906). 



18 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The paraffine wax of commerce consists of a mixture of hydro- 
carbons of the paraffine series from about CjjH^e to C^e^^t. The 
natural waxes of the ceresin type are evidently not normal paraffines 
but isomeric hydrocarbons probably identical with the amorphous wax 
of petroleum oils (see below) . 

The number of hydrocarbons which have been isolated from petro- 
leum is very small. The old procedures, which supplied chemical lit- 
erature with a formidable array of names, empirical formulae and 
boiling-points, consisted in carefully fractioning a quantity of petro- 
leum and collecting fractions boiling between narrow limits. Formulae 
and names were then assigned to these fractions on the basis of com- 
bustion analyses and molecular weight determinations. The extremely 
careful work of Young shows how very difficult the separation of only 
two hydrocarbons may be when the diSierence in boiling-points is as 
much as 8°, as in the case of n.pentane and isopentane. Young and 
Thomas i* were able to separate n . pentane and isopentane in fairly 
pure condition only after thirteen fractional distillations through a 
very efficient dephlegmating column, and Young states that he was not 
able to isolate pure heptanes from light petroleum ether by fractional 
distillation. He regards the presence of n.hexane and isohexane in 
American and Russian petroleums as established, but the presence 
of other hexanes is open to question. Markownikow was able to 
isolate cyclohexane and methyl cyclopentane in fairly pure state from 
Baku oil by a combination of chemical treatments and fractional dls- 
tillation.i^ In the course of his work, Young showed that benzene and 
hexane form a constant boiling mixture boiling at 65°-66°. Although 
the distillation of two closely related hydrocarbons, for example, two 
members of the series CnHjn, 2, as a constant boiling mixture is very 
improbable yet it is a possibility. Also owing to the fact that the 
boiling-points of a series of isomers may extend over a wide range, 
for example 22° in the case of the hexanes, it is evident that the prob- 
lem of isolating pure hydrocarbons from petroleum distillates is practi- 
cally a hopeless one, except in very simple cases as noted above. 

Paraffine hydrocarbons are produced in a variety of biological proc- 
esses. The best known example of this method of their production is 
methane, the name "marsh gas" referring to its formation in bogs 
where cellulose undergoes anaerobic fermentation. The amylobacteria 

"J. Am. Chem. Boo. 71, 440 (1897). 

"Aschan, Ber. SI, 1801 (1898). Markownikow, Ann. SOI, 154 (1898); Ber. SO, 
1532 (1897). 



THE PARAFFINES 19 

of van Tiegham,!* evolve methane from cellulose and in this fermenta- 
tion the other major products are carbon dioxide and the simple fatty 
acids.^^ Whether small proportions of other gaseous hydrocarbons are 
simultaneously produced has not been determined. As regards the 
theory of the biological origin of natural gas and petrolemn, the for- 
mation of methane from buried cellulose material is capable of experi- 
mental duplication but this cannot yet be said of the higher homo- 
logues. 

Normal heptane has been obtained from the "petroleum nuts" 
Pittosporum resiniferum of the Philippines,^* from the oleoresin of 
Pinus sabiniana and the wood turpentine of Pinus jeffreyi}^ The 
higher paraffines occur in small quantity in many essential oils. Com- 
mercial rose oil contains sufficient paraffine or "stearoptene" to sepa- 
rate in large crystals, on chilling. This crude stearoptene has been 
separated into paraffines melting at 22° and 40° to 41°. Heptacosane 
C27H56 and hentriacontane Ca^Hg^ occur in bees' wax ^° and the latter 
hydrocarbon also occurs in the resin of tobacco and the leaves of Gym- 
nema sylvestre, Olea europcea or the European olive, an African vine 
Morinda longiflora and Lippia scaberrina.^'^ According to Meyer and 
Soyka [Monatshefte, 34, 1159 (1913)], candelilla wax, used in making 
phonograph records, contains about 74 to 76 per cent of do-triacontane, 
CgaHsj. Small quantities of crystalline paraffine wax also occur in 
certain eucalyptus oils, e. g.. Eucalyptus paludosa and Eucalyptus 
smithii.^^ Pentatriacontane CggHja melting at 74.5°-75°' occurs in the 
leaves of Eridictyon calijornicumP Pentacontane, CgoHio;;, has been 
found in Lancashire coal. Altogether several tons of dark colored wax 
were found which after purification and decolorizing melted at 92.7°- 
93° and boiled at 420°^22° under 15 mm. pressure. This hydro- 
carbon is the highest homologue of the paraffine series which has been 
found occuring naturally.^* 

The Character and Probable Mode of Origin of Petroleums. 

The development of the petroleum industry had its beginnings 
almost coincident with the very rapid development of organic chem- 

"Compt. rend. 88, 205 (1879). ,,„„„^ 

"Lafar: Tech. Mykologie. Vol. III. 260 (1906). 

"Bacon, Philip J. 8ci. i, 115 (1909). 

>" Sohorger, J. Ind. d Eng. Chem. 7, 24 (1915). 

MSchwalb, Ann. 855, 110 (1886). 

"Power & Tutln, J. Chem. Soc. 91, 1916 (1907) ; 9S, 874 (1908). 

=2 Smith, J. Chem. Ais. 106, 399 (1914). 

M Power & Tutin, J. Chem. Soc. Abs. 90, 885 (1906). 

" Slnnatt & Barash, Inat. Min. Eng. 1919, Nov. 11. 



20 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

istry. The petroleum industry was largely an American development 
but extensive research in organic chemistry was for long carried out 
almost exclusively in Europe, which is one reason for the comparative 
neglect of petroleum research. Also during these earlier years few 
American chemists had the facilities and time at their disposal neces- 
sary for research. Most American chemists of that period were an- 
alytical chemists, with the result that the earlier investigations of pe- 
troleum consisted in laboriously fractioning petroleum distillates and 
christening the various fractions normal undecane, normal dodecane, 
etc., etc. With the exception of the notable pioneer work of Mabery 
very little work of permanent value was done on petroleum in America 
during this long period. 

Young demonstrated ^^ the presence of n . pentane and isopentane 
in petroleum, also the presence of n.hexane and isohexane and n. hep- 
tane and isoheptane, but considered the presence of isomeric hex- 
anes and heptanes as probable but not proven. The presence of 
cyclo-hexane, methyl-cyclopentane " and a limited number of homo- 
loglies has been proven in the case of light naphtha from Baku oil. The 
isolation of a fraction having a constant boiling-point is not necessarily 
indicative of a pure single hydrocarbon. Two isomers, or two totally 
different hydrocarbons may have practically identical boiling-points.^' 
Five of the known octanes boil within the range 114°-118°. Con- 
stant boiling mixtures are also known, the separate constituents of 
which may have quite different boiling-points. For example, pure 
n.hexane boils at 68.95° and benzene at 80.2°, but a mixture of the 
two containing 10 per cent benzene boils at 69° and a mixture contain- 
ing 27.3 per cent benzene at 69.5°. This behavior of benzene and 
hexane explains the fact that on nitrating petroleum fractions contain- 
ing benzene, the fraction yielding the most dinitrobenzene is that 
boiling at 60°-65°, not that boiling at 75° to 85°. For a similar rea- 
son the fraction 90°-100° contains more toluene, when this is a minor 
constituent, than the fraction distilling at 105°-115°. 

All petroleums which contain paraffine hydrocarbons as the chief 
constituents of their lighter fractions, as the Pennsylvania, Mid-Conti- 
nent, and light Texas crudes, show a rapidly increasing per cent of 
naphthenes as the boiling-point rises with successive fractions. In the 
light lubricating fractions the parafiBne hydrocarbons, series CnHan 2, 
seldom exceeds three per cent and after their removal by chilling, re- 

="/. Chem. 800. 7S, 907 (1898). 

"Young, loc. cit.; Markownikow, Ber. SO, 1222 (1897). 

"Jackson & Xoung, /. Chem. Soe. 73. 926 (1898). 



THE PARAFFINES 21 

suiting in the parafEne wax of commerce, the lubricating oil remaining 
is practically free from hydrocarbons of this class. ParafiEine wax of 
commerce, melting ordinarily from 48° to 62° C, consists chiefly of a 
mixture of hydrocarbons of 23 to 28 carbon atoms. The melting- 
points and boiling-points of some of the definitely known parafRne 
hydrocarbons are given in the following table: 

BOIUNG-POINTS OF HyDROCAKBONS OF THE PaBAFFINE SeRIES. 



Formula 


Name 




Boiling-Point °i 


CiHio 


n. butane 




— 0.1 


it 


isobutane 




— 10.5 


GkHu 


n. pentane 




-f 36.3 


It 


isopentane 




27.95 


it 


tetramethyl-methane 




9.5 


ca. 


n. hexane 




68.95 


fi 


2 methyl pentane 




62. 


it 


3 methyl pentane 




64. 


ti 


23 dimethyl butane 




49.6 -49.7 


It 


2.3 " " 




• 58.08 


C7H14 


n. heptane 




98.2 -98.5 


u 


2 methyl hexane 




89.9 -90.4 


ti 


3 " " 




90. '-92. 


It 


trimethyl methane 




95. -98. 


it 


2.2 dimethvl pentane 




78. 


it 


2.4 




83. -84. 


tt 


3.3 




86. -87. 


G,H« 


n. octane 




125.8 


it 


2 methyl heptane 




116. 


it 


3 " " 




117.6 


Mbming-Points and Boiung-Points of 


Hydrocarbons of the 


Paraffine Serh 


Formula 


Name 


Boiling-Point °C 


Melting-Point ° 


CsHis 


i methyl heptane 


118. 




It 


2.4 dimethyl hexane 


109.8-110. 




tt 


2.5 " 


109.2 




tt 


3.4 " " 


116. -116.2 




tt 


diethyl-isopropyl methane 


114. 




tt 


2.2.3.3.tetramethyl butane 


106. -107. 


-t-103. 


C0H20 


n.nonane 


149.5 


— 51. 


tt 


3 methyl octane 


142.4-143.4 




it 


4 ethyl heptane 


138. -139. 




tt 


2.5 dimethyl heptane 


133. -137. 




tt 


2.6 


132. 




C10H23 


n.decane 


173. 


—32. 


(( 


2.6 dimethyl octane 


156.5-158. 




tt 


2.7 


159.6 




tt 


3.6 " 


159.8-160.8 




CuHm 


n.undecane 


194.5 


— 26.5 


C12H26 


n.dodecane 


214.5 


— 12. 


tt 


2.4.5.7 tetramethyl octane 


208. -210. 




CisHjs 


n.tridecane 


234 


— 6.2 


CwHao 


n.tetradecane 


252.5 


+ 5,5 


C15H82 


n.pentadeeane 


270.5 


+ 10. 


CieHjM 


n.hexadecane 


287.5 


+ 19. -20. 


tt 


7.8 dimethyl tetradecane 


263. -265. 


below —30° 



22 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

MEI/nNQ-PoiNTS AND BoiUNG-PoiNTS OF HYDROCARBONS OF THE PaRAFFINB SeRIES. 



Formula 


Name 


Boiling-Point °C 


Melting-Point "C 


CirHse 


n.heptadecane 


303. 


+ 22.5 


CisHss 


n.octadecane 


317. 


28. 


ClgHlO 


n.nonadecane 


330. 


32. 


C2oH4a 


n.eikosane 


205. (15mm.) 


36.7 


CaHrt 


n.heneikosane 


215. (15mm.) 


40.4 


C22H<a 


n.dokosane 


224.5(15mm.) 


44.4 


C23H4S 


n.trikosane 


234. (15mm.) 


47.7 


CaHto 


n.tetrakosane 


240. (15mm.) 


51.5 


CmHh 


n.hexakosane 




56.6 



Owing to the fact that paraffine wax does not crystallize readily in 
well formed crystals; even from crude petroleums which are free from 
asphaltic matter, until after distillation, it has been supposed that the 
crystalline parafBne is at least partly derived from a parent substance, 
"proto-parafEne," which breaks up during distillation and thereby 
yields the freely crystallizing paraffine wax.^' Rakuzin ^^ has shown 
that crude petroleums contain soft, medium and hard paraffines of 
crystalline structure. Marcusson '^ slowly distilled ceresine thereby 
decomposing it to a mixture of well crystallized paraffines and liquid 
hydrocarbons. The substance known to the refiners as amorphous wax 
and which gives much trouble to the wax manufacturer, may possibly 
be ordinary paraffine, whose crystallization is interfered with by col- 
loids, substances capable of gelatinizing on chilling or may in fact con- 
sist of paraffine derivatives, "proto-paraffines," for example, naph- 
thenes having very long paraffine side chains which on pyrolysis yield 
crystalline paraffine wax and an unsaturated naphthene or its polymers. 
A better method of separating or destroying amorphous wax is a 
problem of first importance to the refiners, but the real nature of 
amorphous wax has not been determined. The most definite informa- 
tion on this point is contained in a recent paper by Marcusson ^^ who 
showed that amorphous wax is probably identical with ceresine and 
there is considerable evidence that ceresine consists of a mixture of 
branched chain or zsoparaffines, a hypothesis first put forward by Za- 
loziecki.^^ Heretofore ceresine has generally been regarded as a mix- 
ture of the higher normal paraffine homologues. Marcusson com- 
pared the physical and chemical properties of a crystalline paraffine 
and a refined natural ceresine of practically identical melting points. 

"ZalozlecW, Z. t. angew. Chem. 1888, 126. 

"J. Buss. Phys..Chem. Soc. ISU,, 1544; J. O'lem. 80c. Ais. 108, 489 (1914). 

" Chem. Ztg. 191S, 581, 613. 

" Ohem. Ztg. WIS, 613. 

"Z. angew. Ohem. 1S8S, 126. 



THE PARAFFINES 23 

Paraffine Ceresine 

Melting-point 56.5° -60.5° 57.5° -60.1° 

Solidifying-point 59.2° 59° 

Sp. Gr. at 15° 0.885 0.917 

Sp. Gr. at 60° 0.781 0.798 

Mol. Wt 330. 420. 

ParafiBne is harder than ceresine in penetration tests, is markedly 
more soluble and is less viscous than ceresine at 70°. Paraffine is only 
slightly attacked by fuming sulfuric acid, 33% SO3, at ordinary tem- 
peratures, but ceresine is energetically attacked. The action of nitric 
acid is also more energetic on ceresine. On dissolving paraffine in hot 
mineral oil and then cooling, the paraffine crystallizes out but with 
ceresine, under the same conditions, a vaseline-like deposit is obtained. 
Marcusson has examined the distillation products of ceresine and the 
oily product consists of a mixture of saturated hydrocarbons and ole- 
fines of low molecular weight. No evidence of the presence of naph- 
thenes was obtained. 

The formation of branched chain hydrocarbons or so-called iso- 
paraffines may possibly be explained by the decomposition of montan 
wax, which as shown by Meyer and Brocl ^* consists chiefly of an acid, 
CjgHseOj, and a solid alcoholic wax. This acid of montan wax is not 
a normal chain fatty acid but a branched chain compound. 

Paraffine is formed during the distillation of asphalt base oils by 
the, decomposition of the asphaltic matter. This is in accord with the 
observation that large amounts of crystalline paraffine are contained 
in shale oil, the wax not being present as such in the original shale 
but formed by the decomposition of the complex kerogen of the shale ; 
also the distillate obtained by the low temperature distillation of coals 
rich in volatile matter contains crystalline paraffine, which is not pres- 
ent as such in the original coal. 

In addition to the problem of separating simple mixtures of hydro- 
carbons by fractional distillation and the separation of paraffine wax 
by chilling and crystallizing, it should be noted that other special meth- 
ods must be resorted to, to isolate substances of a particular class from 
a particular petroleum. Petroleums contain varying proportions of 
the following classes of substances, all of which are very imperfectly 
known chemically: 

(1) Paraffine hydrocarbons, liquid and solid, series C^Ha^^j. 

(2) Saturated monocyclic or napththene hydrocarbons, empirical formula 

(3) Saturated polycyclic hydrocarbons, empirical formulae. 

CnHjjn— 2, CaSan— 4, CnHsn— a, CtC. 

" Monatshefte, 191S, 1153. 



24 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

(4) Benzenoid hydrocarbons and derivatives.. 

(5) Unsaturated liydrocarbons. (Present in distillates but probably not pres- 

ent in most crude petroleums.) 

(6) Asphaltic matter. 

(7) Sulfur derivatives. 

(8) Nitrogenous substances. 

(9) Organic acids ("naphthenic" acids, not of the fatty acid series). 

(10) Coloring matter and fluorescent substances (these substances may belong 
to other classes enumerated above). 

The majority of American petroleums yield gasolenes and kero- 
senes consisting chiefly of paraffine hydrocarbons. All American pe- 
troleums which contain large proportions of these lighter distillates, 
such as the light Appalachian, mid-Continent and northern Texas 
crudes, yield gasolene and kerosene of this character. Low boiling 
distillates consisting of cyclic hydrocarbons or naphthenes are usually 
derived from heavier crudes yielding very little of the lighter dis- 
tillates for example, the heavy California and the Jennings, Louis- 
iana crude from which Coates ^^ has isolated dicyclic hydrocarbons 
CioHis to C13H24 and the Russian and Galician oils from which cyclo- 
pentane, cyclohexane, and a series of their derivatives has been iso- 
lated.^^ The determination of the structure of these naphthenes, 
coupled with the difficulty of their isolation in a state of purity, is a 
task as difficult as any in organic chemistry, and it is doubtful if very 
much light will be thrown on their constitution until it is shown that 
chemical methods of utilization may lead to the extraction of greater 
profits, than are now obtained, though it is easily conceivable that the 
latter result cannot be arrived at without the former. 

Beilstein and Kurbatow^' showed that the more volatile hydro- 
carbons of Russian petroleum possessed the empirical formula CnHon, 
exhibited none of the reactions of olefines and in their general chemical 
behavior resembled the hydrocarbons of the methane series. Two hy- 
drocarbons of the formula C,;Hi2, one '« boiling at 72° and the other ^^ 
at 80° were isolated. Cyclohexane, prepared by Baeyer, proved iden- 
tical with the latter hydrocarbon from Russian petroleum and it was 
then shown that the isomeric hydrocarbon was methyl cyclopentane. 
Markownikow obtained evidence of the presence of cycloheptane in the 
fraction boiling at 115°-120° of a Caucasian oil. With the exception 
of the bicyclic decahydronaphthalene isolated by Ross and Leather *° 

"J. Am. Chem. Soe. S8, 384 (1906). 
"Ann. SOI, 164 (1898) ; SOS, 37 (1898) ; 
" Ber. IS, ISlSj 2028 (1880). S07, 842 (1899). 
"Kishner, J. Busa. Phys.-Ohem. Soc. 20, 118 (1890). 
"Markownikow, Ann. SOU, 1 (1898). 

''Analyst SI, 284 (1906) ; This hydrocarbon is now made commercially by the 
catalytic hydrogenation of naphthalene. 



THE PARAFFINED 25 

from Borneo petroleum the structure of the higher boiling naphthenes 
is largely a matter of conjecture. 

Physical PfloPERTiEa of Some Saturated Cyclic Hydrocaebons. 

Name Empirical Formula Boiling-Point°C Sp.Or. 

CyclopropaBe *^ CsHs — 35. ^ 

Cyclobutane" C.H, 11.-12. 0.7038^ 

Methyl cyclopropane " CaHsCHs 4.-5. ^ 

♦Cyclopentane" CHio 49. 0.7635^ 

Methyl cyclobutane " CiHj.CH, 39.-42 

1 . 1 dimethyl cyclopropane *" C8H4< ^^' 21. 

*Cyclohexane « CHia 81. 0.7934^^ 

♦Methyl cyclopentane" aH^CHj 70.-71 

10° 
Ethyl cyclobutane" CiHj.CsH, 72.2-72.5 0.7540^ 

18° 

1.2.3. trimethyl cyclopropane'* C3H3.(CH3)3 65.-67. 0.6946-^ 

1Q° 
1.1.2. " " ■» CsHs.CCHs)^ 57.-59. 0.6832^ 

0° 
Cycloheptane (suberane) " C,H« 118. 0.8275^ 

♦Methyl cyclohexane"" aHu.CH, 100. -101. 0.7662^ 

20° 

1.1 dimethyl cyclopentane "' GHs.CCHa)^ 88. 0.7547^ 

1.2 " " " aHs.CCHa). 92. - 93. 0.7581^ 
i-1.3 " " - aa.(CHa). 93. 0.7410|^ 
Cyclo-octane" CaH., M^Jt^ll5 °-S^°' ^ 

Ethyl cyclohexane ". " CeHuCiHs 132. -133. 0.7913^ 

1 . 1 dimethyl cyclohexane ™ C6Hio(CH3)2 120. 

1.2 dimethyl cyclohexane" CaHioCCHa)^ 124. 0.8002^3 

«Ladenburg & Krilgel, Ber. S2, 1821 (1899). 

"WlUstatter & Bruce, Ber. 1,0, 3979 (1907). 

"Demjanow, Ber. 28, 21 (1895). 

" Markownlkow, Ann. 327, 59 (1903). 

"PerMn & Colman, J. Ohem. Soc. 5S, 201 (1888). 

"Gustavson & Popper, J. pr. Chem. (2), 58, 458 (1898). 

"Perkin & Freer, J. Ohem. Soc. 5S, 203 (1895). 

"Zelinsky & Gutt, Ber. J,!, 2431 (1908). 

"Zelinsky & Zelikow, Ber. SI,, 2857 (1901). 

»» Willstatter & Kametaka, Ber. i}, 1480 (1908). 

" Sabatier & Senderens, Compt. rend. 132, 566 (1901). 

"2 Kishner, Ohem. Cent. 1908, II, 1860. 

MZelinsky & Eudsky, Ber. 29, 405 (1896). 

"Willstatter & Veraguth, Ber. 1,0, 968 (1907). 

»■ Kursanoff, Ber. 32, 2973 (1899). 

""Crossley & Renouf, J. Chem. Soc. 87. 1498 (1905). 

"Sabatier & Mailhe, Oompt. rend. 11,1, 20 (1905). 



26 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Physical PROPBRinis of Some Saturated Cycuc Hydeocabbons. 
Name Empirical Formula BoUing-Point °C Sp. Gr. 



1.3 dimethyl cyclohexane" 


tc 


118. 


0° 
0.7869 Qo 


1.4 " " " 


It 


119. 


0° 
0.7861^ 


1 methyl-3-ethyl oyclopentane "* 


^=^<aa 


120.5-121. 


0.7669^ 


1.1.2 trimethyl cyclopentane ^ 
Cyclononane * 


aH,(CH3)s 


113. -113.5 
170. -172. 


4° 
0.7847^5 
4 



Aromatic, or benzenoid, hydrocarbons have been found, usually in 
very subordinate proportions, in all petroleums which have been care- 
fully investigated. The per cent by volume of benzenoid hydrocarbons 
present, as reported, is often too high particularly when nitration meth- 
ods have been employed. This error is due to the relative ease with 
which non-benzenoid hydrocarbons are nitrated. Thus Edeleanu and 
Gane *^ report a yield of 41 % nitro products from gas oil from Penn- 
sylvania oil, a figure obviously far too high to accord with the em- 
pirical combustion analysis and well known behavior of this oil to 
consider this figure as an indication of the proportion of benzene de- 
rivatives present. However in the case of the lighter distillates the 
crystalline nitrated products can often be isolated and positively iden- 
tified. The presence of benzene has been shown in petroleums of va- 
rious origins and Mabery ^^ had no difTiculty in isolating naphthalene 
from a Cahfornia oil by fractional distillation, the fraction boiling 
at 220°-222° finally solidifying in the condenser. According to Jones 
and Wootton ^^ Borneo petroleum contains 6 to 7 per cent hydrocarbons 
of the naphthalene series. This oil contains mono and dimethyl deriva- 
tives of naphthalene. Brooks and Humphrey ■** found small quantities 
of benzene and toluene in gasolene made by distilling the heavy high 
boiling residue of Oklahoma oil at about 420°C. and under a pressure 
of about 100 pounds. Inasmuch as practically no hydrogen is present 
in the gases formed in the process they suggested that these small per- 
centages of benzene and its simpler homologues were formed as de- 

MZelinsky, Ber. 35, 2679 (1902). „c,Q«^ 

""Crossley & Renouf, J. Chem. 8oe. 89, 33 (189b). 

•"Zellnsky, Ber. 1,0, 3279 (1907). 

"> Bev. gen. Petrol. 1910, 393. 

"J. Soc. Chem. Ind. 19, 52 (1900). 

•w' ^m'^rfpm ^'oe^ts Sol^Vwie) ; The formation of benzene and toluene at 
much higheT temperatures As in the Hail or Eittman process, is an altogether dit- 
S?e5t matter In this latter process hydrogen Is always an important constituent in 
the evoTvedgAses ana it makes little difference what petroleum oil fraction Is employed, 
in fact fairly pure pentane or hexane or parafflne wax will yield substantial quantities 
of benzeno7l Sydro^carbon under these conditions Cf Egloff & Twomey, J. Phys. 
Chem. 20, 515 (1916) ; EglofE, Met. £ Chem. Eng. IS, 692 (1916). 



THE PABAFFINES 27 

composition products of high boiling benzene derivatives which were 
present in the original petroleum, rather than by the dehydrogenation 
of saturated cyclic hydrocarbons. 

Petroleums are normally free from olefinic hydrocarbons. Such hy- 
drocarbons are, however, invariably present in petroleum distillates. 
LeBel «^ found amylene and two isomeric hexenes in the light distillate 
from a petroleum from Pechelbronn, but regarded them as decompo- 
sition products formed during distillation of the crude oil. Balbiano 
and Paolini "^ detected olefines in an American kerosene (by the for- 
mation of a precipitate with mercuric acetate), and Mabery and 
Quayle ^'' reported hexenes, heptenes and octenes in a distillate from a 
Canadian petroleum. But in so far as the presence of olefines in crude 
petroleum is concerned, a clear demonstration of their presence is lack- 
ing, except in the case of a sample examined by Zaloziecki ^' and said 
to have come from Java. The occurrence of terpene like hydrocarbons 
has sometimes been reported but Coates has shown that the turpentine- 
like odor of the Jennings, Louisiana, oil is due to saturated bicyclic hy- 
drocarbons and that this petroleum contains no olefines. The pres- 
ence of olefines cannot be demonstrated or quantitatively measured by 
the usual iodine or bromine absorption methods owing to substitution 
reactions taking place. These methods invariably give too high re- 
sults in the case of pyrolytic distillates. 

The relative ease with which olefines are polymerized by fuller's 
earth and similar substances may explain the absence of these unsatu- 
rated hydrocarbons in petroleums. Until an authentic crude petroleum 
can by proper experimental methods be shown to contain them, the 
statement that olefinic hydrocarbons are not present in crude petro- 
leums seems amply justified. 

Very little is known regarding the sulfur compounds contained in 
crude petroleums and distillates. The refiner is concerned only with 
deodorizing the distillates and the chemical character of the sulfur 
derivatives is of no interest to him. The well known method of Frasch, 
consisting in the desulfurizing of oil by treatment with copper oxide, 
was developed particularly for oils from Canada and the Lima-In- 
diana field and Mabery and Quayle ^* have investigated the sulfur 
compounds of the Canadian oil and discovered what is apparently a 
new series of organic compounds of sulfur. By distilling the oil in 

"Compt. rend. 15, 267 (1872) ; 81, 967 (1875). 

"Ohem. Ztg. 1901, 932. 

"Naphtha, 1900, 222. 

"Am. Chem. J. 35, 404 (1906). 



28 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

vacuo and treating the distillates with alcoholic mercuric chloride they 
obtained precipitates of the sulfur compounds which were then decom- 
posed by hydrogen sulfide. In empirical composition these substances 
are identical with hydrothiophenes (which have not been made syn- 
thetically), and Mabery has designated them as thiophanes. They are 
oxidized by permanganate or chromic acid to sulfones, thick, viscous 
oils of slight, rather pleasant odors, and they combine with ethyl iodide 
to form products of the empirical composition CnHgnS-CaHgl, the iodine 
being replaceable by hydroxyl, by means of silver oxide, to give basic 
substances. The thiophanes are comparatively stable. Mexican pe- 
troleums contain as much as 7.5% sulfur but no differentiation between 
dissolved or suspended free sulfur and combined sulfur has been made. 
Mexican and many of the Gulf coast oils contain free sulfur *" and 
on distillation hydrogen sulfide is evolved. Organic bases such as 
aniline, pyridine and quinoline, and also ammonia react with many, 
perhaps all, of the sulfur compounds contained in petroleums, pyri- 
dine being said to "catalyse" the evolution of hydrogen sulfide. The 
desulfurizing of petroleum by heating in the presence of free ammonia, 
hydrogen sulfide being formed, has been proposed by F. M. Perkin." 
By retorting certain shales, distillates rich in sulfur are obtained 
which may be sulfonated by concentrated sulfuric acid and the product, 
in the form of water soluble ammonium salts, is the material known 
in pharmacy and medicine as "ichthyol," so named because the shales 
in Austria from which the ichthyol oil was first derived are rich in 
fossil fish remains. The product is a complex mixture of substances, 
of variable composition and practically nothing is known as to the 
chemical nature or structure of the sulfur derivatives in the original 
distillate. Other shales yield similar distillates, for example: 

Per cent 

Oil from shale at, C. H. N. O. S. 

St. Champ, France " 77.3 9.2 0.37 1 .14 11 .99 

Tuscany 69.5 8.7 2.27 11.6 7.79 

In preparing ichthyol, the crude distillate is sulfonated by treating 
with ordinary concentrated sulfuric acid, slightly diluted with water or 
brine and the unsulfonated oil extracted by petroleum ether and the 
sulfonic acids, neutralized by ammonia. The commercial product al- 
ways contains ammonium sulfate on account of the practical impos- 
sibility of completely removing the excess sulfuric acid.''^ The crude 

•» Richardson, J. Soc. Cliem. Ind. 21, 316 (1902). 
^"Chem. Trade J. 50, 251 (1917). 

" Demesse & Eeaubourg, Bui. Soc. cMm. IS, 625 (1914). 
"Puckner, 1Mb, Rep. Am. Med. Assn. 5, 110. 



THE PARAFFINES 29 

oil contains, in addition, to sulfur compounds, phenols and organic 
acids/^ 

The occurrence of nitrogen bases in petroleum is by no means rare 
and the percentage of such bases in many crude petroleums is relatively 
large. Ordinarily the proportion of nitrogen in petroleum does not 
exceed 1.5 per cent but an Algerian oil is reported as having 2.17 per 
cent and a Japanese 2.25 per cent. The highest per cent of nitrogen 
thus far reported is 2.39 per cent, found, in a Calif ornian oil. This 
means that probably 20 per cent of this oil consists of nitrogen bases. 
Very little is known as to the character of these bases. The separation 
of definite substances by fractional distillation of the bases recovered 
from the acid washings of the oil has not been successful. They form 
precipitates from acid solutions with platinum, palladium, mercuric, 
cadmium and ferric chlorides, potassium dichromate, ferro and ferri- 
cyanides and picric and oxalic acids. By oxidation with alkaline per- 
manganate in alkaline solution the nitrogen is evolved partly as free 
nitrogen and partly as ammonia. Oxidation by chromic acid has led 
to no definite results. Decomposition by the method of exhaustive 
methylation does not appear to have been given a fair trial; ethyl 
iodide combines with these bases when heated together in a sealed tube. 
The bases are weakly basic. In 1900 Mabery ^* concluded that the 
nitrogen bases in California petroleum consisted of a mixture of more 
or less hydrogenated quinolines. Recently Mabery has returned to the 
problem and in a recent paper, with L. G. Wesson,'^ has shown that by 
careful oxidation with potassium permanganate, the various fractions, 
derived from the crude mixture of bases yield pyridine pentacarboxylic 
acid and methyl pyridine tetracarboxylic acid. No higher fatty acids 
were observed among the oxidation products. By oxidizing with 
chromic acid and subjecting the calcium salts of the acids thus 
formed to dry distillation, p-methylquinoline is produced. Mabery 
and Wesson conclude that the organic bases of California petroleum 
consist mainly of an indefinite mixture of alkylated quinolines or iso- 
quinolenes, the rings containing the nitrogen being completely alkyl- 
ated by small alkyl groups. 

Origin of Petroleum. 

The great preponderance of opinion among geologists and chemists 
is in favor of the theories of the origin of petroleum from organic rather 

"Schelbler, Ber. iS, 1815 (1915). 
"J. Boc. Chem. Ind. 19, 505 (1900). 
"J. Am. Ohem. Soc. i», 1014 (1920). 



30 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

than inorganic sources. [In view of this fact a discussion of the theories 
of inorganic origin will be omitted here but good reviews of this phase 
of the subject are available in many standard worksJ^] A great deal 
has been written on this theme but experimental evidence is almost al- 
together lacking. The chief evidence is of an altogether different na- 
ture, namely geological and geochemical on the one hand and the gen- 
eral chemical character of petroleums on the other. The question is 
one that hardly lends itself to direct experimental study. 

Both animal and vegetable matter have probably contributed to the 
formation of petroleums and natural gases and decay of such organic 
matter appears to be easily adequate to the formation of the quantities 
of oil and gas which are found buried in the strata. Geologists " have 
called attention to the fact that petroleum is very widely dissemi- 
nated through many limestone and sandstone strata of enormous thick- 
ness and area. Thus it has been estimated that in the limestone of 
Chicago, which has a thickness of about 35 feet, there are over 7,000,- 
000 barrels of oil in each square mile of this stratum. 

The deposits of petroleum at Baku and the surrounding territory 
are, nearly all, in Tertiary formations, and the menilite shale in which 
the petroleum occurs is certainly of marine origin. It has been esti- 
mated that if the annual deposition of fish remains in these rocks were 
equivalent to the annual catch in the fisheries of northern Europe, and 
that only 50 per cent of the oil in these remains were converted into 
petroleum, a period of about 2500 years would suffice for the entire 
petroleum accumulations in the Carpathian area. Engler has pointed 
out that both animal and vegetable remains may have contributed to 
the formation of petroleum and Kraemer and Spilker '^ have pointed 
out that certain algae contain droplets of oil in their cells. 

Petroleums may be very much altered by filtration through fine 
sand or other fine material as has been shown experimentally by the 
work of Day, Gilpin and Kramm and others, the more fluid and vola- 
tile hydrocarbons being gradually separated from the more complex 
and less volatile constituents. This undoubtedly accounts for the char- 
acter of certain crude petroleums which are very slightly colored and 
sometimes contain upwards of 30% of gasolene. In the accumulation 
of such oils in pools, the oil must in many cases have traveled long 
distances through the porous rock. 

'• Data of Geo-Chemiatry by F. W. Clark, Bulletin 695, U. S. Geological Survey, 

" Orton, Ohio Geological Survey, First Annual Report 1870, and Hunt : Chemical 
and Geological Essays 1875, p. 168. 
"Ber. 35. 1212 (1901). 



THE PARAFFINES 31 

Practically all petroleums which have been investigated give dis- 
tillates which show slight optical activity. Inasmuch as no synthetic 
process, such as the formation of hydrocarbons from carbides and the 
like, yields optically active material, the presence of optically active 
substances in petroleum is considered to be one of the strongest argu- 
ments in support of the organic origin of petroleum. Although pure 
fatty glycerides are not optically active, natural fats and oils contain 
small quantities of cholesterol, phytosterol, protein decomposition prod- 
ucts and the like which are optically active. When oils containing 
cholesterol or phytosterol are subjected to distillation under pressure 
the maximum optical activity is observed in the same fractions, with 
respect to boiling point, as is the case with petroleum distillates. '° 

It is not too much to expect that further study will reveal the 
chemical history of the formation of petroleum as clearly as the for- 
mation of coal is revealed in the series of changes through peat, the 
lignites, bituminous coals and anthracite. This information will un- 
doubtedly be obtained through a study of superficial or recently buried 
deposits rather than by experimental work seeking to produce the re- 
sults by laboratory methods. Phillips observed the anaerobic fermen- 
tation of sea weeds in an apparatus which was observed over a period 
of two and a half years. At first a little methane together with larger 
quantities of carbon dioxide, hydrogen and nitrogen were evolved but 
toward the end of the experiment the evolved gas consisted chiefly of 
methane. 

In addition to the geological evidence of the organic origin of pe- 
troleum, a wealth of evidence is found in the chemical character of pe- 
troleums themselves, particularly the optically active constituents, 
naphthenic acids, nitrogen and sulfur derivatives. 

A great deal of the experimental investigations which have given 
support to the organic theory have been carried out by Engler and 
his students.'" Engler believes that in the anaerobic decay of marine 
animal remains the fatty oils, being more resistant to putrefactive 
changes, remain entangled in the marine sediments long after the pro- 
teins and other organic constituents have been lost by putrefactive de- 
cay. He has shown that when fish oil is heated or distilled under pres- 
sure, good yields of a liquid hydrocarbon mixture are obtained, which 

" Walden, Chem. Ztg. SO, 391, 1155, 1168 (1906) ; Rakuzin, 8th Int. Oonff. Appl. 
Chem 185, 721 ; Ber. n, 1211, 1640, 4675 (1908) ; Marcosson, Ohem. Ztg. SB, 377, 391 
(1908) : bbbelohde, Ber. i2, 3242 (1909) ; iS, 608 (1910). 

"Ber 21 1816 (1888) ; 86, 1449 (1893) ; SO, 2365 (1897) ; Z. f. angew. Chem. 
ms, 1585 ; Ber. 1,2, 4610, 4613, 4620 (1909) ; ^S, 388, 954 (1910) ; Z. f. angew. Ohem. 
1912, 4. 



32 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

very greatly resembles crude petroleum in its physical characteristics 
and chemical composition. Such distillates have a marked green fluor- 
escence and in the lighter fractions, obtained by fractional distillation, 
n . pentane, n . hexane, n . heptane, n . octane, and nonane were identified. 
By chilling the fraction boiling above 300° crystalline parafEne, melt- 
ing-point 49° to 51°, was obtained and also a viscous fraction closely 
resembling lubricating oil was isolated. These distillates obtained by 
Engler contained notable percentages of unsaturated hydrocarbons, 
thus differing from crude petroleum but this difference is readily un- 
derstood, in view of the experimental demonstration of Gurwitsch ^^ 
that fuller's earth rapidly polymerizes unsaturated hydrocarbons. Thus 
at ordinary temperatures amylene is 85% polymerized in two days. 
Engler's distillates contain small quantities of aromatic hydrocarbons, 
benzene, toluene and xylene being identified by their nitro compounds, 
these distillates resembling crude petroleums in this respect. Very 
similar results were obtained by distilling animal and vegetable oils 
and fats under pressure. 

Although the strata in which petroleum oils occur are never found 
at sufficient depth to be subjected to the temperatures employed by 
Engler and in most cases have not been subjected to volcanic intrusions, 
marked folding of the strata or other sources of heat, Engler, neverthe- 
less, supposes that these same destructive changes which he effects by 
pressure distillation may be effected in Nature at very much lower 
temperatures during the long course of geologic time. Though little 
is definitely known in regard to the substances in petroleum which con- 
tain oxygen and sulfur, the mere presence of these substances is indi- 
cative of an organic rather than an inorganic origin. Mabery has 
shown that the nitrogenous constituents of California petroleum are 
hydrogenated quinolines.'^ 

Asphaltic matter is undoubtedly formed by oxidation, which process 
readily explains such deposits as that of Trinidad Island and such a 
process is closely duplicated in the well-known process of Byerley and 
Mabery of blowing air through the heavy residuum left in the stills 
after the more volatile fractions have been distilled from crude pe- 
troleums. 

As regards sulfur compounds these have been ascribed to the de- 
composition of organic remains and it is noteworthy that certain oils 
rich in sulfur are associated with shales containing abundant fossil re- 

«■ J. Russ. Phye.-Chem. Boo. it, 827 (1915) ; J. Chem. 8oe. 19X5, I, 933. 
"J. Am. ahem. Soc. 42, 1014 (1920). 



THE PARAFFINE8 33 

mains of fish. This is particularly true of the Austrian deposit from 
which the well-known pharmaceutically valuable "ichthyol" is de- 
rived. These sulfur compounds, however, may have been formed in a 
very different manner. It is well known, for example, that sulfates 
can be reduced by organic matter or by anaerobic fermentation with 
the formation of sulfur. Sulfur in very large masses is often found 
associated with petroleum in the American Gulf Coast region and its 
formation is perhaps best accounted for in this manner. It is also well 
known that free sulfur reacts with hydrocarbons with relative ease. 
The direct addition of sulfur to unsaturated hydrocarbons has been 
shown by Erdmann. Reaction with saturated hydrocarbons, parafiine 
for example, can be effected at very moderate temperatures. In the 
latter case, hydrogen sulfide is evolved, and this gas accompanies the 
Gulf Coast petroleums sometimes in very large quantities. 

The Formation of the Paraffines. 

Decomposition of a wide variety of organic substances by heat 
yields paraifine hydrocarbons among the products so formed. Methane 
is an important constituent of retort coal gas (30 to 40% ) , by-product 
coke oven gas, oil gas and the like. The per cent of methane contained 
in such gases depends upon many factors, for example temperature, 
the duration of the heating and the presence or absence of substances 
capable of affecting the equilibria in such gas systems.*^ Thus in the 
coking of coal the gas is richest in methane when the retort tempera- 
ture is within the range 600° to 800° but as the retort temperature in- 
creases above 800° the per cent of methane in the evolved gas rapidly 
diminishes and the per cent of hydrogen rapidly increases.^* Gases 
containing ethylene, such as oil gas and coal gas, are invariably not in 
equilibrium at the temperatures at which they are produced and in 
practice they are removed and cooled before equilibrium at the higher 
temperature is established. Ethylene is rapidly decomposed, above 600° 
to methane and carbon and this reaction may be greatly catalysed by 
contact with iron oxide or other catalysts. Fats or fatty acids readily 
break down on heating under pressure to a series of hydrocarbons, 
mainly saturated, which closely resemble crude petroleum and Eng- 
ler,^^ has used this fact in developing his theory of the origin of pe- 
troleums. It has been shown that in the heat decomposition of heavy, 
high boiling mineral oils under pressure, the lighter oils so produced 

«» Slator, J. Chem. Boc. 109, 160 (1916). 

" Vignon, J. Gas Lighting mi, 107 ; Meyer, Chem. ATig. S, 2795 (1914). 

"Petroleum 7, 399 (1912). 



34 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

consist largely of hydrocarbons of the parafSne series, which may be 
accounted for by the supposition that when a large paraffine molecule 
breaks up into two simpler molecules, one will be a saturated paraffine 
and the other an olefine, 



R CH2CH2 



CH^ R > R CH3 + CH2 = CH.R «« 



The destructive distillation of bituminous shales, lignites and peat 
yields distillates containing paraffine hydrocarbons; and paraffine wax 
has for many years been manufactured from the distillates of shale 
in Scotland. By the distillation of ordinary bituminous coking coal at 
low temperatures a distillate rich in paraffine wax is obtained. These 
solid paraffines like those from petroleum are normal hydrocarbons of 
24 to 29 carbon atoms.*' 

Effects of Heat on Non-Benzenoid Hydrocarbons. 

The changes brought about by heating non-benzenoid hydrocarbons 
have long been of industrial interest and importance, particularly in 
the manufacture of oil gas, carburetted water gas, the pyrolysis of pe- 
troleum oils for the manufacture of kerosene and more recently gaso- 
lene or motor fuel from heavier hydrocarbons. These processes are 
problems of technology or engineering, rather than chemistry, but more 
recently a desire to know more concerning the chemical reactions in- 
volved and their relationships has been indicated by the character of 
many of the published researches. 

The two fundamental reactions which take place when hydrocar- 
bons are heated to the decomposition point are, first, the rupture of 
the carbon-to-carbon structure and second, the dissociation of hydrogen 
from carbon. These two reactions probably occur simultaneously at- 
tended by a sequence of other reactions, but special catalysts may 
greatly accelerate one or the other type of reaction, for example, nickel, 
palladium or platinum may cause dissociation of hydrogen without 
alteration of the carbon structure, as in the conversion of cyclohexane 
to benzene in the presence of nickel at 250°, or the complete rearrange- 
ment and splitting of hydrocarbons by gentle heating in the presence 
of anhydrous aluminum chloride, in which case methane but not hy- 
drogen is evolved. 

The earlier technical investigations of the pyrolysis of hydrocar- 

«01eflnes of this type are unstable and rearrange, ct. pp. (150, 151). 
nQlund, Ber. 12, 1039 (1919). 



THE PARAFFINES 35 

bons centered upon coal tar, benzene, naphthalene and their deriva- 
tives. In 1866-7, Berthelot published a series of important researches,^' 
and stated that at a "dull red heat" equilibrium was established be- 
tween ethylene, hydrogen and ethane. He discovered a series of con- 
densations of acetylene; that in the presence of coke, acetylene, at 
the "temperature at which glass softens" is decomposed almost wholly 
to hydrogen and carbon; acetylene and ethylene yield a condensation 
product isomeric, or identical with crotonylene, and acetylene and ben- 
zene gave naphthalene. Benzene passed through a porcelain tube gave 
diphenyl, chrysene and a resinous substance, but no anthracene or 
naphthalene. Toluene gave benzene, unchanged toluene, and large pro- 
portions of naphthalene. Xylene gave toluene as the principal product. 
Berthelot's view that acetylene was the parent substance of the ben- 
zenoid hydrocarbons was vigorously disputed by Thorpe and Young,'" 
Armstrong and Miller "^ and Haber ^^ who considered that hydrogen or 
methane were first formed, the residues then condensing or undergoing 
still further decomposition: 

2 CeH, > C,,H,„ (diphenyl) -hH, 

CeHi^ (hexane) ^CgHioCamylene) + CH^ 

They pointed out that usually acetylene cannot be detected among 
the products of pyrolysis. Bone and Coward "^ have made a careful 
study of the thermal decomposition of methane, ethane, ethylene and 
acetylene and concluded that Berthelot's theory of the attainment of 
equilibrium between dissociation and recombination of these hydro- 
carbons is not borne out by the experimental evidence. Their results 
show: 

(1) Methane is exceedingly stable. It decomposes almost exclusively 
into hydrogen and carbon and this decomposition, though rever- 
sible, is mainly a surface phenomenon, at least at moderate tem- 
peratures. 

(2) Acetylene polymerizes at comparatively low temperatures, the 
optimum temperature range for this polymerization being 600°- 
700°. Acetylene being formed from ethylene, condensation prod- 
ucts of acetylene will be found among the products whenever 
ethylene is a primary product of the pyrolysis of hydrocarbons. 

" Compt. rend. 62, 905, 947 (1866) ; 63, 788, 834 (1866) ; Bull. Soc. Ghim. (2) 7, 
217 (1867). 

"Proc. Roy. Soc. B, 370; 20, 488; tl, 184 (1873). 
">Ohem. News i9, 285; Soc. 1,9, 74 (1886). 

"J. Gasbel, S9, 377, 395, 435, 452, 799; Ber. 29, 2691 (1896). 
"Soc. 9S, 1197 (1908). 



36 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

(3) Ethylene and acetylene combine with hydrogen at moderate tem- 
peratures to form ethane. Whitaker and Leslie ^^ obtained evi- 
dence of hydrogenation at 620° when hydrogen was introduced 
with oil in an experimental apparatus for making oil gas. These 
authors also call attention to the fact that in decomposing oil to 
gaseous products, equilibrium, or rather the ultimate composition 
which a given temperature tends to produce, is seldom attained, 
even in apparatus of industrial size, owing to the short period 
of time, during which the hydrocarbons are subjected to the par- 
ticular temperature of the operation. One reason for this un- 
doubtedly lies in the fact that some of the reactions taking place 
in such systems are strongly endothermic, for example, 

C^He > C3H4 + Ha = 31,270 calories 

and such reactions can be maintained only by the absorption of 
a large supply of energy .°* 

It is well known that the velocities of chemical changes are greatly 
affected by relatively small changes in temperature. It is, therefore, 
readily understood that small differences of operating temperature may 
cause very great differences in the character of the pyrolytic products, 
a fact apparently first appreciated in industrial operations by Hall. 

Generally speaking, the temperatures employed for obtaining mo- 
tor fuel are within the range 410°-500° and Rittman, Button & Dean "^ 
consider that the maximum yield of aromatic hydrocarbons (from pe- 
troleum oils) is obtained within the range 650°-700°. Ipatiev ^^ states 
that at 600°-700° hexane and cyclohexane yield olefines and other hy- 
drocarbons, but no benzenoid hydrocarbons. Methyl cyclopentane was 
found among the products. Norton and Andrews *" found that at 550° 
hexane was not decomposed and was very slightly affected at 600° 
but at 700° decomposition with formation of gas, methane and ethyl- 
ene, propylene, butylene, amylene, hexylene and butadiene but no 
benzene. Iso-hexane and n . pentane show approximately the same sta- 
bility and at 700° yield gas and a series of olefines. Benzene appears 
among the products of reaction only at higher temperatures. Thus 
Haber obtained benzene from hexane by heating to 800° "^ and Wor- 
stall and Burwell obtained it from heptane and octane at 900°."° 

"J. Ind. d Eng. Chem. 8, 593, 684 (1916). 

"Lomax, Dunstan & Thole, J. Inst. Petr. Teclin. 3, 76 (1916). 

«»TJ. S. Bur. Mines Bull. 114, Washington (1916). 

"Ber. u, 1984, 2978 (1911). 

'^Am. Chem. J. 8, 1 (1886). 

" Loc. cit. 

"Am. Chem. J. 19, 815 (1897). 



THE PARAFFINES 37 

Benzene and its simple homologues had been found in the liquid 
condensate obtained by compressing oil gas.^"" Armstrong and Miller 
made a careful study of this liquid condensate from oil gas and iden- 
tified propylene, amylene, hexylene, heptylene, crotonylene, isoal- 
lylethylene, benzene, toluene, xylenes, mesitylene, pseudo-cumene and 
naphthalene. In 1878, a number of processes were described "^ which 
sought to manufacture benzene hydrocarbons from Russian petroleum 
by passing the oil through red-hot tubes packed with various materials 
(the function of which was not evident) . None of these processes were 
industrially successful. Nikiforoffs' process was apparently a develop- 
ment from the well known Pintsch gas process, the oil being first de- 
composed or vaporized at 525°-650° and then passed through retorts, 
similar to the older type of Pintsch gas retort, at 700°-1200° under a 
pressure of about two atmospheres. No further important work on 
the manufacture of benzene hydrocarbons from petroleum oils by the 
action of heat, in the absence of catalysts, was made until the recent 
war period when Hall, working in England, and Rittman and his co- 
workers in the United States, developed processes, which were operated 
industrially. Hall decomposes oil at 550°-600° and under a pressure 
of about 70 pounds per square inch when motor fuel is the desired prod- 
uct and for benzene and toluene the operating temperature is 750° and 
the pressures 100 to 110 pounds per square inch.^"^ A noteworthy me- 
chanical feature of the Hall process is very rapid passage of the oil 
and vapors through the heated tubes, which minimizes the deposition 
of carbon. Rittman employed a temperature of 700° and a pressure of 
150 pounds per square inch. In connection with this work, which 
probably should be regarded as a war time industry, at least so far as 
the manufacture of benzene and toluene from petroleum is concerned, 
much valuable experimental work was done. Commercial gas oil, 
specific gravity 0.817 at 15.5° and boiling at 200°-350°, in the Rittman 
apparatus gave a maximum yield of toluene, 3.1 per cent by volume, 
at 650°. The maximum yield of benzene, 4.4 per cent by volume was 
obtained at 800°. The maximum yield of xylene was 1.9 per cent at 
750°."' 

Other conditions being equal, higher yields of aromatic hydro- 
carbons are obtained from petroleum containing relatively large pro- 

iM Armstrong and Miller, J. Chem. Soc, Ji9, 74 (1886) ; Williams, Ohem. News i9, 
197 (1884). 

lo'Letny, Ber. 11, 1210 (1878) ; Liebermann & Burg, Ber. 11, 723 (1878) ; Salzmann 
& Wichelhaus, Ber. 11, 1431 (1878). 

'»' TT. S. Pat. 1,175,909 ; Brit. Pat. 24,491 (1913) ; 437 (1914) ; 2948 (1914) ; 
7282 (1914) ; 12,962 (1914) ; 1594 (1915) ; D. S. Pat. 1,194,289; 1,175,910. 

iMEgloff, Met. <& Chem. Bng. 16, 492 (1917). 



38 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

portions of benzene and naphthalene derivatives and cyclohexane de- 
rivatives, such as Borneo petroleum. The oil from the deeper strata 
of the Kotei field in Borneo was used in England during the war for 
the manufacture of benzene and toluene. Jones and Wooton first 
called attention to the unusual character of this oil and more recently 
Chavanne and Simon ^"* have examined the gasoline fraction of this 
oil and state that they have identified cyclopentane, methylcyclopen- 
tane, cyclohexane, a dimethylcyclopentane, methylcyclohexane and 
dimethylcyclohexane. During the war gasoline from this petroleum 
was sent to England where benzene and toluene were made from it in 
a fair degree of purity. This gasoline contained about 40 per cent of 
aromatic hydrocarbons of which about 7 per cent was benzene, 14 per 
cent toluene, 15 per cent xylenes and 4 per cent higher homologues.^"' 
Brooks and Humphrey ^"^ found small quantities of benzene and tolu- 
ene in gasoline made by distilling heavy Oklahoma oil at the relatively 
low temperature of 420° and a pressure of 100 pounds per square inch. 
Small yields of aromatic hydrocarbons were also obtained from heavy 
high-boiling petroleums by heating with anhydrous aluminum chloride 
and since the temperature employed in the first method is considerably 
below that at which benzene has been observed to be formed from 
paraffines or naphthenes, they conclude that high boiling benzene de- 
rivatives are present in the original oil, benzene being obtained by their 
splitting or "cracking." 

It was apparent from much of the early work on pyrolysis that the 
character of the products obtained was not solely a function of the tem- 
perature employed but also of the time or duration of the heating and 
also the presence or absence of various substances acting catalytically 
upon the decomposition, either hydrogen dissociation or splitting of 
the carbon structure, or affecting one or more of the secondary re- 
actions, for example polymerization of the olefines which are formed. 
Before discussing the effect of catlysts the results of pyrolysis at mod- 
erate temperatures will be noted. 

One of the most conspicuous differences in the results of low tem- 
perature decomposition is the greatly decreased yield of gas. Exact 
comparisons are difficult to make on account of variable time factors, 
different distribution and character of the heated surfaces and the like. 
Hall states that in the industrial tube type of apparatus developed by 
him a change of operating temperature from 540° to 580° results in an 

1" Compt. rend. 1919, 285. 
>i»Kewley, Chem. Tr. J. 1921, 380. 
"«J. Am. Chem. Boc. S8, 393 (1916). 



THE PARAFFINES 39 

increase of 50 per cent in the quantity of gas obtained. In a small ex- 
perimental pressure still Brooks, Padgett and Humphrey ^'" found, 
when distilling 85 per cent of the oil used [heavy Oklahoma gas oil] , 
under pressure, that at 50 pounds pressure and a mean temperature of 
410°, 24.8 liters of gas were formed per liter of distillate; at 150 
pounds pressure and a mean temperature of 425°, 58 liters of gas per 
liter of distillate were produced. The relative area of heated surface 
(iron) in this small apparatus was quite large, as compared with oil 
distilling apparatus of industrial dimensions of the Burton type, but 
the results are indicative of the large difference in gas yield resulting 
from a comparatively slight temperature change. The effect of in- 
creased pressure should, per se, decrease the gas yield by polymerizing 
the olefines. That higher temperatures give large proportions of de- 
fines in the gas is indicated by the following table: 

Composition of Oil Gas Made in Tubes Maintained at Definite 
Temperatures .™ 

Temperature, deg. C 600. 650. 700. 730. 

Pressure, lb 57. 72. 83. 95. 

Ethylene, per cent 19.3 19.0 17.7 17.5 

Propylene, per cent 28.0 28.4 23.9 20.0 

Higher olefines, per cent 3.2 4.2 3.5 3.1 

Total olefines, per cent 50.5 51.6 45.1 40.6 

Gases from Cracking Distillations under 100-Lb. Pressure. 
From Jennings Crude 

12 3 

340° 415° 422° 

Temperature in still Per Cent Per Cent Per Cent 

CO2 12 0.5 0.0 

CO 1.2 0.5 1.3 

Illuminants 15.4 15.3 13.0 

Hydrogen 0.0 4.0 4.4 

Saturated Hydrocarbons 81.5 79.7 81.3 

From Paraffine 

417° 432° 437° 

Temperature in still Per Cent Per Cent Per Cent 

CO2 0.0 0.0 0.0 

CO 0.0 0.0 0.0 

Illuminants 25.4 37.0 33.5 

Hydrogen 0.3 0.9 3.0 

Saturated Hydrocarbons 74.3 62.1 63.5 

Analyses of oil gas are usually reported in terms of total olefines, 
or illuminants, hydrogen and methane. Accurate analyses, with respect 
to methane, ethane, propane and other hydrocarbons, made by the 
method of fractional distillation at low temperatures have not been re- 

""J. Franhl. Inat. ISO, 653 (1915). 

"^ Hall type of apparatus, industrial size. 



40 CHEMISTRY OF THE NON-BENZENOW HYDROCARBONS 



CM. 


CH. 


Total 


Per 


Per 


defines 


Cent 


Cent 


Per Cent 


18.6 


16.3 


36.3 


19.0 


18.3 


38.9 


22.4 


12.5 


37.3 


22.6 


13.7 


38.5 


25.7 


12.0 


41.5 



ported. The relative proportions of ethylene, propylene and other 
olefines in oil gas made at different temperatures in a commercial size 
Pintsch gas apparatus is given in the following table: 

Per Cent Ethylene and Pkoptlbne in Oil Gas. 
Higher 
Temp. Olefines 

Deg. C Per Cent 

805-650 1.4 

660-535 1.6 

635-535 2.4 

625-535 2.6 

615-425 3.8 

The composition with respect to olefines of gas made at definite 
temperatures in a large industrial size apparatus of the Hall type is 
as follows: ^"^ 

Per Cent Oil Gasified in Hall Type Apparatus at Different Temperatures. 

Per Cent 

Temperature Per Cent Ethylene and 

Deg. C Gas Propylene 

605 17.7 47.9 

625 ; 26.6 46.1 

645 37.6 44.9 

665 , 40.0 43.7 

685 40.8(?) 42.6 

705 48.7 39.5 

725 66.6 38.5 

Typical analyses of commercial gases are of interest particularly 
as regards the relative proportions of methane, ethane, hydrogen and 
illuminants.^" 



Average Composition of Commercial Gases. 
Ilium. CO H2 CH4 GiHe CO2 0. 
% % % % % % % 



N, Cdl. 

% Pr.B.T.U. 



Coal gas 4.0 8.5 49.8 29.5 3.2 

Carburetted water gas ... 13.3 30.4 37.7 10.0 3.2 

Pintsch gas 30.0 .1 13.2 45.0 9.0 

Blau gas 51.9 .1 2.7 44.1 .0 

All oU water gas 7.0 9.2 39.8 34.6 .. 

Oil gas 31.3 2.4 13.5 46.5 3.0 

Blue water gas 40.9 50.8 .2 .0 

Producer gas (coal) 2 17.6 10.4 6.3 .0 

Producer gas (coke) 25.3 13.2 .4 .0 

Blast furnace gas 26.5 3.5 .2 . . 

Wood gas (pine) 10.6 27.1 32.7 21.5 .. 



Oil gas, Dayton process' 



14.7 5.6 1.7 



7.8 



1.6 

3.0 

.2 

.0 

2.6 

.3 

3.4 

7.3 

5.4 

12.8 

4.9 

6.1 



3.2 

2.1 

1.6 

1.2 

6.6 

1.1 

3.5 

58.1 

55.2 

56.9 

2.6 

63.2 



16.1 
22.1 
43.0 
48.2 
19.7 
38.0 



622 

643 

1276 

1704 

680 

1320 

299 

161 

137 

100 

607 

( 500 

I 300 



>»• Brooke, Cliem. & Met. Eng. i2, April 7, 1920. 

"» Rogers Industrial Chemistry Ed. 2. Fulweiler, p. 474. 

"iBlnnall, Gas Age Jft, 47 (1921). This process depends 
bustlon of the oil sufficient to raise sufficient heat to gasify 
4 gallons of oil axe required to make 1000 cubic feet of gas 
per cent of nitrogen is naturally high. 



upon the partial com- 
the remainder. About 
of 450 B. T. U. The 



THE PARAFFINES 41 

Although data obtained in making oil gas on a small experimental 
scale have no close industrial parallel, the experimental results of 
Whitaker and Rittman ^^^ are of interest as indicating the very marked 
effect of variations of temperature and pressure. 

Oil Gas Experiments of Whitakek & Rittman.* 





Pressure 
















Temp. 


lb. per 


Gas 


Carbon 


Tar 


CH. 


CH, 


a 


Ilium. 


°C 


sq. in. 


Liters 


Grams 


CO. 


Liters 


Liters 


Liters 


Liters 


650° 


15. 


135 


3 


163 


45.5 


13.8 


12.1 


58.8 


650° 


45. 


145 


8 


133 


65.2 


16.7 


13.1 


44.3 


750° 


0.75 


146 


1 


153 







18.3 


82.0 


750° 


15. 


206 


18 


80 


84.5 


10.15 


39.6 


63.0 


750° 


45. 


194 


26 


87 


110.0 


11.8 


33.9 


30.1 


900° 


0.75 


235 


12 


58 


63.4 


trace 


48.8 


110.0 


900° 


15.0 


382 


115 


11 


178.1 


trace 


148.2 


50.0 


900° 


45.0 
Oil used. 


310 


165 


9 


128.9 


none 


155,0 


15.5 


*40co 





In a later paper Whitaker and Alexander ^^^ showed that under the 
same experimental conditions the composition of the gas produced 
varies with the rate of oil feed, within rather wide limits, and that even 
at comparatively slow rates of oil feed equilibrium is not reached. 
Thus it has been shown that at 1200° hydrogen is in equilibrium with 
carbon and about 0.3 per cent methane, but Whitaker and Alexander 
find 6 to 10 per cent methane in their most slowly conducted experi- 
ments "^ and they emphasize the fact that equilibrium compositions 
are not obtained in gas making practice and that it would be im- 
practical to run an oil gas generator at such rates of oil feed as would 
even approximate equilibrium conditions. 

Zanetti ^^' obtained typical oil gas by decomposing the propane 
fraction of natural gas gasoline at 750° , obtaining ethylene, propylene, 
butylene and small quantities of liquid hydrocarbons and tars. 

In view of the fact that the coking of coal at low temperatures 
yields a distillate containing paraffine wax, naphthenes and defines 
and resembling crude shale oil in its general character the coking of 
coal at higher temperatiu-es with the formation of coal gas and typical 
coal tars should be regarded as essentially paralleling the high tem- 
perature pyrolysis of mineral oils, in contact with coke or carbon. 

'"J. Ind. d Bug. Cliem. 6, 479 (1914). 

"'J. Ind. & Bng. Ghem. 7, 484 (1915). 

"•The commercial manufacture of hydrogen by heating methane or other hydro-' 
carbons to 1200°-1300° has been proposed, with various modifications, for example see 
UhliDger, U. S. Pat. 1,363,488. 

'"J. Ind. <6 Bng. Oliem. 8. 674 (1916). 



42 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

As regards the liquid products of pyrolysis of high boiling hydro- 
carbons at moderate temperatures, low temperature, pressure and slow 
operation favor the formation of saturated low boiling hydrocarbons. 
Hall and others have called attention to the relatively large yields of 
olefines and diolefines obtained at 550°-600°. Such distillates are said 
to be "highly cracked," absorb oxygen readily, a very general property 
of diolefines (see pages 212, 216) forming a resinous oxidation product 
which is often noticed as a sticky film when such oil is permitted to 
evaporate. Such distillates, containing diolefines, react energetically 
with sulphuric acid forming tars. Slow distillation under pressure 
evidently polymerizes the olefines since hydrogenation of hydrocarbons 
at 400°-450° in the absence of catalysts and under moderate pressures 
has not been observed. Although Bergius has hydrogenated fatty oils 
in the absence of finely divided metallic catalysts by heating with hy- 
drogen under 30 atmospheres,^^^ no hydrogenation of unsaturated pe- 
troleum hydrocarbons could be detected by Brooks ^" on heating at 
196° for 30 hours under a hydrogen pressure of 3000 pounds per square 
inch. However, Ipatiev ^^^ noted evidence of hydrogenation at higher 
temperatures and under pressures up to 340 atmospheres. 

The low boiling hydrocarbons produced at moderate temperatures 
are mainly normal saturated paraflines as has been shown by Hum- 
phrey in the case of a distillate made from the heavy residues of 
Oklahoma petroleum by distilling at 400°-420° and 100 pounds pres- 
sure.^^" The presence of small quantities of benzene and its homo- 
logues in such distillates has been noted. 

Among the diolefines, which have been identified in the low boiling 
fractions butadiene and isoprene have been repeatedly noted. The 
yield or relative proportions of these hydrocarbons obtainable in this 
way is quite small. Engler and Staudinger,^^" however, have patented 
the manufacture of these conjugated diolefines by the thermal decom- 
position of mineral oils. Pyrolysis under reduced pressure increases the 
proportion of unsaturated hydrocarbons, at least among the gaseous 
products.^^^ 

The polymerization of olefines by heating under pressure has been 
frequently observed. Ethylene, the most stable known olefine, is 
polymerized in the presence of iron at 380°^00° and 70 atmospheres 

"•Z. angew. Chem. 191J,, 522. 

"'J. Frank. Inst. 1915, 658. 

™Ber. St, 2961 (1904). 

^^'J. Ind. <t Enff. Chem. 7, 180 (1915). 

""German Pat. 265,172 (1912). 

121 Whitaker & Rittman loc. cit. 



THE PABAFFINES 43 

pressure, a complex mixture of hydrocarbons being formed."^ The 
polymerization of conjugated diolefines at moderate temperature and 
pressures has been applied to the synthesis of rubber (see page 000) 
and Semmler "= has condensed isoprene with limonene and other ter- 
penes at 275° to form new sesquiterpenes of the empirical formula 
C15H24. Lebedev"* has polymerized allene by heating in glass at 
140° obtaining 5% dimeride, 15% trimeride and 80% of more highly 
polymerized material. Diallyl is very slowly polymerized at 250° to 
a dimeride and a gummy residue. At 150° 2 : 4 hexadine yields chiefly 
the dimeride. The polymerization of olefines is markedly catalyzed 
by many substances. Gurwitsch"^ polymerized amylene by fuller's 
earth at ordinary temperature and Hall polymerized the resin-forming 
constituents (diolefines) contained in light pyrolytic gasoline distillate, 
by passing the hot vapors through a column of fuller's earth. Fuller's 
earth, kaolin and alumina are said to slightly increase the yield of low- 
boiling hydrocarbons. 

The effect of nickel in- a finely divided condition in bringing about 
equilibrium conditions between unsaturated hydrocarbons, hydrogen 
and saturated hydrocarbons, has led to quite changed conceptions re- 
garding the stability of hydrocarbons. The earlier work had to do 
almost exclusively with the formation of saturated hydrocarbons, with 
yields which were practically quantitative. The reversible nature of 
the reaction was not clearly recognized until Sabatier and Senderens 
showed that cyclohexane was converted into benzene in the presence 
of finely divided nickel at 270°-280°. Zelinsky ^^^ showed that cyclo- 
hexane and methylcyclohexane are reduced to benzene and toluene 
respectively, together with free hydrogen, by heating in the presence of 
finely divided palladium. The reaction is appreciable at about 190°, 
and within the range 200°-300°, the equilibrium mixture contains very 
large proportions of benzene.^" No dihydro or tetrahydro derivatives 
were found among the reaction products. Hexane, cyclopentane and 
methylcyclopentane are more stable, and do not yield free hydrogen 
appreciably below 300°. The extraordinary stability of methylcyclo- 
pentane as compared with cyclohexane is shown by later experiments 
of Zelinsky, in which a mixture of methylcyclopentane and cyclohexane 

'''Ipatlev, J. Ruaa. S8, I, 63 (1906). 

"»Ser. t7, 2068, 2252 (1914). 

>"J. S. C. I. im, 1224. 

'"J. Ruaa. il, 827 (1915). 

"•i^. Ruaa. Phva.-CJiem. Soc. ^3, 1220 (1911) ; Ber. U, 3121 (1911). 

1" Tausz & Putnoky, Ber. S2, 1573 (1919), state that in the presence of palladium 
black the formation of benzene from cyclohexane la practically quantitative at 270°- 
300°. They confirm the absence of cyclohexane In Pennsylvania gasoline by testing 
for the formation of benzene under these conditions. 



44 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

were passed o^-er palladium black at 300°, until no further hydrogen 
was evolved. The cyclohexane was converted to benzene, thus offer- 
ing a convenient and easy method of separating these two hydrocar- 
bons.^^' 

That these results are brought about by the catalysts is indicated 
by many observations, for example, Ipatiev ^^^ had shown previously, 
that benzene is not formed from cyclohexane or hexane on passing the 
vapors through an iron tube heated to 650°-700° C. At considerably 
lower temperatures, cyclohexane is readily formed from benzene, the 
reaction being very rapid in the presence of finely divided nickel and 
hydrogen at 160°. The catalytic effect of iron, copper and aluminum 
on the dissociation or addition of hydrogen is very slight. Whether 
or not the iron surface of pressure stills and similar apparatus have 
any catalytic effect on the pyrolytic changes effected by heating pe- 
troleum oils is not certain, but since very finely divided iron has only 
a very slight effect, the catalytic effect of the iron or steel surfaces of 
industrial apparatus is probably negligible. 

It has frequently been proposed to insert catalysts into pressure 
stills and similar apparatus with the object of hydrogenating the ole- 
fines which distillates made in this way normally contain, but these 
methods have had no technical success. Nickel, the most active cat- 
alyst of this type, is very quickly covered with coke and thereby ren- 
dered inactive.^'" Sabatier and Mailhe proposed to remove the carbon 
from the metal catalyst by heating in a current of steam.^^^ 

The lower temperatures at which the reaction of steam and carbon 
becomes appreciable have not been determined and this doubtless varies 
considerably with different forms of carbon. Bergius has converted 
carbon and water to hydrogen and COj by heating at 300° and 150 
atmospheres pressure for 20 days. Although water gas has been manu- 
factured for many years, high temperatures are always employed since 
it has long been known that low temperatures favor the formation of 
COj in the gas equilibrium CO + H2O ±9 CO^ + H^.^^ A number of 
patents have described the decomposition of heavy oils in the presence 
of steam and one patentee claims that iron acts as a catalyst in this 
steam-hydrocarbon mixture."^ This process has been carried out on a 

'"Ber. tS, 678 (1912). 

'"Ber. U. 2987 (1911). 

""The manufacture of hydrogen from methane in the presence of nickel at 700° 
as proposed In the Badlsche process, French Pat. 463,114 (1913), is undoubtedly sub- 
ject to this difficulty. *' 

"'tr. S. Pat. 1,152,765 (1915) ; U. S. Pat. 1,124,333 (1915). 

"= Taylor & Rideal : Catalysis, p. 158. 

>"Noad & Townsend, Brit. Pat. 113,675 (1908). 



THE PARAFF1NE8 45 

fairly large scale, the tubes or retorts being packed with iron turnings 
and a temperature of about 600° maintained. Greenstreet claims that 
the presence of steam in the zone of decomposition prevents the depo- 
sition of carbon or reacts with the carbon to form carbon monoxide and 
hydrogen, the hydrogen being supposed to be taken up by the un- 
saturated hydrocarbons. In the presence of nickel, Sabatier observed 
the reaction of steam and carbon to CO2 and hydrogen at 500°. 

The only catalytic process which has shown great industrial prom- 
ise is of an altogether different type from the catalysts discussed in the 
foregoing paragraphs. Abel and also Friedel and Crafts described the 
decomposition of petroleum hydrocarbons by heating with anhydrous 
aluminum chloride. ^^* Gustavson noted a similar behavior with alu- 
minum bromide. Heusler noted that unsaturated hydrocarbons are 
polymerized by aluminum chloride and also that sulfur derivatives 
are decomposed and the sulfur removed.^^^ Aschan also noted the 
polymerization of olefines in the presence of this reagent and Engler 
observed that amylene, heated with anhydrous aluminum chloride,^^*" 
yielded a mixture of polymers resembling natural lubricating oil. 

A number of patents have been recently issued to McAfee,^^^ who 
has determined the technical refinements necessary in the utilization 
of this catalyst. In addition to a little gas and a mixture of volatile 
saturated hydrocarbons including an excellent grade of gasoline, a 
heavy viscous residue is formed, which contains the greater part of the 
aluminum chloride. This material is very readily carbonized when 
heated, and the recovery of aluminum chloride from these residues is 
the really difficult part of the problem, at least from a technical and 
economical standpoint. The effect of anhydrous zinc chloride and 
anhydrous ferric chloride is similar but much less effective. 

Synthesis of the ParaflSnes. 

The reduction of alkyl halides (chlorides, bromides or iodides) by 
nascent hydrogen has been accomplished in a number of ways. The 
method of Gladstone and Tribe ^^^ of reducing alkyl iodides in alcohol 
solution by 'the copper-zinc couple has been most fruitful. Many of 
these earlier methods were discovered in the attempt to isolate the so- 
called radicals; for example, Frankland showed that heating the sim- 
pler alkyl iodides with water and zinc gave the corresponding hydro- 

"•Friedel & Crafts, Compt. mid. 100, 692; Gustavson, J. prakt. chem. SJ,, 161; 
Egloffi & Moore, Met. £ Chem. Eng. IS, 67, 340 (1916). 

"=Brlt. Pat. 4769 (1877). , „ 

"«Z. anaew. Chem. 9, 288, 318 (1898) ; Ber. 1/2, 4613 (1909). 

"'U. S. Patent. 1,099,096; 1,127,465 and 1,144,304. 

'"Ber. 6. 202, 454, 1136, 1873; J. Chem. 8oo. iS^, 154 (1884). 



46 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

carbons, possibly through the intermediate formation of zinc dialkyls. 
When pure zinc dialkyls are treated with water very energetic decom- 
position occurs with the formation of a hydrocarbon and zinc hydrox- 
ide. 

Zn (C,H,) , + 2H,0 > Zn (OH) , + 2C,H« 

This method has been displaced by the well-known Grignard reaction, 
the simpler alkyl halides readily yielding alkyl magnesium halides 
which are quantitatively decomposed by water to give hydrocarbons. 

C,H,Br -f Mg + (C,H,),0 > C,H,MgBr. (C,H,),0 

OH 

C,H,MgBr . (C,H,) ,0 + H,0 ^ Mg -f C^H^ + (C,H,) ,0 

Br 

Ammonia or an amine may be employed instead of water to decompose 
the magnesium complex. It should be pointed out, however, that an- 
other reaction takes place with magnesium and alkyl halides which, 
though a very subordinate reaction in the case of the simpler alkyls, be- 
comes the principal result with halogen derivatives containing six or 
more carbon atoms. '^^ Thus, like the condensation of propyl bromide 
by metallic sodium to form n . hexane, propyl bromide and magnesium, 
in ether, yields a small amount of n. hexane as expressed by the re- 
action, 

CsH-Br + Mg > CsH^MgBr 

CjHjMgBr + CaH.Br > MgBr. + CeH^, 

This reaction is an admirable method of synthesis within certain 
limits.^*" Thus in the terpene series halides such as bornyl chloride 
react so slowly with magnesium that the Grignard reactions are of 
practically no value for halogen derivatives of this class. Hydrocar- 
bons of an odd number of carbon atoms may be synthesized by a slight 
modification of the method, for example, 

CaH^MgBr + C,H, Br > MgBr, -}- C,Hi 

C.HeMgBr + C,H,,Br > MgBr, + C,H, 

A modification of the above method has proven most satisfactory for 
the preparation of tetramethyl methane, the magnesium complex 
(CH3)3C.MgI being treated with methyl sulfate."^ 

""Grignard & Tissler, Compt. rend. 132, 835 (1901). 

""Alkyl groups may be Introduced in the benzene ring by treating magnesium 
phenyl bromide with propyl or allyl bromide. Tiffeneau, Compt. rend, lis, 437 (1907) : 
Kllng, Oompt. rend. ISrt, 756 (1903) ; Brit. Pat. 122, 630 (1919). 

"'Ferrario & Fogetti, tiaez. CMm. Ital. S8, II, 630 (1908). 



'■li 

•■20 



THE PARAFFINES 



47 



The Grignard reaction has a wide range of usefulness in building 
up substances having the carbon atom structures of the hydrocarbons 
desired, the hydrocarbons themselves then being obtained by other 
methods, for example, 

C2H5 

/ 

RCHO + C^H^MgX > RCH 

OH 



RCOCH3 + C^H.MgX > RC 



/ 



CH, 



\ 

OH 



CaHj 



RCOOCH, + 2C,H,MgX > RC 



/ 



C2H5 



\ 
OH 



C.H, 



CH^ 
^H~ 



RMgX + I >0 * RCH,CH,OH 



the alcohols thus obtained being converted to hydrocarbons by means 
of the corresponding iodide and reduction, or by decomposing the alco- 
hols or corresponding halides to olefines and hydrogenating the latter. 
Hydriodic acid has been widely employed for the purpose of ener- 
getic reduction. Berthelot "^ heated alcohols or alkyl halides with 
concentrated hydriodic acid in sealed tubes and discovered that reduc- 
tion occurs as follows, 

C,HJ + HI >C,H, + I, 

Fatty acids may be reduced to paraffines of the same number of carbon 
atoms by this method and Krafft"^ prepared the normal parafi&nes 
from nonane to tetracosane, C24H50, by converting the ketones, made 
through the lime salts of the fatty acids, into the corresponding chlo- 
rides and reducing the latter with hydriodic acid (in the presence of 
red phosphorus) . 

(C,„H,,),CO > (C,oH,,),CCl, > (C,oH,J,CH, or C,,H,, 

^"J. prakt. chem. (1), m,}03 (1868). 
"'Ber. IS. 1687, 1711 (1882) ; IB. 2218 (1886). 



48 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Magnesium amalgam has been employed for the reduction of alkyl 
halides by Meunier "* and Wislicenus showed that the aluminum-mer- 
cury couple is of wide applicability.^*' Thus isobutyl, n. butyl and 
n. propyl iodides, treated with the aluminum-mercury couple, give the 
corresponding hydrocarbons in nearly quantitative yields in a few 
hours at ordinary temperatures, as compared with heating for 80 to 
90 hours as is necessary with the copper zinc couple. Clemmensen 
has recently shown that ketones and aldehydes are readily reduced to 
hydrocarbons by the zinc-mercury couple and hydrochloric acid.^*^ 
Zelinsky "^ has employed the zinc-palladium couple and alcoholic hy- 
drochloric acid with particularly good results in the case of iodine de- 
rivatives of cyclohexane and cj'clopentane. Ordinarily, alkyl iodides 
give fair yields of the parafiines by reducing with zinc dust in acetic 
acid.^*' 

The classical researches of Sabatier and Senderens have shown 
that ethylene and its homologues may be con^^erted into the corre- 
sponding hydrocarbons by hydrogen in the presence of nickel or nickel 
oxide. With ethylene, copper appears to give the best results.^*' Ipa- 
tiev also employed copper at 300° for the catalytic hydrogenation of 
trimethylethylene to pure isopentane.^^" Brochet and Cabaret ^'^ 
showed that alpha-octene is readily hydrogenated in the presence of 
active nickel and at atmospheric pressure, at temperatures as low as 
65°. At 160° p-hexane and p-octene are rapidly hydrogenated but 
above 200° decomposition occurs with rupture of the carbon chain. 
The methene group > C ;= CH^, as in substances containing the allyl 
group, are more readily hydrogenated than other ethylene types.^'^ 
Limonene, in the presence of copper, is hydrogenated to dihydroli- 
monene, only the A 8.9 group becoming saturated. Platinum black is 
generally not as effecti^•e in catalyzing hydrogenation as nickel and 
copper, but, with this catalyst also, the methene group is more easily 
reduced than other types. For example at 260° propylene is quickly 
reduced to propane and alpha-octene is rapidly hydrogenated at 215° 
but trimethylethylene and beta-hexene are not affected under these 
conditions.^" The relative ease with which the methene group and 

I" C7ompt. rena. ISi, 473 (1902). 
>«J. prakt. Chem. (2), Si, 18 (1896). 
"• Chem. Zent. WIS, 11, 255. 
"'Per. 31, 3205 (1898). 
'"Wislicenus, Ann. eiS, 312 (1883). 

""Sabatier and Senderens, Compt. rend. 130, 1559 (1900) : ISi, 1127 (1902). 
>»Ber. ^, 2089 (1909); ^3, 3387 (1910). 
^"^Cmnpt. rend. 153, 326 (1914). 
"! Albright, J. Am. Chem. Soc. S6, 2188 (1914). 

i» Sabatier and Senderens; Compt. rend, m, 1358 (1897): ISO, 1761 (1900) • 
m. 40 (1900) ; m. 1127 (1902). 



THE PARAFFINES 49 

other define types are hydrogenated by the action of sodium and alco- 
hol is just the reverse of the results noted above. Thus isoeugenol, 
isosafrol and isoapiol are very readily hydrogenated by sodium and 
alcohol but their isomers, containing the methene or allyl group, are 
not."* 

Although the catalytic hydrogenation or "hardening" of fatty 
oils"^ has become of great industrial importance, unsaturated or 
"cracked" petroleum distillates have not been successfully treated in 
this manner, at least not industrially.^^^ It is very difficult to remove 
all of the sulfur from petroleum distillates and very small traces of 
this element are sufficient to poison the ordinary nickel catalyst. Rub- 
ber, prior to vulcanization and free from sulfur, does not appear to 
have been hydrogenated; oily saturated hydrocarbons might result. 

Unstable cyclic hydrocarbons or naphthenes might be hydrogenated 
with rupture of the ring, after the manner of the formation of isopen- 
tane from methylcyclobutane by hydrogen and nickel at 200°."^ 

By employing relatively high pressures, about 30 atmospheres, Ber- 
gius has hydrogenated fatty oils at 300° without a catalyst.'^' Whether 
or not unsaturated hydrocarbons derived from petroleum would also 
be hydrogenated under these conditions has not been determined but 
they are evidently not affected at 196° and 3000 pounds hydrogen 
pressure per square inch."° Whitaker and Rittman ^"^ in the produc- 
tion of oil gas at temperatures within the range 750° to 800° obtained 
distinct evidence of hydrogenation of the gaseous olefines when hydro- 
gen was introduced into the mixture, particularly when operating at 
increased pressures. 

The platinum metals, when in a colloidal state of subdivision, are 
particularly useful in hydrogenating olefines on a small scale or in the 
laboratory. Since the reaction is quantitative, they have been fre- 
quently employed to determine the number of olefine bonds in a sub- 
stance. The development of this method is due chiefly to Paal, Skita and 
Willstatter. Colloidal palladium, prepared according to Paal and Skita, 

""Ciamician and Silber; Ber. 2.3, 1102. 2285 (1890) ; Klages, Ber. 31. 1436 (1899) 

»"'Cf. EUis, "The Hydrogenation of Oils," 1919; Erdmann, J. prakt. Chem. (2), 91 
469 (1915); Paal, Ber. il, 2273 (1908); Skita, "Katalytische Reduktion," 1912- 
Sabatier, "La Catalyse," 1913. 

i»»Cf. TJbbelhode, Petroleum r, 9, 334 (1912) ; Brooks, Bacon, Padgett and Hum- 
phrey; J. Ind. d Eng. Chem. 7, 180 (1915). 

"'Zelinsky; J. Boo. Chem. Ind. S2, 216 (1913); Phlllpow, J. prakt. Chem. (2). 
93, 162 (1916). 

"»Z. /. amgew. Chem. 19H, 522. 

""Brooks, Bacon, Padgett and Humphrey; J. Ind. d Eng. Chem. 7. 180 (1915). 

"•J. Ina. d Eng. Chem. 6, 479 ^1914). 



50 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

is sensitive to acids but Willstatter,"^ Halse^^^ and others have used 
colloidal platinum in glacial acetic acid. Under certain conditions 
palladium may also be used in acetic acid.^*' 

The distillation of fats under pressure has already been referred to. 
The alkali salts of the simpler fatty acids yield paraffines when heated 
with caustic alkali or soda-lime. 

CHgCO^Na + NaOH. > Na^COj + CH,. This reaction does 

not take place to any extent with the higher fatty acids but fairly 
good yields of the paraffines are obtained by heating the alkali salts, 
or soaps, with sodium methylate in vacuo}^* 

Kolbe's electrolytic synthesis has often been cited but has been of 
very little preparative value. Thus, on electrolysing an aqueous solu- 
tion of sodium acetate the chief products are ethane, CO2 and hydro- 
gen.^^^ In general the electrolysis of a fatty acid salt yields, in addi- 
tion to the saturated hydrocarbon, an ester and an define. For ex- 
ample, sodium propionate gives butane, ethylene, ethyl propionate, car- 
bon dioxide and hydrogen. The higher fatty acids salts yield a mix- 
ture of reaction products of the same character.^''^ Aldehydes have 
been converted into the corresponding hydrocarbons by electrolytic re- 
duction but the yields are very poor.^"' 

The well-known method of Wurtz, consisting in heating alkyl bro- 
mides or iodides with sodium, has had wide application in laboratory 
syntheses and it should be particularly pointed out that the reaction 
proceeds easily and with good yields with alkyl halides of high 
molecular weight. Alkyl chlorides have seldom been employed for 
this synthesis although Nef and others have called attention to the 
fact that alkyl bromides and particularly iodides have a much greater 
tendency to decompose to olefines, as in the ether reaction. 

^iC^Hs + Nal + C2H5OH (main reaction) 

/ 

C,H,I + CjH.ONa 

^C,H,.O.aH,-fNaI 

The Wtirtz synthesis has also been useful in ring closing and in the syn- 
thesis of numerous derivatives of cyclic hydrocarbons of both the ben- 

^'^Ber. iS, 1471 (1912). 

'"J. prakt. Ohem. (2) 9S, 40 (1915). 

■"Kefber, Ber. 45, 1946 (1912). 

""Mai: Ber. ii, 2133 (1889). 

>«=Kolbe, Ann. 69, 257 (1849). 

I" Peterson, Z. f. Elektrochemle, 12, 141 (1906). 

■"Scheps, Ber. 46, 2565 (1913). 



THE PARAFFINES 51 

zenoid and non-benzenoid type. Normal hexacontane, CgoHijj, the 
longest normal carbon chain compound known, was made by means of 
this reaction.^'* Optically active hydrocarbons have been prepared by 
employing the iodides of optically active alcohols.^°° 

■"Hell ana Hfigle, Ber. t2, 502 (1889). 

"» It should be pointed but that the only satisfactory methods of preparing pure 
alliyl mono halides are those which utilize the corresponding alcohols. To obtain 
the primary halides, or alcohols, recourse Is often had to the reduction of fatty acid 
esters by sodium and absolute alcohol, according to Bouveault and Blanc (German 
Pat. 164,294 (1903). The addition of halogen acid to alpha-olellnes gives mainly 
secondary halides (E.CHX.CHj.) 



Chapter II. Chemical Properties of 
Saturated Hydrocarbons 

(1). Oxidation. 

The oxidation of saturated hydrocarbons by oxygen, or air, and 
other oxidizing agents is important in several respects, for example, — 
the oxidation of lubricating oil in air compressors, the oxidation and 
carbonization of lubricating oils in automobile or other types of inter- 
nal combustion engines, the oxidation and resinification of trans- 
former oils, the bleaching of oils by air and sunlight and finally the 
oxidation of paraffine and other hydrocarbon mixtures to fatty or soap 
forming acids. Unfortunately very little research has been carried out 
with pure specimens of different types of hydrocarbons with the re- 
sult that we know very little regarding their relative ease of oxida- 
tion. However some of the work recorded, having had to do with com- 
mercial products, is of industrial, if not scientific interest. 

As long ago as 1868 Bolley noted that parafHne wax absorbs oxygen 
at 150° but he made no particular study of the matter.^. Others noted 
that when air is passed through hot mineral oils small quantities of 
acetic and other simple fatty acids are formed.- Holde noted the oxi- 
dation and thickening of mineral lubricating oils when heated in thin 
layers for 10 hours at 100° ^ and in 1896 Byerly and Mabery described 
their now well-known process of manufacturing "artificial asphalt" by 
blowing air through heavy high boiling petroleum residues for four to 
five days at about 230°. The reaction is strongly exothermic and the 
temperature may rise to 300°-400° at the end of the operation. Water 
is formed during the process and very little oxygen remains in the 
final product, typical specimens showing 1.90 to 2.20 per cent oxygen. 
The bromine absorption values of the product are also low, ordinarily 
amounting to 14.0 to 19.0. The hardness and other physical properties 
of this asphalt would seem to indicate that considerable polymerization 
or condensation takes place during the process. Intermediate products 

> Z. 1. Chemie, 1868, 500. 

= Zalozlecki, Z. antjew. Cliem. 1891, 416; Engler & Bock, Ohem. Ztg. 16, 592 (1892). 

'J. Soc. Ohem. Ind. 13, 668 (1894) ; H, 174 (1895). 

52 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 53 

containing oxygen are undoubtedly formed, which may condense with 
the elimination of the water which is always observed. At lower tem- 
peratures oxidation by air has a markedly different result: oxygen is 
absorbed forming fatty or naphthenic acids and some resinous matter. 
It would appear that at the higher temperatures employed by Byerly 
and Mabery the oxidation products first formed, conceivably alcohols, 
aldehydes and ketones, condense with the elimination of water, but at 
lower temperatures, these primary oxidation products are subjected 
to further oxidation to fatty or naphthenic acids. 

According to Worrall and Southcombe* lubricating oil may be 
heated to 760° F. in the presence of steam without causing resiniflca- 
tion or other chemical change (although it may be noted that this is 
approximately the temperature employed by Burton for cracking heavy 
oils to gasoline) . 

The resinous oxidation product which is slowly formed on heating 
mineral oils to 100°-150° in contact with air, may partially be pre- 
cipitated by petroleum ether. The resin behaves as an acid and may 
be removed by shaking out with alcoholic alkali. Kissling " associates 
this resin with carbonization and for testing purposes has proposed the 
determination of "tar numbers" and "coke numbers" of lubricating oils, 
after heating to 150° for 50 hours under standardized conditions.^ 

Transformer oils deteriorate by air oxidation particularly when the 
oil becomes heated as is usually the case when in service. As is indi- 
cated above, water, carbon dioxide, acid resinous material and simple 
fatty acids are formed. The latter are sometimes found in much used 
transformer oils in the form of iron or copper soaps, small quantities 
of which remain dissolved in the oil, and also in the form of insoluble 
basic salts or "sludge." Digby ^ states that these metallic soaps prob- 
ably act catalytically in promoting the oxidation. Waters states that 
"These substances (resinous) are oxidation products, and are most effi- 
cient oxygen carriers." . . . "By heat they become polymerized and 
changed into asphaltic matter." "If they are not removed (as by fil- 
tration through fuller's earth or bone black) heating the oil in the air 
produces more asphalt than would otherwise be the case." A particu- 
lar specimen of a typical resinous deposit showed 76.0 per cent carbon 
and 7.1 per cent hydrogen. The practical importance of the matter is 
apparent from the fact that 0.06 per cent of water in a transformer oil 

*J. 8oc. Chem. Jnd. 21,, 315 (1905). ^ „„„^ 

'Chem. Ztg. SO, 932 (1906) ; SI, 328 (1907) ; Si, 938 (1908) ; SS, 521, (1909). 
"Compare Waters, D. S. Bur. Standards Bull. 7, 365 (1911) ; Circular 99 (1920). 
'■/. Inat. Elec. Sng. 5S, 146 (1915). 



64 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

reduces its dielectric resistance to about 50 per cent of the value for the 
same oil when dry.' Pure paraffine oil can hold this amount of water 
in solution and commercial transformer oils are able to hold in solution 
three to four times this proportion of water. Waters " noted the forma- 
tion of 0.89 per cent of water in a lubricating oil exposed to air and 
light for 22 days. Light, however, accelerates oxidation by air. The 
above observations were carried out with refined commercial oils, but 
small percentages of olefine hydrocarbons were undoubtedly present 
in all the specimens investigated, since refining as ordinarily carried 
out with concentrated sulfuric acid does not remove all the olefines, 
the polymers thereby formed remaining in the oil. Generally olefines 
are more rapidly oxidized by air than saturated hydrocarbons, but 
Waters found that, of several oils examined by him, the one having 
the largest per cent of unsaturated hydrocarbons, as indicated by the 
iodine number and Maumene test, showed the least oxidation. Wa- 
ters suggests that these differences may have been due to greater 
amounts of catalysts or oxygen carriers in the oxidized oils. The con- 
clusion which may be drawn, however, is that factors other than the 
presence of olefines are of primary importance. On account of its de- 
composing action on resins and similar oxidized material, and its ener- 
getic action on unsaturated hydrocarbons, it is possible that oils re- 
fined by anhydrous aluminum chloride would be more stable and more 
resistant to oxidation in service as transformer oils than those oils 
which have been refined in the usual way with sulfuric acid. 

Although the accelerating effect of sunlight on oxidation by air is 
taken advantage of in the industrial sun bleaching of mineral oils, no 
study of individual hydrocarbons appears to have been made. Cia- 
mician and Silber " succeeded in oxidizing the methyl groups of toluene 
and xylene to the corresponding acids by air under the influence of 
sunlight. In the case of non-benzenoid hydrocarbons the group 
R 

>CH2 and RgCH, would probably be oxidized rather than methyl 
R 
groups. 

It has been shown by the well-known work of Engler and Weiss- 
berg " that organic substances, which alone are not appreciably af- 
fected by air or oxygen, may readily be oxidized in the presence of a 

" The method advocated by C. E. Skinner, of purifying old transformer oils by 
quick-lime, removes both water and fatty acids. 
• Loc. cit. 

^Ser. jS. 38 (1912). 
" Vorghnge der Autoxydation, Brunswick, 1904. 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 55 

second substance which is capable of direct oxidation. They have 
shown that the latter class of substances form peroxides and their 
hypothesis is that these peroxides may then effect the oxidation of 
substances which by themselves are inert to oxygen. Thus parafiine 
wax is only very slowly affected by air or oxygen at 150° but the 
oxidation is very much accelerated if a small quantity of previously 
oxidized material is introduced. Unsaturated hydrocarbons which are 
capable of forming peroxides, according to Engler's theory 
RCH = CHRi + O2 > RCH CHRi 

\/ 

0, 

may in this way bring about the oxidation of saturated hydrocarbons. 
Based upon this theory the oxidation of paraffine has been brought 
about by first chlorinating at 160° followed by decomposition of 
these chlorides by heating to 300° and then oxidizing to fatty acids.^^ 
Organic peroxides are decomposed by moisture which explains the 
finding of Charitschkoff mentioned above. Thus linseed oil shows 
greater increase in weight on "drying" in dry air than in moist air, at 
least during the first few days' exposure. 

The oxidation of paraffine wax by air at 120° and 150° was noted 
as long ago as 1868,^^ but under the stress of the conditions prevailing 
in Central Europe during the war intensive research on the synthesis 
of fatty acids was carried out by a special commission of the German 
government, presided over by C. Engler. Numerous researches of the 
same character were undertaken by private concerns and a number of 
patents and published papers have recently appeared dealing with this 
subject. The statements of different investigators regarding the ef- 
fect of metallic oxides and other substances introduced as catalysts 
is very contradictory but the most complete results published up to the 
present time indicate that the best yields are obtained without the 
addition of any catalytic material other than a small amount of pre- 
viously oxidized material added to initiate the reaction.^* The use of 
air under pressure accelerates the oxidation ^^ but the substitution of 
oxygen for air causes the reaction to proceed too rapidly and per- 
oxides are formed and accumulate to such an extent that violent ex- 
plosions are apt to occur. When the oxidation is slowly and carefully 
carried out waxy esters of the fatty acids and higher alcohols, formed 

« Schaarschmldt & Thlele, Ber. SSB. 2128 (1920). 

"BoUy & Tuchschmidt, Z. J. Chemte. 1868, 500; Jazukowitsch, Ber. 8, 768 (1875). 
"Griin. TJlbrich & Wirth, Ber. SSB. 987 (1920). 

"Loffl, CTiem. Ztg. U, 561 (1920). Schneider, J. Soc. Ohem. Ind. ],0, 141A. (1921), 
uses tubular retorts and air under 70 atmospheres pressure. 



56 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

evidently as intermediate products, may be isolated from the oxidized 
mixture.^^ The oxidation to fatty acids, with yields amounting to 
approximately 86 per cent of the theory, takes place in a remarkably 
short time, this yield being obtainable in 12 hours at 160° in the ab- 
sence of catalysts. In a normal oxidation the peroxides noted above 
are decomposed, probably assisting in the oxidation in the manner indi- 
cated by Engler and Weissberg. Carbon dioxide, formic, acetic and 
other simple, volatile fatty acids are formed and the yield of these ap- 
pears to vary within wide limits, one of the "tricks" of the process 
being so to conduct the oxidation that only small proportions of these 
malodorous acids are formed. Presumably these volatile acids are 
removed by blowing with live steam, the residue having an acid num- 
ber of 180 to 200, being then neutralized by alkali and the unsaponifi- 
able portion returned for further oxidation. According to Loffl ^' acids 
satisfactory for soap manufacture have not yet been obtained, the addi- 
tion of 10 to 20 per cent of cocoanut or palm oil being necessary to 
produce a soap of the desired detergent qualities. According to Loffl 
120° is the best working temperature with air under about 45 pounds 
pressure. The presence of water, continually introduced with the air 
in the form of steam, favors the production of the higher fatty acids 
and in the absence of water or its remo^'al as fast as formed the product 
is highly colored and partially resinified. As is usual in such cases a 
large number of special patents have appeared ^* claiming special ad- 
vantages for various catalysts and other minor details of operation 
although the general process seems to have been broadly covered by 
previous publications, particularly the patent of Schaal.^^ Most of 
the published work on this subject has had to do with the oxidation of 
paraffine wax, probably with the idea of manufacturing fatty acids 
identical with fatty acids occurring in natural fats and oils, but in view 
of the much larger quantities of liquid naphthenic hydrocarbons of 
fifteen to twenty carbon atoms (present in kerosene and the inter- 
mediate or fuel oil distillates) and the lower cost of such material, it 
would seem highly desirable to study the oxidation of such oils under 
similar conditions. Although the carboxylic acid derivatives of the 
naphthenes as exemplified by the Russian naphthenic acids, have ob- 
jectionable and very persistent odors, it is probable that these cyclic 

"Griin. Ulbrich & Wlrth. Ber. SSB. 987 (1920). 

" Loc. cit. 

'» Pardubitzer Fabr. Akt. Ges. f. Mineralolindustrle, Brit. Pat. 131,301 : 131,302 : 
131,303 ; Schmidt, Brit. Pat. 109,386 (1907) ; CI. also Fischer & Scheider, Ber. S3. 923 
(1920) ; Kelber, Ber. S3, 66 (1920) ; Bergman, Z. f. angew. Chem. SI, I, 69 (1918) ; 
Holde, Chem. Ztg. 18, 447 (1920) ; Plauson, Bnt. Pat. 156,141 (1919). 

■> Schaal, German Pat. 32, 705. 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 57 

hydrocarbons would be decomposed by oxidation to open chain acids. 
Montan wax is more resistant to air oxidation than parafEne wax.^" 

Harries has applied his well-known method of ozonization to highly 
unsaturated oils such as the oily distillates obtained by the low tem- 
perature carbonization of coal and lignite. 

When saturated hydrocarbons are burned with insufficient air for 
complete combustion, a little formaldehyde is formed. From a hexane 
fraction and isopentane Stepski ^^ obtained water, carbon dioxide, for- 
maldehyde, ethylene and small quantities of propylene, butylene and 
amylenes. The yields of formaldehyde and ethylene by known meth- 
ods are too small for the process to be of industrial value. 

The action of chemical oxidizing agents on saturated hydrocarbons 
shows that certain structures are more easily oxidized than others. 
Zelinsky and Zelikow ^^ have noted that hydrocarbons of the type 

R 

>CHR 
R 

for example (C2H5)2CH.CH3 are readily oxidized by one per cent 
potassium permanganate solution. As contrasted with this, methane 
and ethane are only very slowly oxidized by five per cent perman- 
ganate solutions.^^ The hydrocarbon 2 . 6-dimethyloctane is fairly sta- 
ble to permanganate at 100° but in the presence of unsaturated hydro- 
carbons (menthene) the dimethyloctane is oxidized rather rapidly even 
at 50°.^^ p-Butylhexane is rapidly oxidized by alkaline permanganate 
solution at 80° to 90°, but the only oxidation products which can be 
detected are carbon dioxide and formic acid: by oxidizing it at 25° a 
very small amount of butyric acid can be recognized.^^ Hydrocarbons 
of the type R1R2R3CH are also very easily oxidized by concentrated 
nitric acid, Sp. Gr. 1.53 but normal hydrocarbons, at ordinary tempera- 
tures are only very slowly acted upon. Less concentrated acid, Sp. Gr. 
1.42 =" gives a mixture of nitro derivatives and oxidation products of 
the normal hydrocarbons, and the least oxidation and maximum yields 
of nitro derivatives are obtained by heating, preferably in sealed tubes, 
with dilute nitric acid of 1.075 specific gravity." Paraffine wax is 
slowly oxidized by nitrogen peroxide ^* at temperatures within the 

2» Schneider, J. 800. Chem. Ind. iO, 140A. (1921). 

"Monatah. «S, 773 (1902). 

'^Ber. Si, 2865 (1901). 

"Y. Meyer & Saam, Ber. SO, 1438 (1897). 

"Kishner, J. Rues. J,5, 1788 (1913). 

"Lerene & Cretcher, J. Biol. Chem. S3. 505 (1918). 

"Worstall, Am. Chem. J. 20, 209 (1898) ; 21, 213 (1899). 

»'Konowalow, J. Rubs. Phys.-Chem. Soc. 21, 418 (1895) ; Chem. Zentr. 1900, I, 975. 

=» GrHnaclier, Helv. Ohim. Acta. 3, 721 (1921). 



58 CHEMISTRY OF THE NON-BEN ZEN OID HYDROCARBONS 

range 110°-150°. A mixture of fatty acids, from acetic upwards in 
the series, is produced. Alkaline solutions of these fatty acids are 
red in color due to the presence of nitro compounds. As might be 
expected the results of oxidizing with nitric acid and by permanganate 
are quite different. The fatty acids, with the exception of acetic acid, 
are almost invariably more readily oxidized than the hydrocarbons 
and large yields of the former could, therefore, hardly be expected 
among the reaction products. Prshevalski ^^ has shown that the higher 
normal fatty acids are oxidized by permanganate at two points, i. e., 
at the carbon atom adjacent to the end methyl group and also at the 
carbon atom adjacent to the carboxyl group. Isobutyric acid is oxi- 
dized to the oxy acid (CH3)2 = C — CO2H but with hydrocarbons the 

I 
OH 

molecules are completely broken up. Nitric acid, however, forms a 
series of fatty acids and dicarboxylic acids. In addition to carbon 
dioxide and the simpler fatty acids, oxalic, succinic and adipic acids 
have been observed among the oxidation products.^" Oxidation by 
nitric acid may become violent at 100°.^'- 

Chromyl chloride, CrOjClj has been employed by Etard ^^ and by 
Miller and Rohde ^^ to oxidize the aliphatic side chains of benzene de- 
rivatives. Toluene yields benzaldehj'de and ethyl benzene is oxidized 
mainly at the CHj group to form acetophenone. This interesting re- 
action, however, has not been applied to the study of the paraffine hy- 
drocarbons, although Etard oxidized hexane to a chloroketone and 
Schulz ^* treated a number of light fractions from Boryslaw petro- 
leum with chromyl chloride, obtaining ketone mixtures which were 
not further studied or identified. 

Sulfur. 

Sulfur reacts with paraffines and naphthenes on heating,- hydrogen 
sulfide being e^-olved, but little is known regarding the other products 
formed. Galletly ^= first noted that hydrogen sulfide could conven- 
iently be prepared by heating sulfur and paraffine wax. Somewhat 

"J. Chem. 80c. Ats. wis, I, 1151. 

»« Markownikow, Chem. Zentr. mo, I, 10G4 ; II, 472, 473; Ber. Si. 144 (1899)- 
J. prakt. Chem. (2), 59, ^.^6 (1899). . . . , , v ooo^ , 

"Young & Francis, J. Chem. Hoe. 73, 928 (1898). 
'^Compt. rend. 90, 534 (1880). 
"Ber. 23, 1070 (1890). 
'*Petr. 6, 189. 
"Chem. iWetcs £/,, 107 (1871). 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 59 

later Lidoff ^^ mada hydrogen sulfide by passing naphtha vapors into 
sulfur at 350° to 400°. Friedmann ^' isolated thiocresol as one of the 
reaction products of sulfur and methylcyclohexane but was unable to 
isolate benzene from the reaction product of sulfur and hexane. He 
isolated dinitrobenzene after nitrating the product, which Friedman 
states is possibly due to the initial formation of cyclohexadiene which 
on nitration is converted into dinitrobenzene. Guiselin ^* noted that 
"benzine" dissolves about 0.5% sulfur at 20°, the higher boiling distil- 
lates dissolving somewhat more than this. Raffo and Rossi ^' state 
that pyridine catalyzes the evolution of hydrogen sulfide when hydro- 
carbons and sulfur are heated. Markownikow *" obtained xylene from 
an octonaphthene. Normal hexane *^ is practically inert to sulfur at 
210° but paraffine wax or heavy greases react vigorously at this tem- 
perature. Prothiere *^ obtained 48 liters of hydrogen sulfide from 70 
grams of sulfur and 30 grams of vaseline. It has occasionally been 
suggested that sulfur might be employed to remove hydrogen from 
paraflSnes or petroleum oils to form highly unsaturated oils having 
several double bonds and such products presumably would have the 
general character of drying oils. However, since sulfur reacts much 
more readily with the ethylene bond than it does upon saturated hydro- 
carbons, the result is a certain amount of carbonized material and un- 
changed oil or paraffine, a hydrocarbon molecule once being reacted 
upon then rapidly reacting with more sulfur to form a series of prod- 
ucts of unknown character, the final product resembling asphalt, or 
when strongly heated, petroleum coke. When added to heavy residuum 
and blown with air, sulfur has the effect of giving a markedly harder 
so-called asphalt.*^ Sulfur derivatives frequently exhibit a much 
greater tendency to polymerize than their oxygen analogues and this 
fact may account for the greater hardness, i. e., greater degree of poly- 
merization, of asphalts made from residuum high in sulfur; for example, 
that from Mexican petroleum. Under these conditions a large part 
of the sulfur contained in or added to the original residuum remains 
in the final product. The following results obtained by blowing a 
residuum, 12° Be, from Texas Gulf Coast petroleum, with air are rep- 
resentative. 

•• Chem. Zentr. 188e, 22. 

"J. Chem. Soc. Aha. 1911, I, 13. 

" Petroleum, 191S, 1309. 

"aaas. Chim. Ital. U, 104 (1914). 

"Ber. 1887, 1850. 

" Spanier, Dissertation, Karlsruhe, 1910. 

"Ohem. Zentr. 1903, I. 492. 

"Brooks & Humphrey, J. Ind. d Eng. Chem. 8, 746 (1917). 



60 CHEMISTRY OF THE NON-BENZENOlD HYDROCARBONS 

Effect op Sulfur on Hardness of Blown Artificial Asphalt. 



Sulfur 


Temp. 


Hours 


Penetration 


added % 


°C 


Blown 


mm.* Flowing-point °C 


(1) None 


210 


14 


Too soft for measurement 


(2) 4.0 


210 


10 


61 73 


(3) 6.0 


210 


10 


28 109 


(4) 8.0 


210 


10 


17 148 


(5) 8.0 


215 


10 


13 167 



♦Penetration of No. 2 needle, 100 gram weight for 5 seconds at 25°C. 

Nitration of Non-Benzenoid Hydrocarbons. 

Probably on account of the great industrial importance of nitro 
derivatives in the aromatic series, the nitration of non-benzenoid hy- 
drocarbons of open chain and cyclic structure has been relatively little 
investigated. Oxidation by nitric acid generally takes place to a 
much greater extent in the case of saturated non-benzenoid hydro- 
carbons than with those of the aromatic series and the relative yields 
of oxidation and nitration products depend upon many factors, chief 
of which are the concentration of the nitric acid used and the tempera- 
ture. The constitution of the hydrocarbon is also of importance. The 
use of dilute nitric acid. Specific Gravity 1.025 to 1.075, at 115° to 
125°, constitutes a method whereby fairly good yields of nitro-deriva- 
tives may be obtained. The reaction is usually carried out in sealed 
tubes in the case of very volatile hydrocarbons, but easily nitrated 
hydrocarbons are preferably heated with the dilute acid under a re- 
flux condenser. These methods are due chiefly to Konowalow,^^ and to 
Markownikow.^^ Concentrated or fuming nitric acid or nitric-sulfuric 
acid nitrating mixture gives mostly oxidation products. Hydrocarbons 
containing a tertiary hydrogen atom, RgCH, are most easily nitrated; 
for example, 2, 5-dimethylhexane yields a dinitro derivative,*' which is 
insoluble in alkali solution and which exhibits the exceptional property 
of being crystalline, melting at 124°-125°. 

CHj CH3 CH3 CH3 

CH, — C — CHoCH, — C — CHo > CHo — C — CH„CH~ — C — CH, 



±3 y \j±±2\^A.±2 - 

H H NO, NO, 



The hydrocarbon 2, 6-dimethylheptane similarly gives the tertiary 
nitro derivative, which is easily separated from the relatively small 
amount of primary and secondary nitro-compounds by the solubility 



"Ber. 25, 1244 (1892) ; 28, 1852 (1895) ; 29, 2199 (1896). 

*'J. prakt. Chem. (2) 59, 564 (1899). 

"Konowalow, J. Russ. Phys.-Ohem. Boo. 38, I, 109 (1906). 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 61 

of the latter two classes in aqueous alkali. This solubility in alkali of 
nitro derivatives of the types CH.NO2 and — CHgNOj is a general 
property common to all nitro derivatives of these types,*^ the alkali 
salts probably having the constitution represented by the formulae 



\ // // 

C = N and — CH = N 

/ \ \ 

ONa ONa 

The hydrocarbon 2,7-dimethyloctane yields, with concentrated nitric 
acid, the primary nitro derivatives, but with dilute acid gives 2,7- 
dinitro-, 2,7-dimethyloctane, melting point 101.5°-102°. 

As contrasted with the above hydrocarbons, containing tertiary 
hydrogen, the hydrocarbons 

(CH3)3C.CH,CH3 and (CH3)3C.CH2CH2CH3 
are nitrated only with difficulty; in fact, the former can be purified 
from isomeric hydrocarbons by repeatedly nitrating the fraction boil- 
ing at 48°-51°.^' When these hydrocarbons are nitrated, the nitro- 
group is attached to the carbon atom next to the (CH3)3.C group. The 
normal parafiines are also nitrated much less readily than their branch 
chain isomers. Di-isopropyl (CH3)2CH.CH(CH3)2 reacts very ener- 
getically with nitric acid at 20°, but not with the nitric-sulfuric acid 
nitrating mixture commonly employed to nitrate benzene. 

That saturated non-benzenoid hydrocarbons are more easily ni- 
trated by dilute nitric acid than the benzene ring is shown by a number 
of examples. Phenylcyclohexane is nitrated in the cyclohexane, not 
in the benzene ring.*" Here also nitration takes place at the tertiary 
hydrogen atom yielding 1-nitro-l-phenylcyclohexane 

CH^ — CH, NO2 

/ \ / 

HjC C 

\ /\ 

CH2 — CH2 CgHj 

Ori/io-xylene with dilute nitric acid, Sp. Gr. 1.075 at 110° gives 
o-tolylnitromethane,"" which like all primary nitro compounds easily 
forms alkali salts. Dilution of nitric acid with acetic acid has practi- 

« Cf. Net "Constitution of the Nltroparafflnes." Ann. no, 331 (1892) ; S80, 263 

<a Markowniliow. Chem. Zentr. 1S99, II, 472: Ber. S2, 1446, (1899) : Ber. S3, 1908 
(1900). ^ ^„„ 

" Kursanoff. J. Chem. Soc. Ahs. J307, I, 599. 
»» Konowalow. J. Chem. Soc. Ais. 1905, I, 762. 



62 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

cally the same effect as dilution with water; dilution and heating. di- 
rects the nitration chiefly to the side chain, forming nitro derivatives 
and also acids by oxidation. In accord with the above observations 
1 . 2-diphenylpropane gives the primary nitro derivative rather than 
substitution in the benzene ring, C6H5CH2CH(C6H5) .CH2NO2. Ben- 
zoyl nitrate is a reagent, which with benzene, toluene, phenol, anisole, 
naphthol, coumarine and thiophene gives nitro derivatives very 
smoothly, but when several methyl groups are present, nitration of a 
methyl group takes place, as in durene.^^ 

C,H2 (CH3) , > CeH^ (CH3) 3 . CH2NO2 

In nitrating p-cymene the isopropyl group is attacked at the ter- 
tiary hydrogen atom forming p-methylacetophenone, by oxidation, un- 
less special precautions are taken,^^ advantage being taken of the fact 
that the paraflBnes are but little affected by nitric-sulfuric acid nitrat- 
ing mixture. 

The aliphatic ketones are much more reactive to nitric acid than 
the hydrocarbons. Nitric acid, specific gravity 1.38, yields a mixture 
of products of which dinitro ketones and dinitro hydrocarbon deriva- 
tives are conspicuous, the formation of these products being accom- 
panied by splitting of the carbon structure, probably as indicated by 
the reaction, 

(a) RCO.CH„R' ^RCO.CCNOJ^R' 

(b) R.CO.CCNOJsR' + H^O >RCOOH + R'CHINOJ^ 

Menthone is readily nitrated by dilute nitric acid to the mononitro 
derivative °^ 




= =0 



!-N0, 
CH3 CH, 




•' Willetatter & Knbli. Ber. i2, 4152 (1909). 

"'Andrews, J. Jnd. <f Eng. Chem. 10, 453 (1918). 

" Konowalow, Ber. 26, Eef. 878 (1893) ; 28, Ret. 1054 (1895) 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 



63 



Suflonation 

The difference in the ease with which benzenoid hydrocarbons on 
the one hand and paraffine or non-benzenoid hydrocarbons on the other 
are sulfonated is not as great as is commonly supposed. Although 
data with respect to hydrocarbons of known character and purity are 
extremely meager, Worstall =* showed that n.hexane, n. heptane, and 
n. octane are readily sulfonated by fuming sulfuric acid at the tem- 
perature of a water bath and Markownikow ==^ states that naphthenes 
also are reacted upon by fuming sulfuric acid, both sulfonation and oxi- 
dation taking place. Paraffine wax is attacked by warm fuming sul- 
furic acid but oxidation rather than sulfonation is the result.^" Oxida- 
tion occurs with fuming acid and saturated hydrocarbons to a much 
greater extent than in the case of benzene and its derivatives. Hy- 
drocarbons containing a tertiary hydrogen group as in di-isopropyl 
(CH3)2CH.CH(CH3)2 are much more readily sulfonated and oxi- 
dized than normal paraffine hydrocarbons and it is possible that the 
large losses experienced in the refining of lubricating oils by concen- 
trated sulfuric acid are in part due to the sulfonation and oxidation of 
branched chain hydrocarbons. 

Halides. Preparation and Properties. 

In the following pages the methods of preparation and more par- 
ticularly the properties of the simpler alkyl halides will be discussed. 
Very little work has been done with fluorine derivatives, and such 
information as we have does not indicate that fluorine derivatives 
possess particularly interesting or valuable properties. When writing 
of the halogen derivatives, it will, therefore, be understood that gen- 
erally chlorides, bromides or iodides only are meant. 

Our knowledge of the simpler alkyl halides, especially chlorides, 
has recently been much extended by the development of synthetic 
rubber, and this, it may be noted, is coincident with the production 
of enormous quantities of electrolytic chlorine at very low cost. Cheap 
chlorine makes many processes industrially possible, which heretofore 
have been only of theoretical interest. 

The conditions for the chlorination of methane have been noted 
(page 79). Chlorine reacts readily with butane and pentane and the 
higher paraffines in the cold and in diffused daylight. It has repeatedly 
been observed that in chlorinating petroleum ether a sluggish so-called 
induction period is first noted. The chlorine dissolves in the hydro- 

"Am. Chem. J. 2S, 654 (1898). 

"■Z. Buss. Phys.-Chem. Boc. 1892, 141. 

"Michailescu & Istrati. Bull. Soc. Sci. Bucharest. 13, 143. 



64 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

carbon apparently without reacting, but, after a few minutes, the color 
is suddenly discharged and the reaction thereafter proceeds very 
rapidly. An excellent example of this peculiar induction period " has 
been observed in the case of brominating cyclohexanone and 1, 1-di- 
methylhexanone(3). Catalysts are not necessary, although the pres- 
ence of moisture is distinctly advantageous in the case of the more 
volatile hydrocarbons.^^ The chlorination of petroleum pentane has 
become of industrial importance in connection with the manufacture 
of synthetic amyl acetate (see page 89) . In order to produce mainly 
monochlorides, it is necessary to stop the chlorination after the concen- 
tration of monochlorides in the reaction mixture has reached about 20 
per cent, and separate the unchanged pentane by fractional distilla- 
tion. The relative proportions of the isomeric monochlorpentanes 
formed are not known. Cyclohexane is more reactive to halogens than 
n.hexane. When n.hexane is chlorinated, the CHj groups, not the 
CHg groups, are attacked.^" 

The chlorination of parafHne wax is carried out industrially, the 
product being used as a solvent for dichloramine — -T.^" Boiling the 
product with aniline readily removes most of the chlorine. The higher 
boiling petroleum fractions, are readily chlorinated in diffused day- 
light at ordinary temperature, but the products are very unstable. 

Bromine reacts more slowly with the paraflBnes. Pentanes may be 
brominated readily under the influence of intense illumination, and the 
higher paraffines react readily with bromine when gently warmed and 
illuminated. In the presence of metallic iron or ferric bromide, bro- 
mine readily forms a series of substitution products in which one bro- 
mine atom is attached to each carbon atom, thus 

CHgCH^CH.CH^CH, > CH^Br . CHBr . CHBr . CHBr . CH,Br . 

Normal heptane and an excess of bromine in the presence of iron 
yields 1, 2, 3, 4, 5, 6, 7-heptabromoheptane. Ethyl bromide may be 
brominated under these conditions to ethylene bromide and propyl 
bromide to 1 . 2-dibromopropane.''^ Bromides have been made by treat- 
ing chlorine derivatives, such as CCl^, C2CI4 and CjClg, with anhydrous 
aluminum bromide.*^ 

Sodium iodide reacts with many alkyl chlorides and bromides to 

»' Crossley & Renouf. J. Chem. Soc. 91, 81 (1907). 

MAschan, Uliem. Ais. 1919, 2868. 

™Ber. S9, 2138 (1906); Strauss claims to be able to prepare primary mono- 
chlorides by chlorinating at reduced pressures and temperatures above the boiling- 
point ot the hydrocarbons. (German Pat. 267, 204.) 

"> Dakin & Dunham. Brit. Med. J. 1918, I, 51. 

"V. Meyer & Miiller, J. prakt. Chem. (2) ^6, 171 (1892), 

« Gustavson, Chem. Zentr. mi, 131,642. 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 65 

give the corresponding alkyl iodide and sodium chloride or bromide. 
Sodium iodide dissolves readily in acetone and this solvent yields the 
best results in carrying out the reaction, which usually takes place at 
once at ordinary temperatures, with the separation of sodium chloride 
or bromide.*^ 

Unsaturated substances may be brominated without affecting the 
double bond, substitution taking place, by employing N-bromo-aceta- 
mide. Thus 

{CH3)2C = C(CH3) 2 yields (CH3),C = CCCH,) CH^Br. 

Sodium hypobromite, although a very energetic oxidizing agent, 
converts acetone into carbon tetrabromide (and acetic acid). Bromo- 
form also yields carbon tetrabromide with this reagent."* 

In the great majority of cases, it is much preferable to prepare 
alkyl halides from an alcohol or olefine than by treating the hydro- 
carbons themselves with chlorine or bromine, the latter method giving 
mixtures of isomeric derivatives. Since it is usually possible to ob- 
tain the simpler aliphatic alcohols in a state of purity, they constitute 
a valuable raw material for the preparation of pure mono-halides. 
The methods employed will only be mentioned and reference made to 
original articles or works on preparative methods for further data.'° 

(1) Hydrochloric acid gas, and methyl or ethyl alcohol in the 
presence of zinc chloride gives good yields of the corresponding chlo- 
rides, but this method is practically valueless with the higher alcohols 
on account of the instability of the higher alkyl chlorides in the pres- 
ence of zinc chloride. Tars or heavy polymers are formed with the 
higher alcohols. However, Norris "" has obtained good yields from a 
large number of alcohols by using a large excess of concentrated hydro- 
chloric acid, without zinc chloride. 

(2) Hydrobromic acid and hydriodic acid give very much better 
yields, than hydrochloric acid. With the simpler alcohols the well- 
known sulfuric acid and sodium bromide method gives excellent re- 
sults, but not with the higher alcohols. In the case of the higher alco- 
hols much better results are obtained by the method of Norris,"' in 
which the alcohol is gently heated with the concentrated aqueous acid 

" Flnkelstein, Ber. fS, 1528 (1910). ,^„„„, 
«Dehn, J. Am. ahem. 8oc. SI, 1220 (1909). 

"KV^'wa'tf lM.o2.Z-. f'rm.'ir^m'soo. SB, 1071 (1916). Norris & MuUlken: 
J Am Chem. Sob. ia, 2093 (1920). According to the autbor's experience, the halides 
OTewred aMording to this method are purer and much preferable to similar produrts 
SaTby other methods: Particularly is this true when the halides are to be employed 
S a Grignard reaction. According to German Patent 280,740 the addition of calcium 
chloride is advantageous. 



66 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

and the alkyl halide removed as formed by distillation from the mix- 
ture. This method gives especially good yields with tertiary amy! 
alcohol, tertiary butyl alcohol, octyl alcohol, cetyl alcohol, etc. By 
the Norris method good yields are obtainable in many cases with con- 
centrated hydrochloric acid. In this connection it is of interest to note 
that the glycol S(CH2CH20H)„ gives the dichloride quantitatively 
with concentrated aqueous hydrochloric acid at 60°.^' Tertiary alco- 
hols of the type R0CH2C(0H)R2 give excellent yields of the chloride 
on warming with 38% hydrochloric acid.^* 

(3) The use of PCI3, PCI5 and PBrg in preparing alkyl chlorides 
and bromides is well known, but the yields are greatly reduced by the 
formation of esters of phosphorus or phosphoric acid. Iodides are com- 
monly made by introducing iodine into a mixture of the alcohol and 
red phosphorus which method has been recently improved for the 
simpler alkyl iodides by Adams and Voorhees.^^ Dehn and Davis "' 
state that yields of 85 and 88 per cent of isobutyl and iso-amyl chlo- 
rides respectively can be obtained from the corresponding alcohols 
by adding PCI3 to a mixture of the alcohol with concentrated aqueous 
zinc chloride. In the case of tertiary alcohols, acetyl chloride fre- 
quently reacts abnormally, giving the corresponding chlorides instead 
of the acetates, for example, dimethylbutylcarbinol thus yields the cor- 
responding chloride. 

(4) It is well known that olefines combine with halogen acids to 
form alkyl halides. In the case of hydrocarbons, generally the halo- 
gen will combine with that carbon atom of the olefine group which has 
combined with it the least number of hydrogen atoms, which generali- 
zation is known as Markownikow's rule: 

CH3CH = CH, > CH3CHI . CH3 

CH3 CH3 

>C = CH2 > >C — CH3 

CH3 CH3 I 

Br 

However, small quantities of the isomeric halides are sometimes 
formed. Thus propylene yields very small quantities of n. propyl 

"H. T. Clarke, J. Uhem. Soc. 101, 1583 (1913). Gomberg, J. Am. Chem. 8oc hi 
1415 (1919). This chloride is the now well known "Mustard Gas." ' ' 

"Paloma, Chem. Alls. 1919, 2862. 

"J. Am. Chem. Soc. U, 789 (1919). 

'»/. Am. Chem. Soc. 29, 1328 (1907) ; When PClj reacts with an alcohol, succes- 
sive formation and decomposition of the whole series of possible alkyl phosphites 
results, and the series of reactions may be arrested by choosing the experimental 
conditions to get very large yields of P(0E)8, P(0R)2.0H, P(0E).(0H)2 or P(OH), 
and 3 RCl. [Mllobendzki and Sachnowski, J. Chem. Boc. Ais. WIS, I. 477.] 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBOl^ia 67 

iodide/^ and isobutylene yields, with a solution of HBr in acetic acid, 
about 93 per cent tertiary butyl bromide and 7 per cent isobutyl bro- 
mide.'^ Acetic acid solutions of hydrogen chloride and bromide have 
given particularly good results in the terpene and sesquiterpene series, 
where crystalline hydrochlorides are often difficult to obtain.'^ 

The ability of an olefine to combine with halogen acid depends 
somewhat upon its structure. Thus trimethylethylene 

CH3 

>C = CH.CH3 combines readily with hydrogen chloride, but the 
CH3 

isomeric amylenes do not. Advantage of this fact is taken in one of 
the synthetic rubber processes,^* in which normal pentane is chlorinated 
to a mixture of monochlorides. The monochlorides are converted into 
amylenes by passing over quicklime at 385° to 400° and the resulting 
amylene vapors are passed over alumina at 450°. The amylene frac- 
tion boiling from 34° to 38° contains trimethylethylene, which is re- 
moved by combining with hydrogen chloride and the tertiary amyl 
chloride, boiling point 84° to 86°, isolated by fractional distillation. 

Unstable carbon ring structures are often ruptured by halogen 
acids. Pinene in acetic acid solution gives mainly dipentene dihydro- 
chloride, with rupture of the bridged or cyclobutane ring. 

Bromocyclopropane'^ and bromocyclobutane " and cyclopropyl 
carboxylic acid are converted into open chain compounds by concen- 
trated hydrobromic acid. Thus 

I > CHBr -f HBr > CHjCHBr . CHjBr. 

CH, 

CH, 

I > CH . CO,H + HBr > CH,Br . CH.CH.CO^H 

CH, 



Br:H 



CH,- 



-CH, CH,Br CH, 



-i: 



•^L 



CH^ CHBr CH3 CHBr 

"Michael & Lelghton, J. prakt. Chem. 60, 348, 446 (1899). 
"Ipatiev & Ogonowsky, Ber. S6, 1988 (1903). 

" For good results, the reaction mixture saturated with HCl or HBr should 
be ailowed to stand two or three days in a cool, dark place. 
"Badische A. & S. Fab. Brit. Pat. 18, 356 (1911). 
"WlUstatter & Bruce, Ber. 1,0, 4457 (1907). 
wperkin, J. Chem. Soo. 65, 950 (1894). 



68 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

It will be noted in the last case that the bromine atom of the HBr 
molecule combines in such a way as to place it in the position farthest 
removed from the bromine atom already present in the ring. This il- 
lustrates the positiA-e-negative rule of Michael/' which is not as em- 
pirical as Markownikow's rule. According to Michael's principle the 
combination of two molecules, for example, halogen acid and an olefine, 
tends to occur with such structural results as will give the maximum 
degree of entropy, that is the neutralization of the chemical energies 
or affinities of the reacting atoms. This generalization is, therefore, a 
special case of Ostwald's hypothesis that "every system tends towards 
that state whereby the maximum entropy is reached.'^ 

Michael formulated his principle after a comprehensive study of 
addition reactions. The marked influence of a methyl group is shown 
in the formation of CHgCHBr.CHg from propylene, CHgCBrjCHg 
from CHgCBr^CH^, CH^Br . CH^ . CO^H the chief product of HBr 
and CHj = CH . COjH, etc. The rule is not without many exceptions, 
however. Faworsky '*' considers the matter from the standpoint of 
relative reaction velocities. By heating isopropyl bromide to 250° sev- 
eral times, removing the fraction boiling at 69°-70° each time he was 
able to effect 20 per cent com-ersion of isopropyl bromide to normal 
propyl bromide. The conversion of normal propyl bromide to iso- 
propyl bromide is therefore reversible and the addition of HBr to 
propylene takes place in part contrary to Markownikow's rule and 
Michael's principle, the result being dependent upon the relative ve- 
locities of the two reactions. 

(1) CH3CH = CHj + HBr ^CHgCHBr.CHg (main result). 

(2) CH3CH = CH2 + HBr > CHgCH.CH.Br 

Similar reversible relations were found in the bromopentane series. 
Faworsky confirmed the earlier observation of Eltekow that isobutyl 
and tertiary butyl bromides are in equilibrium at about 210°, as noted 
in the following: 

CHj CH3 

(CH3)3CBr±5HBr+ >C = CH,?± >CHCH,Br. 
CH3 CH3 

In a similar manner it was shown that etliylidene bromide is present 
in the mixture resulting from heating ethylene bromide: 

"J. vrakt. Cliem. ^6, 205 (1892). 

"J. prakt. Chem. 60, 286, 292 (1899); Ber. 39, 213S (190C). 

"Ann. S5i, 325 (1907). 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 69 
CH3r CHBr 



A 



^11 +HBr?±CH3CHBr, 

H3r CH, 



Hydrogen bromide combines with CH^ = CH . CHjBr in the light to 
form trimethylene bromide, CH2Br.CH2CH2Br quantitatively, but in 
the dark considerable propylene bromide is formed.*" 

General Properties of the Simpler Alkyl Halides: One of the most 
conspicuous properties of the alkyl halides is the relative ease with 
which they are decomposed by heat to form olefines and halogen acid. 
Accurate data are practically confined to the simpler substances. The 
decomposition of the two propyl bromides was studied by Aronstein.^' 

Per Cent Dissociation by Heat. 

Temperature n. Propyl Bromide Isopropylbromide 

113° .... 5.40 

138° .... 7,30 

180° 2.9 . 15.10 

210° 10.4 21.00 

262° 31.9 56.00 

Roozeboom *^ has determined similar values for the decomposition of 
tertiary butyl bromide to isobutylene and HBr.*^ 

Temperature Per Cent Dissociation 

115° 4.2 

130° 10,0 

150° 26,0 

183° 42.6 

204° 60.0 

250° 76,0 

300° 85.2 

Chlorine and bromine derivatives of petroleum fractions, kerosene 
fractions for example, are very unstable, and as, noted by Markowni- 
kow *" and others, decompose slowly at ordinary temperatures with 
liberation of halogen acid. When such chlorine or bromine deriva- 
tives are treated with sodium iodide in acetone free iodine is liberated. 
The decomposition of these halides is probably accelerated by light.*^ 
Kipping and Davies attribute the instability of chlorinated petroleum 
oils to compounds of the type R3CX. 

The dissociation of alkyl halides, particularly in the presence of 

"> HoUeman & Matthes, Chem. Aba. 1318, 2545. 

«ieeo. trav. chim. 1, 134 (1882). 

«2Ber. 14, 2396 (1881). ^, ^ . ^. ^ , 

«■ The decomposition of amyl bromides by heat has recently been investigated 

by Colson, Compt. rend. 1918, 1548. 

"Arm. SOI, 185 (1898). . , , .^ 

"PfeltCer, Z. angew. Ohem. 1313, 545, noted the decomposition of nitro stllbene 

dlchloride by light. 



70 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

aluminum chloride, is intimately associated with the subject of the re- 
arrangements which alkyl halides and olefines undergo. Thus Freund '" 
showed that isobutyl halides were partially converted into tertiary 
derivatives on heating with aluminum chloride in sealed tubes,*' and 
the formation of tertiary butyl derivatives of benzol toluene and xylene 
by condensing isobutyl chloride or bromide with these hydrocarbons 
according to Friedel and Crafts' method has been well established by 
Baur.** Nef has advanced two explanations of such rearrangements. 
In his earlier work he supposed the intermediate formation of a nas- 
cent olefine. According to this theory the formation of tertiary butyl 
ethyl ether from isobutyl iodide and alcoholic silver nitrate is as fol- 
lows: 

CHj CHg 

(a) >CHCH,Br > >C — CH^ 

CHs CHg I I 



CH, CH, 



8 



(b) >C — CH,-}-CAOH > >C — CHg 

CH, II CH, ■ 



Ac 



iCzHg 

In a similar manner isobutyl iodide and silver cyanate yield a mixture 
of about two parts tertiary butyl isocyanate and one part of the iso- 
butyl derivative; silver acetate in acetic acid yields about two parts 
tertiary butyl acetate to one part isobutyl acetate.*' Wischnegradsky 
showed that secondary iso-amyl alcohol with halogen acids yields 
chiefly the tertiary halide."" 

CHg 

>CHCH.CHg CHg 

CHg I > >C.CH,CH3 

OH CHg I 

X 

Also the secondary halide, when heated with lead hydroxide, yields the 
tertiary alcohol. 

But the facts are somewhat more involved than is indicated above. 
Thus isobutyl alcohol, when decomposed by heat, and the primary 
isobutyl halides with alcoholic alkali gives a mixture of butylenes 

"J. prakt. chem. (2), ig^ 26 (1875). 

" Tbe nature of the decomposition products of alkyl halides In the presence of 
anhydrous aluminum chloride, either alone or in the presence of saturated or un- 
saturated non-benzenold hydrocarbons, has never been carefully investigated. Cf. Meyer, 
Ber. «t, 2766 (1894). 

"Ber. H, 2832 (1891) ; SI, 1344 (1898) ; Si, 3647 (1899). Nitrated tertiary butyl- 
toluene and xylene are Itnown commercially under the name of artificial musk. 

"Butlerow, Ann. 168, 143 (1873); Nef, Ann. 309,150 (1899). 

"Ann. ISO, 342 (1878). 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 71 

which have been shown to contain isobutylene and a and p-normal 
butylenes. 

CH3 CH3 

>CB..Cli^X > >C = CH2 and 

CH3 CH3 

CH3CH = CH.CH3 

and 
CHjCHjCH =^ CHj 

Nef believed that such facts could best be explained by the inter- 
mediate formation of a cyclopropane ring, which structure is known 
to be ruptured easily. Thus 

CH3 - CH - CH,X CH3 - CH - CH < 

CH^H CH3H 

CH3-CH-CH2 CHa-CH-CH.-CH^ CH3CH = CHCH3 

\/ ^ I I ^ 

CH^ - CHjCH.CH = CH2 

CH3 CH3 

(a) >CHCH2Br > >C — CH^ 

CH3 CH3 I I 

CH3 CH3 

(b) > c — CH2 + C^H.OH > > C — CH3 

CH3 I I CH3 I 

0C,H3 

The reaction of the solvent is frequently important in such reactions. 
Isobutyl iodide and silver acetate give a small yield of about equal 
parts of isobutyl acetate and tertiary butyl acetate. Tertiary butyl 
iodide, however, does not give the acetate except when acetic acid is 
employed as a solvent. It is significant also that tertiary butyl iodide 
gives only isobutylene when treated with silver cyanide, oxide or 
cyanate, nothing resembling a so-called double decomposition reaction 
taking place. Tertiary butyl iodide and silver nitrate in alcohol 
solution gives no trace of tertiary butyl nitrate; nitric acid is not 
known to react with a double bond to give an alkyl nitrate, in the 
same manner that sulfuric acid yields alkyl sulfuric esters."^ 

" Nef, loo. cit. 



72 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

In the amylene series several cases of rearrangement have been 
well established which are capable of a similar explanation. Thus 
primary iso-amyl alcohol and the corresponding halides yield chiefly 
trimethyl ethylene; 



CH3 



CH3 
^CH.CH^CH^X^ >CHCH2CH 
CH3 

CH3 



/ 
\ 



>C — CH, 
CH3 \/ 
CH, 



>C- 
CH3 I 



■ CHo — CHo 



CH, 



>C = CH.CH3 



CH3 

The formation of this olefine from bromotetramethylmethane, ob- 
served by Tissier "' may be similarly explained without resorting to 
the vague idea of the "wandering" of the methyl group. 



(CH3)2C — CH,Br- 
^H, -H 



2^ 



(CH3),C-CH^ 
CH, H 



(CH,) ,C — CH, 

I / 
CH, 



> (CH3) ,C — CH, — CH, -> (CH3) ,C = CH . CH3 

Another rearrangement involving a change in the position of a 
methyl group is that noted by Coutourier.°* 

CH, 



CHBr — CH, 



H,H 



>C 
CH. ^ 

CH3 

>C — CH.CH3 

CH3 1/ 

CH„ 



CH3 
-> >C — c- 
CH, I /H 



■CH, 



CH, 



CH, 



CH, 



-^ >C=:C< 

CH, CH, 



Some support for Nef's theory of such changes is found in the 
properties of the cyclopropane ring (see page 77) . 

The mechanism of dissociation of the alkyl halides and their so- 

"A»». chim. phys. (6), 89, 361 (1893). 
"4»». cMm. phya. (6), 26, 464 (1892). 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 73 

called double decomposition reactions is of fundamental importance. 
Nef °^ has advanced the theory, which he has developed from his 
previous studies of bivalent carbon, that alkylidene dissociation first 
occurs. 

(a) RCH^CH^X > RCH2CH< + HX 

(b) RCH,CH< >RCH=:CH2 

Whether or not olefines are foimd in the reaction products de- 
pends upon the presence or absence of substances capable of reacting 
with the very reactive alkylidene, the rate of this reaction as com- 
pared with the rate of the rearrangement to the olefine, and other 
secondary factors. Thus Nef explains the apparently contradictory 
results obtained by previous investigators by showing that when ethyl 
chloride is decomposed by heating to 550° and the gases subsequently 
passed over soda lime to remove the hydrogen chloride, a nearly quan- 
titative yield of ethylene was obtained. If, however, ethyl chloride 
is passed directly into hot soda lime at 550° ethyl alcohol or rather 
the decomposition products of ethyl alcohol under these conditions, 
acetate, carbonates, methane and hydrogen, are obtained. Hydrogen 
chloride acting upon the soda-lime liberates water, which may then 
react with the labile, reactive alkylidene as follows: 

OH 

(a) CH3CH< + HOH > CH3CH< 

H 

(b) CH3CH< + H^O > CH3CHO + H, 

The behavior of the simpler alkyl halides to alcoholic alkali has 
been thoroughly investigated by Nef, with the results summarized be- 
low: 



Halide 


Olefine % 


Ether % 


Temp. °C. 


C2H.Br 


11. 


60. -70. 


70 ± 5 


C^flJ 


14. 


60. 


40- 90 


CHsCaCaBr 


20. 


60. 


80-100 


CHsCaCHJ 


36.4 


40. 


80-100 


CHsCHBr.CH, 


75.0 


17. 


80-100 


CHsCm.CH 


93.6 


C? 


80-100 


(CHa)2CHCaCl 


.... 


37. 


120 


a 





38.5 


170 


(CH.),CHCH2Br 


64.' 


23. 


90-100 


(CH.).CHCHJ 


98. 


0. 


90-100 


CH. 








(CHs).C < 


97. 


0. 


90-100 


a 









Sodium 
isobutylate used 



•'Ann. S09, 128 (1899) ; SIS, 3 (1901). 



74 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Halide 
CH, 
(CH.).C < 

I 

(CH.).CH.CmCHJ 

an, 

(CH,).C < 

Br 
CHiBr.CHjBr -^viny: 


define % 
97. 


Ether % 
0. 


Temp. °C. 
90-100 


80. 
I bromide, 


70.5 
51. 

? 

quantitative. 


90-100 
90-100 

50- 60 



Vaubel '" has shown that allyl halides give chiefly allyl ether with 
alcoholic alkali under a wide variety of conditions. (For the influ- 
ence of double bonds upon the reactivity of adjacent halogen atoms see 
page 000.) Nef °^ has also shown that the alkyl sulfates, ethyl, n . propyl, 
isobutyl and iso-amyl, react with alcoholic caustic potash to give 
mainly the ethers ROCjHg. On heating the alkyl halides with water, 
alcohols and olefines are formed. The employment of high pressures 
during the hydrolysis greatly increases the yield of alcohols from 
chloropentanes.'* 

Acetates are formed when the alkyl halides are heated with an ace- 
tate of sodium, potassium, silver or lead and the best results appear to 
be obtained in glacial acetic acid under pressure. As with ether for- 
mation noted by Nef the best yields of alkyl acetates are obtained 
from the alkyl chlorides, iodides giving the poorest yields. This well- 
known method is of general application. It is applied industrially in 
the manufacture of artificial amyl acetate and also in the terpene series 
in the conversion of bornyl chloride into the acetates of borneol and 
isoborneol.^' 

The alkyl halides and metallic nitrates give very small yields of 
alkyl nitrates. Thus Bertrand,"" with methyl, ethyl and propyl 
iodides and silver nitrate obtained free nitric acid, and small quantities 
of ethers and alkyl nitrates. Tertiary butyl iodide and alcoholic silver 
nitrate yield isobutylene and tertiary butyl ethyl ether in about equal 
amounts.^"^ Ethylene bromide and alcoholic silver nitrate gives a 
trace only of the dinitrate, a little free nitric acid, some glycoldiethyl 
ether and the chief reaction product is the ethyl ether mononitrate 

CI12OC2H5 

CH2ONO2 

"Ber. H, 1685 (1891). 

"Ann. SIS, 3 (1901). 

••Essex, Hibbert & Brooks, J. Am. Chem. Soc. S8, 1369 (1916). 

™ Camphene is the principal reaction product. 

'"Bull. Soc. CMm. SS, 566 (1881). 

loiNef, Ann. S09, 150 (1899). 



CHEMICAL PROPERTIES OF SATURATED HYDROCARBONS 75 

Alkyl halides, particularly chlorides, can be converted into the cor- 
responding alcohols by heating with alkali formate in methyl alcohol 
solution. Henry "^ first noted the ease with which certain alkyl for- 
mates react with methyl alcohol to give methyl formate and an alcohol. 
Nef prepared acetol in this manner and excellent yields of ethylene- 
glycol can be obtained from ethylene chloride.^"' 

(1) RCH^Cl + NaO^CH >RCHACH (alkyl formate) 

(2) RCH^OjCH + CH3OH > RCH2OH + CH30,CH + NaCl 

There is no appreciable difference in the behavior of alkyl and non- 
benzenoid cyclic halides toward magnesium and in the various appli- 
cations of the Grignard reaction. To cite a few examples among many, 
Borsche used the Grignard synthesis of sulfinic acids to convert cyclo- 
pentyl bromide into cyclopentanesulfinic acid,^°* and Bouveault used 
bromocyclohexane in the preparation of cyclohexanol.^"^ Hesse has 
patented the conversion of bornyl chloride to borneol by the use of the 
Grignard reaction,^"^ but in this case, as with the higher alkyl halides, 
the yields are very poor. Bromocyclohexane, like normal and iso- 
hexane monobromides, is unstable. Alcoholic caustic potash yields 
mainly cyclohexene. 

"» Bull. acad. roy. telg. ISOt, 445. 

""Brooks & Humphrey, /. Ind. d Bng. Chem. 9, 750 (1917). 

^"Ber. ^0, 2220 (1907). 

^"Bull. 80C. cMm. (3), S9, 1049 (1903). 

'"U. S. Pat. 826,165; 826,166. 



Chapter III. The Paraffine 
Hydrocarbons. 

Methane. 

Methane is described in a special section on account of its com- 
mercial importance. One liter of methane (made by the action of 
water on magnesium-methyl iodide) weighs 0.7168 grams at 0° and 
760 mm. pressure.^ Its melting-point is — 184°.^ Its boiling-point 
under 760 mm. pressure is — 164°.^ The critical temperature is 
— -82.85°, the critical pressure 45.60 atmospheres, and the critical den- 
sity 0.1623.* The coefficients of expansion x 10" are A = 3687 and 
B = 3681.= 

The liquefaction of methane has recently become of industrial im- 
portance in connection with the separation of helium from natural gas. 
Pure methane may be separated from ethane and other hydrocarbons 
in this manner, which is a matter of some importance in the industrial 
chlorination of methane. Although both the Linde and Claude proc- 
esses have been employed on a large scale for this purpose, little tech- 
nical information has been published. Satterly and Patterson * have 
determined the latent heat of vaporization of methane to be 130 calories 
per gram and ethane 260 calories per gram. Satterly ' has shown that 
nitrogen dissolves in liquid methane at moderate pressures and Mc- 
Taggart and Edwards ^ have determined the temperature and compo- 
sition relations in the liquid and gas phases in the system methane- 
nitrogen. 

The flame of methane is not very luminous. When burned in an 
Argand burner at the rate of one cubic foot per hour it gives a flame 
of 5.2 candle power. Pure methane on combustion yields 1003 B.T.U. 

' Gnye, Chem. Zentr. 1909 I. 977. 

= Baume & Perrot, compt. rend. 148, 39 (1909) ; also Wahl, Proo. Boy. Soo. StA, 871. 
» Molssan & Chavanne, Compt. rend. Vfl, 407 (1905) ; Olszewski, Compt. rend. 100, 
940 (1885). 

* Cardoso, Arch. sci. phya. not. S6, 97, S9, 400. 
»Leduc, Compt. rend, m, 173 (1909). 
'Trans. Roy. Soc. Canada. IS, 123 (1919). 

for 



'Ibid., a, 109 (1919). 
•Ibid., li, 57 (1919). 



76 



THE PARAFFINS HYDROCARBONS 77 

per cubic foot." Values for natural gas vary from 950 to about 1250 
B.T.U. per cubic foot. 

Methane has no phj-siological effect on men or animals except when 
present in sufficient per cent to produce the characteristic symptoms 
of oxygen deficiency. Mine gas and other mixtures of methane and air 
may, therefore, contain sufficient methane to form explosive mixtures 
and yet cause no physiological symptoms which might serve as a warn- 
ing to miners. Haber ^" has developed an interesting automatic warn- 
ing whistle. 

The largest explosive limits. for methane and air are those deter- 
mined by Burrell and Oberfell, i. e., a minimum methane content of 
4.9 per cent and a maximum of 15 to 15.4 per cent.^^ Initial pressures 
of 5 atmospheres do not appreciably effect these ratios, so that these 
values are practically independent of ordinary variations of barometric 
pressure. Burgess and Wheeler,^^ and Wheeler ^^ find somewhat nar- 
rower limits." Wheeler ^^ also finds that moderate changes of pres- 
sure have only very slight effects on the explosion limits. Coward, 
Carpenter and Payman,^" give 5.6 per cent methane as the lower limit 
of explosibility. Methane and oxygen ignite at 667° and although this 
ignition point is somewhat lowered by certain metals, oxidation in the 
presence of palladium is not appreciable below 404°." This fact 
makes possible the quantitative determination of hydrogen in the pres- 
ence of methane by selective combustion." 

' Richards, "Metallurgical Calculations," 1918, p. 25, gives 970 B. T. U. per cubic 
foot as the net heat of combustion of methane : ethane 1719 B. T. U. and propane 
2464 B. T. U. per cubic foot. 

'» (The U. S. Bureau of Mines has recently demonstrated a highly efficient system 
of warning miners of danger by introducing butyl mercaptan in the air supply.) The 
ECaber apparatus for the detection of methane in mine gases gives -warning as the 
percentage of methane approaches the limit of explosibility. It is based on the principle 
that differences in the density of a gas are indicated by difCerences in the sound 
produced by blowing a whistle or pipe with the gas. The apparatus contains 
two stopped pipes, which are tuned to the same pitch when filled with the same 
gas. When one whistle is supplied, by piped connections, with a mixture of 
methane and air in the proportions corresponding to the lower explosive limit, and 
the other supplied with the mine air, then the simultaneous blowing of the two 
whistles produces a beat whose interval diminishes as the pitch of the two pipes 
approach the same value, or as the mine gas approaches the dangerous composition 
gas in methane content. When near the explosion limit the beat produQCs a charac- 
teristic shrill sound. Cf. Chem. Ztg. 87, 1329 (1913). 

" U. S. Bureau of Mines. Techn. Paper 119 and 121 (1916). 

^J. Chem. Soc. 105, 2591 (1914). 

"J. Chem. Soc. lOS, 2606 (1914) : also Mason & Wheeler, J. Chem. Soc. lis. 45 
(1918). 

" Mixtures of methane and air containing 9.6 per cent methane are the most 
flammable, and the rate of flame travel and explosion violence is greatest with mixtures 
of this composition. Methane and oxygen, in molecular proportions, gives a flame 
velocity of 7,616 feet per second. Mason & Wheeler [J. Chem. Soc. 117, 1227 (1920)] 
give 5.4 per cent, as the lower limit of methane and air mixtures for horizontal flame 
propagation, 

^'J. Chem. Soc. Ill, 411 (1917). 

"J. Chem. Soc. lis, 28 (1919). 

" Denham, J. Soc. Chem. Ind. U, 1202 (1905) ; Phillips, Am. Chem. J. IS, 163 
(1894). 

M Hempel, Z. anal. Chem. Si, 445 (1902) ; Rlchardt, Cliem. Zentr. 1301,, II. 364. 



78 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The mechanism of the combustion of methane and other hydro- 
carbons has been studied by Bone and Wheeler ^'* who found that 
formaldehyde is an intermediate product. Formaldehyde is then fur- 
ther oxidized, with the possible intermediate production of formic acid, 
to water and carbon dioxide. They represent the combustion of me- 
thane as passing through the stages indicated in the following: 

(1) CH. + O^ >H,CO + H,0 

OH 

(2) 2H2CO +O2 > 20c < 

H 

OH 

(3) 0C< > HjO + CO 

H 

(4) 2C0 + O2 > 2CO2 

Methane is exceptionally stable to heat. Bone and Coward ^° have 
shown that its decomposition at 700° is not appreciable, but at slightly 
higher temperatures it is decomposed directly into carbon and hydro- 
gen without the formation of ethylene or acetylene. Coward and Wil- 
son ^^ showed that at 850° the equilibrium mixture contains 97.5 per 
cent hydrogen and 2.5 per cent methane. At 1000° the equilibrium 
mixture consists of 1.1 per cent methane and 98.9 per cent hydrogen. 
At 1200° Pring and Fairlie ^^ found a gas mixture in equilibrium with 
amorphous carbon containing 0.36 per cent methane. The carbon 
formed by decomposing methane in hot tubes, hot furnace checker work 
and the like is not a good commercial black but is gray-black in color 
and usually gritty. Whitaker and Alexander ^^ have called attention 
to the fact that in gas mixtures produced by the thermal decomposition 
of hydrocarbons, equilibrium corresponding to the temperature em- 
ployed is rarely, if ever, attained. The composition of the gas is not 
only dependent upon the temperature to which the mixture is sub- 
jected, but is also markedly affected by the time of heating, the pres- 
sure and the presence or absence of substances which may catalytically 
influence the tendency to establish equilibrium. 

When methane is decomposed in contact with metals, metallic car- 
bides are sometimes formed; in fact, it has been proposed to intro- 

"J. Chtm. 80c. SI, 541 (1902) ; 83, 1074 (1903) ; CI. Armstrone, J. Chem. Soc. 
8S, 1088 (1903). 

^J. Chem. 800. 93, 1197 (1908). 

»i J. Chem. 8oc. US, 1380 (1919). 

"J. Chem. Soc. 101, 91 (1911) ; Bone A Jordan, J. Chem. Soc. 71, 41 (1897) ; 19, 
1042 (1901). 

»/. Ind. d Bng. Chem. 6, 383 (1914). 



THE PARAFFINE HYDROCARBONS 79 

duce carbon into molten iron in this manner. Magnesium carbide is 
rapidly formed by heating the metal with methane at 760°. Man- 
ganese also readily forms a carbide when heated to 800° in methane.^* 

Chlorination of Methane: The industrial production of carbon 
tetrachloride, methyl chloride, chloroform and dichloromethane from 
methane or natural gas, is peculiarly an American opportunity on ac- 
count of the availability of natural gas. No process for the manu- 
facture of methane, as by the hydrogenation of carbon monoxide, has 
as yet been operated on an industrial scale. The problem of manufac- 
turing these chlorinated derivatives is an old one but recent interest in 
this direction is coincident with the steadily increasing value of the 
products of wood distillation, particularly methyl alcohol and acetone, 
and the rapid development of the electrolytic chlorine industry and 
relatively cheap liquid chlorine. Obviously, the maximum economic 
advantage would be secured by bringing natural gas and electrolytic 
chlorine production together. As pointed out elsewhere, natural gas 
varies considerably in the proportions of methane and other hydrocar- 
bons, but so-called dry gases containing very low percentages of ethane 
and higher methane homologues are widely distributed. According 
to reported analyses ^^ such dry gas is available at numerous locali- 
ties in the Louisiana, Texas and California fields and, as has already 
been pointed out, pure methane can be separated from its homologues 
by liquefaction methods so that West Virginia or other gas could thus 
be employed. 

Chlorine and methane do not react in the dark at ordinary tem- 
peratures but Bedford ^^ states that fairly good yields of methyl chlo- 
ride and carbon tetrachloride may be obtained, without explosions, 
by chlorinating at 0° in strongly actinic light. Baskerville and Ried- 
erer^' state that ultraviolet light has very little effect upon the re- 
action but that intense illumination by light strong in the visible blue 
rays is much more effective. Philips ^' heated the chlorine-methane 
mixture and prevented explosions by packing the heated zone with 
sand, asbestos or bone black,^' very similar to the method of smoothly 
chlorinating acetylene. At 300° to 400°, in the dark, the principal 
products are methyl chloride and carbon tetrachloride. Tolloczko 

"Hllpert & Pannescu, Ber. i6, 3479 (1913). 

"Cf. U. S. Bur. Mines. Techn. Paper #255,-11, (1921). "Chlorination of Natural 
Gas" by Jones, Allison & Meighan. 

"J. Ind. & Eng. Ohem. 8, 1090 (1916). 

="■/. Ind. & Eng. Oftem. 5, 5 (1913). 

"Am. Chem. J. 16, 361 (1894). 

^'Yoneyama & Ban [J. Chem. Soc. Ais. 1S21, I. 3] use bone black and fine calcium 
oxide at 250°. 



80 CHEMISTRY OP THE NON-BENZENOID HYDROCARBONS 

and Kling ^° obtained a yield of 78 per cent carbon tetrachloride by 
chlorinating at 400° in contact with pmnice, and impregnation of the 
pumice with cupric chloride is said to favor smooth chlorination. Chlo- 
rination at 400° is also described by Mackayc;^^ The effect of cat- 
alysts upon these reactions is of interest, particularly as regards in- 
creasing the yield of partially chlorinated products. Passing a mix- 
ture of the two gases through active charcoal at 90° was proposed 
by Mallet ^^ in 1879 and Damoiseau ^^ states that methyl chloride may 
be chlorinated mainly to chloroform by passing the proper gas mix- 
ture through animal charcoal heated to 250°-350°. Garner and Clay- 
ton ^* have recently patented a similar method, employing a specially 
activated charcoal as the catalyst. Recent experiments of Jones, Alli- 
son and Meighan ^° indicate that the carbons, particularly anthracite . 
activated by steam at 700° F., are much more effective than silicious 
porous substances, such as pumice, asbestos, silica gels, porcelains and 
glass wool. Although the work of these investigators and others shows 
that chlorination occurs somewhat below 300° in the absence of cat- 
alysts, they employed temperatures within the range 375° to 400° in 
nearly all of their experiments with catalysts. 

Ferric chloride and antimony pentachloride give poor results ^° 
but the work of the U. S. Bureau of Mines indicates that coke impreg- 
nated with iron or nickel gives the highest yields of chloroform, that 
activated carbons give the best yields of carbon tetrachloride and that 
coke impregnated with nickel, tin or lead gives slightly better yields 
of methyl chloride, using larger proportions of methane in the latter 
case. A total yield of about 90 per cent of chlorinated products, based 
upon the gas used, can be obtained. 

Methyl chloride boils at — 23.7°, melts at — 103°; its critical tem- 
perature is 143°, critical pressure 66 atmospheres, critical density 
0.37. The densities and vapor pressures are given in the following 
table." The latent heat of evaporation at 0° C. is 176 B.T.U. per lb. 
or 98 kilogram-calories per kilogram, or 4.94 kilogram-calories per 
gram molecule.^' 

The reduction of carbon tetrachloride to chloroform by zinc and a 

">J. Soc. Chem. Ind. SS, 742 (1913). 

"U. S. Pat. 888,900. 

"V. S. Pat. 220,397. 

"Compt. rend. 91, 1071 (1880) ; 92, i2, 145 (1881). 

"D. S. Pat. 1,262,769. 

"»Loc. cit. 

"Pfelfer, Mauthner & Eeitlinger, J. prakt. Chem. (2), 99, 239 (1919) 

•'Hoist, Betrigerating World, 1319, May, p. 13. ^ /• 



Density, rejerred 


Pressure, absolute 


to water at 30° F. 


in atmospheres 




0.27 


i.b24 


0.47 


1.008 


0.76 


1.000 


1.00 


0.991 


1.16 


0.987 


1.27 


0.972 


1.73 


0.995 


2.49 


0.945 


2.91 


0.936 


3.51 


0.925 


4.20 


0.915 


4.83 


0.892 


6.91 


0.883 


7.96 



THE PARAFFINS HYDROCARBONS 81 

Density and Vapor Pressure op Methyl Chloride. 



-50 
-40 
-22 
-11 

- 4 

- 
+14 
+32 

40 
50 
60 
68 
90 
100 

little aqueous hydrochloric acid ^* and by finely divided iron in the 
presence of water ^' has been carried out and some such method ap- 
pears to offer the best solution thus far proposed for the problem of 
manufacturing chloroform from methane. 

The conversion of methane into hydrocyanic acid by passing a mix- 
ture of methane, hydrogen and nitrogen through an electric arc has 
been tried out on an industrial scale but details of the process have not 
been published.*" 

Rideal and Taylor have reviewed the hydrogenation of carbon 
monoxide to methane.*^ The industrial operation of the process would 
make illuminating gas much less, toxic and increase its calorific value. 
The process might be of value in localities where natural methane is 
not available and where the methane could be utilized for a special 
purpose, for example, the manufacture of chlorinated methane prod- 
ucts. Elworthy *^ proposed to remove the carbon dioxide from water 
gas, add hydrogen sufficient to form the mixture, CO -\- SHj, and effect 
the conversion to methane by passing over catalytic nickel at 250°. 
At one time Sabatier *' attempted the industrial solution of the problem 
in a somewhat different manner. He noted that the carbon deposited 
from the conversion of CO to COj and carbon at 500° in the presence 
of nickel, readily reacts with steam to form COj and methane. By 
superposing the two reactions, passing water gas and superheated steam 
over the catalyst at 500°, mixtures consisting essentially of methane, 
hydrogen and carbon dioxide were produced. Reduced nickel at 250°- 

■» Chem. Rev. 1896, 88. 

"A. W. Smith, U. S. Patent, 753,325 (1904). 

" Chem. Aba. 19U,, 1659. 

" "Catalysis in Theory and Practice." 1919. p. 182. 

«Brit. Pat. 12,461 (1902) ; 14,333 (1904). 

"French Pat. 355,900 (1905). 



82 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

300° in the presence of an excess of hydrogen has been found most ef- 
fective,** but in practice considerable difficulty was experienced by 
poisoning of the catalyst by substances containing sulfur,*^ and the de- 
position of carbon on the catalyst and it was also found that at least 
five volumes of hydrogen are required for one volume of carbon mon- 
oxide. Carbon dioxide is reduced to methane in the presence of nickel 
quite rapidly at 350°.*" The necessary excess of hydrogen can be ob- 
tained by the catalytic conversion of CO and steam to hydrogen and 
COj and removing the latter, or by partially separating the carbon 
monoxide and hydrogen of water gas by liquefaction methods. Bed- 
ford finds that when the liquefaction process is carried out so that the 
uncondensed portion contains approximately 14 per cent carbon mon- 
oxide, the sulfurous impurities are removed with the liquefied CO and 
the resulting mixture has no appreciable poisoning effect on the cat- 
alyst. Bedford carried out the reaction in quartz tubes at 280°-300° 
and owing to the strongly exothermic character of the reaction, 

CO -|- 3H2 > CH4 + H2O + 48,900 calories, the reaction maintains 

itself without external heating. In order to prevent the deposition of 
carbon the concentration of carbon monoxide was kept below 17 per 
cent, the resulting gas containing 28.3 to 31.8 per cent methane. By 
successive additions of carbon monoxide and repassage over the cat- 
alyst a gas mixture containing 76 per cent of methane can be obtained. 
Meredith " states that it is difiicult to prevent the formation of nickel 
carbonyl in this process, although, as is well known, the decomposition 
of nickel carbonyl is rapid at temperatures as low as 200° C. 

Ethane: The simple derivatives of ethane are quite familiar to all 
organic chemists and their reactions have been most frequently em- 
ployed as type reactions in text books of organic chemistry. Yet ethane 
itself has never been a product of industrial interest, and the hydro- 
carbon has not been employed as the raw material for the manufac- 
ture of those derivatives which are so important. For example, ethyl- 
ene, ethyl chloride and ethyl ether are all manufactured from ethyl 
alcohol. Changed economic conditions conceivably may change a great 
many of these processes. That ethane can be separated in quite a pure 
state from methane and propane, was first shown, in an analytical way, 
by Burrell, Seibert and Robertson,** who made use of the large differ- 

" Jochum, J. Gasbel, 57, 73,103,124 (1914). 
"Gautier, Compt. rend, ISO, 1564 (1910). 

" Sabatier & Senderens, Compt. rend, ISi, 514, 689 (1902) ; Farbwerke M. L & Br 
Brit. Pat. 146,110; 146,114 (1920). 
«Gas Age, i7, 7 (1921). 
"U. S. Bureau of Mines, Techn. Paper 104 (1915). 



THE PARAFFINS HYDROCARBONS 83 

ences of the vapor pressures of these several hydrocarbons at low tem- 
peratures. 

By the Linde or Claude methods of fractional distillations at low 
temperatures these gases may be easily separated; in fact, the separa- 
tion of nitrogen and oxygen is considerably more difficult. Reference 
to the boiling-points of these several substances indicates this possi- 
bility. 

Boiling-Point, at 760 mm. Difference 

Nitrogen — 195.84° ) ,„ ok" 

Oxygen ;.. — 182.99M 

Methane — 160. ° ( -^ -o 

Ethane" — 89.3 " f '"•' 

Propane" — 44.1 " 45.2° 

The following vapor pressure curves of liquid ethane were deter- 
mined by Burrell and Robertson, Fig. I, and by Maas and Mcintosh, 
Fig. II. Natural gas and possibly oil gas and petroleum still gases 

Ethane 



-1C 

lOO' 

;/o' 














^^_^ 










^ 


^ 












x^ 












/ 
















/ 
















2 


5 


^ 





s 


^ 


7 


D 


&S 



Vapor P.^essure 
Fig. 2. 

contain ethane in quantities sufficient for its separation on a large 
industrial scale; the high ethane content of many samples of natural 
gas, as determined by the old method of combustion and calculation, 
is undoubtedly inaccurate, as has been previously pointed out, but 10 

"This Talue found by Burrell & Robertson, /. Am. Chem. Soc. 37, 1893 (1915) ; 
Maas & Mcintosh give — 88.5° as the boiling-point of ethane, J. Am. Chem. Soc. SB, 
737 (1914) ; Cardoso & Bell, J. cMm. phys. 10, 497 (1913) ; found the value — 84.1°; 
Maas & Wright, J. Am. Chem. Soc. J,S, 1102 (1921) give the value — 88.8°. 

"Burrell & Robertson, J. Am. Chem. Soc, S7, 2188 (1915). 



84 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



to 12 per cent ethane is not uncommon. Practically pure ethane, sepa- 
rated in this manner, and cheap chlorine, present to organic chemists 
a great opportunity. The manufacture of ethyl chloride, ethylene, 
ethyl ether and ethyl alcohol from ethane is entirely feasible by meth- 
ods now known but which are capable of great improvement. 

The chemical properties of ethane are nearly identical with those 
of methane; it is less stable to heat and in contact with metallic nickel 



aoO| 1111111111(111 — ') 1 1 1 1 1 1 1 1 1 1 1 1 1 

- -4- 




i 3 


-1 i -i 


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700 + ^ 


: ± 


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S erift _, L 


a 500 -j ^ 


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W V f 


S 400 ^ - li - 


a 400 ^ - -rjt^ ^ 


i it S it 


» ^ 'V 


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u 12 


«: / 7 


' - ^ ^ i 


«» J. J. 


zoo ft 


y 2^ 


A r 


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^'^ y 


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ABS. 103.1 
tENT.- 170 



133.1 
^140 



163.1 
-110 



193.1 
-80 



TEMPERATURE - DEGREES 
FlQ. 1. 



at 325° carbon is deposited and methane and hydrogen are formed.'^ 
It is absorbed by fuming sulfuric acid somewhat more rapidly than 
methane.^^ Slow oxidation below the temperature of actual ignition 
yields chiefly water, carbon dioxide, carbon monoxide and formalde- 
hyde.^' It is more readily chlorinated than methane and it is note- 
worthy, in the light of Michael's positive and negative theory of addi- 
tion, that ethyl chloride on further direct chlorination yields chiefly 
ethylidene chlorine but in the presence of antimony pentachloride 

■' Sabatier & Senderens, Compt. rend. IBL 1360 (1897). 
»2Worstall, J. Am. Chem. Soe. 21, 249 (1899). 
"Bone & Stockings, J. Chem. Soc. 85, 696 (1904). 



THE PARAFFINS HYDROCARBONS 



85 



ethylene chloride is the principal product.^* No researches on the 
chlorination of ethane have recently been published.^^ 

Propane: The principal raw materials utilized for the prepara- 
tion of propane and its simple derivatives are acetone, glycerine, tri- 
methylene glycol, propyl alcohol from fusel oil, and propylene from oil 
gas or petroleum still gases. Crude pyroligneous acid contains allyl 
alcohol, but no industrial use for it has been found. The hydrocarbon 
itself is not used as such or separated from natural gas or other gas 
mixtures containing it. Natural gas is the only source from which it 



700- 



S 500- 

I 40o: 

3 
.J 

§ 300- 



2Q0- 
100- 



tfTO-flflTWHj^illlillMllliMlM^r'INIIII^ 
P WWW \^'''WMWWSri^^ ':'A^W¥M 


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ABS. 14ai 
CENT.-130 


163.1 
-110 


183.1 
-90 


203.1 223.1 
-70 -60 

TEMPERATURE. DEGREES 


243.1 
-30 


263.1 
-10 


273.1 




could be separated in quantity. For laboratory study it may conveni- 
ently be prepared by the catalytic decoinposition of isopropyl alcohol, 
over alumina at 380°-400°, and the catalytic hydrogenation of the re- 
sulting propylene to propane.^" 

The vapor pressure curves of liquid propane, propylene and butane 
are shown in the accompanying figure. ^^ 

The chiorination of propane does not appear to have been studied 
since the work of Schorlemmer °' in 1869, who noted the formation of 
n. propyl chloride (?), propylene chloride and more highly chlorinated 
products. Although the monochlorides of methane, ethane, pentane, 
and probably propane and butane can be converted into the corre- 

"D'Ans. & Kautzsch, J. praJct. chem. .(2), SO, 310 (1909); V. Meyer & Muller, 
Ber. Si. 4247 (1891) ; Kronstein, Ber. SJ,B, I. (1921). 

" Cf. Lacy, U. S. Pat, 1,242,208 : chlorinates above 300°. 
"Sabatier & Senderens, Compt. rend, m, 1127 (1902). 
"Burrell & Robertson, J. Am. Chem. 8oc. S7, 2188 (1910). 
"Ann. X52, 159 (1869). 



86 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

spending alcohols with good yields and ethylene chloride may be con- 
verted satisfactorily to the glycol, the more highly chlorinated deriva- 
tive 1, 2, 3, trichloropropane behaves very differently. Caustic alkali 
yields p-epidichlorohydrine CHCl = CH . CHjCl and a-derivative 
CH2 = CCI.CH2CI, and alcoholic potash gives ethylchloroallyl ether, 
C2H5O . CaH^Cl. From what is known of the halogen derivatives of 
propane, it is very improbable that glycerine will ever be manufactured 
industrially by their means. Glycerine can be synthesized by adding 
HOCl to allyl chloride and hydrolysing the product, but when it is 
attempted to prepare allyl chloride by decomposing propylene chloride, 
the principal products are foimd to be a and p chloropropylene. 

Butanes: Normal butane was made by Frankland in the attempt 
to isolate the hypothetical ethyl radical, by the reaction of ethyl iodide 
and metallic zinc. It has been prepared in a very pure state by Le- 
beau by treating n. butyl iodide with sodium amalgam in liquid am- 
monia.^° Its boiling point at 755 mm. is 0.5° ; critical temperature 151° 
to 152°. At 17° and 772 mm. pressure one volume of water dissolves 
0.15 volumes; chloroform at 17° and 768 mm. dissolves 32.5 volumes of 
the gaseous hydro'carbon. 

The most convenient source of n. butyl compounds is n.- butyl alco- 
hol from which a large number of simple derivatives may readily be 
prepared.*" This alcohol is now a common commercial article, being 
obtained together with acetone by fermenting starch with a mould, 
Amylomyces rouxii studied by Fernbach and Strange, and by bacteria, 
probably Bacillus granulobacter pectinovorum, the latter process being 
developed by Weizmann.*^ The butyl alcohol produced in ordinary 
alcoholic fermentation and appearing in the fusel oil fore-runnings is 
isobutyl alcohol, (CH3),.CH.CH,0H. 

The most convenient source of crude butane is the very light gaso- 
line separated from natural gas or "casing head" gas. Garner and 
Cooper have described the isolation of crude butane from this source 
by the application of principles now well known in the industry.'"' 

Butlerow "^ pointed out that two isomeric butanes were possible and 
synthesized isobutane by treating acetyl chloride with zinc methyl, 
according to the well-known Butlerow synthesis, forming the car- 

"» Bull. Ac. Roy. Belg. 1908, 300. 

•»Kamm & Marvel, J. Am. Soc. 1920, 299. 

" Speakman, J. Boc. Chem. Ind. 38, 155 (1919) ; Weizmann, Brit. Pat. 4,845 
(1915) ; Fembach & Strange, Brit. Pat. 14,607 (1915) ; Fernbacli, Biit. Patents, 109,- 
969 (1917) ; 15,203, 15,204 and 16,925 (1911). 

«n. S. Pat. 1, 307,353 (1919). 

-Ann. m. 1 (1867). 



THE PARAFFINE HYDROCARBONS 87 

•CH3 

Isobutane : > CH — CH3 

CH3 

binol (CH3)3C.OH. This was converted into the iodide which on re- 
duction with zinc in the presence of water gave isobutane, an octane 
and isobutylene. 

Isobutane boils at — 10.5° under 757 mm.; its critical temperature 
is 134° to 135°.«* 

The butanes are readily chlorinated by moist chlorine at ordinary 
temperatures.'^ Bromine reacts much less readily and on heating with 
bromine in a sealed tube, it is decomposed forming tetrabromethylene, 
BrjC = CBrj as one of the products."" Isobutylene readily combines 
with hydrogen iodide to form tertiary butyl iodide. 

The Pentanes: Both normal and isopentane occur in petroleum, at 
least in certain petroleums which have been carefully examined. The 
difficulty of separating these two hydrocarbons by fractional distilla- 
tion is well shown by the work of Young,"^ whose results are ex- 
pressed by the following figure: 




Thirteen very careful fractional distillations and the use of a very effi- 
cient fractionating column were required to isolate these two hydro- 
carbons in fair degrees of purity. 

The vapor pressure curves of butane n.pentane, n.hexane, n. hep- 
tane and n. octane are given in the following table: °' 

The pentanes are chlorinated very much more readily than methane 
and ethane, i. e., at 0° in diffused daylight. The relative stability of 

" Lebeau, loc. cit. 

"■Mabery & Hudson, Am. Ohem. J. 10, 244 (1897). 

™Weith, Ber. 11, 2244 (1878). 

"J. Ohem. Soc. n, 906 (1898). 

'•Anderson, J. Ind. Eng. Oliem. 12, 647 (1920). 



88 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

the halogen derivatives of the series ibethane to pentanes inclusive has 
already been noted. 

No satisfactory method of preparing these simple hydrocarbons 
seems to have been developed. The preparation of n.pentane by heat- 
ing acetyl acetone with concentrated hydroiodic acid to 180° and by 
heating pyridine with the same reagent to 300° has been suggested. 
The action of amyl or iso-amyl bromides on magnesium, in ether, 
probably yields a little amylene and decanes,^' but since n.pentane or 
isopentane can easily be separated from these by-products, the method 



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of decomposing amyl or iso-amyl-magnesium bromides by water would 
undoubtedly prove the most satisfactory method of preparing these hy- 
drocarbons in a pure state. By the reduction of iso-amyl iodide by 
zinc fairly pure isopentane can be prepared,^" and Ipatiev made isopen- 
tane by the hydrogenation of trimethyl ethylene.'^ 
• Tetramethylmethane, C(CHg)4, was prepared by reacting upon 
2 . 2-dichloropropane with zinc methyl, 

CH3 CH3 CH3 

>CC1, + Zn(CH3), ^ >C< +ZnCl, 

CH3 C/H3 CI13 

This hydrocarbon'^ is remarkable for its relatively low boiling 
point, 9.5°, and relatively high freezing-point, — 20°. 

"» Cf. Tschelinzeff, J. Rusa. Phya.-Chem. Soc. 36, 549 (1903) : TifTeneau, Compt. rend. 
ISi, 481 (1904). 

"Frankland, Ann. 7j, 53 (1850) ; Just, Ann. 220, 152 (1883). 
"Ber. ^2, 2089 (1909). 
"Lwow, Z. f. Chem. JSno, 520. 



THE PARAFFINE HYDROCARBONS 89 

Aschan^^ has studied the chlorination of the pentane and hexane 
fractions of petroleum and also the chlorination of isopentane, which 
hydrocarbon, Aschan claims, is present in all petroleums. The best 
yields of monochloropentanes are obtained by chlorinating with dry 
chlorine but moist chlorination leads chiefly to the formation of the 
two possible primary chlorides, small proportions of secondary chlo- 
ride and no tertiary chloride. Dry chlorination yields all four pos- 
sible monochlorides the properties of which are given by Aschan as 
follows: 

Boiling-Point D—r- 

10 

4-chloro-2-methyl butane 99. -102.° 0.8692 

3-chloro-2-methyl butane 90. - 93.° 0.8752 

l-chloro-2-methyl butane 96. - 99.° 0.8818 

2-chloro-2-iiiethyI butane 85.5- 88.° 0.8692 

The primary iso-amyl chloride made from natural fusel oil is con- 
verted almost quantitatively to the acetate and alcohol by heating with 
alcoholic potassium acetate at 200°. Isopentyl chloride is only very 
slowly acted upon by 2 per cent caustic potash at 60°-70°. 

The Hexanes: Like the pentanes, normal hexane may readily be 
separated, in an impure state, from light petroleum distillates, and the 
preparation of pure n. hexane depends upon standard laboratory meth- 
ods such as the reduction of secondary hexyl iodide (made from man- 
nite) or the condensation of normal propyl iodide by metallic sodium.'* 

Like pentane it chlorinates readily and it also reacts rapidly with 
bromine in sunlight. The mixture of monochlorides contains about 
10 per cent of the 1-chloro compound and about 45 per cent each of 
the 2 and 3 chloro derivatives.'^ Its reactivity to the halogens, to 
fuming sulfuric acid, to nitration by the dilute nitric acid method, and 
the properties of the simple derivatives, chlorides, alcohols, amines, 
carboxylic acid derivatives, etc., is almost identical with the chemical 
behavior of cyclohexane. 

The Heptanes: Normal heptane enjoys the distinction of being the 
only saturated hydrocarbon, other than the solid paraffines formed by 
phytochemical processes. It is one of the major constituents in the 
volatile oil of the two American pines, Pinus sabiniana and Pinus 
jejjreyi, and also occurs in the "petroleum nuts," Pittosporum resini- 
ferum, of the Philippines. How such a saturated hydrocarbon is 
formed in the living plant is entirely obscure; it is accompanied by 

" Chem. Als. 11,, 3654 (1920). 
"Michael, Am. Chem. J. is, 421 (1901). 
"Michael & Turner, B&r. S9, 2153 (1906). 



90 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

no other substances, so far detected, which conceivably could have 
been the parent substance. Unsaturated hydrocarbons, the terpenes, 
are undoubtedly formed from alcohols, and it is well established that 
such decompositions occur in the leaves of plants. Pine needle oils 
commonly contain borneol and other alcohols although the oleoresins of 
these pines, when finally secreted in the resin ducts of the stem, con- 
tain only resin acids and unsaturated hydrocarbons. The fact that this 
particular hydrocarbon is one of an odd number of carbon atoms is 
also most unusual, since by far the great majority of the hydrocarbons, 
sugars and alcohols, fatty acids and ketones occurring in plants contain 
an even number of carbon atoms. 

Normal heptane probably occurs in most light petroleum fractions, 
as in commercial gasoline.'* Its separation from gasoline, however, in 
a reasonably pure state is a matter of the greatest difficulty. The 
raw material which has been employed for the preparation of the best 
known derivatives of n. heptane is oenanthol or n.heptyl aldehyde." 
This aldehyde undergoes the usual aldehyde reactions, yields l:l-di- 
chloroheptane by treatment with PClg, and on reduction gives n.heptyl 
alcohol from which n.heptyl chloride can be made by the action of 
hydrogen chloride. This is the only one of the four possible monochlor 
derivatives of n . heptane which has been prepared in reasonable purity 
and identified as such. Only three of the possible 17 dichlorides are 
known, i. e., the 1-1, 4-4 and 1-7 derivatives. Until the discovery of 
the Grignard reaction which serves to build up any desired carbon 
structure up to 10 carbon atoms and with limitations, larger mole- 
cules, and also the discovery of catalytic hydrogenation by which 
means unsaturated hydrocarbons may be readily converted at low tem- 
peratures and in neutral reaction media, to saturated hydrocarbons, our 
knowledge of hydrocarbons of the paraffine series containing more 
than six carbon atoms was very limited indeed. 

The physical properties of the known isomeric heptanes are as 
follows: 



Name 
n . Heptane 


Structure 
CH3(Ca).CHa 


Boiling-Point 
98.2-98.5° 


Density 
0.7006- 0° 


2-Methylhexane 


(CH3).CH.(CH3)a.CH3 


89.9-90.4° 


0.7067- 51 

4 


3-Methylhexane 


C.H,.CH(CH3).aH5 


90. -92. ° 


20° 
0.6865-=^ 
4 


'" Young, J. Chem. 


Soc. 73, 906 (1898) ; Engler & 


Hofer, "Das Erdol," 


Vol. I, 244 



(1913). 

" This aldehyde is readily prepared by the well known method of destructive 
distillation of castor oil, enanthol and undecylenic acid being formed. 



THE PARAFFINS HYDROCARBONS 91 

Name Structure Boiling-Point Density 

3-Ethylpentane CH.CCjHb). 95. -98. " 0.689 -27° 

2,2-Dimethylpentane (CHa)aC.CsH, 78.° 0.6910 ^ 

2,4-Dimethylpentane (CH,)2CH.CH2.CH.(CHa)a 83.-84.° 0.7002 ^^ 

3, 3-Dimethylpentane (CH.)jC(C2Hb)j 86. -87. ° 0.7111 0° 

The Octanes: Normal octane probably occurs in most light petro- 
leum distillates, or gasolines. It is most readily prepared in a pure 
state by treating n . butyl iodide with sodium/' a reaction which is said 
to give better yields with alkyl halides of higher molecular weight than 
with the simpler ones. As typical examples of methods which may be 
employed in the synthesis of hydrocarbons, the methods employed in 
the preparation of the known octanes are given in reaction outline, as 
follows: 

(1) Normal octaneP 

2CH3CH,CH,CHJ -^ 2Na > Nal + CH3 (CHJ ^ . CH3 

(2) 2-Methylhe'ptaneP 

CHg CHjCHjCHg 

>CH.CH,CHO + Mg< > 

CH3 X 

CH3 

> CH . CHjCH . CH2CI12CH3 

in 

> corresponding iodide > 2-methyI-heptane, by 



reduction with copperized zinc and hydrochloric acid. 
(3) S-Methylheptane.^" 

CH3CH2CHJ -t- CH3COCH.CO2C2H, > 

Na 

10% KOH 

CH,COCH . CO,C,H, > CH3C0CH3CH2CH,CH 



s 

HjCHjCHj 
CH3C(0H) .CH2CH2CH2CH3 > corresponding iodide- 



i. 



A 



2H5 



3-methylheptane, by reduction as indicated above. 



«Zlncke, Ann. 15B, 15 (1869). ,,„„„^ 

"L. Clarke, J. Am. Chem. Soc. SI, 108 (1909). 
"Ibid.. 558 (1909). 



92 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 
(4) 4-Methylheptane.^^ 

CHaCH^CH^CH.CHs + CHgCOCH.COAHs > 

I Na 

10% KOH 



CH,COCH . CO2C2H5 -^ CHgCH.CH^CH . CH^COCHj 



CH3CI1.CH2CH2CH3 CHs 

by reduction by sodium in moist ether > alcohol 

, iodide > CH3CH2CH2 — CH — CH^CH^CHa 



CH3 

(5) 2.4-Dimethylhexane.^^ 

CH3 
CH3CO . CH^CH . CH2CH3 + Mg < -^ 

CH3 
CH3C (OH) .CH^CH . CH2CH3 

CH3 CH3 

> iodide, which by reduction ^CHaCH.CH^CH.CH^CHa 

CHj CHg 

(6) 2.5-Dimethylhexane. (Di-isobutyl) 

(b)" CH3CO.CH.COAH5 

CH3 
CH2CH< -^CH3C0.CH2CH,CH.CH3 
CH3 I 

CH3 

CH3 
by Mg< -^ CH3C (OH) . CH^CH^CH . CH3 

I I I —> hydrocarbon 

CH3 CH3 as above 

"'L. Clarke, Am. Chem. J. S9, 87 (1908) ; Ber. iO, 352 (1907) ; cf. Clemmensen, 
Ohem. Abs. 6, 2919 (1912). 

•"L. Clarke, J. Am. Chem. Sob. SO, 1144 (1908). 

"Wurtz, Ann. 96, 365 (1855). 

"L. Clarke, J. Am. Chem. Soc. SI, 586 (1009). 



THE PARAFFINE HYDROCARBONS 



93 



(7) 3 .4-Dimethylhexane}^ 

2CH3CH2COCH3 (Methylethyl ketone) ^2CH3CH,CH (OH) .CH, 
— » 2CII3CH2CH . CH3 

+ 2Na -^ CH3CH3CH . CH . CH3CH3 

CI 

(8) 2-Methyl, S-ethylpentane.^^ 
CH3CH2 

CHoCH, 



Br 



>CH.C0CH3 + Mg< 



CH, 



^Hj CH3 
CHoCH, 



CH,CH, 



>CH.C(0H).CH3 



CH, 



by methods given above -> CH3CH, 



CH3 
>CH.CH< 
CH3CH2 CH3 

(9) 2.2.3.3-Tetramethylbutane." 

(CH3)3C.Br+ (CH3)3C.MgBr >MgBr3+ (CH3)3C-C(CH3)3 

Eighteen isomeric octanes are theoretically possible. 

The physical properties of the known octanes are as follows: 



Name 


Structure 


Boiling-Point 


Density 


n. Octane 


CHa(CH.)aCH3 


125.8° 


0° 
0.7185-^ 
4 


2-Methylheptane 


(CH3)3CH.(CH3),CH3 


116. ° 


0.7035-^ 

ID 


3-Methylheptane 


CH3CH3CH.(Ca)3CH3 


117.6° 


0.7167 -||J 
15 


4-MethylheptaEe 


in. 
CH3 

aH5CH.CH3CHCH3 
CH3 CH3 


118. ° 


0.7217 is; 


2 . 4-Dimethylhexane 


109.8°-110. ° 


0.7083 i^ 






±0 


2 . 5-Dimethylhexane 


(CH3)3CH.CH3CH3CH(CH3), 


108.3°-108.5° 


0.6993 i|^ 
lo 


3 . 4-DimethyIhexane 

2-Methyl, 3-ethylpen- 
tane 

2.2.3.3.-tetramethyl- 
butane 


C2H5.CH.CH.C2H6 

CH3CH3 
CHaCH.CH.CH.CH3 

CH3C2H5 

(CH3)3C.C(CHa)a 


116. °-116.2° 

114. ° 

106. °-107. ° 


0.7165 ^ 
0.7084 ^^' 

* 



♦Remarkable for Its high melting-point. 103°-104°. 

"Norris & Green, Am. Chem. J. 26, 313 (1901). 
"L. Clarke, Am. Chem. J. S9, 572 (1908). 
"Henry, Compt. rend. m. 1075 (1906). 



94 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The Nonanes and Decanes: Pure normal nonane boils at 149.5° 
and n.decane at 173°. The petroleum fraction boiling chiefly at 150°- 
170°, therefore, consists chiefly of these two hydrocarbons, when de- 
rived from petroleums of the Pennsylvania type.'* This particular 
fraction is a regular commercial article, being sold as a turpentine sub- 
stitute. Its volatility or rate of evaporation and solvent power for oils 
and resins is practically identical with that of turpentine.'* 

CH3 
2.6-Dimethyl Octane, >CH. (CHJaCH.CH^CH, 

CH3 I 

CH3 

is of interest in that it possesses the carbon structure of the aliphatic 
so-called terpenes, myrcene and ocimene, CioHje, and also the alcohols 
geraniol, linalool and citronellol and their corresponding aldehydes. 
Many of the terpenes proper and their alcohols are very probably re- 
lated genetically to these alcohols and aldehydes and it is therefore 
a matter of theoretical interest, what substance or substances in living 
plants yield alcohols or hydrocarbons of the carbon structure of 
2 . 6-dimethyl octane. This saturated hydrocarbon has not been found 
in nature but is readily made by hydrogenation of myrcene or ocimene, 
or the alcohols geraniol or linalool."" 

Paraffines C10H22 to Ceo^iza- 01 the hydrocarbons of this series 
all the normal parafiines up to C^Jisi ^^^ known, and also a few hydro- 
carbons higher in the series have been deflnitely characterized. Most 
of what is known of the synthesis of the solid parafiines is found in 
three papers published by Krafft,"^ who employed the following meth- 
ods in their preparation: 

(1) Heating fatty acids with hydriodic acid and phosphorus, in sealed 

tubes, to 240°. 

(2) Condensation of n.alkyl primary iodides by means of sodium. 

(3) Preparation of ketones by heating the calcium salts of fatty acids; con- 

version of the ketones, to dichlorides by PCls and reduction by HI 
and phosphorus, 

CitHsjCO . CuHia — > dichloride — > hydrocarbon 

MMabery, Am. Chem. J. 19, 419, 482 (1897). 

'» Much of the special naphtha sold for thinning paint and varnish boils chiefly 
over the range leO-'igO" or considerably above the boiling-point range of turpentine. 
Oils used in paints and varnishes are mlscible in both petroleum naphtha and turpen- 
tine but copals are sparingly soluble in both solvents. Fusion of copals, as in varnish 
making, partially decomposes them and the longer the fusion, or the greater the 
decomposition, the more oil and thinner can be incorporated in the varnish without 
partial precipitation of resins. 

Old oxidized turpentine leaves a resinous film on evaporation and the presence 
of organic peroxides in such turpentine accelerates the oxidation or "drying" of 
linseed oil. However, the difference in behavior on drying films of paint or varnish 
thinned with freshly distilled turpentine, or with petroleum naphtha, is not appre- 
ciable. 

« Willstatter, Ber. J,!, 1478 (1908) ; Enklaar, Ber. 11, 2084 (1908). 

"Ber. 15, 1697 (1882) ; IS. 2223 (1886) ; 89, 1323 (1896). 



THE PARAFFINS HYDROCARBONS 95 

Peterson '" employed the method of electrolysing the fatty acid 
soaps and Mai "' heated the barium soaps with sodium methoxide. 
Formates at 290°-300° °* decompose to parafi&nes. 

Crystalline paraffines have been noted from a wide variety of 
sources but commercial paraffine is derived principally from certain 
petroleums and to a lesser extent from shale oil, ozokerite, and the dis- 
tillates obtained by the carbonization of coal or lignite at low tempera- 
tures. The constitution of the paraffines made by synthesis according 
to the methods indicated above, may reasonably be inferred from the 
methods employed in their preparation, but as regards the crystalline 
paraffines found in the various pyrolytic distillates and in natural 
waxes and essential oils we know practically nothing more than may 
be inferred from their melting-points, and these values may be very 
misleading. Thus Krafft'^ prepared a series of paraffines, by frac- 
tional crystallization, from the crude paraffine isolated from an oily 
distillate from lignite. On the basis of their melting points, varying 
from 22.5° to 76°, the various .crystal fractions are described as eight- 
een distinct substances but many of the specimens so prepared were 
probably mixtures. It is probable that many of these crystalline paraf- 
fines are not normal hydrocarbons, for example, n-eicosane, CjoH^j, 
melts at 36.7° (made by condensing n.decyl iodide by sodium) but an 
isomeric hydrocarbon melting at 69° has been reported from four dif- 
ferent natural sources. 

It is of interest to note the number of essential oils and other natural 
products which contain solid paraffines, and that most of them evi- 
dently bear no relation to the natural fatty acids, having many more 
carbon atoms than these acids. 

Source Melting-Point 

Kaempferia galanga (about 50% of the essential oil)" 10." 

Rose oil 22.° 

Jaborandi leaves 28°-29.° 

Rose oil 40°^1.° 

Birch buds 50.° 

Camomile oil 53°-S4.° 

Orange blossoms 55.° 

Eucalyptus oils" 55°-56.° 

Sassafras leaves 58.° 

Bees-wax ; Virginia and Kentucky tobacco " 59.5° 

•=Z. /. Electroch. 12, 144 (1906). 
"Ber. 22, 2134 (1889). 

»«Fr. Bayer & Co. J. Chem. Soc. Ais. 1918. I, 209. 
"Ber. J,0, 4779 (1907). 

»»Schimmel & Co. Semi-Ann. Rep. 1903, I, 43. 

"'Smith, Chem. Ais. 8, 399 (1914) ; Id Eucalyptus acervula, E. paludosa and E. 
Bmithll. 

""Thorpe & Holmes, J. Chem. Soc. 79, 982 (1901). 



96 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Source Melting-Point 

Verbena 62.5° 

Arnica, essential oil ; pelargonium 63.° 

Camomile, Roman : . 63°-64.° 

Dill oil; Cistus, several species; Chrysanthemum cineraraefolium. . . 64.° 

Wintergreen oil, from Betula and Gaultheria 65.5° 

Bees-wax; leaves of European olive; Kentucky and Virginia to- 
bacco; seeds of Brucea sumatrana; Lippia scaberrina; Micro- 

meria chamissonis; Grindelia robusta; Gymnene sylvestre 68.1° 

Eriodictyon calif ornicum; leaves of European olive; Aithusa cyna- 

pium 74.7° 

Evodia simplex 80°-81.° 

Paraffines are also found in the mineral ozokerite, which is mined 
near Boryslaw, Galicia, and in Wasatch and Utah counties, Utah. Re- 
fining of ozokerite by concentrated sulfuric acid yields ceresine, which 
is valued for its relatively high melting point. When ozokerite is 
distilled crystalline paraffine, about 40 per cent, can be separated from 
the distillate, and the undistilled residue is ozokerite pitch or "oko- 
nite." Fractional crystallization of the solid waxes in Galician ozo- 
kerite gives a series of fractions the lowest melting at about 54° and 
the highest melting at 92.8°-93.2°.''° Practically nothing is known of 
the nature of these hydrocarbons in refined ceresine beyond the fact 
that their analyses indicate the composition CnHj^+j and that their 
chemical behavior is like that of other solid parafiBnes. 

The crystallization of paraffine is considerably affected by the vis- 
cosity of the oil from which it is crystallized and also the presence of 
asphaltic matter seriously interferes with the crystal growth. With 
increasing viscosity of the oil solvent the crystal size diminishes.^"" 
The exact nature of the so-called "amorphous wax" is not known but 
repeated distillation of oils containing much paraffine yields cleaner 
distillates from which large crystals are obtainable without difficulty. 
According to Rakuzin "^ crude petroleums contain crystallizable paraf- 
fine although its crystallization is greatly interfered with by asphaltic 
substances present. He is therefore opposed to Zaloziecki's views as to 
the presence of "protoparaffine" in crude petroleums, but there is no 
doubt that complex substances such as the "kerogen" of oil shale, peat 
and lignite, yield paraffine only when decomposed, as by heat. 

Paraffine is remarkably insoluble in most organic solvents. The 
solubility of a paraffine fraction, melting-point 64° to 65° from Ga- 
lician ozokerite, in petroleum ether is as follows: ^"^ 

" Engler, "Das Erdoel," Vol. I, 667. 

io»cf. ruchs, Petroleum IJ,, 1281 (1919). 

i" J. Buss. PM/a.-Chem. fioo. WIS, 1544 ; J. Chem. Soc. Ai). 19U, I, 489. 

'MPawlewski, Ber, 21, 2973 (1888). 



THE PARAFFINS HYDROCARBONS 97 

g. paraffine in 
Solvent 100 g. solvent 

Carbon bisulfide 12.99 

Petroleum ether, boiling-point below 75° 11.73 

Acetic acid, glacial 0.06 

Since petroleum ether and glacial acetic acid are miscible in all 
proportions, these two solvents are recommended for recrystallizing 
paraffine. In industrial practice the oil and low-melting wax is per- 
mitted to drain slowly from the crude crystals in warm chambers, i. e., 
the "sweating process." 

By several fractional distillations, at 40 mm., Mabery ^"^ separated 
commercial paraffine into several fractions, the lowest melting at 48° 
and the highest at 62°-63°. 

The dielectric constant of paraffine is such that large quantities 
are used for the purpose of electrical insulation, usually in cases where 
the material is not subjected to temperatures high enough to melt the 
wax. Comparisons of the dielectric constant of paraffine and other 
common insulating materials, are as follows: ^°* 

E 

Paraffine, crude brown 2.07 

" melting-point 44°-46° 2.105 

" 54°-56'' 2.145 

" double refined 1.94 

Asphalt 2.68 

Amber 2.80 

Shellac , 3.10 

Gutta-percha 4.43 

Bees-wax 4.75 

The specific heat of paraffine wax is a linear function of the tem- 
perature; at 100° it is 0.6307, at 0° = 0.47, at — 100° = 0.325 and at 
— 180° = 0.199.^°^ The latent heat of fusion of commercial paraffine 
wax, calculated from the lowering of the freezing point on adding sub- 
stances of known molecular weight, ranges from 38.9 to 43.9 calories.^"^ 

Paraffine wax is generally considered to be a very inert material but 
it is attacked by nitric acid and by sulfuric acid at slightly elevated 
temperatures, oxidation rather than nitration or sulfonation being the 
principal result. It reacts readily with sulfur on heating to about 200°, 
evolving hydrogen sulfide ; in fact, this reaction serves as an admirable 
method for the laboratory preparation of hydrogen sulfide, particularly 
where the gas is not continually needed and the apparatus must stand 

""Ct.Am. Chem. J. 3S, 251 (1905). 

"' Landolt-Bornsteln, "Physikallsch-Chemisahe Tabellen," 1SJ2, pp. 1212. 
>»» Nernst, J. Cham. 8oc. Ais. 108, II, 263 (1910) ; Bushong & Knight, J. Ind. <C 
Eng. ahem. 12, 1197 (1920). 

""Kozickl & Pilat, J. Sac. Chem. Ind. S7, 681 A (1918). 



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102 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

idle for long periods.^"^ Chlorine reacts rapidly when passed into the 
melted wax at about 125°, or in solution in carbon tetrachloride. Such 
a chlorinated product, containing about 33 per cent chlorine, has been 
employed as a solvent for chloramine-T, about 10 per cent of this 
germicidal substance dissolving in the "chlorocosane" at ordinary tem- 
peratures.^"' The oxidation of parafiBne by air or oxygen at 120°-160° 
tias already been referred to (see p. 52). ParaflSne is also less stable 
to heat than is sometimes believed. Distillation, at ordinary pressure, 
of a wax melting at 52° causes a decrease in melting-point due to de- 
composition of about 4°. In the old fashioned cracking process as car- 
ried out to increase the yield of kerosene, the wax often crystallizes 
from the distillate in fine large crystals, due largely to decrease in the 
viscosity of the distillate, but, according to Mabery,^"' paraffine is ac- 
tually decomposed during the process. 

Notes on the Refining of Petroleum Distillates. 

Petroleum distillates are refined with the object of removing offen- 
sive odors, removing or lightening the color and also rendering the oils 
more stable in the sense that certain constituents which oxidize readily 
with darkening of color and formation of acids or resinous substances 
are removed. The physical properties of the various fractions are but 
very slightly changed by refining, imless the lowering of the congealing 
point, or cold test, by the removal of parafiine wax may be considered 
as a refining operation. When first distilled from the crude oils the 
lighter fractions, including gasoline and kerosene, are nearly free from 
color and the lubricating oil fractions are clear shades of amber, brown 
or reddish brown, but on standing in contact with air, unrefined gaso- 
line and kerosene become yellow and the lubricating distillates become 
very dark in color. These color changes do not take place appreciably 
in well refined oils. 

Offensive odors are generally pronounced in the case of the more 
v^olatile oils, gasoline and kerosene, particularly when these are made 
from heavier oils by pyrolytic processes. The offensive odor of these 
distillates is commonly attributed to olefines but, with the exception 
of conjugated di-olefines such as cyclohexadiene and cyclopentadiene 
present in light oil gas condensates, the odors of pure unsaturated hy- 
drocarbons are mild and not offensive. The conjugated di-olefines 

>" Fuel oil or lubricating oil also gives HjS on heating with sulfur. 
"«Dakin & Dunham. Chem. Aha. 12. 1079 (1918). 
'"Proc. Am. Phil Soe. 1897, 135. 



THE PARAFFINS HYDROCARBONS 103 

have a sharp irritating odor suggestive of allyl alcohol or acrolein, but 
less pronounced. Unsaturated hydrocarbons generally develop objec- 
tionable odors on long standing due to oxidation, for example turpen- 
tine when fresh is very sweet and pleasant iij odor, deteriorates by 
air oxidation, formic acid being one of the products formed. The con- 
stituents which are chiefly responsible for the objectionable odors of 
petroleum distillates are derivatives containing sulfur, nitrogen bases 
and naphthenic acids. These are very efficiently removed by the usual 
processes of refining with concentrated sulfuric acid and washing with 
caustic alkali, although special methods have to be resorted to in order 
to remove sulfur derivatives from oils derived from certain crudes, for 
example the Frasch copper oxide method as applied to petroleum of 
the Lima-Indiana field. Nitrogen bases in the more volatile distillates 
possess odors closely resembling pyridine. These simpler nitrogen 
bases are generally absent in the case of gasoline and kerosene distilled 
directly from crude petroleums, but are present in pyrolytic gasolines, 
unless made from nitrogen free oil. Petroleums of the Mid-continent, 
Gulf coast, California and Mexican fields on distilling under pressure 
yield volatile malodorous nitrogen bases. Mabery has investigated the 
nitrogen bases present in California petroleum and concludes that they 
are quinoline derivatives. When light distillates, e. g., motor fuel or 
kerosene, containing the simpler nitrogen bases, are treated with cop- 
per oxide, as by the Frasch method, the oxide combines with the or- 
ganic bases and treatment of the resulting copper oxide compound with 
caustic alkali liberates the nitrogen bases. In ordinary practice, how- 
e\'er, the organic bases are very eSiciently removed by treating with 
concentrated sulfuric acid. When the acid sludge is diluted with water 
to precipitate oil and tarry matter, salts of the organic bases and a 
large proportion of the alkyl sulfuric esters, derived from the unsatu- 
rated hydrocarbons, remain in solution in the diluted acid. When this 
diluted acid is concentrated by the usual process of open pan heating 
and evaporation, this dissolved organic matter carbonizes and causes 
the destruction of a portion of the acid. The charring of this organic 
matter with the separation of carbon seriously interferes with the oper- 
ation of cascade evaporating systems by clogging of the overflow lips. 
The tarry matter precipitated by diluting the sludge derived from 
treating lubricating oils, also generally contains nitrogen bases, as can 
readily be shown by heating or distilling with an excess of lime, but 
the quantity of ammonia thus obtainable is too small to be of indus- 
trial interest. 



104 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Sulfuric acid is also very effective in removing naphthenic acids, 
as was first shown by Zaloziecki/** and Gurwitsch ^*^ later showed that 
this removal of naphthenic acids is not merely a solution effect and 
that far greater proportions of the naphthenic acids present pass into 
the acid layer than corresponds to the proportions required by the 
law of partition coefficients. These observations are in accord with the 
findings of Kendall and Carpenter who showed that a very wide variety 
of organic substances containing oxygen, e. g., aliphatic and aromatic 
acids, ketones, aldehydes, and phenols, form addition products with 
concentrated sulfuric acid and they regard these addition products as 
oxonium compounds. American petroleums do not contain conspicu- 
ous proportions of naphthenic acids, as do most of the Russian oils, 
but many of the Gulf Coast oils contain naphthenic acids of high 
boiling-point. These high boiling naphthenic acids are removed from 
the lubricating oil distillates by alkali. They are nearly odorless and 
their alkali soaps are very easily salted out of solution on account of 
their large molecular weight. They have apparently not been investi- 
gated and nothing definite regarding their empirical composition or 
chemical character is known. They are not recovered in present 
refinery practice. 

Practically nothing is known of the nature of the coloring matters 
in petroleum distillates. When such oils darken by air oxidation, amor- 
phous asphalt-like substances are formed. Sulfuric acid is very ef- 
fective in removing coloring matter, which is readily understood if the 
coloring matter consists largely of substances containing oxygen or 
nitrogen. It is improbable that these coloring matters are hydro- 
carbons, since the few colored hydrocarbons which are known contain 
conjugated imsaturated groups, as in the hydrocarbons of the fulvene 
series. Some writers regard the removal of such coloring matter by 
sulfuric acid as a purely physical or colloid phenomenon."^ However, 
as all refiners know, it is necessary to use concentrated sulfuric acid 
in order to hold the tarry matter in solution, since in addition to the 
small amount of coloring matter present in the original unrefined lubri- 
cating oil, constituents are present which yield tar on treating with 
acid. Although water white gasoline and kerosene can be made with- 
out great difficulty, it is impossible entirely to remove the color from 
lubricating oils by sulfuric acid (or oleum) and alkali treatments. 



"< Chem. Ztg. 1S92, 905. 

'"Z. 1. physa. Chem. 87, 323 (1914). 

"» Ubbelohae, Petroleum, i, 1395 ; Schulz, Petroleum, 5, No. 4 and 8. 



THE PARAFFINS HYDROCARBONS 105 

Pale yellow viscous oils can be made in this way which are practi- 
cally tasteless (liquid paraffine oil) but filtration through fuller's ^*^ 
earth, bone black or similar material, or distillation in vacuo, must be 
resorted to in order to obtain colorless oil such as is desired for phar- 
maceutical purposes. 

The fluorescence of petroleum distillates is due to substances which 
are largely removed by sulfuric acid, although several treatments with 
concentrated acid followed by treatments with oleum {15% SO3) are 
necessary entirely to remove them. This property also has been re- 
garded by some writers as being due to particles of sulfur, carbon 
or other substance in a colloidal degree of dispersion, or due to the 
presence of substances having extremely large molecules. Although 
such mixtures are not optically homogenous and do show pronounced 
Tyndall effects, true fluorescence is not observed in aqueous or oil 
suspensions. Most petroleum distillates and certain crude petroleums 
which are sufficiently free from asphaltic matter, such as light Penn- 
sylvania crudes, exhibit green, bronze-green, bluish green or clear blue 
fluorescence. Examination of carefully filtered fluorescent oils in a 
quartz ultramicroscope of the Zsigmondy type shows no particles in 
suspension.^*' When sulfuric acid sludge is diluted with water and 
filtered to remove oil and tar the resulting aqueous solutions are usu- 
ally highly fluorescent. In other words, the fluorescent substances 
have been sulfonated to water soluble sulfonic acids. It is probable, 
therefore, that the extremely small quantities of fluorescent substances 
which are present in petroleum are highly condensed or benzenoid hy- 
drocarbons. ^*° Such fluorescent substances are commonly formed when 
any organic substance is charred, for example, boiled linseed oil ex- 
hibits fluorescence if even slight carbonization occurs during the boiling 
process. The heavy waxy distillates obtained toward the end of the 
heating of an old-fashioned coking still are highly fluorescent. 

For various trade reasons it is sometimes desirable to modify the 
fluorescence and so-called "de-blooming" reagents are sometimes added 
to the oil. Thus nitronaphthalene is sometimes employed for this pur- 
pose. It is well known that the fluorescence of all organic substances 
which possess this property is greatly modified by various solvents 

"" It Is probable that the color absorbing qualities of fuller's earth are dependent 
upon the presence of partially dehydrated amorphous silica. Certain American refin- 
eries have recently manufactured a bleaching material superior to fuller's earth, 
by treating natural talc-like hydrated silicates with sulfuric acid, washing neutral 
and activating by drying at not too high temperatures. 

'"Brooks and Bacon, J. Ind. d Eng. vnem. 6, 623 (1914). 

"" That the fluorescent constituents are not nitrogen derivatives Is indicated by 
the fact that 80% sulfuric acid does not remove them. 



106 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

and the fluorescence of petroleum is affected by the common solvents "" 
in a way entirely parallel to the findings of Kauffman ^^^ in the case 
of the diaminoterephthalic acid methyl esters. Carbon bisulfide, nitro- 
benzene, and aniline diminish the intensity of the fluorescence and 
change its original bluish green character to dull green. Amyl alcohol 
and petroleum ether intensify the fluorescence and enhance its bluish 
character. Filtration of oils through fuller's earth does not remove the 
fluorescent constituents appreciably. Oxidizing agents destroy the con- 
stituents in question and sun-bleached oils which have thus been sub- 
jected to air oxidation are considerably altered in this respect, usually 
acquiring a brownish green or muddy fluorescence. 

The per cent of sulfur in the various petroleum fractions is very 
greatly reduced by treating with concentrated sulfuric acid, except 
in the case of highly unsaturated pyrolytic distillates when treated 
with a relatively small quantity of acid, in which case an increase in 
sulfur content may be observed. This is due to the formation of neu- 

RO 

tral esters of the type >S02. No real explanation of the removal 

RO 
of sulfur compounds from mineral oils by sulfuric acid can be ad- 
vanced since our knowledge of the nature of these substances is so 
meager. Mabery and Smith ^^^ found that on treating a distillate 
from northern Ohio oil with sulfuric acid the sulfur content was re- 
duced from 0.51% to 0.13%, and according to Robinson ^^^ sulfuric 
acid, 98% H.SO^, is much more effective than ordinary acid, a certain 
Ohio distillate containing 0.346% sulfur being thus refined to 0.05% 
sulfur. 

The reactions of sulfuric acid and pure olefines of different types 
have been discussed in another section. It is there shown that the 
hydration of the olefines to alcohols is important only with ole- 
fines of four to eight carbon atoms and that on standing in contact 
with the acid the proportion of polymers increases and the yield of 
alcohols decreases. With olefines of ten or more carbon atoms and 
containing one double bond, polymerization is the principal result; in 
certain instances being practically quantitative. In so far as the 
polymerizing action of sulfuric acid on unsaturated hydrocarbons is 
concerned, the specific gravity and viscosity of petroleum distillates 
should be increased by refining. Usually a slight decrease in these 

'"> Brooks & Bacon, loc. cit. 
"^Ann. S9S, 1 (1912). 
'"Am. Chem. J. 189i, 88. 
"> Ohem. Ztg. Rep. 1907, 194. 



THE PARAFFINS HYDROCARBONS 107 

values is observed after refining in this way, particularly in the case 
of lubricating oils. The effect of refining on the specific gravity of a 
number of pyrolytic gasolines, made by distillation of heavier oils 
under pressure of 100 to 150 pounds is indicated in the following: ^" 

25° 

Specific Gravity 

25° 

Loss on refining, 

Original gasoline After refining % by volume 

0.739 0.743 9.0 

0.729 0.735 8.2 

0.727 0.748 9.8 

0.737 0.754 10.1 

0.730 0.749 10.6 

Such oils refined and washed in the usual way become discolored on 
standing a few weeks, but if they are redistilled after refining, this 
discoloration does not take place, at least by no means rapidly. Such a 
redistillation also may serve the purpose of removing the heavy oily 
polymers formed by the acid treatment and which are commonly be- 
lieved to be objectionable constituents of gasoline when used as motor 
fuel or for extraction or cleaning purposes. 

One of the effects of treating highly unsaturated oils with relatively 
small proportions of sulfuric acid is to form alkyl sulfuric esters which 
remain dissolved in the oil and are not washed out by alkali. This is 
shown in the following treatment of a mixture of hexenes: 

SuLPUHic Esters in Refined Hexene. 



Vol. Oil cc. 


Vol.H^O.cc. 


Vol. Residual 
Oil cc. 


g. SOi on 
Distillation 


% Calc. as 
(RO)^O, 


50 
50 
50 


25 

50 

100 


32 
28 
26 


0.284 
0.146 
0.094 


4.9 
2.9 
1.8 



The concentration of the sulfuric acid employed has a marked effect 
upon the sulfur thus introduced, as is shown by the following results of 
Condrea,^'® on a Roumanian kerosene, refined by a 2% volume of acid 
at 20°: 

Acid concentration.. 90% 95% 97% 100% 5% SO, 10% SO2 20% SOs 

Color mm. to stand- 
ard 135 

SOa.g. per 1 liter. . . . 0.157 

Sulfonic acids in acid 

tar 1.30 2.57 4.20 7.30 12.45 16.77 35.00 

Refining with sulfuric acid at low temperatures greatly reduces the 
oxidizing effect of the acid, with less attendant tar and color formation. 

'" Brooks and Humphrey, loc. clt. 
"'iJOT. petrol. 1311, 61. 



175 


230 


290 


285 


270 


240 


0.294 


0.426 


0.67 


1.30 


1.71 


2.87 





Add Tar 


Unused 


Temp. °C 


Grams. 


H^O, 





61.6 


47.91 


5 


62.0 


46.82 


10 


62.5 


46.53 


15 


63.5 


45.72 


20 


64.3 


44.37 


25 


64.8 


43.52 


30 


65.2 


41.87 


40 


66.0 


39.03 


50 


67.0 


37.26 



108 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

It is well known that lighter colored oils are produced by operating at 
low temperatures, but some difference of opinion exists as to the effi- 
ciency of the refining in other respects. Zaloziecki ^^° gives the follow- 
ing data obtained by treating a Galician kerosene with sulfuric acid, 
98.94% H2SO4, in the proportions of 50 grams per liter of oil. 

Acidity of Color in mm. 

Srdfonic Acids Kerosene as to Match 

Calc. as HiSOt HSO^ Standard 

1.45 0.86 193. 

1.55 1.42 166. 

1.65 1.56 143. 

1.93 1.76 112. 

2.22 2.45 89. 

2.68 2.63 80. 

3.72 3.65 52. 

5.62 4.83 yellow 

4.81 5.91 yellow 

Similar results have been noted by others. Mechanical agitation 
during the sulfuric acid treatment results in slightly lighter colored 
oils than when agitated by air. Generally, in practice, little attention 
is paid to temperature during the sulfuric acid treatment, particularly 
since cooling greatly increases the viscosity of oils of the lubricating 
class, and thus greatly prolongs the time required for the separation of 
the emulsified acid tar or sludge. 

Various mechanical means have been tried in the effort to increase 
the fineness of the emulsified oil particles, and also to decrease the 
time required for the tar laden acid to settle out. For the latter pur- 
pose centrifugal separation, and the addition of fine sand, infusorial 
earth and the like have been tried and while these methods give some- 
what better oils, these methods have not been adopted in large scale 
practice. 

Nitric acid or oxides of nitrogen in the sulfuric acid even in very 
small percentages,"^ e. g., .05 to 0.10 per cent, results in darker colored 
refined oils. Sulfuric acid made by the contact process is, therefore, 
much to be preferred to chamber acid, aside from the fact that the 
former acid is preferable on account of its greater concentration. 

The higher boiling distillates, for example, lubricating oils, require 
very much more acid for refining than kerosene or gasoline. The 
chemical reactions involved are fairly well known in the latter case but 
the chemical character of the substances removed from lubricating 

^"Chem. Ztg. 1911, 3129. For data on the rise in temperature on refining oils of 
different types see Klssling, (7ft«m. Ztg. 29, 1086 (1905) ; Wlschln, Petroleum 3, 1062 

"'Schuiz, Ohem. Rev. Fett u. Ham. Ind. tO, 82 (1913). 



THE PARAFFINS HYDROCARBONS 109 

oils and why they react at all with sulfuric acid is not known. It 
is also possible that the large losses thus incurred are not necessary, 
that the per cent of substances present which are actually objection- 
able, malodorous substances, easily oxidized, color or acid forming 
substances, is really very small, as in the case of the lighter distillates. 
Naturally many other reagents have been tried, including benzensul- 
fonic acid, phosphoric acid, zinc chloride, aluminum chloride and the 
like. The latter, anhydrous aluminum chloride, is the only chemical 
refining agent other than sulfuric acid, which has shown great promise. 
The tar losses in this case are very high, but the quality of the prod- 
ucts produced, gasoline, lubricating oil or white medicinal oil, is re- 
markably fine. 

Anhydrous aluminum chloride polymerizes olefines energetically, 
decomposes sulfur derivatives and naphthenic acids. Color is very 
effectively removed. The oils so refined are extremely stable as regards 
oxidation by air. Interest in this reagent for refining has recently been 
revived by McAfee ^^* and Grey.^'^' In polymerizing amylenes by 
aluminum chloride Aschan obtained a' series of saturated hydrocarbons 
and believed methylcyclobutane, cyclohexane and other cyclic hydro- 
carbons to be present in the lower boiling fractions. 

Liquid sulfur dioxide has been employed to some extent for refining 
kerosene, this method being based upon the marked difference in solu- 
bility of saturated and unsaturated and aromatic hydrocarbons in this 
solvent. With many oils the liquid sulfur dioxide method does not 
yield water white oils, and in such cases, refining with small proportions 
of sulfuric acid must be resorted to in order to get this result. The 
separation of the unsaturated and aromatic hydrocarbons from the 
parafiines is much more efficient at low temperatures, a temperature of 
— 12° being recommended."" While it is a fact that the removal of 
unsaturated and g,romatic hydrocarbons improves the burning quali- 
ties of kerosene, and the Edeleanu process can, therefore, be considered 
as a rational method in this respect, there is nothing to indicate the 
refining value of the liquid sulfur dioxide method as regards naphthenic 
acids, malodorous sulfur compounds and the like. The method seems 
to be predicated mainly on the idea that unsaturated hydrocarbons 
should be removed from oils to be used as motor fuel, gasoline or 
naphtha solvents, lubricating oils, etc. On the other hand, there is con- 

■■"U. S. Pat. 1,277,328; 1,277,092; 1,277,329. 

'"U. S. Pat. 1,193,540; 1,193,541 (essentiaUy cracking processes). Cobb, U. S. 
Pat. 1,322,878; 1,322,762. 

"° See section on Physical Properties ; Solubility. 



110 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

siderable evidence indicating that it is possible to refine motor fuel and 
lubricating oils to a satisfactory degree without the large losses at- 
tendant upon the removal of the unsaturated hydrocarbons and aro- 
matic hydrocarbons. That benzene can be satisfactorily used as a mo- 
tor fuel, particularly when mixed with gasoline, or gasoline and alcohol 
is now generally recognized. It is probable that the unsaturated 
hydrocarbons themselves, as removed from pyrolytic process motor 
fuel by the Edeleanu method, can be employed successfully in internal 
combustion engines, provided the resin forming conjugated diolefines, 
present only in very small proportions, be removed by fuller's earth 
according to Hall's refining process, or an equivalent method.^®^ It is 
also probable that transformer oils and oils intended for the lubricat- 
ing of air compressors and internal combustion engines should be free 
from unsaturated hydrocarbons on account of the general tendency of 
such hydrocarbons to be readily oxidized by air. But it is possible 
that highly unsaturated but otherwise refined oils would prove satis- 
factory even in these instances. Considerable research needs to be 
carried out in order to determine precisely in what refining for par- 
ticular purposes should consist, and to develop industrially feasible 
methods of refining, which would remove the objectionable constituents 
with little or no loss of the valuable hydrocarbons. 

Ml The writer has seen test runs of an automobile engine in which pure turpen- 
tine was used as the fuel, without abnormal deposition of carbon, with excellent 
thermal efficiency and without carburetor difficulties. A great many of our ideas as to 
what the characteristics of good motor fuel should be have apparently been derived 
from the commercial salesman, who bad a certain article to sell. 



Chapter IV. The Ethylene Bond 

Theory of the Ethylene Bond and Cyclic Structures 

It is probably not exaggerating the relative importance of the mat- 
ter to state that the chemical behavior and physical properties of the 
unsaturated olefine, or ethylene group, is fully as important as the 
well differentiated properties of condensed or benzenoid structures. 
The chemical properties of the ethylene structure cannot properly be 
indicated by a few so-called type reactions and in the following dis- 
cussion it will be pointed out that all of the important chemical prop- 
erties of this group may be greatly influenced by structural configura- 
tion and proximity of other groups or substituents. The properties of 
this group as displayed in the enol form of tautomeric compounds is 
not discussed at length as this material has been well presented else- 
where and it is moreover not strictly germane to the subject of hydro- 
carbon chemistry. 

It will be of interest to examine the current theories regarding the 
atomic structure of such a linking. That the group >C =; C< is rela- 
tively unstable, or under stress (Baeyer), is indicated by a wealth of 
experimental evidence. Our conceptions or theories of such carbon 
"linkings" have been greatly advanced by the general hypotheses re- 
cently published by Lewis and by Langmuir. First, Lewis ^ pointed 
out that "a study of the mathematical theory of the electron leads, I 
believe (irresistibly to the conclusion that Coulomb's law of inverse 
squares must fail at small distances." Like Parson,^ Lewis believed 
that the most stable condition for the atomic shell is the one in which 
eight electrons are held at the corners of a cube. As regards the carbon 
atom Lewis may again be quoted. "Assuming now, at least in such 
very small atoms as that of carbon, that each pair of electrons has a 
tendency to be drawn together, perhaps by magnetic force if the mag- 
netic theory (of Parson) is correct, or perhaps by other forces which 
become appreciable at small distances, to occupy positions indicated 
by the dotted circles, we then have a model which is admirably suited 
to portray all of the characteristics of the carbon atom. With the 

'J. Am. Ohem. Boo. S8, 773 (1916). 
'Smithsonian Inst. Public 65, 1915, p. 2371. 

Ill 



112 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

cubical structure it is not only impossible to represent the triple bond, 
but also to explain the phenomena of free mobility about a single bond 
which must always be assumed in stereochemistry. On the other hand, 
the group of eight electrons in which the pairs are symmetrically placed 
about the center gives identically the model of the tetrahedral car- 
bon atom which has been of such utility throughout the whole of or- 
ganic chemistry." Then two such tetrahedra, attached by one, two or 
three corners of each, represent respectively the single, double and 
triple bond. In the first case, one pair of electrons is held in common 
by the two atoms; in the second case two such pairs and in the third 
case, three such pairs. 

According to Lewis, the triple bond represents the highest possible 
degree of imion between two atoms. Like a double bond it may break 
one bond producing two odd carbon atoms, but it may also break in a 
way in which the double bond cannot, i. e., to leave a single bond and 
two carbon atoms (bivalent), each of which has a pair of electrons 
which is not bound to any other atom. The three resulting structures, 
in the case of acetylene, may be represented as follows, H : C : : : C : H, 
H : C : : C : H and H : C : C : H. In addition we have a form cor- 
responding to Nef's acetylidene and such forms as may exist in highly 
polar media, such as the acetylidene ion : C : : : C : H. 

The instability of multiple bonds, as well as the general phenome- 
non of ring formation in organic compounds, is admirably interpreted 
by the Strain Theory of Baeyer. This theory may, however, be put 
into a far more general form if we make the simple assumption that 
all atomic kernels repel one another, and that molecules are held to- 
gether only by the pairs of electrons which are held jointly by the 
component atoms. Thus two carbon atoms with a single bond strive 
to keep their kernels as far apart as possible, and this condition is met 
when the adjoining corners of the two tetrahedra lie in the line joining 
the centers of the tetrahedra. This is an essential element of Baeyer's 
Theory of stress in cyclic structures. When a single bond changes to a 
multiple bond and the two atomic shells have two pairs of electrons 
in common, the kernels are forced nearer together and the mutual re- 
pulsion of these kernels greatly weakens the constraints at the points 
of junction. This diminution in constraint, therefore, produces a re- 
markable effect in increasing the mobility of the electrons. In any 
part of a carbon chain where a number of consecutive atoms are dou- 
bly bound there is in that whole portion of the molecule an extraor- 



THE ETHYLENE BOND 113 

dinary reactivity and freedom of rearrangement. This freedom usu- 
ally terminates at that point in the chain where an atom has only 
single bonds and in which, therefore, the electrons are held by more 
rigid constraints, although it must be observed that an increased mo- 
bility of electrons {and therefore increased polarity) in one part of 
the molecule always produces some increase in mobility in the neigh- 
boring parts. 

"There is much chemical evidence, especially in the field of stereo- 
chemistry, that the primary valence forces between atoms act in di- 
rections nearly fixed with respect to each other." ^ 

"Further evidence for the stationary electrons has been obtained 
by Hull, who finds that the intensities of the lines in the X-ray spectra 
of crystals are best accounted for on the theory that the electrons 
occupy definite positions in the crystal lattice." 

According to Langmuir's postulates carbon, atomic number six, has 
normally six electrons, two situated close to the nucleus or kernel as 
in helium, and the "four electrons in the second shell tend to arrange 
themselves at the corners of a tetrahedron for in this way they can get 
as far apart as possible." Langmuir regards the electrons in the atoms 
"as able to move from their normal positions under the influence of 
magnetic and electrostatic forces." 

It should be borne in mind when reviewing the chemical properties 
of the ethylene bond that there is no set of reactions which infallibly 
characterize this group as distinguished from other unsaturated types, 
particularly cyclopropane derivatives. This is in accord with Baeyer's 
strain theory and it is probably worth while to emphasize these rela- 
tionships and briefly review the theory. 

Baeyer was much impressed by the explosibility of the polyacety- 
lene compounds and endeavored to visualize the manner in which en- 
ergy could be absorbed in the formation of the acetylene bond, this 
energy being released as heat when such a substance explodes. From 
the generalization of van't Hoff and LeBel, Baeyer inferred that "the 
four valences of the carbon atom act in directions which connect the 
center of the sphere with the comers of a (inscribed) tetrahedron, and 
which form an angle of 109° 28' with each other. The direction of the 
attraction (or valence) can undergo a bending or distortion, which re- 
sults in a tension (Spannung) proportional to the amount of this bend- 
ing." * 

• Langmuir, J. Am. Ohem. Soc. il, 686 (1919) . 
'Ber. 18, 2269 (1885). 



114 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

"Ethylene is the simplest methylene ring, as it may be regarded as 
dimethylene." In order to bend two of these hypothetical lines of 
valence direction to parallel positions would require that each of the 
pair be deviated one-half 109° 28' or 54° 44' from their normal direc- 
tions. In the same way the supposed deviations from the normal va- 
lence direction may be calculated for cyclopropane, cyclobutane, and 
so on. Ring structures containing more than five carbon atoms would 
require a spreading or widening of the normal angle, the angles of devi- 
ation of the simpler cyclic carbon structures being as follows: 



1 
CH, 




CH2- 
CH,- 


-CH, 


CH, — CH, 

1 >CK 

CH, — CH, 


- 54° 44' 


+ 24° 44' 


+ 9° 


44' 


0° + 44' 




C 

/ \ 

H,C CH^ 

H^C CH, 

V 

— 5° 16' 




C 
/ \ 






H,C 

C 
H 


CH, 

— C 
2 H2 
9° 33' 




cyclooctane, - 
cyclononane, - 


— 12° 46' 
- 15° 16' 





Cyclopropane and its derivatives are generally not as reactive as 
ethylene but the ring is broken by bromine, hydriodic acid, and by 
hydrogen in contact with nickel at 80°. Cyclopropane is not oxidized 
by cold dilute permanganate. Cyclobutane is not reacted upon by 
bromine, concentrated hydroiodic acid or dilute permanganate solution. 
The ring is opened by hydrogen in the presence of nickel, forming 
butane at high temperature but is stable at 100°. The stability of 
cyclopropane and cyclobutane rings toward oxidizing agents, t)romine, 
halogen acids, dilute sulfuric acid and the like is very greatly modified 
by substituent groups, just as the chemical behavior of the ethylenes 
is altered by different groups. Thus 1 . 2-dimethylcyclopropane is acted 
upon by 1% permanganate^ and the hydrocarbon 1, 1, 2-trimethyl 

■ZeUnsky, J. prakt. Chem. 8i, II, 543 (1911). 



THE ETHYLENE BOND 115 

cyclopropane combines with concentrated hydrochloric acid at 100°. 
The derivatives 

CMe, CMe, 



and CH,< I 
H.CH.CHMe, CH.CO„H 



are stable to permanganate solution but the former is hydrogenated 
in contact with nickel at 125° and adds hydrobromic acid very slow- 
ly .° Ethylcyclobutane is extremely stable, being unaffected by per- 
manganate solution, concentrated hydrobromic acid at 100°, concen- 
trated sulfuric acid at 25° and is only reduced by HI at 210°. 

The cyclobutane derivative 1, 1, 3, 3-tetramethyl 2, 4-diethylcyclo- 
butane 

Me^C CHC,H, 



i 



C2H5CH — CMe, 

is also remarkable for its stability, its chemical behavior resembling 
that of a saturated hydrocarbon of great inertness.'' The acid chloride 

>CHC0C1 is sufficiently stable to anhydrous aluminum chloride 



A 



and hydrogen chloride * to react normally in the Friedel and Crafts 

CH, 

synthesis to give good yields of the ketone C6H50C.CH< | . This 

fact is somewhat remarkable in view of the ease with which the cyclo- 
propane ring in carane and sabinene and the cyclobutane ring in 
the pinenes is ruptured by halogen acids, by bromine and by di- 
lute mineral acids. Wallach ^ has noted that the ketonic acid 

CH.COCH3 CH.CO,H 

CH2< I is very unstable, but the acid CH2< | 

C — CH,CO,H C — CH,CO,H 

I I 

C3H, C3H, 

is very stable. 

Although Baeyer's theory needs revision in the light of our present 
knowledge and theories of valence and atomic structure, it has passed 

•KlBhner, J. Chem. Soc. Aha. 1913, I, 1163. 
'Wedekind & Miller, Ber. U, 3285 (1911). 
•Kishner, J. Bust. Phys.-Chem. 80c. iS, 1163 (1911). 
•Ann. 369, 82 (1908) ; 388, 49 (1912). 



116 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

the test of usefulness and been of very great value. Experience is gen- 
erally in accord with the theory and the yields in analogous reactions 
of synthesis indicate that in the cyclopropane, cyclobutane, cyclopen- 
tane and cyclohexane series, derivatives of cyclopropane are produced 
with the greatest difi&culty or poorest yields, and that while cyclobu- 
tane and cyclohexane derivatives are much more easily obtained, the 
tendency to form cyclopentane derivatives is so pronounced that quan- 
titative yields are frequently produced and, in fact, cyclopentane de- 
rivatives sometimes result during reactions which might be expected 
to yield other ring structures. As regards the relative influence of 
different substituent groups in such syntheses Perkin " states that it 
is clear that a useful generalization cannot be formulated until a much 
larger number of cyclic carboxylic acids and other derivatives have 
been prepared and investigated. J. von Braun" states that 1,4 di- 
halogen alkyls and sodium malonic ester give good yields of cyclo- 
pentane derivatives but the same reaction applied to the synthesis of 
cyclohexane and cycloheptane compounds, from the 1, 5 and 1, 6 di- 
halogen derivatives, respectively, give very poor yields. The ease with 
which cyclohexanones are converted to cyclopentanones has been 
noted by Wallach " and the four carbon ring in cyclobutyldiethyl- 
carbinol, on decomposition with loss of water, forms the five carbon 
ring 1, 2-diethylcyclopentene." However, a very large number of re- 
arrangements have been observed in which change to a system, less 
stable so far as the.Baeyer theory and the number of carbon atoms in 
the ring is concerned, is brought about.^* 

J. F. Thorpe '■^ and his assistants reasoned that if two valences of 
a given carbon atom are under strain due to ring formation, the di- 
rections of the two remaining valences would be affected, for example, 
the angle formed by two side chains attached to a carbon atom in a 
ring such as cyclohexane, would be bent from the normal 109° 28' re- 
quired by Baeyer's theory. In the case of cyclohexane these two side 
chains may be closer together than in a corresponding compound hav- 
ing an open chain structure. Their results are an interesting confirma- 
tion of the theory. Thorpe has compared the relative stability of 
the cyclopropane derivatives formed by the elimination of hydrogen 

"Cf. Goldsworthy & Perkin, J. Chem. Soc. lOS, 2665 (19141 

"Ber. J,6, 1782 (1913). \'->"--±). 

^J. Chem. Soc. Abs. 1916, I, 487. 

" Kishner, Chem. Zentr. ISli, I, 1001. 

" See chapter od Rearrangements. 

"Beesley, Ingold & Thorpe, J. Chem. Soc. 107, 1080 (1915). 



THE ETHYLENE BOND 117 

bromide from the monobromo derivatives of cyclohexane-1 . 1-diacetic 
acid and |3p-dimethylglutaric acid, as follows, 

CH2CH2 CHBr.CO^H 

CH,< >C< > 

CH.CH^ CH.CO^H. 

CH^CH, CH.CO2H 

CH,< >C< I 

CH2CH2 CH.CO.H 

CH3 CHBr.CO.H. CH3 CH.CO.H 

>C< > >C< I 

CH3 CH,CO,H. CH3 CH.CO^H. 

Both of the resulting acids are remarkably stable towards boiling acid 
permanganate solution but the chief difference observed was in their 
behavior to concentrated hydrochloric acid in sealed tubes at 240° 
under which conditions the spiro acid, from cyclohexanediacetic acid, 
is unaffected but the other, trans-caronic acid, is completely changed 
to terebic acid, with rupture of the ring. 

The thermal measurements of Stohmann and Kleber are not in 
good agreement with Baeyer's theory. According to their work, the 
quantities of heat absorbed in the formation of similarly constituted 
compounds containing the cyclopropane, cyclobutane, cyclopentane 
and cyclohexane rings by the removal of two atoms of hydrogen from 
the corresponding open-chain substances, are as follows: 

Ring Cz a C, Ca 

Angle of strain (Baeyer) 24.7° 9.7° 0.7° 5.3° 

Heat absorbed, calories 38.1 42.6 16.1 14.3 

Ingold ^° has suggested that these calculated angles of strain may 
not be correct and that the normal tetrahedral angle of Baeyer 
(2 tan"^ y 2 = 109.5°) may be modified somewhat according to the 
volume occupied by the four attached atoms or groups. (The distor- 
tion of the valency direction, as suggested by Ingold, has nothing in 
common with the theories of Guye and Brown, which refer to the ef- 
fect of the size of the substituent radicles upon the asymmetry of the 
molecule as measured by the molecular optical activity.) 

Ingold suggests that "the tetrahedron representing a carbon atom 
is approximately regular only when the carbon atom is attached to 
four atoms of a similar kind," for example, to four carbon atoms, 

"J. Chem. Soc. US, 306 (1921). 



118 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

(A). However in cyclopropane, cyclobutane and the like, each carbon 
atom is attached to two hydrogen atoms and two carbon atoms, (B). 

C C H C 

\ / \ / 

c c 

/ \ / \ 

C C H C 

(A) (B) 

Since the hydrogen atom occupies a much smaller volume than the car- 
bon atom, it is accordingly possible that in the >CH2 group the two 
carbon atoms attached to the central one occupy more of the sur- 
rounding space than do the hydrogen atoms. If this is so, the angle be- 
tween the carbon-to-carbon valencies of a polymethylene chain will 
not be 109.5°, as hitherto supposed, but will be some angle greater 
than this." Using Traubes values for the atomic volumes of carbon 
and hydrogen, Ingold calculates that this volume factor causes a 
change in the angles between each pair of carbon-to-carbon valencies 
in a polymethylene chain and that this angle may be nearly 6° greater 
than has hitherto been supposed. Employing this new angle 115.3° 
instead of 109.5°, Ingold calculates "by how much" the terminal car- 
bon atoms of C3, C4, C5, and Cg rings must approach one another and 
obtains values more nearly in accord with the thermal results of Stoh- 
mann and Kleber. 

The above stereo-chemical considerations afford an explanation of 
the effect of the gem-dimethyl group in promoting certain reactions 
and in other cases greatly increasing the stability of the substance. 
Thus, aa-dimethylbutane -apy-tricarboxylic acid is smoothly con- 
verted into the cyclopentanone derivative, on heating its sodium salt 
with acetic anhydride, but this change has not been observed with 
adipic acids which do not contain a grem-dimethyl group. The 
(0113)2 C< group stabilizes certain lactones, for example, P|3-dimeth- 
ylglutaric anhydride may be boiled in water for hours without change, 
and a|3p-trimethylglutaric anhydride may be crystallized from hot 
water in crystals containing water of crystallization, but ordinary glu- 
taric anhydride is easily decomposed by water. 

Hiickel " regards the heat of combustion of CHj as different in 
each polymethylene ring and points out that if the heats of combustion 
of these hydrocarbons are divided by the number of CHj groups con- 

"Ber. BSB, 1277 (1920). 



THE ETHYLENE BOND 119 

tained in the hydrocarbon concerned, then values are obtained which 
are much better in accord with Baeyer's theory than the older com- 
parisons of Stohmann. In this way, the values for CHj in ethylene, 
cyclopropane, cyclobutane, cyclopentane and cyclohexane are calcu- 
lated to be 170, 168.5, 165.5, 159, 158 calories, respectively. 

In view of the fact that the chemical behavior of the cyclopropane 
group reveals a condition of unsaturation or strain (Baeyer) it is not 
surprising that ring closing in this case influences the physical proper- 
ties of substances containing this ring complex. This will be discussed 
more fully in the section dealing with physical properties and constitu- 
tion but it may be noted here that one of the most significant and use- 
ful properties, refractivity, is affected by the formation of the 3 carbon 
ring to almost the same degree as in the case of the ethylene bond, 
and that when the cyclopropane group occurs in a conjugated position 
to an ethylene bond substantially the same degree of exaltation is ob- 
served as is noticed in the case of two conjugated ethylene bonds. 



Chemical Properties of Unsaturated Substances of the Ethylene 

Type. 

Unsaturated substances of the ethylene type, e. g., substances con- 
taining one or more so-called olefine groups, are capable of a series 
of reactions which are very widely applicable to nearly all substances 
containing such an unsaturated group and which have come to be re- 
garded as characteristic reactions of this type of unsaturation. These 
reactions are best exemplified by the addition of ozone, of halogens, 
particularly bromine, oxidation by potassium permanganate solution 
to the corresponding glycols, addition of nitrosyl chloride and oxides 
of nitrogen. Other reactions less widely applicable will be noted be- 
low. All of these reactions involve rupture of one of the ethylenic 
linkings or, in other words, one of the primary valences. In addition 
to these reactions, it has been noted that substituted ethylenes are 
capable of forming a large number of so-called molecular compounds 
with other substances. In these compounds the double bond is not 
broken and the formation of these molecular compounds is due to what 
is termed, for lack of a better name, "residual valence," "latent affin- 
ity," "secondary valence," and similar terms. It should be pointed out, 
however, that the ability to form such molecular compounds is by no 
means limited to unsaturated substances of the ethylene type. 



120 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Well crystallized compounds of p-tetrabromotetraphenylethylene 
with acetone, ether, methylethyl ketone, carbon tetrachloride, ethyl 
acetate and benzene, have been described. These compounds are easily 
decomposed to the original constituent substances. Norris ^^ has sub- 
mitted the following hypothesis in regard to substances of this kind. 

(1). The molecular compound is formed as a result of the com- 
ing into play of latent affinities residing in an atom in each of the 
constituents of the compound. 

(2). All atoms possess these latent affinities. If an atom in a 
compound reacts with difficulty when the latter is brought into con- 
tact with other substances, it is evident that a large part of its energy 
has been expended and but a little of it remains to take part in re- 
action. On the other hand, if the atom enters into reaction readily with 
other substances, it is e^'ident that it still possesses available energy. 
It is probable, therefore, that such active atoms might be able to unite 
with atoms of a similar nature (with respect to residual energy) and 
form molecular compounds. A study of the literature confirms the 
view that compounds containing unusually active elements or groups 
form well characterized molecular compounds. 

(3). Substances which contain inactive double bonds may form 
molecular compounds. In most cases direct addition of atoms or 
groups at the double bond leads to the formation of ordinary saturated 
compounds. So-called unsaturated compounds are known, however, 
in which the unsaturation is so slight that they will not unite with such 
an active element as bromine. The chemical affinity latent in the dou- 
ble bond is so small that it cannot hold in combination other atoms 
or groups linked to it by primary valence bonds. Many such com- 
pounds form well characterized molecular compounds. In other words, 
the available energy of the double bond is not enough to neutralize 
the energy of atoms and form a true valence bond, but is suf- 
ficient to interact with a similar small amount of energy residing in 
another compound. For example, p-tetrabromotetraphenylethylene 
(BrCoIl4)2C = C(C6H^Br)2 will not react with bromine, as shown by 
Bauer,^° but it does form a series of molecular compounds, as noted 
above. [There is apparently no way of determining whether the resid- 
ual energy which makes these combinations possible in this case is 
really inherent in the double bond or in the bromine atom. The latter 
possibility suggests itself in view of the fact that tetraphenylethylene 

"J. Am. Chem. Soc. Ifi, 2086 (1920). 

»Ser. m, 3317 (1904) ; Hinrlchsen, Awn. sse, 223 (1904). 



THE ETHYLENE BOND 



121 



dichloride (CeH5)2CCl.CCl(CeHg)2 also forms molecular compounds. 
B. T. B.] 

The hypothesis that unsaturated hydrocarbons are able to unite 
with acids, by virtue of "free partial valences," to form salt-like sub- 
stances was put forward and subsequently rejected by Baeyer but 
Kehrmann and Effront ^° have revived the hypothesis to account for 
the formation of two series of salts by the triphenyl methane dyes, and 
for the behavior of certain unsaturated ketones towards acids. For ex- 
ample, distyryl ketone gives mono- and di-acid compounds, lemon- 
yellow and orange-red respectively, from which it seems necessary to 
assume that combination can occur at one double bond in addition 
to the oxygen atom. 

The reaction of bromine with styrene and substituted styrenes 
shows that replacement of one of the methylenic hydrogen atoms by 
an aryl group increases the reactivity to bromine slightly and this 
difference is further accentuated by substituting both hydrogen atoms 
by alkyl groups. The introduction of one halogen atom decreases the 
reactivity toward bromine but the effect of a CN group is even more 
marked, the effect of the CN and carboxyl group being of about the 
same order.^^ 

Double compoimds of ethylene and aluminum chloride have been 
isolated but energetic polymerization occurs with most olefines. Very 
little work has been done with the Friedel and Craft reaction as ap- 
plied to non-benzenoid hydrocarbons. Darzens '^ found that acetyl 
chloride did not react with cyclohexarie in the presence of aluminum 
chloride but with cyclohexene the saturated chloro ketone was formed. 



/^ 



H 



CI 



/ 



\ / 



+ CH3COC1 AICI3 



^ ^— C0.CH3 



\ / 



stannic chloride is a most efScient catalyst for this reaction. Norris 
and Couch "^ have recently noted that ethylene reacts with benzoyl 

'"Ber. 51,, 417 (1921). 

"Reich et al. Helv. Chim. Acta, i, 242 (1921). 

'^ Compt. rend. 150, 707 (1910J. The chloride noted above may be decomposed 

by alkali to give the unsaturated Itetone.— HC=C< ' 

"J. Am. Chem. Soc. ),t, 2330 (1920). 



122 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

chloride in the presence of AICI3 apparently in a different manner, to 
give phenyl vinyl ketone CeHjCO . CH = CHj. The chloride, 
CeHjCO . CHgCHjCl, corresponding to Darzen's product, was not ob- 
served. 

There is no subject in organic chemistry to which it is more diffi- 
cult to give accurate expression than the modification of the chemical 
behavior of certain groups or substituent atoms by other groups «or 
atoms in the same molecule. As pointed out by Bauer the substitu- 
tion in ethylene of strongly negative groups diminishes the ability of 
the substance to react with bromine.^* On the other hand, the substi- 
tution of halogens or the phenyl group very markedly increases the 
reactivity of the ethylene group in certain other respects. Thus ethyl- 
ene is polymerized only at high temperatures and pressures and in 
the presence of catalysts such as alumina or iron, or in the presence of 
very reactive substances such as anhydrous aluminum chloride or zinc 
chloride. On the other hand, styrene CeH^CH = CHj, vinyl bromide, 
CH2 = CHBr, and vinyl chloride polymerize on standing at ordinary 
temperatures, and rapidly under the influence of light. The enhanced 
reactivity of the hydrogen atoms in styrene is also indicated by the 
fact that this substance yields the nitro derivative CeHjCH = CHNO2 
when treated with nitric acid.^° 

That the double bond greatly influences the reactivity of the sub- 
stituent halogen atoms is also well known. Thus vinyl bromide and 
vinyl chloride are remarkably stable to alkalies and in many of their 
reactions closely resemble chloro-benzene and bromobenzene. Ad- 
vantage is taken of this unusual stability of chlorine substituted ethyl- 
enes, with respect to reactivity of the chlorine, in utilizing them as 
commercial solvents. For example, trichloroethylene, CHCl = CClg, 
is not appreciably hydrolyzed by hot water and is practically not af- 
fected by iron or copper and is therefore admirably adapted for use 
as a solvent in industrial apparatus made of these metals.^^ This sta- 
bility of halogen derivatives of ethylene is also indicated by the com- 
mercial methods of manufacturing trichloroethylene, e. g., treating 
tetrachloroethane with alkali or passing over thorium oxide at 390°." 
On treating trichlorocyclohexane with alcoholic caustic potash the prin- 

'iPerkin has called attention to the fact that the stability of cyclopropane and 
cyclobutane derivatives is variable within wide limits depending upon the character 
of the substituent groups. 

== Recent work of Wieland, Ber. 5), 201 (1920), shows that ethylene reacts with 
a mixture of nitric and sulfuric acids (20% oleum) to give a mixture of ethylene 
dinitrate and B-nitro-ethyl nitrate. 

» Gowing-Scopes, J. Hoc. Chem. Ind. SS, 160 (1914) ; Crudes, Ohem. Al)s. 1917, 544. 

=> German Pat. 171,900; 206,854 (1906) ; 274,782 (1914). 



THE ETHYLENE BOND 123 

cipal product is chlorodihydrobenzene, CeHjCl, the last chlorine atom 
being stabilized by the adjacent double bonds. 

WohP® has shown that when tetramethylethylene (CH3)2C = 
0(0113)2 is treated with n-bromoacetamide, primary addition occurs 
through subsidiary valences of the bromoacetamide and of one or both 
of the unsaturated carbon atoms of the olefine. Acetamide is then 
formed, the bromine atom taking the place of the hydrogen re- 
moved to form acetamide, the final products being acetamide and 
(CH3)20 = O.OHs.OH2Br. 

Free bromine reacts energetically with the unsaturated hydro- 
carbons and therefore solvents are usually employed in such re- 
actions, e. g., carbon bisulfide, carbon tetrachloride, glacial acetic 
acid and, less generally, alcohol or ether. The reaction is rapid and 
standardized solutions of bromine in acetic acid or carbon tetrachloride 
can often be used to titrate such hydrocarbons and determine the de- 
gree of unsaturation.^^ However, substitution of hydrogen sometimes 
takes place and the well-known analytical methods of Hiibl, Hanus 
and Wijs, which are of such value with unsaturated fatty oils, cannot 
be relied upon to give correct results in the case of the terpenes and 
the higher ethylene homologues derived from petroleum.^" Bromine 
addition products are sometimes crystalline solids and thu^ serve for 
purposes of identification, as in the case of butadiene, the tetrabro- 
mide '^ melting at 118°, and limonene and dipentene whose tetrabro- 
mides melt at 104°-105° and 124° respectively. The addition of halo- 
gen acids has already been referred to in the section dealing with the 
preparation of halogen derivatives. The addition of bromine is made 
use of in the analytical chemistry of rubber and a chlorinated rub- 
ber ^^ has recently appeared on the market. 

Hypochlorous acid reacts with ethylene bonds more readily than 
concentrated sulfuric acid, forming chlorohydrins. Thus ethylene re- 
acts readily with cold dilute solutions of hypochlorous acid, and also 
other substances, which are inert or react only very slowly with 
sulfuric acid at ordinary temperatures, yield chlorohydrins, for ex- 
ample, cinnamic acid, allyl bromide, maleic acid and the higher ethyl- 
ene homologues. Solutions of chlorine water give nearly theoretical 

"Ber. S2. B. 51 (1919). 

^Cf. V. Soden and Zeitschel, Ber. S6, 266 (1903). 

" For description and details for carrying out these determinations see Leach, 
"Pood Analysis," pp. 488-530, 4th Ed. Lewkowitsch, "Oils, Fats and Waxes," Vol. I, 
p. 393. See Faragher and Garner, J. Ind. & Eng. Ohem. IS, 1044 (1921). 

" A low melting modification melting at 37.5° Is also known. 

" The product carries the trade name "Duroprene" and appears to have value as 
u. varnish film resistant to corrosive vapors or acids. 



124 CtlEMISTRY OF ThS NON-BENZENOID HYDROCARBONS 

yields of ethylene chlorohydrin but other unsaturated hydrocarbons 
that react energetically with chlorine also yield dichlorides. In such 
cases better yields of chlorohydrins are obtained by employing dilute 
solutions of alkali hypochlorite which yield free hypochlorous acid by 
hydrolysis and contain no free chlorine. Thus Walker ^•'' employs so- 
dium hypochlorite in the presence of sodium bicarbonate to prepare 
amylene chlorohydrins (carbonic acid is a stronger acid from the ioni- 
zation standpoint than hypochlorous acid) . The chlorohydrins of ethyl- 
ene, propylene, butylene,^* amylenes,^' and hexylenes are best known. 
Propylene and hypochlorous acid yields a mixture of the two isomers 
CH3CHOH.CH2CI and CH3CHCI.CH2OH. By the action of hydro- 
gen chloride on propylene oxide both isomeric chlorohydrins are ob- 
tained as has been shown by an examination of their rate of hydroly- 
sis.^* Isobutylene and the amylenes also yield a mixture of isomeric 
chlorohydrins.^^ All of these simpler chlorohydrins yield alkylene 
oxides when treated with concentrated caustic alkali, and slow hydroly- 
sis in the presence of sodium bicarbonate gives good yields of the gly- 
cols. The utilization of the ethylene and propylene in oil gas and 
petroleum still gases in this manner has recently been attempted on 
an industrial scale. 

On heating the simpler chlorohydrins with water, aldehydes, or ke- 
tones are formed. Thus 2-chloro-3-hydroxybutane is completely con- 
verted to methyl ethyl ketone in 3 hours at 120°. Propylene chloro- 
hydrins give acetone and propionic aldehyde and the chlorohydrin of 
trimethyl ethylene similarly yields methyl isopropyl ketone.^* 

The reaction of hypochlorous acid with other unsaturated sub- 
stances, for example, the terpenes, unsaturated petroleum oils and 
fatty oils has been very little studied. Pinene yields a mixture of 
products,^" among which is pinol oxide, CioHigOa, which oxide, unlike 
cineol, is very easily hydrolyzed by dilute acids to a glycol. The di- 
chlorohydrine CioHisOjClj is also formed, the bridged ring being 
opened. The substance cis-pinolglycol-2-chlorohydrin, C10H17O2CI, is 
very stable to aqueous alkalies as is also the chlorohydrin obtained 
from camphene,*" CioHioHOCl. Large proportions of chlorination 

"» V. S. Pat. 972,952 ; 972,954. 

"Henry, Bull. Acad. roy. Belg. 1906, 523; Compt. rend. i//3, 493; Krassuski, Chem. 
Zentr. 1901, I, 995. 

»» Carius, Awn. 126, 199 (1863) ; Umnowa, Chem. Zentr. 1911, I, 1278. 

"•Smith, Z. pliysik, Cliem. 93, 59 (1918) ; Cf. Michael, Ber. S9, 2785 (1906). 

" Henry, loc. cit. 

" Krassuski, Chem. Zentr. 1S02, II, 20. 

" Wagner & Slawinski, Ber. 32, 2064 ; Henderson & Marsh, J. Ohem. Soc. 119, 1492 
(1921). 

" Slawinski, Chem. Zentr. 1906, I, 137. 



THE ETHYLENE BOND 125 

products are also formed in the case of camphene and this together 
with the fact that these chlorohydrins are relatively stable and are 
not easily converted to glycols perhaps accounts for the fact that 
hyppchlorous acid has not become an instrument of research in this 
series. 

The influence of constitution and the presence of substituent atoms 
or groups on the addition of water and behavior toward acids, or 
their aqueous solutions, is very pronounced. A few substances possess- 
ing double bonds, carbon to carbon, react with water energetically, 
for example, ketene HjC = CO and carbon suboxide, OC = C = CO, 
whose behavior toward water resembles that of acid anhydrides. The 
unsaturated hydrocarbons themselves, however, do not react with wa- 
ter directly although Engelder observed indications that the dehydra- 
tion of alcohol to ethylene and water in the presence of alumina or 
kaolin, is reversible.*^ 

Aqueous solutions of organic acids, particularly formic and oxalic 
acids, effect hydration in certain instances, for example 

(CH3) ^C = CH . CH3 + H2O ^ (CH3) 2 . C . OH . CH2CH3 

but the method is by no means general and is of no preparative value. 
The formation of esters of organic acids and olefines on heating or in 
the presence of other substances, such as zinc chloride or sulfuric acid, 
often gives excellent yields. Heptylene and acetic acid heated in an 
autoclave or sealed tube to 300° yields heptyl acetate.^^ Amylene and 
acetic acid react at ordinary temperatures in the presence of zinc chlo- 
ride, but the yield is greatly diminished by the formation of polymers. 

(CH3),C = CH.CH3 -f CHjCO^H 

(CH3),C(03C.CH3).CH,CH3 

polymers 



+ [ZnCl.j 



In most cases, better results are obtained by the method of Ber- 
tram and Walbaum, in which process the define is dissolved in an 
excess of acetic acid and a relatively very small quantity of sulfuric 
acid is added.*' The presence of water greatly retards the acetylation. 
This reaction does not appear to have been applied industrially to the 
acetylation of amylenes or other olefines derived from petroleum, but 

"J. Phys. ahem. U, 676 (1917). 

«Baal and Desgrez, Compt. rend. Ill,, 676 (1892). 

"J. pram. Chem. 1,9, 7 (1894). 



126 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

has been conspicuously successful in the acetylation of camphene to 
bomyl acetate (see Artificial Camphor) . Barbier and Grignard ** rec- 
ommend benzene sulphonic acid instead of sulfuric acid to promote the 
reaction and state that the addition of acetic anhydride to the reaction 
mixture increases the yield of ester. Pinene yields mainly a-terpineol 
acetate. 

Anhydrous oxalic acid and pinene at 120° yield bomyl oxalate and 
formate, which process formed the basis of the first artificial camphor 
process to be attempted on an industrial scale.^^ A large number of 
patents have been issued covering the use of other organic acids in 
making borneol esters. Just as hydrogen chloride containing a little 
moisture yields chiefly dipentene dihydrochloride, concentrated formic 
acid (98-99%) yields mainly terpinyl formate, the bridged ring being 
opened in each case. 

The results of treating unsaturated hydrocarbons with sulfuric 
acid is of considerable interest in connection with the hydration of 
olefines, including the terpenes, and also the refining of petroleum dis- 
tillates. The results include changes of the following nature: re- 
arrangement, or shift in the position of the double bond, polymeriza- 
tion, formation of mono and dialkyl sulfuric esters, and hydration to 
alcohols. 

The tendency of the olefines and substituted ethylenes to react 
with sulfuric acid is distinctly less than their tendency to react with 
bromine. Thus cinnamic and fumaric acids readily yield dibromides 
but are not affected by ordinary concentrated sulfuric acid at 25°. 
The substitution for the hydrogen of ethylene, of groups which impart 
a strongly electronegative character, results in decreased reactivity to 
sulfm-ic acid. Thus cinnamic and fumaric acids are inert, and dichlo- 
roethylene and trichloroethylene are only very slowly acted upon by 
sulfuric acid at ordinary temperatures. Allyl bromide is also more 
stable to sulfuric acid than is propylene. The substitution of groups 
which impart an electropositive character, such as methyl groups, re- 
sults in greatly increased reactivity to sulfuric acid. Isobutene, 
(CH3)2C = CHj is rapidly and completely dissolved by sulfuric acid, 
63% HjSO,, at 17°. Also tetramethylethylene (CH3)2C = C(CH3)2 
reacts readily and completely with 77% acid at ordinary tempera- 
tures. Of the two amylenes 

"Compt. rend, lis, 1425 (1907) ; Bull. Soc. Chim. (4), 5, 512 (1909) 
"Thurlow, y. S. Pat. 698,761; 833,095. Carried out by the Ampere Electro- 
chemical Co. at Niagara Falls, N. Y. r v- 



THE ETHYLENE BOND 127 

CHj C2H5 

>CHCH = CH^ and >C = CH, 

CHg CHg 

the latter dissolves more readily in 66% acid.^° Results very closely 
parallel to these have been noted in the case of the reactions of amyl- 
enes and halogen acids.*' Michael and Brunei believed that in the ali- 
phatic hydrocarbon series the tendency to form alcohols and alkyl sul- 
furic esters decreases with increasing molecular weight, this result ap- 
pearing to be maximum with the amylenes and hexylenes. With in- 
creasing molecular weight polymerization becomes the principal result, 
which result, however, may possibly be preceded by alcohol forma- 
tion.*' The difference in the final results may, therefore, be due in large 
part to the relatively greater stability of the simpler alcohols. Thus un- 

C2H5 CH3 

der the same conditions 3-ethylpentene (2) >C = C< yields 

CaHg H 

72% alcohol and 12% polymers and 2-methylundecene(2) yields 
97% polymers and only a trace of alcohol. Secondary octyl alcohol, 
octane-ol(2), treated with 95% sulfuric acid at 20° gives a yield of 
octene polymers C^JIs^ ^^'^ CjiH^g, increasing with the time of stand- 
ing. A mixture of octene (1) and octene (2) treated with sulfuric 
acid, with cooling, yields chiefly a mixture of the di- and tri-polymers.*" 

In a study of a series of pure unsaturated hydrocarbons Brooks 
and Humphrey noted that the polymers were always more stable to 
sulfuric acid than the parent olefines.^" Kondakow noted a closely 
parallel behavior in the reaction of hydrogen chloride and isobutene 
and its polymers.^^ These results can be expressed in another way, 
e. g., unsaturated hydrocarbons are more highly polymerized, to higher 
boiling, more viscous polymers, by 100% sulfuric acid than by 95% 
acid and the latter will produce a higher degree of polymerization than 
85% acid. 

The mechanism of these changes is very obscure. It has generally 
been assumed that the alcohols, formed by treating unsaturated hydro- 
carbons with sulfuric acid or dilute sulfuric acid, were a result of the 
hydrolysis of the alkyl sulfuric esters first formed, 

"Michael and Brunei, Am. OTiem. J. il, 118 (1909). 

"Bltekow, Ber. 10, 707 (1877) ; Konowalow, B&r. IS, 2395 (1880). 

" Cf . Brooks and Humphrey, J. Am. Chem. 8oc. iO. 822 (1918). 

"RossoUmo, Ber. BT, 626 (1894). 

"J. Am. Chem. Soc. 1,0, 822 (1918). 

"J. prakt. Chem. (2) SJ,, 449 (1896). 



128 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

RCH RCH RCH, 

II +H,SO, > I +H,0 > I +H,g 

RCH RCHOSO,H RCHOH 



Thus ethyl-hydrogen sulfate can be hydrolyzed to give ethyl alco- 
hol but the relative stability of this ester is indicated by the fact that a 
dilute solution of ethyl-sodium sulfate is hydrolyzed in 8 days at 60° 
only to the extent of 16 per cent.''^ The mono or acid sulfuric esters 
of amylenes, hexenes and heptenes are not appreciably hydrolyzed 
on diluting with water at ordinary temperatures and their hydrolysis 
in dilute solution at 100° is very slow. However, when these olefines 
are dissolved in cold sulfuric acid and the clear homogenous acid solu- 
tion diluted with water at 0° the free alcohols are precipitated imme- 
diately in yields sometimes as high as 70 per cent of the theory. Fur- 
ther dilution or complete extraction of the alcohols remaining dissolved 
by means of an immiscible solvent causes no hydrolysis of the alkyl 
sulfuric esters which remain in the aqueous solution. The barium 
salts of these acid esters can be easily isolated by slow evaporation 
without appreciable decomposition. Although these alkyl sulfuric 
esters can be saponified by caustic alkali or hydrolyzed by prolonged 
boiling or steaming, they are not hydrolyzed to alcohols under the 
conditions which obtain in the separation of the alcohols from these 
sulfuric acid mixtures. Also the highest yields of alcohol are obtained 
when employing sulfuric apid containing water, greater yields of alcohol 
being obtained with 85 per cent acid than with 95 per cent or 100 per 
cent acid, or with benzene sulfuric acid. 

To account for these facts the theory has been proposed ^' that the 
addition of water to olefines with formation of free alcohols, in cold 
solutions, is due to reaction with the monohydrate of sulfuric acid 
HaSO^.HaO, or higher hydrates. The monohydrate, or orthosulfuric 
acid, is usually regarded as having the constitution 

HO OH 

\ / 

s = o 

/ \ 

HO OH 

'^Linhart, Am. J. Sci. 35, 283 (1913) ; Evans an<3 Albertson mention that In the 
Bystem C2HoOH+H2SOi±5C2HbH.SOi + HjO the dilution ot the mixture by titration does 
not cause appreciable hydrolysis, [j. Am. Chem. Soc. S9, 456 (1917).] 

" Brooks and Humphrey, loc. cit. 



THE ETHYLENE BOND 



129 



It is practically certain that esters of this acid would have quite differ- 
ent degrees of stability and quite different rates of hydrolysis than the 
known relatively stable esters of ordinary sulfuric acid. 

The hydration of pinene to terpin hydrate CioHi8(OH)2.H20 by 
dilute aqueous acids has long been known. Heating terpin hydrate 
with dilute sulfuric or phosphoric acids results in partial decomposition 
to terpineol, which process is carried out industrially. Wallach ^* 
has pointed out the marked effect of differences of constitution on the 
rate of hydration of five menthenols. 



CH, 



CH, 



CH, 



'\ 



OH 



N 



OH 



\ / \ 

I n 



\/ 



CH, 



/\. 



CH, 



\/ 



/\ 




CH, 



/ 



\/ 



IV 

\/ 



CH, 



.K 



\ 



/\ 



OH 



/\ 



OH 



\ 



/\ 



The menthenols I and II react readily with 5% sulfuric acid 
at ordinary temperature and III a little less rapidly. Menthenols IV 
and V react so much slower than I, II and III, that separation of 
these two groups can be effected in this way, taking advantage of the 
fact that the resulting terpins are not volatile with steam. Other 
substances having a methene group in a side chain are also very easily 
hydrated by dilute sulfuric acid, for example, dihydrocarveol and iso- 
pulegol, 



/\ OH 
\ 



H 



/\ OH 

/ \/ 
\ 



\ / 






H 



dihydrocarveol 



/\ 



■OH 



'^Ann. seo, 82 (1908). 



130 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



//^\ 



OH 



\/ H 



I I OH 

I 1/ 

\ /\ 
\/ H 



/\ 



OH 



isopulegol 

The facility with which such unsaturated groups are hydrated af- 
fords an explanation of the rearrangement of many unsaturated sub- 
stances in the presence of dilute mineral acids, for example, 



/ \ 






./ 



V=° 



isopulegone 



/ 



\ /=o 

Y 

;^oH 






pulegone 



= 



\/ 



./ 



/ 



/• 



k 






/ 



terpinolene 



\/ 



V^X 



\ 



limonene 



\ 



\ 



\ 



\ 






+ 






terpinenes 



y\ 



THE ETHYLENE BOND 131 

The rearrangement of 2-methylbutene-(3) to trimethylethylene by 
dilute acids is probably effected in the same manner/^ 

CH3 CH3 OH CH3 

>CHCH = CH2-^ >CHCH< -> >C = CH.CH3 
CI13 C'H3 CH3 CH3 

Thus when commercial amylene is hydrated by sulfuric acid, the 
resulting alcohol is chiefly "amylene hydrate" or dimethylethylcar- 
binol,^° obtained in very pure condition from trimethylethylene,^' 

CH3 CH3 

>C=:CH.CH3 > >C.0H.CH,CH3 

CH3 CH3 

Amylene and alcoholic sulfuric acid yields amyl methyl ether.^^ 

Unsaturated Hydrocarbons and the Refining of Petroleum Oils. 

From the foregoing section, it is clear that treatment of petroleum 
distillates with sulfuric acid does not completely remove the unsatu- 
rated hydrocarbons but partly polymerizes them. The polymers thus 
formed are not removed with the "acid sludge," but are found in the 
treated and washed oil. This accounts for the relatively large pro- 
portions of high boiling fractions usually obtained when a so-called 
cracked gasoline is refined by sulfuric acid and then redistilled.^^ 
When the sulfuric acid from a refining operation is diluted with water 
an "acid oil" is precipitated which, in the case of gasoline and kerosene, 
has a pronounced odor due chiefly to the alcohols present. Acid oil 
from the lower boiling distillates, gasoline and kerosene, contain little 
tarry matter. Pure mono olefines of the aliphatic series do not yield 

" On account of this tendency of unsaturated substances to rearrange, in the 
presence of sulfuric or other mineral acids, the method of determining the constitution 
of unsaturated hydrocarbons by oxidation by chromic acid is not to be relied upon. 
The same consideration applies to the oxidation of certain alcohols, for example, a 

CH3 
substance containing the group > CH.CH2CI-IOH — CH2 — E would undoubtedly 

CH3 
yield a mixture of oxidation products, among which acetone derived from 
CH3 

> C = CH — R would be found. 

CH3 X 

" It will be noted that the alcohols derived from the hydration of ethylene double 
bonds are always tertiary or secondary alcohols ; the hydroxyl group becomes attached 
to the more "positive" carbon atom. The industrial manufacture of alcoholic solvents 
from low-boiling olefines, derived from petroleum or the commercial "amylene" obtained 
as a by-product of the manufacture of oil gas or Pintsch gas, has been attempted. 
The "acid oils" obtained by diluting the sulfuric acid used in refining gasoline made 
by pressure distillation or similar methods also contains secondary and tertiary 
alcohols. Although the tertiary alcohol, dimethyl ethyl carbinol, boiling point 102°, 
is an excellent solvent for cellulose nitrate, it cannot be acetylated by ordinary 
methods. Lilie the majority of tertiary alcohols, it has a camphor-like odor. 

" Wischnegradsliy, Bcr. 10, 81 (1877) ; Ann. 190, 332, 366 (1878). 

" Eeychler, Oliem. Zentr. 1907, I, 112,5 ; Henry, Bull. Acad. roy. Bely. 1906, 261. 

" Cf. Brooks & Humphrey, loc. cit. The proportions of such high boiling polymers 
contained in a refined oil will be greater if the duration of the treating operation is 
prolonged, or the mixture allowed to stand. 



132 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

tars with concentrated sulfuric acid at ordinary temperatures, but 
diolefines, particularly those containing conjugated double bonds, re- 
act very energetically with sulfuric acid, forming tars. and reducing the 
acid. Thus highly unsaturated oils, made at very high temperatures, 
such as crude benzene derived from oil gas or Pintsch gas manufac- 
ture, react violently with sulfuric acid on account of the cyclohexadiene 
and other di-olefines contained in such oils. 

When gasoline or kerosene containing unsaturated substances is re- 
fined by sulfuric acid and then redistilled, liberation of sulfur dioxide 
is always noted. This is present in the alkali washed oil, prior to dis- 
tillation, in the form of neutral or dialkyl esters of sulfuric acid, 
. (R0)2S02. These esters are decomposed on heating, yielding tarry 
matter and sulfur dioxide. Theory indicates that refining with a mini- 
mum of sulfuric acid leads to the formation of neutral or dialkyl 
esters, which partly remain dissolved in the treated oil, and greater 
proportions of sulfuric acid favor the formation of acid or mono-alkyl 
esters which are readily washed out. Practice confirms this suppo- 
sition; oils refined by relatively small quantities of acid contain more 
sulfur, in a form appearing as SOj on heating, than oils treated with 
relatively larger quantities of acid. 

It is also evident from the foregoing section that the per cent by 
volume of unsaturated hydrocarbons contained in a certain distillate 
cannot be accurately ascertained by treating with sulfuric acid. The 
usual practice has been to determine the loss on treating with concen- 
trated sulfuric acid but it is evident that the formation of polymers 
entirely destroys the quantitative character of such a determination. 
Such tests are of qualitative value only. The results obtained by em- 
ploying sulfuric acid, Sp. Gr. 1.84 are too low, at least for gasolines 
and kerosene, and the results obtained when fuming sulfuric acid is 
employed are too high since Worstall *" has shown, and it is a matter 
of common experience that fuming sulfuric acid attacks saturated hy- 
drocarbons. Fuming sulfuric acid also sulfonates any aromatic hydro- 
carbons which may be present. No accurate quantitative method is 
now known for the determination of the percent by volume of un- 
saturated hydrocarbons in a mixture containing also saturated hydro- 
carbons (probably of various types) and aromatic or benzenoid hy- 
drocarbons. 

"Am. Chem. J. 20, fi64 (1898). The original method as recommended by KrSmer 
and Botteher specified the use of fuming sulfuric acid. Worstall oljtained yields of 
30 to 40% of the sulfonic acids of n.hexane, n.heptane and n.octane. According to 
Markownikow naphthenes are simultaneously sulfonated and oxidized by fuming 
sulfuric acid. {J. Buss. Phys.-Chem. Soc. 1892, 141.) 



THE ETHYLENE BOND 133 



Other Reactions of Olefines. 



The oxidation of unsaturated hydrocarbons by air or oxygen is 
nearly as general a reaction as the reaction with ozone, although much 
less energetic than the latter. The oxidation of turpentine, and the 
formation of what are now recognized as peroxides, was noted by 
Schoenbein in his well-known studies of oxidation, hydrogen peroxide 
and ozone and, Berthelot like Schoenbein, wrote of ozone formation 
when turpentine is oxidized by air. Fudakowski "^ noted that light 
petroleum fractions acquired oxidizing properties similar to oxidized 
turpentine, when these oils were exposed to light and air. Kingzett "^ 
first proved that ozone was not present and attributed the ability of 
such oxidized material to effect the oxidation of other substances, to 
the presence of a peroxide or "hydrated oxide." A great deal of ex- 
perimental work on this subject was done many years ago, but the 
whole matter was greatly clarified by Engler and Weissberg,"^ Bach "* 
and others and the general character of the "autoxidation" of these 
unsaturated hydrocarbons finds close parallels in the air oxidation 
and resinification of rubber, particularly prior to vulcanization, the oxi- 
dation and consequent deterioration of rosin, copals and varnishes, the 
drying of linseed and similar oils and the deterioration of many sub- 
stances by oxidation brought about by some second unsaturated sub- 
stance occurring with it, for example, the destruction of cellulose fiber 
when in contact with lignin or rosin sizing. Engler and Weissberg 
showed that "the oxygen combines as molecular oxygen," and that "a 
peroxide is formed which may then rearrange to ordinary oxides, or 
may react upon other unoxidized substance." In the case of turpen- 
tine, the per cent of peroxides present after oxidation at temperatures 
up to 160° decreases rapidly with rising temperature, and a sample 
rich in peroxides, formed at low temperature,, is rapidly altered by 
heating, the peroxides being decomposed, with further oxidation of the 
turpentine. As surmised by Kingzett and later shown conclusively by 
Clover and Richmond ^^ organic peroxides are hydrolyzed by water 
forming hydrogen peroxide, which accounts for the many positive re- 
actions for this substance obtained by the earlier investigators. Engler 

"Ber. 6, 106 (1873). 

"J. Ghem. Soc. 12, 511 (18T4). 

""Vorgange d. Autoxydatlon, 1904; Ber. SI, 3050 (1898). 

'*Oompt. rend, m, 2951 (1897). 

""Am. Chem. J. 29, 179 (1903). Tbe oxidizing power of old oxidized turpentine 
has been utilized In medicine, as an antiseptic, as an antidote for certain poisons, 
sucli as yellow phosphorus, and the more stable peroxides, such as benzoyl peroxide 
and benzoylacetyl peroxide studied by Clover and Kichmond have been tried as anti- 
septics for diseases of the intestinal tract. 



134 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

and Weissberg were able to isolate the peroxides of amylene, trimethyl 
ethylene, and hexylene in fair degree of purity. 

Rupture of the ethylene bond by autoxidation has been noted in 
many instances, aldehydes, ketones or acids being formed ; the methene 
group >C = CH2 splits with the formation of formaldehyde or formic 
acid, as in the case of p-pinene, limonene^^ and p-phellandrene." 
Willstatter sought a catalyst, in the hope that oxidation of unsaturated 
substances might be effected as easily as hydrogenation in the presence 
of fine nickel but, although metallic osmium appears to catalyse the 
reaction and cyclohexene was thus oxidized, in acetone solution, to 
cyclohexenol, the method has had no further extension.''^ However, the 
industrial use of catalysts in promoting air oxidation has long been 
known in the paint and varnish industry where salts or resinates of 
manganese, lead and cobalt are widely used. The effect of light in 
accelerating such oxidations has also long been known. In the autoxi- 
dation of styrene marked polymerization occurs, but in direct sunlight 
fission of the side chain occurs with the formation of benzaldehyde 
and formaldehyde."^ The effect of sunlight in promoting autoxidation 
has been studied by Ciamician and Silber '" whose investigations also 
show that oxidation under these conditions is by no means limited to 
substances containing an ethylene bond, but very stable ketones such 
as cyclohexanone and menthone are oxidized and their carbocyclic 
structure ruptured. Vanadium pentoxide^^ has come into vogue as 
catalyst for oxidizing a wide variety of substances by means of air at 
elevated temperatures, for example, naphthalene to phthalic acid or an- 
hydride. These conditions are quite different from those commonly un- 
derstood as autoxidation. The oxidation of defines or saturated non- 
benzenoid hydrocarbons by this method has not been reported, but 
judging from their oxidation under very similar conditions the resulting 
products would probably be water, carbon dioxide, unchanged hydro- 
carbon and small yields of the simpler aldehydes and acids. 

Closely related to the subject of autoxidation is the method dis- 
covered by Prileshajew" who has shown that benzoyl peroxide, 
CeHjCO . . OH, combines directly, in cold neutral solvents, with sub- 

"Blumann & Zeitschel, Ber. 1ft, 2023 (1914). For the oxidation of ethylene to 
formaldehyde see Ethylene, Willstatter, Ann. 1,» (1921). 

»' Wallach, Ann. 3;,S, 30 (1905) ; Xi, 291 (1908) ; Kingzett has noted the corrosion 
of metal containers, used for turpentine, due to solution of the metal by formic acid. 

"Ber. Ifi, 2952 (1913). 

™ Stobbe, J. prakt. Chem. 1911,, 551. 

■"Ber. J,2, 1510 (1909) ; ;,6, 3077 (1913). 

" Senderens employed it for oxidizing alcohols. [J. Chem. Soc. 1913, I, 814.] 
Naphthalene and benzene are also oxidizable by its aid. 

"Ber. i2, 4812 (1909) ; J. Russ. Phvs.-Chem Soc. 1,3, 609 (1911) ; U, 613 (1912). 



THE ETHYLENE BOND 135 

stances containing an ethylene bond. The initial product readily de- 
composes to give an oxide of the original olefine, and these oxides are 
generally very easily hydrolysed to glycols. The method was applied 
particularly to the oxidation of linalool, geraniol, citral and citronellal. 
The hydrocarbons di-isobutylene, decylene and the terpenes limonene 
and pinene yield oxides, which may be hydrolysed to glycols, which 
suggests that the autoxidation of other unsaturated hydrocarbons, for 
example, unsaturated petroleum hydrocarbons, may lead to the for- 
mation of glycols as one of the minor products, when moisture, suffi- 
cient for hydrolysis, is present. 

Probably the best known method of oxidizing the olefine group 
for the purpose of determining the constitution of organic substances 
is that of oxidizing by cold dilute potassium permanganate. Thus 
trimethyl ethylene gives a very good yield of the corresponding gly- 
col,'^ and diallyl yields a hexyl erythrite. An excess of permanganate 
results in further oxidation of the glycol with a break in the carbon 
atom chain, as in the rupture of the double bond in a-pinene to form 
pinonic acid.'* This break in the carbon atom structure of a substance 
does not always occur at the point at which the double bond was origi- 
nally located, as has been shown in the case of carvenone and ter- 
pinenol-(4). Nevertheless, this method of oxidation and the ozone 
method are the most reliable means yet discovered of determining the 
position of ethylene bonds in organic substances. 

The reaction of sulfur with unsaturated hydrocarbons has been 
little investigated. According to H. Erdmann''' sulfur exists at 160° 
largely as S3 or thiozone, and at this temperature he succeeded in 
forming a "thiozonide" of linalyl acetate C12H20O2S3 and was unable 
to obtain a derivative containing less than three atoms of sulfur. 
Friedmann,'" however, isolated a compound CioHjjS by reacting upon 
dicyclopentadiene with sulfur." By heating sulfur and turpentine 
together at 150° a viscous product containing 30 to 50 per cent of sul- 
fur can be obtained.'^ 

The reaction of sulfur with unsaturated hydrocarbons is of interest 
in connection with the vulcanization of rubber. In addition to the evi- 
dence furnished by the ozone reaction, the action of oxygen upon thin 

"Wagner, Ber. 21, 1230, 3343 (1888). 
"Baeyer, Ber. 29, 22 (1896). 
"Ann. 362, 133 (1908). 
"Ber. 49, 50, 683 (1916). 

"Koch, German Pat. 236, 490 (1909), prepares sulfur derivatives of terpenes by 
heating with sulfur until hydrogen sulfide is evolved. 
"Pratt, U. S. Pat. 1,349,909. 



136 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

films of rubber indicates the presence of two double bonds for each 
C10H18 complex, two molecules of oxygen being combined/^ and when 
treated with sulfur chloride ^° the limit of the reaction corresponds 
more closely to Weber's (CioHj5S2Cl2)n than to Hinrichson's 
[(Ci(|Hig)2S2Cl2]n- When pure Ceylon para, gutta-percha and ex- 
tracted and purified balata are treated with 37 per cent of sulfur at 
135° the final products are apparently identical and correspond to 
the empirical formula (CioHieS2)n-*^ In the ordinary hot process of 
vulcanization, using about 10 per cent of sulfur the first stage evi- 
dently consists in adsorption, followed by slow chemical combination,*^ 
and when sulfur chloride is employed adsorption followed by slow 
chemical combination appears to be the result.*^ 

Vulcanization is essentially an increase in the degree of polymeri- 
zation of the rubber and when this is effected by means of sulfur or 
sulfur chloride, it is probable that combination also occurs between 
sulfur atoms attached to different complexes or molecules, since the ten- 
dency of sulfur derivatives to polymerize is well known, as for example 
the thio-aldehydes. The literature on the subject of vulcanization is 
voluminous, and is burdened by much speculative matter which will 
not be reviewed here; the subject is complex and the effect of varia- 
tions in mechanical treatment, and the presence of other substances, 
is often very marked. These effects are of great importance to the 
rubber industry but are not of general interest. The causes of the 
variability of the vulcanization of plantation Hevea rubber have been 
particularly well investigated ** and recently a large number of sub- 
stances have been investigated which promote further polymerization 
independently of sulfur or which greatly accelerate the vulcanization 
when sulfur is employed. Thus para nitrosodimethylaniline, one of 
the most potent accelerators, when added in amounts equivalent to 
0.33 to 0.6 per cent, reduces the time required for vulcanization to 
about one-third that normally required and the proportion of sulfur 
may also be somewhat reduced. That many mineral substances, 
such as litharge, red lead, zinc oxide, magnesium oxide, etc., accelerate 
vulcanization by sulfur has long been known but a large number and 
variety of organic substances also function in this manner. A large 
number of aromatic nitro derivatives, piperidine and quinoline and 

"Peachey, J. 8oc. Chem. Ind. SI, 1103 (1909). 

"Kirchof, Kolloid Z. U,, 35 (1914). 

" Spence and Young, KolloU Z. XS, 265 (1913). 

''Harries, Ber. 1,9, 1196 (1916). 

" Hinrielison, Chem. Abs. M, 104 (1918) ; van Eossem, Chem. Abs. 12, 2142 (1918) 

M Baton & Grantham, J. Soe. Chem. Ind. Si, 989 (1915). 



THE ETHYLENE BOND 137 

their derivatives, amines and substituted amines and ureas, have been 
found to have accelerating effects.^^ Barium peroxide alone has no 
vulcanizing effect but benzoyl peroxide does "vulcanize" in the absence 
of sulfur ** but the product is markedly different from the commercial 
products made by the use of sulfur or sulfur chloride.^^ Dubosc has 
insisted that colloidal sulfur, which he assumes is formed by the inter- 
action of hydrogen sulfide and sulfur dioxide, produced in situ during 
vulcanization, is solely responsible for the vulcanization effects. This 
opinion is not commonly held but it is of interest in view of the fact 
that a process of cold vulcanizing has recently come into use which 
consists in treating rubber with a mixture of these two gases, sulfur 
being formed in an extremely finely divided state. Reychler ^' showed 
that rubber takes up nearly 25 times as much sulfur dioxide as CO2, 
under comparable conditions, and Peachey ^° has taken advantage of 
this fact in his process of vulcanization just alluded to. 

The saturation of the double bonds in rubber by sulfur explains 
the value of "hard rubber" in handling hydrochloric, hydrofluoric 
and other acids. The action of sulfuric or other mineral acids upon 
unAoilcanized rubber has been but very little investigated. 

Addition of Ozone. 

That ozone is capable of reacting with unsaturated hydrocarbons 
has been known for many years, the reaction of ethylene and ozone 
to form formaldehyde, formic acid and carbon dioxide having been 
noted by Schoenbein;°° also the reaction between benzene and ozone 
was studied by Houzeau and Renard "^ but the reaction product was 
regarded as a peroxide rather than an ozonide. The true character 
of these reactions was first made clear by Harries, who pointed out 
that reaction with ozone in the absence of moisture gave thick viscous 
substances, which were very explosive, but which he was able to show 
by analysis consisted of products containing O3 for each double bond 
present in the original substances. These ozonides can break down 
in two ways as follows, — • 

1 — ^By reaction with water to form hydrogen peroxide and ketones 
or aldehydes accompanied by complete rupture of the double bond. 

'"Twlss, J. Soc. Chem. Ind. SB, 782 (1917) ; King, Met. & Chem. Eng. IS, 231 
(1916) . 

«» OstromuisIensM, J. Ruas. },1, 1462 (1915). 

" TwiS8, loc. cit. 

»«/. chim. phus. 8, 617 (1910). 

" Peachey & Shipsey, J. Soc. Chem. Ind. 1321, 4 T. 

"J. prakt. Chem. 66, 282 (1855). 

'^Compt. rend. 76. 572 (1873). 



138 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

>C C< + H,0 >>C0 + 0C< + H^O, 

0—0—0 
2 — Decomposition can take place on warming or in solvents such as 
absolute alcohol or glacial acetic acid in the absence of water to give 
a peroxide and a ketone or aldehyde. 


>C C< »C<| +0C< 

0—0-0 
The peroxides formed as in equation (2) can often react with water 
to form a carboxylic acid; for example, mesityl oxide ozonide breaks 
down in accordance with the two schemes just shown as follows: 
(a) 



(CH3),C 

I 

— 0- 
(b) 
(CH3),C 



CH.CO.CH, 







+ H,0 -> (CH3) ,C0 + OCH . CO . CH3 
+ HA 



CH . CO . CH3 -» (CH3) 2CO 



— 0-0 



+ |>CH.C0.CH3 




(b.) 




I > CH . CO . CH3 + H,0 -» HCO2H + CH..C00H. 


Decomposition according to (b) and (bi) accounts for the fact 
that the yield of methylglyoxal is relatively small and formic and 




Mot- 




CH3 

pulegone ozonide 



3 ^^^3 

P-methyl- 
adipic add 



yCO 
/ \ 

ZV\i CH3 

1-methylcyclo- 
hexanedione-(S, 4) 



THE ETHYLENE BOND 



139 



acetic acids are formed. This type of decomposition accounts for re- 
actions which were for a time considered abnormal, for example, — 
pulegone ozonide "^ yields p-methyladipic acid and not the substance 
which would be expected from the character of the great majority of 
ozonide decompositions, namely, l-methylcyclohexanedione-(3, 4) 

Similarly camphene gives a little camphenilone and a relatively 
large yield of a lactone, whose formation is attended by rupture of the 
six carbon ring.*' 




HCHO 



Harries regards these peroxides formed by the decomposition of 
ozonides as having the constitutions indicated in the above examples. 
Another type of peroxide is formed by the direct action of ozone upon 
carbonyl derivatives, aldehydes or ketones, thus nonyl aldehyde acted 
upon by ozone forms a labil peroxide melting at about 10°, but a more 
stable peroxide of the same empirical formula CHj. (CHjj)7.CH02 is 
formed by the decomposition of the ozonides of substances containing 
the group CH3(CH2)7CH = CHR. This more stable peroxide melts 
at 73° and can readily be recrystallized. 

The reaction of ethylene bonds with ozone is substantially as gen- 
eral a reaction as is the reaction of bromine. In fact, ozone reacts with 
many substances, which are commonly regarded as not having unsatu- 
rated bonds of the ethylene type, for example, benzene and naphtha- 
lene. It is of interest to note that the ethylene bond in fumaric acid, 
which substance is not hydrated by sulfuric acid, reacts only very 
slowly with ozone, but when prepared by employing very concentrated 
ozone the ozonide spontaneously decomposes on standing, yielding the 
original substance, fumaric acid. This reaction, which has been em- 
ployed so successfully by Harries in the investigation of various kinds 
of caoutchouc, has been an outgrowth of his studies of the reaction 
of ozone upon mesytilene, amylene, 2.6-dimethylheptadiene-(2, 5), 
diallyl, and similar substances. In this connection, it should be men- 
tioned that conjugated dienes react very energetically with ozone to 

•= Harries, Ann. S7i, 297 (1910). 

"Semmler, Ber. iB, 246 (1909) ; Palmen, Ber. iS, 1432 (1910). 



+ 2HCH0 



140 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

form mono-ozonides, but the diozonides are formed only very slowly. 
Diallyl, or 1, 5 hexadiene, in chloroform solution readily gives a very 
explosive syrupy diozonide, which on hydrolysis yields succinic dialde- 
hyde and formaldehyde. 

/\ 

CH^CH = CH^ CH3CH CH, CH^CHO 

I —.1 -^ I 

CHjCH = CH^ CH^CH CH, CH.CHO 

03 

Geometrical isomers of the type of fumaric and maleic acids yield 
identical ozonides or rather identical hydrolytic products, which fact 
may serve to establish the structural similarity of such isomers. 

The work of Harries on the constitution of certain unsaturated 
hydrocarbons has clearly shown that most of them are in reality mix- 
tures of isomers, a fact brought out in the section on the preparation 
of unsaturated hydrocarbons. Thus the octadiene made by the action 
of methyl-magnesium iodide on succinicdiethyl ester and decompo- 
sition of the resulting glycol or its bromide was supposed to have the 
constitution, — (CH3)2C = CH.CH =C(CH3)2 but the ozone method 
clearly shows that this hydrocarbon is in reality a mixture chiefly con- 

\ / 

sisting of the hydrocarbon C.CH, — CHj — C (2.5 di- 

/ ■ \ 

CH3 CH3 

methylhexadiene — (1.5) ). 

When the alkaloid pseudo-pelletierin is decomposed by the method 
of exhaustive methylation, the basic nitrogen atom is removed and a 
cyclo-octadiene results which Willstatter and Veraguth °* were inclined 
to regard as containing a pair of conjugated double bonds. Their 
cyclo-octadiene polymerized with remarkable ease. Nevertheless, Har- 
ries showed that this hydrocarbon forms a diozonide which is hydro- 
lyzed normally yielding succinic dialdehyde, and succinic acid, indi- 
cating that the hydrocarbon is cyclo-octadiene — (1.5). 
CH, CH^ CH2 CH = CH — CH, 

I i \ i \ 

CH, H0.N(CH3)2 CH2 — ^CH, CH, 

I I / I ' / " 

CH2 CH2 CHj CH — CH = CH 

"Ber. S8, 1975 (1905) ; iO, 959 (1907). 



THE ETHYLENE BOND 



141 



O3 
/\ 

CH2 — CH CH — CHj 



CH, — CHO 

2 I 
-> CH, — CHO 



CH2 — CH CH — CH, 

\/ 

O3 

Harries has summarized his researches on ozonides in four general 
articles.'^ Some of the ozonides first prepared by Harries in the earlier 
period of his researches were not pure and consisted apparently of 
mixtures derived by the addition of O3 and also the hypothetical com- 
pound 0^ or oxozone. After passing the crude ozone-oxygen mixture 
through 5 per cent caustic soda and then through sulfuric acid, the gas 
then gave pure ozonides. Polymeric forms of ozonides have frequently 
been noted, an oily volatile monomolecular form having usually a 
sharp disagreeable odor, and polymers in the form of solid gummy, 
glassy or crystalline substances having little or no odor, usually being 
observed. Thus monomolecular butylene ozonide can be distilled in 
vacuo and it readily dissolves in the common solvents. The dimeric 
form of butylene ozonide, however, is an almost odorless gummy sub- 
stance very sparingly soluble in water. Formation of ozonides at low 
temperatures, below 0°, favors larger proportions of the polymeric 
forms. 

Unsaturated cyclic hydrocarbons behave toward ozone and sub- 
sequent hydrolysis generally like aliphatic olefines. Cyclopentene 
ozonide, CgHgOg, is soluble in the common solvents and is smoothly 
hydrolyzed by water resulting chiefly in the mono-aldehyde corre- 
sponding to glutaric acid, 



CH, — CH 



CH, — CH2 



> 



CH- 



CH, — CH -- 







CHj — COOH 



.CH — > CH, — CH, — CHO 

CHj — CH, 

"Ann. SiS, 311 (1905) ; m,, 288 (1910) ; 390, 236 (1912) ; ^10, 1 (1915). 



142 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Cyclohexene ozonide is much more stable to water but on long boil- 
ing yields hexane dialdehyde and adipic acid. Limonene readily yields 
a mono-ozonide, the isopropenyl side chain "^ first being reacted upon, 
and at a much slower rate the cyclic double bond is attacked.^' 

By the ozonization of natural Hevea rubber, Harries obtained lae- 
vulinic acid and laevulinic aldehyde,"' from which observation he 
concluded that Hevea rubber is a polymer of the di-isoprene, 1.5- 
dimethyl cyclo-octadiene-(1.5), 

CH2CH = C(CH3).CH2 

-A, 



CHjC = CH CHj 



ii 



However, the real unit, which is polymerized to ring complexes an 
unknown number of times, is the group — CH2C(CH3) = CH-CHj — . 
Artificial isoprene rubber, on treating with ozone and subsequent hy- 
drolysis, yields succinic acid and acetonylacetone in addition to lae- 
vulinic acid and aldehyde,"" which products could conceivably be de- 
rived from 1.6-dimethylcyclo-octadiene-(1.5). 

The first work upon the treatment of petroleum distillates with 
ozone appears to have been done by Molinari and Fenaroli,^"" who ob- 
tained a yield of 32 per cent of an ozonide from a kerosene fraction, 
boiling at 295°-300°, derived from a Russian petroleum. The subject 
has not been pursued further but inasmuch as Harries observed that 
refined petroleum ether and hexane are not altogether unacted upon 
by ozone when used as solvents for unsaturated substances, the con- 
clusions of Molinari that a conjugated di-olefine, Cj^Hgo, was present 
in the relatively large proportions indicated by the yield stated, are 
hardly to be accepted. Ethane is reacted upon by dilute ozone at 
100°, the initial oxidation products being ethyl alcohol and acetalde- 
hyde.^"^ During the recent war period Harries turned his attention 

"Prior to the researches of Harries, vanillin had been made by the action of 
ozone on iso-eugenol. (Otto, Ann. d. Chim. d Phys. [7J 13, 120 [1898] ; German Pat. 
97, 620.) Better yields were, for a time, obtained by using crude ozonizing apparatus 
giving dilute ozone, about 1%, than when using more concentrated ozone made by 
improved apparatus. Harries later showed that 70% yields could be obtained by 
treating the ozonide with zinc dust and acetic acid (Ber. 1,S, 32 [1915].) The side 
chain in satrol also reacts readily, Semmler and Bartlett (Ber. J,!, 2751 [1908])', obtain- 
ing homopiperonylic aldehyde. 

" Critical examination of Harries' work Is apt to elicit the fact that he frequently 
paid little attention to the history or purity of his original material and also that 
more definite results might often have been obtained, in the terpene series, in the 
hands of other well-known specialists in this field. 

"Ber. 38, 1195, 3986 (1905) ; ^6, 733 (1913) ; Ann. m, 173 (1914). 

" Steimmig, Ber. Ift, 350 (1914). 

■^""Ber. 1,1, 3704 (1908). 

"iBone and Drugman, Proc. Chem. Soc. 20, 127 (1904). 



THE ETHYLENE BOND 143 

to the oxidation by ozone of the highly unsaturated oily distillates 
obtained by the low temperature carbonization of lignite. Although 
the method had a large scale trial in Germany during the stress of 
conditions imposed by the war, the yields of fatty acids obtained were 
very small and the project was soon abandoned/"^ Harries identified 
stearic, palmitic and myristic acids among the reaction products, to- 
gether with relatively large proportions of simpler, water soluble acids, 
including formic, acetic, propionic and oxalic acids. 

The reaction of unsaturated hydrocarbons with sulfur trioxide is 
naturally a very energetic one leading, under ordinary experimental 
conditions, to oxidation of the hydrocarbon and formation of SOj. A 
definite reaction product is easily obtainable with ethylene, the crystal- 
line anhydride carbyl sulfate being formed. 

CH, CH,-SO,\ 

II +2SO3 *| >0 

CH^ CH, — - SO, 

No further work on this reaction seems to have been done since its 
discovery in 1838 ^"^ and whether ethylene homologues can form similar 
derivatives (at low temperatures in a neutral solvent) is not known. 
The anhydride carbyl sulfate reacts energetically with water "* to 

CH^.SOsH 
form ethionic acid, | which substance is then rapidly 

CH^.O.SO^H 

CH^.SOsH. 
hydrolyzed to iso-ethionic acid I Sulfonic acid groups in 

CH,.OH 
which sulfur is bound directly to carbon, as in iso-ethionic acid, are 
not easily displaced and alcohols or glycols cannot be made from them 
by any known methods. 

The propane derivative, propanol-(l) sulfonic acid- (3), is formed 
when allyl alcohol reacts with an alkali bisulfite, 

CH.OH. CH^OH. 

CH + KHSO3 > CH2 

CH2 CH2.SO3K. 

'<" Ozone, as an oxidizing agent to be employed in Industrial operations, Is usually 
much too costly compared with other methods of oxidation, although its cost may be 
expressed largely in terms of the cost of electrical power. 

■»»Regnault, Ann. 85, 32 (1838) ; Magnus, Pogg. Ann. p, 509 (1839). 

>»«CIaesson, J. prakt. Chem. (2), 19, 253 (1879). 



144 CHEMISTRY OF THE NON-BEN ZENOW HYDROCARBONS 

The behavior of ethylene bonds to sulfur dioxide and aqueous sul- 
jurous acid is very different from sulfuric acid in that hydration to alco- 
hols does not occur, but addition to form very stable sulfonic acids is 
frequently the result. This reaction follows the general rule that other 
adjacent groups exert a very great influence upon the reactivity of the 
unsaturated bond. Anhydrous sulfur dioxide has not been shown to 
react with unsaturated hydrocarbons, although the very marked solu- 
bility of such hydrocarbons in liquid sulfur dioxide and the complete- 
ness with which they may be extracted from paraffine hydrocarbon 
mixtures, as in the Edeleanu refining process, might be considered as 
an indication of the formation of such labil compounds. When solu- 
tions of amylenes or butylene in sulfur dioxide are subjected to the 
action of heat and light, amorphous hornlike solids are formed,^''^ the 
butylene compound having the composition (CiHgSOa)^ and when the 
conjugated diene, isoprene, is allowed to stand two days in liquid 
sulfur dioxide a crystalline substance CgHsSOa, is formed."* 

Sulfonic acid derivatives of sabinene, sabinol and pulegone are 
formed when SO2 is passed into their cooled alcoholic solutions ^"^ but 
the formation of sulfonic acid derivatives has been most frequently ob- 
served in cases where the ethylene bond is adjacent to a carbonyl 
group, >CH = CH — C — . Thus acrolein"** and crotonic alde- 



hyde ^°° react with sodium bisulfite normally so far as the aldehyde 
group is concerned but the ethylene bonds react also, to form stable 
sulfonic acid derivatives, which are not affected by treating with alkali. 
The aldehyde group generally reacts more readily with bisulfite than 
the ethylene bond and advantage is taken of this fact in isolating un- 
saturated aldehydes, such as citral and citronellal, from mixtures 
containing them. Citral contains two double bonds, one of them adja- 
cent to the aldehyde group, and both ethylene bonds may react yield- 
ing the stable disulfonic acid salt, CgHi^. (S03Na)2.CHO, from which 
citral cannot be regenerated. When cold neutral sodium sulfite is em- 
ployed and the alkali, formed by the reaction, is neutralized as fast 
as formed, 

C^Hi, . CHO + 2Na2S03 + 2H2O ^ C,H,, (S03Na) ^CHO -f- 2NaOH 

'""Mathews and Elder, J. Boc. Chem. Ind. 1915, 670. 

"■de Bruin, Uhem. Abs. 9, 623 (1915). 

«" Wallacb, Nachr. TFiss. Oes. Ooettingen. 1913, 321. 

'"Mtiller, Ber. 6, 1442 (1873). 

™Haubner, Uonatsh. 12, 546 (1891). 



THE ETHYLENE BOND 145 

then an unstable dihydrosulfonate is formed from which citral is easily 
regenerated. '^^° Citronellal contains only one double bond and this is 
far removed from the aldehyde group and accordingly less reactive. 
Under the conditions just described citi'onellal is not reactive;"^ with 
cold concentrated bisulfite, in the presence of sodium bicarbonate, the 
aldehyde group only reacts, and normally, but when warmed with an 
excess of bisulfite (containing a little sulfite) the stable sulfonate is 
formed.^^^ 

CH„ 



cold/" 
citronellal 



^8\ OH 

C = CH.CH,CH2CH.CH,CH< 



\ CH, 

hot\ 

CH, 



.H, 



\ OH 

C — CH2 . CH^CH.CH . CH,CH < 

/\ I ' OSO„Na 

SOsNa CH3 

cannot be regenerated. 



Nitrosyl chloride has been a most useful reagent in the investiga- 
tion of the terpenes but has not been used in the investigation of 
unsaturated hydrocarbons derived from petroleum, although the 
first thorough study of the addition of nitrosyl chloride to defines 
was carried out with amylene.^^^ When Wallach first undertook the 
study of the terpenes the literature had become confused with a va- 
riety of names for hydrocarbons which were not clearly differentiated, 
one from another, and the names adopted usually referred to various 
particular sources. The reaction with nitrosyl chloride, which had 
been discovered by Tilden and Shenstone,"* proved to be a most 
valuable reagent for the preparation of characteristic crystalline de- 
rivatives of these unsaturated hydrocarbons and the multiplicity of 
names began to diminish as the identity of differently named terpenes 
was established. The addition products formed by the reaction of 
these hydrocarbons with nitrogen trioxide and nitrogen tetroxide also 
proved useful in this connection. Crystalline tetrabromides, dihydro- 
chlorides, etc., also assisted in this work of identification and "cit- 
rene," "hesperidene," and "carvene," for example, were shown to be 
identical and are known as limonene. 

"»Tiemann, Ber. SI, 3306, 3315 (1898). 
I" Tlemann, Ber. S2, 816, 818 (1899). 
'"Tiemann, Ber. SI, 3306 (1898). 
""Wallach, Ann. ^5, 246 (1888). 
"' J. Chem. Soc. 1877, I, 554. 



146 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Among the simpler defines the ability of olefines to combine with 
nitrosyl chloride increases with molecular weight (or introduction of 
the "positive" methyl groups) : ethylene forms only ethylene chloride, 
and propylene forms both the' dichloride and nitrosochloride.^^^ As 
indicating the variety of ethylene types which form nitrosochlorides, 
the following may be mentioned, trimethyl and tetramethyl ethyl- 
ene, cyclohexene, methene derivatives R2C = CHj, and also hy- 
drocarbons having a semicyclic double bond and a side chain, as 

CH, 
(CH2)x< >C = CH.R. Unsaturated hvdrocarbons having the 

groups >C ^ CHj, and — CH = CHj, do not usually yield crystalline 
nitrosochlorides: ^^* the type RaC = CHR usually does yield crystal- 
line nitrosochlorides.^^' The terpene, p-fenchene 




forms a crystalline nitrosochloride and Wallach has obtained such 
crystalline derivatives from other hydrocarbons whose double bond 
is similarly situated.^^' 

The crystalline nitrosochlorides, nitrosites and nitrosates are gen- 
erally bimolecular ^^^ and hence called tiis-nitrosochlorides, 6is-nitro- 
sites and bis-nitrosates, but in solution many ^^" of these derivatives 
are blue in color and are monomolecular. . Many of the nitrosochlorides, 
in monomolecular form, are volatile with steam without decomposition ; 
for example, the blue modifications derived from the hydrocar- 
bons,^"' "2 

""TiMen & Sudboroiigh, J. Chem. Soc. 6S, 479 (1893). 

!■« Meyer, "Analyse & Konstitutioniren. org. Verb," Ed. 2, Berlin, 1909, p. 939. 

"'Weyl, "Die Methoden d. org. Chemle," II, 639 (1911). 

"s^n-n. Si7, 322 (1906) ; S65, 267 (1909). 

"•Baeyer, Ber. 28, 641, 650, 1586 (1895) ; 29, 1078 (1896). 

«» Wallach & Sieverts, . A»». 306, 279 (1898), 3.12, 309 (1904), showed that pinol 
nitrosochloride may exist In a colorless monomolecular form. 

'" Wallach, Ann. 353, 308 (1907) ; 396, 280. 

'" The preparation of nitrosochlorides is best carried out by dissolving the hydro- 
carbon in an equal volume of glacial acetic acid, adding one volume of ethyl nitrite, 
cooling to 10°, and then adding one-third volume of concentrated hydrochloric acid. 
In most cases, where a crystalline nitrosochloride is possible, an abundant crystalline 
deposit of the nitrosochloride forms in a few minutes. Acetone is generally the best 
solvent for recrystallizing these derivatives. Nitrosobromides are also easily prepared 
but are less stable than the corresponding chlorides : 5="^ tetramethyl-ethylene and 
5"" ethyl nitrite, cooled to 0° C and treated with 5"' concentrated HBr solidifies in a 
few minutes to the solid bisnitrosobromide. 



THE ETHYLENE BOND 147 



>-C{CH,l «nd (^ )=C(CW,]^ 



The value of the nitrosochlorides has been chiefly their ready con- 
version to oximes, from which ketones may be made, and to other 
more stable substances suitable for identification purposes, for example, 
condensation with benzylamine. All three types of nitroso derivatives 
may be converted into the isomeric oximes by carefully warming with 
alkalies, 

(CH3),C-C1 (CH3),C.C1 



-> 



i = : 



CH3-OH.NO CH3-C = N.0H 

It has been proposed to utilize the reaction with nitrogen tetroxide 
in determining the constitution of olefines, since the addition product 
RCH.NO2.CHNO2.R, is split by heating with concentrated hydro- 
chloric acid to give fatty acids.^^^ 

Ammonia and aliphatic amines react with the ethylene bond in cer- 
tain instances where the very reactive ethylene-carbonyl group 
>CH = CH — C — occurs, as in mesityl oxide, ^^* 



u 



NH2 
/ 

(CH3)2C = CH.CO.CH3 + NH3 -^ (CH3),C 

\ 
CH2COCH3 

Vinyl chloride, which polymerizes on eta.rdino- but is nuite stable to 
sulfuric acid, reacts with ammonia to give ethylenediamine,^^^ 

CHj = CHCl + 2NH3 ^NH^ . CH^CH^NH^HCl 

The unsaturated hydrocarbons themselves are not reactive to am- 
monia or amines. The ethylene-carbonyl group is also reactive to 
hydroxylamine in a fairly large number of substances. Allyl ketones, 
CHj = CH . CH2COR, react normally to give oximes but the ethylene 
bonds in propenyl and vinyl ketones also react,"° 

"•Jegorow, J. prakt. Chem. S6, 521 (1912). 

'" Sokolotf, Ber. 7, 1387 (1874) ; Kohu, Monatsh. 185, 135 (1903) ; Blaise & Malre, 
Compt. rend, m, 215 (1906). 

i25Engel, Compt. rend, m, 1621 (1887). 

"•Blaise, Compt. rend. US, 1106 (1904) ; 1J,S, 215 (1906). 



148 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

R 

/ 

CH2 = CH . COR > NH . OH . CH„CH,C 

\ 
N.OH 

The ethylene-carbonyl group also reacts with aniline, phenyl hydra- 
zine, urea, semicarbazide, mercaptans, hydrogen sulfide, hydrocyanic 
acid, malonic and acetoacetic esters. 

CO^R CO^R 

aniline ^^ + RCH = C < » RCH — CH < 

CO,R I CO^R 



NH.C„H 



CH . COOH NH — CO — CH^ 

urea ^^s _|_ 1 1 ^ 1 1 

CH, CO — NH — CH, 

semicarbazide "" + (CH3)2C = CHCOCH3 

CH3 

/ 

> (CH3)2C — CH,.C = N.NH.C0.NH3 

NH.CO.NH.NH, 

ethyl mercaptan^"'+ (CH3),C = CH.CO 

I 
CH3 

SCoH,, 



> (CH3),C — CH,C< 

SCjHg 
SC2Hg CH3 

hydrogen sulfide ^^^ + carvone > (C^oH-ifi) M^S 

hydrocyanic acid "^ + (CH3),C = CH.COCH3 
^(CH3),C — CH,C0CH3 

:n 



2^ 

A, 



I" Blank, Ber. 28, 145 (1895). 

""Fischer & Boeder, Ber. S/,, 3751 (1901). 

""Important in connection witti the use of semicarbazld for the identification of 
such Isetones ; citronellal and two molecules of semlearbazid gives the crystalline seml- 
carbazino-semicarbazone immediately. Cf. Eupe, Ber. 36, 4377 (1903) • Semmlpr 
Ber. 1,1. 3991 (1908). K'->"Jo, , aemmier, 

i"»Posner, Ber. So, 799 (1902) ; S7, 502 (1904). 

"'OC. Wallach, Ann. m, 385 (1894) ; Sl,s. 32 (1905) ; mesltyloxide and the hydro- 
carbon menthene also form compounds with H«S. 
"^Lapworth, Jour. Chem. Soc. 8S, 1214 (1904). 



THE ETHYLENE BOND 149 

acetoacetic ester "^ + CH^ = CH.CO.R 



CH,COCH.CO,R 



CH,— 



CH2.CO2R' 



The above reactions cannot be said to be general reactions even 
for a, p-unsaturated ketones or acids (the "ethylene-ketone" group), 
and none of them have so far been found applicable to hydrocarbons. 
In fact, until the mechanism of such reactions, and the part played by 
the carbonyl group, is understood, it is questionable whether this last 
group of reactions should really be considered as reactions of the un- 
saturated bond ; it would be more correct to consider them as reactions 
of the>CH = CH — C — or "ethylene-carbonyl" group. These con- 



siderations apply also to the hydrolytic rupture of the ethylene bond of 
this group which is noted when many substances, for example, mesityl 
oxide, citral ^^* and pulegone, are treated with dilute alkalies or min- 
eral acids, thus 

+ H,0 
(CH3) 2C = CH . CO . CH3 ^ (CH3) ,C0 + CH,C0CH3 



(CH3),C = CH.CH,CH,C = CH.CHO 

CH3 

citral 
+ H,0 
> (CH3),C = CH.CH,CH,C = 

CH3 
+ CH3CHO 

Metallic sodium has been observed to combine directly with un- 
saturated hydrocarbons ^^^ only in a few cases where a negative group 
is present, as in stilbene, CgHgCH = CH^. Metallic sodium in a very 
finely divided or colloidal form is employed for the purpose. 

Preparation of defines. 

As regards the preparation of olefine hydrocarbons, it may be 
pointed out that most methods of preparation yield a mixture of isomers 

"» Vorlander, Ann. g9i, 317 (1897). 

"«Verley, Butt. soc. chim. (3), 17, 175 (1897). Effected best by heating with 
potassium carbonate ; pulegone may be hydrolyzed by heating with water In an auto- 
clave. Wallach, Ser. 38, 3388 (1899). 

""Schlenk, Appenrodt, Michael & Thai, Ber. 1,7, 473 (1914). 



150 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

and that often when a single product is theoretically probable a mix- 
ture of isomers results owing to rearrangement. Thus Eltekow "" 
showed that isobutyl alcohol or the corresponding halides decompose 
to give a mixture of three butylenes, 



CH3 


CH3 

1 ^n — r,H 


CH3 


CH3 




CH3CH = CH.CK 




CH,CH,CH = CH, 



Haber ^" showed that on heating normal hexane to 600° to 800°, it is 
decomposed, methane and amylene being found among the products 
formed and assumed that the amylene was alpha amylene, as expressed 
by the equation, 

C3H7 . CH2CH2CH3 > C3H7CH ^ CHj -f- CH4 

But, as indicated in the case of the butylenes, olefines of the type 
RCH = CH2 are prone to rearrangement under the influence of heat. 

CH3 
Thus the amylene >CH.CH = CH., rearranges under the infiu- 

CH3 
ence of heat, or mineral acids, to trimethylethylene, 

CH3 

>C = CH.CH3 
CH3 

Noorduyn ^^^ has made a study of the constitution of the olefines 
formed by heating barium fatty acid salts with sodium ethoxide or 
methoxide. Very little work of this kind, critical examination of the 
constitution of acyclic olefines, has been done. Five methods have 
been used to determine the constitution of unsaturated substances. 

(1) The method of Varrentrap; fusion with caustic potash which 
causes a change of position of the double bond toward the carboxyl 
group (of fatty acids). 

(2) Oxidation by potassium permanganate, in which method 1:2 
glycols are former as intermediate products. 

(3) Beckmann's transposition, in which method the formation of 
the dibromide is the first step. 

'"Ber. 13, 2404 (1880) ; Cf. Net, Ann. SIS, 1 (1901). 

»'5er. t9, 2691 (1896). 

^"Rec. trwv. cMm. S8, 317 (1919). 



THE ETHYLENE BOND 151 

(4) Jegorow's method based upon the addition of N^O^ to the 
double bond. 

(5) Harries' method consisting in reaction with ozone and hy- 
drolysis of the resulting ozonide. 

Noorduyn used the ozonide method. Examination of the decylene 
made by heating the barium salt of undecylenic acid with sodium 
ethoxide and hydrolyzing the ozonide of the hydrocarbon yielded for- 
maldehyde, acetic, propionic, butyric, valeric and hexylic acids show- 
ing that the hydrocarbon is a mixture of isomers. Similarly the hepta- 
decylene, from oleic and elaidic acids and sodium methoxide was shown 
to be a mixture of isomeric hydrocarbons. Nonylenic acid, from oenan- 
thole and malonic ester, yielded a mixture of octylenes and "|3-octyl- 
ene," boiling-point 124°-126° from secondary octyl alcohol was also 
shown to be a mixture. 

Primary alkyl iodides or alcohols invariably yield a mixture of hy- 
drocarbons, as a critical examination of the physical properties of the 
hydrocarbons described in the literature as having been prepared in 
these ways, shows. Thus Morgan and Schorlemmer ^^^ prepared a hex- 
ene, boiling-point 68° to 70°, from a monochlorohexane and Zelinsky 
and Przewalski ^^^ heated n-hexyl iodide with quinoline and obtained 
a liquid mixture boiling from 35° to 67°. On oxidizing the fraction 
boiling from 63.6° to 65° they obtained a mixture of butyric and 
valeric acids indicating that this hexene fraction was probably a mix- 
ture of the a and p-isomers. Van Beresteyn ^^^ also obtained a hexene 
boiling at 67.7° to 68.1° by decomposing n-heptyl alcohol by heating 
in contact with nickel at 220°. 

CH3(CH2)3CH2CH2CH,OH-» CH3(CH,)3CH = CH^ ? + CO + 2H2 

However, von Braun ^*^ obtained a hexene, by gently heating n-hexyl 
trimethyl ammonium hydroxide, which showed a boiling-point of 62° 
to 63° and which he regarded as a-hexene, although he was unable to 
prove the constitution of it on account of the small quantity made. 
Brooks and Humphrey ^*^ confirmed the character of von Braun's 
a-hexene by synthesizing it by means of a reaction which had been 
applied by Tiffeneau "* to the synthesis of allyl derivatives of ben- 

'"Ann. m, 305 (1875). 

""Ohem. Zentr. 79, II, 1854 (1908). 

'"IMd. 1911, II, 1017. 

"'Ann. S82, 22 (1911). 

"^J. Am. Chem. Soc. J,0, 833 (1918). 

^"Compt. rend. 139, 481 (1904). 



152 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

zene."^ They treated n-propyl magnesium bromide with allyl bromide, 
the reaction taking place smoothly at room temperature. 

CsH.MgBr + BrCH,CH = CH^ -^ CsH.CH.CH = CH^ + MgBr, 

CH3 

Iso-a-heptene, >CH.CH2CHaCH = CH, and iso-a-octene were 

CH3 

also made in a similar manner. This reaction is undoubtedly appli- 
cable to the preparation of a large number of alpha olefines of this 
series. 

Pure olefines of other types may be prepared in certain cases by 
making use of the symmetry of the parent alcohol or halide. For ex- 
ample, the tertiary alcohol triethylcarbinol readily yields pure y-ethyl- 
P-pentene (3-ethyl pentene-2). 

CgHg C2H5 

C,.H3 — C — OH > C„H-C 

I " li 

CjHj CH . CH3 

and 8-iodo heptane, C3H- — CHI — C3H,, by virtue of its symmetry, 
yields pure y-heptene when decomposed by caustic alkali. 

The simpler primary alkyl chlorides and bromides on treatment 
with caustic alkali in methyl or ethyl alcohol yield chiefly methyl or 
ethyl ethers but alkyl iodides of five or more carbon atoms, particu- 
larly secondary and tertiary derivatives, yield olefines almost quanti- 
tatively.^*' 

Organic bases, aniline, quinoline and the like have frequently been 
employed to remove halogens with success. Tertiary halides, like ter- 
tiary alcohols, are easily decomposed and Klages ^" has employed pyri- 
dine for tertiary chlorides. Decomposition of alkyl halides by heat is 
usually attended by rearrangements and often with rupture of the car- 
bon structure, and, in some cases, by condensation or polymerization, 
but many substances catalyze this decomposition of the halides, so 
that lower temperatures may be employed and subsequent changes of 
the olefines may be minimized. Nearly quantitative yields of ethylene 

"^ Austerweil later synthesized isoprenes in a similar way, treating vinyl-magne- 
sium bromide with beta-chloropropvlene, 

/ CH = CHa /CI / CH = CH2 

Mg + CH3C » MgBrCl + CH3C 

\ Br \ CH2 \ CHa 

J. Cltem. Soc. Ais. 102, 525 (1912). 

"«Nef, Ann. 309, KB (1S99) ; SIS, 1 (1901). 
"'Ber. S5, 2633 (1902). 



THE ETHYLENE BOND 153 

may be obtained from ethyl chloride by heating in contact with barium 
chloride and chloropentanes can be decomposed to amylenes in this 
manner.^** A large number of processes for the decomposition of bornyl 
chloride to camphene have been described in connection with the syn- 
thesis of camphor. Bornyl chloride is remarkably stable and most of 
the successful reactions are carried out withiri the range 160° to 190°. 
Usually an alkaline substance or mixture is sought which will dissolve 
the bornyl chloride forming a homogenous reaction mixture and pat- 
ented methods refer to the use of sodium phenolate, sodium soaps such 
as oleate, linoleate, etc., sodium acetate in acetic acid, aniline, quino- 
line, etc. Zinc chloride catalyzes the decomposition of bornyl chloride 
but rapidly polymerizes the camphene formed. 

Certain defines are often most readily made by the decomposition 
of halogenated, hydroxy or unsaturated fatty acids but these methods 
are by no means generally applicable. Pure p-butylene is easily made 
from bromotiglic acid by heating with soda in aqueous solution.^*" 
CH3 

/ 

CHgCHBrCH > CH3CH = CHCH3 + CO^ + NaBr 

\ 

CO.Na 

The p-halogen derivatives of the fatty acids are decomposed very 
easily by alkalies and the resulting unsaturated acids frequently lose 
CO2 on heating or distilling to give an olefine. (3-bromoisobutyric acid 
is quantitatively decomposed by aqueous barium hydroxide to methyl 

CH3 CH3 

\ \ 

acrylic acid, CH . CO,H > C . CO.,H and a-bromo- 

/ " / " 

CH^Br CH2 

butyric acid, considerably more stable, also yields methyl acrylic acid 
by treating with 25% caustic soda.^^" Normal (3-bromo fatty acids on 
heating with water, dilute alkali, or by destructive distillation, yield 
more of the a-p-unsaturated acid than the p-y-unsaturated acid. 
Wallach ^" has made use of the instability of the P-hydroxy acids to 

"•Badische, German Pat. 255,519, J. Chem. Soc. 101,, 438 (1913); German Pat. 
268,100, Chem. Zentr. 191J,, I, 308; Sabatier & Mailhe, J. Chem. Soc. 101,, 330 (1913) ; 
Braun and Deutsch, Ber. J,s, 1271 (1912). 

According to Mathews, Bliss and Elder, the decomposition of alkyl halides within 
the range 100°-700* is catalyzed by water, either in the presence or absence of other 
catalysts. Brit. Pat. 16,828 (1912) ; 17,234 (1912). 

"• Pagenstecher, Ann. 195, 112 (1879). 

""Engehorn, Ann. 200, 68 (1880) ; Bischoff, Ber. ii, 1041 (1891). 

'"Ann. S6S, 257 (1909). 



154 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

synthesize olefines containing the methene group. Using the method of 
Reformatsky of condensing ketones or aldehydes with bromoacetic 
ester by means of zinc, Wallach proceeded as indicated by the follow- 
ing reactions, the hydroxy acids being dehydrated by heating with 
acetic anhydride. 



--CH 
I 
COH 




and from nopinone p-pinene was synthesized, 





CH^CO^H 





CH,\ 
' C-CHCO^H ^ 



Tertiary alcohols decompose so readily that they are difficult to 
acetylate. Glacial acetic acid at 150° to 155°, or acetic anhydride con- 
taining a little zinc chloride, or sulfuric acid, yields chiefly unsaturated 
hydrocarbon. Thus trimethyl carbinol yields isobutylene,^^^ diethyl- 
propylcarbinol yields an octene,^^^ etc. 

Primary and secondary alcohols of high molecular weight may be 
converted to olefines by the method of Krafft,^^* i. e., treating with 
palmityl chloride and distilling the palmitic ester slowly at ordinary 
pressure. In the terpene series the method developed by Tschugaeff ^^^ 
consisting in heating the methylxanthogenate ester of the alcohol, has 
given excellent results. Very little heat is usually required and the 
probability of rearrangement or decomposition is greatly lessened; in 
fact, the methylxanthogenate esters of tertiary alcohols, if formed, de- 
compose spontaneously at ordinary temperatures. Henderson ^''^ pre- 

>" Menscliutkin, Ann. 197, 204 (18Y9). 

""Mason, vompt. rend. Ui, 483 (1901); Henry, Compt. rend. U,!,, 5D2 (1907); 
U7, 1260 (1908). 

^'^ Ber. IS, 3020 (1883). 
"=Ber. Si, 3332 (1899). 
»"■/. Chem. Soc. 97, 1020 (1910) ; 99, 1903 (1911). 



THE ETHYLENE BOND 155 

pared very pure bornylene from the methylxanthogenate ester of bor- 
neol. 

Heating primary or secondary alcohols with mineral acids rarely 
gives good results except with the simpler members, as in the well- 
known methods of preparing ethylene and propylene, using sulfuric or 
phosphoric acids. Wallach showed that concentrated formic acid ^^^ 
or oxalic acid ^°* give better results in the terpene series than mineral 
acids. Potassium acid sulfate has been employed with good results, as 
in the conversion of borneol, which is relatively quite stable, to cam- 
phene.^^' When potassium acid sulfate or phosphorus pentoxide is used 
to dehydrate cyclohexanol-1-acetic acid, cited above, the resulting 
product is A^' '' cyclohexene acetic acid instead of the A^<^> acid which is 
obtained with acetic anhydride. 

Sabatier and Mailhe ^^° have shown that phosphorus, carbon, anhy- 
drous calcium sulfate, basic aluminum sulfate and many metallic oxides 
promote the dehydration of alcohols. The corresponding define hydro- 
carbon is usually produced, although alumina at 210° causes some ether 
to be formed. Ipatiev found that under higher pressures the formation 
of ether was considerably increased. Baskerville was unable to detect 
ether in ethylene resulting from the decomposition of alcohol in con- 
tact with thoria at temperatures as low as 250°.^°^ Sabatier and 
Mailhe studied a series of catalysts and, within the temperature 
range 300°-350°, ethyl alcohol gave varying yields of ethylene and 
hydrogen, the latter being formed together with acetaldehyde, 

CH3CH2OH > CH3CHO + H^. Thoria, alumina and blue oxide 

of tungsten at 340°-350° gave practically quantitative yields of ethyl- 
ene and the other catalysts gave the results indicated in the following 
table: 

Per cent ethylene 

ThOi 100. 

AljOa 98.5 

WiOa 98.5 

Cr^Oa 91. 

SiO. 84. 

TiOa 63. 

BeO 45. 

Zr02 45. 

UsOs 24. 

M02O5 23. 

FeA 14. 

ViOa 9. 

ZnO 5. 

^" Ann. g91, 361 (1896) ; 356, 243 (1907). 

"'Ann. ars, 106 (1893). 

■"Wallach, Ann. 230, 239 (1885). 

'"Ann. Ohim. Phys. nil. BO, 289 (1910). 

'"J. Am. Chem. Soo. 35, 93 (1913). 



Dehydration and 
dehydrogenation 



156 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

SnO 0. i 

CdO 0. 

MgO 0. )■ Dehydrogenation 

Cu 0. 

Ni 0. J 

Engelder "^ showed that in the presence of AI2O3, SiOa, ZrOj and 
TiOj the equilibrium, alcohol <:± water -\- ethylene, could be displaced 
by the addition of water vapor to the incoming alcohol. Kaolin within 
the range 350°-400° is particularly efficient in producing ethylene.^"*^ 
Ipatiev, prior to the work of Sabatier and Mailhe quoted above, had 
shown the wide applicability of alumina as a dehydrating catalyst.^"^ 
He prepared isobutylene and pure propylene, using alumina as a cat- 
alyst and butylene has been made from n . butyl alcohol, on an indus- 
trial scale, by the same method. ^"^ Senderens found that amorphous 
silica is much more active than ground quartz and aluminum phos- 
phate is also an excellent catalyst; Senderens obtained noteworthy re- 
sults by decomposing cyclohexanol at 300°, to cyclohexene and men- 
thol to menthene.^^" Pinacone gives excellent yields of dimethylbuta- 
diene when passed over alumina at 450°, but the best yields are ob- 
tained in vacuo}^'' 

The decomposition of tertiary amines has been employed as a 
laboratory method but the preparation of these amines is compara- 
tively costly and difficult though several processes for the preparation 
of dienes, leading to the synthesis of rubber, which involve this ter- 
tiary amine method, have been patented."' As pointed out above, the 
decomposition of the tertiary, amines usually takes place at compara- 
tively low temperatures, thus lessening the probability of decompo- 
sition or rearrangement of the resulting define. Willstatter and 
Schmaedel,^'^ made cyclobutene in this way. 



CH3 — CH — NH,- 


-^CH, — CH- 


-N(CH3)3 


CH, — CH 


CH, — CH, 


CH, — CH, 


Air 


1 1! 

CH, — CH 



+ N(CH3)3 + H,0 
The Grignard reaction has sometimes been applied to the synthesis 
of defines in ways other than noted above. In rare instances the Grig- 

"'J. Phys. Chem. 21, 676 (1917). 

"" The activity of tliese catalysts Is gradually diminislied as they become impreg- 
nated with carbon, evidently formed by the decomposition of ethylene to methane -and 
carbon. 

'"Ber. S6, 1997 (1903) ; S^, 596, 3579 (1901). 

'•'Newman, Cam. Chem. J. 1920, 47; King, J. Chem,. Soc. 115, 1404 (1919). 

'"Comvt. rend, m, 1109 (1907) ; MO, 125 (1908) ; Bayer & Co. Brit. Pat. 4,076 
(1913) . 

'"Badische, French Pat. 417,275 (1910). 

'"J. Chem. Soc. 102, I, 821 (1912). 

'"Ber. 38, 1992 (1903). 



THE ETHYLENE BOND 



157 



OMgX 
nard complex RC< breaks down spontaneously, but heat is 

R, 
usually required to effect decomposition to the olefine.^'" 

The decomposition of hydrocarbons by heat has not been employed 
for the preparation of pure defines, but it is well known that the pyro- 
lytic products of paraffine, petroleum oils and the like are rich in 
olefines. Pressure, as in distillation of heavy oils under pressure, di- 
minishes the proportion of olefines in the product and decomposition by 
heat under vacuum increases the proportion of olefines. Dilution of the 
original hydrocarbon vapors with an inert gas or steam also has this 
effect."! 

The reduction of the ketone group to the CHj group, in the pres- 
ence of a cyclopropane ring or unsaturated bonds of the ethylene type 
and without reducing these double bonds, may, in certain instances, be 
accomplished by forming the hydrazine derivative of the ketone and 
then decomposing this by solid caustic potash. Thus carone gives 
carane, without rupture of the cyclopropane ring, and ionone yields the 
corresponding unsaturated hydrocarbon.^" 
Cm, 




/•■ 



^ CH=CH 
I 
C=N.NH. 



""Harriea & Weil, Ann. StS, 363 (1905) ; Klages, Ber. S9, 2306 (1906) ; Barbier & 
Locquin, Chem. Zentr. 1913, II, 28. 

"■ Greenstreet, U. S. Pat. 1,110,925. 

"'Kishner, J. Buas. Phya.-Chem. Soc. 1^, 1398, 1563 (1911). 




Chapter V. Acyclic Unsaturated 
Hydrocarbons. 

Remarkably few hydrocarbons of this series are known. Many 
which have been described are undoubtedly mixtures and the constitu- 
tions assigned to many of them are undoubtedly incorrect. This is 
particularly true of olefines of the type RCHjCH = CHj. The simpler 
olefines are very reactive and the most promising outlook for the 
chemical utilization of petroleum is undoubtedly in the direction of 
these simpler olefines, including the gaseous olefines, ethylene and 
propylene, and the low boiling highly reactive olefines such as the 
butylenes, amylenes and hexylenes. 

Ethylene 

One liter of ethylene under standard conditions weighs 1.2519 
grams.^ Its boiling point at 760 mm. according to Cailletet ^ is — 105° 
and according to Ladenburg and Kriigel ^ is — 105.4° ; Burrell and 
Robertson * give — 103.9° as the boiling-point. Its melting-point is 
— 169°. Its critical temperature is 9.5° ± 0.1, critical pressure 50.65 
± 0.1 atmospheres.^ Its heat of combustion is stated to be 333,350 
and 341,400 calories (Thomsen") and 345,800 calories (Mixter^- 
Data on the compressibility of ethylene and the extent of its deviation 
from the behavior of a perfect gas under pressure at ordinary atmos- 
pheric temperature have recently been published, compressed ethylene, 
in steel cylinders, for welding and cutting now being commercially 
available.* 

Water at 0° dissolves approximately 0.25% ethylene. The gas is 
markedly soluble in ammoniacal cuprous chloride, but not in am- 

'Cf. Mallsoff & Bgloff, J. Pfms. Ohem. 2S, 65 (1919). 
' Compt. rend. W,, 1224 (1882). 

• Ber. S2, 1818 (1899). 

*J. Am. Chem. Soc. SI, 1893 (1915). 
'J. Chim. Pivys. 10, 504 (1913). 

• Thermochem, Unters, 4, 64. 
■•Am. J. Bci. (4), 1,, 51 (1897). 

'According to British Patents 146,332 and 147,051 (1920), ethylene may be 
separated from coal gas or oil gas by passing the gas through a series of absorbent 
materials at low temperatures. 

158 




^00 



looo 



is-00 looo ifoo 3000 3S'ao 



fom 



Pressure. Poun<i6 per so^Jnch 

Compressibility of Ethylene. 



159 



160 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

moniacal silver chloride. Ethylene is also markedly soluble in pe- 
troleum oils under moderate pressures; oil gas scrubbed with pe- 
troleum oils under pressures of 50 to 150 pounds loses by solution in 
the oil much more ethylene and propylene than corresponds to the 
partial pressure of these olefines in the gas mixture. On removing 
the pressure on the oil solution, gas is liberated which is much richer 
in olefines than the original. 

Ethylene is most easily made by passing ethyl alcohol over kaolin 
at 350° to 400°. Ethylene was made by this method on a large scale, 
during the late war.' When ethyl alcohol is passed over metals at 
elevated temperatures various amounts of acetaldehyde are formed. 
Zinc dust at 550° gives a 50% yield of ethylene. Ipatiev ^° used fire 
clay and alumina with excellent results and Engelder^^ states that 
with alumina at 350° the resulting gas contains 98.5% ethylene. 
Sprent^^ gives a slightly higher figure as the best working tempera- 
ture when using alumina, i. e., 360°. This method of preparing ethyl- 
ene is intimately connected with the stability of ethylene to heat and 
the presence of various contact substances. As pointed out by Bone 
and Coward ^^ the importance of the time factor on the character and 
proportions of the products resulting from the passage of substances 
through hot tubes has frequently been overlooked. Ethylene is very 
rapidly decomposed in contact with nickel at 300°, carbon, ethane, 
methane and hydrogen being formed. This decomposition is much 
slower, in contact with iron, but is quite rapid above 350°, but ac- 
cording to Ipatiev polymerization occurs in the presence of iron or cop- 
per at 400°-450°. In the absence of catalysts such as nickel, no hy- 
drogen is formed from ethane at 450°. According to Day " ethylene 
appears to be very slowly condensed at 350° to 400°, the residual gas 
containing methane and ethane. According to the early researches of 
Berthelot, ethylene condenses with benzene to form anthracene when 
the two hydrocarbons are passed together through a red-hot tube. 
This reaction has recently been examined by Zanetti and Kandell,^° 
who find that the maximum yields of anthracene are obtained at 900° 
to 925° C. 

Numerous attempts have been made to prepare ethylene by partial 

'Norris, J. Ind. & Eng. Chem. 11, 817 (1919). 

"Ber. S5. 1047 (1902); S6, 1990 (1903). 

"J. Pliys. Chem. 21, 676 (1917). 

"■/. Boc. Chem. Ind. 32, 171 (1913). 

''Rep. Brit. Assoc. 1915, 368; Soc. 9S, 1197 (1908). 

"Am. Chem. J. S, 153 (1886). 

"J. Ind. & Eng. Chem. 13, 208 (1921). 



ACYCLIC UNSATURATED HYDROCARBONS 161 

hydrogenation of acetylene, but so far, without commercial success. 
Karo^^ and others^' state that 90 to 95% conversion to ethylene can 
be effected in the presence of active nickel at about 100°. Ethylene, 
itself, is very rapidly hydrogenated to ethane in the presence of nickel 
at 150°. The activity of nickel is quickly impaired by the separation 
of carbon and copper is not very effective, but the change is rapid in 
the presence of platinum black at 185°, and aqueous colloidal plati- 
num or palladinum effect rapid reaction at room temperature.^® In 
this, as in many similar reactions in which gas and liquid phases are 
concerned, the rate of solution of the gas is the chief time controlling 
factor. During the war this problem was investigated in the labora- 
tory at Edgewood Arsenal, on account of the importance of ethylene 
in the manufacture of "mustard gas." The process was evidently not 
carried out on an industrial scale but it was ascertained that in the 
presence of catalytic nickel prepared by reduction at 300°, both ace- 
tylene and ethylene are hydrogenated at temperatures as low as — 10°. 
No deposition of carbon on the catalyst was noticed when the reaction 
was carried out at room temperatures. Gas mixtures containing ap- 
proximately 80% ethylene were obtained, the remaining gas consist- 
ing of ethane, nitrogen and a little acetylene. 

Ethylene is a minor product in the electrolysis of salts such as ace- 
tates, malonates and succinates: it can be made from ethylene bromide 
by Gladstone's copper-zinc couple, and certain metallic carbides react 
with water to give small proportions of ethylene (barium carbide and 
silicide mixture yields a gas containing 15% ethylene). But the only 
method, other than the hot kaolin method, which is of preparative 
value, is the old familiar laboratory method of passing alcohol vapor 
into hot sulfuric or phosphoric acid. In this method of preparation a 
small proportion of hydrocarbon oil is always noticed in the wash bot- 
tles, and this oil is probably a condensation product or polymer of 
ethylene.^" Thus zinc chloride at 275° converts ethylene into an oily 
polymer of specific gravity (15°) 0.751 and anhydrous aluminum chlo- 
ride effects a similar change at room temperature. 

Ethylene may be oxidized without great difficulty to formaldehyde, 

"Karo, Ger. Pat. 253,l(i0 (1911) ; Rabatier & Senderens, Oompt. rend. 128, 1173 
(1899) ; ISO, 1559, 1628 (1900) ; m, 40, 187 (1900) ; Paal, Ber. i8, 275 (1915) ; Paal & 
Schwarz, Ber. SI, 640 (1918), claim that colloidal palladium gives the best results. A 
particularly important paper has Just appeared by Ross, Culbertson and Parsons, J. 
Ind. <£■ Eng. Chem. U, 775 (1921). 

"Lane, Ryberg & Kinberg, Ger. Pat. 262,541 (1913). 

'" Sabatier & Senderens, Compt. rend. Ml, 40 (1900) ; Paal & Hartman, Ber. ^2, 
2239 (1909) ; 1,8, 994 (1915). 

"MontmoUin [Bull. Soc. cMm. (4), 19, 242 (1916)] has examined this oil mixture 
and states that it consists chiefly of alkylated naphthenes. 



162 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

oxalic and acetic acids, glycol, formic acid, etc., but these oxidation 
products are themselves oxidized more rapidly than ethylene. The 
major products of the oxidation of ethylene are, therefore, usually CO2 
and water and large yields of intermediate products are not to be ex- 
pected. 

At 400° with insufficient oxygen for complete combustion, a little 
formaldehyde is formed.^" With equal volumes of oxygen, carbon 
monoxide and hydrogen are produced ; with less than an equal volume 
of oxygen Lean and Bone ^^ believed two reactions to be involved, 

C^H^ > CH, + C 

2C,H, + 0, > 2CH, + 2C0 

Bone and Wheeler ^^ studied the oxidation of ethylene by oxygen 
at temperatures within the range 250° to 400°, but according to a re- 
cent paper by Willstatter ^^ the oxidation to formaldehyde is not rapid 
below 500°. As shown by F. C. Phillips, combustion of ethylene takes 
place at lower temperatures in the presence of osmium than with other 
catalytic surfaces and Willstatter finds that in the presence of this 
metal oxidation of ethylene begins at 130°, carbon dioxide and water 
being practically the only products. In the presence of copper or silver 
practically no formaldehyde is produced, and in the case of copper oxi- 
dation is fairly rapid at 250°. Willstatter made use of the observation 
that when ethylene is diluted with an inert gas the thermal decompo- 
sition of the ethylene itself is greatly reduced. Metallic surfaces cat- 
alyse the thermal decomposition of ethylene and Willstatter accord- 
ingly obtained the best yields of formaldehyde by operating without a 
catalyst at about 585°, using a gas mixture containing 19.38 per cent 
ethylene and 7.58 per cent oxygen. Under these conditions he ob- 
tained approximately 50 per cent of the theory of formaldehyde. 

Ozone reacts vigorously with ethylene,^* an explosive compound 
being formed. In the presence of. water formaldehyde, formic acid, 
carbon monoxide and hydrogen peroxide are among the reaction prod- 
ucts. 

Ethylene and oxygen in sunlight at ordinary temperatures do not 
react but under the influence of ultraviolet light, oxidation to CO2, CO 

»>Nef, Ann. S98, 202 (1899). 
»J. Chem. 8oc. m, 144 (1892). 
»=J. Chem. Boo. 8S. 1074 (1903). 
"Ann. m, 36 (1921). 
"Harries, Ann. Sni,, 288 (1910). 



ACYCLIC UNSATURATED HYDROCARBONS 163 

and formic acid results.^^ According to Taylor ^° ethylene and oxygen 
react at ordinary temperatures in the presence of activated charcoal. 
Chromic acid oxidizes ethylene, with difficulty to CO2, formic and 
acetic acids.^^ Potassium permanganate in dilute sulfuric acid yields 
CO2, formic and acetic acids, but neutral or alkaline permanganate 
yields glycol and oxalic acid.^* 

Ethylene combines directly with a large number of substances and 
while many of these reactions have been known for a great many 
years, a few of them have become industrially important only within 
very recent years. Ethylene chlorohydrin was made by Carius ^^ and 
others by treating ethylene with dilute aqueous hypochlorous acid. 
Gomberg ^^ has recently shown that the reaction of ethylene and hypo- 
chlorous acid takes place so rapidly that practically quantitative yields 
of the chlorohydrin are obtained by agitating ethylene with cold chlor- 
ine water, although free chlorine is ^also present. Methods suit- 
able for large scale manufacture of ethylene and propylene chlo- 
rohydrins, using chlorine and cold aqueous solutions of sodium car- 
bonate or bicarbonate, have recently been described.^?- Ethylene bro- 
mohydrin has recently been made by passing ethylene and bromine 
vapor separately into ice water, keeping the concentration of the bro- 
mine in the solution very low.^^ The bromohydrin had previously been 
made by the action of HBr on ethylene glycol or by the action of PBrj 
on the glycol. The bromohydrin boils with slight decomposition, at 
146°-150° and has a density, 20°, of 1.7629. 

Ethylene chlorohydrin reacts with sodium azide, the chlorine being 
replaced by the triazo group.'^ (Vinyl bromide does not react with 
sodium azide.) By converting the triazoethyl alcohol to the bromide 
and replacing the bromine with iodine, the resulting triazoiodine deri- 
vative can be decomposed by alkali, removing HI and yielding triazo- 
ethylene. The boiling-point of triazoethylene is 26°, or 10° higher than 
the corresponding bromide CHj = CHBr. 

CH.Cl CH.Ng CH.Ng CHN3 

I +NaN3 .1 >\ ' >|| 

CHOH CH2OH CHJ CH, 

=» Berthelot and Gaudechon, Compt. rend. 150, 1327 (1910). 

" TroMs. Am. ElectrocJiem. Soc. 1919, 167. 

"'Chapman & Thorpe, Ann. m, 182 (1867); Othmar & Feidler, Ann. 197, 243 
(1879). 

"Ann. 150, 373 (1869) ; Ber. 21, 1234 (1888). Cf. Evans on oxidation of ethylene 
glycol by permanganate, J. Am. Chem. Soc. it, 1385 (1919). 

"Ann. 126, 197 (1863) ; Butlerow, Ann. m, 40 (1867). 

"J. Am. Chem. Soc. il, 1414 (1919). 

"■Brooks, Chem. d Met. Eng. 22, 629 (1920). 

"Read & Hook, J. Ghem. Soc. 117, 1214 (1920). 

"Forster & Newman, J. Chem. Soc. 97, 2570 (1910). 



164 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Ethylene chlorohydrin gave promise of becoming of some impor- 
tance during the recent war, as an intermediate in the manufacture 
of dichloroethyl sulfide (mustard gas) , but another reaction of ethylene, 
i. e., its reaction with sulfur chloride, first discovered by Guthrie,^* 
proved to be more suited to large scale production and was adopted in 
all the Allied countries. The experimental conditions, of which Guth- 
rie's work gave little more than a hint, were worked out by Pope ^° and 
the large scale operations worked out by Levinstein. Gibson and 
Pope ^^ showed that when the reaction between ethylene and sulfur 
chloride is carried out above 70° considerable decomposition occurs 
and Pope and his assistants showed in a later paper ^' that practically 
quantitative yields are obtained when the ethylene contains a little 
alcohol vapor but when pure ethylene is employed the product is not so 
pure, thus explaining the discrepancies reported by other workers. The 
sulfur liberated in the reaction appears to be retained largely in a 
colloidal condition and may be separated by dissolving the dichloro 
sulfide in kerosene and then separating the mustard gas from the 
kerosene solution by chilling. Distillation in vacuo readily yields pure 
P|3-dichloroethyl sulfide. In Germany the chlorohydrin method of 
making mustard gas was employed. 

Ethylene reacts with selenium monochloride ^' to give free selenium 
and the product ClaSelCH^CHaCl)^. 

The reactions of the two manufacturing processes for mustard gas 
are as follows: 

(1) CH^ CH^ — OH 

II +H0C1 > I 

CHj CHj — CI 

2CH,0H CH,OH CH.OH 

I + Na,S > I I 

CH^Cl CH3-S-CH3 

CH3OH CH^OH CH^Cl CH^Cl 



+ 2HC1 ■ 



CH3 S CH, CH,— S — CH^ 

CH, CH.Cl CH,C1 

(2) 2 II +S,C1, 



— ^ I I > 

CHo CH2 Sj CHj 

"Ann. 119, 91 (1861) ; 121, 108 (1862). 

"J. Soc. Chem. Ind. 3S, 344R, 434E (1919) ; Green, J. 8oo. Chem. Ind. SB, 363R, 
469R (1919). 

"J. Chem. Soc. 117, 271 (1920). 

",/. Chem. Soc. 119, 634 (1921). 

" Bausor, Gibson & Pope, J. Chem. 8oe. in, 1433 (1920) ; Heath & Semen. /. Ind. 
d Eng. Chem. 12, 1100 (1920). 



ACYCLIC UNSATURATED HYDROCARBONS 165 

CH.Cl CH.Cl 

CH, S CH, 



ir +' 



Phosgene reacts with ethylene under the influence of light as fol- 
lows.'^ 

CHg CHjCl 

II +COCI2 > I (Chloropropionyl chloride) . 

CH3 CH2COCI 

Norris and Couch *" have shown that benzoyl chloride reacts with 
ethylene in the presence of anhydrous aluminum chloride to give phenyl 
vinyl ketone, a reaction probably capable of considerably wider appli- 
cation. Ethylene is readily absorbed by anhydrous aluminum chloride 
and benzene to form mono- and poly-substituted ethyl benzenes.*^ 

Chlorine and bromine*^ react smoothly with ethylene to give the 
symmetrical dihalides. The addition of chlorine to ethylene to form 
ethylene chloride or "Dutch liquid" was first carried out in 1796 and 
Faraday later treated oil gas *^ with chlorine obtaining ethylene chlo- 
ride together with other chlorinated products. Although this reaction 
has been known since this early date, no very thorough study of it has 
been made. Dry chlorine and ethylene react exceedingly slowly. Ethyl- 
ene passed into chlorine water yields ethylene chlorohydrin almost 
exclusively; cold dilute bromine water yields both ethylene bromide 
and ethylene bromohydrin. In chlorinating ethylene, it is difficult to 
limit the chlorination to the dichloride, trichloroethane and still more 
highly chlorinated products being formed. The introduction of ethyl- 
ene into liquid chlorine in the cold, under pressure, gives excellent 
fields of ethylene chloride,** and chlorination in the presence of char- 
coal, alumina or other very porous material is stated to give good 
yields.*' Another patentee employs solid calcium chloride as a cat- 
alyst.*" Higher olefines, amylenes and hexylenes, yield dichlorides when 
treated with sulfuryl chloride below 30°.*^ When chlorine is absorbed 
in cold bromine in the proportions required by the hypothetical sub- 

"Uppman, Ann. 129, 81 (1864). 

"J. Am. Chem. Soc. iS, 2330 (1920). 

"Balsohn, Bull. Soc. chim. (2), si, 529 (1879). 

** According to Plotnikov, Oliem. A'ba, 1917, 48, ethylene and bromine react even 
at — 80° in the dark. 

" The oil gas used by Faraday was probably made from fatty oils, which, however, 
closely resembles oil gas made from mineral oils in its general character. 

" Curme, U. S. Pat. 1,315,545 ; 1,315,547. 

"Harding, Brit. Pat. 126,511 (1918). 

"Smythe, Oaa. J. 1J,9, 691 (1920). A yield of 50% ethylene chloride by this 
method Is reported. 

" Badische Co., J. Soo. Chem. Ind. 131$, 151. 



166 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

stance BrCI and ethylene is then introduced, the principal product is 
CHaCl.CHjBr, which appears to be the only real evidence of the ex- 
istence of the compound Cl.Br."^ Bromine has practically no action 
on ethylene bromide. Iodine reacts slowly with ethylene in direct 
sunlight or on heating to 60°.^' 

Iodine monochloride and ethylene yields ethylene chloride and free 
iodine. Concentrated hydriodic and hydrobromic acids combine slowly 
with ethylene at 100°. 

Boron trifluoride reacts with ethylene forming the product CjIIgBFj 
boiling at 125°.='' 

The reaction of sulfuric acid and the simpler gaseous olefines has 
recently become a matter of industrial interest since the alkyl sulfates 
may be saponified or hydrolyzed by steam to the corresponding alco- 
hols. As first described by Faraday °^ in 1827, the absorption of 
ethylene by concentrated sulfuric acid, with the formation of ethyl 
hydrogen sulfate, is not rapid below 160° and according to Butlerow " 
the absorption is rapid at 160°-170°. The question of an industrial 
synthesis of alcohol from gases containing ethylene was investigated in 
1855 by Berthelot == and later by P. Fritzsche ^* who states that 100 
kilos of concentrated acid are required to produce 18 kilos of alcohol. 
The chief difficulties have been the handling and re-concentration of 
relatively large quantities of sulfuric acid and loss of acid by oxidation 
and charring of other olefines, which were not completely removed 
prior to the absorption of ethylene. One patentee claims that vana- 
dium or uranium salts facilitate the absorption of ethylene. ^° Ferrous 
sulfate and cuprous salts are said to promote the absorption of ethyl- 
ene and under these conditions ^^ the gas is treated with acid at 100°- 
120°. Very recently. Bury and Ollander °' have carried out these re- 
actions on an industrial scale, in England, and state that one ton 
of Durham coal yields sufficient ethylene to produce 1.6 gallons of 95 
per cent ethyl alcohol. After removing benzene vapors and olefines other 
than ethylene, the gas is scrubbed by hot 95 per cent sulfuric acid and 
the resulting ethyl-hydrogen sulfate is hydrolyzed by steam. Since 

"DeWpine & Ville, Bull. Soc. cMm. Sn, 673 (1920). 

"Faraday, Phil: Trana. 18, 118; Regnault, Ann. d. Ohimie. (2), 53 (1835). 
"Landolt, Ber. m, 1586 (1879). 
'^Pogg, Ann. 9, 21 (1827). 
''Ber. e, 196 (1873). 

" Compt. rend. iO, 102 (1855) ; Ann. CMm. (3), iS, 385 (1855). 
"(Jftem. Ind. SO, 266 (1897) ; S5, 637 (1912). 

'" Lattre, French Pat. 468,244 ; J. Soc. Chem. Ind. 191i, 953 ; Loisy, Compt. rend, 
m, 50 (1920). 

"Brit. Pat. 152,495, J. Soc. Chem. Ind. S9, 833A (1920). 
"Brit. Pat. 147,360 (1914) ; Chem. Weelcilad. 11, 478 (1920). 



ACYCLIC UNSATURATED HYDROCARBONS 



167 



coal gas ordinarily contains not over 2.5 per cent ethylene, it would be 
reasonable to assume that such a process would be more successful 
with oil gas or waste gas from petroleum stills, particularly cracking 
or coking stills, gas from the latter source containing 5 to 6 per cent 
ethylene. Propylene and butylenes are absorbed by sulfuric acid at 
ordinary temperatures and according to Hunt °' and Ellis °° good yields 
of isopropyl and secondary butyl alcohols are obtainable in this way. 
By the Ellis process isopropyl alcohol is obtained from propylene con- 
tained in the gases from Burton stills used in cracking petroleum oils 
to make gasoline. The gases are allowed to bubble through cool sul- 
furic acid of specific gravity 1.8 until the gravity falls to 1.3 or 1.4. 

3S- 
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Absorption of Ethylene in Sulfuric Acid of Different Concentrations, 
at 50° and 100° C. 

The acid liquor is diluted with water and polymers, higher alcohols, 
etc., allowed to separate. The diluted liquid is distilled with steam. A 
small amount of olefines and propyl ether first appear in the distillate. 

's'Brlt. Pat. 146,956; 146,957 (1920). 

" Oil, Paint & Drug Rep. Dec. 20, 1920, p. 28. 



168 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Isopropyl alcohol then comes over. The rate of absorption of ethylene, 
in a small experimental apparatus, at 50° and 100°, is shown in the 
accompanying figures. These values are entirely empirical but give a 
good comparison of the absorption in acids of different concentration.'" 
The reaction of ethylene with mercury salts is well known through 
the work of Hoffman and Sand.^^ They conclude that the following 
types of salts are formed, to which they have given the names indi- 
cated, 

(1) Ethene mercury salts, CHaCH.HgX 

(2) Ethanol mercury salts, CHjOH 

CH.HgX 

(3) Ethyl ether mercury salts, XHgCjH.OC.H.HgX 

(4) Polymerized ethene mercury salts (CaHjHgX)^ 

They proposed the theory of the initial formation of CHjX 

CH,HgX, 

which by decomposing with loss of HX would give ethene compounds, 
or by reacting with water ethanol salts. Hydrochloric acid decom- 
poses all four types, liberating ethylene. 

Sand *^ later expressed the opinion that only two series of com- 
pounds are formed and stated that the fourth class, polymerized ethene 
mercury compounds, did not exist. Later writers have confirmed this 
view.*^ Manchot "* has shown that the ethanol compound CaHgOHgCl 
is monomolecular. In view of the ease with which cold dilute hydro- 
chloric acid liberates ethylene from this ethanol compound, not 
CH3CH2OH, as the Sand structure would lead one to expect, Manchot 

OH 
favors the structure C2H^Hg< the ethylene group being held in 

CI, 
combination in some manner analogous to the way CO is combined 
with cuprous chloride. Manchot explains the stability of the mercury 
ethanol compound towards nitric and acetic acids and its reactivity 
to hydrochloric acid by the theory that mercuric chloride is capable 
of forming the double compound, HgClj . 2HC1. The equations for its 
decomposition by HCl would then be expressed as follows: 

"Plant and Sidgwlck, J. Soc. Chem. Ind. 1921, 14T. 
"^Ber. S3, 1340, 2692 (1900); Si, 1385 (1901). 
"Ber. Sh 1385 (1901). 
"Manchot, Ann. po, 174 (1920). 
"Loc. dt. 



ACYCLIC UNSATURATED HYDROCARBONS 169 

OH 

(1) C,H,Hg< +HCl*^C,H,HgCl, + H,0 

CI 

(2) C,H,HgCl, + 2HC1 fc? HgCl^, 2HC1 + C^H, 

The constitution of these compounds can hardly be regarded as defi- 
nitely determined. 

Curme '^ has described a method of separating ethylene in a pure 
condition from gas mixtures, which consists in absorbing the ethylene 
in a solution containing a mercury salt, such as mercuric sulfate, and 
subsequently heating the solution to expel the ethylene. 

CH^HgOAc 
With mercuric acetate in methyl alcohol the ether | is 

CH2OCH3 

formed.^' Manchot and Brand " state that ethylene forms a double 
compound with cuprous chloride. A double compound with platinum 
chloride, CjHiPtCla, is known,"* and concentrated aqueous ferrous 
bromide forms the crystalline compound C2HiFeBr2.2H20. Hender- 
son and Gangloff"" isolated double compounds with anhydrous alu- 
minum chloride (from absolute alcohol) having the formula AICI3. 
C2H,.2C2H,0H and AlCl3.C2H,.CH30H.H20. 

Propylene and Substituted Propylenes 

The best laboratory method for the preparation of propylene is the 
decomposition of isopropyl alcohol by passing over aluminum phos- 
phate or kaolin at about 300°.^° It is liquid under 7 to 8 atmospheres 
pressure and would probably be industrially valuable in this form. 
Propylene forms propanol mercury salts analogous to those of ethyl- 
ene; Curme ^^ describes the use of ethanol salts to separate pure ethyl- 
ene from inert gaseous diluents but the similar treatment of gaseous 
mixtures containing propylene has not been described. The source of 
propylene utilized by Ellis for the preparation of isopropyl alcohol 
by means of the sulfuric acid esters, is oil gas or petroleum still gas. 
Propylene may be separated from ethylene almost quantitatively by 
means of sulfuric acid (see above). 

•=TJ. S. Pat. 1,315,541 (1919). 

«« Schoeller, Schrauth & Essers, Ber. ie, 2864 (1913). 
"Ann. an, 286 (1909). 

MBirnbaum, Ann. 195, 69 (1868) : Zeise, Pogg. Ann. 21, 497,592; iO, 234 (1837). 
"J. Am. Chem. Soo. S8, 1382 (1916). 

™ Senderens, Compt. rend, m, 1110 (1907). The necessary isopropyl alcohol may 
be prepared by the reduction of acetone by sodium. 
"D. S. Pat. 1,315,541. 



170 CHEMISTRY OF THE NON-BEN ZENOID HYDROCARBONS 

The chemical properties of propylene are of interest as showing 
the marked difference in chemical behavior, as compared with ethylene, 
due to the introduction of a methyl group in ethylene. Whereas ethyl- 
ene passed through 98.1% sulfuric acid at 70° gives an increase in 
weight in 2.5 hours, of only 2.27 per cent, propylene at a much lower 
temperature, 25°, in the same apparatus and using 97% sulfuric acid, 
showed a gain in weight of 50 per cent in two hours.'^ Propylene re- 
acts with hypochlorous acid, to form the two chlorohydrines, more 
rapidly than ethylene, and in contrast with ethylene is absorbed by 
concentrated hydriodic acid in the cold;'^ it is also absorbed, though 
less rapidly, by concentrated hydrochloric and hydrobomic acid. 

The derivatives of propylene have been the despair of those who 
have sought to formulate simple rules for the addition of other sub- 
stances to the olefine group. Usually these rules have been based upon 
ideas of electrical polarity and an arrangement of the additive sub- 
stance which would supposedly satisfy best the balance of the forces 
of attraction and repulsion. A few examples will su£Bce to show the 
difficulty of forming generalizations which will hold true in this simple 
series. In reactions where two substances are formed the * indicates 
the principal product.'* 

CH3CH = CHCl + HBr -.[ gg^ggf™^;^ * 

CH3CCI = CU, + HI > CH3CCII.CH3 

CH3CCI = CH, + HBr > CH3CCI . Br . CH3 

CH,CI-CH = CH, + HBr . | ^i§\:2^^^6%' 

dark 
,CH3CH = CHCl + CU > CH.Cl . CH = CHCl 

light 

CH3CH = CHCl + CI2 > CH3CHCI.CHCI2 

dark 
CH3CCI = CH3 + CI2 > CH.Cl . CCl . = CH^ 

CH3CI . CCl = CH3 + HCl > CH.Cl . CC1,CH3 

CH3CH = CHBr + HBr . j '^n'^K^C^if' ' 

CH3C .Br = CH2 + HBr > CH3CBr,CH3 

CH.BrCH = CH. + HBr >j gg:gj:g™H':S 

"Plant & Si<}gwick, J. Soc. Chem.. Ind. ^0, 17 T. (1921). 

"Butlerow, Ann. Ii5, 275 (1868) ; Michael. J. prakt. Chem. (2), 60, 445 (1899). 

"Eeboul, Ann. Cliim. (5) u,, 461 (1878) ; Michael, Ber. 39, 2787 (1906). 



ACYCLIC UNSATURATED HYDROCARBONS 171 

PP'-dichloro-n-propyl sulfide, analogous to mustard gas, has been 
described by Coffey ,'' who obtained it easily from propylene chloro- 
hydrin by means of Clarke's'® modification of Victor Meyer's meth- 
od." Coffey was unable to make the dichloro sulfide from sulfur chlo- 
ride and propylene although in the case of ethylene the results leave 
little to be desired. With propylene, condensation to dark colored 
semi-solid material results, when the reaction is carried out at 50° to 
60°. 

The Butylenes and Amylenes: There are three butylenes, i. e., 
CH3 
CH3CH2CH = CH2, >C = CH2 and CH3CH = CHCH3, the lat- 

CH3 
ter hydrocarbon being known in cis and trans form,'' 

HC . CH3 HC . CH3 

HC . CH3 CII3C . H 

CIS, boiling-point 1 to 1.5° trans, boiling-point 2.5° 

When primary or secondary butyl alcohol or the corresponding 
halides are decomposed, all three butylenes are formed." The diffi- 
culty of preparing pure olefines has repeatedly been emphasized in 
these pages. The butylenes occur in oil gas, in the light liquid, con- 
densed under pressure, from Pintsch-gas, and in the fore runnings of 
the distillation of crude benzene, particularly when made by loW tem- 
perature carbonization of coal or from water gas tar. The butylenes 
are not at present utilized industrially. Their physical properties are 
very imperfectly known but their boiling points, as recorded, are as fol- 
lows, 

Butene- ( 1 ) , boiling-point — 5° 

Butene-(2), " " cis + 1 to 1.5°; trans -f- 2.5°. 

Isobutylene, " " —6°. 

Isobutylene can readily be prepared by dropping tertiary butyl 
iodide into boiling water, the hydriodic acid being retained by the 
water.^^ 

"J. Ohem. Soc. 119, 94 (1921). 

'•/. Chem. Soc. 101, 1583 (1912). 

" The writer experimented with this method, in cooperation with the TJ. S. Chem- 
ical War Service in 1917 and 1918, in the effort to utilize the ethylene and propylene 
in oil gas. The yields of the dichloro sulfide are good, in the case of propylene, but 
the product is much less toxic than the ethylene derivative. 

" Wislicenus, Ann. SIS, 228 (1900). 

"Faworski, J. prakt. chem. (2), 1,2, 153 (1890): Senderens, Compt. rend. 144, 
1110 (1907) ; Newman, Can. Chem. J. 1920, 47 and, King, J. Chem. Soc. 1919, 1404, 
describe the catalytic decomposition of n. butyl alcohol to butylene, which is then 
treated with 80% sulfuric acid to obtain secondary butyl alcohol, which in turn may 
be catalytlcally dehydrogenated to obtain methyl ethyl ketone. 

80 WlslicBnus Zoc dii 

"Nef, Arm. 'si8, 23 (1901) ; Cf. Ipatiev, Ber. V), 1829 (1907). 



172 CHEMISTRY OF THE NON-BENZENOID'HYDROCARBONS 

Isobutylene is rapidly dissolved by 70 per cent sulfuric acid in the 
cold; when such a solution made up with 50 per cent acid is warmed 
to 100° di-isobutylene CgHis is formed, and when acid of stronger 
concentration, 80 per cent, is employed tri-isobutylene is formed, illus- 
trating a very general behavior of olefines, i. e., that the more con- 
centrated the acid the fiurther the polymerization proceeds.'^ 

The butylenes form characteristic crystalline nitrosates, or rather 
6ts-nitrosates, when nitrogen peroxide, is passed into cold ether solu- 
tions f^ reduction of these nitrosates yields the corresponding diamines. 
Isobutylene reacts with acetyl chloride in the presence of zinc chloride 
to form a chloroketone.** 

CH3 CH3 

> C = CH^ + CH3COCI > > CCl . CH,C0CH3 

CH3 CH3 

which decomposes on heating to mesityl oxide. The above reaction 
is analogous to the reaction between ethylene and benzoyl chloride in 
the presence of anhydrous aluminum chloride, discovered by Norris 
and Couch.'^ As noted in connection with the action of sulfuric acid on 
olefines, the butylenes and amylenes are much more reactive than their 
higher homologues, and it is therefore probable that in the presence 
of aluminum chloride the rate of polymerization may greatly exceed 
that of condensation with other substances as in Norris's reaction. 
Very probably the higher olefines such as the decylenes will give bet- 
ter yields of condensation products, in the presence of aluminum chlo- 
ride, than butylene or amylenes. 

The amylenes have probably been more thoroughly studied than 
any of the olefines with the exception of certain of the terpenes. This 
is perhaps to be explained by the availability of the raw materials, 
amyl alcohol and petroleum pentane. Of the five possible amylenes, 
four are definitely known but pentene-(l) certainly never has been 
prepared in a pure state and it is doubtful if the material supposedly 
isolated by Brochet,*^ from the distillate of bog head coal, contained 
any of this hydrocarbon at all. It is also doubtful if pentene- (2) has 

"Butlerow, Ann. ISO, 247 (1876) ; 189, 48 (1877) ; Ber. 12, 1482 (1879) ; Brooks 
& Humphrey, J. Am. Cliem. Soc. 1,0, 822 (1918). 

" Ssiderenko, Chem. Zentr. 1907, I, 399. 

" Kondakow, J. Buss. Phys.-Chem. Soc. 26, 12 (1894). 

"J. Am. Chem. Soc. J,S, 2329 (1920). 

"Bull. chim. & Phys. (3), 7, 567 (1892) ; Wurtz, Ann. US, 136 (1868), and Wag- 
ner & Saizew, Ann. 179, 304 (1875), attempted to prepare this hydrocarbon by the 
reaction of allyllodide and zinc ethyl ; reaction of magnesium ethyl bromide and allyl 
bromide should yield this hydrocarbon in a pure state, analogous to the preparation 
of hexene-(l) by Brooks and Humphrey, J. Am. Chem. Soc. iO, 822 (1918). When 
this hydrocarbon Is prepared its boiling point, by analogy from the hexenes, will 
probably be found to be below 35° instead of 39°-40° as given by Brochet. 



ACYCLIC UNSATURATED HYDROCARBONS 



173 



been prepared in a fairly pure condition. It is idle therefore to com- 
pare the physical properties of these isomeric amylenes. The most 
stable of the amylenes is trimethylethylene and it is formed when any 
of the other amylenes are prepared at high temperatures. According 
to Ipatiev*^ 2-methylbutene-(3), is almost quantitatively converted 
into trimethylethylene by passing over heated alumina, 

>CH.CH = CH, > >C = CH.CH3 

CH3 CHj 

When ordinary amyl alcohol is passed over alumina at 340°-350° all 
three of the methylbutenes are formed, trimethylethylene being the 
principal product.** 

CH, 



CH, 



CH, 



\ 



CH.CH.CHaOH- 



\ 



CH3 
CH3 

CH3 

CH, 



/ 



CH.CH = CH, 



\ 



/ 



C = CH.CH, 



CH, 



\ 

( 



C.CH2CH3 



Commercial "amylene" is accordingly a mixture of these hydrocarbons 
containing trimethylethylene as the principal constituent. When such 
amylene is treated with 70 per cent sulfuric acid in the cold, the prin- 
cipal product is dimethylethylcarbinol, boiling at 102°. 
CH, 



\ 



CH^ 
CH, 



/ 



C.CH.CHg +H2O 



CH, 



\ 
C 



C^CH.CHj +H,0 



CH, 



\ 



. /I 
CH, OH 



C . CHjCHj 



"Ber. SB, 2004 (1903). 

"Senderens, Compt. rend, ni, 916 (1920). 



174 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Sulfuric acid in methyl alcohol and trimethylethylene gives the methyl 
ether.*' 

It is worthy of note, that most of the reactions of the amylenes are 
applicable to the terpenes, and vice versa. The chemical behavior of 
the two groups of hydrocarbons is entirely similar, but the use of the 
word "hydro-aromatic" for the cyclohexane derivatives has probably 
done a great deal to prevent the full realization of the similarity, one 
might say homogeneity, of the chemistry of the non-benzenoid hydro- 
carbons. For the purpose of emphasizing this similarity a number of 
reactions of amylenes and terpenes will be noted. 

(1) Addition of HCl and HBr (in acetic acid solution). 
CHj CH3 

\ \ 

C = CH.CH3 > C.CH.CHj 

/ / 

CHj CH, 




■3 -'2 -"3 

(2) Addition of nitrosyl chloride."" '^ 



CH3 



>C = CH.CH3 + N0C1- 



CH3 
-^ >C — CH.CH3 
CH, 



d 



CH, 



1 NO 

CH3 
I CI 



H, 



H + NOCI 



-^H 



/ 



in certain terpenes 

" Reychler, Chem. Zentr. 1307, I, 1125. 

•"J. Schmidt, Ber. S5, 3732 (1902) ; SB. 1765 (1908). 

•' WaUach, Ann. iiS, 245 (1888) ; Ber. Si, 1535 (1891). 



NO 

H 



< 



ACYCLIC UNSATURATED HYDROCARBOMS 175 

(3) Behavior of nitroso chlorides."^ 
Both amylenes and terpenes, 
■R,C — CHRT bimolecular, T R,C — CR 



[R^C — CHR"j bimolecular, "I 

CI NO J2 crystalline J 



CI N.OH 
monomolecular 



(4) Behavior of nitrosochlorides and nitrosates; formation of 
oximes."^ 

R 
I CI 

c/ 
R /\ 

I / \ R 

C H,C C = N.OH.. I 

/\ ^ I I \ c 

/ \ nitrosochloride /^\ 

H,C CH. / \ 

I I R ^^,^ HC C = N.OH. 

y/ oxime 

H,C C = NOH. 

I 1 

nitrosate 

(5) Behavior of nitroso chlorides: formation of nitrol amines.'* 

R R 

I CI I HN.R 

i/ C/ 

/\ /\ 

/ \ / \ 

H,C C^NOH + H^NR >H,C C = N.OH. 



nitrosochloride nitrolamine 

(6) Addition of N^O^ 

amylenes > bimolecular or bis-nitrosates 

terpenes > " " " 



"Baeyer, Ber. iS, 1586 (1895) ; Ber. 29, 1078 (1896). 

" Best carried out by heating with sodium acetate in acetic acid. Wallach, Ann. 
374, 202 ; S79, 135. 

« Wallacli, 4»n. HI, 296 (1887) ; 262, 327 (1891) ; Ann. BiS, 253 (1888) ; Sjff, 143 
(1906). 



176 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 
(7) Oxidation, parallel behavior, e. g., KMnO^ 



trimethylethylene 
terpenes 

(8) Dilute sulfuric acid, 
CH, 



-^ glycol. 
-» glycols. 



CH, 



>C = CH.CH3 



(9) 



terpenes > 

Concentrated mineral acids, 

amylenes > diamylenes - 

terpenes > diterpenes 



CH3 
-^ >C.CH,CH3 
CH3 I 
OH 

terpene alcohols 



(10) Action of zinc chloride, 
amylenes — 
terpenes — 



-> polymers 



-^ triamylenes, etc. 
-> trimerides, etc. 



->• polymers 



(11) 



Behavior on heating, 

amylenes, rearrangement to more stable form 
chiefly trimethylethylene, 

terpenes, rearrangement to more stable forms, 

6. g., pinenes > dipentene, terpinene 

phellandrenes > " " 

(12) Halides, heated with sodium acetate in acetic acid, 

chloropentanes > amyl acetate + amylenes 

bornyl chloride > bornyl acetate + j Bom^S 

Also, the behavior of the amylenes and the terpenes to bromine, ozone, 
catalytic hydrogenation, air oxidation, and many other reactions, is 
very closely parallel. 

Pentadienes : The preparation and polymerization of isoprene, pi- 
perylene and dimethylallene have been discussed in the chapter on poly- 
merization and the problem of synthetic rubber. Piperylene, 



ACYCLIC UNSATURATED HYDROCARBONS 



177 



CH3 . CH = CH . CH = CHj, may be identified by its physical proper- 
ties (noted in the table on page 231) and by its tetrabromide, 1.2.3.4- 
tetrabromopentane, known in two stereo-isomeric forms (1) crystalline 
form, melting point 114.5° and (2) a liquid, distilling at 115°-118° 
(4 mm.).°^ Oxidation of piperylene by permanganate yields formic 
and acetic acid. Harries '^ endeavored to prove its constitution by 
means of its reaction with ozone but without success ; it combines only 
slowly with ozone but the diozonide was so explosive that no definite 
results were obtained. Auwers^' concludes from the exaltation of its 
refractive index that the double bonds are in the conjugated position. 
The isomer 1 .4-pentadiene, CH2 = CH.CH2CH = CHg, is one of the 
products of the decomposition of pentamethylenediamine nitrite but 
it has only been isolated in the form of its tetrabromide,"^ melting- 
point 86°-87°. The preparation and polymerization of isoprene is also 
discussed in connection with the subject of synthetic rubber. Isoprene 
in glacial acetic acid solution combines with two molecules of hydro- 
gen bromide to form CH^Bt .CUfiBr {CHs) 2, and with hypochlorous 
acid to form a dichlorohydrin melting at 82°- It condenses with ben- 
zoquinone when the two are heated together at 120°-180°, the product 
melting at 234°, and since it yields a dioxime and a tetrabromide Euler 
and Josephson*' conclude that the combination has occurred through 
the double bonds in the isoprene, and the quinone, the product probably 
having the following constitution. 





CH, 



/\ /\ /\ 







-CH, 



According to Ostromuislenski isoprene may be estimated when pres- 
ent in a mixture of butylenes, amylenes, benzene, etc., by shaking with 
about ten volumes of fuming hydrochloric acid for six hours ; the prod- 

»= Maguanlni, Gaxz. CMm. Ital. IB, 391. 

"Ann. iia, 1 (1915). 

"Ber. Ji9, 827 (1916). 

»» Demjanow, Ber. J,0, 2590 (1907). 

"Ber. SS. 822 (1920). 



178 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

uct is washed with cold brine, dried over calcium chloride and distilled. 
The fraction distilling at 50°-90° contains butyl and amyl chlorides, 
the fraction from 90°-130° is separately collected and then, the tem- 
perature rising rapidly from 130° to 142°, the 2.4-chloro-2-methyl- 
butane fraction in a fairly pure condition is collected at this tempera- 
ture. Refractionation of the fraction boiling at 90°-130° will yield a 
further small proportion of the dichloride. 

Ole fines, Six to Nine Carbon Atoms: Very few of the many pos- 
sible hexenes, heptenes, octenes and nonenes have ever been prepared, 
but their properties may be roughly assumed from the behavior of the 
impure mixtures, which have been prepared and from the properties of 
defines of the terpene class, many of which have been carefully investi- 
gated. Certain hydrocarbons of this series are incorrectly described 
in the literature, for example, hexene-(l) boils at 62°-63°, and the hy- 
drocarbon described by Brochet "" boiling at 67° which he separated 
from a distillate from bog head coal, is probably a mixture containing 
chiefly hexene-(2), (see pp. 151-152). High temperatures, and many 
chemical reagents, particularly acids, cause such a-olefines to rearrange 
or the double bond to shift its position. Only reactions employing low 
temperatures and absence of isomerizing reagents can be expected to 
produce these a-olefines in any degree of purity, for example, 

, CH2CH2GH3 

Mg < + BrCH^CH = CH^ -» CHjCH^CH^CH^CH = CH^ 

Br 

+ MgBr^ 

or von Braun's method of decomposing trialkyl ammonium hydrox- 
ide."^ 

The hexene obtained by treating secondary hexyl iodide (from man- 
nite and HI with alcoholic caustic potash is a mixture of hexene- 
(1) and hexene-(2). Tetramethylethylene (CH3)2C = C(CH3)2, is 
the best known of the hexenes and is probably the most stable. Of the 
heptenes only three are known in fairly pure state, and only two of the 
many possible nonenes are definitely known. These hydrocarbons have 
been relatively of such little importance that they will not be described 
in detail. Most of them, as described, are obviously impure and so few 
of the many possible hydrocarbons are known that it is impossible to 
learn anything from a study of their physical properties. 

^"Bull. CMm. & Pli/yg. (3) t, 568 (1892). 
>"4nm. S82, 22 (1911). 



ACYCLIC UNSATURATED HYDROCARBONS 179 

As regards their chemical properties, it should be kept in mind that 
in the majority o'f cases one is dealing with mixtures. Nearly all of 
the defines of this series combine with hydroiodic acid in the cold, 
form nitrosochlorides and nitrosates (which have been definitely de- 
scribed in but a few cases) , and behave normally toward most of the 
reagents affecting olefines. Sulfuric acid yields varying proportions 
of polymers, alcohols and alkyl sulfuric esters. 

None of the known chemical reactions of these olefines offer much 
promise that the unsaturated hydrocarbons in unrefined gasoline will 
be utilized. They can be removed practically unchanged by extraction 
with liquid sulfur dioxide and their conversion to alcohols, ketones and 
acids would not be matters of great difficulty. Such products, if made, 
would be mixtures and, therefore, entirely unsuitable for certain uses, 
for example, perfumes, flavoring materials and pharmaceuticals. 

When one reviews the chemical reactions of such olefines, it is 
evident that these reactions have been devised and applied chiefly for 
the purpose of isolation and identiflcation, or for their removal as a 
nuisance, as for example, the usual method of refining with concen- 
trated sulfuric acid.^"^ It is, therefore, entirely possible that the dis- 
covery of new reactions will render these petroleum olefines industrially 
valuable.^"^ 

Octadienes: Conylene, CsH^^. By distilling the ammonium base 
obtained by exhaustive methylation of coniine, an octadiene is ob- 
tained boiling at 126° (738 mm.). When benzoylconiine is treated 
with phosphorus pentachloride 1 . 5-dichloro6ctane is obtained.^"* 

2.5-Dimethylhexadiene-(1.5) ^"^ is of interest as illustrating a 
property, quite general among dienes of eight or more carbon atoms, of 
forming an oxide, the anhydride of the 2 . 5-diol, when treated with 70 
per cent sulfuric acid. This substance also illustrates the labil char- 
acter of the a-olefine or >C = CH^ group, being converted into dii'so- 
crotyl by the action of alcoholic alkali, 

102 That large proportions of the olefines remain In the refined oil as polymers, has 
previously been pointed out. 

"'The writer suggests that it would hardly be worth while, at least for one who 
greatly values his time, to enlarge our knowledge of the many possible hydrocarbons 
between pentane and the terpenes by proceeding along the old preparative lines, and 
examining the various derivatives by old reactions, and measuring the usual physical 
properties. Pending the possible development of new reactions, or greatly Improved 
old ones, and the discovery of uses for such products as can now be made. It would 
seem that the best utilization of such olefines would be their polymerization, perhaps by 
aluminum chloride or zinc chloride to their much more stable polymers, of value as 
lubricants. 

'"V. Braun & Schmitz Ber. 39, 4366 (1906). 

"" Pogorzelslty, J. Buss. Phye.-Chem 8oo. SO, 977 (1898) ; J. Chem. Soc. Ala. 1899 
I. 785. 



180 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

H,SO 
70% I 0- 



CH3 CH3 ^CH3 I I CH3 

\ / >C.CH,CH,C< 

C.CH^CH^.C CH3 CH3 

// \ 

CH„ CH, CH, CH, 



'■2 



-» 



>C = CH.CH = C< 



KOH CH3 CH3 

The latter hydrocarbon also yields this oxide when treated with 70 
per cent sulfuric acid. (Oxides containing five or six atoms in the ring 
are very much more stable than the three membered ring oxides such 

RCH 

as ethylene or propylene oxides I >0 (Cf. Cineol.) 

CH, 

Nonadienes: Geraniolene, 2.6-Dimethylheptadiene-(1.5). This 
hydrocarbon, boiling-point 142°-143°, is of interest on account of its 
relation to geraniol and citral, and its conversion to cyclogeraniolene 
when treated with 65 per cent sulfuric acid. When the oxime of citral 
is dehydrated by acetic anhydride the nitrile is formed which readily 
yields geranic acid, CgHjg.COaH. On distillation at ordinary pres- 
sure, geranic acid loses a molecule of CO, and forms "geraniolene." ^°° 
The constitution of this hydrocarbon follows from the structure of 
citral and, if we accept the structure of citral as found by Barbier and 
Bouveault^"' the relations between geraniolene and a and P-cycloger- 
aniolene are as follows: 

CH3 

I 
CH3 CH3 CH3 CH, — C 

\ / \ / \ 

C = CH.CH,CH,C > C CH 

/ \ / \ y 

CH3 CH, CH3 CH, — CH, 

CH3 

CH3 CH =C 

and >C< >CH, 

CH3 CH, — CH, 

iMTlemann & Semmler, Ber. 26, 2708 (1893). 
"" Compt. rend. XSS, 393 (1896). 



ACYCLIC UNSATURATED HYDROCARBONS 181 

Tiemanns' conclusions ^"^ as to the constitution of geraniolene and the 
cyclogeraniplenes are confirmed by Crossley and Gilling^°° by the 
synthesis of the supposed intermediate alcohol, and the conversion of 
the corresponding bromide into a and p-cyclogeraniolene. 





and 




Decadienes and Decatrienes : Dihydromyrcene, 2 . 6-Dimethylocta- 
diene (2.6). Boiling-point 166°-168°, D^^" 0.7792."" This hydrocar- 
bon is obtained by the partial hydrogenation of ocimene or myrcene, 
by means of sodium and alcohol/^^ or by slowly distilling methylger- 
anic acid.^^^ Like geraniolene it is converted into a cyclic hydrocarbon 
by sulfuric acid (in acetic acid).^^^ Kishner's method of converting 
aldehydes and ketones to hydrocarbons ^^* converts citral to an isomer 
of dihydromyrcene, boiling-point 164.5°. Kishner's method reduces the 
carbonyl group to — CHj — without affecting the ethylene bonds 
present. 

CH3 

>C = CH.CH„CH,C = CH.CHO 
CH3 ' I 

CH3 

CH3 

> > C = CH . CH^CH.C = CH . CH3 

CH3 \ 

CH3 

^"Ber. SI, 816 (1898) ; SS, 3711 (1900). 

"^ J. Ghem. Soc. 97, 2218 (1910). The above structures are also confirmed by 
the work of Wallach, Ann, SSi, 97 (1902) but are not accepted by Harries and Turk, 
Ann. Si3, 331, 362 (1905). 

"»Bnklaar, Kec. trav. cliim. ge, 164 (1907). 

"I'Semmler, Ber. Si,, 3126 (1910). 

"'TifiEeneau. Compt. rend, m, 1154 (1908). 

^'J. Buss. Phyt.-Chem. Boo. iS, 951 (1911). 

"'Enklaar, Ber. H, 2083 (1908). 



182 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Myrcene, Ocimene and Alloocimene: CioHig. These hydrocarbons 
are isomeric decatrienes, two of the double bonds being in conjugated 
positions. All three hydrocarbons yield 2 . 6-dimethyl octane on hydro- 
genation.^^'^ They are sometimes called "aliphatic terpenes" perhaps 
because of their empirical formulae CioHig and the fact that myrcene 
and ocimene are constituents of essential oils. Myrcene was discovered 
by Power and Kleber ^^^ in oil of bay, Pimenta acris (Myrcia acris) , 
one of the myrtaceae, and thus named by them. It also occurs in oil 
of hops ^" and in oil of verbena, Lippia citriodoro}^^ The physical 
properties of these three hydrocarbons are as follows: 



Myrcene 

Power & Kleber 
Semmler '" 
Enklaar™ 


Boiling-Point 

167° : 67-68° 20mm. 
171-172° : 67-80° 20mm. 
166-168° 


Density 
15° 
0.8023 

0.8613 


n 
D 
1.4673 
1.4673 
1.4700 


Ocimene 

Van Eomburgh "» 
Enklaar'^ 


176-178° : 73-74° 21mm. 
81° 30mm. 


Density 
15° 
0.801 
0.8031 


n 
D 
1.4861 
1.4857 


Allo-Odmene 

Auwers & Eisenlohr "^ 




0.8119 ^f 


1.5455f 


Enklaar"" 


188° : 81° 12mm. 


0.8133 


1.5447 



Myrcene and ocimene, on partial hydrogenation, yield the same di- 
hydromyrcene (dihydromyrcene tetrabromide melting-point 88°), and 
of the two original hydrocarbons myrcene is much more rapidly resini- 
fied. Enklaar proposed the following structures for myrcene, ocimene 
and dihydromyrcene. 
CH, 



CH, 



>C= 



:CH . CH2CH2C — CH^CHj 

I 
CH, 



myrcene 



CH, 



>C=CH . CH2CH2C=CH . CH3 

I 
CH, 



reaction-product 



CH3 
CH3 t 

> C=CH . CH2CH=C— CH=CH3 
CH3 I 

CH3 
ocimene 

""Enklaar, Ber. il, 2083 (1908). 

'"Pharm. Rev. (New York), IS. 61 (1895). 

"' Semmler & Mayer, Ber. U„ 2009 (1911). 

u'Barbier, Bull. 8oc. CMm. (3), 2.5, 691 (1901). 

^Ber. Si, 3126 (1901). 

"° Rec. trav. cMm. 26, 157 (1907) ; Schimmel & Co. 8emi-Ann. Rep. 1906, I, 109. 

121 Chem. Zentr. 1901, I, 1006. 

i"ieee. trav. CMm. 26, 157 (1907) ; Schimmel & Co. SemUAnn. Rep. 1906, I, 109. 

^J. prakt. Chem. (2) 81,, 37 (1911). 



ACYCLIC UNSATURATED HYDROCARBONS 183 

Ocimene derives its name from its presence in the essential oil of 
Ocimum basilicum. 

Allo-ocimene was thought to be a geometrical isomer of ocimene, 
being obtained from this hydrocarbon by heating. Enklaar^^* later 
studied the ozonides and the resulting decomposition products of these 
hydrocarbons and concludes that allo-ocimene is 

CH3 

>C = CH.CH = CH.C = CH.CH3 
CH3 1 

CH3 

This structure having all three ethylene bonds in conjugated positions, 
as in n . hexatriene, accounts for the high refractivity of this hydro- 
carbon. 

Both ocimene and myrcene yield alcohols, ocimenol and myrtenol, 
on treating with acetic acid and a trace of sulfuric acid, according to 
Bertram and Walbaum. Barbier ^''^ believes myrcenol to be different 
from linalool, and Enklaar noted the following constants: Boiling- 
point 99° (10 mm.), d^^" 0.9032, nL=i 1.4806, phenylurethane melting- 
point 68°. Ocimenol gives a phenylurethane melting at 72°. Enklaar is 
of the opinion that myrcene, ocimene and allo-ocimene are not obtain- 
able in a state of purity, an opinion held by Wallach with regard to 
the terpinenes and phellandrenes. The instability of the former hy- 
drocarbons probably accounts for the fact that the physical constants 
of the myrcene investigated by Lebedew and Mereshkowski ^^° was 
found, after "repeated purification," to be quite different from the con- 
stants observed by others.^^' 

Other Derivatives of 2 . 6-Dimetliyloctane. 

The Citral Group: Several well-known alcohols and aldehydes be- 
long to this group. Their occurrence in essential oils is very wide and 
includes a very large number of plant species. Many of the most valu- 
able essential oils owe their fine aroma chiefly to substances of this 
group, for example, the essential oils of the rose, Rosa damascena and 
Rosa centifolia, lavender and orange blossoms. Some of the cheaper 
oils such as lemon grass, citronella and palmrosa oils are used as raw 

^'*Beo. trav. chim. se, 215 (1916). 

'"Bull. Soc. cMm. (3) 25, 687 (1901). 

'"J. Rusa. Phys.-Chem. Soc. /,S, 1249 (1913). 

"' The polymeriziDg action of metallic sodium on conjugated dlenes Is now well 
known ; such hydrocarbons give a brown resinous deposit after repeated distillation 
over sodium. 



184 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

materials for the isolation of certain constituents such as citral and 
geraniol, which are further utilized, as in the manufacture of ionone 
from citral. The chemical behavior of these alcohols and aldehydes 
has been well established but in most cases it has been impossible defi- 
nitely to distinguish between the groups 

CH3 CH3 

\ \ 

C = CHR and C.CH^R. 

/ / 

CH3 CH, 

Instead of outlining the historical development of the subject, the gen- 
eral relationships of the substances in this group will be indicated, fol- 
lowed by a description of the individual substances and some of their 
more important reactions. 

The chemical behavior and constitution of substances in the citral 
series is intimately associated with methylheptenone,^^' or, as Tiemann 
and Semmler^^' showed it to be, 2-methylheptene-(2)-one-(6), (CHg)^ 
= CH . CH^CH.COCHa. A little later, Verley "" confirmed this struc- 
ture by synthesis. Oxidation, first by Wagner's method, using cold 
dilute permanganate, followed by chromic acid, yields acetone, and 
levulinic acid. 

CH3 : 

• > C = CH . CH,CH2C0CH3 > ( CH3 ) „C0 4- CH^COCHs 

CH3 : 'I 

: CH,CO,H 

On boiling an aqueous solution of potassium carbonate with citral 
methylheptenone and acetaldehyde are formed, and on oxidizing with 
chromic acid methylheptenone is also produced. The empirical for- 
mula of citral is CjoHk-O and its chemical behavior and physical prop- 
erties indicate that it is an aldehyde containing two double bonds. If 
methylheptenone condensed with acetaldehyde, splitting off a molecule 
of water as in the condensation of acetaldehyde to croton aldehyde, or 
acetone to mesityl oxide, 

CH3 CHO + CH3CHO > CH3CH = CH.CHO 

1" Methylheptenone Is usually associated with citral, and Is a constituent of 
lemon grass, lemon, palmarosa and llnaloe oils. It is best prepared by boiling a 10% 
solution of potassium carbonate with citral, Verley, Bull. Soc. chim. (3) n, 176 
(1897). Its boiling-point is 173°-174° ; density 20° 0.8602. Hydrogen in the presence 
of nickel at 180°-190° saturates only the double bond ; sodium and alcohol reduces the 
ketone group forming methyl heptenol. It reacts normally with alkyl magnesium 
halides. 

«»Ber. S8, 2115, 2126 (1895). 

"'Bull. Soc. cMm. n, 192 (1897). 



ACYCLIC UNSATURATED HYDROCARBONS 185 

CH3 CHj 

>CO + H2CH.COCH3 > >C = CH.C0CH3 

the result would be citral. Such a reaction would be the reverse of 
the hydrolytic reaction brought about by aqueous potassium carbonate. 

CH3 CH3 

>C = CH . CH,CH,C = CH . CHO ^ >C = CH . CH,CH,C = 
CH3 I CH3 I 

CH3 CH3 

citral + CH3CHO 

That this is the structure of citral is indicated by the synthesis of 
geranic acid from methylheptenone ^'^ and the conversion of geranic 
acid to citral by heating its calcium salt with calcium formate.^'^ 
Methylheptenone and iodoacetic ester condense in the presence of zinc 
to give the hydroxy acid and heating this with acetic anhydride yields 
geranic acid. 

CH3 

>C = CH.CH2CH2C = + CHJ.CO^R > 

CH3 I 

CH3 

CH3 OZnl 
> >C = CH.CH3CH2C< ^ hydroxy acid 



CH3 I CH2CO2H 

CH3 

CH3 

> >C = CH.CH2CH2C = CH.C02H > 

CH3 I 

CH3 

CH3 

>C = CH-CH^CH^C = CH.CHO 
CH3 I 

CH3 

citral 

Tiemann ^°^ discovered that purified natural citral yields mainly 
a semicarbazone melting at 164°, and from the mother liquors of these 
crystals a second semicarbazone melting at 171° was isolated; mixtures 
of the two melt as low as 130°. The aldehyde yielding the low melting 

'"Barbler & Bouveault, Oompt rend. i28, 393 (1896). 

"2 Tiemann, Ber. SI, 827 (1898). 

'"Ber. SI, 3331 (1898) ; S2, 115 (1899) ; SS, 877 (1900). 



186 CHEMISTRY OP THE NON-BENZENOID HYDROCARBONS 

semicarbazone was designated "citral a" and the other "citral h." Cit- 
ral a condenses more readily with cyanacetic acid, forming a citry- 
lidene cyanacetic acid melting at 122° and the corresponding deriva- 
tive of citral b melts at 94°-95°. Tiemann considered these isomeric 
crystalline derivatives as geometrical isomers and Zeitschel ^^* states 
that citral a and citral b probably correspond to the geometrically 
isomeric alcohols geraniol and nerol. 

Me,C = CH . CH^CH.C — CH, Me^C = CH . CH,CH,C — CH3 

II ^ II 

HC — CH^OH. HC.CHO 

geraniol citral a 

Me^C = CH . CH^CH^C — CH3 Me^C = CH . CH^CH^C — CH3 

II ^ II 

HO.HjC — C — H. OHC — C — H 

nerol citral b 

Citral a and citral b have practically the same chemical proper- 
ties ^^° and their physical properties differ only very slightly. As a 
rule, the boiling-points of such geometrical isomers differ only very^ 
slightly, for example, the two p-butylenes, and dibromobutylenes 

HC — CH3 boiling-point HC — CH3 boiling-point 

HC — CH3 + 1° to 1.5° CH3 — C — H + 2° to 2.7° 

Br — C^CHj boiling-point Br — C — CH3 boiling-point 

II II 

Br — C — CH3 146°-146.5° CH3 — C — Br 149°-150° 

That small differences in structure may greatly affect the melting 
point has previously been pointed out, and the different melting points 
of certain derivatives of these isomeric citrals is a case in point. Con- 
version of citral a to citral b and vice versa takes place readily, and, 
according to Bouveault,^'^ alkalies convert a to b. Ordinary natural 
citral gives nearly pure condensation products of citral a. 

Further confirmation of the above relationship of geraniol and nerol 
is found in the behavior of these two alcohols on oxidation, first by 
dilute permanganate thus oxidizing the double bonds to glycols, and 
followed by oxidation with chromic acid. Both alcohols yield the same 
oxidation products and in the same proportions, i. e., acetone, levulinic 

"«Ber. S9, 1780 (1906). 
"'Tiemann, Ber. S3, 877 (1900). 
"•Bull. Soo. chim. (3), SI, 423. 



ACYCLIC UNSATURATED HYDROCARBONS 



187 



acid and oxalic acid.^'' As in the case of the two citrals, geraniol and 
nerol have nearly identical physical properties but the melting-points 
of some of their condensation products differ markedly. 



Boiling-point 



Specific gravity 

Refractive index 

Diphenylurethane, M. P.. 
Tetrabromide, M. P 



Geraniol "" 


Nerol'" 


230° 


226°-227° 


110°-lll°(10mm.) 


lll°(9inm.) 


0.8812 to 0.883"° 


0.8813"° 


1.4766 - 1.4786 


1.468 


82.5° 


52°-53° 


70°-71° 


118°-119° 



Separation of geraniol and nerol is best carried out by means of anhy- 
drous calcium chloride which forms a crystalline product with geraniol 
but not with nerol. 

According to a recent paper by Verley,^^" citral a is mainly the A^ 
isomer. When it is boiled with one per cent aqueous caustic soda 
2-methyl-A^-heptenone is produced, which when oxidized first by per- 
manganate and then by chromic acid gives only traces of acetone, 

OH 
CH^ CH^OH. 

\ \ 



CH, 



/ 



C -CH^CH.CH.CO . CH3-* 



CH, 



/ 



C-CH.CH^CHaCOCH, 



This methylheptenone is rapidly converted into the isomeric, ordinary 
2-methyl-A^-heptenone, by warming with dilute sulfuric acid. Verley 
therefore favors the corresponding A^ formula for geraniol and points 
out that this structure better explains the conversion of geraniol to 
dipentene. > 



?H, 



CH, 



H,C 



H^C. 



'^, 



CH 



CH,OH 




-^ 



XH, 




H. 



CH3 ^CH, 



CH3 -CH^ 



■"Blumann & Zeitschel, Ber. U, 2590 (1911). 

"= Bertram & Gildemelster, J. prakt. Ohem. (2) 5S, 508 (1897); Erdmann, J. 
prakt. ahem. (2) 56, 3 (1897) ; Stephan, ibid., 58, 110 (1898). 
"•Soden & Tre£f, Chem. Ztg. 27, 897 (1903). 
'"Bull. 8oe. chim. (4), 2S, 68 (1919). 



188 CHEMISTRY OF THE NON-BENZENOlD HYDROCARBONS 

Two ketones occurring in artemisia oil appear to have a carbon 
structure different from the citral group but these two isomeric ketones 
are supposed to bear the same relation to each other as the A^ and A^ 
isomers discussed above.^^^ 

As is indicated in the foregoing discussion of the constitution of 
citral, the constitution of geraniol and nerol are shown by their rela- 
tions to citral. Citral is formed from geraniol by oxidation with chro- 
mic acid,^*^ and reduction of citral yields geraniol. Apparently only 
the groups — CHjOH and — CHO are affected. On more energetic 
oxidation the citral first formed is oxidized as indicated above, to 
methylheptenone, acetone, levulinic acid, etc. These relations are, 
therefore, expressed by the following constitutions of geraniol, 

CH3 

\ 

C = CH.CH^CH^C = CH.CH.OH 

/ 1 

CHj CH3 

CH3 

\ 

or, C . CH^CH^CH^C = CH . CH.OH 

/ I 

CH2 CH3 

When geraniol is heated with water in an autoclave to 200° linalool 
is formed,^*^ and the conversion of linalool to geraniol, or geranyl ace- 
tate is brought about by heating with acetic anhydride.^** By warm- 
ing a solution of linalool in toluene with hydrochloric acid, geranyl 
chloride is formed.^*^ These changes are readily understood from the 
structure of linalool deduced by Tiemann and Semmler^*" by a study 
of the oxidation products of linalool. Oxidizing first with dilute per- 
manganate, followed by chromic acid gave acetone and levulinic acid 
(equivalent to methylheptenone) and oxalic acid. 

CH3 : OH . CH3 

>C = CH.CH,CH,C<. • > >C0 + 

CH3 : 'I .CH = CH, CH3 

CH3 . 

1" Asahina & Takagl, J. Chem. Soc. Ala. 1931, I. 9. 
i« Semmler, Ber. gS, 2966 (1890). 
'" Bchimmel & Co.'s Ber. 1S98, I, 25. 

>" Bouchardat, Compt. rend. 116, 1253 (1893). Terplneol is also formed. 
"'Tiemann, Ber. SI, 832 (1898) ; Dupont & Labaune, Roure-Bertrand, FiU. Bull. 
1909, II. 27; Forster & Cardwell, J. Chem. Soc. lOS, 1338 (1913). 
"«Ber. 28, 2126 (1895). 



ACYCLIC UNSATURATED HYDROCARBONS 189 



C02H.CH2CH,C0 CO,H 

+ I 

m, co,H 



2^^ 

k 



It was also pointed out that the chemical and physical properties of 
linalool agree with the structure of a tertiary alcohol, and that when 
oxidized by chromic acid direct, to citral, isomerization by the acid to 
geraniol, or the glycol, first takes place, 

by acid CrOg 
linool > geraniol > citral 

OH OH 

CH3 T I 

>C = CH . CH3CH2C — CH = CH^ > RC — CU, — CH^OH 

CH, j I 

linalool 



3 

H, CH, 



>R — C = CH.CH.OH > RC = CH.CHO 

CHj geraniol CH3 citral 

Linalool has recently been synthesized by Ruzicka ^" who employed 
a reaction discovered by Nef,^*' i. e., condensation of acetylene with 
ketones by means of metallic sodium. The first condensation product 
gives good yields of linalool on reducing by moist ether at low tem- 
peratures. 4 
CH3 

>C = CHCH^CH.C = CO + HC = CH 
CH3 I 

CH3 

CH3 OH 
> > C = CH . CH,CH,C < 



CH3 I C = CH > linalool 

CH3 

The constitution of citronellol and the corresponding aldehyde, cit- 
ronellal, is shown by the following reactions ; citral may be oxidized to 
the corresponding acid geranic acid and on reducing this by sodium and 
amyl alcohol citronellic acid is obtained; also the aldehyde citronellal 
may be converted to its oxime and this, by loss of HjO, to the nitril, 
which yields citronellic acid. Therefore, citronellol is dihydrogeraniol, 

"'Hell!. CMm. Acta. 8. 182 (1919). 
"8 Aran. 308, 264 (1898). 



190 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

and citronellal is dihydrocitral.^^' As to the location of the remaining 
double bond in citronellic acid, citronellol and its aldehyde, the evi- 
dence was at first confusing, but the facts are best explained by the 
reduction of the RC = CH . COOH group, which is in harmony with 



ii 



the well known highly reactive character of the >C = C — CO — 
group. The aldehyde citronelall can be reduced mainly to the corre- 
sponding alcohol, citronellol, by sodium amalgam in acetic acid.^'^" As 
with the other substances of this group, some doubt remains as to 
whether the double bond in citronellol and its aldehyde is in the po- 
sition shown but according to Harries ^^^ both isomers are present in 
natural citronellol, i. e., 

CH3 

\ 

C = CH.CH.CH.CH.CH^CH.OH 

/ I 

CH3 CII3 

and 

CH3 

\ 

C — CH2CH2CH2CI1 . CHjCHjOH. 

// I 

CH2 CH3 

Citronellol and rhodinol appear to be isomers differing only in the 

CH2 

\ 

position of the double bond, C.CH^R, or (CH3)2C = CH.R. 

CH3 

The question of the existence of rhodinol has been the subject of con- 
siderable controversy, the difficulty of deciding such questions being 
that, as in all such cases, the chemical behavior and physical prop- 
erties are so nearly identical, and conversion of the one isomer into the 
other takes place with great ease. In discussing the simple aliphatic 
olefines, such as hexene(l), it was pointed out that double bonds of 
the type RCH2CH = CH^ frequently shift their position very readily, 
and the work of Verley, noted above, shows that warming with dilute 
sulfuric acid changes the group 

"•Tiemann, Ber. SI, 2899 (1898) ; Bouveault, Oompt rend. 138, 1699 (1904). 
i" Dodge, Am. Chem. J. 11, 463 (1889). 
"ifier. tl, 287 (1908). 



ACYCLIC UNSATURATED HYDROCARBONS 191 

CH, 

\ 

C.CH.R to the isomer {CH3)2C = CH.R. 

/ 

German chemists continued to regard rhodinol as a mixture of cit- 
ronellol and geraniol but Harries ^^^ and his assistants have shown that 
natural citronellol and the aldehyde citronellal consists of a mixture 
of the two isomers, confirming the contention of Barbier, Bouveault ^^^ 
and Locquin ^^* as to the existence of rhodinol. According to Harries 
ordinary citronellal, derived from oil of citronella, contains approxi- 
mately 60 per cent "rhodinal," the aldehyde corresponding to rhodinol. 
Methods of oxidation have not clearly shown the structure of these 
isomers but rhodinol appears to be the more stable of the two alcohols. 
Both alcohols, in the form of their acetates, combine with hydrogen 
bromide, and when this is removed by heating with sodium acetate, 
rhodinol is the product. Also, according to Barbier and Locquin,^''' 
citronellal may be converted into its oxime, which on dehydrating by 
acetic anhydride yields the nitrile, but the oxime of the aldehyde, made 
by the oxidation of Z-rhodinol or d-rhodinol, does not yield the nitrile 
but acetylmenthone oxime. Citronellol may be converted into rhodinol 
by the addition of water, brought about by treating with 30 per cent 
sulfuric acid. 

CH, 

C . CH^CH.CH . CH3 . CH^OH 
/ I citronellol 

CH3 I CH3 

CH3 '•' 

C . CH.CH.CH^CH . CH,CH,OH 

CH3 OH I CH3 

CH3 ^ 

C = CH . CH2CH2CH . CH, . CH3OH 

/ I rhodinol (according to 

CH3 CH3 Barbier) . 

'"Ber. kU 2187 (1908) ; Ann. ilO, 1 (1915). 
^"Bnll. Soc. oMm. (3), M, 458, 465 (1900). 
"^Compt. rend. 157, 1114 (1913). 
^"Loo. olt. 



192 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Prins ^^° endeavored to separate natural citronellal into its two isomers, 
by repeated fractional distillation^^' followed by repeated fractional 
crystallization of the semicarbazone and semioxamazone, but without 
success. Prins also studied the conversion of citronellal to isopulegol, 
by treating with 85 per cent formic acid and by 80 per cent phosphoric 
acid but was unable to detect the formation of any substance, which 
could be derived directly from rhodinal. The formation of isopulegol 
acetate by heating ordinary citronellal with acetic anhydride is prac- 
tically quantitative,^^^ which, in the light of Harries' work, indicates 
that under these conditions rhodinal must be converted into its isomer, 
true citronellal. Barbier and Bouveault believed that they had ob- 
tained small yields of menthone from rhodinal, but Tiemann and 
Schmidt ^^' were unable to confirm this. The ready conversion of cit- 
ronellal to isopulegol, however, favors the structure purposed by Bar- 
bier for this aldehyde, 



CHj 




CH, 




CH 






^CH^°" 



CH, 



CH, 



'^ 



CH, 



According to Semmler^^" aldehydes of the types R2CH.CHO and 
RCH2CHO are converted to enolic forms by acetic anhydride and that 
in the case of citronellal this change precedes ring formation. 

The above review illustrates how difficult it is to distinguish be- 
tween isomers of this kind. 

Geraniol. The importance of the alcohols and aldehydes of this 
group to the essential oil industry warrants further description of them 
and their chemical behavior. Geraniol is present to a large extent in 
palmarosa oil, ginger grass, citronella and oil of sweet geranium, partly 

'^ CJiem. WeekM. It,, 62T, 692 (1917). The maximum difference in boiling-points 
observed by Prins was 198°-200° for the low-boiling fraction and 203°-204° for the 
higher boiling portion. 

"' Schimmel & Co.'s Kep. 1910, I, 155. 

^^ Schimmel <£• Co.'s Rep. 1S96, 34; Scmmler, Ber. i2, 584, 963, 1161, 2014 (1909). 

"'Ber. SO, 38 (1897). 

'"Ber. i2, 584, 963, 1161, 2014 (1909) ; U, 991 (1911). 



ACYCLIC UNSATURATED HYDROCARBONS 193 

in the free state and partly as the acetate. In oil of geraniuna small 
proportions of the geraniol ester of tiglic acid are present.^^^ Com- 
mercially geraniol is isolated from either palmarosa or citronella oil by 
means of finely ground anhydrous calcium chloride, 'the mixture being 
chilled to about — 5° for several hours. Other oils are removed by 
means of petroleum ether and the crystalline calcium chloride com- 
pound decomposed by water. Small percentages of geraniol cannot be 
separated from essential oils in this manner. It is readily identified 
by its diphenylurethane/^^ melting-point 82°, or its naphthylurethane, 
melting-point 47°-48°. 

Geranyl chloride is of particular interest as filling a niche in the 
chemistry of the non-benzenoid hydrocarbons and contributing lo the 
generally similar chemical behavior of this whole class of substances. 
Although not mentioned in Richter's "Lexikon" geranyl chloride was 
evidently first made by Jacobsen ^^' and later by Tiemann ^°* who pre- 
pared large quantities of it by the action of hydrogen chloride on 
geraniol. Dupont and Labaune ^^^ passed dry hydrogen chloride into 
a solution of geraniol or linalool in toluene at 100° and noted that 
both alcohols gave the same chloride, which they called linalyl chloride, 
and Kerschbaum ^'"' following Tiemann's first method, made it by 
treating geraniol with phosphorus trichloride. The first study of the 
chloride and its reactions was carried out by Forster and Cardwell,^" 
who employed Darzen's method, dissolving the geraniol in pyridine 
and treating with thionyl chloride. The chloride was shown to be a 
derivative of geraniol rather than linalool by the preparation of geranyl 
acetone, by the action of geranyl chloride on the sodium derivative of 
acetoacetic ester, and hydrolysis of the geranyl acetoacetate by barium 
hydroxide. The constitution of geranyl acetone is shown by reference 
to the constitution of famesol ^"^ and the work of Kerschbaum.^°° The 
chlorine atom in geranyl chloride is stabilized by the proximity of a 
double bond, (CH, ) C = CH . CH.CH^C = CH . CH^Cl but it reacts 



i. 



normally with sodium ethoxide to give the ethyl ether and with sodium 
acetoacetic ester and sodium malonic ester. From the latter substance 

'" Schlmmel & Co., Semi-Ann. Rep. 1913, II, 61. 

»"=Cf. Parry, "Essential Oils" Vol. II, Ed. II, 1919, 98. 

""A»». 157, 236 (1871). 

"»Ber. 189, 921 (1896) ; SI, 832 (1898). 

""■ Boure-Bertrand Fas' Bull. 1909, II, 19. 

"«Ber. 4e, 1735 (1913). 

"'J. Chem. Soe. 103, 1338 (1913). 

iM Harries & Haarman, Ber. ■}«, 1737 (1913). 

^"Loc. cit. 



194 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

geranyl acetic acid was made, CioH„ . CHjCOjH. Sodium azide yields 
the azoimide and corresponding amine, geranyl amine. 

Prileshajev"" has prepared the mono and dioxides of geraniol by 
direct oxidation by benzoyl peroxide. The dioxide is a mobile liquid 
boiling at 180°-183° under 25 mm. 



CH3 /\ /\ 

> C — CH . CH^CH.C — CH . CH^OH 
CH3 I 

CH3 

geraniol dioxide (according to Prileshajev) 



Geraniol is markedly less stable than citronellol. On heating with 
phthalic anhydride to 200° geraniol is decomposed but citronellol forms 
the acid phthalic ester; concentrated formic acid also decomposes ge- 
raniol much more readily than citronellol.^'^ Benzoyl chloride at 140°- 
160° also decomposes geraniol,^'^ but not citronellol. 

Isogeraniol: Evidence of a shift in the position of one double 
bond in citral by the action of acetic anhydride is furnished by the 
isolation of an isomer of geraniol when the acetic ester of enol-citral 
is reduced by sodium amalgam in methyl alcohol acidified by acetic 
acid.^'^ This alcohol, like geraniol, has a fine roselike odor and may 
be distinguished by means of its diphenylurethane melting at 73°. Ac- 
cording to Semmler, the formation of isogeraniol may be represented 
as follows: 



CH, 



H^ 




CH, 



CH, 




CHO 



CH3 






CH, 



CH, 



XH, 



"^ 



CH(0Ac) 




XH, 



H, 



CH^OH 



CH, 



CH3 



'^ 



CH, 



""J. Russ. Phys.-Cliem. Soc. 44, 613 (1912) ; a trace of mineral add bydrolyEes 
one of the oxide groups, forming tne glycol, Cn)Hi70.(0H)3.2H20 melting-point 94.5°, 
also the anhydrous glycol CioHuO.CGHJs In two forms melting at 145° and 163°. 

"iWalbanm & Stephen, Ber. SS, 2307 (1900). 

'"Barbier & Bouveault, Compt. rend. ISi, 530 (1896). 

"'Semmler, flpr. m, 991 (1911). 



ACYCLIC UNSATURATED HYDROCARBONS 



195 



Linalool: Linalool is isolated technically from oil of Central 
American linaloe wood. Its acetate is the principal constituent 
of oil of lavender and it is an important component of a great 
number of other essential oils, among which are ylang-ylang, cham- 
paca, rose, geranium, petit-grain, bergamot, neroli, jasmine and other 
oils. It is not easily isolated or purified since it yields no crystal- 
line addition products or derivatives from which linalool can easily be 
regenerated. Hydrogen chloride forms geranyl chloride, boiling-point 
82°-86° at 6 mm."* Mono linalyl phthalate may be prepared by 
forming the sodium compound of linalool, in ether and allowing this to 
stand several days with phthalic anhydride.^'^ Linalool, being a ter- 
tiary alcohol, is partially decomposed when acetylation by acetic an- 
hydride is attempted, dipentene, terpinene, a-terpinyl acetate and neryl 
acetate being formed.^^^ Continued heating with acetic anhydride de- 
composes terpineol, also a tertiary alcohol, and maximum yields of ter- 
pinyl acetate, about 85 per cent, are obtained in 45 minutes.^^' When 
diluted with xylene, as proposed by Baulez, the maximum esterifica- 
tion, about 63 per cent, is obtained in 7 hours.^" The conversion of 
linalool to terpinene and dipentene by heating with acids is believed to 
involve isomerization to geraniol. 



CH, 




CH, 



CH, 



OH 
H 




-> 



CH, 



H 



CH^OH 




OH 



CH 



'V, 



CH, 



ch; 



c^ 




CH, 



ch: 



OH 
CH, 



Anhydrous oxalic acid is much more energetic in its action and yields 
a bicyclic diterpene, CjoHja, isocamphorene.^^^ 

Oxidation of linalool by benzoyl yields a mono oxide or dioxide 
depending upon the proportions of benzoyl peroxide employed ^^° and 

'" Forster & Cardwell, loc. oit. 

""Charabot, Ann. chim. phys. (7), 21, 232 (1901). 

"•Stephan, J. prakt. Chem. (2), 58. 109 (1898) ; Zeitschel, Ber. 39, 1780 (1906). 

"' Schimmel & Co.'s Ber. 189S. I, 38. 

"• Schimmel & Co.'s Ber. 1907, I, 127. 

"•Semmler, Ber. 1,1, 2068 (1914). 

ISO prileshajev, loc. cit. The oxide of linalool found in lanaloe oil by Schimmel 
& Co. ISenU'Ann. Rep. 13m (2), 78] boils at 197°-198° (758mm.) and is not readily 
hydrolyzed by dilute acids indicating clearly that the oxygen is not attached to 



196 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

H. Erdmann ^^^ employed linalyl acetate in studying the addition of 
sulfur to unsaturated substances to form what he terms thioozonides. 
These thioozonides decompose on heating, evolving hydrogen sulfide. 

A tertiary alcohol resembling linalool and containing two more 
hydrogen atoms (one less double bond) has been prepared by two well- 
known reactions, which have previously been discussed in connection 
with the synthesis of hydrocarbons, and the action of sulfuric acid 
upon defines. Thus dihydromyrcene on treating with 85 per cent 
sulfuric acid^'^ yields dihydrolinalool; the same tertiary alcohol is 
obtained by the action of ethyl magnesium bromide on methyl hep- 
tenone. 

+ H3 

(1) myrcene * CH3 + H^O 

> C = CH . CH2CH,C = CH . CH3 ^ 

CH3 "I 

CH3 

(2) CH3 

> C = CH . CH3CH3C = + C,H,MgBr > 

CH3 I 

CH3 

CH3 CXI2CI13 

> > C = CH . CH,CH,C < 

CH3 I OH 

CH3 

dihydrolinalool. 

Contrary to opinions previously held, Dupont and Labaune ^'^ find 
that the double bonds in linalool and geraniol react with sodium sul- 
fite. These alcohols are completely dissolved by continued shaking 
with aqueous sodium sulfite, the compounds CioH^sO . 2NaHS03 hav- 
ing been isolated. It has long been known that the ethylene bond in 
citral, in the group — G = CH.CHO reacts readily with sodium sul- 



k 



fite, but this is the first instance of unsaturated alcohols reacting in 
this manner. 

Citronellol and Rhodinol: From the foregoing discussion of these 

adjacent carbon atoms. The oxide of linalyl acetate, made by Prileshajev's method, 
reacts with water readily to give the glycol CioBuiOFDz-OzCiB-a which on saponifica- 
tion .yields CkiHi,(OH)3 melting at 54°-55°., 

'«4«n. S62, 137 (1908) 

i»2 Myrcene is converted to cyclo dihydromyrcene by the action of sulfuric acid 
in acetic acid. 

"" Boure-Bertrand Fits' Bull. 1SJ2, (3) 6 d 7; J. Chem. Soe. ISIS, I, 746. 



ACYCLIC UNSATURATED HYDROCAnBONS 



197 



two substances it is evident that these two alcohols occur together, 
and while recognizing the probable existence of rhodinol, the name 
citronellol will be retained and, following common usage, will be em- 
ployed for the alcohol CjoHjoO, containing one double bond, and hav- 
ing the following physical properties: 

Phtsical Pbopeeties. 



Observer 


BoUing-Point 


Density 


^D 


Method of 
Isolation 


Wallach"* 


114°-115°(12-13mm.) 


0.856^^° 


1.4561 


Destroying 
geraniol at 250° 


Tiemann '" 


117°-118° 


(17mm.) 


0.856511° 


1.4566 


reduction of 
citronellal 


Tiemann '"" 


\\Z°-\W 


(15mm.) 


0.8612 ^°° 


1.4578 


by PClj method 


Schimmel & 
Co."' 


225°-226'' 




0.862 


1.45611 


Wallach's 
method 


Schimmel & 
Co."» 


109° 


(7mm.) 


( 0.8604 
( 0.8629 


1.4565 ) 
1.4579 ■ 


From Java 
citronella 


Schimmel & 
Co. 


225°-226° 




0.862 
0.869 


1.459 
1.463 ■ 


Commercial 
preparation from 
oil of geranium 



Citronellol is considerably more stable than geraniol or linalool, 
to the action of alkalies, 10 per cent sulfuric acid, heating with formic 
acid or phthalic anhydride, phosphorus trichloride in the cold, heating 
with water as in Wallach's method of purifying citronellol. The for- 
mation of a cyclic hydrocarbon by loss of water from citronellol has 
not been observed. 

Citral: The constitution of citral and the nature of citral a and 
citral b have been discussed in the preceding general discussion. The 
following physical properties of citral have been noted: 



Observer 



Boiling-Point 



Tiemann & Semmler"" 110°-112°(12mm.) 
117°-119°(20mm.) 



Schimmel & Co." 



Schimmel & Co. 



110°-lll°(12mm.) 



92°- 93° (5mm.) 



■"JTacftr. K. Oes. Wiss. Oottingen, 1896, 56. 

"'Ber. S9, 906 (1896). 

""'Ibid, 923. 

'" Schimmel & Co.'s Ber. 1898, 62. 

'" Ibid, 1902, I, 14. 

'"Ber. B6, 2709 (1893). 

'"BcMmmel d Oo. Rep. 1899, I, 72. 



Density 



0.8972 



15° 



0.893 



15° 



0.8926ii 



"D 



nj. 
1.4931 
1.4901 

1.4885 



Source 



lemon- 
grass 

lemon 



198 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

In addition to the chemical reactions of citral noted above, the fol- 
lowing may be noted. Potassium acid sulfate or moderately diluted 
sulfuric acid react on citral very energetically with ring closing, loss 
of water and the formation of p . cymene. 

The behavior of citral to sodium sulfite solutions has been the sub- 
ject of considerable investigation. In the presence of a very slight ex- 
cess of free sulfiu-ous acid, in the cold, the normal, aldehyde addition 

OH 
product CgHi5CH< is formed, separating as very fine, spar- 

OSO,Na 

ingly soluble, crystalline plates; regeneration of citral from this de- 
rivative is not quantitative. If this crystalline product is allowed to 
stand, and gently warmed, with an excess of bisulfite, it goes into 
solution as a labil dihydrodisulfonic acid derivative, from which citral 
can be regenerated by the action of caustic soda, but not by alkali 
carbonates. If the bisulfite solution of citral is strongly heated, the 
stabil dihydrodisulfonic acid derivative is formed and it is impossible 
to regenerate citral from this stabil combination. If the labil dihydro- 
disulfonic acid salt is treated with another molecular portion of citral, 
this goes into solution as a labil monohydrosulfonate which can readily 
be decomposed to citral. The formation of labil soluble sulfonate of 
citral can also be carried out by employing neutral sodium sulfite and 
neutralizing the free alkali, as fast as formed, by acetic acid.^'^ 

C,Hi,CHO + 2Na2S03 + 211^0 -^ C^HisCHO. (NaHSOa)^ + 2NaOH 

This reaction usually gives so much difficulty that Tiemann's ^^^ direc- 
tions may be given here. A solution of 350 g. sodium sulfite in one liter 
of water is made slightly alkaline to phenolphthalein, treated with 100 
g. citral and gently shaken, keeping just slightly alkaline by the con- 
tinual addition of a calculated quantity of 20 per cent sulfuric acid (or 
acetic acid) . The solution should always be distinctly red by phenol- 
phthalein, since in slightly acid solution the sparingly soluble crystal- 
line compound will separate. The various addition products formed 
by sodium bisulfite and citral may be summarized thus,^"' where X 
represents the SOgNa group. Evidently, in the stable derivatives, car- 
bon and sulfur are directly combined as — C — SOgNa or true sulfonic 
acid salts. 

'"Cf. Gildemelster, "Die Aetherischen Oele," Vol. I. Ed. II. 429— (1910). 

'"Ber. SI, 3317 (1898). 

"»G. Komeo, Oaen. cMm. Ital. ^, (1), iS (1918). 



ACYCLIC UNSATURATED HYDROCARBONS 199 

(1) normal aldehyde addition product. 

CH3 OH 

> C = CH . CH^CH^C = CH . CH < labil. 

CH3 I OSO,Na 

CH3 

(2) stable dihydrodisulfonate, formed in warm acid solutions, prob- 
ably of the type — C — SOjNa. 

CH3 (HX) (HX) 

>C — CH.CH^CH.C — CH.CHO stable. 

CH3 I 

CH3 

(3) labil dihydrodisulfonate, formed in slightly alkaline solutions, 
probably of the type — C — OSOaNa. 

CH3 (HX) (HX) 

>C — CH.CH,CH,C — CH.CHO labil. 

CH3 I 

CH3 

(4) Citral mono sodium hydrOfeulfonate, formed by citral + labil 
citral dihydrodisulfonate CgHigCHO . SOgNa (constitution not 
known) . labil. 

(5) Citral trihydrosulfonate. 

CH3 (HX) (HX) OH 

>C — CH.CH^CH.C — CH.CH< labil. 

CH3 I OSO.Na 

CH3 

(6) A stable form of (5). stable. 

The hydrogenation of citral is of considerable industrial interest 
on account of the availability of citral in oil of lemon grass and the 
possibility of its conversion into the more valuable rose like citronellol, 
or the hydrogenation of one double bond only, yielding citronellal 
which, as noted above, is quantitatively convertible into isopulegol 
and the latter substance being convertible by hydrogenation into the 
well-known article of commerce menthol, now derived entirely from oil 
of peppermint. Skita ^"^ found that on hydrogenating over nickel at 
190°-200°, chiefly a decane was formed, and at a lower temperaturej 
140°, and under pressure Ipatiev showed that a decanol was the chief 
product. Law ^'° attempted to reduce citral by electrolytic reduction in 

'»< Client. Zentr. 1911, I, 1209. 
"»7. Chem. 80c. 101, 1024 (1912). 



200 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

alcohol acidified by sulfuric acid, but he was evidently not familiar 
with the properties of citral and related substances and it is impos- 
sible to tell from his article just what the result was.^'* According to 
Paal 1'' hydrogenation by colloidal paladium or platinum, or by cat- 
alytic masses consisting of a supporting material on which small pro- 
portions of one of these metals are deposited, converts citral first to 
inactive citronellal and then to the saturated aldehyde tetrahydro- 
citral ; geraniol is reduced to inactive citronellol and the saturated alco- 
hol tetrahydrogeraniol. (This alcohol has recently been further studied 
by Ishizaka, Ber. 41, 2483 (1914) , who also prepared it by Paal's meth- 
od.) Skita states that citral yields both citronellal and citronellol to- 
gether with a dimolecular aldehyde C20H34O2 when using colloidal 
palladium as a catalyst. 

Condensation of aliphatic aldehydes with p-naphthylamine and 
pyruvic acid usually yields well crystalline products suitable for the 
purpose of identification. Citral condenses with these two substances 
to form citryl-p-naphthocinchoninic acid, melting at 199°-200°. Cit- 
ral oxime and the phenylhydrazone' are liquid at ordinary tempera- 
tures. Cyanacetic and malonic acid condense readily yielding well 
crystalline products. 

CN CN 

C,Hi,CHO + H^C < > C^H^CH = C < 

CO2H CO^H 

CO^H. CO^H 

C,Hj,CHO + H2C< > CgHisCH = C< 

CO2H CO2H 

Citral also condenses readily with acetone in the presence of alka- 
lies, and this led Tiemann ^"^ to the discovery of the ionones. The for- 
mation of psew(io-ionone is an example of the well-known type of con- 
densation illustrated by the formation of croton aldehyde, and mesityl 
oxide. According to Tiemann's patent specifications the condensation 
is effected by means of barium hydroxide, but other condensing agents 
give better results, for example 5 per cent of sodium ethoxide in abso- 
lute alcohol.^'^ The resulting mixture is distilled and the fraction 
boiling at 138°-155° at 12 mm. is purified from unchanged citral and 
condensation products formed from acetone alone, by distilling with 

1" In the opinion of the writer, Law's experiments are of considerable Interest 
and would be worth repeating with the cooperation of a slsilled organic chemist. 
»'D. S. Pat. 1,210,681; Chem. Aia. 8. 1019 (1917). 
>»«Ber. «fi. 2675 (1893). 
>"Slaclc, Pret. & Egs. OU Record. 7, 389 (1916). 



ACYCLIC UNSATURATED HYDROCARBONS 



201 



steam, these impurities being easily volatile. By a second vacuum dis- 
tillation of this product a very pure pseudo-ionone boiling at 143°-145° 
is obtained. 



CH3 
CH3 
CH3 
CH, 



> C = CH . CH2CH3C = CH . CHO + H3C — CO — CH3 



i: 



H, 



>C = CH.CH,CH,C = CH.CH = CH.COCH3 



CH, 

pseudo-ionone. 

The physical properties of pseudo-ionone are as follows; specific 
gravity at 20° = 0.8980, refractive index -t) = 1.53346, boiling-point 
at 12 mm. = 143°-145° 

When pseudo-ionone is heated with dilute sulfuric acid, about 1 
per cent, for several hours, ring closing results, probably through the 
intermediate addition of water and subsequent decomposition, giving 
two isomeric ionones, designated as a and p. 




oc-ionone 



/^ 



-lonone 



The odors of the two isomers are noticeably different, a-ionone 
having a sweeter odor more nearly resembling orris root and ^-ionone, 
in very dilute solutions, about 1 : 10,000, resembling more closely the 
fresh wood violet. Commercial ionone is usually a mixture of the 
two isomers containing mostly a-ionone. The conditions under which 
pseudo-ionone is condensed affect the relative proportions of a and 
P-isomers, more concentrated sulfuric acid at low temperatures in- 
creasing the proportion of p-ionone while phosphoric, hydrobromic and 
hydrochloric acid yield chiefly a-ionone. Many methods have been 
proposed to separate the two isomers, of which two only will be men- 
tioned. Pure a-ionone was isolated by Tiemann by making the oxime 



202 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

of a commercial ionone containing mostly a-ionone, recrystallizing the 
oxime from petroleum ether and regenerating the ketone by means of 
dilute sulfuric acid. One method of separation is based upon the in- 
solubility of the sodium hydrosulfonate of a-ionone in aqueous sodium 
chloride solutions.^"'' If sodium chloride is added to a hot solution of 
the sodium hydrosulfonates, the a-ionone derivative separates, crystal- 
lizing in very small plates ; the (3-ionone hydrosulfonate remains in so- 
lution. Gildemeister ^"^ notes the following physical properties for 
commercial ionone; boiling-point 104°-109° (4 to 5 mm.), d^^° 0.9350 

20° 
to 0.9403, n ~ 1.5033 to 1.5051. Chuit ^'^ gives the following for the 

two isomers. 

a-Ionone P-Ionone 

Boiling-point 127.6° (12mm.) 134.6° (12mm.) 

Density, 15° 0.9338 0.9488 

Refractive index 1.50001 1.52008 

p-Bromophenylhydrazone, M. P 142°-143° 116°-118° 

Semicarbazone 107°-108° 148°-149° 

The ionones may be hydrogenated to the ketone tetrahydroionone 
by means of hydrogen and colloidal palladium ^"^ or the ketone group 
may be converted to >CH2 without affecting the double bonds.^"* 

Irone: On account of its similarity to the ionones, this ketone, an 
isomer of the synthetic violet ketones, may be mentioned here. It was 
isolated from the volatile oil of orris root and studied by Tiemann. It 
has been made by the condensation of A* cyclocitral and acetone,^"^ 
and its close similarity to the ionones is shown by the following struc- 
ture. 

Hi 




Hff \,H.CH, 



H.CH=CHCO 
I 

CH- 
CH3 XH3 ^ 

The physical properties of irone are, boiling-point 144° (16 mm), 

20° 
d^^° 0.9391, n -^r 1-5017. Its characteristic derivatives are the oxime, 

'"Chuit, Rev. Gen. CMm. 6, 432 (1903). 

"•^"Die Aetherischen Oele", Vol. I, 485. Ed. II (1910). 

""Loc. cit. 

«»Skita, Ber. J,5. 3312 (1912). 

=«Kisliner, J. Buss. Phys.-Chem. Soc. VI, 1398 (1912). 

=»'Merling & WeWe, Ann. S66, 119 (1909). 



ACYCLIC UNSATURATED HYDROCARBONS 



203 



melting point 121.5°, p-bromophenylhydrazone melting at 174°-175° 
and thiosemicarbazone melting at 181°. Irone is not made syntheti- 
cally on an industrial scale, nor isolated as such from the volatile oil 
of violet root, or orris. 

In view of the commercial value of the ionones Merling and 
Welde ^"^ undertook a study of similarly constituted unsaturated 
ketones. Any slight change in the constitution of these ke- 
tones causes considerable difference in odor. While the group 
— CH = CH — CO — CHj is essential to odors of this kind, as is 
shown by the fact that on hydrogenating the double bonds, the fra- 
grance of the ionones disappears, the particular quality of the odor is 
influenced greatly by the relative positions of the other ethylene bond 
and the methyl groups. Condensation products with acetone were pre- 
pared from the following three aldehydes, isomeric with cyclocitral. 



HO 




■CHO CH, 




CH, XH, 




HE 



CH, XH, 




-CHO 



CH, XH 



The product derived from I was almost odorless but the products 
from II and III had faint violet like odors. The most intense odor is 
obtained when the aldehyde group is situated between the methyl and 
dimethyl groups. The perfume character of such acetone conden- 
sation products disappears when the aldehyde group does not adjoin 



a methyl group. Nevertheless the grouping 



CH3 

i_CH- 
CHO 



CH, 



C< 

i: 



does 



H, 



not yield a perfume when condensed with acetone, as is shown by the 
condensation product obtained from p-isopropylbutaldehyde and ace- 
tone, but when these groups are present in the cyclogeraniolene ring, 
a perfume results. The importance of the tertiary butyl group 
— C(CH3)3, to the odor of musk, has been brought out by the work 

"•Arm. see, 119 (1909). 



204 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

of Bauer on artificial musk.^"' Austerweil ^"^ has shown that the group 
>C=;CH.CRRi appears to be necessary to produce geraniol like 

OH 
odors. 

The condensation of citral with ethyl acetoacetate has been studied 
by Knoevenagel ""^ who isolated five isomeric ethylcitrylidene acetol 
acetates. Condensation is brought about by adding a very small quan- 
tity of piperidine to a mixture of ethyl acetoacetate and citral at 
— 15° and allowing to stand two days. The structure of these con- 
densation products is not yet definitely known. 

Citral reacts normally, with methyl or ethyl-magnesium bromide 
to give secondary alcohols of rose like odor.^^" 

Sesquicitronellene, C15H24. This so-called aliphatic sesquiterpene 
was discovered in Java citronella oil by Semmler and Spornitz.^^^ It 
has four double bonds, three of which are probably conjugated. 

Mol. Ref. 74.53 

Mol. Ref. calc. for Ci5H24/=:4 69.6 



E M— 4.9 



Sodium and alcohol readily reduce it to CigHje (evidence of at least 
one pair of conjugated double bonds) and hydrogen in the presence of 
platinum black yields the saturated acyclic hydrocarbon C15H32. As 
is frequently observed among the sesquiterpenes ring closing is easily 
effected, being brought about in this case by concentrated formic acid. 
Sodium and alcohol do not reduce the cyclic hydrocarbon showing 
that ring formation has occurred through one of the conjugated double 
bonds. The original sesquicitronellene is readily oxidized and poly- 
merized. Its physical properties are, boiling-point 138°-140° (9 mm.), 
d^o 0.8489, Up 1.53252. 

Spinacene. CgoHsj. This very remarkable unsaturated hydrocar- 
bon has recently been described by Chapman ^^^ and by Tsujimoto.^^' 
It has been found in the livers of several species of the Spinacidae, a 
family of the Selachoidei, or sharks, and Chapman has therefore named 
it spinacene. In the fresh liver oils of certain species this hydrocarbon 

•"Ber. a. 2832 (1891) ; St, 3647 (1899). 

'•• Oompt. rend. ISl, 440 (1910). 

■"J. vralct. ohem. (2), 97, 288 (1918). 

»"> Bayer & Co., Cfhem. Zentr. 130J,, II, 624, 1269. 

"^Ber. 46, 4025 (1913). 

'"/. Ohem. Boo. Ul, 56 (1917) ; lis, 458 (1918). 

"•Cftero. ^68. 12. 1004 (1918). 



ACYCLIC UNSATURATED HYDROCARBONS 205 

constitutes about 90 per cent of the oil. Fish liver' oils previously 
known, such as those of the haddock, skate, hake, cod, and tunny, 
contain only about 2 per cent of unsaponifiable matter which appears 
to be cholesterol. From the standpoint of physiological chemistry, 
the manner of formation, secretion and physiological utilization of such 
an oil is of great interest, and inasmuch as the sharks are found, fos- 
silized, in many strata, geologically very old, the probability that 
shark liver oils have contributed to the formation of petroleum is at 
once suggested. 

Chemically, spinacene is of more than ordinary interest. Dry hy- 
drogen chloride passed into a cooled ether solution of spinacene forms 
the crystalline hexahydrochloride, C30H50.6HCI, and bromine in dry 
ether yields the crystalline dodecabromide CjoHgoBrij. Like chlorine 
and bromine derivatives of petroleum hydrocarbons and the terpenes, 
these spinacene derivatives are unstable and readily decompose on heat- 
ing. The hydrocarbon accordingly contains six double bonds. A moder- 
ately stable crystalline trinitrosochloride can be prepared by the usual 
methods. By catalytic hydrogenaton by means of platinum black, Chap- 
man obtained the saturated hydrocarbon CjoHgg, which is liquid at 
— 20° and therefore is not a normal paraffine. Exaltation of the re- 
fractive index and partial polymerization by metallic sodium indicate 
that probably two pairs of double bonds are in conjugated positions. 
On distilling over sodium, partial decomposition also occurs, forming a 
hydrocarbon CioHig, which appears to be a monocyclic hydrocarbon 
containing one double bond, boiling at 170°-175°, and much resem- 
bling cyclodihydromyrcene in its properties. 

Cholesterylene: The hydrocarbons resulting from the decomposi- 
tion of cholesterol or cholesteryl chloride have been repeatedly in- 
vestigated on account of the possible connection of this hydrocarbon 
with the optical activity of petroleum. The properties of "choles- 
terylene" vary considerably according to its method of preparation. 
When equal parts of cholesterol and infusorial earth are rapidly heated 
to 280°-300° a solid cholesterylene is obtained, which is capable of 
adding four atoms of hydrogen to form the solid cholestane. A sim- 
ilar mixture slowly heated for about eight hours at 300° gives an oil, 
probably a mixture, boiling at 257°-267° at 12 mm., D = 0.9572 and 
[a] J) 4- 49.12°. The product obtained by rapid heating is laevo ro- 
tatory .^^^ Cholesteryl chloride "^^ yields an oil having properties prac- 
tically identical with those noted above. 

"* Stelnkopf, J. prakt. chem. (2) 100, 65 (1919). 

"» Mauttauer & Suida, J. Chem. Soo. Aia. ISOi, I, 49 ; ISOB, I, 714. 



206 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



5 eo ■>«< 



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o 



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o 

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ACYCLIC UNSATURATED HYDROCARBONS 



207 



p ^ CO ■"< 
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208 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



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ACYCLIC UNSATURATED HYDROCARBONS 209 

1 V. Braun, Ann. 382, 22 (1911) ; Zelinsky and Prshevalsky, J. Russ. Phys.- 
Chem. Soc. 39, 1, 1168 (1907). 

2 Brooks and Humphrey, /. Am. Chem. Soc. 40, 833 (1918). 

3 Jawein, Ann. 195, 255; Ipatiev, Chem. Zentr. 1899, II, 177. 

4 Umnova, J. Russ. Phys.-Chem. Soc. 4B, 1530 (1911). 

5 Wislicenus, Ann. 219, 313; Jawein, Ann. 196, 255 (1879). 

6 Fomin and Sochanski, Ber. 46, 244 (1913). 

7 Delacre, Chem. Zenir. 1906 (1), 1233. 

8 Henry, Compt. rend. 144, 553 (1907). 

9 Kondakow, J. prakt. Chem. (2), 62, 174 (1900). 

10 Welt, Ber. 30, 1495; Przewalski, Chem. Zentr. 1909 (2), 794. 

11 Sabatier and Senderens, Compt. rend. 136, 88 (1902). 

12 Schorlemmer and Thoi-pe, Ann. 217, 150 (1902). 

13 Bjelouss, Ber. 46, 625 (1912). 

14 Sayzew, J. prakt. Chem. (2) 57, 38 (1898). 

15 Kaschirsky, Ber. 11, 985 (1878). 

16 Pawlow, Ann. 173, 194 (1874). 

17 Butlerow, J. Ricss. Phys.-Chem. Soc. 7, 44 (1875). 

18 Senderens, Compt. rend. 144, HIO. 

19 Briihl, Ann. 236, 11; Eijkwan, Chem. Zentr. 1907 (2), 1210. 

20 Muset, Chem. Zentr. 1907 (1), 1313. 

21 Sokolow, J. prakt. Chem. (2), 39, 444 (1889); Clarke and Riegel, J. Am. 
Chem. Soc. 34, 679 (1912). 

22 Grigorowitsch and Pawlow, /. Russ. Phys.-Chem. Soc. 23, 172 (1891). 

23 Mannich, Ber. 35, 2145 (1902). 

24 Freund, Ber. 24, 3359 (1891). 

25 Bjelouss, Ber. 45, 625 (1912). 

26 Grosjean, Ber. 25, 478 (1892). 

27 Kishner, Chem. Zentr. 1900, II, 725. 

28 Wallach, Ann. 408, 163 (1915). 

29 Kishner, J. Russ. Phys.-Chem. Soc. 43, 951 (1911). 

30 Wolff, Ann. 394, 86 (1912). 

31 Bjelouss, Ber. 46, 625 (1912). 

32 Grignard, Bull. Soc. chim. (3), 31, 753. 

33 Kondakow, J. Russ. Phys.-Chem. Soc. 28, 808 (1896). 

34 Thorns and Mannich, Ber. 36, 2546 (1903). 

35 Ross and Leather, Chem. Zentr. 1906 (2), 1294. 

36 Bjelouss, Ber. 45, 625 (1912). 

37 Krafft, Ber. 16, 3020 (1883). 

38 Grignard, Chem. Zentr. 1901 (2), 624. 

39 Freylon, Ann. chim. 20, 58 (1910). 

40 Klages, Ber. 36, 3586 (1903). 



Chapter VI. Polymerization of 
Hydrocarbons. 

The polymerization of unsaturated hydrocarbons is a phenomenon 
the mechanism of which is exceedingly obscure, in fact, no very plaus- 
ible theories have been advanced to explain this kind of condensation, 
although the process is accepted and utilized daily in the industries. 
When unsaturated petroleum hydrocarbons are polymerized by sul- 
furic acid it has been assumed that alkyl sulfuric acid esters are 
formed which may then condense with other molecules of the original 
olefine, with the liberation of sulfuric acid,^ 

(1) CH3 CH3 

>C = CH^ + H,SO^ > >C CH3 

CH3 CH3 I 

OSO3H 

(2) CH3 CH3 CH3 CH3 

>C CH3+ >C = CH3-^ >C = CH.C< 

CH3 I CH3 CH3 I CH3 

OSO3H CH3 

However, polymerization of hydrocarbons is brought about by a great 
variety of substances, energetic reagents such as anhydrous aluminum 
chloride or bromide, zinc chloride, ferric chloride, sulfur chloride, and 
also such substances as fuller's earth, forms of energy such as light, 
heat, the silent electric discharge and also certain metals, for example, 
metallic sodium. It is quite probable, therefore, that we shall have to 
go much deeper than the drawing of graphic formulae for plausible 
theories of polymerization; in fact, the question really is one involv- 
ing the nature of valence. It is beyond the scope and purpose of the 
present volume to go far afield in reviewing the subject of valence, 
but there are a number of phenomena, such as polymerization and the 
mechanism of organic reactions, absorption of light and its alteration 
as in fluorescence, and the decomposition of substances under the in- 
fluence of heat which are undoubtedly very closely related and, with 

iKondakow, J. prakt. cliem. Si, 442 (1896). 

210 



POLYMERIZATION OF HYDROCARBONS 211 

valence, belong fundamentally to the subject of the constitution of 
matter. The observations noted in the following discussion have been 
brought together on account of their interest to organic chemists, rather 
than for any light that may be thrown upon the mechanism of poly- 
merization. 

Ethylene, as noted elsewhere in these pages, is relatively stable, but, 
at temperatures within the range 400°-450°, condensation, in contact 
with iron or copper, is fairly rapid.^ Many substituted ethylenes con- 
taining negative groups such as chlorine, or the phenyl group, poly- 
merize on standing at room temperature, for example, styrene 
CeHjCH ^ CHj, vinyl chloride CHg = CHCl (polymerization is par- 
ticularly rapid in sunlight), 1, l-dichloroethylene CHj = C.Clj, vinyl 
bromide in sunlight, 1-chloro-l-bromoethylene CHj^C.ClBr, and 
1, 1-dibromoethylene CH2. = CBrj. These substances are rapidly oxi- 
dized by air or oxygen. On the other hand, allyl chloride and bromide, 
CH^ = CH.CH^X, trichloroethylene CHCl = CCl^, and 1.2 dibromo- 
ethylene, CHBr = CHBr are not spontaneously polymerized and are 
not appreciably oxidized on standing in contact with air or oxygen. 

Vinyl bromide, CHj = CHBr, is polymerized on standing in sun- 
light to what Ostromuislenski ^ calls a-caouprene bromide. Polymeri- 
zation under these conditions is very greatly affected by other sub- 
stances, light low boiling hydrocarbons very greatly retarding the re- 
action. This polymer, a-caouprene bromide, dissolves very readily 
in carbon bisulfide and its chemical properties are of particular inter- 
est, for example, it is quite inert to inergetic oxidizing agents and to 
concentrated mineral acids. Under the influence of ultraviolet light 
the polymerization appears to proceed further, forming what have been 
named P- and y-caouprene bromides. The |3-caouprene bromide is solu- 
ble in carbon bisulfide but the y-product is quite insoluble but swells 
in this solvent. The y-product may be converted into the soluble 
P-bromide by boiling with chlorobenzene and then precipitating with 
petroleum ether. The tetrabromide of butadiene-caoutchouc, de- 
scribed by Harries, also exists in three forms whose behavior is ap- 
parently identical with the polymerized vinyl bromides just de- 
scribed. Ostromuislenski regards the polymers of vinyl bromide as 
structurally arranged as follows, 

... CH,CHBr.CH,CHBr.CH2CHBr 



"Ipatiev, J. Chem. Soc. Aha. 19m, I, 5. 
'J. Rues. Phya.-Chem. Soc. U, 204 (1912). 



212 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Butylene, amylenes and hexylenes are more easily polymerized 
than their higher homologues and when condensation of such mono- 
olefines occurs, ring formation does not take place. 

Hydrocarbons containing two or more conjugated ethylene bonds 
are more rapidly oxidized by oxygen and are very easily polymerized, 
as, for example, butadiene (also called erythrene and divinyl) isoprene, 
dimethylallene, piperylene, the so-called aliphatic terpenes, myrcene 
ocimene, cyclopentadiene and the fulvenes, cyclohexadiene and the like. 
The structure of the polymers of these substances is known in but few 
instances, but one instance of ring formation is well known, i. e., the 
condensation of isoprene to the cyclohexene derivative dipentene. Also, 
dimethyl and tetramethylallene yield cyclobutane derivatives on poly- 
merization. 

Dimethylallene, (CH3)2C = C = CH2, is of iterest as an isomer of 
isoprene. This hydrocarbon may readily be converted to isopropyl 
acetylene, and vice versa, indicating that the internal stress in the two 
hydrocarbons is approximately of the same order, 

(CH3) ^C = C = CH2 ±5 (CH3) 2CH — C = CH. 

Tetramethylallene is also easily changed to an acetylene derivative. 
In the series beginning with allene and including methyl, dimethyl, tri- 
methyl and tetramethylallene, the stability diminishes with increasing 
substitution of methyl groups.* 

When dimethylallene condenses to the dimeric cyclobutane deriva- 
tive six isomeric hydrocarbons are possible but two have been iso- 
lated, i. 6., 

CH2 — C = C(CH3)2 boiling-point 6r-62°, 9 mm. 

CH2-C = C(CH3)2 

CH^^C — C(CH3)2 boiling-point 37°-38°, 9 mm. 

(CH3)2C-C = CH3 
Tetramethylallene condenses to the hydrocarbon.^ 

• Mereshkowskl, J. Buss. Phys.-chem. Soo. iS, 1940 (1913). Tetramethylallene was 
obtained pure for the first time by Mereshkowskl, by treating (CHs)2C=C— CH(CHs)a 

Br 
with alcoholic caustic potash in an autoclave at 130°, illustrating the marked effect 
of the double bond on the reactivity of the bromine atom. 

» This hydrocarbon has the unusually high optical exaltation of 2.596, due doubt- 
less to conjugated linkings of semi-eycUc character and also perhaps to the presence 
of the cyclobutane ring. 



POLYMERIZATION OF HYDROCARBONS 213 



(CH3),C = C = C(CH3), 
(CH3)3C = C = C(CH3), 



(CH3),C — C = C(CH3), 
(CH3),C-C = C(CH3), 



Polymerization is a property which is probably common to all sub- 
stances containing ethylene Unkings." 

In a study of the polymerization of a, p unsaturated ketones, Ru- 
zicka [Helv. chim. Acta, 3, 781 (1920) ] showed that the point of at- 
tack was the ethylene bonds, not the CO groups. 

Conjugated Dienes and the Synthesis of Rubber. 

The preparation of conjugated dienes has become a matter of great 
interest on account of the property, which some of these unsaturated 
hydrocarbons possess of polymerizing to rubber-like substances. Many 
industrially important organic substances derived from natural sources 
can also be manufactured by synthetic methods but the competition 

' Ethylene bonds undoubtedly play a very essential part in the polymerization of 
fatty oils, and the phenomenon is most pronounced in the case of highly unsaturated 
oils such as tung, linseed, walnut and certain flsh oils. However, the glycerine and 
carboxyl groups also probably enter into the process of condensation. Kronstein 
{Ber. Ji9, 722 [1916] showed that olive and cottonseed oils contain considerable pro- 
portions of glycerides which gelatinize like tung oil if the non-polymerizing portions 
of these oils are first removed by distillation. Polymerization of these oils is accom- 
panied by a decrease in their iodine absorption values. Depolymerization takes place 
readily since Morell (J. Soc. Chem. Ind. S7, 181 [1918]) has shown that the methyl 
esters, derived from polymerized tung oil, are of normal molecular weight. Salway 
[J. Boc. Chem. Ind. S9, 324T, [1920]) shows that the introduction of free fatty acids 
accelerates the polymerization of such oils (whale oil), and when the free fatty acids 
are heated, decrease of the iodine value and refractive index occurs. When the natural 
glycerides are heated, Salway supposes, (1) splitting off of free fatty acid; (2) con- 
densation of the free fatty acid with the unsaturated linkings of the fatty oil; (3) 
possible anhydride formation in which reaction the free alcoholic glyceryl radicles take 
part. 

(1) 

CHoO.OCR CH.OH. 

I i 

CH„O.OCR > CH^O.OCR. + RCO.OH. 

I I 

CH.O.OC (CHJ ,CH=CH.C,,Hi„ CH.O.OC (CHJ ,CH=CH.CiiH,„ 

(2) 

CH,OH. CH, — — CH, 

>CHAOCR C.... C... 

CH3O.OC. (CHJ ,CH— CH,.Ci,Hi, C . . . . C . . . . 

i anhydride 

.OCR formation 



214 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

of the two methods is often very close, and while the future of syn- 
thetic rubber is a matter of opinion, all chemists interested in this 
problem should keep in mind the fact that plantation rubber from 
Hevea braziliensis can be produced at a cost of approximately twenty- 
five cents per pound. The present relative importance of synthetic 
and natural rubber is not a matter of opinion, but of record, and with 
the exception of a quantity produced in Germany during the war, no 
synthetic rubber has been produced on an industrial scale or at prices 
which threaten the rubber plantations. The production of rubber from 
Hevea plantations has been much greater than the pioneers of the in- 
dustry had anticipated on account of the "wound response" of the trees 
on tapping.^ The synthesis of good gutta percha would seem to offer 
a better chance of commercial success on account of the slow growth 
of the trees yielding gutta and the apparent difficulties of solving this 
phase of the rubber business by plantation methods. Yet even in this 
case the struggle between synthetic and natural camphor is suggestive. 
Camphor trees are seldom felled for camphor distillation until they 
have reached the age of approximately fifty years, yet camphor plan- 
tations, distilling the leaves and twigs, have been undertaken on an ex- 
tensive scale and the cost of manufacturing synthetic camphor has 
increased with the higher cost and diminishing supply of turpentine, 
the necessary raw material. 

The history of the subject^ of artificial rubber has been marred 
by polemical controversies which have arisen largely on account of 
definitions and the difiiculty of determining just what rubber is struc- 
turally and the difficulty of proving the identity of such amorphous 
substances. As regards the question of the identity of polymerized iso- 
prene rubber and natural Hevea rubber, it now appears that the former, 
when made either by polymerization by metallic sodium or by per- 
oxides, is not homogenous, as is indicated by the fact that the ozonides 
yield succinic acid, acetonylacetone, laevulinic aldehyde and laevulinic 
acid, corresponding to the two dimeric isoprene complexes 1.5-di- 
methyl-A^-^-cyclo-octadiene and 1 .6-dimethyl-A^''-cyclo-octadiene.* 
Natural Hevea rubber, on the other hand, appears to be a homogenous 
product, the ozonide decomposition products being referrable to the 

' Parkin, Rubber Cultivation in the Far East, Science Progress. I. Jan. 1910 ; II. 
April, 1910. According to Eaton, Chem. Trade J. 1921, 242 approximately 2,000,000 
acres are under cultivation for rubber. 

8 Cf. Pond, J. Am. Chem. Soc. 36, 165 (1914) ; Luff, J. Soc. Chem. Ind. So, 983 
(1916) ; Perkin, J. Soc. Chem. Ind. 31, 616 (1912) ; Gottlob, Indiana Rubber J. 58, 305, 
348, 391, 433 (1919). 

•Stelmmlg, Ber. j^t, 350 (1914). 



POLYMERIZATION OF HYDROCARBONS 215 

1.5-dimethyl-A^-^-cyclo-octadiene complex. The first direct evidence 
obtained by Harries of an eigiit carbon ring complex was later shown 
to be incorrect, the ketone then considered to be cyclo-octane-1 .5-dione 
proving to be impure heptane-2 . e-dione.^" For practical purposes, 
however, Ostromuislenski is little concerned with chemical standards 
of comparison between natural rubber and synthetic colloids resembling 
them, and advocates ^^ a classification based upon the temperatures at 
which the colloid acquires and loses its elastic properties, and the 
range between these temperature limits. When these agree closely 
with the values for natural caoutchouc he proposes that the colloid be 
classed as normal, regardless of its ozonide decomposition products. 
Considering the conflicting results of different experimenters with the 
ozone method, and the difficulties of such work, the proposed classifi- 
cation would probably be as consistent and also more useful. 

Harries has contended that the earlier investigators, who discov- 
ered the polymerization of isoprene, did not really produce caoutchouc, 
but the question seems a futile and purposeless one. That isoprene 
could be polymerized to an amorphous rubber-like substance was evi- 
dent from the early work of Greville Williams ^^ who did not recog- 
nize his product as rubber, but whose description of the product, to- 
gether with the results of later repetition of his work, indicate that his 
product was in fact rubber, and Bouchardat^^ who, in 1875, treated 
isoprene with concentrated hydrochloric acid at 0°, and Tilden^^ 
who obtained a similar product in 1882 and announced later, 1892, that 
isoprene polymerizes spontaneously on long standing in the light and in 
contact with air." Wallach " showed that light causes the polymeri- 
zation of isoprene in a sealed tube, but the change is more rapid in 
contact with oxygen or air. The polymerization of isoprene and sim- 
ilar dienes is more fully discussed in a separate section on the prop- 
erties of unsaturated hydrocarbons. 

As regards the preparation of the dienes, it is possible to note 
processes which are of industrial promise and, processes which are not 
likely to become commercial on account of the cost of raw materials or 
operating diflSculties, or both. 

"Harries, Ber. p, 784 (1914). 

"■Ct. J. Russ. Phya.-Chem. Roc. 1,1, 1928 (1915). 

"PAa Trans. ISO, 254 (1860). 

^'Oompt. rend. 89, 361, 1117 (1879). 

"Chem. News. J/S, 220 (1882). 

"Ohem. News, 65, 265 (1892). 

"Ann. in. 295 (1885). 



216 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The earlier workers prepared isoprene by the destructive distilla- 
tion of rubber, a typical distillation yielding the following products: 

Isoprene 6.2 per cent 

Dipentene 46.0 " " 

Higher boiling oils 43.8 " " 

Carbonized residue 1.9 " " 

Loss and mineral matter 1.9 " " 

The formation of isoprene by pyrolysis of turpentine was first 
noted by Hlasiwetz ^^ who passed turpentine through a "red-hot" iron 
tube packed with broken porcelain. A large number of products were 
obtained and isoprene was not then actually identified in the low boil- 
ing fraction, but Tilden^^ later repeated this work and proved the 
formation of isoprene in this manner. The yields of isoprene obtained 
by the pyrolysis of turpentine and dipentene vary greatly and are gen- 
erally very low. Harries ^^ obtained 10 per cent of isoprene by decom- 
posing commercial pinene by means of his isoprene lamp (wires heated 
electrically to low red heat) . Herty and Graham '" reported yields of 
5.5 to 8 per cent from turpentine fractions, and 12 per cent from 
limonene while Harries obtained yields of 30 to 50 per cent from the 
latter hydrocarbon. By decomposing under reduced pressure, 4 mm., 
yields as high as 60 per cent are said to be possible from limonene.^'' 
Schorger and Sayre ^^ also report low yields from turpentine, the two 
pinenes, a and P, giving substantially the same yields. Very little 
attention has been paid to the temperature required for optimum 
yields of isoprene but, in contact with glass or porcelain, this tem- 
perature appears to be 550° to 600°.^^ According to Ipatiev, the con- 
densation of isoprene to dipentene is fairly rapid at 300°. 

Small yields of butadiene and isoprene can also be obtained by the 
pyrolysis of petroleum oils and have been identified in the low boiling 
fractions of the light oils obtained by compressing oil gas or Pintsch 
gas to 150 to 200 pounds pressure. However, the fact that they have 
been detected in these pyrolytic products is a tribute to the analytical 
skill of the chemists who investigated these hydrocarbon mixtures." 
Nevertheless, the preparation of isoprene and butadiene by the pyroly- 

"Ser. 9, 1991 (1876). 

"J. Chem. Soc. iS, 410 (1884). 

"Ann. SSSj 228 (1911). 

"J. Ind. & Eng. Chem. 6, 803 (1914). 

" Staudinger & Klever, Ber. U, 2212 (1911). 

"J. Ind. i Eng. Chem. 11. 924 (1915). 

2« Mahood, J. Ind. & Eng. Chem. m, 1152 (1920) ; Helnemann, Brit. Pat. 14,040 ; 
24,236 (1910) ; 1953 (1912) ; Stephen, D. S. Pat. 1,057,680 ; Ostromuislenskl, French 
Pat. 442,980 (1912) ; Sehering, German Pat. 260,934 (1913). 

"Armstrong & Miller, J. Chem. Soc. i9, 74 (1886). 



POLY MERtZAf ION OF HYDROCARBOMS 2i7 

sis of petroleum oils at about 7D0°, particularly in vacuo,^^ has re- 
cently been patented. This method presumably would give better re- 
sults with light petroleum oils containing cyclohexane, cyclopentane, 
and their simpler homologues, since it has been claimed that tetra- 
hydrobenzene yields a certain proportion of butadiene on decomposition 
under these conditions. ^° However, in the ten years which have elapsed 
since this work was done, there have been no industrial developments 
along this line and considering the small yield of the desired dienes, 
the value of petroleum oils for other uses, and the difficulty of purify- 
ing the desired hydrocarbons, it is very doubtful indeed if the direct 
pyrolysis of hydrocarbons will ever prove to be an economic method 
of producing these hydrocarbons. In this connection, it should be 
noted that Ostromuislenski " has shown that on polymerizing iso- 
prene containing amylene or similar olefines, the resulting "rubber" is 
very sticky and soft. 

Petroleum pentane is mostly normal pentane but attempts have 
been made to utilize this hydrocarbon as a raw material for the manu- 
facture of isoprene. It may be said of all the chemical methods for 
the preparation of these unsaturated hydrocarbons that no really new 
methods or reactions have been developed; all of the known methods 
of producing unsaturated hydrocarbons have been applied to the prepa- 
ration of these dienes but the great majority involve the elimination of 
halogens, usually chlorine, or of hydroxyl groups in the form of water. 
The production of isoprene from normal pentane involves the change 
to the carbon structure of isopentane. This is accomplished by one 
patentee ^* by taking advantage of the isomerization of olefines effected 
by heat, which has already been noted in the case of the butylenes. 
Thus pentane is chlorinated to a mixture of the monochlorides and 
these are converted to amylenes by pyrolysis in contact with barium 
chloride, lime or other methods, and the mixture of amylenes then 
passed over alumina at about 450°. Partial rearrangement to tri- 
methylethylene occurs and on treating the resulting mixture of amyl- 
enes with hydrogen chloride this hydrocarbon reacts most readily, the 
chloride thus formed being separated by fractional distillation. The 
hydrocarbons thus separated are passed again over alumina at 450°, 
and so on. The purified monochloroisopentane is converted to tri- 
methylethylene by the usual methods and this treated with chlorine to 

a«Bngler and Staudinger, Ber. 48, 2468 (1913) ; German Pat. 265,172 (1912). 
*■ Farbenfabr, Elberfeld, German Pat. 241.895. 

='J'. Russ. Phya.-Ohem. Soc. JiS, lOYl (1916) ; Chem. Ab8. 11, 1768 (1917). 
^Badische, German Pat. 280,596 (1919). 



218 CHEMISTRY OF THE NON-BENZENOID HYDltOCARBONS 



form the dichloride which then forms isoprene with the elimination of 
two molecules of hydrogen chloride. The reactions involved are as fol- 
lows: 

CH3CH3CH2CH2CH3 > monochlorides > 



amylenes - 
CH, 



rCHj 

>C = CHCH, 
CH3 

and isomers 



- + HCl ■ 



CH, 



CH3 



>CC1.CH2CH3 



■^CH, 



CH, 



>C = CHCH3 



(pure) 



>CC1.CHC1.CH3 



■^CH, 



\ 



/ 



C — CH = CH.. 



CH3 

Petroleum pentane is one of the cheapest raw materials which have 
been suggested for this purpose but the process involves a large num- 
ber of operations, distillations, purification of intermediates and the 
losses are large, for example, if each operation indicated above gave a 
yield of 90 per cent the final net yield of isoprene would be about 47 
per cent. Pentane can, in fact, be chlorinated to monochloropentanes 
with a yield of about 90 per cent, exclusive of vaporization losses, but 
the losses on isomerizing the amylenes are large and it is impossible 
to chlorinate trimethylethylene without partially chlorinating further 
to trichlorides and tetrachlorides. 

Several patented processes employ phenol and cresols as raw ma- 
terials. Phenol may be hydrogenated to cyclohexanol, with good 
yields, and this alcohol may then be dehydrated by heating in contact 
with alumina, thoria or kaolin, to give cyclohexene. Cyclohexene gives 
small yields of butadiene and ethylene by direct pyrolysis, 

CH2 

/ \ 

H,C CH 



H.,C CH 

' \ / 

CH, 



-> CH, =: CH — CH = cn, + CJi, 



POLYMERIZATION OF HYDROCARBONS 219 

Chlorination of cyclohexene to the dichloride, and then decomposing 
this, yields the conjugated diene, cyclohexadiene, but this hydrocarbon 
polymerizes to a substance more nearly resembling resin than rubber. 
Benzene itself is readily hydrogenated to cyclohexane and this may be 
converted to cyclohexene through the monochloro derivative by the 
usual methods ^° but none of these materials yield final products of 
good quality. 

It is much easier to prepare isoprene and butadiene, and in much 
purer condition, by using butyl or isoamyl alcohol as the raw ma- 
terials. A new method for the manufacture of n. butyl alcohol has 
been developed based upon the fermentation process of Fernbach,^'' 
the two principal products being n. butyl alcohol and acetone. Al- 
though originally developed in connection with the synthetic rubber 
problem it was carried out on a large scale diuring the recent war, 
essentially as a process for the manufacture of acetone. At com- 
paratively high temperatures butyl alcohol is decomposed partially to 
butadiene ^^ but, as in many pyrolytic processes, the yields are small. 
The alcohol may be converted to the corresponding chloride and the 
resulting butyl chloride then chlorinated to the dichlorides which may 
then be decomposed by methods already mentioned, to butadiene,^^ 

CH3CH2CH2OH > CH3CH2CH2CI > dichloride > butadiene 

By similar methods isoamyl alcohol, the chief constituent of fusel oil, 
may be converted by hydrogen chloride to isoamyl chloride, which on 
chlorination yields a mixture of dichlorides, 

(CH3)2CH.CHC1.CH,C1 boiling-point 142° C. 

(CH3)2CC1.CH,CH2C1 " " 152° C. 

CH2CI 

>CH.CH2.CH2C1 " " 170° C. 

CH3 

Of these dichlorides the second is the principal product, but the crude 
mixture, boiling-point 140°-180°, is used for the production of isoprene, 
the yield, according to Perkin,^^ being 40 per cent of the theory. As 
pointed out by Perkin the total available quantity of ordinary fusel 
oil, about 3500 tons, is wholly inadequate as a raw material for rub- 

2" Schmidt, Hochschwender & Eichler, U. S. Pat. 1,221,382. 

"Fernbach & Strange, Brit. Pat. 15,203; 15,209; 16,925 (1910). The butyl 
alcohol contained in ordinary fusel oil from the manufacture of alcohol la Isobutyl 
alcohol and is only a minor constituent. 

"Perkin & Mathews, J. Soc. Chem. Ind. S2, 884 (1913). 

■=Cf. Badiache, German Pat. 255,519 (1913); 264,008 (1911); Harries, German 
Pat. 243,075; 243,076 (1910) ; Brit. Pat. 18,653; 22,035 (1912). 

"J. Soc. Chem. Ind. SI, 616 (1912). 



220 CHEMISTRY OF fHS NON-BSNZENOID ttybROCARBONB 

ber synthesis, and is relatively high priced on account of its many in- 
dustrial applications. The per cent of isoamyl alcohol in commercial 
fusel oil varies somewhat according to the distillation range over 
which it is collected, but the fraction distilling at 128°-131° contains 
approximately 87 per cent isoamyl and 13 per cent active amyl alcohol 
C2H5CH(CH3) .CHjOH. Two typical analyses of commercial fusel 
oils are as follows,^* 

Fromjermentation Percent From fermentation Percent 

of potatoes by wt. of com by wt. 

n. Butyl alcohol 6.8 n-Propyl alcohol 3.7 

Isobutyl alcohol 24.3 Isobutyl alcohol 15.7 

Amyl alcohols 67.8 Amyl alcohols 75.8 

Fatty acids 04 Hexyl alcohols 0.2( ?) 

Fatty acids 56 

It is probable, in view of the researches of Ehrlich,^^ that such varia- 
tions in the character of fusel oils are due to differences in the yeasts 
employed for fermentation or proteins otherwise introduced rather .than 
the materials fermented. A sample of fusel oil from corn, examined 
by Pringsheim,^^ contained isopropyl and normal butyl alcohols in ad- 
dition to the normal propyl and isobutyl alcohols which are normally 
present in fusel oil from this source. 

In view of the efforts which have been made to utilize cheap fer- 
mentable material and the resulting butyl and amyl alcohols, as raw 
material for rubber synthesis, this phase of the work is reviewed here. 
Ehrlich claims that in ordinary yeast fermentation the fusel oil alco- 
hols are derived from the decomposition of protein material, or rather 
the amino acids leucine, isoleucine and the like, 

(CH3)2CH.CH2CH< +H2O 

leucine 00,11 

> (CH3),CH.CH2CH30H + CO^ + NH, 

isoamyl alcohol. 

Ehrlich established the following relations, 

(1) Pure yeast and pure sugar yields no fusel oil. 

(2) " " " " " + leucine yields isoamyl alcohol. 

(3) " " " " " -f isoleucine yields d. amyl alcohol. 

The addition of ammonium carbonate or asparagin to yeast fermen- 
tations decreases the yield of fusel oil and the addition of leucine, or 

" "The Nitrocellulose Industry", Worden. 

"=Cf. Brit. Pat. 6,640 (1906) ; Ber. 1,0, 1027 (1907). 

"Biochem. Z. IB, 243 (1909). 



POLYMERIZATION OF HYDROCARBONS 221 

protein rich in this complex, increases it. Only traces of fusel oil are 
formed by alcoholic fermentation by means of Buchner's cell-free 
pressed yeast juice.^' However, normal butyl alcohol at least can be- 
come, under certain conditions, one of the principal products derived 
from the sugar undergoing fermentation. Realizing the inadequacy of 
the supply of commercial fusel oil for possible rubber synthesis, Per- 
kin and his associates undertook to develop a special process of fermen- 
tation which would yield larger proportions of butyl or amyl alcohols. 
Although the anaerobic Bacilliis butylicits was discovered by Fitz ^' in 
1878 in a study of glycerine fermentation, and Perdrix '" had described 
an anaerobic bacterial fermentation which gave very high yields of 
fusel oil, it does not seem to have occurred to anyone else to utilize this 
possibility until it had been developed by Fernbach and Strange.*" As 
has been previously noted both the major products of this fermenta- 
tion, acetone and n . butyl alcohol, are necessary raw materials required 
by. several different processes for the production of butadiene and 
dimethyl butadiene. 

All of the known methods of decomposing alcohols to unsaturated 
hydrocarbons have been applied to the problem of producing these sim- 
ple conjugated dienes. Butyleneglycol yields butadiene when passed 
over heated kaolin, alumina, or aluminum phosphate.*^ The butylene- 
glycol, required by this process, can be made from acetaldehyde, the 
primary raw material therefore being ethyl alcohol or acetylene. Acet- 
aldehyde may be condensed by well-known methods to aldol, which 
upon reduction yields butylene glycol, 

Alcohol, or acetylene —> acetaldehyde— ^CH3CH( OH) .CH^CHO 

-^ CH3CH (OH) . CH,CH,OH ^ CH, = CH . CH = CH^ 

Butyraldehyde yields a certain amount of butadiene when passed over 
kaolin at 500°-600° under reduced pressure *^ and isovaleric aldehyde 
yields some isoprene under the same conditions.*^ Secondary butyl 
alcohol can be prepared by (1), reduction of the commercial solvent 
methyl ethyl ketone, derived from "acetone oil," or (2), treating oil 
gas with 80 per cent sulfuric acid and hydrolysing the butyl hydrogen 

"Buchner & Meisenheimer, Ber. 30, 3201 (1906). 
"Ber. 11, 481, 878 (1878). 
"Z. Spwitusind. U, 17T (1891). 
« French Pat. 488,364 (1913). 

"Mathews, Strange & Bliss, Brit. Pat. 3,873 (1912); Cf. Bayer, German Pat. 
261,642 (1913). 

«U. S. Pat. 1,033,327. 
«U. S. Pat. 1,033,180. 



222 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

sulfate so formed. The secondary butyl alcohol may then be decom- 
posed catalytically, with very good yields, to butylene, which on 
chlorination or bromination and subsequent decomposition, yields bu- 
tadiene. As has already been noted, it is very difficult completely to 
remove halogens from such substances on account of the stabilizing in- 
fluence of an adjacent double bond, the second 

( 1 ) CH3CHBr . CHBr . CH3 > CHjCHBrCH = CH^ 

(2) CHaCHBr . CH = CH, > CH, = CH — CH = CH, 

reaction taking place with difficulty (higher temperatures) and when 
the temperatures are sufficiently high for the complete removal of halo- 
gen, loss of the desired diene occurs through secondary reactions. 

The condensation of acetaldehyde and ethyl alcohol by passing over 
heated copper, followed by decomposition of the condensation product 
by passing over heated alumina, has been noted by Ostromuislenski ** 
as a possible method, and the chemical changes, which really involve 
five consecutive reactions, may be summarized as follows: 

2C2H,OH -^ CH3CHO + C^H.OH -^ CH^ = CH . CH =GH^ + 2H,0 

The yields of butadiene are poor and considering the number of other 
reactions which also occur in this process, it is not likely to become 
of industrial interest. 

That tertiary alcohols are much more easily decomposed to un- 
saturated hydrocarbons, than secondary and primary alcohols, is well 
known, and advantage is taken of this fact in the employment of 
pinacone as an intermediate product. Thus acetone may be reduced 
and condensed to pinacone under a wide range of conditions and the 
use of amalgams for this purpose is particularly promising.*' Pinacone 
is smoothly decomposed by passing over alumina at about 400° giving 
good yields of dimethylbutadiene.*' 

acetylene { 

acetate of lime i > acetic acid 

I ^^ \ 

starches and sugars j ^"^ ^ > acetone > 



starches and sugars 

"X Runs. PJiya.-Chem. 8oc. p, 1472, 1494 (1915) ; J. Chem. 8oc. Ats. 1916, I, 4. 
» HoUeman, Rec. trav. chim. is, 206 (1906) ; Bull. soo. cMm. 1910, 454. 
«• German Pat. 250,086. 



POLYMERIZATION OF HYDROCARBONS 223 

CH3 CH3 CH^ CH, 



CH„ 



C — C > c — c 



CH3 CH, CH 



OH OH 



3 
dimethylbutadiene 



The synthetic rubber manufactured in Germany during the recent war 
was made from pinacone and dimethylbutadiene, the latter material 
being polymerized in sealed iron drums during a period of several 
months. 

Pinacone chlorohydrin also yields dimethylbutadiene, when heated 
with bases, dimethylaniline being recommended for this purpose," and 
Kondakow *' claims that pinacone dichloride gives better yields of the 
diene than pinacone itself. Decomposition of the alcohol pentene-2, 
ol-4 by passing over alumina or kaolin at 400° has been employed 
for the preparation of piperylene. Under certain conditions acetalde- 
hyde condenses to crotonic aldehyde and on methylating this aldehyde 
pentene-2, ol-4 is formed. 

OH 
2CH3CHO -^ CH3CH = CH . CHO — > CH3CH = CH . CH< 

CH, 



■ CH,CH = CH.CH = CH. 



Many methods have been described which make use of well-known 
syntheses, but which are interesting from a theoretical point of view. 
Kyriakides *° has described an interesting synthesis starting with chlo- 
roacetone, which is ethylated, and the resulting chlorohydrine is then 
treated with caustic alkali to obtain the oxide, as indicated in the fol- 
lowing, 

CH3COCH2CI > CH3 CH3 

>C — CH, > >C — CH, 

C,H, I I C,H, \/ 

OH CI 

CH3 

/ 

*CH, = CH.C 

\ 
CH, 

"German Pat. 319,505 (1916). 
"J. prakt. Chem. 62, 169 (1900). 
"J. Am. Chem. Soe. S6, 663 (1914). 



224 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The oxide is decomposed by heating in the presence of kaolin at 
440°-460°. 

Dimethylallene may be partially converted into isoprene by re- 
arrangement °'' and Ipatiev °^ has prepared isoprene from this hydro- 
carbon by adding two molecules of hydrogen bromide, followed by de- 
composing the dibromide by well-known methods, 

CHg CII3 

> C = C = CH, + 2HBr > > CBr . CH,CH,Br 

CH3 CH3 

CH, 

\ 
> C — CH = CH, 

/ 
CH3 

Among the reactions of theoretical interest which have been em- 
ployed in research in this field, may be mentioned Euler's ^^ prepara- 
tion of isoprene by the exhaustive methylation of methylpyrollidine, as 
follows, 

CHg — CH — CHj 

>NH + 2CH3I + NaOH > 



CH, — CH, 



2 



CH3 — CH — CHj CH3 — C == CH2 

I >N{CH3)J-^ I 

CH^ — CH^ CH — CH — N (CH3) 

+ CH3I 
> CH, — C == CH 



2 



CH 



2 



+ KOH 
2 — CH, — N(CH3)3l > CH3 — C == CH, 



iH = 



CH, 



isoprene 

It will be recalled that this method has been frequently used by von 
Braun and others in the investigation of alkaloids, on account of the 
ease with which nitrogen can be removed from organic bases. 

Phenol may readily be hydrogenated to cyclohexanol, which on oxi- 
dation by nitric acid =^ yields adipic acid. Conversion of this acid to 

»»Webel (U. S. Pat. 1,083,164), elalms that ax. dimethylallene rearranges to 
isoprene when passed over alumina at 300°, and preferably under diminished pressure 
"J. prakt. Chem. 55, 4 (1897). e <= •><! <:, 

"J. pram. Chem. 57, 132 (1898). 
" BouTeault and Locquin, Bull. 8oc. chim. 1908, S, 437. 



POLYMERIZATION OF HYDROCARBONS 225 

the amide, followed by treatment with hypochlorite, yields tetramethyl- 
enediamine and the method of exhaustive methylation applied to this 
diamine yields butadiene; cresol, treated similarly, yields isoprene. 

Polymerization of Conjugated Dienes to Rubber-like Substances. 

As pointed out elsewhere in these pages the polymerization of iso- 
prene had been observed by Greville Williams, Bouchardat, Tilden and 
Wallach. But the first attempt to polymerize isoprene which had been 
prepared from sources other than rubber itself was Tilden's investiga- 
tion of isoprene made by the pyrolysis of turpentine, published in 
1888." Tilden states that, "The action of hydrochloric acid on iso- 
prene converts it partially into caoutchouc ; the latter seems to be ob- 
tained more easily starting with the oily polymeride resulting from the 
action of heat." Some 28 years later, Ostromuislenski ^^ showed clearly 
that the character of synthetic isoprene rubber was markedly affected 
by the method of polymerization ; that on heating isoprene to 80°-90'' 
it undergoes spontaneous polymerization to a dimeride, p-myrcene, and 
this hydrocarbon then yields "normal" caoutchouc when polymerized 
by sodium, or barium peroxide. However, when isoprene itself is 
treated with these reagents the resulting rubber is not normal."" Til- 
den seems to have been aware all along that rubber might be formed 
by the polymerization of isoprene. The polymerizatioj i of the isomeric 
hydrocarbon piperylene, CH3CH = CH — CH = CH2 had been ob- 
served by Hofman " and by Schotten,"* but their publications contain 
no suggestion that their product resembled rubber. In 1892 Tilden,"* 
in a communication to the Philosophical Society of Birmingham, 
stated, "I was very much surprised to find that the contents of the 
flasks containing isoprene, prepared from turpentine, had entirely al- 
tered in appearance. Instead of a colorless, limpid liquid, there was 
now a thick syrup, in which floated several pieces of a yellow solid 
material. On examining it more closely this was found to be caout- 
chouc." * « * "A solution of synthetic rubber leaves, on evapora- 
tion, a residue which completely resembles in all its characteristics a 
like preparation made with Para rubber." • " * "Artificial rub- 
ber combines with sulfur in the same way as natural rubber, giving 
an elastic, resistant mass." A little later Tilden's results were con- 

"/. Chem. Soc. i5, 411 (1888). 

"J. Russ. Phys.-Chem. Soc. ^, 1071 (1916). 

"J. Russ. Phys.-Ohem. Soc. kt, 1928 (1915). 

"Ber. U, 665 (1881). 

"Ber. IS, 425 (1882). 

" Ohem. News, es, 265 (1895). 



226 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

firmed by Weber ^" who prepared about 200 grams of synthetic iso- 
prene rubber, and Pickles *^ also confirmed Tilden's statement that 
isoprene polymerizes on standing in contact with air. 

The marked influence of oxygen upon the formation of polymers is 
well shown by experiments reported by Engler,*^ in which duplicate 
samples were exposed to oxygen and carbon dioxide, at 80° C. The 
very rapid polymerization of styrene, and the conjugated dienes, iso- 
prene and myrcene, are particularly noteworthy. 

Per cent poltmers formed on standing. 

In contact with CO2 In contact with Oi 

Days exposed ISS4IZS4 

Limonene 2% 4% 5% 8% 4% 6% 8% 9% 

Phellandrene 4 6 8 9 9 13 16 21 

Pinene 12 2 3 3 4 4 5 

Myrcene 8 13 18 22 20 30 40 50 

Camphene 3 4 5 6 5 7 8 9 

Isoprene 14 per cent in 10 hours; 35 per cent, 10 hours 

Styrene 22 per cent, 20 hours; 67 per cent, 20 hours 

The presence of moisture apparently has no effect upon the rate of 
polymerization of hydrocarbons, although the smallest trace of mois- 
ture acts catalytically upon the polymerization of the aldehyde, gly- 
oxal;'^ monomolecular succinic dialdehyde behaves in a sirnilar man- 
ner. 

The polymerization of dimethyl butadiene, dimethyl 2-3 buta- 
diene 1-3, to a rubber-like substance was first effected by Kondakow,^* 
who noted that it polymerized spontaneously and more rapidly than iso- 
prene or butadiene. His publications upon the polymerization of this 
dimethylbutadiene, which he prepared from pinacone, would seem to 
justify Kondakow's claims of priority, so far as the dimethylbutadiene 
process, later patented and used industrially in Germany, is concerned. 
It was noted also, and confirmed by others,*^ that when dimethyl 
butadiene polymerizes, either spontaneously or in the presence of alco- 
holic caustic potash, a dimeride and a trimeride are produced, in addi- 
tion to the rubber-like substance. It was important for the technicali- 
ties of later patent controversies that Kondakow had described his di- 
methylbutadiene rubber as insoluble in most organic solvents, although 
it is now generally recognized that this property varies considerably 

"J. Soc. Chem. Ind. IS, 11 (1894). 
«J^. Chem. Soc. 97, 1085 (1910). 
"8th Int. Crnigr. Appl. Chem. 25, 661 (1912). 
«» Harries, Ber. Ifi, 165 (1906) : il, 255 (1908). 
"J. prakt. Chem. H, 109 (1901). 

"Lebedew, J. Busa. Phys.-Chem. Soo. il, 1818 (1909); Harries, Ann. S8S. 210 
(1911). 



POLYMERIZATION OF HYDROCARBONS 



227 



with all rubbers, depending upon the degree of polymerization ; in fact, 
vulcanization is essentially a process of effecting higher degrees of 
polymerization. It is well known also that dimethylbutadiene poly- 
merizes more rapidly than other similar hydrocarbons. Perkin states, 
"The situation in 1906 might be summed up in this way; it had been 
recognized, in a more or less general way, that most compounds con- 
taining a system of conjugated double linkings, show a tendency to 
polymerize, more or less readily. The polymerides are either viscous, 
ill defined substances, or well characterized caoutchoucs; or, again, 
hard resinous solids, like polystyrene. Their properties vary accord- 
ing to their method of preparation, and according to the molecular 
weight of the hydrocarbon employed as a raw material." 

Like natural Para rubber, Kondakow's rubber can be de-polymer- 
ized by heat, although more readily than Para rubber, the principal 
product being a dimeric dimethylbutadiene resembling dipentene and 
which Richard °° and Kondakow regard, as having the structure. 



CK 



or 





The same hydrocarbon is also formed by. careful polymerization of 
2.3-dimethylbutadiene-(1.3). In the polymerization of isoprene to 
synthetic isoprene rubber a dimeric isoprene is formed, in addition to 
the dimeride, dipentene. This second hydrocarbon, called di-isoprene 
or myrcene by earlier writers, yields a liquid tetrabromide, in con- 
trast to the crystalline dipentene tetrabromide. According to Lebedew 

" Compt. rend. 15S, 116 (1911) ; According to Lebedew and Mereshkowski (J. Rues. 
Phi/s.-Chem. Soo. is, 1249 [1913]) this dimeride has the following properties; boiling- 
point 85° at 13 mm., 205° at 750 mm., D j. 0.8741 nj) 1.48074 ; dry HCl yields a 

Me 
//C.Me.CHs / 

monohydrochloride MeC >C.Me.CCl , boiling at 122°-124° under 17 mm.; 

\CH2CHa \ 

Me 
oxidation by benzoyl peroxide, according to Prlleschajev (q.v.) yields a dioxide which 
is hydrolyzed by aqueous benzoic acid to a tetrahydrlc alcohol- 



228 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



and Mereshkowski " this hydrocarbon is 1 . 3-dimethyl-3-ethenyl-A«- 
cyclohexene.*^ On hydrogenating in the presence of platiniim the side . 
chain ethenyl group is first saturated, following the general behavior 
of substances containing double bonds in both the ring and side chain. 



CH^ 





CH=CH, 




.CH, 



CH,CHj 




Piperylene similarly should yield two dimerides. Butadiene yields a 
dimeride, CgHi^, boiling at 36° under 23 mm., 129.5°-131° under 
760 mm. pressure. Hydrogenation by Paal's method yields ethyl cy- 
clohexane; bromine reacts to form a tetrabromide melting at 69.5°- 
70.5° and oxidation yields the acid 



CO^H 

from which facts, and reasoning by analogy from the relations between 
isoprene and dipentene, Lebedew "^ concludes that the hydrocarbon is 
l-ethenyl-A*-cyclohexene, 

CH — CH, 



CH 



/ 

r 
\ 



\ 



CH.CH = CH, 



CH, — CH, 



/ 



These details are of first importance as the yield of synthetic rubber, 
by present methods of polymerization, is seriously diminished by the 
formation of these oily polymers. 

As to why or how sodium effects the polymerization of isoprene, 



" Loc. cit. 

MCf. Harries, Arm. S8S, 157 (1911). 

"J. Ritas. Phya.-Chem. Soc. iS, 1124 (1911). 



POLYMERIZATION OP HYDROCARBONS 229 

no one has hazarded a theory. Perkin '"' relates that Weizmann and 
Mathews were induced to try the effect of permitting the hydrocarbon 
to stand in contact with the metal, by their having noted the conversion 
of dimethylallene to isopropylacetylene by metallic sodium, 

(CH3) ^0 = = CH2 (CH3) 2CH — C = CH, 

a reaction which had been recorded by Favorsky.^^ This discovery, 
the polymerization of isoprene by sodium, was, according to Perkin, 
made by Weizmann and Mathews in July and August, 1910, although 
it was first publicly described in the ioUowing year by Harries.'^ The 
same discovery had evidently been made by Harries in the "en\.\ of 
(the year) 1910." 

The polymerization of hydrocarbons may, according to Lebedew 
and Mereshkowski '^ be grouped in several well defined classes, (1), 
the styrene type, peculiar to ethylene hydrocarbons with unsymmetri- 
cal substitution of the hydrogen atoms by phenyl, or other groups, and 
yielding amorphous polymers of very high molecular weight and whose 
structures are not yet known; (2) the stilbene type, shown by sub- 
stances having symmetrically substituted groups; (3) the acetylene 
type, whose characteristic is the formation of benzene or its deriva- 
tives; (4) the allene type, yielding cyclobutane derivatives; (5) the 
1 .3-butadiene or isoprene type, which forms cyclohexane derivatives 
and also polymers of high molecular weight, usually amorphous, and 
including rubber-like substances. The structures of the polymers of 
the styrene and stilbene type, when ascertained, may show that these 
two classes are really of the same type of polymerization. 

With isoprene and 2.3-dimethylbutadiene-(1.3) it has been shown 
that with increasing temperature the proportion of the dimeride in- 
creases and that of the rubber-like polymer decreases. Since the re- 
action is markedly affected by catalysts, it follows that, for maximum 
yields of "synthetic rubber," a catalyst and the lowest possible temper- 
ature should be employed. The ^earch for raw materials for the prepa- 
ration of the simpler conjugated dienes, and the effort to discover effi- 
cient methods for the preparation of these hydrocarbons has involved 
a great deal of research. The finishing step in the process, polymeri- 
zation, is still without a theory sufficiently tangible or plausible to be 
of use as a guide for further work. There has been a very noticeable 

'"Loc. cit. 

"J. Rusa. Phys.-Chem. Soc. 19, 558 (1887). 

"Atm. S8S, 157 (1911). 

"J. Russ. Phys.-OJiem. 80c. i5, 1249 (1913) ; J. Chem. Soc. Abs. 19a, I, 1285. 



230 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

abatement of research on rubber synthesis since 1912 (the manufacture 
of synthetic rubber may have been, for Germany, a war preparedness 
measure) . It is certain that all methods of synthesis previously known 
have been applied to this problem, — and synthetic rubber has not yet 
made a place for itself. New methods of synthesis or polymerization, 
or changed economic values with respect to raw materials for synthe- 
sis, or cost of plantation rubber, may affect the situation in ways 
which none can now foresee. 



POLYMERIZATION OF HYDROCARBONS 



231 



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il 


S 

3 


1 




pq 


^ 



g 



t.5 






o 




c» 


II 




g 


g 

1 




II 
O 


n 




1 


o 




o 


II 




IL 


M 


ri 


w 


o - 


- O 


o 

0) 


<u 




1 a 


1 




ethyl 
tadie 






J i 


•S* 





-o 
-o 



^ 



OS i-H 



si 



IM 



;o 



I 



•-a 

J3 



a ss 



05 



:2 "-^ v." a si 

!>• 00 Oi O i-H N 



Si 

t-H 
CO 



Tit 

00 
00 






"3 
t^ , 

CO OJ 

. o 

ii 

"^ X 
~ 3 
<U 03 

^ a 

■3"C 
o 






p 9 -^ 
ill S rt 



232 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



U5 N i-i 



Q^ 



o 






U 


00 




(U 


R 






■B 


«-< 


(V 




a 

o 


N 


IS 


^ 


.9 


V 


(U 


-y 


<i) 


-n 


T3 


-d 


1 


a 


a 


■i 


o 


o 




o 










n 


^ 




J3 


<a 


sa 


"S 


PJ 





TH 


O 


M 


•3 


W 


i-i 




o 


fV 


s 


p, 


S 


;f 


II 


oT 


< 


o >^ 


3 


! 


OS 


" 


y 


Ti.a 


T1 


CO 


s ^ 


n 




o ^ 


03 


a 


oN 


^H 


g 


>.>. 


o 


•{5 


J3J3 



o 



So 





lO 


s 


7—1 
IN 













^ 


CO 


f«. 


m 
















lO 


^ • 


s 


^ 


■* 



?s 






th o w e5 |tii 



o o o o o 

|->i<o|Ttio|o 



.c 

^ 






OIt1< 



eo«3 

OJOS 



©« 



»^§ 
mam 






"S 



o 


o 


O 


1 

d 


o 




o 




g3 




K 


Sv 


1 

o 




1 




o'P^ 


s 






ss 



J^ 


CO 


■* 


CO 


!9 


■* 




us 


o : 




















r* 


t- 


t~ : 


t-; 






o 


o 


o 


O 


o 


o 



O CO CO 

CD CO ^ 

t* P- t^ 

d d o 



s 






CO 


LQ 

rH 

1—1 


? 




o' 


o 




O 


o 


O 





5 


1-H 


53 


■^ 

pH 


i-H 


^ 


^ 



I I 

o o 

•>* CO 

•* to 



o 



<o 

V 



CO 

CO 

o 



^0 

'I) 
■ s 

So 



s 



■3 

03 

X 

w 



a 

(U 
Pi 



>» 

^ 



w. 



w 






03 



CO < 



3 



a. 



1^ 
•■3 

si 



lU 



a 

1 



lU 



•3 

03 






■■B 

03 



g § 

^ .2 



<? <3 



§ 
■3 

o3 



<1 

1 


1 


"<3 


1 


1 




1 


1 


a 


1 


^ 




a 


J 


1 


'i 


3 


^ 


S 




1^ 


«!> 


CO 


ti 


CO 


M 


CO 



oo-*:S 

05>0 3 

°la« 

•iMeo 



Chapter VII. Cyclic Non-benzenoid 
Hydrocarbons. 

General Methods of Synthesis of Cyclic Non- 
benzenoid Hydrocarbons. 

Many of the well-known condensation reactions of the parafiBne 
series can take place with intramolecular condensation or ring forma- 
tion. Thus the type condensation of acetic ester to acetoacetic ester 
can take place with the diethyl esters of adipic, pimelic and suberic 
acids to form 5, 6 and 7 carbon rings, respectively, for example, 

CHjCHj . CO2C2H5 CHj — CH.., 

CH2< CH2< ">C0 

CH2CH2.CO2C2H5 CH2 — CH.CO2C2H5 

Glutaric and succinic esters do not condense in this manner to give 
cyclobutane and cyclopropane derivatives, illustrating the relative dif- 
ficulty with which ring structures of 3 or 4 carbon atoms are formed. 
The calcium salts of adipic, pimelic and suberic acids give, on heating, 
cyclopentanone, cyclohexanone and cycloheptanone respectively, but 
calcium succinate gives the cyclic diketone 

CH2 — CO — CH2 

CH2 — CO — CH2 
When the calcium salt of cyclohexane -1 . 3-dicarboxylic acid is decom- 
posed by heat the bicyclic ketone is formed which Stark ^ calls "deme- 
thylated pinone." 




_ 'Ber. iS, 2369 (1912); this keton( boilt at 157°-158°, da) 0.9322; 
melting-point 179°-180*. 

233 



semicarbazone 



234 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Ring closing incidental to Grignard's synthesis of carboxylic acids has 
been observed, as in the case of 1 . 5-dibromopentane, which with mag- 
nesium forms the dimagnesium compovind, and then on treating with 
carbon dioxide yields cyclohexanone and pimelic acid.^ 

Succinic ester and sodium condense to give a six carbon ring, suc- 
cinosuccinic ester. On hydrolyzing and heating with sulfuric acid the 
cyclic diketone is obtained which may be reduced to cyclohexane by 
converting it first into the alcohol, cyclohexanediol-1.4, then into the 
corresponding iodide and reducing this with zinc dust and acetic acid, 
exactly as in the case of aliphatic alcohols and iodides. 

K xaR H. Hi. 




"^ Cycloliexane 



The method of Wiirtz and Fittig, of treating alkyl halides with me- 
tallic sodium effecting condensation with formation of sodium halide, 
has been employed for ring formation. Freund made cyclopropane by 
treating trimethylene bromide with sodium.^ 

CH,Br CH, 

CH, < + Na, >CIL,<\ + 2NaBr . 

CH,Br CH, 



Methyl cyclobutane was prepared by Perkin, Jr., in a similar way 
from 1.4 dibromopentane.^ 



CH3 — CHBr.CH, 
CH, — CH,Br 



+ Na, 



CH,- 
CH,- 



CH — CH3 

■CH, 



" Grignard & Vlgnon, Compt. rend, m, 1358 (1907). 

'Monatsh s, 625 (1882). The original material for this synthesis trimethylene 
glycol is now a common commercial product, being isolated from the forerunninss in 
glycerine distillation. " 

*J. Chem. Soo. 5S, 201 (1888) ; 65, 599 (1894). 



CYCLIC NON-BENZENOID HYDROCARBONS 235 

and cyclohexane has been made from 1 . 6-dibromohexane and sodium. 
Condensations to carbocyclic derivatives have also been made as 
indicated by the following synthesis; the disodiimi compound of acetone 
dicarboxylic ester being treated with iodine " gives, 

COjR CO^R CO2R 003 

CHNa + I2 + NaHC CH — CH 

C0< >C0 ^C0< >C0 

CHNa + I2 + NaHC CH — CH 

CO^R COjR CO2R CO,R 

Instead of using free iodine or bromine, alkyl halides may react 
with sodium malonic ester or similar sodium compounds, as in the 
following syntheses carried out by W. H. Perkin, Jr.' 

CH^Br CO,R CH^ CO^R 

I +CH,< +2CH30Na >| >C< 

CH,Br CO2R CH^ CO2R 

from which cyclopropane monocarboxylic acid is readily made by loss 
of CO2 from the dibasic acid. 

In the same way trimethylene bromide (1) and pentamethylene 
bromide (2) yield 

CH, 

(1) >CH2< >CH.C02H cyclobutanecarboxylic acid 

CH, 

CHj — CHj 

(2) >CHi<. >CH.C02H cyclohexanecarboxylic acid 

CHj — CH2 

The above syntheses are capable of considerable variation and exten- 
sion as the following syntheses indicate: 

(1) CH2CI CH2(C02R)2 CH2 — CH(C02R)2 

+ 4-2C2H,ONa- 



CH2CI CH2(C02R)2 


CH2 — CHCCOjR), 


CH2 — CNa(C0,R)2 CH2- 
1 +Br2^l 
CH2 — CNaCCO^R), CH2- 


-CH(C0,R)2 
-CH(C02R)2^ 


CH2 — CH.CO2H 
CH2 — CH.CO2H 







•t. Pechmann, Ber. SO, 2669 (1897). 
'Ber. 15, 2091 (1902). 



236 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

(2) 



CH3 — CNaCCOsR)^ 
CH,< +CB..J.,- 

CH, — CNaCCO^R)^ 



CH2 — CCCOjR)^ 
CH^ — CCCO^R), 



CH2 — CH.CO^H 
CH,< >CH, 

CH, — CH.CO,H 



Acetoacetic ester and ethylene bromide yield cyclopropyl methyl ke- 
tone in the following manner: 



CH,Br 



CH3 

I 
CO 



CH3 

Ao 



CH, 



CH, 



CH^Br + H^C +2C2H50Na^ | >C 



CO3 



CH, 



CO,R 



CH, 



>CH.C0.CH3 



Polymerization of unsaturated substances sometimes results in ring 
formation, as in the condensation of isoprene to dipentene and isoprene- 
rubber. 



H^C 



^ 



CH, 
I ^ 
C 



^V. 



CH 



CH, 



CH 

I 



H^C 



H,C 



CK 



^%, 



CH 



XH, 



3 CHj 



crN 



Vinylacrylic acid also polymerizes readily, in the following man- 
ner,' when heated with barium hydroxide. 



CH, = CH.CH = CH.CO2H. 
CH, = CH.CH = CH.CO,H. 



CH^.CHz^CH.CH, 



CH,.CH=CH.CH, 



The Grignard reaction has also been employed to effect ring closing 
as in the preparation of l-methyl-l-hydroxycyclopentane by Zelinsky 
and Moser.* 



'DSbner, Ber. SB, 2129 (1902). 
•Ber. S5, 2684 (1902). 



CYCLIC NON-BENZENOID HYDROCARBONS 



237 



CH, 



CH, 

I 
CH, 



\ 
C 

/ 



CH, 



C = I 



\ 



CH 

H 

CH, 



C = Mgl 

CH,. 



CH3 OMgl 

\ / 

C 



2 CHj 

CH3 OH 

\ / 

C 

/ \ 

» CH, CH„ 



>CH, 
CH, 



CH, 



CH, C 



In the same manner that acetone condenses to give mesityl oxide, 
diacetylbutane treated with sulfuric acid yields methylcyclopentene- 
methyl ketone." 



CH,< 



CH, — CH, — CO 



CH, 



CH, — CO 



CH, 



-^CH,< 



CH, 
~CH, 



C — COCH3 

II 

C — CH, 



Diacetylpentane when similarly treated yields a methylcyclohex- 
enemethyl ketone. 



CH, 



CH, 



i 



C — COCH3 

)li, C — CH, 

\ / 
CH, 

Condensation of alkyl halides with benzenoid hydrocarbons, with 

elimination of halogen acid, takes place very rapidly in the presence 

of anhydrous aluminum chloride (the Friedel-Crafts synthesis) . This 

reaction has been employed for ring closing, as, for example, phenyl- 

valeryl chloride being converted into 



CH, 



XO-CH^ 
benzo-cyclohepTanone 

■Kipping A Perkin, J. Ohem. Boo. S7, 14, 24 (1890). 



238 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Halogen acids are very readily eliminated from alkyl chlorides 
alone, when treated with aluminum chloride, as for example, chloro- 
pentanes and chlorohexanes, but the nature of the resulting products 
has apparently never been investigated. 

Condensation of the aldehyde citronellal to isopulegol, through the 
action of acetic anhydride, is not typical but illustrates the tendency, 
so frequently observed, to form rings of six carbon atoms. 
CH, CH, 



H 



L ' i: 

/ \ / \ 

HgC CHj HjC CH2 

I i ^ I i H 

H^C CHO H^C C< 

\ \ / OH 

CH C 



C 



& 



Hg CHg CH3 CX 

citronellal isopulegol 



Methylheptenone is condensed by dehydrating agents to a mixture 
of m-xylene and 1 . 3-dimethyl-A'-cyclohexene. The initial reaction 
product apparently is 1.3-dimethyl-A^-^-cyclohexadiene, which it will 
be noted has the same arrangement of the double bonds as in a-ter- 
pinene and the ease with which terpinene is converted to cymene is 
well known. Apparently this cyclohexadiene derivative undergoes 
auto-reduction to give about equal parts of m-xylene and 1.3-di- 
methyl-A'-cyclohexene.^° 



CHg 

/ H, 



H,C CH 

I I > 

HjC C — CHo 

\ / 
C 
H 

The condensation of pseudo-ionone to a and P-ionone by means of 
sulfuric acid is supposed to take place through the addition and subse- 

"WaUach, Ann. S95, 74 (1918). 



i 

/ \ 

H,C CH 

H^C C — 
\ / 

c 

H 




CH 



CYCLIC NON-BENZENOID HYDROCARBONS 239 

quent loss of water. The discovery of this reaction (and the formation 
of pseudo-ionone from citral and acetone by the action of barium hy- 
drate or other alkalies) by Tiemann and Kruger/^ in 1882 marked the 
beginning of the industrial manufacture of this now well-known "syn- 
thetic violet" perfume. The two ionones are cyclohexane derivatives 
(see p. 201). 

Pinacone condensation may take place intramolecularly to form 
carbocyclic structures, as for example, the formation of 1 . 2-dimethyl- 
1 . 2-dihydroxycycloheptane from diacetylpentane." 

CH^ — CH^ — COCH3 CH^ — CH2 — COH.CH3 

CH,< >CH2< I 

CH2 — CH^ — COCH3 CH2 — CH, — COH.CH3 

A special synthesis, that of cyclopropane derivatives, has been ef- 
fected by means of diazomethane or diazoacetic ester by Buchner and 
Curtius.^* Thus fumaric ester and diazomethane yield cyclopropane- 
dicarboxylic ester. 

CHj CH.CO^R CH^ CH.CO2R CH.CO2R 



N = N CH.CO^R N C: 



^H.CO^R CH.COjR 

\ / 

N 

Cyclopentanone has been made by applying the method of con- 
densing nitriles in the presence of sodium ethylate, a reaction discov- 
ered by Thorpe." Thus 1.4-dicyano-valeric ester condenses to the 
imino compound. 

CH, — CH^CN 
CH, — CH-CN 



i 



0,R 



CH,- 


-CHj.CN 




\ 




C = NH 




/ 


CH,- 


-CH 




CO,R 



On hydrolyzing by means of sulfuric acid and heating the resulting 
acids the imino group is replaced by oxygen and two molecules of CO^ 
are removed, resulting in cyclopentanone. 



"Ber. n, 808 (1898). 

"Kipping & Perkin, J. Ohem. Soc. S9, 214 '1891). 

"Ber. IS, 237 (1885). 

"J. Cliem. Soc. 85, 1726 (1904) ; U, 578, 1004 (1907). 



240 CHEMISTRY OF THE NON-BBNZENOlD HYDBOCABBONB 



CH^ — CH- 
\ 



■CO,H 



C = NH 



CHj — CH2 
\ 



CH, 



CH 
CO,H 



CH, 



CH, 



CO + 2 CO2 



+ NH3 



It has been shown by Thorpe ^= that ring closing to form rings of 
five carbon atoms takes place very rapidly and with approximately 
equal ease in both the following cases, 



XH^CN 



XH,CN 




C=NH 



CH, — CH,CN 



i: 



H, — CH^CN 



CH-CN 



CH, — CH2 

\c = NH 



H, 



CH — CN 



Kon and Stevenson also find " that ring closing by elimination of wa- 
ter from the COOH group takes place readily forming products of the 
following type. 

^' R 

^\CHXQH 




There is no indication of the valency direction being different in 
any of these examples of ring closing. 

An instance of the ease with which substances containing a five- 
carbon ring are formed is the condensation of sym.-dipropionylethane 
to l-methyl-5-ethyl-A^-cyclopentene-2-one by the action of 10 per cent 
aqueous caustic potash.^' 

»J. Chem. Soc. 9S, 165 (1908) ; 95, 1901 (1909). 
>•/. Chem. Soc. 119, 87 (1921). 
"Blaise, Oompt. rend. 158. 708 (1914). 



CYCLIC NON-BENZENOID HYDROCARBONS 



241 



CH,CH,CO mC — CH, 



\ 



/ 



CO 



CHo — CHo 



CH3CH2C =^ C — CH3 

\ 

CO 

/ 

CH, — CH„ 



Acetonylacetone and acetonylacetophenone are unchanged under these 
conditions. 

Kishner^' has discovered that when hydrazine reacts upon un- 
saturated ketones containing the group — CH = CH . CO-pyrazoline 
bases are formed in many instances, which are readily decomposed to 
give cyclopropane derivatives. Thus pulegone yields carane: 




In a similar manner, isobutylidene acetone yields l-methyl-2-iso- 
propyl-cyclopropane, 

Pr Pr 



CH3 
CH, 



>CH.CH = CH.COCH3 -^ HN< . 



CH — CHj HC — CHj 



==i- 



CH, 



CH.CH, 



Cinnamic aldehyde yields phenylcyclopropane and phorone yields 
a dimethylisobutenylcyclopropane. This synthesis, discovered by Kish- 
ner, is another example, illustrating the remarkable reactivity of the 
group — CH = CH — CO — . 

As noted above cyclopropane derivatives are formed by the reac- 
tion of diazoacetic ester and olefine bonds, a reaction employed by 
Buchner to throw light on the constitution of camphene.^' 



".7. JJUS8. Phys.-Chem. Soc. i5, 987 (1913) ; J. Chem. Soo. Ala. 1913, I, 1163, 1165. 
"Ber. i6. 759 (1913). 



242 CHEMISTRY OF THE NON-BEN ZENOID HYDROCARBONS 




■N^CHCqR 



^=CH, 




CH-COjR 



The formation of a seven carbon ring from a cyclohexane derivative 
has been noted in the reaction of mesitylene and diazoacetic ester, the 
intermediate product being smoothly decomposed in the presence of 
copper powder at 105°. This is another illustration of- rearrangement 
which undoubtedly takes place through the intermediate formation of 
a cyclopropane derivative.^" 



CH, — C 



CH — C — CH, 



mesitylene 

+ 
diazoacetic ester 



CH = C 



\ 



y 

CH 



CH.CO,C,H, 



H„ 



CH, — C==CH- 



CH=C 



CH- 
\ 



CH, 



/ 
CH 



C.CO,C,H, 



i 



H, 



The formation of cyclic non-benzenoid hydrocarbons by hydrogena- 
tion of aromatic hydrocarbons is a useful method for the preparation 
of a limited number of substances and these could very properly be 
given the appellation hydroaromatic compounds. The hydrogenation 
of benzene at 180°-200° over finely divided nickel was first carried out 
in 1901 by Sabatier and Senderens,^^ and cyclohexane made in this way 
has been employed to some extent as a motor fuel for aeroplanes.^^ On 
hydrogenating naphthalene, tetrahydronaphthalene is the principal 
product at 180°-200°, but at 250° and 120° atmospheres pressure deca- 
hydronaphthalene is formed. Tetrahydronaphthalene has recently 
become an industrial product, being recommended as a solvent or tur- 

=»Buchner, Ber. 6S, 865 (1920). 
'^ Compt. rend. 132, 210 (1901). 
''Of. Brit. Pat. 133,288; 133,667 (1919). 



CYCLIC NON-BENZENOID HYDROCARBONS 243 

pentine substitute.^^ The xylenes readily yield the corresponding di- 
methylcyclohexane, p-cymene is converted into para-menthane, and 
meta-menthane is easily obtained by the catalytic hydrogenation of 
sylvestrene.^* Indene at 250° and under pressure may be hydrogenated 
to octahydrindene or bicyclononane.^° 

CH, — CH^ — CH — CH^ 

\ 

CH, 

CH^ — CH, — CH — CH^ 

Dibenzyl ketone, made from phenylacetic acid, yields dicyclohexyl- 
propane on hydrogenation by catalytic nickel and hydrogen. 

Cyclic Non-benzenoid Hydrocarbons, 

As pointed out in the preface, it is difficult to classify the non- 
benzenoid hydrocarbons in a way which will not unduly emphasize 
slight differences in chemical behavior or structure. As regards chemi- 
cal behavior we should certainly consider cyclopentane with normal 
pentane and cyclohexane with normal hexane. Also, the amount of 
information dealing with the derivatives of cyclohexane exceeds the 
sum total of that dealing with all the other cyclic non-benzenoid hydro- 
carbons. The reasons for this are the long standing interest in the 
chemistry of benzene, the conversion of benzene and a few of its de- 
rivatives to cyclohexane derivatives by hydrogenation, and the avail- 
ability of material for investigation, as in the case of the terpenes. 
Practically all of the other cyclic non-benzenoid hydrocarbons have 
been obtained only by synthesis, only a very few of the simplest of 
such hydrocarbons having been isolated from petroleum. Although the 
quantity of information regarding cyclohexane is so relatively large, 
the use of the term "hydroaromatic" for the cyclohexane series is very 
unfortunate and will be avoided in the following pages as much as 
possible. 

Some writers may consider that cyclopropane may properly be con- 
sidered togetherwith ethylene and its derivatives but the so-called un- 

" Cf. Tetralin and Similar Hydrogenated Products, — Frydlender, Bev. prod. ohim. 
is, 719 (1920). 

"Sabatier & Marat, Compt. rend. 156, 184 (1913). 

"Ipatlev, J. Chem. Soc. AT>s. WIS, I, 1165 ; Osterberg & Kendall, J. Am. Chem. Soo. 
ii, 2616 (1920), recommend Ipatlev's method for the preparation of cyclohexane from 
benzene. The method consists simply In placing the benzene and catalyst In a tight 
bomb, heating to 250° and passing in hydrogen at 1800 lbs. pressure from a pressure 
ey Under. 



244 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

saturation of cyclobutane places it close to cyclopropane and in a pq- 
sition intermediate between cyclopentane and cyclopropane. How- 
ever, some concession must be made to the necessity of some sort of 
orderly arrangement of subject matter and the writer has elected to 
discuss the cyclic non-benzoid hydrocarbons in a series beginning with 
cyclopropane. 

There are two general classes of information regarding the cyclo- 
parafSnes and particularly the cyclohexane series. On the one hand 
there is a relatively large amount of information obtained by the in- 
vestigation of pure substances, either synthesized or isolated from a 
natural product as is usually the case in the study of the terpenes ; this 
information is usually accurate and satisfactory, from a scientific 
point of view. The second type of information is much less definite 
and less reliable and has to do with very imperfectly known mixtures 
such as petroleum distillates, shale oils, rosin oils, and similar products 
whose literature is nevertheless considerable by reason of their com- 
mercial importance. In dealing with the chemistry of these substances 
the scientific and industrial works have usually been rigidly exclusive, 
each of the other class of information. However, the proportion of 
information of permanent, scientific value contributed by the indus- 
tries is becoming greater than ever before and cannot be passed by, 
and in the following pages information from industrial sources will be 
included whenever it is of interest and appears to be of permanent 
scientific value. 

Cyclopropanes: Simple cyclopropane hydrocarbons have not been 
found in nature but the bicyclic terpenes. sabinene and carene possess 
three carbon rings, as does also the ketone thujone. The similarity 
of the cyclopropane ring to the ethylene bond has repeatedly been 
pointed out. Its influence upon physical properties is less marked 
than in the case of the double bond, as has been reviewed in the sec- 
tion on physical properties. Carr and Burt ^^ conclude, from a study 
of absorption spectra, that the cyclopropane ring is a "center of resid- 
ual afiinity" similar in character but intermediate in quantity to that 
of the double bond, and as such can form a conjugated system with 
the carbonyl group. The relative stability of the derivatives of cyclo- 
propane varies within wide limits, with different substituent groups, 
as will be brought out in the following pages. 

Kohler and his students have shown, in a series of papers, that sub- 
stituents have exactly the same effect upon the mode of addition to a 

"J. Am. Chem. Soc. 40, 1590 (1918). 



CYCLIC NON-BENZENOID HYDROCARBONS 245 

cyclopropane ring as to an ethylene linkage, even though the saturated 
open-chained compounds formed in the two cases are quite different in 
structure.^^ Thus, as pointed out by Kohler and Conant, the mode of 
addition of hydrobromic acid to cyclopropane hydrocarbons is deter- 
mined by the number and arrangement of the alkyl groups. The ring 
invariably opens between the carbon atoms that hold the largest and 
the smallest number of alkyl groups and the principal product is al- 
ways one in which the halogen is combined with the carbon atom that 
holds the largest number of alkyl groups. In the case of cyclopropane 
carboxylic acids the COjH groups may affect the ease with which addi- 
tion takes place, but the product is always either a y-bromo acid or 
the corresponding lactone. The few ketones that have been studied 
behave like the acids. In cases where a carbonyl group is next to the 
ring the halogen atom accordingly always goes to the p-position in the 
ring, for example, 

CH, 

I >CH.CO,H + HBr ^CH^Br.CH.CH^.CO^H 

CH, 

CH^ 

I > CH . CO . CeH, + HBr > CH.Br . CHXH^COCeH, 

CH3 

Kohler and his assistants find that derivatives of the type 

CeH.CH — CH.COCeH, 

\ / 

C(CO,R), 

are quite stable to cold permanganate solution and to ozone but are 
hydrolyzed by water with "unusual rapidity," and, in the absence of 
water, alcoholates, ammonia and amines rapidly convert them into 
isomeric unsaturated compounds. 

The cyclopropane ring may be broken in different ways depending 
upon the conditions and the reaction employed. The phenylanisoyl 
derivative studied by Miss Hahn^^ breaks down in the three ways 
indicated below, 

(1) With alkali alcoholates 

CeH.CH — CH . COCeH.OCH, 

\ . / > CeH.CH = C — C0C„H,0CH3 



C(C0,CH3), I 



HCCO^CH,), 



"Cf. Kohler & Conant, J. Am. Chem. Soe. S9, 1404 (1917). 
"J. Am. Chem. fioc. SB, 1J20 (lUltSi. 



246 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

(2) When the dibasic acid is heated COj is evolved accompanied by 
rupture of the ring, 

RCH — CH . COCeH.OCH, 

\ : / > RCH = C . CH.COCeH.OCHj 

C(CO,H), I 

CO,H 

(3) When the ester in solution in acetic acid is reduced with zinc dust 
the reduced derivate is obtained 

RCH — CH . COCeH.COCHj 

\ / ^RCH.CH^COCeH.OCH^ 

C(CO,CH3)3 I 

CH(C0,CH3), 

A series of cyclopropane derivatives has been made by Bruylants ^' 
starting with the novel reaction, 

CH,Br CH^Br 

CH3< +2C2H5MgBr— ^CH2< > 

CH.CN CH,C — C,H» 



CH,/ 



CH, 



N.MgBr 
CH, 



^CH,<| 
CH — C — CjHg CH — C — CoH. 

II II 

NMgBr 

Halogen derivatives of the type CH, CHj 

I >CHC< 

CH, I CHg 

are quite stable to boiling aqueous caustic alkali but boiling with alco- 
holic alkali gives a mixture of the ether and the unsaturated hydro- 
carbon. When the unsaturated hydrocarbon is treated with bromine a 
tribromide is formed, the double bond taking up Br, and the tertiary 
hydrogen atom being replaced without rupture of the cyclopropane 
ring, 

CH, CH, CH, CH,Br 



CH — C +2Br, 



\ / 

C — C.Br 

/.I \ 



CH, CH3 CH, I CH3 

Br 

"Reo. trav. cUm. tS, 180 (1909). 



CYCLIC NON-BENZENOID HYDROCARBONS 247 

Kohler has made a number of nitro derivatives of cyclopropane by re- 
acting upon unsaturated substances with nitromethane, brominating 
and removing HBr, for example,'" 

CeH.CH = CH . COC (CH3) 3 + CH3NO, ^CeH.CH— CH.COC (CH3) 3 

CH2NO2 



■^CeH.CH — CHBr.COC(CH3)3 + CHjCO^K 



2^ 

— > 



CH.NO, 



CeH.CH — CH . COC (CH3) 3 
CH.NO2 

Cyclopropane is reduced to propane by hydrogen and catalytic 
nickel slowly at 80° and rapidly at 120°, but cyclobutane requires a 
temperature of approximately 180° for hydrogenation to butane.^^ 
Cyclopropane thus occupies a position intermediate in stability, to 
hydrogen and nickel, between cyclobutane and ethylene, the latter 
being reduced to ethane at temperatures as low as — 15°. Cyclo- 
propane is readily reduced to propane by colloidal platinum in acetic 
acid but cyclopropane-1 . 1-dicarboxylic acid is not reduced under these 
conditions.'^ Ethylene is reduced a little more rapidly than cyclopro- 
pane by this method (Fokin-Willstatter method) . 

In contact with iron conversion of cyclopropane to propylene '' can 
be observed at 100°, but in the presence of platinum black the reaction 
is slow at 200°, although rapid at 315°. 

Cyclopropane can be prepared '* by the reduction of 1 . 3-dibromo- 
propane by zinc in alcohol (75 per cent) at temperatures not exceeding 
60°. It was first made by the action of sodium on this dibromide. It 
is thus evolved as a gas, easily condensed to a liquid boiling at — 35° 
(749 mm.). 

Methyl Cyclopropane,^^ boiling-point 4° to 5°, is formed when 1.3- 
dibromobutane is treated with zinc dust in alcohol, in the same manner 
in which Gustavson prepared cyclopropane from 1 .3-dibromopropane. 

1 .1-Dimethylcyclopropane,^^ boiling-point 21°, like other deriva- 

■» Kohler & Rao, J. Am. Chem. Soc. U, 1697 (1919). 
" Wnistatter & Bruce, Ber. iO, 4459 (1907). 
"Boeseken and others, Rec. trav. chim. S5, 260 (1916). 
"Ipatiev, Ber. S5, 1057 (1902) ; S6, 2014 (1903). 
"Gustavson, J. prakt. Chem. (2) 76, 512 (1907). 
"Demjanoff, Ber. 28, 22 (1895). 
"Ipatlev & Huhn, Ber. S6, 2014 (1903). 



248 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

tives of cyclopropane, reacts only very slowly with permanganate, and 
may thus be distinguished from the isomer trimethylethylene, the lat- 
ter hydrocarbon being formed when 1 . 1-dimethylcyclopropane is 
passed over alumina at 340°-345°. 

The 2 . 3-dicarboxylic acid derivative of 1 . 1-dimethylcyclopropane 
is of interest as having been produced by Baeyer and Ipatiev ^' by the 
oxidation of carone and later synthesized by W. H. Perkin, Jr., and 
Thorpe.^' It exists in two physically isomeric forms known as cis and 
irans-caronic acids. It was synthesized by treating the ester of mono- 
bromo-pp-dimethylglutaric acid with alcoholic caustic potash. 
C(CH3), 
X \ C(CH3), 

/ \ KOH / \ 

C^HAC.CHBr CH^.COAHs > KO,C . CH — CH . CO^K 

Hydrobromic acid at 100° breaks the ring in the following manner: 

C(CH3), 
\/ \ Br.C(CH3), 

X\ \ +HBr I 

HO^C.CH — CH.CO^H > HO,C . CH^ — CH — CO,H 

The alkali salts of cis and trans-caronic acids are quite stable to aque- 
ous permanganate. 

1 .2.-Dimethylcyclopropane has been made from 2 . 4-dibromopen- 

0° 20° 

tane by Gustavson's method. It boils at 32°-33°, d -j^ 0.7025, d-p- 

0.6806, n^ 1.3823. 

1 .2.S.-Trimethylcyclopropane was made by first synthesizing 3- 
methylpentanediol-(2.4). This was converted to the corresponding 
dibromide by heating with hydrobromic acid and the dibromide treated 
with zinc dust in 80 per cent alcohol, yielding the hydrocarbon, boiling- 

22° 22° 

point 65 °-66°, d-j3 , 0.6921, n^=-1.3942. It is quite stable to aqueous 

permanganate. 

1 .1 .2 .-Trimethylcyclopropane was made by Kishner'^ from mes- 

ityl oxide by his hydrazine method. The hydrocarbon boils at 52.8° 

20° 
d ^ 0.6949, nj) 1.3866. It is easily dissolved by nitric acid (1.52) 

and reacts with concentrated sulfuric acid giving a mixture of kero- 

" Ber. 29, 2796 (1896), 

"J. Chem. 800. 75, 48 (1899). 

"J. Ruaa. Phya.-Chem. Soc. H, 165 (191 2 1 



CYCLIC NON-BENZBNOID HYDROCARBONS 



249 



sene-like hydrocarbons boiling mostly within the range 170°-360°. 
These higher boiling hydrocarbons are probably formed by the inter- 
mediate formation of an olefine followed by polymerization in accord- 
ance with the general behavior of olefines to concentrated sulfuric acid 
which has been discussed elsewhere in these pages. With nitric acid in 
glacial acetic acid hydration occurs, resulting chiefly in isopropyl di- 
methyl carbinol. It is reduced by Sabatier's method as follows: 
CH3 CH.— CHe CH, 

\ / 

C 



CH, 



/ \ 



-> CH,CH, 



A- 



CH, 



CH, 



CH, 



Fuming hydroiodic acid and bromine break the cyclopropane ring. 

Methylisopropylcyclopropane is formed by heating methyl iso- 
propyl pyrazoline (from isobutylidene-acetone and hydrazine hydrate) 
to 230° with caustic potash.*" 

CH3 CH3 

>CH — CH.NH.N > >CH — CH 



CH, 



i 



H, 



C — CH, 



CH, 



\ 



\ 



CHj — CH , CH3 



2(1° 2f)° 

The hydrocarbon boils at 80°-81°, d^ 0.7120, n ^ 1.3927. 

1-Methyl-l .2 .-Diethylcyclopropane has been made by Kishner's 

20° 
hydrazine method. It boils at 108°-109°, d -^ 0.7382, nj-, 1.4102. It 

is markedly more stable to permanganate solution than 1.1.2.-tri- 
methylcyclopropane and is also less reactive to bromine.*^ 

Methylisobutylcydopropane was made by Zelinsky *^ by hydrogen- 
ating the dimethylbicyclohexane, shown b^low, in the presence of 
platinum or palladium black, 

CH3 
CH — CH, CH — CH^CH < 



CH, 



/ 

2 
\ 



CH — CH 



\ CH3 

y., CH3 

1 

20° 



->CH, 



/ 
\ 



CH, 



CH.CH, 



It boils at 110°-111°, d-j^ 0.7403. In the presence of nickel and hy- 
drogen the cyclopropane ring is also broken and reduced. 

"Kishner, J. Buss. PJivs.-Chem. Soc. J,S, 987 (1913). 
" Klshner, J. Rusa. Phys.-Ohem. Soc. U, 165 (1912). 
"J. Ruas. i5, 831 (1913). 



250 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



1.1. -Diinethyl-2-Isobutenylcyclopropane is formed when phorone 

20° 

is heated with hydrazine hydrate; boiling-point 132°, d-r— - 0.7677, n_ 

1.442.*' It may be oxidized to 1 . 1 . -dimethylcyclopropanecarboxylic 
acid by means of permanganate without rupture of the ring. Treat- 
ment with fuming HBr gives first the monobromide and then the di- 
bromide, 



CH3 CH — CH: 



c< 



CH3 

CHo CH, 



CH, 



■^ >C< 
CH, CH. 



CH — CH, — C< 



CH3 

CH, 



>CH.CH2CHBrCH2 — C< 

I 
Br 



2 
CH3 

CH, 



Br 



CH, 
~CH, 



A tricarboxylic acid derivative of methyl dicyclobutane has been 
prepared by Beesley and Thorpe ** and is mentioned because of its 
curious structure, its method of preparation and the fact that 
it exists in three distinct modifications, in accord with accepted 
ideas of stereochemistry. When the dibromoethyl ester of the acid 
CH3C. (CH2C02H)3 is treated with pyridine a dilactone ester is formed 
which readily yields the free acid, 



CHBr.CO^C^Hg 

/ 
CH3C — CHBr . CO2C2H, 

\ 

CH,CO„C,Hk 



/ 



CH.CO,H. 



-^CH3 — C — C.CO^H. 



-^H.CO^H. 

Three distinct modifications melting at 193°, 165° and 154° were iso- 
lated, which evidently correspond to the three theoretically possible 
acids, 



CH3 

i 



CH, 



i 



/ 



/ 



/ 



/ 



\ 



\ 



\ 



\ 



c c c 

/\ I /\ 

/ \ CO,H / \ 

H . CO^H. CO,H H 



/ 



/ 



/ 



./ 



\ 



\ 



\ 



/ \ 

CO,H H 

"Klshner, J. Russ. Phys.-Chem. Soc. 1,5, 957 (1913). 
"J. Chem. 800. m, 601 (1920). 



■C- 



\ 



■ c 



CO,H 



H 






CO^H 



CYCLIC NON-BENZENOID HYDROCARBONS 251 

CH. 

I 
C 



/ 






\ 
\ 
\ 
\ 



c c c 

/ \ CO,H / \ 

CO^H H CO^H H 

These acids are remarkably stable and are not affected by prolonged 
boiling with aqueous acids or alkalies. 

Cyclobutane: This hydrocarbon, boiling-point 11°-12°, D^" 
0.7038, is readily made by hydrogenating cyclobutene in the presence 
of nickel at 100°. Hydrogen in the presence of nickel, at 180°, con- 
verts cyclobutane to normal butane. It is stable at ordinary tempera- 
tures to bromine and hydriodic acid. Its simple derivatives show a 
striking resemblance in physical and chemical properties to the deriva- 

CH, — CHOH 
tives of n. butane. Thus cyclobutanol I I and n. butyl 

CHj — CHj 
alcohol are very similar in odor and boiling-point, 123° and 116.8° re- 
spectively. W. H. Perkin, Jr.,*^ who prepared cyclobutanol, stated, "It 
shows the closest resemblance to the fatty alcohols containing the same 
number of carbon atoms ; it might, indeed, be readily mistaken for nor- 
mal butyl alcohol." Perkin also found that cyclobutylcarboxylic acid 
behaves very much like valeric acid, the amide giving excellent yields 
of the amine, with bromine and caustic potash. 

CH^ — CH . CONH, CH^ — CHNH^ 

CH2 — CH2 CHj — CHj 

The cyclobutane derivatives all have slightly higher boiling-points 
than the corresponding normal butane derivatives. 



6° 

7" 
8° 
40 

7* 



Cyclobutyl Series 


Normal Butyl 


Substance B.-P. 


Substance B.-P 


R.CO,H 195° 


R,CO.H 186° 


R.NH, 81° 


RiNH, 76° 


R.OH 123° 


RiOH 116° 


R.Cl 85° 


R>C1 77° 


RBr 104° 


RiBr 100° 


RI 138° 


I^I 131° 



'J. Chem. Soo. 65, 950 (1894). 



2S2 CHEMISTRY OF THE NON-BENZENOlD HYDROCARBONS 

Willstatter *^ and his co-workers have applied the well-known method 
of exhaustive methylation and decomposition of the tertiary base, to 
the preparation of cyclobutene. 

CH3 

CH, CH — NH, CH, CH — N — CH, 



l\ 
OH CH, 



CH, — CH 

+ N(CH3)3 + H,0 



i: 



R, — CH 

Cyclobutene readily adds one molecule of bromine to form the com- 
paratively stable dibromide boiling-point 171°-174°. When heated 
with quinoline this dibromide decomposes with rupture of the ring, giv- 
ing butadiene but with caustic potash at 200° acetylene is formed.*^ 

[CH = CH n HC = CH 

I I ^ + 

CH = CH J HC = CH 

I' L \ 

CH, — CHBr \ + quinoline > CH^ = CH ^ CH = CH^ 

The following methods of rupturing the ring of cyclobutane or its 
simple derivatives have been observed. 

(1) CH, — CH^ 

I I > H3 + Ni at 180° > CHaCH.CH^CH, 

CHj — CHj 

(2) CH2 — CHCO^.iCa + CaCOH), 

CH, — CH, > 2CH3 = CH, + CaCOs . + H,0 

heat 

(3) 1 . 2-dibromocyclobutane + quinoline > butadiene. 

(4) Cyclobutylamine phosphate 4- heat > butadiene. 

(5) 1. 2-dibromocyclobutane + KOH > acetylene. 

Gustavson *' prepared a hydrocarbon C5H5 by the action of zinc in 
alcohol on CCCHaBr)^ and from the manner of its formation and its 
physical properties and chemical behavior Gustavson's hydrocarbon 
has been considered to be spirocyclane, 

"Ber. 38, 1992 (1905) ; iO, 3979 (1907). 

" The 1.3-diphenyl derlvatiTe of cyclobutadiene is a stable crystalline hydrocarbon 
melting at 130°. [Gastaldi & Cherchi. Gaaz. cMm. Ital. U (1), 282.] 
"J. prakt. Chem. (2) 5i, 105 (1896) ; 56, 93 (1897). 



CYCLIC NON-BENZENOID HYDROCARBONS 



253 



BrCH, CH^Br 

\ / 

C 

/ \ 

BrCH, CH3r 



CH, CH, 


\ / 




C 




/ \ 




CHj CH2 



However, it has been shown that by careful fractional distillation Gus- 
tavson's product may be separated into two hydrocarbons, one boiling 
at 37.5° and the other at 42°. Philipow *" has demonstrated that both 
hydrocarbons are derivatives of cyclobutane, the lower boiling one 
yielding levulinic acid on oxidation, 



CHj — C — CH, 



CH, 



.i 



CH,-C< 



CH, 



CH, — CO — CH, 



H 



Ch, 



OH 
CH.OH. 



CH, — CO„H 



methylcyclobutene 



The hydrocarbon boiling at 42° proved to be methenecyclobutane. 
Both hydrocarbons yield the same hydroiodide and treatment of this 
iodide with moist silver oxide yields an alcohol boiling at 116°-119°. 
The same alcohol is obtained directly from both hydrocarbons by 
careful hydration by dilute sulfuric acid. 



CHj — C — CHa 



+ HI 



CH, 



C< 



CH, 



CH, — CH 
CH, — C = 



CH2 — CH2 



^ CH,- 



H, 



CH2 \ /» 

X 



\ 



\ 



CH, 



CH2-C< 



OH. 



dil. H,SO, 



CH, — CH, 



Previous results on the oxidation of the hydrocarbon boiling at 42° and 
the alcohol had led to no very definite results, but Philipow showed 
that the oxidation of the alcohol is strictly analogous to the oxidation 
of 1 -methy ley clohexanol ( 1 ) , 



"■/. pmkt. Chem. (2) 9S, 162 (1916). 



254 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

CH2CO2H principal 

/ CH2CO2H reaction 

CH3/ 






0H\ 

\ 

HCO2H -|- cyclohexanone. 



CH3 

CH2 — C< CO2H CO^H principal 

I I OH. /> CH3C0,H + CH3< >| 

I I / CO,H CO2H reaction 

CH2 — CHg \ 

\ HCO^H + CH2 — CO CH2 — CO^H 

I > 1 



i 



H2 — CHj CHj - — COgH 

Hydrogenation had yielded a hydrocarbon C5H10, supposed, on the 
basis of the spirocyclane structure, to be ethylcyclopropane. Philipow 
made ethylcyclopropane ^" by Kishner's admirable method, from 
acetylcyclopropane, 

'>CH.CO.CH3 + H2N.NH2^| >CH.CH,CH3 + Nj + H,0 
H„ CHo 



A 



Perkin and Colman^'^ had stated that methylcyclobutane was pro- 
duced by the action of sodium, in toluene, on 1.4-dibromopentane but 
on repeating their work Philipow obtained a similar product but showed 
that it was a mixture of hydrocarbons, in which he identified piperylene 
and n.pentene. Demjanow ^'^ had made methylcyclobutane by the ac- 
tion of zinc in acetic acid on cyclobutylmethyl iodide. Philipow made 
this hydrocarbon in two ways, from cyclobutylaldehyde CiH^.CHO 
by Kishner's method, and also by reduction of Gustavson's hydrocar- 
bons by colloidal palladium (Skita's method), and the hydrocarbon 
obtained by the three methods proves to be identical, i. e., methyl- 
cyclobutane, boiling-point 36°-36.5° (755mm.),d^5 0.7118, MR 23.58, 

MR calc. 23.02. Methylcyclobutane reacts with hydrogen in the pres- 
ence of catalytic nickel at 205° to give isopentane. 

"Phillpow's ethylcyclopropane boils at 36.5° (755mm.), d 4° 0.7055, MR 23.61, 
MR calculated 23.02. 

»> J. Chem. Soc. 5S, 201 (1888). 

« J. Buss. Phpe.-Chem. Soc. i2, 842 (1910). 



CYCLIC NON-BENZENOID HYDROCARBONS 255 

18° 
Cyclobutanone, boiling-point 99°-10P, il-y^ 0.9344, has an odor 

lo 

resembling acetone. Oxidation by nitric acid yields succinic acid. It 
was made by Kishner from cyclobutanecarboxylic acid by treating 
with ammonia to form the amide, brominating and then treating with 
bromine and caustic potash, 

/ \ / \ 

CH^ CH.CO.H >CH2 CHCONH, > 

\ / \ / 

CHj CH2 

/ \ / \ 

CH2 C — CONH2 CH^ CO 

\ /I -^ \ / 

CH2 Br CHj 

Cyclobutene is of interest on account of the series of bromine 
substitution products which can be prepared from it without rup- 
ture of the ring. Thus cyclobutene adds a molecule of bromine to 
form 1 . 2-dibromocyclobutane. On treating this with alkali one mole- 
cule of hydrogen bromide is removed and the resulting bromocy- 
clobutene, like aliphatic olefines containing halogen, is relatively 
quite stable. It adds HBr to form 1 . 1-dibromocyclobutane which 
on hydrolyzing with aqueous lead oxide yields cyclobutanone. 
Bromocyclobutene adds bromine to form 1 . 1 . 2-tribromocyclobutane, 
which can be converted to CHj — CBr by loss of HBr, and this in 

H, — CBr 

turn adds bron:iine to give CHj — CBt^ melting-point 126° and this 

- '^^^ 
can be further brominated without breaking the ring to form penta- 

bromocyclobutane, and hexabromocyclobutane melting at 186.5°.^° 

Ethylcyclobutane has been prepared by a very roundabout method 

from the amide of cyclobutanecarboxylic acid, which was converted 

into cyclobutylmethyl ketone, this reduced to cyclobutylmethylcar- 

binol and the latter converted to the corresponding iodide and reduced 

by zinc dust and acetic acid.^* The hydrocarbon boils at 72.2°-72.5°, 

"Wnistatter & Bruce, Ber. m, 3979 (1908). 
"Zelinsky & Gutt, Ber. Si, 2432 (1908). 



CI., ^. 
CH, — CI 



256 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

10° 20° 1Q "i" 

d-^ 0.7540, d-^ 0.7450 and n^ 1.4080. Oxidation by nitric acid 

yields succinic acid. Cyclobutylmethyl ketone boils at 136°-136.5° 
(semicarbazone melting at 148°) and the cyclobutylmethylcarbinol 
CiH^.CHOH.CHs, boils at 144° (phenylurethane melting at 87.5°- 
88°). 

Lebedev ^^ has shown that when substituted allenes are polymer- 
ized, cyclobutane derivatives are formed. When unsymmetrical di- 
methyl allene is heated in sealed tubes the principal product is 1 .2-di- 
isopropylidenecydobutane CH^ — C = C (CH3) ^ together with 1 . 1- 

CHj — C ^ C (CH3) 2 
dimethyl-2-methylene-3-isopropylidenecyclobutane. The former hy- 

20° 1Q 7° 

drocarbon boils at 179°-181°, d-^ 0.8422, n ^^- 1.5008 from which 

the increment of the molecular refraction is shown to be 2.32. It is 

readily hydrogenated to 1.2-diisopropyl-cyclobutane, boiling at 157°- 

0° 
158.5°, d —3. 0.7901. The monoozonide yields isopropylidene-2-cyclo- 

butanone, CHj — C = boiling-point 171°. Isopropyl-2- 

CH2 — C ^ 0(0113)2 
cyclobutanone obtained by reduction, boils at 148°-150° (semicarba- 
zone melting at 183°). 

The hydrocarbon l.l-dimethyl-^-methylene-S-isopropylidene boils 

20° 
at 149°-150°, d -j^ 0.7982. The corresponding saturated hydrocarbon 

obtained by reduction, i. e., — 1.1. 2-tTimeth.y\-d-isopropylcyclobutane, 

20° 

boils at 145°-146°, d -j^ 0.7598. The two unsaturated hydrocarbons 

have a sharp kerosene-like odor. The two saturated hydrocarbons are 
not attacked by aqueous permanganate. The stability of the satu- 
rated cyclobutanes to sulfuric acid has not been noted. 

Cyclobutane-1 .1-Dicarboxylic Acid, melting-point 155°, is pre- 
pared by a general method discovered by Perkin, i. e., — ^the reaction 
of 1 . 3-dibromopropane and sodium malonic acid ester or sodium cyan- 
acetic ester. 

CH2Br CO2R CH2 CO2H 

0H2< +2Na + H20< »0H,< >C< 

CH2Br ON OH2 OOjH 

Decomposition of the dicarboxylic acid yields, 

"J. Ruas. Phys.-Chem. Soc. 1,3, 820 (1911). 



CYCLIC NON-BENZENOID HYDROCARBONS 257 

Cyclobutanecarboxylic Acid, boiling-point 194°. The acids of this 
type resemble fatty acids very closely, this acid readily yielding a 
pleasant smelling ethyl ester boiling at 160°, an anhydride boiling at 
160°, an amide melting at 130° and a nitrile boiling at 150°. Hydri- 
odic acid at 200° breaks the ring forming n . valeric acid.^' When the 
silver salt is treated with iodine, a peculiar condensation with forma- 
tion of the ester of cyclobutanol results," 

2C,H,C0,Ag + I, > C,H,CO, . C,H, + CO, + 2AgT 

Cyclohutane 1.1 .2.2.-Tetracarhoxylic Acid, melting-point 145°- 
150° is formed by the reaction 

CO,R 
CH,— C< 

CO^R 

CO^R 
CH,-C< 

CO^R 

On heating, the free acid it loses two molecules of carbon dioxide and 
forms cyclohutane-l-2-dicarhoxylic acid, melting at 137°, known in cis 
and trans forms. On brominating the 1 . 2-dibromide is formed. By 
the action of caustic alkalies one molecule of HBr is removed to form 
the bromocyclobutene carboxylic acid, 

CH^ — CBr — CO^H . CH^ — CBr 

KOH I II +C02 + HBr 



CH,- 


CO,R 

-CNa< 

CO^R 

CO^R 

-CNa< 

CO,R 


Br, 


CH,- 


or I, 



— CBr — 



CH, — CBr — CO,H . CH, — C . CO,H 

Silver oxide in water replaces both bromine atoms with hydroxyl, these 
reactions being quite analogous to the formation of bromofumaric acid 
and tartaric acid from isodibromosuccinic acid under the same condi- 
tions, 

CHBr . CO,H . CH — CO,H CH (OH) . CO,H 



CBr— 



and I 



CHBr.CO,H CBr— CO^H CH(OH).CO,H. 

Cyclohutane -1 . S-Dicarboxylic Acid is known in cis and trans 
forms, melting at 136° and 171°, respectively. Simonsen^^ has shown 
that when the ethyl ester of Prmethoxymethylmalonic acid is digested 

"Klsliner, J. Russ. Phys.-Ohem. 8oc. iO, 673 (1908). 
"Demjanov, J. Ruse. Phya.-Chem. Soc. iS, 835 (1911). 
"J. Chem. Boo. SS, 1778 (1908). 



258 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

with hydrochloric acid it yields cis-cyclobutane-1 . 3-dicarboxylic acid. 

The cyclobutane ring exists in a-truxillic acid, which, according 
to De Jong,^^ is 1 . 3-diphenyl-cyclobutane-2 . 4-dicarboxylic acid. It is 
formed from cinnamic acid by the action of light and on heating breaks 
up again into cinnamic acid. 

Cyclopentane: The relationship between cyclopentane and cyclo- 
hexane, or their derivatives, is exceedingly close, and the increasing 
number of instances known, in which change of the one ring system 
into the other occurs, makes evident the rationality and convenience 
of considering these two ring systems together, rather than isolating 
the cyclohexane derivatives as "hydroaromatic" compounds, as has 
usually been done heretofore and thus widely separating the subject 
matter dealing with these two ring systems. Examples of the con- 
version of these two ring systems, one into the other, have been noted 
in the section on Rearrangements. Thus one of the smoothest reactions 
of this kind is the nearly quantitative conversion of 1-methyl-l-a-hy- 
droxyethylcyclopentane to 1.2-dimethyl-A^-cyclohexene by zinc chlo- 
ride.°" Cyclopentane is also formed when the bromide of cyclobutyl- 
carbinol is reduced by the zinc-palladium couple and hydrobromic 
acid.®^ Kishner showed that when benzene is reduced under high pres- 
sure at 280°, according to Wreden, that the product is not cyclohexane 
but methylcyclopentane *^ and Markownikow ^^ has shown several in- 
stances in which benzene hydrocarbons give cyclopentane derivatives 
on hydrogenation. Cyclohexanol yields chiefly methylcyclopentane on 
heating with concentrated hydriodic acid. The hydrocarbons them- 
selves are quite stable; only in reactions of their derivatives does re- 
arrangement of the ring structure occur easily. Thus Markownikow 
and Fortey °* independently observed that cyclohexane could be heated 
with hydriodic acid (and red phosphorus) in sealed tubes to 240° with- 
out change. Methylcyclohexane is, however, partially rearranged by 
heating with hydriodic acid to 270° to dimethylcyclopentane, and this 
change is effected without the formation of higher boiling products, in 
other words, is not a thoroughgoing decomposition such as occurs in 
"cracking" processes. Methylcyclopentane is one of the products of 
the action of aluminum chloride on cyclohexane.^^ 

" Chem. Aba. 1918, 1385; Stoermer & Laage, Ber. 5i, 77 (1921). 

•"Meerweln, Ann. il7, 255 (1918). 

•'Demjanow, Ber. 1,0, 4960 (190T). 

'^J. Ruse. Phys.-Chem. 8oc. 29, 2i0 (1897). 

"Ber. SO, 1214 (1897). 

" Proc. Ohem. Soc. 1897, 161. 

"Aschan, Ann. S2I,, 12 (1902). 



CYCLIC NON-BENZENOID HYDROCARBONS 259 

Cyclopentane was prepared by Wislicenus °* from cyclopentanone, 
the latter being prepared by the well-known method of heating calcium 
adipate. Cyclopentanone is also a constituent of the oily residues re- 
covered in the rectification of wood alcohol. The ketone on reduction 
under the same conditions usually applied to ordinary aliphatic ke- 
tones, for example, reduction by means of sodium in moist ether, yields 
cyclopentanol. The alcohol has an odor resembling amyl alcohol, boils 

21 5° 
at 139°, d "p 0.9395. Cyclopentanol is converted into the corre- 
sponding iodide by saturating with hydrogen iodide and hydrogen bro- 
mide yields the bromide, without rupture of the ring. Reduction of 
the iodide under the usual conditions, zinc and hydrochloric acid in 

20 5° 

dilute alcohol, yields cyclopentane, boiling-point 50.5°-50.7°, d "„ 

0.7506. 

Cyclopentane is inert to bromine in the dark but in sunlight sub- 
stitution with evolution of HBr occurs, approximately with the same 
ease as in the case of normal pentane. On heating with bromine in a 
sealed tube the reaction is very slow at 100° but more rapid at 128°- 
130°, the reaction then being accompanied by deposition of carbon. 

Cyclopentane has not been sulfonated, the hydrocarbon being quite 
stable to sulfuric acid. Borsche ^^ has prepared cyclopentane sulfonic 
acid by an indirect method involving the conversion of cyclopentanol 
to the bromide, reacting on the bromide with magnesium in ether and 
treating the magnesium complex CjHgMgBr with SOj and then oxidiz- 
ing with aqueous permanganate. The potassium cyclopentyl sulfonate 
was crystallized from absolute alcohol. Salts of methylcyclohexane-3- 
sulfonate were prepared in the same manner from 1 methyl-3-bromo- 
cyclohexane. 

Cyclopentene is readily formed on warming cyclopentyl iodide with 
alcoholic caustic potash, closely resembling amyl iodide and its con- 
version to amylene under the same conditions. Cyclopentene boils 
at 46°. When cyclopentyl bromide is employed a small proportion of 
cyclopentyl ethyl ether is also formed, again paralleling the n.amyl 
derivatives. From cyclopentene Meiser "^ prepared the dibromide, 
which he converted to the 1 . 2-glycol by hydrolyzing with aqueous po- 
tassium carbonate; the glycol was converted to the chlorohydrin by 

"Ann. 275, 327 (1893). 

" Ber. kO, 2220 (1907). Borsche prepared l-methyl-cyclohexane-3-sultone-chloride, 
which on reduction yields the 1-metliyl cyclohexane- thiol (3), boiling at 172°, — the 
first of the cyclic mercaptana to be synthesized. 

"Ber. Si, 2050 (1899). 



260 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

hydrochloric acid and the same product was made by the addition of 
hypochlorous acid to cyclopentene. 

In the cyclopentane series a very large number of derivatives are 
known, but the great majority of them have been synthesized by 
costly and usually very roundabout methods. The hydrocarbons them- 
selves have seldom been used for preparing derivatives; in fact, the 
hydrocarbons have been prepared from the derivatives. Cyclopentane 
or its alkyl derivatives have never been isolated in a pure state from 
petroleum or any other natural product. 

Cyclopentadiene, boiling-point 41°, may be isolated from the fore- 
runnings when crude benzene is distilled,^' and Etard and Lambert '"' 
found it among the products of the thermal decomposition of heavy 
paraflBne oil. It polymerizes spontaneously to the dimeride CjoHij on 
standing at ordinary temperatures and on distillation the dimeride is 
partially inverted to the original hydrocarbon. The dimeride (un- 
known constitution) boils at 170°. Stobbe ''^ finds that the spon- 
taneous conversion to the dimeride is complete in about 30 days and 
when exposed to oxygen or air a diperoxide of the dimeride is formed, 
which Stobbe regards as having the following structure. 



CH — CH — CH — CH 


/ 








\ 


0= 











\ 








/ 


CH CH — ( 


:H CH 


\/ 


\/ 




CH 


3 


CHj 





The dimeride is much more stable than the original hydrocarbon 
but may be further polymerized by heating to 160°-180° in a sealed 
tube, a solid resin being formed.'^ The polymers of acyclic olefines 
and dienes are also more stable than the original hydrocarbons, the 
difference being marked in their behavior to concentrated sulfuric acid, 
hydrogen chloride, hydrogen bromide, etc. Hydrogen chloride com- 
bines with cyclopentadiene to form a monochlorocyclopentene, boiling- 
point 50° (40mm.), and this derivative, though not further acted 
upon by hydrogen chloride, combines readily with chlorine to form a 
trichlorocyclopentane boiling at 196°. Addition of bromine to cyclo- 
pentadiene gives two stereoisomeric 1 . 4-dibromides, one a liquid and 

"Kraemer & Spllker, Ber. S9, 552 (1896). 
'•"Compt. rend. Ui, 945 (1891). 
"Ber. 5», 1436 (1919). 
"Kronsteln, Ber. S5, 4150 (1902). 



CYCLIC NON-BENZBNOID HYDROCARBONS 261 

one a crystalline solid; the dibromides yield two stereo-isomeric aa-di- 
bromoglutaric acids on oxidation. Cyclopentadiene, like isoprene, com- 
bines with quinones to give stable crystalline compounds ; for example, 
with benzoquinone to form the product CnHioOj, melting-point 78°. 
Cyclopentadiene reacts violently with concentrated sulfuric acid and 
dilute sulfuric acid resinifies it. Like cyclohexadiene, its polymers do 
not resemble caoutchouc but are resinous. 

Cyclopentadiene is of special interest on account of the reactivity 
of the CHj group. The hydrocarbon reacts with potassium with evolu- 
tion of hydrogen, forms CjH^Mgl from CHgMgl with evolution of me- 
thane ''\ and readily condenses with aldehydes and ketones under the 
influence of sodium ethylate. Thiele " attributes this reactivity to the 
unsaturated character of the contiguous groups, its condensation with 
aldehydes and ketones paralleling the reactivity of substances contain- 
ing the group = C — CHj — C = with these reagents under the 
same conditions. With acetone, acetophenone, and benzophenone the 
following intensely colored hydrocarbons are formed: 

CH = CH CH3 

I >C = C< dimethylfulvene 

CH = CH CH3 

CH = CH CH3 

I >C = C< methylphenylfulvene 

CH = CH CgHg 

CH = CH C5H5 

I >C = C< diphenylfulvene 

CH = CH C5H5 

Courtot '° has pointed out the similarity in chemical behavior of the 
CH2 in cyclopentadiene with the corresponding group in fluorene and 
indene, which hydrocarbons are also colored. The fulvene derivatives, 
discovered by Thiele, polymerize on warming and absorb oxygen, by 
autoxidation much more rapidly than cyclopentadiene." Stobbe and 
Dunnhaupf have shown that cyclopentadiene polymerizes very slowly 
in the absence of oxygen and, unlike styrol, the polymerization is but 
very slightly affected by light. 

4-Methyl-2-Ethylcyclopentadiene: When the ethyl ester of levu- 

" Grlgnard & Courtot, Compt. rend. 158, 1763 (1914) ; Courtot. Ann. cMm. 4, i» 
(1915). 

"Ber. SS, 666 (1900) ; Si, 68 (1901). 

" Loc. cit. 

'•Engler & Frankenstein, Ber. Si, 2933 (1901). 

"Ber. 52, 1436 (1919). 



262 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

linic acid in alcohol solution is condensed by sodium ethylate, an un- 
saturated cyclic dicarboxylic ester is formed which may have either 
of the two following structures, 

I. CH3 — C — CH, — C — CO^H 



I 



CH C — CH2CH2 . CO^H 

4-methylcyclopen.tadiene-l-carboxy'-S-propionic acid 

II. CH3 — C — CH^ — C — CO2R 

RO,C — CH3 — C C — CH3 

S . 4-dimethylcyclopentadiene-l-barboxy-3-acetic acid 



^2 



The discoverers of the condensation of levulinic ester favor I as being 
the structure of the reaction product. The free acid melts at 218°, with 
evolution of carbon dioxide and formation of the hydrocarbon, the 
structure of which, if the above structure I proves to be correct, is 
4-methyl-2-ethylcyclopentadiene. The hydrocarbon boils at 135°, but 
on distilling at ordinary pressure about one-third is polymerized, the 
tendency to polymerize evidently being abnormally great." 

Methylcyclopentane has been made synthetically by a number of 
methods and has been shown to be present^ in the light distillate from 
Russian petroleum. Methyl-cyclopentane-2-one is formed by heating 
the calcium salt of |3-methyladipic acid. The ketone, boiling-point 
143.5°, may be purified by the sodium bisulfite compound, then 
reduced to methylcyclopentanol- (2) , boiling-point 150.5°-151°, and 
the latter reduced, by heating with concentrated hydriodic acid, to 
methylcyclopentane.'" When made by reducing the iodide, l-methyl-2- 
iodo-cyclopentane, by the copper zinc couple the hydrocarbon showed 

0° 

the following physical properties,*^ boiling-point 71°-72°, djr^ 0.7664. 

It has an odor like well-refined gasoline. A mixture of concentrated 

sulfuric and nitric acid has little effect on it but fuming nitric acid 

alone reacts rather violently, acetic acid, carbon dioxide and water 

being the chief reaction products. Nitric acid Sp. Gr. 1.075, at 115°- 

120° gives chiefly the tertiary nitro derivative. According to Namet- 

kin,'^ 2-nitro-l -methylcyclopentane is also formed, boiling-point 98°- 

22° 
99° at 40 mm., d -^ 1.0381, and succinic and a-methylglutaric acids 

"Duden & Freydag, Ber. S6, 944 (1903). 
"Konowalow, J. Ruaa. Phya.-Chem. 8oc. tS, 125. 
«' Markownikow, Ber. SO, 1222 (1897). 
•'J. Busa. Phya.-vhem. 8oc. iS, 1603 (1911). 



CYCLIC NON-BENZENOID HYDROCARBONS 263 

are also formed. The tertiary nitro derivative can be isolated from the 
secondary nitro derivatives by dissolving the latter in aqueous alkali. 
According to Markownikow ^^ tertiary nitromethylcyclopentane boils 
at 92° (40 mm.) or at 177° at atmospheric pressure, with considerable 
decomposition. Both nitro derivatives give good yields of the corre- 
sponding amines when reduced by tin and hydrochloric acid. The 
tertiary amine may be converted into the corresponding tertiary alco- 
hol by nitrous acid and after distilling, boiling-point 135°-136°, solidi- 
fies to crystals melting at 30°. 

Chlorine reacts energetically with methylcyclopentane at ordinary 
temperatures in diffused daylight.^* The tertiary chloride, prepared 
from the tertiary alcohol, is unstable, partially decomposing on distil- 
lation, boiling-point 123°. By direct chlorination of methylcyclopen- 
tane, derived from petroleum, Markownikow obtained a mixture of 
chlorides from which he was unable to isolate any definite product, 
the presence of cyclohexane in the original methylcyclopentane adding 
to the difficulty. 

Methylcyclopentane has been made by means of the Grignard re- 
action, ring closing being brought about by treating 8-acetylbutyl- 
iodide with magnesium in ether, 

CH2 — CHj — - CO — CH3 CHj — CHg CH3 

I +Mg I >C< 

CH, — CH,I > CH^ — CH2 OMgl 

CHj — CH2 CI13 

I >C< 

CH^ — CH2 OH 

the alcohol being converted 
into the iodide and the latter reduced by zinc dust and acetic acid.*^ 

Cyclopentanone. This ketone has usually been prepared by ring 
closing of the ethyl ester of adipic acid by means of sodium. The 
resulting ester may be regarded as a carbocyclic derivative of aceto- 
acetic ester and by the general method of decomposing such esters to 
ketones, this cyclic ester yields cyclopentanone, 

CH, — CH, — CO,R + Na CH, — CH CO,R 



CH, 



CH2 — cm — CO^R cm — CH„ 



''Ann. SOI, 355 (1S99). 

" Markownikow, loc. cit. 

»»Zelinsky & Moser, Ber. S5, 2684 (1902). 



>C0 



264 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



CH, — CHo 



i: 



>co. 



Thorpe and Best " have described a series of derivatives of cyclo- 
pentanone which are quite stable to acids but are decomposed by alkali 
with rupture of the ring, the ring being stable to acids as long as a CN 
or CO2C2H5 group is present adjacent to the ketone group. The cor- 
responding imino derivatives are exceedingly stable to alkaline hydro- 
lyzing agents. The derivative 2-cyanocyclopentane-l-one is a com- 
pound which resembles ethyl cyanoacetate in many of its properties; 
thus when treated with alcoholic sodium ethoxide it yields a sodium 
derivative which on treating with methyl iodide yields 2-cyano-2- 
methyl-cyclopentane-1-one. These derivatives will not be described 
in any detail but are mentioned since they show the great similarity in 
the chemistry of the open chain and cyclopentane series, and also since 
Best and Thorpe showed that the CN group could readily be removed 
by heating with dilute sulfuric acid yielding derivatives of cyclopen- 
tanone. 



CH2— CH 



CH, — CHo 



CN 
/ 

\ 

CO + NaOC^H, 

/ > 



CN 

/ 

CH,— C.Na 

\ 

CO or 

/ 

CHj — CHj CH, 



CH,— C 



/ 



CN 



\. 



+ RI CH, — C- 



/ 



CN 



-R 



CH, 



\ 

CO -t- dil. acid 

/ > 

CH, 



CH, — CH- 



/ 
CH, 



-R 



CONa 



\ 



CH, — CH, 



/ 



CO 



alkyl cyclopentanones. 



Thorpe and Best also made 2.5-dimethylcyclopentane-l-one, boiling- 
point 149°, and 2-ethyl-cyclopentanone, boiling-point 149°, and 
2-methylcyclopentanone by similar methods. 

Cydopentanone is formed during the carbonization of wood. It 

boils at 129°, d,o° 0.948, n 1.4366." Acetic anhydride enolizes it 

D 

"J. Chem. Soc. 95, 690 (1909). 
" Wallach, Ann. S5J, 330. 



CYCLIC NON-BENZENOID HYDROCARBONS 



265 



to form cyclopentenol acetate. The semicarbazone melts at 205°-207° 
when slowly heated, or at 212°-213° when heated rapidly. It con- 
denses with formic acid ester to form oxymethylenecyclopentanone 
CoHeO : CH(OH), melting-point 72°-73°. A cyclopentanonesulfonal 
is known melting at 127°-128°. 

\ 

C(S02C2H5)jj 

It condenses readily with aldehydes to form derivatives of the general 
type *' 

HC.R 
// 



CH, 



\ 



CH, — C 



/ 



CO 



\ 



HC.R 



The condensation product of the above type formed with benzaldehyde 
melts at 191°, with anisaldehyde 215°, cinnamic aldehyde 222.5°, pipe- . 
ronal 257° and cuminol 145.5°. Acetone condenses with cyclopenta- 
none '° to form the isopropylidene derivative, 

CH3 

/ 

CH, — C = C 



\ \ 



CH, 



■CH, 



CO CH„ 



a liquid very soluble in water, boiling at 195°-199°. Another re- 
action which has been useful in the synthesis of hydrocarbons derived 
from cyclopentanone is the condensation with bromoacetic ester and 
zinc, according to Reformatsky's method, to give cyclopentanolacetic 
ester, the free oxy acid decomposing on heating to give methenecyclo^ 
pentane,^" boiling-point 78°-81°. 

"Voriander, Ber. 29. 1838 (1896) ; Hobohm & Menzel, Ber. S6. 1499 (1903) ; Wal- 
lach, Ooett. Nachr. 1907, 404. 
'" Wallach, Ann. S9i, 868. 
" Wallach, Ann. HI, 825. 



266 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



CHo — CHo 



CHj — CHj 



>co- 



CHj — CH2 



OH 



CH2 — CH2 

I 
CH,— CH, 



-> I >C< 

CHj — CHj CH2CO2H 

■>C = CH2 + H20 + C02 



Methenecyclopentane has a penetrating rather disagreeable odor, 
yields the glycol C6Hi(,(0H)2 on oxidation by permanganate and, fol- 
lowing the general behavior of glycols, this glycol is converted by dilute 
acids to cyclopentane aldehyde. In the same manner a-bromopro- 
pionic acid yields the oxy acid from which ethylidenecyclopentane may 
be prepared. This hydrocarbon, boiling-point 114°, behaves like the 
terpenes in many of the characteristic reactions. Thus it yields a ni- 
troso chloride, which on treating with alkali loses HCl and on hydrolyz- 
ing the resulting oxime, A^-acetylcyclopentane, is formed,^^ 



CHj — CH2 

I 
CH, — CH, 



>C = CH.CH3 > 



CH, — CH, 



CH,— 



CH, 



>C — — CH3 



CI N.OH 



CH, — CH, 



CH, — CH 



\ 
( 



CH, — CH, 



C — C — CH, 



N.OH 



CH, — CH 



\ 
C 



C — C — CH3 

II 





Cyclopentanone reacts normally with the Grignard reagent, giving 
l-methylcyclopentanol(l) with methyl-magnesium iodide,®'' or the 
ethyl derivative with ethyl-magnesium iodide.'^ These tertiary alco- 
hols readily decompose to give alkyl cj'^clopentenes 



CH2 — CH2 OH 



CH, — CH 



CHg — CHj 



>C< 



CH, 



boiling-point 135° 
melting-point 35°-37° 



CH- — CHo 



\ 
C 



C.CH, 



" Wallach, Ann. ses, 274. 

«Zelinsky & Namjetkln, Ber. S5, 2683 (1902). 

•■ Wallach, Ann. 365, 276. 



CYCLIC NON-BENZENOID HYDROCARBONS 



267 



CH, 



CH, — CH, 



-CH, OH 

>C< 



CH, — CH 



CaHj 



\ 



C . C,H. 



boiling-point 155°-157° 
d,° 0.916 



I / 

CHj — CHj 

boiling-point 108° 
d,„° 0.7915 



By condensing with bromoisobutyric acid and decomposition of the re- 
sulting oxy acid, isopropylidenecyclopentane is formed, which, like ter- 
pinolene and other hydrocarbons having a semicyclic double bond of 
this nature, is converted to isopropylcyclopentene by alcoholic sul- 
furic acid, the double bond shifting to the ring, 



CH, — CH2 CH3 

\ / 

c = c 



CH2 — CH2 



CH3 

boiling-point 136°-137° 
d," 0.817 



CHj — CH CH3 

\ / 

C — CH 

/ \ 

CH2 — CHj CH3 



The reactivity of cyclopentanone is also shown by its condensation 
on treating with sodium ethylate or with hydrogen chloride to dicyclo- 
pentenepentanone, which may be reduced first by hydrogen and palla- 
dium and then by sodium to the saturated alcohol. Heating the alco- 
hol with zinc chloride yields cyclopentylcyclopentene, boiling-point 
197°-198°. 



CH— CH, 
CH— CH, 



H,C- 





(I 

Cv 



XH, 



-CH, 



) 



0=c 



/ 




268 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

By the condensation of three molecules of cyclopentanone a ketone 
CisHjoO is formed, which on hydrogenation, as indicated above, yields 
the saturated ketone dicyclopentylcyclopentanone,'* CijHjuO, the cor- 
responding alcohol readily yielding dicyclopentylcyclopentene, 



CH, 

/ \ 

/ \ 



CH, 



CH, 



CH 



CH, 



CH 

/\ 

C CH 



CH, 
/ \ 

/ \ 

CH CH, 



CH, 



H, 



CH, 



CH, 



hoiling-point 290° at 760 mm., d^o" 0.939 



This hydrocarbon may be regarded as a tricyclic "sesquiterpene." 



1 .2-Methylcyclopentanone 
CH3 

Ah 

/ \ 

C = boiling-point 140°-141° 



H,C 



H,C 



CH, 



d,„° 0.917 



This ketone can be prepared from camphor-phorone, or from a-methyl 
adipic acid. It does not condense with aldehydes in the presence of 
caustic soda. 

1 .S-Methylcyclopentanone, boiling-point 144°-145°, daa" 0.913, can 
be prepared from p-methyladipic acid. It condenses readily with alde- 
hydes in the presence of caustic soda, the benzaldehyde compound 
melting at 149°-151° (inactive form) . When prepared from optically 
active p-methyladipic the 1 . 3-methylcyclopentanone is also active.*' 
[a] -j- 124°-133°. When reduced to the alcohol and then converted 

D 
to the iodide, the latter yields 1-methyl-A^-cyclopentene when treated 
with alcoholic caustic potash.** 

"WaHach, Ann. SS9. 182. 

" WaUach, Ann. SSg, 349 ; m, 371. 

"Zellnsky, Ber. S5, 2488 (1902). 



CYCLIC NON-BENZENOID HYDROCARBONS 



269 



CH, 

in 
/ \ 

H,C CH 



boiling-point 69°, d"^ 0.7663 



[a] J) +59.07 



H,C- 



CH 



1-methyl-A^-cyclopentene 

1 . 3-Methylcyclopentanone reacts with methyl-magnesium iodide to 
give 1.3-dimethylcyclopentanol(3), boiling-point 143°-145°. Accord- 
ing to Zelinsky this tertiary alcohol is decomposed by oxalic acid 
mainly to 1-methyl-S-methenecyclopentane,^'' 




CH, — CH — CH, 



CH, — CH, 



\ 

( 



C = CH, 



boiling-point 93° 
0.7734 



,19° 



Potassium permanganate solution oxidizes l-methyl-3-methene- 
cyclopentane to the glycol and 1 . 3-methylcyclopentanone. 

1 . 3-Methylcyclopentanone condenses with acetone °^ to form 4-iso- 
propylidene-l-methylcyclopentane-3-Qne, which can be employed for 
the synthesis of a series of hydrocarbons containing the methyl and 
isopropyl groups in the 1.4 position. 

CHj CHj 

CH CH 

/ \ / \ 



CHg H,C 



CH, 



H,C 



CH, 



CH, 



>C0 + 



H,C C = 



CH3 
CH, 



>C = C- 



= 



" Ber. Si, 3950 (1901). 
•• Wallach, Ann. S9i, 372. 



boiling-point 203°-205° 
d — 0.9315 



270 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The ring may be broken by the rearrangement of the oxime, by sul- 
furic acid, to the isoxime and hydrolyzing the latter by boiling with 
hydrochloric acid to amidocapronic acid,°° a reaction which is very 
generally applicable to the cyclic ketones. 




1 .1-Dimethylcyclopentane: Kishner^"" finds that all of the re- 
actions of dimethylcyclobutylcarbinol, which were studied by him, are 
abnormal in that the cyclobutane ring is changed to the cyclopentane 
ring. The carbinol may be prepared by the Grignard reaction ap- 
plied to the ester of cyclobutanecarboxylic acid, 



CH,< >CH.CO,R 



+ 2CH3MgI 



CH, 



CH, 



■^CH,< >CH — C< 

CHj CHj 

OH 



When this carbinol is treated with hydrogen bromide the product 
formed is 2-bromo-l.l-dimethylcyclopentane, which on treating with 
alcoholic caustic potash yields the A^ unsaturated hydrocarbon. 



CH, 
/ \ CH3 

CH2 CH — C< 

\ / ICH3 

CH, OH 



CHBr- 
+ HBr CH2< 
> CH,— 



C< 



CH, 



ir*^^- 



" WaUach, Ann. S12, 184 

»»/. Russ. Phys.-Ohem. Soc. iO. 994 (1908). 



CYCLIC NON-BENZENOID HYDROCARBONS 271 

CH, 



CH 
\ 



CH — C< 



CH3 

boiling-point 78°-78.5° 



2f)° 
CH,-CH, d— 0.7580 

20° 
n^ 1.4190 

It has an odor resembling naphthalene. On oxidation by nitric 
acid it yields aa-dimethylglutaric acid. According to Kishner/"^ both 
hydrobromic and hydriodic acids reacting on the above carbinol yield 
halogen derivatives, which on treating with alcoholic caustic potash 
yield 1.1. -dimethyl-A^-cyclopentene together with the isomeric hydro- 
carbon 1 . 2-dimethyl-A^-cyclopentene. When the bromide, obtained 
from the carbinol, is reduced by the copper-zinc couple, a saturated 
hydrocarbon is formed which Kishner ^"^ regards as 1 .1 Dimethylcy- 

20° 
dopentane, boiling-point 88.3°-88.5°, d —s- 0.7653. 

1 .S-Dimethylcyclopentane, obtained by reduction of 1 . 2-dimethyl- 

9fl° 

A^-cyclopentene by Sabatier's method, boils at 92.7°-93°, d~ 

20° 
0.7534, n-^ 1.4126. 

1 .2-Dimethyl-A^-Cyclopentene, one of the products obtained by 
the decomposition of dimethylcyclobutylcarbinol, as described above, 
is identical with the hydrocarbon made by Maquenne^"^ from per- 
seitol. On reduction by means of concentrated hydriodic acid it is 
converted to a hydrocarbon C^H^^, which Aschan^"* regarded as 1.3- 
dimethylcyclopentane, but Kishner ^"^ states that more probably it is 
1.2-dimethylcyclopentane together with a little methylcyclohexane. 
The olefine reacts with hydrobromic acid to form an unstable bromide, 
yields a nitrosochloride melting at 73°-75°, and on oxidation yields 
Y-acetobutyric acid. 

CHj — C — CH3 
/ 



CH, 

\ 
CH, 



CH, 





CH2- 


- COCH3 




/ 




CH 


2 
\ 






CH,- 


-CO2H 



"»■/. Uuis. P?iys.-Chem. goo. iO, 994 (1908). 
'"J. Ruaa. Phya.-Ohem. 80c. 97, 509 (1905). 
'"J. Chem. Soc. Aba. 1S93 (1), 635. 
'"Chemle d. AlicycUscben Verb, p. 473. 
'"J. Buaa. Phya.-Ohem. Soc. iO, 994 (1908). 



272 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

1 .S-Dimethylcyclopentane was synthesized in an optically active 
form by Zelinksy^"* from d.-1.3-dimethylcyclopentanol(3) by con- 
verting the alcohol to the iodide and reducing the latter by the well- 
known method of treating with zinc dust and acetic acid. The hydro- 

1fi° 
carbon boils at 90.5°-91°, d ^0.7497, [a] + 1.78°. 

1-Methyl-S-Ethylcyclopentane was prepared in an optically active 
form by Zelinsky in a manner similar to that employed for the 1.3- 

16° 

dimethyl derivative. The hydrocarbon boils at 120.5°-121°, d —^ 

0.7669, [«]■[) + 4.34°. It is noteworthy that the optical rotations of 
the active saturated hydrocarbons are usually much lower than the 
unsaturated hydrocarbons of the same carbon atom structure. 

1-Methyl-S-Isopropylcyclopentane ^"^ is formed by reducing cam- 
phorone by Sabatier's method at 130° to dihydrocamphorone, which 
on further reduction yields the saturated hydrocarbon, boiling-point 
132°-134°, dig" 0.773. 

1 .2-Dimethyl-S-Isopropylcyclopentane ^"^ has also been made from 
camphorone by hydrogenation to dihydrocamphorone and treating this 
ketone with methyl-magnesium iodide, decomposing the resulting ter- 
tiary alcohol and hydrogenating the resulting cyclopentene derivative. 
The saturated hydrocarbon boils at 146°-148°, die" 0.786. 

l-Methyl-2-Isopropylcyclopentane: When the bicyclohexane deri- 
vative prepared by Kishner from camphorone by his hydrazine method, 
is treated with hydrogen bromide the three-carbon ring is broken in 
such a way as to form a cyclopentane derivative, a very general result 
when it is theoretically possible to form either a cyclopentane or cyclo- 
hexane derivative by the rupture of a three-carbon ring. 

H, H 







£H, 

-Cr-Br 

:H3 CH3 



Decomposition of the resulting bromide with alcoholic caustic potash 
yields the isopropylidene derivative almost exclusively but decompo- 
sition by aniline gives the two possible isomers. 

•"Ber. S5, 2677 (1902). 



CYCLIC NON-BENZENOID HYDROCARBONS 



273 



-C\ + aniline 



/CH3 




CH, 



CH3 ^"J 

Both of the above unsaturated hydrocarbons on catalytic hydrogena- 
tion yield l-methyl-2-isopropylcyclopentane, boiling-point 142.5°, 

d ^ 0.7833. 



Cyclopentenes. Physical Peopekties * 



Name 
Cyclopentene 



Formula 



B.-P °C 



n- 



ca, 



:> 



■4" -4° 

44.5° 0.773 1.421 



CHa- 



Methyl-A'-cyclopentene 

Methyl-A'-cyclopentene 

Ethyl cyclopentene 

1.1-dimethyl-A^-cyclopentene CHa \ 

CH, 



69. 

72. 



CHa>. 



> 
> 

\— aa 108. 

78. 



1 2-dimethyI-A'-cy clopentene 



ca 



-CH. 103. 



0.765 1.413 

0.772 1.427 

0.796 1.443 

0.758 1.419 

0.794 1.442 



CH.. 



1.1.2-trimethyl-A'-cyclopen- pg^> I \ 

tene | / 

CH. 



108. ° 0.782 1.431* 



1 5.3-trimethyl-A'-cyclopen- 
tene 



\, 



-CH. 119. 



0.796 1.442* 



• Auwers, Ann. il5, 110 (1918). 



20° 



• t He refractive Indices marked wltli an asterisk are for n — 



274 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



l.l-diethyl-A'-cyclopentene c'Hs'^ \ 144. ° 0.808 1.446 



C2HB 




140. " 0.803 1.447* 



1 .2-dietliyl-A'-cyclopentene 



1 .3-diniethyl-2-ethyl-A'- 
cyclopentene 



C2HB 
C2H6 

1.2.3-triethyI-A'-cyclopen^ I >-C.H, 181.5° 0.814 1.451* 



CiHt 



■{ 



C3H5 

Naphthenic Acids: These acids probably occur in more petroleums 
than is commonly supposed, although they are usually associated with 
Russian petroleum. The naphthenic acids occurring in Russian petro- 
leum include relatively simple low-boiling acids so that, the mixture 
of acids, as they are obtained by treating with aqueous alkali and 
precipitating with acid, possesses a marked, very persistent and rather 
disagreeable odor. The Gulf Coast petroleums also contain organic 
acids but they are of high boiling-point and, when separated from lu- 
bricating oil, are practically odorless and are easily salted out of their 
solutions in aqueous solutions. The acids in the Gulf Coast oils have 
never been studied to the extent of determining their nature, but their 
alkali solutions have pronounced emulsifying and foam producing 
power and may accordingly find employment in compounding cutting 
oils or emulsions but can hardly be employed in soaps on account of 
the ease with which their alkali salts, or soaps, are salted out. 

Markownikow ^"^ fractioned the methyl esters of the Russian naph- 
thenic acids. The fraction distilling at 160°-165° was essentially 
CjHiiO^CHj. The purified free acid distilled at 213°-214° and the 

20° 
purified methyl ester boiled at 164°-166°, d -^ 0.90509. The amide 

'«A»». sen, 360 (1899). 



CYCLIC NON-BENZENOID HYDROCARBONS 275 

melts at 121°-123.5° and by converting the amide to the amine, a 
secondary amine was formed which is perhaps identical with the sec- 
ondary amine resulting from the reduction of secondary nitromethyl- 
cycbpentane. The acid methylcyclopentane-2-carboxylic acid 

CH2 — CH . CH3 

CH, 

\ 

CHj, — CH.CO^H 

isolated by Perkin and Freer,^"' boils at 219°-219.5° and an isomeric 
acid, probably the 1.3 acid, prepared by Euler,"" boils at 220°. The 
aldehyde derivatives of methylcyclopentane have been observed by 
Markownikow and the two synthetic acids has not been satisfactorily 
explained. 

The starting point in the researches of Perkin and Freer '^' was the 
condensation of sodio-malonic ester with 1.4-dibromopentane, 
CHj — CH — CH3 CO2R 

/ \ / 

Cn, Br + 2Na + CH^ 



^2 



\ \ 

CH3r CO,R 



->CH, 
\ 



CH, — CH — CH3 



CO^R 
CH,-C< 

CO,R 



On heating the free dicarboxylic acid a few degrees above its melting- 
point it decomposes to carbon dioxide and l-inethylcyclopentane-2-car- 
boxylic acid, boiling-point 219.5°-220.5°. These carboxylic acid deri- 
vatives of cyclopentane are of interest since the simpler naphthenic 
acids of Russian petroleum are evidently derivatives of cyclopentane. 
The acid named above has a most disagreeable odor, somewhat resem- 
bling valeric acid. It is not acted upon by bromine at ordinary tem- 
peratures but at 100° rapid substitution occurs with evolution of hy- 
drogen bromide. 

Zelinsky^^^ has applied the Grignard reaction to the preparation of 
naphthenic acids but the yields are usually very poor. From 1-methyl- 

'"J. Chem. Soe. 53, 199 (1888). 
"»Ber. 28, 2952. 

"'J. cnem. Soe. S3, 195 (1888). 
"'Ber. SS, 2687 (1902). 



276 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



3-bromo-cyclopentane the acid l-methylcyclopentane-3-carboxylic acid 
was prepared by passing carbon dioxide into the ethereal solution of 
the magnesium derivative. The acid distills at 115°-116° (15 mm.), 

22° 
d -j3- 1.006; the amide melts at 149°-150°. This acid is possibly iden- 
tical with the methylcyclopentanecarboxylic acid described by Euler, 
referred to above. 

Rearrangements of the iodohydrins of the methylcyclohexenes to 
aldehyde derivatives of methylcyclopentane have, been lobserved by 
Tiffeneau.^^' Thus the iodohydrin of A'-methylcyclohexene, on treat- 
ing with silver nitrate is converted into the aldehyde, which on oxi- 
dation yields the corresponding acid, previously obtained by Zelinsky, 



CH, 



CH, 




CH, 



-^ 



^^ 



H 




J 




CH, 




H OH 



CHO 



cqH 



The iodohydrin of cyclopentene does not rearrange but gives the 1 . 2- 
oxide. In the case of the phenylcyclohexane derivative ^" or substi- 
tuted phenyl derivatives, rearrangement to the cyclopentane ring does 
not take place but the phenyl group migrates to the a-position with 
the formation of a cyclohexenol, which is converted to the isomeric 
ketone. 

Cyclopentane-1 .2-Dicarboxylic Acid has been prepared from 1.3- 
dibromopropane and sodium-malonic ester and also by the action of 
iodine on the disodium derivative of the ester, 



CH, 



/ 

2 
\ 



CH^ — C.NaCCOaR)^ 



+ Ia 



CH, 



CH^ — C.NaCCOjR)^ 



/ 

2 
\ 



CH^ — CICO^R), 



CHi, — C(C0,R)5 



and decomposing the tetracarboxylic acid by heating, in the usual 
manner, 

'"Compt. rend. 159, Til (1914). 

>"Le Brazidec, Compt. rend. 1S9, 774 (1914). 



CYCLIC NON-BENZENOID HYDROCARBONS 



277 



CH, 



2 
\ 



CH3-C< 



CO^H. 



CH,-C< 



CO,H. 
CO,H 
"CO,H 



CH, — CH — CO,H 



CH, 



2 
\ 



CH, — CH — CO,H 



It is known in as and trans forms, the cis form readily forming an 
anhydride. 

l-Methylcyclopentane-2.S-Dicarboxylic Acid, melting-point 99°- 
104°, has also been prepared by one of Perkin's methods, i. e., condens- 
ing 1 . 3-dibromobutane with the disodium derivative of the ethyl ester 
of ethane tetracarboxylic acid, followed by decomposition of the tetra- 
carboxylic acid in the usual manner.^^^ 

The cis and trans modifications of cyclopentane 1.2.4-tricarboxy- 
lic acid are known, and are best prepared by the reaction of ethyl a|3-di- 
bromo-propionate on the disodium derivative of ethyl propane-a a y Y" 
tetracarboxylate.^^' 



CH, 



CO^R 






C(Na)< 






/ CO^R 


BrCH^ CICO^R),- 
+ ] -^ CH,< 

BrCH.CO,R C(C02R)2- 


-CH, 


\ CO,R 


- CHCO.R 


C(Na)< 






CO^R 







CH, 



2 
\ 



CO,H 
CH — CH, 



CH — 
0,H 



i 



CH.CO^H 



. The trans form, melting-point 129°-130°, yields the anhydride of the 
cis form when heated with acetic anhydride and the anhydride then 
may be hydrolyzed to the pure cis form, melting at 146°-148°. 



""Fargher, J. Ohem. Soc. m, 1355 (1920). 

""Perkln & Goldsworthy, J. Chem. Soc. 105, 2666 (1914). 



Chapter VIII. The Cyclic Non-ben- 
zenoid Hydrocarbons. 



The Cyclohexane Scries. 



The conception of cyclohexane and its derivatives as "hydroaro- 
matic" compounds has served a useful purpose in connection with the 
study of the constitution of benzene. Reduction of ortho, meta and 
para derivatives of benzene yield the corresponding derivatives of 
cyclohexane which would not be expected from Ladenburg's prism 
formula. It has also been shown that tetrahydrobenzene and dihydro- 
benzene do not have the bridged structures shown below, 

H H, 

C C 



H3C 



/ 



H,C 



\ 



\ 



CH, 



C 
H 



/ 



CH, 



/ \ 

HC CH 

\/ 
/\ 



HC 



CH 



\ / 
C 
H, 



and Baeyer has shown that the tetrahydroterephthalic acids do not 
possess bridged ring structures but contain double bonds, the addition 
products indicating that the two isomeric acids have double bonds in 
the two positions shown below. 



CO,H 




CO^H 



and 



278 



CO^H 




CO^H 



THE CYCLOIIEXANE SERIES 



279 



It should be borne in mind that derivatives of hydrocarbons such 
as cyclohexane are capable of exhibiting stereoisomerism when two 
or more substituents are present. Thus if the six carbon atoms are 
conceived to lie in one plane, as in the plane of the paper, then six of 
the hydrogen atoms in cyclohexane will lie above the plane and six 
below the plane. Cyclohexanecarboxylic acid can obviously exist in 
only one form but a cyclohexane dicarboxylic acid can exist in two 
forms. Thus the 1.4-dicarboxylic acid derived from terephthalic acid, 
studied by Baeyer, can exist in two stereo isomeric forms. 




\ CO,H H 



■H HO^ci 




Baeyer likened these stereoisomers to fumaric and maleic acids, con- 
sidering the double bond and the ring structure as preventing free 
rotation in much the same manner. 



H CO^H 

\ / 

C 

/\ 
\/ 

c 



CO,H 



H 

maleic acid 




maleinoid 
cyclohexane-1 .4- dicarboxylic acid 



HO,C H 

\ / 

C 

/\ 
\/ 

c 

/ \ 

H CO3H 

fumaric acid 





fumdroid 
cyclohexane-1 .4-dicarboxylic acid 



280 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Cyclohexane and its alkyl derivatives probably occur in more petro- 
leums than is generally known but this hydrocarbon and its mono- 
methyl and dimethyl derivatives were long ago recognized as impor- 
tant constituents of the light naphtha from Russian petroleum, hence 
the term "naphthenes" suggested by Markownikow. Careful examina- 
tion of the lighter distillates of the petroleums from southern Cali- 
fornia, Mexico and the southern Texas and Louisiana fields will un- 
doubtedly show the presence of cyclohexane and its simpler alkyl de- 
rivatives. Quite a variety of methods have been employed for the 
preparation of cyclohexane and its derivatives but the methods of cat- 
alytic hydrogenation of Sabatier and Senderens Ipatiev and Skita are 
so far superior to most of the others that the latter are generally only 
of historical interest. A number of syntheses of cyclohexane and its 
derivative will be briefly mentioned, as follows: 

(1) Treatment of 1 . 6-dibromohexane with sodium.^ 

(2) Reaction of 1 . 5-dibromopentane, malonic ester and sodium 
ethylate, yielding cyclohexane-l.l-dicarboxylic acid, which in turn 
yields cyclohexanecarboxylic acid by decomposition. 

(3) Heating the calcium salt of pentane-1.5-dicarboxylic acid, 
forming cyclohexanone.^ 

(4) Condensation of the ethyl ester of pentane-1.5-dicarboxylic 
acid to form the ester of cyclohexanone-2-carboxylic acid. 

(5) Condensation of two molecules of succinic ester' to the 2.5- 
dicarboxylic acid derivative of the 1.4-cyclohexane-dione; this readily 
loses CO2 to give the 1.4-diketone, which can be reduced by the usual 
methods to 1.4-cyclohexanediol from which cyclohexane may be pre- 
pared by reducing with hydriodic acid or the iodide converted into 
A^- *-cy clohexadiene. 

(6) Condensation of 8-ketonic acids to 1.3-cyclohexanediones. 

(7) Addition of sodium malonic ester to a (3 unsaturated ketones 
to form derivatives of 1 . 3-cyclohexanedione. 

(8) Condensation of two molecules of acetoacetic ester with alde- 
hydes to form open chain diketonic acids which condense further to 
cyclic unsaturated ketonic esters which readily lose COj on saponifi- 
cation to give cyclohexenone derivatives. Similar products are ob- 
tained by the condensation of methylene iodide and two molecules of 
sodium acetoacetic ester.'' 

'W. H. Perkin, Jr., Ber. Srt, 216 (1894). 

2 Markownikow, Compt. rend. 110, 466 (1890) ; 115, 462 (1892), 
'Baeyer, Ann. iJ,S, 106 (1888) ; Ber. SS, 1276 (1890). 
•Hagemann, Ber. «fi, 876 (1893). 



THE CYCLOHEXANE SERIES 



281 



(9) Condensation of aliphatic aldehydes and ketones, for ex- 
ample, methyl heptenone to a mixture of meta-xylene and dimethyl- 
cyclohexene; citronellal to isopulegol, etc. 

(10) Addition of chlorine to benzenoid hydrocarbons, for example, 
the addition of chlorine to benzene to form hexachlorocyclohexane. 

(11) The indirect reduction of unsaturated substances by first 
adding bromine or hydrobromic acid and then replacing the bromine 
by hydrogen by treating with acetic acid and zinc, for example the 
conversion of dihydro and tetrahydroterephthalic acids to cyclohexane- 
1.4-dicarboxylic acid. 

(12) The hydrogenation or reduction of benzenoid hydrocarbons. 
As mentioned above, these methods, particularly the well-known 
method of Sabatier and Senderens, have practically superseded all the 
older methods and promise to become of industrial importance for 
the hydrogenation of benzene to cyclohexane, phenol to cyclohexanol 
and cyclohexanone, both the latter products being of value as com- 
mercial solvents (see below). The ease of reduction or hydrogenation 
varies considerably with the number and character of the substituent 
groups. Thus terephthalic acid and the dihydro and tetrahydro-tereph- 
thalic acids are reduced with difficulty, but mellitic acid is easily re- 
duced by reducing agents to cyclohexanehexacarboxylic acid. 



HC(^H 



Hqc^ 


CO,H 

rl 
V 

CO^H 


r^.eH "^" 




HOC- 


J-cqH HqcH 



H.CQjH 



With the phenols the ease of reduction increases with the number of 
hydroxyl groups, resorcin being easily reduced to cyclohexane- 1.3- 
dione. 

Benzene is reduced to cyclohexane in the presence of catalytic 
nickel at^ 180°-250°, but the refinements of the process as carried out 
industrially are not generally known. Cyclohexane was manufactured 
in this way in the United States and in Germany during the recent war, 
the cyclohexane being used to some extent as a motor fuel ^ for aero- 
planes. In the case of the alkyl derivatives of benzene some decompo- 

■ Dayton Metal Products Co. Brit. Pat. 133,288; 133,667 (1919). 



282 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

sition also takes place, for example, in the hydrogenation of para- 
cymene at 170°-180° to para-menthane, small proportions of methyl 
and ethylcyclohexane are also formed. At about 300° the mixture in 
equilibrium in the presence of nickel consists chiefly of benzene and 
at this temperature dehydrogenation of cyclohexane to benzene can be 
effected. The relative ease with which this change is brought about 
makes possible the detection of small proportions of cyclohexane in 
the presence of normal hexane, and other saturated hydrocarbons, the 
fraction distilling at 75°-85° being passed over nickel at 300° and the 
distillate treated with concentrated sulfuric acid to remove and poly- 
merize olefines and then treated with nitrating acid mixture to remove 
the benzene which may be identified as crystalline dinitrobenzene.' 
As regards the hydrogenation of benzene to cyclohexane by hydrogen 
in the presence of platinum black Willstatter and Hatt ^ show that the 
reaction proceeds quantitatively at atmospheric pressures in about six 
hours in glacial acetic acid solution, using about . 1 part of platinum 
black. The hydrogenation is distinctly slower when glacial acetic acid 
is not used as a solvent. The catalyst is exceedingly sensitive to traces 
of thiophene, less than 0.01 mg. of thiophene per gram of benzene com- 
pletely preventing the hydrogenation. Toluene is reduced to methyl- 
cyclohexane under the same conditions much more readily than in the 
case of benzene, i. e., in about 31/2 hours. 

The hydrogenation of benzene derivatives to the corresponding de- 
rivatives of cyclohexane may conveniently be considered here. As- 
chan ' reduced sodium benzoate by sodium amalgam, neutralizing the 
caustic soda by carbon dioxide, as fast as formed, thus preventing 
the precipitation of the sodium benzoate by the concentrated caustic 
soda. When the hydrogenation is incomplete a considerable pro- 
portion of A^-cyclohexene carboxylic acid is formed. Ipatiev " ob- 
tained yields of 40 to 50 per cent of cyclohexane carboxylic acid by 
his method of reducing at 300°-320° and hydrogen at about 210 atmos- 
pheres in the presence of nickel oxide. Phthalic acid under the same 
conditions is more readily reduced to the corresponding cyclohexane- 
1 . 2-dicarboxylic acid and this method is probably the best method of 

"Tausz, Chem. Ztg. 37, 334 (1914). According to Zelinsky (Cf. Wieland, Ber. 45, 
484 [1912]), hydrogen Is dissociated from cyclohexane, with the formation of benzene, 
at temperatures below 300° and in the presence of nickel ; under the same conditions 
cyclopentane and cyeloheptane are .stated to be practically unchanged. In the absence 
of a catalyst cyclohe.xane yields considerable benzene at 490° ; normal hexane at 
slightly higher temperatures yields methane, amylene and other hydrocarbons. (Jones, 
J. Chem. Soc. 107, 1582 [1915].) 

'Ber. I,S, 1471 (1912). 

'Ber. »,, 1864 (1891). 

'Ber. 41, 1005 (1908). 



THE CYCLOHEXANE SERIES 283 

preparing this acid. It is noteworthy that at the same temperatures 
and with the same catalyst but without the use of pressure no hydro- 
genation of phthalic acid could be detected. The older method of re- 
duction by means of sodium and amyl alcohol was used successfully 
for the reduction of anthranilic acid to 2-amidocyclohexanecarboxylic 
acid, and also para-amidobenzoic acid to 4-amidocyclohexanecarboxy- 
lic acid.'" Osterberg and Kendall '^ used sodium and alcohol for the 
reduction of the oxime of cyclohexanone to cyclohexylamine and also 
report that the method of Sabatier and Senderens gives good yields of 
the amine from the oxime, but state that the method of reducing aniline 
to cyclohexylamine, according to Ipatiev, did not give satisfactory re- 
sults. Ipatiev reported yields of 40 to 50 per cent of the amine by 
reducing aniline with hydrogen and nickel oxide, employing a hydro- 
gen pressure of about 120 atmospheres at 220°-230°. Quinoline could 
not be hydrogenated by Padoa and Carughi,^^ using the method of Sa- 
batier and Senderens, but Ipatiev succeeded in reducing it to deca- 
hydroquinoline by his high pressure method. Diphenylamine also can- 
not be reduced to dicyclohexylamine by the Sabatier and Senderens 
method, other products being formed, but the Ipatiev method, at 225°- 
230°, gives a good yield of dicyclohexylamine.'^ Paals' method on 
aniline is reported to give a yield of about 10 per cent of cyclohexyl- 
amine. Osterberg and Kendall recommend Ipatiev's method for the 
preparation of cyclohexane and cyclohexanol. Ipatiev finds that nickel 
oxide hydrogenates benzene and its derivatives several times faster 
than reduced nickel in the presence of hydrogen under pressure at 
about 255°. The cyclohexane so produced is practically pure and the 
reduction is complete in about 1% hours when using 2 g. nickel oxide 
to 25 g. benzene. Decomposition with the formation of methane and 
the separation of carbon begins to be noticeable at about 290°. Un- 
der the same conditions Ipatiev reduced phenol to cyclohexanol, di- 
phenyl to dicyclohexyl, naphthalene (in two successive operations) to 
decahydronaphthalene, dibenzyl to dicyclohexylethane, |3-naphthol to 
(3-hydroxydecahydronaphthalene and a-naphthol to a-hydroxydecahy- 
dronaphthalene. Anthracene was reduced by Godchot '* by reduced 

"Einhorn & Meyenburg, Ber. 27, 2466 (1894). In the case of anthranilic acid the 
reaction proceeds in w/o ways, pimelic acid also being formed, probably through the 
intermediate formation of salicylic acid. 

NHj OH CHaCHjCO^H 

C«H4< > C8H4< + Hj,0 + 4H > I 

COeH CO2H CH2CH2CH2CO2H 

"J. Am. Chem. Soc. ^, 2616 (1920). 

"At«. Accad. Lincei (5) 15, 113 (1907). 

"Ipatiev, Ber. 1,1, 991 (1908) ; J,0, 1281 (1907). 

"Oompt. rend. 139, 605 (1904). 



2S4 CHEklSfRY OF THE NON-BENZENOlD HYDR6CARB0N^ 

nickel at atmospheric pressure to tetra and octohydroanthracene, but 
Ipatiev succeeded in completely reducing it to perhydroanthracene, 
C14H24, by his high pressure method, using nickel oxide as a catalyst. 
By one operation tetrahydroanthracene, melting-point 103°-105°, is 
the chief product; a second operation yields mainly decahydroanthra- 
cene, C^Ji^o, melting-point 73°-74°, and a third operation using the 
decahydroanthracene yields the completely reduced hydrocarbon, 
C^Ji^i, melting-point 88°-89°. Slight carbonization and formation 
of methane occurs at the temperatures employed, i. e., 260°-270°. 
Phenanthrene was also reduced in steps, the completely reduced hydro- 
carbon being finally obtained. At lower temperatures the hydrocar- 
bon was not completely reduced, the temperatures required being con- 
siderably higher than for the reduction of benzene, 

At 320° phenanthrene > chiefly C14H12 and CnHi^ 

At 360° " > " Ci,Hi8 

At 370° " > " Ci^H,, 

r— 

The completely reduced phenanthrene is a liquid boiling at 270°-276°, 
does not crystallize at — 15° and is inert in the cold to nitrating acid 
mixture, bromine and aqueous permanganate. Phenyl ether is decom- 
posed under the conditions of Ipatiev's method, yielding a mixture con- 
sisting of cyclohexane, cyclohexanol and cyclohexyl ether (temperature 
employed 230°). 

As regards the practicability of developing Ipatiev's method into 
an industrial process, it may be pointed out that the pressures employed 
are at least no higher than the lowest pressures employed for the syn- 
thesis of ammonia from nitrogen and hydrogen, and the temperatures 
required are very much lower. The technique of operating at such 
pressures on an industrial scale has been improved to a degree which 
should make Ipatiev's process entirely feasible industrially. In con- 
nection with the hydrogenation of complex benzenoid hydrocarbons it 
should be noted that attempts have recently been made to hydrogenate 
coal under high pressures to oily hydrocarbon mixtures from which 
oily hydrocarbons, or polynaphthenes having lubricating value, may 
be obtained. This work, the details of which are not yet available, are 
undoubtedly based upon the earlier findings of Ber^us ^^ that, under 

" According to U. S. Pat. 1,342,790, issued to F. Bergius, pulverized coal 1b mixed 
with a mineral oil boiling above 200° and introduced as a thick paste into a reaction 
vessel, where it Is heated to about 400° and subjected to the action of hydrogen, with- 
out Introducing any catalytic substance, under a pressure of 100 atmospheres. Partial 
hydrogenation is claimed, a heavy oil boiling about 300°-400° being formed from the 
coal substance. Bergius claims that with soft coals as much 85% of the coal may 
thus be converted into oily liquid or oil soluble products. 



. THE CYCLOHEXANE SERIES 285 

very high pressures, hydrogenation can be effected without a catalyst. 
For the hydrogenation of such an impure material as coal, it is obvious 
that either a high pressure method of the Bergius type, or the em- 
ployment of a catalyst not poised by sulfur, will be required. 

Skita has shown that the benzene ring may be reduced at ordinary 
temperatures by colloidal platinum. Thus cinnamic aldehyde is con- 
verted into cyclohexyl propyl alcohol by reduction in this way using 
very slight pressures, i. e., about one atmosphere. Cyclohexanone is 
also very rapidly reduced to cyclohexanol in the same manner. Acetic 
acid is usually employed as a solvent. The unsaturated ketone pu- 
legone also yields the saturated alcohol menthol under the same con- 
ditions.^' For research and laboratory preparations, Skita's method 
is usually to be preferred although the method does not appear to have 
been applied to many reductions of the benzene nucleus. Aqueous 
alcohol may also be employed as a solvent. In the reduction of 
pulegone to menthol 5 grams, in 40 c.c. acetic acid, and with colloidal 
platinum and a little gum arable as a protective colloid to retard pre- 
cipitation of the metal, the reduction is complete in sixty minutes. 

Cyclohexane: The presence of cyclohexane in Russian petroleum 
was shown by Markownikow " and Young found it also in a specimen 
of gasoline from an American petroleum, but the exact origin of the oil 
examined by Young is not known. Its presence in the fraction boiling 
at 80°-81° may be indicated by the physical constants of the fraction 
and the isolation of adipic acid among the products of oxidation by 
nitric acid. The boiling-point is usually given as 80.8°, but the physi- 
cal properties of a specimen of the hydrocarbon carefully purified by 
several treatments with slightly fuming sulfuric acid are given by 

Auwers^^ as follows, boiling-point 80.0°-80.2° at 749 mm., d ^^|- 
0.7869, nj3 1.42910, Mj) 27.66 (calculated 27.71). 

Cyclohexane is slightly more stable to heat than normal hexane, but 
the decomposition of both is noticeable at 500° and under pressure. 
According to Ipatiev ^' it is decomposed at 500°-510° and in the pres- 
ence of alumina (110 atmospheres pressure) to a complex mixture of 
decomposition products among which methyl cyclopentane was identi- 
fied by means of the easily formed tertiary nitro derivative 

"Ber. iS, 1496 (1915). 

"Ber. SO, 974 (1897). 

"Ann. no, 262 (1915). 

"J. Rus8. Phys.-Chem. Soc. iS, 1431 (1912). 



286 CHEMISTRY OF THE NON-BENZENOID HYDfiOCARBONS 
CH„ — CH, NO, 



-'2 



I >C< Cyclohexane is practically inert to bro- 

Cxij — CHj CI13 

mine in the cold and is only very slowly reacted upon at its boiling- 
point and in diffused daylight, but bromination is rapid in direct sun- 
light. In the presence of anhydrous aluminum bromide a mixture of 
high boiling products is formed, but when dibromo cyclohexane or 
cyclohexene is similarly treated it is possible to identify hexabromo- 
benzene among the reaction products.^" 

Considerable has been written about the so-called "formolite" re- 
action which, according to Nastjukow, the cyclohexenes and other non- 
benzenoid cyclic hydrocarbons undergo when treated with formalde- 
hyde in the presence of concentrated sulfuric acid or aluminum chlo- 
ride. According to Nastjukow ^^ a mixture of cyclohexane, anhydrous 
aluminum chlorine and trioxymethylenes react forming a mixture of 
condensation products but no definite reaction product was isolated. 
The reaction is usually carried out using sulfuric acid as the condens- 
ing reagent and the saturated acyclic hydrocarbons are supposed not 
to give the "formolite" reaction. It does not appear that any definite 
reaction products have ever been isolated and the character of the 
reaction therefore is at present a matter of speculation; also it does 
not appear that the reaction has been carried out with a suflBcient num- 
ber of pure hydrocarbons to warrant the proposal that it be employed 
in the study of petroleum fractions to determine what types of hydro- 
carbons are present. As carried out according to Nastjukow one vol- 
ume of the hydrocarbon mixture is treated with one volume of concen- 
trated sulfuric acid and then one-half volume of concentrated (40%) 
formaldehyde is gradually added, with agitation. A precipitate is 
formed which after washing with gasoline, water and ammonia, may 
be dried and powdered, the product resembling a brown resin. The 
higher boiling oils generally yield larger proportions of "formolite" 
resin than the lighter oils, but the yield of resin appears to vary evi- 
dently with the conditions of the operation. The product prepared 
according to Nastjukow's directions contains considerable sulfur, a 
spindle oil giving a resin containing 6.98 per cent sulfur and 6.66 per 
cent oxygen. When the mixture is kept cold the condensation product 
is liquid and does not contain sulfur.^^ According to Gurwitsch "^ only 

"iBodroux & Taboury, Bull. soc. cMm. 9, 592 (1911). 
"J. Russ. Phys.-Chem. Soc. ^7, 46 (1915). 
"J. Bms. Phua.-Chem. Soc. i2, 1596 (1910). 
" Wlssensch, Grundlagen d. ErdSlbearb., 46. 



THE CYCLOHEXANE SERIES 287 

certain olefines such as "partially reduced aromatic compounds" and 
aromatic hydrocarbons react to give formolite resins. Terpenes are 
said to give "formolite" resins, but they are very energetically poly- 
merized, oxidized and esterified by sulfuric acid alone and it is en- 
tirely obscure what the function of the formaldehyde is supposed to 
be. Most books on petroleum testing describe the "formolite" reaction 
and often use the phrase "formolite number," but this test and these 
phrases are meaningless until the reaction is studied in many cases, not 
only of cyclohexane, the cyclohexenes, and commercial oils of known 
chemical character, but also applied to a series of definite pure hydro- 
carbons of various types. Cyclohexenes should give "formolite" resins 
since they polymerize readily with sulfuric acid alone and cyclohexa- 
diene reacts violently with sulfuric acid. Nastjukow may have dis- 
covered something, but, if so, no one has been able to determine what 
it is. 

A series of metallo derivatives of cyclohexane has been prepared by 
Griittner,^* who has prepared cyclohexyl derivatives of lead, tin and 
bismuth. The starting point in all cases was the reaction of cyclohexyl 
magnesium bromide on the chloride or bromide of the other metal. 
Bromocyclohexane reacts with magnesium in ether very much like 
n . hexyl bromide, the secondary reaction 

RMgBr + R.Br -^MgBr2 + R.R., 

taking place in both cases. The cyclohexyl derivatives show slight 
differences from the simple alkyl derivatives of lead. Tetracyclohexyl 
lead reacts with hydrogen chloride or hydrogen bromide to give 

Pb and the simple alkyl derivatives give Pb X . R3 under 

\ 

the same conditions. Cyclohexyl-magnesium bromide and lead chlo- 
ride in ether react very smoothly. Tetracyclohexyl tin crystallizes in 
fine microscopic aggregate melting at 248° and is easily soluble in ben- 
zene, chloroform and carbon bisulfide; bromine reacts with it to give 
SnBr2(C6Hii)2, long well formed needles melting at 58°. Tiffeneau 
and Gannage ^^ prepared dicyclohexyl-mercury by the action of sodium 
amalgam on bromocyclohexane; the mercury derivative forms needles 
of a camphor-like odor, melting at 139°. Mercury derivatives of 

"Ber. kl, 3257 (1914). 

"J. Chem. Soc. Abs. MO (1), 472 (1921). 



288 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

methylcyclohexane were similarly prepared from 4-bromomethylcyclo- 
hexane. Derivatives of the type RHgCl were made from dicyclohexyl- 
mercury by the action of benzoyl chloride or arsenic trichloride. 

Some Simple Derivatives of Cyclohexane: An extensive review of 
the derivatives of cyclohexane is beyond the scope and purpose of the 
present volume but a brief description of some of the more important 
derivatives indicating the close parallelism in the chemistry of cyclo- 
hexane and normal hexane, and other examples of chemical behavior 
which are likely to prove of interest in connection with the chemical 
investigation of petroleum, are given. 

Cyclohexane is readily acted upon by dry chlorine, direct sunlight 

not being required. The monochloride, boiling-point 141.6°-142.6°, 

22° 
d -^ 0.9976, is also readily prepared by the action of concentrated 

hydrochloric acid or PCls on cyclohexanol. On treating with alkalies 
the chloride forms cyclohexene and when alcoholic caustic alkalies are 
employed a small proportion of cyclohexylethyl ether is formed; in fact, 
the behavior of the chloride closely parallels the behavior of the mono- 
chloron. hexanes. Like the monochloropentanes and monochloro- 
hexanes the cyclohexyl derivative is decomposed by passing over anhy- 
drous barium chloride or alumina at 350°-450°, cyclohexene being 
formed almost quantitatively.^* Another process for converting chloro- 
cyclohexane to cyclohexene describes passing the chloride over lime at 
350°-450° or over barium chloride at 300°-400°." Fortey ^« decom- 
posed the chloride by heating with quinoline and described the result- 

4° 
ing cyclohexene as boiling at 82.3° d — 0.8244, but Auwers ^° gives the 

15 6° 

following physical constants, boiling-point 83°-83.5° (760 mm.), d j, 

0.8143, nj) 1.44921, Mj-, 27.03 (calculated Mq 27.24). Cyclohexene 
cannot be made satisfactorily from cyclohexanol by heating with an- 
hydrous oxalic acid, the principal product being dicyclohexyl oxalate, 
but heating with potassium acid sulfate gives an 80 per cent yield of 
cyclohexene.'" A small proportion of cyclohexyl ether, boiling-point 
239°-240°, is also formed. The bromine and iodine derivatives are 
naturally more easily decomposed than the chlorides, but a double bond 
adjacent to the halogen stabilizes the substance as in the aliphatic se- 

^'Badische, ADilin n. Soda Fabr., J. Chem. Soc. Abe. WIS (1), 349. 

" Schmidt, Hochschwender & Eichler, Chem. Ais. 1917, 1885. 

^'J. Chem. 800. 73, 941 (1898). 

"Ann. ilO, 257 (1915). 

■» Willstatter & Hatt, Ber. i5, 1464 (1912). 



THE CYCLOHEXANE SERIES 



289 



ries. Usually the halogen derivatives have not been prepared from the 
hydrocarbon but from the alcohols. Thus cyclohexanol and concen- 
trated hydriodic acid yield cyclohexyl iodide and quinite yields the 
corresponding 1.4 dihalogen derivatives. 

When cyclohexane is chlorinated in the cold a mixture of chlorides 
is obtained. Two dichlorocyclohexanes are obtained, one boiling at 
105.4°-106.4° (50 mm.) and the other distilling at 112.4°-113.4° 
(50 mm.) ; the former on prolonged boiling with alcoholic caustic pot- 
ash yields a chlorocyclohexene. On distilling at atmospheric pressure 
the dichlorides decompose markedly. Continued chlorination yields 
tetrachlorocyclohexane, crystallizing from chloroform in long prisms 
melting at 173°." 

Cyclohexane is practically unacted upon by the usual nitrating 
mixture of nitric and sulfuric acids, but may be nitrated by heating in 
a sealed tube with dilute nitric acid according to the method discovered 
by Konowalow.^^ Its behavior in this respect is practically identical 
with that of n.hexane and the properties of the resulting nitrocyclo- 
hexane are quite different from the properties of nitrobenzene. On 
reduction with tin and hydrochloric acid, the corresponding amine is 
not formed but cyclohexanone or its condensation products are formed, 
evidently through the intermediate formation of the oxime of cyclo- 
hexanone, 




160 form 



oxime 



cyclohexanone 



Dinitro and trinitro derivatives of cyclohexane cannot be prepared by 
the nitration method noted above. Alkyl derivatives of cyclohexane, 
such as methyl or dimethylcyclohexane, containing a tertiary hydro- 
gen atom are much more easily nitrated by Konowalow's method, the 
nitro group replacing the tertiary hydrogen atom. Like primary and 
secondary nitro derivatives of the aliphatic series, nitrocyclohexane is 
soluble in alkalies, evidently forming salts of the iso form whose struc- 
ture is noted above. Nitro cyclohexane boils at 205.5°, d20° 1.0616. 



"Sabatier & Mailhe, Compt. rend, isn, 240 (1903). 
"Compt. rend. 121, 652 (1895). 



290 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Nametkin '^ states that the yield of nitrocyclohexane is increased by 
nitrating the hydrocarbon with about three parts by weight of alu- 
minum nitrate. Cyclohexane yields about 56 per cent of nitro- 
cyclohexane together with cyclohexanone and dinitrodicyclohexyl, 
CiaHaoCNO^)^ melting at 216.5°. 

Aminocyclohexane and other amino derivatives of the cyclohexanes 
differ markedly from the amines of the benzene hydrocarbons, par- 
ticularly in their behavior when treated with nitrous acid. As noted 
above aminocyclohexane is best prepared by reduction of the oxime 
of cyclohexanone in alkaline solution or by catalytic hydrogenation by 
the Sabatier and Senderens method. Heating cyclohexanone or similar 
ketones with ammonium formate and reduction of the resulting formyl 
derivative to the amine has also occasionally been employed,'* but re- 
duction of the oxime generally gives much better yields. In the case 
of tertiary nitro compounds, such as 1-nitro-l-methylcyclohexane, re- 
duction of the nitre group gives satisfactory yields since the tertiary 
nitro derivatives cannot rearrange to the iso forms with the resulting 
formation of oximes and ketones. 

The aminocyclohexanes yield comparatively stable nitrites when 
treated with nitrous acid and on heating their aqueous solutions de- 
composition takes place with diflBculty yielding the corresponding alco- 
hol (yields usually very poor), and decomposition also proceeds in 
another iranner with the formation of ammonia and unsaturated hy- 
drocarbons. The latter reaction can be modified so as to serve admir- 
ably for the preparation of unsaturated hydrocarbons, particularly in 
cases where the resulting imsaturated hydrocarbon is easily rearranged 
or polymerized. For this purpose the amine is subjected to exhaustive 
methylation and the resulting alkylated ammonium hydroxide decom- 
posed by gentle heating, a method mentioned in connection with cyclo- 
butene and which warrants more extensive applications in research. 
Decomposition of the phosphates of amines of this type by heating has 
also been employed for converting the amines to unsaturated hydro- 
carbons.'' 

The method of reducing the oximes to amines has been employed 
for the preparation of the 1.3-diamine and 1.4-diamine, the oximes 
being prepared from the corresponding ketones. The 1 . 2-diamine has 
been prepared from anthranilic acid which can be best reduced by the 

"J. Runs. Phya.-Chem. Soc. i2, 581 (1910). 
"Leuchart & Bach, Ber. m, 104 (1887). 
"Harries, Ber. S^, 300 (1901). 



THE CYCLOHEXANE SERIES 



291 



method of Ipatiev or by sodium and amyl alcohol.'* The amide of the 
reduced acid may then be converted to the diamine in the usual manner 
by bromine and alkali.'' 

The cyclohexadienes have been of considerable interest on account 
of their close relation to benzene. A cyclohexadiene boiling at 84°-86° 
was first made by Baeyer '' and the same laborious methods of prepa- 
ration were later employed by Crossley.'" A product evidently identi- 
cal with Baeyer's and having the same boiling-point was made by 
Markownikow by decomposing chlorinated cyclohexane isolated from 
Russian petroleum.^" Fortey reported a cyclohexadiene boiling at 81°- 
82° *^ and Harries and Antoni *^ obtained a product of the same boiling- 
point, 81.5°, by the decomposition of the phosphate of 1.4-diamino- 
cyclohexane. From 1 . 2-dibromocyclohexane Crossley ^' also obtained 
the low-boiling product and, from its method of preparation and the 
fact that oxidation by nitric acid yielded oxalic and succinic acids, con- 
cluded that the low-boiling product was 1 . 3-cyclohexadiene. 



CH^ CH, CO,H. 

I I + I ' 

CO^H CO^H CO^H. 



Zelinsky and Gorsky ** obtained the» high-boiling hydrocarbon from 
1.4 dibromocyclohexane and the low-boiling one from 1.2 dibromo- 
cyclohexane. Both hydrocarbons form different and characteristic di- 
bromides and tetrabromides. 



H^^Br 



H-^"-B. 






A^* cyclohexadiene 
B.-P. 85°-86° 



"Einhorn & Meyerburg, ^er. 87, 2466 (1894). 

"Binhorn & Bull, Ber. 29, 964 (1896) ; Ann. 295, 187. 

"Ber. 25, 1840 (1892). 

"J. Ohem. 8oc. 85, 1410 (1904). 

"Ann. sm, 30 (1898). 

"J. Ohem. Boc. n, 945 (1898). 

"Ann. S28, 93, 106 (1903). 

"Loo. cit. 

*^Ber. il. 2479 (1908). 



292 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 




^\^ 



A^-^ cyclohexadiene 
B.-P 81.5° 



Although the evidence of the existence of the two isomeric hexa- 
dienes is quite clear some doubt as to their constitution has been ex- 
pressed on account of the fact that neither of the hexadienes shows the 
exaltation of the molecular refraction which two conjugated double 
bonds were supposed always to show. However, Auwers has shown 
that cyclopentadiene, which must contain conjugated double bonds, and 
cycloheptadiene, containing conjugated double bonds, do not show any 
exaltation and the conjugated cyclic trienes show only very slight ex- 
altation.^' The agreement with the calculated value of A^- ^-cyclo- 
hexadiene is in fact within the experimental error, if we accept the 
more recent determinations of Harries ^^ and of Willstatter and Hatt.*' 



EMa. 

Harries 0.05 

"Willstatter and Hatt 0.00 



EM 



D 
0.09 
0.02 



A similar discrepancy between the observed refractivity and the 
expected exalted value due to conjugation of double bonds confused 
for a time the question of th§ constitution of the substituted cyclo- 
hexadiene, a-terpinene (q. v.). The determination of the constitution 
of such hydrocarbons has been particularly difficult on account of the 
ease with which the double bonds shift their positions. Thus the prepa- 
ration of pure a- or y-terpinene, a- or p-phellandrene, and terpino- 
lene is practically impossible. 

The cyclohexadienes show a very marked tendency to oxidize to 
benzene (or its homologues), for example, the oxidation of the ter- 
pinenes to cymene. Also cyclohexadiene (probably a mixture of the 
two isomers) is converted to benzene by dehydrogenation in the pres- 
ence of nickel at the remarkably low temperature of 180°.*^ Dilute 
acids very frequently cause shifting of double bonds when a more 
stable substance can result, and a double bond in a side chain fre- 
quently shifts to the ring. Thus 2-phenyl and 2-propyl-A^-'-8- (»)-men- 

*» For a fuller discussion of the refractivity of cyclic and acyclic hydrocarbons 
see the chapter on physical properties. 
"Ber. iS, 809 (1912). 
" Ber. iS, 1647 (1912). 
"Boeseken, Rec. trav. chim. 37, 255 (1918). 



THE CYCLOHEXANE SERIES 293 

thatriene are quickly converted to the isomeric benzene derivatives by 
warming with 3 per cent hydrochloric acid.'*^ 

Conjugated dienes react with concentrated sulfuric acid with al- 
most explosive violence, with tar formation and reduction of the acid, 
a behavior frequently noted on refining crude benzene containing cyclo- 
pentadiene and cyclohexadiene and this energetic action is particu- 
larly marked when the crude benzene has been manufactured from 
oil, as in Pintsch gas "hydrocarbon" or carburetted water gas tar. Un- 
der the same conditions that amylene and such simple olefines give 
good yields of the alcohols (i. e., by treating with ordinary sulfuric 
acid in the cold and diluting with water) the conjugated diolefines 
yield only tar. 

Cyclohexanol: This alcohol promises to become a common com- 
mercial product °° as a result of the development of methods of cat- 
alytic hydrogenatioR, being readily prepared from phenol. Cyclohex- 

37° 
anol has a camphor-like odor, boils at 160.9°, melts at 23°, d -j^ 

0.9397, n-p) 1. 46055. '^^ It is sparingly soluble in water but is hygro- 
scopic, a little water lowering the freezing-point, a eutectic point being 
noted at — 47.4°, the liquid containing 4.97 per cent of water at that 
point.°^ The acetate resembles amyl acetate and while it has no very 
marked physiological action, the narcotic action of the vapors is about 
three times greater than the same property of amyl acetate.'^^ The 
naphthylurethane =* melts at 139°-140°. 

When phenol is reduced with hydrogen over active nickel at 160°- 
170°, the nickel having been reduced from the oxide at 300°, the prod- 
uct is chiefly cyclohexanol together with a little unchanged phenol and 
a little cyclohexanone. Holleman ^° removed the cyclohexanone by 
condensing it with benzaldehyde in the presence of alkali. When cyclo- 
hexanol is passed over copper, with a little air, at 280° cyclohexanone 

"Klages, Ber. 1,0, 2360 (190T). 

"■ The use of cyclohexanol In soap is said to enable one to Incorporate solvents 
such as benzene, tetraline, chlorinated solvents and the like in the soap and also 
facilitates the manufacture of soaps containing phenolic insecticides. Its use as a 
solvent for rubber In reclaiming rubber is mentioned in German Patent 366,146. Like 
fusel oil and amyl acetate, cyclohexanol and its acetate are of value as solvents for 
nitro cellulose, such solutions being capable of considerable dilution with the common 
hydrocarbon solvents, gasoline, benzene, etc. The use of cyclohexanol and cyclo- 
hexanone in the manufacture of celluloid has been patented by Rascbig, German Pat. 
174,914 (1905). 

"Auwers, Ann. ilO, 257 (1915). 

'^Forcrand, Compt. rend. 156, 118 (1912). 

" Lehmaun, Chem. Ala. MIS, 2432. 

" Neuberg, Bioch. Z. 87, 339. 

"Rec. trav. chim. U, 19 (1905) ; Brochet [/. Soc. Chem. Ind. S2, 1031 (1913)] 
used nickel and hydrogen at 120°-180° and 10 to 15 kilograms per sq. cm. pressure. 



294 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

is produced in good yields. Sabatier and Senderens °* reduced phenol 
at a higher temperature and obtained a mixture of cyclohexanone and 
cyclohexanol, from which they prepared cyclohexanol by passing again 
over the catalyst with hydrogen at a lower temperature, 140°-150°, 
and prepared nearly pure cyclohexanone by passing the mixture over 
copper at 330°. Cyclohexanol is readily oxidized to cyclohexanone by 
chromic acid, under the same conditions that aliphatic secondary alco- 
hols are oxidized to the corresponding ketones. 

Cyclohexane-1 .2-diol, melting-point 99°-100°, is formed when 
cyclohexene is oxidized by cold dilute permanganate in the usual man- 
ner. Cyclohexane-1 .S-diol," melting-point 65°, is produced by the 
catalytic hydrogenation of resorcinol in the presence of nickel at 
130°. It is easily soluble in water and alcohol, does not reduce Feh- 
lings' solution or give a color with ferric chloride. Cyclohexane-1 .2.3- 
triol was also obtained by the catalytic hydrogentition of pyrogallol, 
the triol forming very hygroscopic crystals melting at 67°. Cyclo- 
hexane-1. 3. 5-diol, made by reducing phloroglucine with sodiiun amal- 
gam, melts at 184°. Cyclohexane-1 .4-diol, also called quinite can be 
obtained by catalytic hydrogenation of hydroquinone and was also 
prepared by Baeyer by reducing cyclohexane-1. 4-dione with sodium 
amalgam. It was named quinite on account of its relation to benzo- 
quinone, which it yields when oxidized by chromic acid. Two other 
hydroxyl derivatives of cyclohexane may be mentioned on account of 
their interest to biochemistry, i. e., quercite, cyclohexane-1. 2. 3.4.5- 
pentol, and inosite, cyclohexane-1 .2.3.4.5. 6-hexol. Quercite is known 
in two forms [a]-^ .+ 24.16°, melting-point 235°, and [a]^ — 73.9°, 
melting-point 174°. The chemical behavior of quercite and inosite is 
very closely parallel to the behavior of sorbite, rhamnite, etc. Both 
substances have been known for a long time and their chief interest 
in connection with a discussion of the chemistry of the hydrocarbons 
is that ring closing makes such slight differences in their chemical 
properties as compared with the alcohols of the methyl pentose and 
hexose series. Quercite yields a pentacetyl derivative melting at 125°, 
an explosive pentanitrate and an amorphous pentaphenyl carbamate. 
Inosite yields a hexacetate melting at 212° and a very explosive hex- 
anitrate. A monomethyl ether of inosite has been reported in a caout- 
chouc (gutta-percha ?) from Borneo and a dimethyl ether in another 

"Oompt. rend. W, 1025 (1908). 

" Sabatier & Mailbe, Compt. rend. US. 1193 (1908). 



THE CYCLOHEXANE SERIES 



295 



specimen of caoutchouc.^' The resin of the California pine, Pimts 
lambertiana, also contains a monomethyl ether of d-inosite.°' This 
ether, pinite, has been found in other plant secretions, tastes very 
sweet, melts at 186°, and following the general behavior of such ethers, 
is readily split by warming with concentrated hydriodic acid, to methyl 
iodide and the alcohol. 

The Physical Properties and Literature References op the Cyclohbxanols 



Name B.-P. 

Cyclohexanol 160.9° 



Methylcyclohexanol- ( 1 ) 

Methylcyclohexaiiol-(2) . . . 

Methylcyclohexanol-(3) . . . 

Methylcyclohexanol-(4) . . . 
1.3-Dimethylcyclohexanol-(l) . . 
1.4-Dimethyloyclohexanol-(1) . . 
2.2-Dimethylcyclohexanol-(l) . . 
3 3-Dimethylcyclohexanol-(l) . . 
4.4-Dimethylcyclohexanol-(l) . . 
2.4-Dimethylcyclohexanol-(l) . . 
2.5-Dimethylcyclohexanol-(l) . . 
2.6-Dimethylcyclohexanol-(l) . . 
3.4-Dimethylcyclohexanol-(l) . . 
3.5-Dimethylcyclohexanol-(l) . . 
1 .3.5-Trimethylcyclohexanol- ( 1 ) 
3.3.5-TrimethylcyclohexaiLol- (1 ) 
2.2.5-Trimethylcyclohexanol- ( 1 ) 
226 ,6-Tetramethylcy clohexanol- 

(1) 

2.2.5.5-Tetramethylcyclohexanol- 

(1) 



'-158. 



156. 

168. ' 
174. ' 
173. ' 

169. ' 
170. 
177. ' 
185. ' 
186. 
176.5' 
178.5 
174,5* 
189. 
187. ' 
181. ' 
200. ' 
187. ' 



195. °-197. 



-175.5° 



20° 



202. 



d4° 


nD 


References 


0.949 


1.4659 


1 


0.924 


1.4585 


1 


0.928 


1.463 


2 


0.917 


1.458 


3 


0.919 


1.458 


4 


0.903 


1.455 


5 


0.909 


1.457 


5,6 


0.922 


1.464 


7 


0.909 


1.459 


8 


0.925 


1.463 


9 


0.908 


1.4562 


10 


0.904 


1.4532 


10 


0.924 


1.4628 


11 


0.904 


1.4562 


10 


0.898 


1.453 


12 


0.886 


1.453 


13 


0.897 


1.453 


12 


0.900 


1.459 


14 


0.897 


1.4537 


15 


0.902 


1.462 


16 



5 
6 

7 
8 

9 
10 
11 
12 
13 
14 
15 
16 



Zelinsky, Ber. 34, 2800 (1901) ; Auwers, Ann. 410, 309 (1915). 
Wallach, Ann. 329, 375 (1903) ; Murat, Chem. Zentr. 1909 (2), 851. 
Zelinsky, Ber. SO, 1534 (1897); Haller and March, Chem. Zentr. 1906 (2), 

325; Sabatier and Mailhe, Chem. Zentr. 1906 (1), 742. 
Sabatier and Mailhe, Chem. Zentr. 1907 (1), 1096; Auwers, Ann. 410, 309 

(1915). 
Sabatier and Mailhe, Chem. Zentr. 1906 (2), 483. 
Wallach, Ann. 396, 266 (1913). 

Auwers and Lange, Ann. 401, 319 (1913); Meerwein, Ann. 405, 144 (1914). 
Perkin, St., J. Chem. Soc. 87, 1493 (1905); Auwers and Lange, Ann. 401, 

314 (1913). 
Auwers and Lange, loc cit. 

Sabatier and Mailhe, Chem. Zentr. 1906 (1), 1248. 
Haller, Chem. Zentr. 1913 (2), 1144. 

Knoevenagel, Ann. 297, 182 (1897); Auwers, Ann. 410, 311 (1915). 
Wallach and Schlubach, Ann. 396, 284 (1913). 
Wallach, Ann. 329, 87 (1903) ; Auwers, Ber. 41, 1814 (1908). 
Haller, Chem. Zentr. 1913 (2), 41. 
Auwers and Lange, Ann. 409, 178 (1915). 



»s Flint & ToUens, Ann. 272, 288 (1893). 
"Wiley, J. Am. Chem. Soo. IS, 228 (1891). 



296 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

A great many alkyl derivatives of cyclohexanol are known, the 
simpler ones being readily made by catalytic hydrogenation of the 
cresols, by the Grignard reaction on cyclohexanone and other well- 
known methods. As in the aliphatic series the secondary alcohols are 
not easily decomposed to unsaturated hydrocarbons but tertiary alco- 
hols of the type 

OH 



yield unsaturated hydrocarbons very readily. 

Cyclohexanone: On account of the very great value of this ke- 
tone as a material for the synthesis of a very large number and va- 
riety of hydrocarbons, it will be briefly described. Its best method of 
preparation has already been described in connection with cyclo- 
hexanol. Its chemical behavior closely parallels that of the aliphatic 

ketones. Pure cyclohexanone boils at 156.6°-156.8° d-^^0.9503, n^^ 

1.45261.^° It may be characterized by the phenylhydrazone melt- 
ing at 74°-77° and the condensation products with benzaldehyde 
CeHsCH = (CeHgO) melting at 53° and the dibenzylidene compound 
CeH^CH = (CeHeO) = CH.CeH, melting at 117°." The ketone, like 
cyclopentanone, is condensed by sodium ethylate or by gaseous hydro- 
gen chloride to cyclohexylidenecyclohexanone and a dicyclohexylidene- 
cyclohexanone. The ring is not easily broken but in direct sunlight 
in dilute alcohol solution capronic acid and A' hexene aldehyde are 
formed, and the oxime is converted by concentrated sulfuric acid to 
the iso-oxime, or e-caprolactam. With an excess of bromine in the 
cold it yields a tetrabromide melting at 119°, but when brominated hot 
the chief product is 2 . 4 . G-tribromophenol."^ 

Methylcyclohexane occurs in Russian "^ and Galician ^* petroleum. 
Galician petroleum appears to be midway between Russian petroleum 
and oils of the Pennsylvania type. The presence of methylcyclohexane 
in Russian petroleum was regarded as "probable" by Young. It also 

•oAuwers, Ann. IflO, 257 (1915). 
"' Wallach, Qoettingen Nachr. 1907, 402 ; Ber. iO, 71. 
"=Bodroux & Taboury, Compt. rend, m, 1509 (1912). 

" Milkowskl, J. Buas. Phya.-Chem. Soo. 17, 37 (1885) ; Zellnsky, Ber. SO, 1532 
(1897). 

"Skowronski, Chem. Ais. 19g0, 3523. 



THE CYCLOHEXANE SERIES 297 

occurs in rosin spirit*' and can readily be prepared by the catalytic 
hydrogenation of toluene. Reduction of cycloheptanol by heating with 
concentrated hydriodic acid causes a rearrangement of the carbon 
structure giving methyl cyclohexane as the reduction product. 

When treated with bromine and aluminum bromide the principal 
product is pentabromotoluene, melting at 282°, and this fact can be 
used for detecting the presence of methyl cyclohexane in gasoline, 
after proper fractional distillation. When methylcyclohexane is ni- 
trated by Konowalow's method using nitric acid, Sp. Gr. 1.20, the 
yield of nitro derivatives is about 58 per cent, but Nametkin°° re- 
ports that nitration by aluminum nitrate gives about 72 per cent of 
nitrated products. The tertiary nitro derivative may be separated 
from the primary and secondary derivatives by the solubility of the 
latter two types in alkali. 1 . 1-Nitromethylcyclohexane is a liquid dis- 
tilling at 109-° 110° (40 mm.), d-^1.0547 and may be reduced by tin 

and hydrochloric acid to the amine boiling-point, 143° (744 mm.). 

0° 

The 1.3-nitromethylcyclohexane distills at 119°-120° (40 mm.), d-jj- 

1.0547; cyclohexylnitromethane, CsHii.CHaNOa, is also formed. Oxi- 
dation of methylcyclohexane by nitric acid yields a mixture of adipic, 
succinic, oxalic, glutaric and pyrotartaric acids. 

The chlorination of methylcyclohexane yields, of the monochlo- 
rides, about 60 per cent l-methyl-3-ehlorocyclohexane and about 40 
per cent of the 1 . 2-derivative. This was shown by forming the mag- 
nesium derivatives with the monochlorides passing oxygen into the 
ethereal Grignard solution, and examining the resulting alcohols. 
Cyclohexylmethyl chloride, 0^11,1. CHjCl, made from the correspond- 
ing carbinol, boils at 166° (760 mm.) without appreciable decompo- 
sition; 2-chloromethylcyclohexane boils at 156° with slight decompo- 
sition; 3-chloromethylcyclohexane distills at 157° and 4-chloromethyl- 
cyclohexane distills at 158°, also decomposing appreciably." 

Methyl Cyclohexenes : Of the three methyl cyclohexenes A^-methyl 
cyclohexene is the most stable, the other two isomers being readily 
converted to the A^ hydrocarbon by heating with dilute acids. The A^ 
hydrocarbon is also present in the mixture of hydrocarbons obtained 
by decomposing methylcyclohexanol- (3) or methylcyclohexanol-(4) 
with phosphorus pentoxide or zinc chloride. Decomposition of 1 . 1 or 

"Ann. cUm. phys. (6) 1, 229 (1884). 

"J. Russ. Phya.-Ohem. 8oc. iB, 691 (1910). 

" Sabatier & Mailhe, Compt. rend. UO. 840 (1905), 



298 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



1 . 2-methylcyclohexanol yields the A^ hydrocarbon. Wallach *^ pre- 
pared it by treating cyclohexanone with methyl-magnesium iodide and 
decomposing the tertiary alcohol by zinc chloride. Its boiling-point, 
111°-112°, is several degrees higher than the isomeric methenecyclo- 
hexane prepared by Wallach by distilling and decomposing cyclo- 
hexene acetic acid. The A^ hydrocarbon yields a glycol, by per- 
manganate oxidation, melting at 67°. When 1.2 methylcyclohexanol 
is decomposed by Ipatiev's method, passing the vapors over' heated 
alumina at 350°, a mixture of methylcyclohexenes, distilling from 
96°-100°, is formed, but when a mixture of alumina and copper oxide 
is used, the reaction takes place smoothly at 240° and the product is 
nearly pure A^-methylcyclohexene.''° By condensing cyclohexanone 
and bromoacetic ester in the presence of zinc, Wallach '" made cyclo- 
hexanolacetic acid which on decomposing with bisulfate or P2O5 yields 
mainly A^-cyclohexene-acetic acid but by heating with acetic anhy- 
dride yields mainly A^O-cyclohexeneacetic acid, a reaction frequently 
employed for the synthesis of methene derivatives in the cyclohexane 
and cyclopentane series. Distillation of the unsaturated acids yields 
the hydrocarbons, as indicated below, 



.=CHCO^H 




=iCH +C0, 



Methenecyclohexane''^ boils at 103°, dig 0.8020, n-p 1.4499. It 
readily absorbs hydrogen chloride, forming an unstable chloride boiling 

•'Ann. 3S9, 287 (1908). 

"Ber. iS, 3383 (1910) ; J. Ruas. Phva.-Chem. 8oc. U, 1675 (1913). 

^'Ann. S5S, 288 (1906). . 

" Wallach, Ann. S65, 262 (1909) ; Favorsky & Borgmann, Ber. 40, 4863. 



THE CYCLOHEXANE SERIES 



299 



at 151°-152°. It is easily converted to A^-methylcyclohexene by alco- 
holic sulfuric acid and on hydrating by dilute sulfuric acid yields the 
tertiary alcohol 1 . 1-methylcyclohexanol. Permanganate oxidation 
yields cyclohexanone and a glycol melting at 67°-77°. Its nitroso- 
chloride may be converted into the nitrolpiperidide, useful for identi- 
fication or HCl may be removed by heating with sodium acetate in 
acetic acid to give an aldoxime (a very general reaction of nitroso- 
chlorides, giving an aldoxime or ketoxime). Hydrolysis of the 
aldoxime yields A^-cyclohexene aldehyde, an aldehyde having an odor 
greatly resembling benzaldehyde. Since these reactions are widely 
applicable and have in fact been frequently employed, they are noted 
here, 



CH, 



CH=NOH 
CI 



CH=NOI) 




CHO 




The glycol is readily converted to the saturated cyclohexyl aldehyde 
by the action of dilute acids, also a very general reaction, and having 
its parallel in the behavior of the 1 . 2-glycols of the aliphatic series 



CHjOH 
OH 



CHO 



-> 



Unlike benzaldehyde, cyclohexyl aldehyde polymerizes very easily to 
the dimeride (C7Hi20)2 and with acids the substance (trimeride ?) 
(CjHi20)3 is formed. 

^'-Methylcyclohexene, boiling-point 103°, may be obtained by 
heating and decomposing the acid phthalic ester or methyl xantho- 
genate of methylcyclohexanol(3) or by decomposing the iodide by 
alcoholic caustic potash or dimethyl aniline. From optically active 
methylcyclohexanol (3) Zelinsky " obtained an optically active hydro- 
carbon by decomposing the iodide. The hydrocarbon, the constitu- 

"Ber. 35, 2488 (1902). 



300 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

tion of which was not proven, varied according to the method of 
preparation, the hydrocarbon obtained by caustic potash having the 
highest rotation, 

(1) by alcoholic KOH,— boiling-point 103°-103.5°, [a]j) + 81.4° 

(2) by dimethyl aniline, boiling-point 105°-106 °, [ajp -f- 48.3° 

When A*-methylcyclohexene is treated with sulfuric acid (1 volume 
water to two volumes of acid) the principal product is the dimeride, 
C14H24, and more dilute acid (1:1 by volume) converts it to a mixture 
of the A^ and A^ isomers and alcohols, among which methylcyclohex- 
anol(3) were identified." 

1.1 Dimethylcyclohexane: This hydrocarbon has been synthesized 
by Crossley and Renouf,'* from 1 . 1-dimethyldihydroresorcin. Zelin- 
sky and Lepesckin'^ had prepared a hydrocarbon which they con- 
sidered to be 1 . 1-dimethylcyclohexane from laurolene and isolaurolene 
but the work of Crossley and Renouf shows that Zelinsky's conclusions 
were incorrect. Crossley and Renouf treated 1 . 1-dimethylcyclohex- 
anol(3) with hydrogen bromide in acetic acid and reduced the bromide 
with zinc dust in acetic acid to 1 . 1-dimethylcyclohexane. The hydro- 
carbon is stable to bromine and permanganate in the cold and is slowly 
oxidized by fuming nitric acid to P|3-dimethyladipic acid. When 
the above bromide (3) is_ treated with alcoholic caustic potash 
1 .l-dimethyl-&L^-cyclohexene is formed, apparently not contaminated 
with the A^-isomeride. The unsaturated hydrocarbon has a turpentine 
like odor and yields P|3-dimethyladipic acid on oxidation by perman- 
ganate. The physical properties of the two hydrocarbons are as 
follows, 

B.-P. dl 



15° 

1 . 1-dimethylcyclohexane 102° 0.7864 

1 . l-dimethyl-A'-cyclohexene 117°-117.5° 0.8040 

17 

Zelinsky's hydrocarbon boils at 111.5°-114°, d-^ 0.7686, and on oxida- 
tion does not yield (5p-dimethyladipic acid. The physical properties 
of 1.1 -dimethylcyclohexane prepared from 1 . 1-dimethylcyclohexane- 
3-one, by reduction to the alcohol, and conversion of the latter to the 

" Markownikow, J. Russ. Phys.-Ohem. Boo. SS, 1049 (1903). 

"J'. OMm. Boo. 87, 1487 (1905) ; 89, 27 (1906). 

'^Ann. SIS. 303 (1901) ; J. Buss. Phys.-Ohem. Boo. IS, 549 (1901). 



THE CYCLOHEXANE SERIES 301 

unsaturated hydrocarbon followed by catalytic hydrogenation were, 

90° 90° 

boiling-point 118.5°, d-^^0.7825, n =g-1.4289." 

Zelinsky and Lepeschkin '''' later confirmed the work of Crossley and 
Renouf by the synthesis of 1 . 1-dimethylcyclohexane in another man- 
ner (from p-methyl-A/3-heptone-^-one) and noted the following: boil- 

16° 16° 

ing-point 119-2°-119.7°, d -^ 0.7843, n_ 1.4320. When 1. 1-dime- 
thylcyclohexane is brominated in the presence of aluminum bromide 
one of the methyl groups goes to the para position, resulting in a 
para-xylene derivative. 

Auwers'* has prepared a series of methyl derivatives of cyclo- 
hexane. The method of preparation most frequently employed was 
the catalytic hydrogenation of phenols, conversion of the resulting 
secondary alcohols to iodides and reduction of the latter by zinc dust 
and acetic acid. Also tertiary alcohols, formed by treating cyclo- 
hexanone derivatives with magnesimn methyl iodide, were converted 
to the corresponding chlorides by the action of phosphorus trichloride 
and the resulting chlorides reduced to the saturated hydrocarbon by 
sodium in moist ether. A summary of the physical properties of the 
methyl derivatives of cyclohexane, as determined by Auwers is given 
in the following table. 



Name 


Alk.^ 

:ane 
;ane 


'L Derivatives 
I. Methyl I 
Structure 


OP Cyclohej 
)ebivatives. 


cane: 

B.-P.* 
80.5° 
101. " 

120. ° 
123. " 


, 20° 

0.778 
0.771 

0.781 
0.779 


m° 


Cyclohexane 


/ 


1.427 


Methylcyclohexane 


/ 

\ 


^CHa 


1.423 






-S.CH, 




1 .1-dimethylcy clohej 


d 


1.430 






X;Hi 

CU. 

1 




1 .2-dimethylcyclohe3 


/ 
\ 


^CH, 


1.429 



• The above data show that the density decreases as the methyl groups are seoa- 
rated more widely from each other. 

"Gadaskl & Ssorokina, Chem. Ztg. srt, 725 (1913). 
"J. Rusa. Phys.-Chem. Soc. MS, 613 (1913). 
■"Ann. J,iO, 88 (1919). 



302 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

I ^ 

U-dimethyloyclohexane" / ^ CH. 119. ° 0.771 1.425 

1.4-dimethylcyclohexane CHjr-< ^ ^ CH, 120. " 0.769 1.424 

CH, 



V 138. ° 0.790 1.436 



CH, 

I 



15.4-trimethylcyelohexane CH^-^ ^CHa 140. ° 0.778 1.429 

CHj CHa 

I I 

ia.3-trimethylcycloliexaiie"' <(~~\-C^ 149.6°-150° .. 



CH, 

1.3.5-trimethylcyclohexane / )>— CH, 138. ° 0.772 1.429 

CH. 
CH. 

1.2.4.5-tetramethylcyclohex- CH_^^ V-CH, 161. " 0.785 1.434 

CH, 

The boiling-points and densities of otiier alkyl derivatives of 
cyclohexane are given in tlie following table. 

Alkyl, Derivatives of Cyclohexane II. 

D D r. •. ^0° Rejer- 
Name B.-P. Density,-^ ^^^^ 

Ethylcyclohexane 130° 0.7772 1 

1.2-Methylethylcyclohexane 151° 0.784 2 

n.Propylcyclohexane 156° 0.7865 3 

Tertiarybutylcyclohexane 166°-167° O.8305-73- 4 

l.a-Methylethylcyclohexane 145°-146° 0.8320 5 

1.3-Methylpropyloyclohexane 164°-165° 5 

21° 

15-Methylisopropylcyclohexaiie [o-menthane] ... 171° 0.8135-jr5- 6 

24° 
1.3-Methylisopropylcyclohexane [m-menthane] . . 166°-167° 0.7965 -jto- 6 



0° 

"Zelinsky, Ber. 35, 2677 (1902), gives the foUowlng, boiling-point 119.5-120°, d- 



26° 
4° 

0.7661. Zellnsky prepared tlie hydrocarbon by converting 1.3-dlmethyl cyclohexanol (1) 
to the Iodide and reducing It with zinc in acetic acid. 
»»Treppmann & KroUpfelffer, Ber. ^8, 1226 (1915). 



THE CYCLOHEXANE SERIES SO^ 

25° 
1.4-Methylisopropylcyclohexane[p-meiithane] ... 167°-168° 0.8028-^ 6 

2-Cyclohexyl-2-methylbutane 

CeHu.C(CH3)sC2Ho 191°-192'' 0.8226^ 4 

2-Qyclohexyl-2-methylpeiitane 206°-207° 0.8372^ 4 

3-Cyclo}iexyl-3-methylpentane 207°-208° 0.8310-^ 4 

3-Cyclohexyl-3-ethylpentane 222°-223° 0.8388^ 4 

2-Cyclohexyl-2.4-dimethylpentane 220°-221° 0.8304^ 4 

3-Cyclohexyl-3-methyIhexane 224°-226° 0.8406^ 4 

17° 
l-Methyl-2-isoamylcyclohexaiie 204° 0.812-j^ 7 

1 Sabatier and Senderens, Compt. rend. 132, 210, 556 (1901). 

2 Murat, Ann. chim. phys. (8) 16, 108 (1909). 

3 Kursanoff, Ber. S4, 2035. 

4 Halse, J. prakt. Chem. (2) 92, 40 (1915). The hydrocarbons described by 

Halse were made by Willstatter's method of catalytic hydrogenation. 

5 Mailhe and Murat, Bull. soc. chim. 7, 1083 (1910). Zelinsky, Ber. 35, 2677 

(1902), gives the boiling-point 148°-149°, ^^ 0.7896. 

6 Sabatier and Murat, Compt. rend. 156, 184. 

7 Murat, Ann. chim. (8) 16, 108 (1909). 

Of the hydrocarbons noted in the above tables, cyclohexane, methyl- 
cyclohexane, 1 . 3-dimethylcyclohexane and 1 . 3 . 4-trimethylcyclo- 
hexane have been reported in the lighter fractions of Russian petro- 
leum, and the methyl, propyl, 1.3-dimethyl and 1.4-dimethyl 
derivatives have been reported in rosin oil. The method of identify- 
ing alkyl cyclohexanes by brominating in the presence of aluminum 
bromide to benzene derivatives which are supposed to retain the alkyl 
groups in the same relative positions as they occurred in the original 
cyclohexane hydrocarbon, is open to the objection that profound 
alteration of the carbon structure of the hydrocarbon has frequently 
been observed in the presence of aluminum bromide; thus 1.1-dime- 
thylcyclohexane gives a bromide derivative of para-xyhne. The same 
objection could be made to an attempt to convert the alkyl cyclohexane 
to the corresponding alkyl benzenes by dehydrogenation over nickel at 
about 300°. In view of the extreme difficulty of separating such 
hydrocarbons from petroleum by fractional distillation, to which diffi- 
culty Young has called attention, and the equally great difficulties and 
uncertainties of identifying them by chemical means (conversion to 
benzene derivatives or oxidation to known acids, etc.), it is quite 



304 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

probable that many of the cyclic hydrocarbons reported to have been 
identified in Russian petroleum have been so reported on faulty or 
insufficient evidence. 

Although a fair number of alkyl derivatives of cyclohexane are 
known, very little is known of their chemical behavior; for example, 
to concentrated sulfm-ic acid, nitric acid, chromic acid and the like. 
Even in the case of the menthanes, it is not known in what positions 
bromine enters on bromination and whether or not the tertiary hydro- 
gen atoms are reactive to sulfuric acid or are easily oxidized. In view 
of the very large losses which result on treating petroleum distillates 
with sulfuric acid, it would be desirable to know whether the different 
types of substituted cyclohexanes, bicyclic and polycyclic hydrocar- 
bons of different types, saturated in the sense that no double bonds 
are present, are resistant to air oxidation, resinification, destruction 
by concentrated sulfuric acid, etc. 

The Substituted Cyclohexenes follow very generally the chemical 
behavior noted in the so-called terpene series. Only in comparatively 
recent years has it been realized that the chemistry of these hydro- 
carbons occurring in nature cannot be dissociated in any way from 
the chemistry of the simple derivatives of cyclopentane, cyclohexane 
and cycloheptane. The boiling points, densities and refractive indices 
of a number of unsaturated hydrocarbons of this series are given in 
the following table. 



THE CYCLOHEXANE SERIES 



305 



•-C N CO Tjl U5 



oi -^ fO 

03 CO oS 

^ ^ 3i 



^ 






El 

15 






j5r^ sp 






CD o 






I 

o 

T-H 

o 



CO 

T 





55 


o 





^ 


^' 









/\ ^ 



o o o 

AX « 



t4 



\/ \y\/ 



.^ g_,/\ g_/\_g 



\/ \/ 



"Q- 



;§ 



s 
^ 



«j 



i 

(U 



p 



0) 


(U 










M 




S 




^ 


,f^ 


o 




•3 


•3 


!^ 


h 



<u 



I 



I 



•§ 



< -H 



>> 


>> 


ja 


ja 


53 


-fj 


a 


OJ 


a 


a 




^ 


<^ 


c4 



306 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



09 r> t» M cq CI 



^ 
^ 



I i 



I 



o 




g°^ 



























lO t- 


15 








O t^ 




CO 


t^ 


00 


oq aj 


s 


o 


o 


o 


o o 



I 



05 
I 



?3 






1-1 '^ 



is 



to 



O3?:^■oo 




<U 03 

(N ^ !>• en ^ ^H (O 

•^^ OJ _S 2 W tH 03 



-hNMtJI USCOt-. 










o 




a 


s 




1 
-3 


1 

•3 


hexene 
yclohexe 




^ 


& 


■i -' 


_o 


o 


i 


& 


^ -? 


"o 


O 


C3 


o ^ 


>. 


>. 


Oi 


"! 


,' >> 


J? 

1 


< 


a 

i 


;1 

CD 

a 


.9 1 










5 "^ 

»0 tH 


«4 


■^ 


CO 


<fi ci 



THE CYCLOHEXANE SERIES 307 

Wallach ^'^ tabulates the physical properties of a series of cyclo- 
hexane derivatives each of which contains a semicyclic double bond, 
as follows, 02^ 

Boiling-point 102.° 123.°-124.° 122.M23'' 

d 0.8025 0.798 0.7925 

Mj) 32.15 36.95 36.93 

Md (calc.) 31.83 36.43 36.43 

CH. 
I 
<( ^=CH.CH, <^ ^CH.CHa CHr-<^~\=CH.CH, 

Boiling-point .... 137.°-138.° "l53.° 156." 

d 0.823 0.813 0.8125 

M-Q 36.82 41.65 41.65 

Md (calc.) 36.43 41.03 41.03 

CH» 

I 

/ N=CH.aH. <( >=CH.C2H5 CHr-/ >=CH.aH. 

Boiling- > ^ ^ / ^ ^ 

point 157.°-158.° 170.°-173.° 172.°-174.° 

d 0.821 0.814 0.815 

Md .. 41.60 46.35 46.28 

Mr, (calc.) 41.03 45.64 45.64 

" CHs 

C>=< C>=< ^H3-<3=/ 

Boiling- ^f^> ^CH= ^CHa 

point 160.°-161.° 173.°-175.° 172.°-174.'" 

d 0.836 0.825 0.831 

Md •• 41.56 46.25 45.88 

Md (calc.) 41.03 45.64 45.64 

1 .2-Dimethyl-^^-Cyclohexene is of special interest since Meer- 
wein*^ discovered that it is smoothly formed by the dehydration of 
the cyclopentane derivative 1-methyl-l-a-hydroxyethylcyclopentane. 
CHj — CHg CH3 CHj — CHj — C — CH3 

I >C< -^1 M 

CH, — CH^ CH(0H).CH3 CH, — CH, — C — CH, 

The hydrocarbon is also formed by the dehydration of 1 . 2-dimethyl- 
cyclohexanol(l). It is therefore readily prepared from methylcyclo- 
hexane-2-one by treating with methyl-magnesium iodide and dehy- 
drating the resulting alcohol. The nitrosochloride is bluish in color, 
easily volatile with steam and melts at 58°-60°. It yields a dibro- 
mide CjHi^Br, melting at 154°-156° and by oxidation, the glycol 
melting at 38°-39°.^^ 

•' Ann. 360, 34. 

"Ann. Ut, 255 (1918). 

" Wallach, Ann. SSB. 278 (1913). 



308 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Ethylidenecyclohexane has been synthesized by the Reformatsky 
synthesis, condensing cyclohexanone and a-bromopropionic acid and 
decomposing the resulting cyclohexanolpropionic acid 

CHg — CHj 
/ \ OH 

CH, C< 

\ / CH{CH3).C0,H. 

CHj — CHj 

in the usual manner. The nitrosochloride melts at 132°.*'° Following 
the general rule that on treating with alcoholic sulfuric acid semi- 
cyclic double bond shifts to the ring, ethylidenecyclohexane when so 
treated yields ei%Z-A^-cyclohexene. The latter hydrocarbon is more 
readily prepared by treating cyclohexanone with ethyl-magnesium 
bromide and dehydrating the resulting tertiary alcohol in the usual 
manner. Propylidenecyclohexane is similarly prepared and also re- 
arranges readily to propyl-A^-cyclohexene.** 

The hydrocarbon 1 . 3-dimethyl-A^-cyclohexene, noted in the above 
tables, is identical with the so-called "tetrahydro-meta-xylene" ob- 
tained by condensing methylheptenone. It yields a nitrosochloride 
and a characteristic nitrolpiperidide melting at 130°-131°.^^ 

1.4 Di-isopropylcyclohexane: Several unsaturated hydrocarbons 
having the carbon structure of di-isopropylcyclohexane have recently 
been prepared by Bogert and Harris*" by well-known methods of 
synthesis. When the esters of the hydrogenated terephthalic acids 
were treated with methyl-magnesium iodide the glycols were not 
obtained, these passing immediately into the hydrocarbons. 



C-OH 



CH 



■..,^^"^ 




ch; 



.C-OH 




»s»WaUacli, Ann. S89, 189 (1912). 
«* Wallach, Ann. S60, 56. 
"Wallach, Ann. S96, 264 (1913). 
"J. Am. Chem. Soc. il, 16T8 (1919). 



I 



THE CYCLOHEXANE SERIES 



309 



CH,^ CH3 
C-OH 





CH. 



.-OH 



'C< 



C«3.^^CH, 




n 




CHj'^^^CH, 



CH, 







in. 



CH3 ^CHj 



The hydrocarbon I, 1.4-di-isopropenyl-A^"*-cyclohexadiene, melts at 
117°-117.5°, yields an oily tetrabromide and also a crystalline tetra- 
bromide melting at 107°-109°. When it was attempted to add more 
bromine, substitution and evolution of hydrobromic acid occurred 
similar to the behavior of A^-^^^^-p-menthadiene noted by Perkin, 
which adds smoothly only two atoms of bromine supposedly on ac- 
count of the fact that the two double bonds are in the conjugated 
position. Bogert and Harris regard their liquid and crystalline tetra- 
bromides as cis and trans isomers of the substance 



CH3— C-CH^Br 





CHj-C-CH^Br 



The refractive index of the hydrocarbon was determined in benzene 
and in chloroform solutions, using Eisenlohr's values, and an exalta- 
tion of the molecular refraction, due to the two conjugated double 
bond systems of 3.776, was found. Bogert and Harris note that almost 
the same exaltation of the molecular refraction was noted in the case 
of 1.4-disopropenylbenzene, i.e., 3.841, which they believe points to a 
structure analogous to Dewar's structure for styrene, 



310 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



CH=CH, 




CHj-C=CH^ 




CH=C-CH, 

The values obtained for the magnetic rotatory power of p-di-isopro- 
penyl-benzene, however, point to a Kekule, not a Dewar structure. 

Cantharene, a hydrocarbon obtained by the decomposition of 
cantharidene, has been synthesized by Haworth ^^ from 1-methyl-A^- 
cyclohexene in the following manner. The nitrosochloride of the 
methylcyclohexene was heated with sodium acetate in acetic acid, 
removing hydrogen chloride in the usual manner and by hydrolyzing 
the resulting unsaturated oxime l-methyl-A°-cyclohexene-2-one was 
obtained. A methyl group was introduced by means of methyl- 
magnesium iodide and the resulting tertiary alcohol was decomposed 
by heating with 8 per cent oxalic acid. 

CH. 




CanTharenol Cantharene 

Monocyclic Sesquiterpenes: The name "sesquiterpene" has been 
employed for a number of hydrocarbons of the formula CisH^^ occur- 
ring in essential oils. Semmler has recently made several hydrocar- 
bons of this empirical formula by condensing isoprene with various 

"J. Chem. 800. lOS, 1242 (1918). 



THE CYCLOHEXANE SERIES 311 

terpenes by heating them together in sealed tubes. Very little is 
known regarding the constitutions of the sesquiterpenes beyond the 
fact that some are acyclic and have four double bonds, some are 
monocyclic and have three double bonds, some are bicyclic having 
two double bonds and others are tricyclic and have only one double 
bond. It will readily be understood that the possible number of 
isomeric hydrocarbons is very great and it now appears that most of 
the hydrocarbons, described in the literature of twenty years ago as 
definite hydrocarbons, are in reality mixtures and that the separation 
of pure individual hydrocarbons from such mixtures is a difficult task 
indeed. Also it was usually assumed in the literature that the hydro- 
carbons regenerated from crystalline derivatives, such as the dihydro- 
chlorides, were identical with the original hydrocarbons, whereas many 
instances are known in which the structure of the regenerated hydro- 
carbon is quite different from the original. 

The monocyclic sesquiterpenes are probably derivatives of cyclo- 
hexane and are accordingly so classified. The physical data are often 
very helpful in showing whether the sesquiterpenes are monocyclic, 
bicyclic or tricyclic. As noted by Parry *^ the following constants are 
typical of these several groups. 

Mol. Refraction 
Specific Gravity (Calculated) 

Monocyclic sesquiterpenes 0.875 to 0.890 67.76 

Bicyclic " 0.900 " 0.920 66.15 

Tricyclic " 0.930 " 0.940 64.45 

Catalytic hydrogenation by Paal's, Skita's or Willstatter's methods 
and the reactions with hydrogen chloride or hydrogen bromide also 
indicate the number of double bonds in the hydrocarbon, hydrogena- 
tion being more certain since conjugated linkings frequently do not 
add the maximum number of molecules of halogen acid. 

Zingiberene and Zingiberol: This sesquiterpene occurs in ginger 
oil. According to Semmler and Becker *° it is monocyclic and con- 
tains three double bonds, one of which is in the ring and two in the 
side chain. The molecular refraction indicates that two of these 
double bonds are in conjugated positions; MR = 68.37, calculated for 
CibHji/— ^ is 67.86. This optical evidence is also supported by its 
chemical behavior, forming a dihydrochloride, melting at 169°-170'^. 
Catalytic hydrogenation in the presence of platinum gives hexahydro- 

" "The Chemistry of Essential Oils," Ed. Ill, Vol. I, Tl. 
"Ber. i8, 1914 (1913). 



312 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



zingiberene C15H30, but reduction by sodium and alcohol yields the 
monocyclic dihydrozingiberene, CigHjj, which also is good evidence of 
the existence of two conjugated double bonds, and since this reduction 
takes place very readily Semmler concludes that these conjugated 
double bonds are in the side chain. As with other substances contain- 
ing conjugated double bonds, zingiberene resinifies and polymerizes 
very readily on standing in the air or warming with sodium. Semmler 
and Becker state that when zingiberene is treated in acetic acid solu- 
tion with a little sulfurfc acid, that it is condensed to a bicyclic isomer 
which they have named isozingiberene. They have proposed the fol- 
lowing constitution for these two hydrocarbons 



CH3 



C-CH3 



ch3'^^Hh, 

Zingiberene 




^^r 



Isozingiberene 



Zingiberene forms a nitrosochloride melting at 96°-97° and a nitrosite 
melting at 97°-98° ( by treating zingiberene in cold petroleum ether 
with acetic acid and sodium nitrite). A nitrosate melting at 86° 
(with decomposition) is formed by treating the hydrocarbon, dis- 
solved in cold glacial acetic acid, with ethyl nitrite and slowly adding 
nitric acid. 

Zingiberene is associated in the essential oil of ginger, with a 
sesquiterpene alcohol, zingiberol,'" which yields zingiberene on decom- 
position by warming gently with potassium acid sulfate. The alcohol 
is partially decomposed on treating with acetic anhydride and does 
not readily yield a phenylurethane, and on treating the alcohol with 
hydrogen chloride or hydrogen bromide in acetic acid, the dihydro- 
chloride and dihydrobromide respectively, of zingiberene are formed. 
The alcohol is evidently a tertiary alcohol and from its relations to 
zingiberene the hydroxyl group must be situated at positions (8) or 

■"Brooks, J. Am. Chem. 8oc. S8, 430 (1916). 



THE CYCLOHEXANE SERIES 3lS 

(12) in the above figures. The alcohol has a persistent aroma of 
ginger oil but does not have the sharp taste of the "gingerol" discov- 
ered by Garnett and Greier®^ and recently shown by Nelson,^^ and 
others ®* to be a phenol derivative. [Cf. particularly Lapworth, Pear- 
son and Roy le.] Zingiberol distills at 154°-157° (14.5 mm.). 

The physical properties of zingiberene, and isozingiberene f*"" as 
follows, 

Zingiberene Iso-zingiberene 

Boaing-point 128°-129°(9mm.) 118°-122°(7mm.) 

d 0.8684 0.9118 

2(3° 

n 1.4956 1.5062 

D 

Mol. Ref. calc. for C,sH.2t/=' 67.86 

" found 68.37 66.50 

" calc. for Ci=H«/=^ 66.15 

According to Semmler and Becker the dihydrochloride noted above 
is really a derivative of isozingiberene since the latter hydrocarbon is 
formed from the dihydrochloride by digesting with alcoholic caustic 
potash. Hydrogenation by platinum black in acetic acid yields hexa- 
hydrozingiberene, C15H30, boiling-point 128°-129° (11 mm.) d20° 

0.8264, njQ 1.4560. Isozingiberene adds only four atoms of hydrogen 

to form the saturated bicyclic hydrocarbon. Like myrcene and other 
conjugated dienes, zingiberene is readily condensed by heating at about 
215° to a bicyclic isomer, and to a dimeride, CjqH^s, boiling-point 
260°-280° (11 mm.), d2oo 0.9287. 

A synthetic monocyclic sesquiterpene has been made by Roenisch °* 
in a manner which leaves little doubt as to its constitution and may 
properly be named isoamyl-a-dehydrophellandrene. By treating car- 
vone with isoamyl-magnesium iodide (in benzene solution) he obtained 
the unsaturated hydrocarbon, boiling-point 130°-132° (11 mm.) 
d22o 0.8679, [a]jy + 18° 30', nj^ 1.49478. 

«' Chem. Zentr. 1907, II, 924 ; 1909, II, 1593. 
•'J. Am. ahem. Soo. U, 1115 (1919) ; ig, 597 (1920). 

" Nomura, Chem. AT>s. 1917, 2662 ; Lapworth, Pearson and Royle, J. Chem. Soc. Ill, 
777 (1917). 

»* Schimmel & Co., Semi-Ann. Eep. 1917, 20. 



314 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



CH, 




CH, 



^S 



1=0 



+ M3I CH, 




CH(cH^^ 



CH, 



ch: 



CH, 




-%. 



-CH,-CH, 
CH, ^CH, 



CH, 



The synthetic hydrocarbon does not give a solid hydrochloride but is 
readily hydrogenated by Willstatter's method to the hydrocarbon 
CisHgo. 

Bisabolene, C15H24: This sesquiterpene is monocyclic, contains 
three double bonds and yields a trihydrochloride C15H27CI3, melting at 
79°-80°. Its constitution is not known but it is probably a derivative 
of cyclohexane. It was originally discovered in the essential oil of 
Bisabol myrrh but has since been found in other essential oils, a speci- 
men isolated from lemon oil by Gildemeister and Miiller ^^ having the 
following physical properties, boiling-point 110°-112° (4 mm.), d^co 

0.8813, [a]j3— 41° 31', n^j 1.49015. The regenerated hydrocarbons, 

obtained by heating the trihydrochloride with sodium acetate, distilled 
at 261°-262°. Bisabolene does not form a crystalline nitrosochloride, 
nitrosite or nitrosate. 



"=Sehimmel & Co.. Semi-Ann. Rep. 1909 (2), 50. 



Chapter IX. Cycl?^ Non-benzenoid 
Hydrocarbons: 

The Para-menthane Series. 

(1) Limonene and Dipentene. 

Limonene occurs in a very large number of essential oils. Dextro- 
limonene is found as the major constituent in the citrus oils, sweet 
orange peel, lemon, bergamot, lime, mandarin orange and petit-grain 
oil, also the essential oils of ginger grass, camphor, Manila elemi, 
caraway and other oils. It is most conveniently isolated from oil 
of sweet orange peel, constituting about 90 per cent of this oil. Loevo- 
limonene is found chiefly in the leaf oil of the silver fir, turpentine 
from Pinus serotina of the southern United States, one of the species 
of eucalyptus, Eucalyptus staigeriana, American oil of peppermint, 
oil of verbena, American penny-royal, etc. The optically inactive 
form, dipentene, is also found in nature in the essential oils of lemon 
grass, palma-rosa, ginger grass, Siberian pine needle, pepper, cubeb, 
camphor oil, ajowan, coriander, nutmeg, fennel, cardamom, etc. It is 
also formed by the racemization of d. or I. limonene by prolonged 
heating, by the rearrangement of less stable terpenes such as pinene '■ 
and phellandrene, by the condensation of two molecules of isoprene 
and is accordingly found in turpentines made by distilling pine stumps 
and the lighter fractions of rosin or copal oils made by the destructive 
distillation of rosin or Manila copal and the destructive distillation 
of caoutchouc. Formerly a number of different names were given to 
this hydrocarbon, but Wallach ' showed that the hydrocarbon frac- 
tions boiling at 175°-176° from orange peel oil ("hesperidene") , lemon 
("citrene"), caraway ("carvene"), bergamot, dill and pine needle oils 
yielded a tetrabromide melting at 104°, and that the corresponding 
hydrocarbon variously designated as cinene, cajeputene, kautschin, 

■ On heating pinene with anhydrous oxalic acid a mixture of dipentene and borneol 
esters are formed, cf. "synthetic camphor." 
'Attn, im, 277 (1885). 

315 



316 CHEMISTRY Of ThU NOM-BENZENOIL. HYDROCARBCSS 

di-isoprene and that from camphor oil, yielded a tetrabromide melt- 
ing at 125". On isolating I. limonene from pine needle oil Wallach' 
showed that the crystalline tetrabromide appeared to be identical 
with the tetrabromide from d-limonene, except for opposite hemihedral 
crystal development (like Pasteur's salts of tartaric ac.d), and that 
when equal portions of the d and Z-tetrabromides were dissolved and 
crystallized, the tetrabromide melting at 125° and characteristic of 
dipentene resulted. This relationship has since been established for 
other derivatives of limonene and dipentene. It was by such methods 
that the investigation of the terpenes began to be simplified. Thus 
the same relation was shown to exist between the nitrolamine deriva- 
tives of d and Himonene and those of dipentene, or the racemic forms. 
Wallach * discovered that when the nitrosochlorides of d or Z-limonene 
and dipentene were treated with aniline, condensation to the nitrol- 
anilides resulted, there being six forms. Their relations were made 
clear by Wallach as indicated in the following diagram, 
Z-limonene d-limonene 

a-nitrosochloride |3-nitrosochloride a-nitrosochloride p-nitrosochloride 

4' V 4^ v 

a-nitrolanilide p-nitrolanilide a-nitrolanlide p-nitrolanilide 
M.-P. 113° M.-P. 153° M.-P. 113° M.-P. 153° 

\ \ / / 

\ \ / / 

\ \ / / 

\ \/ / 

\ /\ / 

\ / \ / 

\ i/ \ / 

racemic, a-dipentene nitrol- racemic, p-dipentene nitrol- 
anilide, M.-P. 126° anilide, M.-P. 149° 

Physical Properties: The recorded physical properties of limonene 

20° 

are the following: boiling-point 175°-176°, d..o 0.846 to 0.850, n. — 

10 JJ 

1.47459,^ [a]j)=-f 125° 36',^ — 105°, —119.41°.' A sample of 
dipentene made by destructive distillation of caoutchouc, examined by 

'Ann. 2i6, 221 (1888). 

'Ann. 252, 94 (1889). For experimental details this paper Is recommended. 

"Wallach, Ann. SiS, 222 (1888). 

"Godlewski & Roshanowitsch, Chem. zentr. 1S99 (1), 1241. 

' Gildemelster, "Aetheriaohe Oele," Ed. 2, Vol. I, 325. 



THE PARAMENTHANE SERIES 317 

Schimmel and Co./ showed a boiling-point of 175°-176°, d2oo 0.844 

20° 
and n -—1.47194. The boiling-point of dipentene, 177° to 178°, is 

usually stated, in the older literature, to be higher than that of limo- 
nene but these higher boiling-points (sometimes given as high as 179°) 
were probably due to the presence of considerable high-boiling ter- 
pinene. (Until recently racemic compounds were believed not to 
persist in the liquid state, but Ladenburg ^ has shown, in the case of 
pipecoline, that this is possible, and Dunstan and Thole " have found, 
by means of viscosity measurements, evidence that racemic forms 
may exist in solution.) Limonene shows two broad absorption bands 
in the ultraviolet spectrum, but the absorption is increased in isomeric 
■para menthadienes in which the double bonds are nearer each other; 
limonene accordingly shows less absorption than other menthadienes.^" 
Perkin ^^ also showed that limonene has a lower magnetic rotation, 
M= 11.24, than the isomer A^'-^c) menthadiene, M = 13.06, the 
double bonds in the latter hydrocarbon being in the conjugated posi- 
tions. 

Limonene and dipentene are most conveniently identified by means 
of their tetra-bromides,^^ which are best prepared by adding the cal- 
culated amount of bromine to the hydrocarbon dissolved in about four 
volumes of acetic acid, keeping the mixture chilled during the gradual 
addition of the bromine. Remarkably high yields of the nitroso- 
chlorides of limonene and pinene can be obtained by following the 
method recently described by Rupe.^^ Concentrated sulfuric acid and 
concentrated sodium nitrite solution are separately dropped into a flask 
containing a thin paste of common salt and concentrated hydrochloric 
acid. The evolved gases are cooled, dried by passing through calcium 
chloride and then passed into a solution of limonene in one volume 
of ether and one half volume of glacial acetic acid, cooled in ice and 
salt. Heating limonene or dipentene nitrosochlorides with alcoholic 
caustic alkali yields carvoxime." Both d and ^carvoxime melt at 
72° but the racemic carvoxime, derived from dipentene, melts at 93°. 
When limonene nitrosochloride reacts with sodium azide the chlorine 

'Ber. I,!i, 2374 (1910). 

'J. Chem. Soc. 93, 1815 (1908) ; 97, 1249 (1910). Evidence of racemic menthyl 
mandelates, cf. Flndlay, J. Cliem. Soc. 91, 905 (1907). 
"Hantzsch, Ber. l,S, 553 (1912). 
"■/. Chem. Soc. 89, 854 (1906). 
"Power & Kieber, Arch. Pharm. 232, 646 (1894). 
" Helv. chim. Acta. J,, 149 (1921). 
"Deussen & Halin, Chem. Zentr. 1910 (1), 1142. 



318 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

atom is replaced by the azide group N3 ; the resulting nitroso-azide also 
yields carvoxime on decomposition.^'' 

Oxidation of limonene in the presence of water yields carvone, 
carveol (q.v.) and a resin.^^ Oxidation of limonene by chromyl 
chloride yields chiefly cymene which is then further oxidized to 
a-p-tolylpropaldehyde and p-tolylmethyl ketone/' resembling terpi- 
nene in this respect, but in the case of limonene much more resin is 
formed. Condensation of limonene with formaldehyde brought about 
by the use of para-formaldehyde in glacial acetic acid with the addi- 
tion of a little sulfuric acid, yields an unsaturated alcohol homo- 

19° 
limonenol, boiling-point 122°-126° at 13 mm., d 0.9720. Accord- 

4° 

ing to Prins ^^ addition of formaldehyde to a double bond occurs to 
give an oxide ring which may then hydrolyze to a glycol, which in 
turn decomposes to give an unsaturated alcohol, as in the case of 
limonene, or many yield a methylene ether, as indicated in the fol- 
lowing, 

R 
RCH = CHR —^ RCH — CHR — -> RCH — CH< 



H,C 



CH,OH 



RC = CHR R 

RCH — CH< 



A 



H,OH or 





\ 

CH^ — CH^ 



This reaction with formaldehyde has also been studied by Prins in the 
cases of pinene, camphene, cedrcne, etc. When dipentene dihydro- 
chloride, a by-product in the manufacture of artificial camphor, is 
treated with chlorine to form a trichloromenthane and this product 
decomposed, cymene is formed.^^ 

Carvomenthene: (A^-p-menthene?) . 

When limonene is hydrogenated in the presence of platinum black, 
the reduction proceeds in two stages, the first product being carvo- 
menthene and the final product paramenthane.^" Carvomenthene 

"Forster & Gelderen, /. Chem. Soc. 99, 2061 (1911). 

"Blumaun & Zeltschel, Ber. i7, 2623 (1914). 

"Henderson & Cameron, J. Chem. Soc. 95, 972 (1909). 

"Chem. Aia. li, 1662 (1920). 

"Brit. Pat. 142,738 (1919). 

MVavon, Bull. Boo. cMm. (4) 15, 282 (1914). 



THE PARAMENTHANE SERIES 319 

made in this manner is optically active, [ajgyg +118°. Bacon "^ 

prepared carvomenthene from limonene monohydrochloride (by HCl 
in cold carbon bisulfide solution) by making the Grignard complex, 
magnesium limonene hydrochloride, and decomposing this with water. 
However, racemization accompanies the formation of the hydro- 
chloride. Bacon also made the hydrochloride of carvomenthene and 
reduced it to para-menthane in the same manner by means of the 
Grignard reaction. Carvomenthene boils at 175°-177°, its hydro- 
chloride boils at 85°-86° (13 mm.) and the nitrosochloride melts 
at 95°. 

Para-menthane : By the catalytic reduction of limonene by hydro- 
gen in the presence of platinum black,^^ by the hydrogenation of para- 
cymene in the presence of catalytic nickel ^^ and by heating the semj- 
carbazone or hydrazone ^* of menthone with sodium ethylate at 

15° 
160°-170°, para-menthane is produced, boiling-point 169°, d — ^ 0.803. 

In the latter process heating the semicarbazone at 160° first forms 
the hydrazone which subsequently decomposes to the hydrocarbon, 

>C = N.NH.CONH, + H,0 >>C = N.NH^ + 00^ + NH, 

The Constitution of Limonene: The structure of limonene is inti- 
mately related to the structure of terpineol, terpin and carvone. 
Tilden ^° and Wallach "^ had, at an early date, shown that when terpin 
is digested with dilute acids, it yields terpineol and that by more 
energetic dehydration terpineol also decomposes further, forming 
water and dipentene. ' 

CioHi8(OH)2 > C10H17.OH > CjoHio 

terpin terpineol dipentene. 

Terpineol and terpin are converted by hydrogen chloride to a crystal- 
line dichloride " CioHigCla melting at 50°, which is identical with the 
dihydrochloride made from dipentene.^^ The position of the double 
bond in terpineol was suggested by Wallach ^^ and confirmed by later 
researches of Baeyer ^'^ and others, particularly on the ground of the 

"PMippine J. Sci. 1908, 52. 

"Vavon, Compt. rend. 11,0, 997 (1909). 

^» Sabatier & Senderens, Oompt. rend. 156, 184 (1913). 

"Wolff, Ann. S9i, 86 (1912). 

"Bcr. n, 848 (1879) ; J. Chem. Soc. S5, 287 (1879). 

"Ann. BSO, 258 (1885). 

"List, Ann. 67, 367 (1848). 

"Ann. «7, 105 (1893). 

"Ber. ge, 2558 (1893). 



320 CHEMISTRY OF THE NON-BENZENOW HYDROCARBONS 

relations between terpineol and carvone (see below). Wallach's pro- 
posed constitution of terpineol was 



HC 



<^' 



I^OH 

This proposed structure was open to the objection that such a sub- 
stance could not decompose with loss of water to give a hydrocarbon 
containing an asymmetric carbon atom, whereas Wallach himself 
had shown that dipentene was a mixture of the two active d and 
Z-limonenes. A little later, 1894, Wagner '" published his well-known 
paper "On the oxidation of cyclic compounds," in which he modified 
Wallach's terpineol structure to 



CH, 



HC 



<^ 




^ 



C— OH 



CH, 



which is abundantly supported by other evidence published since, of 
which probably the most convincing is W. H. Perkin, Jr.'s synthesis 
of terpin, terpineol and a series of related substances.'^ 



'"Ber. 87, 1636 (1894). 

"'8th Int. CO»g. Appl. Chem. VI, 224 (1912). 



THE PARAMENTHANE SERIES 321 

CH3 

/ . . . 

The group R — C — OH is readily synthesized by the action 

\ 

CH3 

of zinc methyl, and particularly easily by the action of magnesium 
methyl iodide on acid chlorides, esters or methyl ketones and Perkin 
accordingly carried out his synthesis as follows: 

(1) Pentane-1, 3, 5-tricarboxylic acid was heated with acetic anhy- 
dride when CO2 and water were eliminated and cyclohexanone-4-car- 
boxylic acid was formed. 

HO.C.CH.CH^ CH2CH2 

>CH.CO,H > 0C< >CH.CO,H 

HO2C.CH2CH2 CH2CH2 

(2) The ester of this acid was then treated with methyl-magnesium 
iodide in the usual manner when the ketone group reacts much more 
readily than the COjR group ; the resulting hydroxy acid was converted 
to the corresponding bromide by heating with hydrobromic acid and 
the resulting tertiary bromide digested with sodium carbonate, remov- 
ing HBr to give l-methyl-A^-cyclohexene-4-carboxylic acid. 

CH,CH, HO CH,CH, 

0C< >CH.CO,R > >C< >CH.CO,R 

CHjCHj CH3 CH^CHj 

Br CH,CHA /CH.CH3 

-> >C< CKCO^H^CH^ — C >CH.CO,H 

CH3 CH2CH2/ \CH2CH2 

(3) On treating the ester of this acid with methyl-magnesium 
iodide an almost quantitative yield of a-terpineol was obtained. 

CHCH2 CHCH2 CH3 

/ \ / \ / 

CH3C CH.CO2R -» CH3C CH — C — OH 

\ / \ / \ 

CH2CH2 CH2CH2 CH3 

a-Terpineol is characterized by its fine odor of lilacs and is manu- 
factured in comparatively large quantities by decomposing terpin 
hydrate or terpin (made from pinene) by means of phosphoric acid. 
Unless specially purified the commercial product is liquid at ordinary 
temperatures and contains a little ^-terpineol '^ melting when pure at 

"Stephan & Helle, Ber. S5. 2147 (1902). 



322 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

32°, and the liquid terpinenol-l.'^ In nature, only a-terpineol ap- 
pears to be formed. Terpineol is the major constituent of commercial 
long leaf pine oil '* made by distilling the wood with steam. A good 
commercial pine.oil will show 75 per cent distilling between 211° and 
218°. It has proven particularly valuable for the concentration of 
low-grade copper ores by the flotation process. The stability of ter- 
pineol in the presence of alkali renders it valuable in the perfuming 
of soaps. Commercial a-terpineol melts at 35°, boils at 217°-218° at 
760 mm., at 1(M°-105° and 10 mm., has a density of 0.935 to 0.940 at 

20° 
15° and a refractive index n ^—1.4808.'= An exceptionally pure speci- 
men of a-terpineol, made by Wallach ^^ by the action of dilute sulfuric 
acid on homonopinol, showed melting-point 37°-38°, boiling-point 
218°-219°, and fa]^)— 106° (in 16.34 per cent solution in ether). 

The highest optical activity observed for natural terpineol is 
[a] £)+ 95° 9' (from bitter orange peel oil) and [a]j) — 27° 20' shown 

by a specimen of J-terpineol from linaloe oil. A specimen of synthetic 
Z-terpineol" showed [a]^ — 117.5°. Commercial terpineol is soluble 

in 9 volumes of 50 per cent, in 3 volumes of 60 per cent and in about 
2 volumes of 70 per cent alcohol. When free from water it is miscible 
in petroleum ether. The nitrosochloride of d or Z-terpineol melts at 
107°-108°, that of i-terpineol at 112°-113°; the corresponding nitrol- 
piperidine compounds melt at 151°-152° and 159°-160° respectively. 
By shaking terpineol with an excess of concentrated hydriodic acid 
the dihydroiodide CioHigl^ is formed, melting at 77°-78°. Terpineol, 
being a tertiary alcohol, is very easily decomposed with loss of water 
when heated with potassium acid sulfate or oxalic acid; even acetic 
anhydride partially decomposes it, on heating, forming dipentene. 
Phenylisocyanate yields a phenylurethane,^^ the inactive form melting 
at 113°. The a-naphthylurethane ^' melts at 147°-148°. As with 
most tertiary alcohols, the phenyl and naphthylurethanes are diflJcult 
to prepare, partial decomposition of the alcohol, with the formation 
of water, causing the conversion of phenyl isocyanate to diphenyl urea. 
In preparing the isocyanate it is advisable to separate the crystals of 

"Wallach, Ann. S62, 269 (1908). 

"Teeple, J. Am. Chem. Boc. SO, 412 (1908) ; Met. & Chem. Eng. 11, 247 (1913). 

" GUdemeUter, "Aetherisclie Oele," Ed. 2, Vol. I, 394. 

"Ann. seo, 89 (1908). 

»' ErtscMkowsky, Bull. soc. chim. (3) IS, 1584 (1896). 

"Wallach, Ann. 875. 104 (1893). 

"Schlmmel & Co. Semi-Ann. Kep. 1906 (2), 33. 



THE PARAMENTHANE SERIES 323 

diphenyl urea, which first form, by taking up the liquid portion in a 
little perfectly dry ether. The mixture should be permitted to stand 
three or four days protected from the moisture of the air. Good 
yields of terpinyl hydrogen phthalate and succinate can be obtained 
by allowing an excess of the alcohol to stand with the acid anhydride 
at temperatures below 100°.^" The d-glucosides of both a and p-terpi- 
neol have been made by treating p-tetra-acetylbromoglucose in ethyl 
ether with an excess of the terpene alcohol in the presence of silver 
carbonate. The acetyl groups are removed from the product by means 
of barium hydroxide. The resulting glucosides are rapidly hydrolyzed 
by hot dilute acids but are very slowly split by emulsin.*^ Glucosides 
of citronellol and of dihydrocarveol were prepared in the same manner. 
It is practically certain that glucosides of many terpene alcohols exist 
in nature, in addition to the few, such as coniferin, which are known 
to occur in nature. 

Tertiary alcohols appear to be capable of forming addition products 
with chromic acid, when the alcohols are dissolved in an inert solvent 
and shaken with concentrated chromic acid or the solid crystals. In 
the case of a and p-terpineols the addition products are liquid and 
unstable.*'' 

The hydration of a-terpineol to terpin hydrate can be beautifully 
demonstrated, as for a lecture experiment, by dissolving terpineol in 
5 parts of 80 per cent phosphoric acid at 30°, allowing to stand a few 
minutes and then diluting about six times with cold water, when within 
a few minutes a bulky matted mass of crystals of terpin hydrate will 
form.*' The reaction is less complete with 60 per cent sulfuric acid 
and Aschan ** has shown that 45 per cent sulfuric acid, shaken with 
pinene for 16 hours at + 1° gives a yield of 53 per cent terpin. The 
ease of making terpin hydrate from commercial long leaf pine oil has 
been pointed out by Teeple.*= 

The synthetic a-terpineol made by Perkin was converted into terpin 
hydrate by agitating with dilute sulfuric acid ; by heating with potas- 
sium hydrogen sulfate dipentene was obtained, thus completing the 
synthesis of these three important substances. Additional proof of the 
constitution of terpin was furnished by Perkin and Kay, who showed 

"Pickard, Lewcock & Yates, Proc. chem. 8oc. 29, 127 (1914). 

*' Haemaelaeinen, Biochem. Z. i9, 398 (1913). 

''Wienhaus, Ber. 47, 322 (1914). 

" Prins, Ctiem. Ahs. 1317, 2773. 

" Oltem. Aba. 1919, 2759. 

"Loc. cit. 



324 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



that when ethyl cyclohexanone-4-carboxylate was treated with large 
excess of methyl-magnesium iodide, terpin is formed. 





II 

c 

/ \ 



H2C CH2 



+ 3CH3MgI 



\ / 

CH 



CO, 



R 



CH, 



C — OH 



H^C CH 



H^C CHj 

\ / 

CH 

C — OH 

/\ 

CH3 CH3 

1 . 8-terpin. 



This synthesis proves conclusively the position of the two hydroxyl 
groups in terpin. * 

Terpin Hydrate is not known to occur in essential oils. It melts 
at 116°-117° and readily loses a molecule of water on heating or on 
standing over sulfuric acid to form terpin, melting-point 104°, whose 
structure is shown above. Terpin exists in two stereo-isomeric forms 
of the CIS and trans type.*" Terpin derived from terpin hydrate by 
dehydration is the cis form; the trans form, melting-point 156°-158°, 
is made from irans-dipentene dihydrobromide and silver acetate. 
Trans-terpin does not crystallize with water of crystallization. 

Other evidence for the structure of limonene, a-terpineol and terpin 
had already shown their constitution with reasonable certainty. 
Wagner had proposed his now accepted constitution of a-terpineol 
largely to overcome the objection made against Wallach's constitution, 
that the latter could not give an optically active hydrocarbon, limo- 
nine, on dehydration. By oxidizing a-terpineol first with perman- 
ganate and then with chromic acid, Wallach *' obtained a series of 
oxidation products finally resulting in homoterpenylic and terpenylic 



"Baeyer, Ber. 26, 2865 (1S93) ; », 5 (1896). Van't Iloff, lu 1874, had predicted 
that cyclic compounds of this type would be found to exist in two stereo isomeric 
forms. 

"Ann. 221, 110 (1893). 



THE PARAMENTHANE SERIES 



325 



acid and he showed that these changes could readily be interpreted by 
Wagner's constitution for a-terpineol, i.e., 



A 




;-0H 

ch; ch, 

a-terpineol 



yMVlnO. 



CH3 



OH 




OH 
H 



CrO, 




CH3 ^CH, 



X=0 



CO^H 



CHi 



.C-OH 
Cri3 ^CH, 






XQ,H 



C=0 CO,H C=0 




CH3 "CH3 



cK "CH3 

Homoterpenylic acid Terpenylic acid 



Although the constitution of these important acids was worked out 
with reasonable certainty ** their synthesis by Lawrence and Simon- 
sen ^° removes all question as to their structure. The constitution of 
these acids also has a very direct bearing on the constitution of 
pinene and Simonsen's synthesis is therefore mentioned in outline as 
follows, 



"Wallach (Ann. 259, 322 [1890]), had suggested the above constitution for ter- 
penylic acid and Its correctness has been confirmed by the work of Flttlg (Ann. 288, 
176 [1896]), Mahla and Tlemann (Ber. 29, 928 [1896]), and Schryver (J. Ohem. Soc. 
63, 1338 [1893]). 

"J. Chem. 80c. 15, 627 (1899) ; 91, 184 (1907). 



326 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 
CO,R COjR CO^R CO^R 

H,C CH, CH,MeI H,C CH, 



(a) 



\ / 

\/ 
CH 



CH, 



., CH3MgI H,C 

> \ / 

CH 



C-OH 

CH3 CHg 




^b) COjR 

i 



I 
CHJ 



+ 



CO^R 

A, 



^H, 



/ 

NaC — CO,R 

io 

CH, 



COoR 

CH3 COjR 

CH2 CHj 
\ / 

\/ 

C — : CO2 

CH, 



R 



When the latter ester is hydrolyzed with hydrochloric acid, CO^ is 
eliminated; the ester of the resulting p-acetyladipic acid yields homo- 
terpenylic acid (ester) when treated with magnesium-methyl iodide, 
as in (a). 

The above work, together with Perkin's synthesis, conclusively 
proves the position of the double bond in a-terpineol. The position of 
the other double bond in limonene was shown by reference to the con- 
stitution of carvone and dihydrocarveol. The nitrosolimonene of 



THE PARAMENTHANE SERIES 



327 



Tilden and Shenstone '" proved to be identical with carvoxime,^^ from 
which it follows that at least one and perhaps both double bonds in 
limonene and in carvone are similarly situated. On reduction of 
carvone one double bond is saturated yielding dihydrocarveol, which 
on oxidation first by permanganate, followed by chromic acid and 
sodium hypobromite, finally yields 2-hydroxy-para-toluic acid, which, 
when the intermediate products are also considered, indicates that 
the double bond in dihydrocarveol is in the side chain. ^^ 




Dihy dro carv e ol 



CH, 



CH, 



^ \ 


^" 






pr^N 




^OH 


NaOBr 


•^^ 




:o^H 








CO^H 



OH 



2-hydroxy- 

para-toluic 

acid 



The above facts make clear the relations between limonene, a-ter- 
pineol and terpin, and the dihydrohalogen derivatives obtained from 
all three, i.e., 

"J. Chem. Soc. SI, 554 (1877). 

"Goldschmidt & Ziirrer, Ber. IS, 2220 (1885). 

'^WaUach, Ann. 275, 110 (1893) ; Tiemann & Semmler, Ber. iS, 2141 (1895). 



328 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 





CH, 



OH 



±!k^ l--rerpineol 



+ HJ) 



-H,0 



terpm 



CH3 ^CHj. 



H3 




Br 



ch: 



X-OH 



> by ^5 oceTaTc 
ond hydrolysis 



•3 CH. 

The Constitution of Carvone. 

The conversion of carvone to carvacrol, and carvoxime to carva- 
crylamine were early observed and, though not understood, served to 
call attention to the probability that carvone, carvoxime and limonene 
were para-menthane (l-methyl-4-iso propylcyclohexane) derivatives 
and that the oxygen atom in carvone occupied position (2) . Wagner ^' 
with his usual perspicacity, proposed a constitution for carvone in 
1894, which has proven correct. He based his deductions upon the 
results obtained by Best ^* and by Wallach °^ on oxidizing carvone, 
although the constitutions of the oxidation products they obtained 
were not then definitely known. Terpenylic acid can be obtained 
from carvone in the following manner, the ring being broken at two 
points to give acetic acid as one of the oxidation products. 

CH3CO2H + 
= C CO^H 

/I I 

/ CH, CH, 

\/ 

c\ 

— i « 



?"* 






CH3 


— 


^N 


=0 


HO 
H 


-K>s 


fO 


X. ^^ 


-> 




\^ ^ 




CHf^^CH, 






c»^%, 





o 



CH 



/\ 



"Ber. 87, 2270 (1894). 



CH,OH 



'Ber. er. 1218 (1894). " Ber. St, 1496 (1894) 



THE PARAMENTHANE SERIES 



329 



= C CO,H. 

/I I 

\ / 

\ / 
C\ 

i^ 

CHo CH. 



(by replacing OH by Br and 
reducing) 







The relation between carvone and limonene is very well shown 
by Wallach's °° conversion of terpineol to carvone by removing hydro- 
gen chloride from terpineol nitrosochloride by means of caustic alkali 
and then boiling the resulting oxime with acids, thus hydrolyzing the 
oxime to the ketone and simultaneously removing the original hydroxyl 
group. 



CH. 




oc-TerpineoI 




CH, 



F=N.OH 




+ NOCI 






+ KOH 



=N.OH 



+ dil- ocid» 







carvone 



fO 



Other menthadienes were made synthetically by W. H. Perkin, Jr., 
and his assistants. A^-*(°)-p-menthadiene was made in the following 
manner. Para-toluic acid was reduced by sodium and alcohol to 
l-methylcyclohexane-4-carboxylic acid which on bromination, fol- 
lowed by removal of HBr by sodium carbonate or quinoline in the 
usual maimer, yielded l-methyl-A'-cyclohexene-4-carboxylic acid 
the ester of which yields A'-p-menthenol (8) when treated with mag- 

"Ann. m. 120 (1898). 



330 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



nesium methyl iodide. On digesting this menthenol with potassium 
acid sulfate A*-'(^)-p-menthadiene is formed. 

CH, 



H AH 



/CH3 H, 



^6^+\C0,H(p; 



CH, 



Ha 
H, 



H, 



Ha 




H, 



CQ,H 




CHj 



CO^H 








CO^H 



>C<:OH ,C5^ 

CH, CH, CHf ^CH, 



113 V..13 v,..3 ~.-2 

A'-p-menthenol(8) ^^■^^^'>-p-menthadiene 

Like many substances having two double linkings in the conjugated 
position, this menthadiene reacts with bromine to form a dibromide 



in which the double bond has shifted to the 



CHBr 
CH, 



>C = C< 



CH,Br 
CH, 



position. Also, as contrasted with limonene, this menthadiene is capa- 
ble of combining with only one molecule of HCl or HBr, these products 
being liquid. The same behavior toward bromine and HBr and HCl 
is shown by the ortho and meta-menthadiene derivatives containing 
conjugated double bonds, i.e.. 



CH, 




y"^ 



^\, 




CH3 



\^-^<-^'>-o-menthadiene A'-^'-^''>-m-menthadiene A^-^'-^^-m-menthadiene 



THE PABAMENTHANE SERIES 



331 



Another synthesis of A^-^(°)-p-menthadiene was developed by 
Perkin in collaboration with Wallach." In this synthesis 1-methyl- 
cyclohexane-4-one is condensed, by the Reformatsky reaction (zinc 
and a-bromopropionic ester) , to the oxy acid. 

CH, Cn3 CHj 








OH 
CH, ^O.H 



CH 



XO^H 



The oxy acid loses water, when digested with acetic anhydride, and the 
resulting unsaturated acid decomposes further when distilled, losing 
COj. The seniicyclic hydrocarbon was then converted into its nitroso- 
chloride and this by eliminating hydrogen chloride by alkali yields 
an oxime which was hydrolyzed in the usual manner to the ketone. 

CHj CH3 9H3 CH3 



— > 



CHj C(^H 



CH3 





CH 
CHj 



H, 



+2 



Mjlffl, 



V 




C=N.OH 

6H3 



CH, 




C=N.OH 

I 

CH, 



r 

CH, 







a: 



CH;^^rH^ 



CH, 

A^-p-menthenol(8) 

The ease with which this teriary alcohol is decomposed with loss of 
water to form the A'-*(»>-p-menthadiene is worthy of note; shaking 

"Afm. rn, 198 (1910). 



332 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

with 1 per cent sulfuric acid at warm temperature effects this change. 
The products obtained by these methods are, of course, optically 
inactive and therefore, to obtain A^-p-menthenol(8) of high optical 
activity, Perkin selected natural pulegone as his original material. 
As is well known, pulegone decomposes on heating with alkali to give 
l-methyl-cyclohexane-3-one, which in this case showed [«]£) + 8°. 

By treating this ketone with sodium amide and carbon dioxide 
l-methyl-cyclohexane-3-one-4-carboxylic acid was formed which was 
dehydrated yielding d l-methyl-A'-cyclohexene-4-carboxylic acid of 
high optical activity [a]jj+ 150.1° 




COjH 



l-methyl-A^-cyclohexene-4- 
-carboxylic acid, [a]j) -\- 150.1° 



The following physical properties of A'-«(=)-p-menthadiene were 
noted by Perkin and Wallach: boiling-point 184°-185°, d —0 858, 

20° 
n ^ 1.4924 from which the molecular refractivity is 46.02, calculated 

for CioHie/=2 is 45.24 showing the exaltation due to the conjugated 
position of the double bonds. 



THE PARAMENTHANE SERIES 333 

Terpinolene and the Terpinenes. 

The constitution of the terpinenes has been a matter of consider- 
able controversy but researches of recent years, particularly the work 
of Wallach, has solved the puzzle in a very satisfactory manner. Til- 
den, Armstrong and others had studied the action of mineral acids 
on turpentine or pinene, also limonene and the alcohols, terpineol and 
terpin, but the chief result of their investigations was to the effect 
that a new terpene, CioHu, was probably formed. It was not defi- 
nitely characterized either by physical constants or chemical deriva- 
tives, and it was given a variety of names. In 1885 Wallach °^ applied 
his tetrabromide method, which he had used in the identification of 
limonene and dipentene, to the high-boiling fraction boiling from 
179°-190°, obtained by the action of alcoholic sulfuric acid on tur- 
pentine. From this fraction he prepared a new tetrabromide, 
CioHieBr^ melting at 116°-117°, thus proving the existence of a new 
terpene, which he named "terpinolene." In the mixture of hydrocar- 
bons resulting from the action of alcoholic sulfuric acid on terpin 
hydrate, dipentene, phellandrene or cine'ol, he showed that the fraction 
boiling from 179°-182° contained what he termed "terpinene." This 
fraction did not give a crystalline tetrabromide. A fairly good yield 
of terpinolene was also obtained by the action of hot concentrated 
oxalic or formic acid on a-terpineol, the terpineol being slowly dropped 
into the acid and the terpinolene removed by distilling with steam as 
fast as formed, as otherwise the new terpene underwent further change. 
Being influenced by the constitution for a-terpineol which he had pro- 
posed, Wallach ^^ suggested the following structure for terpinolene, 

CH3 





H 



X- 



Although von Baeyer had accepted Wallach's a-terpineol formula, he 
nevertheless advanced his now generally accepted A^-'(^> structure for 

"Ann. m, 283 (1885) ; 1830, 262 (1885). 

"Ann. m, 145 (1893). This formula was later put forward by Harries, Ber. S5, 
1169, as the constitution of terpinene (q.v.). 



334 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



terpinolene. Baeyer *° considered that this structure was indicated by 
the formation of blue nitrftso derivatives. The position of the second 
double bond was indicated by its relation to a-terpineol and its optical 
inactivity. In view of the fact that other isomeric hydrocarbons are 
also simultaneously formed and that radical changes in constitution 
are known to be brought about by heating with acids, these considera- 
tions would have little weight were it not for other evidence. Baeyer 
made terpinolene by brominating limonene dihydrobromide and treat- 
ing the resulting tribromide with zinc dust; saponification of the 
resulting mono-acetate yielded a new terpineol, y-terpineol, melting- 
point 69°-70°. Baeyer had shown that other substances containing 
the group >C = C(CH3)2, for example, tetramethylethylene, give blue 
nitroso compounds. He had also shown that generally dibromides in 
which the two bromine atoms are in the 1.2 position are reduced by 
zinc dust and acetic acid to the olefine group. 

\/ \/ 

C — Br C 



i 



-Br 



A 




/\ 



t2HBr 
> 



H3 




Br 



CH3 




C 



+Br 



H, 




Br 







H, 



PjCXHj 




OH 



1 



"Bar. «r. «8 (1894). 



C 

II 

y-terpineol 
M.-P. 69°-70° 



Br 



A 

terpinolene 



THE PARAMENTHANE SERIES 335 

Also since the nitrosochloride of y-terpineol was also blue, Baeyer 

reasoned that this terpineol contained the >C ^ C (0113)2 group as in 

terpinolene. Dehydrating agents were shown to convert y-terpineol 

to terpinolene. 

Semmler °^ has made a terpinolene of unusual purity by reducing 

terpinolene tetrabromide (which can be isolated from impure material) 

by treating with zinc dust in alcohol instead of acetic acid. Semmler's 

terpinolene had the following physical properties: Sp. Gr. 20°, 0.854, 

20° 
n ^p— 1.484, boiling point at 10 mm. 67°-68°, boiling-point at 760 mm. 

183°-185°, optically inactive. Heat converts terpinolene to dipentene 
and acids partially convert it to a mixture containing a and y-terpi- 
nenes, dipentene and terpinolene. Terpinolene is apparently not found 
in nature; Clover*^ reported it in Manila elemi, but Bacon,*^ working 
on material from the same source, was unable to confirm this. Terpi- 
nolene is obtained as a by-product in the manufacture of commercial 
terpineol and is occasionally found as an adulterant of lavender and 
other oils. Terpinolene has been synthesized from nopinone and 
methyl nopinol (q.v.) .°* 

The Terpinenes. 

The formation of "terpinene" by the action of alcoholic sulfuric 
acid on pinene, terpin hydrate, cineol, dipentene and phellandrene has 
been mentioned in connection with terpinolene, which is also formed 
in the reaction mixture. Its occurrence in nature was first noted in 
the case of oil of cardamoms by Weber.*^ It has been reported to 
occur in Manila elemi, but according to the researches of Clover and 
Bacon,^° on over a hundred specimens of authentic material, different 
individual trees yield an oleoresin containing either limonene or phel- 
landrene of remarkable purity ; the commercial oil accordingly contains 
both of these terpenes, but since Clover and Bacon worked with fresh 
material it is probable that the terpinene reported by others was 
formed from phellandrene by the action of formic or other acids 
developed by air oxidation. "Terpinene" has usually been identified 
by means of the nitrosite melting at 155°. According to Schimmel 

•■Ber. ii, 4644 (1909). 
"PMUppine J. Sci. 1907, 1. 
" PhUippme J. Eci. A. 1309, 93. 
"Wallach, Ann. 356, 244 (1907). 
"Ann. 2S8, 107 (1887). 
" PhOipplne J. Sd. 1909, 93. 



336 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



& Co.,°' Wallach's a-terpinene occurs in coriander oil and y-terpinene 
in ajowan, lemon and coriander oil. 

Terpinene was frequently confounded with dipentene, in the earlier 
literature. Both yield crystalline addition products with halogen 
acids, but although the melting points of the corresponding dihydro- 
halides are very close together, a marked lowering of the melting- 
point results when the two are mixed. The terpinene dihydrohalides 
are best prepared from sabinene. 

"Terpinene" Dipentene 

aoHi,.2HCl Sl°-52° 50° 

CioH»,.2HBr 58°-59° 64° 

C10H4..2HI 76° 77° 

Wallach*^ has shown that with aqueous alkali the dihydrochloride is 
converted into a terpin melting at 137° and not identical with cis or 
trans-1 .S-ierpin which corresponds to limonene dihydrochloride. 
Wallach reasoned that if the new terpin was a di-tertiary alcohol, as 
its behavior indicated, it must have the structure of 1 . 4-dihydroxy- 
p-menthane, if it was in fact a para-menthane derivative. It was 
further distinguished from ordinary or 1.8-terpin by the formation 
of an oxide differing from cineol (eucalyptol). It should be men- 




M.-P. OS- 102°-105° 
trans- 156°-158° 



H,0 



-> 1.8 cineol 



C— OH 



CH, 



OH 



l/t-terpm 



M.-P. cis- 116°-117° 
trans- 137° 



H,0 



1.4 cineol 




OH 

CH 

" Gildemelster & MUIler, Wallach-Featechrift 1909, 443. 
"Ann. SSO, 157 (1906) ; 356. 200 (1907). 



THE PARAMENTHANE SERIES 



337 



tioned that on dehydrating ordinary terpin, one of the products is the 
oxide, cineol, which has been shown to be an oxygen ether, or oxide, 
the oxygen atom of which is attached to the carbon atoms 1 and 8. 
The difference between the two terpins and their oxides are, as sug- 
gested by Wallach. 

Additional evidence that this is the constitution of the new terpin 
was furnished by its synthesis ^^ from sabina ketone. (Sabinene and 
sabina ketone, q.v., had already been shown to contain an unstable 
tri-carbon ring, as shown.) 

CH, CH) 

-OH i_OH 




C3H7 C3H, 

Reduction of ascaridol (q.v.) also yields 1.4-terpin. 

It will be evident that 1.4-terpin, or the corresponding dihydro- 
chloride, can conceivably decompose with loss of two molecules of 
water or hydrochloric acid, respectively, to give four different para- 
menthadienes, i.e., 



CH, 



CH, 




CH, 



n 




H 
CHr^CH, 





CHj 



m 



CHj ^CH, 





13. 



m. 




CHC' ^CH, 



CH3 "CH, 



a-terpinene ^-terpinene y-terpinene terpinolene 

Of the hydrocarbons represented above IV has the constitution which 
had already been shown to be that of terpinolene. A hydrocarbon 
having the structure represented by II, A'-^(^)-p-menthadiene, has 
been synthesized by Wallach ''" from sabina ketone and found to yield 
a tetrabromide melting at 154°-155°, and boiling at 173°-174°. It is 

••Wallach, Ann. S57, 64 (1907). 

"Ann. S57, 68 (1907) ; S62, 287 (1908). 



33S CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

therefore not present in ordinary "terpinene" boiling at 179°-182° 
and which does not yield a crystalline tetrabromide. The constitution 
of "terpinene" therefore resolves itself into I or III, or a mixture of 
these two hydrocarbons. 

On oxidizing ordinary terpinene with permanganate, a a'-dioxy- 
a-methyl-a'-isopropyladipic acid, melting-point 189° is formed. This 
acid can only be derived from A^-'-p-menthadiene. 





a-terpinene erythrite adipic acid derivative 

The structure of this acid has been proved beyond question by its 
synthesis, in the following manner, 

io 



H^C 



/ 



+ 2HCN - 



H,C 



CH3 

C — OH. 



CN 



H,C 



\ 



CO 



k 



B.J 



H^C CN 

\ / 

C\ 

I OH. 
C3H7 



followed by hydrolyzing the nitrile to the adipic acid derivative. The 
structure of this acid can also be shown by following the oxidation of 
terpinenol- (4) CH, 




OH 



CA 



Ttrpinenol-rt) 



THE PARAMENTHANE SERIES 



339 



which also yields this adipic acid derivative." Further oxidation 
yields dimethyl-acetonylacetone whose dioxime melts at 137°. 

Additional evidence of the presence of A^"''-p-menthadiene in "ter- 
pinene" has been furnished by the conversion of terpinene nitrosite to 
carvenone, first by reducing the nitrosite in alcohol solution by zinc/^ 
and later with particularly good yields, by reducing the nitrolamine 
by zinc and acetic acid." 



H, 




NHR 
l=N.OH 



V 



terpinene 
nitrolamine 




carvenone oxime 



carvenone 



In the investigation of terpinene from various different sources or 
made in different ways, it was observed that those specimens which 
give good yields of the a a'-dioxy-a a'-methylisopropyladipic acid, 
melting at 189°, also give good yields of the above crystalline nitro- 
site.'* On the other hand it has been noted that specimens which yield 
little or no nitrosite also yield very little of the adipic acid derivative 
melting at 189°. 

The presence of A^ ■ *-p-menthadiene in terpinene was made prac- 
tically certain by the discovery of Gildemeister and Miiller " that one 
of the oxidation products was isopropyl tartronic acid. This specimen 
of terpinene was isolated from ajowan oil and Gildemeister and Miiller 
were unable to isolate a crystalline nitrosite, nor could they detect the 
adipic acid derivative among the oxidation products. All experience 
with terpinene, particularly as brought out by Wallach's extensive 
investigations,'" indicate that "terpinene" is a mixture containing vary- 
ing proportions of the two isomers, which Wallach designates as a and 
y-terpinene (see above). Auwers has studied the terpinene question 
from the standpoint of their physical properties, particularly the re- 

" Wallach, Ann. S6S, 266 (1908). 

"Amenomiya, Ber. S8, 2730 (1905). 

"Wallach, Ber. iO, 582 (1907). 

"Wallach, Ann. Sli, 229, 230 (1910). 

"Schlmmel & Co. Semi-Ann. Eep. ia09 (2), 16. 

"Ann. S6i, 2C1, 285 (1908) ; S68, 13 (1909) ; S7i, 224 (1910). 



340 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

fractive index. In accord with Wallach's findings, Auwers showed 
that a terpinene having a particularly high' refractive index, as would 
be expected in the case of a-terpinene, also gave a very large yield of 
crystalline nitrosite and the adipic acid derivative. Wallach believes 
that the preparation of strictly pure terpinenes, terpinolene and the 
phellandrenes is impossible." 

Carvenene is probably an impure a-terpinene. It was so named by 
Semmler,^' who prepared it from carvenone by the action of PCI5 
followed by reduction. According to Semmler, alcoholic sulfuric acid 
converts carvenene to an isomeric hydrocarbon isocarvenene which he 
considers is identical with jB-terpinene. Auwers does not agree with 
Semmler as to the supposed purity of carvenene and claims that it is 
not identical with a-terpinene which Auwers made from O-cresol. 

Henderson and Sutherland '° have made what appears to be mainly 
a-terpinene by reducing thymohydroquinone to 2 . 5-dioxy-p-menthane 
and decomposing this with removal of two molecules of water. Their 
a-terpinene showed a boiling-point of 179°, specific gravity about 
0.840 and refractive index 1.4779. Pickles *" isolated a terpene "origa- 
nene" from the volatile oil of Origanum hirtum, which he considers is 
probably a-terpinene. 

Crithmene. 

This terpene is mentioned in connection with the terpinenes since 
it yields terpinene dihydrochloride on treating with hydrogen chloride. 
It is contained in the volatile oil of Crithmum maritimum?'^ Its boil- 

20" 

mg-pomt IS 178°-179°, specific gravity, 0.8658, n-j=^ 1.4806. It does 

not yield a crystalline tetrabromide, the nitrosite melts at 89°-90° 
and the nitrosate at 104°-105°. It yields two nitrosochlorides which 
can be distinguished by their different crystal forms, although the 
melting-points are very close together, 101°-102° and 103° and 104°. 
The discoverers have suggested that crithmene is probably A^-(^)-*('>- 
p-menthadiene. 

"Fairly pure a-terplnene has been synthesized by Wallach, Ber. «. 2404 ri909> 
■•' Ber. U, 4474 (1908) ; J,l, 522 (1909). • f, \ »"»;. 

"J. Chem. Soc. 97, 1616 (1910). 
"J. Chem. Soc. 93, 862 (1908). 

" Fransesconi & Sernaglotto, AM accad. Llncei, 1S13, 231, 312 : Deleplne & Belsunee 
Bull. toe. chim. (4) 23, 34 (1918). ' 



THE PARAMENTHANE SERIES 341 

CH3. 

II 

c 

/ \ 

H,C CH, 

I I 

H,C CH, 

" \ / 

C 

II 

c 

/ \ 

CHg CII3 

crithinene 

The Oxides. 1.8-Oineol, 1.4-Cineol, Pinol and Ascaridol. 

These oxides of the terpene series are usually described without 
reference to other intramolecular ethers, or oxides, of the non-ben- 
zenoid hydrocarbons. Unfortunately the number of such organic 
oxides, to use the customary term, which are known, is so small that 
it is not possible to show such close relationships between those which 
happen to have been first prepared from the terpenes, and those pre- 
pared from other non-benzenoid cyclic or open chain hydrocarbons, as 
might be desired. 

In the first place it may be noted that the ethylene oxide ring is 
considerably less stable than the tri-carbon ring in cyclopropane and 
its derivatives. Thus ethylene oxide reacts with water on heating 
to give glycol and this reaction is catalyzed by a trace of a mineral 
acid.'^ 

CH^ CH^OH 

\ 

+ H^O > 

/ 

CH, CH^OH.. 

Oxides of this type have been carefully studied in the case of the 
oxides of ethylene, propylene, the butylenes, amylenes and hexylenes. 
They react with hydrogen chloride with considerable energy, forming 
the chlorohydrins; with ammonia to form the corresponding amino 
alcohols, with nascent hydrogen to give alcohols and with a variety of 
other substances, as, for example, sodium malonic ester, 

"Henry, Compt. rend, m, 1404 (1907). 



342 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

CHs Na . CH^ONa 

I >0+ >C.(COAH,), >| 

CH, H CH^CHCCO.CoH,),. 

The greater instability of the ethylene oxide ring as compared with 

the tri-carbon ring is brought out in the case of isobutylenoxide 

(CH3),C CH,, which reacts with water to form the glycol merely 

\ / 


on shaking together with water at ordinary temperatures. (The group 
(0113)20 < in cyclopropane usually results in greater stability.) *' 
As with carbocyclic rings a great increase in stability is noted, com- 
pared wth ethylene oxide, when the oxide ring contains five or six 
atoms. Thus diethylene oxide OH, — — CHj is the principal 

I I 

CH^ — — OH2 

product resulting when ethylene glycol is distilled with 4 per cent 
aqueous sulfuric acid; in the same manner, but with smaller yields, 
1.8-terpin yields ordinary cineol and 1.4-terpin yields 1.4-cineol. 
Diethylene oxide, in contrast to ethylene oxide, yields a series of well- 
defined addition products ®^ of the type which Baeyer suggested were 
derivatives of quadrivalent oxygen; the sulfate, O^HgOj.HjSO^ melts 
at 101°, the dibromide O^HiOjEr^ melts at 60°, etc. When the con- 
stitutions of these two substances are compared it is apparent that 
the reason for the greater stability of diethylene oxide is the hexatomic 
ring. 

CH^ OH2 — — OH2 

, >o I ■ I 

^H3 OH2 — — CHj 

diethylene oxide. 



k 



In connection with the stability of diethylene oxide its comparatively 
high melting-point + 9-5°, and boiling-point 100°-101° are significant. 
If the valence directions of quadrivalent oxygen are in the directions 
of the four comers of a regular tetrahedron as we assume to be the 
case in the carbon atom, then we should expect a close parallel with 
non-benzenoid carbocylic substances, as regards stability and ease 
of formation and rupture. Derick and Bissell ^s have called attention 

"Ingold, J. Chem. Soc. U9, 305 (1921). 

"Paterno & Spallino, Qazz. chim. Ital. 37 (1), 106 (1907) ; Faworskl, Chem. Zentr 
1907 (1), 16. 

"J. A.m. Chem. Soc. 1916, 2478. 



THE PARAMENTHANE SERIES 343 

to the fact that trimethylene oxide CHjCHjCHjO, which contains 



four atoms in the ring is markedly more stable than ethylene oxide. 
[The stereochemistry of oxygen has been very little studied. There 
would seem to be no reason why substances containing asymmetric 
oxygen cannot be resolved into optically active forms, possibly by 
Pasteur's method of mechanically picking out crystals of opposite 
hemihedral development.] It has been noted *° that 1.4 and 1.5- 
glycols and their oxides behave in a manner markedly different from 
the 1.2-glycols. The former are readily converted into their oxides 
of five and six membered rings respectively by heating with 60 per 
cent sulfuric acid and these oxides are quite stable to water; in fact, 
they can be heated with water to 200° several hours without forming 
glycols. It should be pointed out that their behavior is strictly 
parallel to the behavior of the better known oxides, cineol and pinol. 

Up to the present time the only oxides whose synthesis has been 
attempted with the idea of industrial utilization are the simpler 1.2 
oxides, i.e., ethylene oxide for the manufacture of phenylethyl alcohol 
by the Grignard reaction,^' 

CeH,MgBr+ (CHJ.O > CeH,CH,CH,OH, 

and other organic preparations,^* and the 1 . 2 oxides of butylenes and 
amylenes which have been proposed as solvents for cellulose esters.^" 
However, the 1.4 and 1.5 oxides are quite stable and should prove 
industrially valuable if they could be made economically. 

Tetramethylene oxide. CH^ — CH^ boils at 67° and is 

I >o 

CHj — CII2 

easily soluble in water. It is not reacted upon by water at 150° but 
is attacked by fuming hydrobromic acid. 

1 A-Oxidopentane. CHj — CH — CH3 is a liquid of agree- 

] >o 

CH2 — CHj 
able ethereal odor boiling at 77°-78° and soluble in 10 parts of water 
at ordinary temperatures. It can be made by heating the 1.4-glycol 
with 60 per cent sulfuric acid or by the action of caustic alkali on the 

" Petrenko-Kritschenko & Konschin, Ann. S42, 51 (1905). 

"Grignard, Compt. rend. 136, 1260 (1903) ; Altweijg, V. S. Pat. 1,315,619. Accord- 
ing to the writer's experience this reaction gives yields 75 to 80 per cent, of the theo- 
retical ; ethylene oxide is best made by solid caustic soda on nearly anhydrous ethylene 
chlorohydrin. 

"•Cf. 8oc. chim. du Rhone, Brit. Pat. 128,552; 12S,553 ; 128,554 (1919), — for 
aminobenzoic acid derivatives; Brit. Pat. 128,911 (1919) for chloroethyl esters; Brit. 
Pat. 128,908 (1919) for etbanolamines and aminophenol ethers. 

"Walker, U. S. Pat. 972,952. 



344 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

corresponding chlorohydrine. The dimethyl derivative is a product of 
the action of sulfuric acid on diallyl, 

CH^CH = CH^ CH,CH — CH, 



•ii 



>0 boiling-point 90°-92° 



CHjCH ^ CHj CHjCH — CHg 

1 .6-Oxidopentane (Pentamethylene oxide) ."' 

CH, — CHo 

/ \ 

CHs 

\ / 

CHj — CHj 

can be obtained by heating 1 . 5-dibromopentane with water at 100° 
or from the glycol by the sulfuric acid method. The oxide boils at 
81°-82°. The same methods of preparation have proven successful 
in the conversion of 1.4 and 1.5-dihydroxy-n.hexane°^ to the corre- 
sponding oxides. Most of the glycols containing six or more carbon 
atoms are quite difficult to prepare and since interest in them is so 
narrow, they are not described here. The above examples, however, 
are given in support of the general thesis of the present volume, that 
the chemistry of the so-called hydro- aromatic hydrocarbons is ration- 
ally a part of the larger division of non-benzenoid hydrocarbons. 

Cineol is the name given by Wallach and Brass ^' to the substance 
CjoHigO, boiling-point 172°, which they isolated from the volatile oil 
of wormseed, "Oleum cince," from Artemisia maritime L. It was also 
shown that "cajeputol" from cajeput oil and "eucalyptol" were identi- 
cal with cineol. Gladstone had shown that cineol could be distilled 
over metallic sodiimi without change and Hell and Ritter "^ obtained 
an addition product with hydrogen chloride and accordingly suggested 
that the oxygen was bound as in ethylene oxide, but recognized that 
cineol is much more stable than ethylene oxide. 

The following additive compounds have been prepared from cineol, 
(a„H,30),.HCl; (C,„H,30),.Br,; C,„H„O.Br,; (C,„H,30),.I,; 
C,„H,80.HBr; C.oH.^O.HgPO,; CioHi^O . HaAsO,,^^ also well crys- 
tallized products with hydroferricyanic and hydroferrocyanic acids, 
a and P-naphthol,'* iodol and resorcin. This property is utilized for 
the detection and quantitative estimation of cineol, methods based 

•» Hochstetter, Monatsh. S3, 1073 (1902). 

»'Franke & Lieben, J. Chem. Soc. Abs. 1913, I, 491. 

•'Ann. 225, 291 (1885). 

"" Merck, German Pat. 132,606. 

"Hermlng, German Pat. 100,551; Chem. Zentr. 1899 (1), 764, 



THE PARAMENTHANE SERIES 345 

upon the reaction with phosphoric acid" and with resorcin being most 

favored for quantitative estimation.*" 

Composition of Product" Melting-Point 

CioHisO.HBr 56. ° 

CxoH«O.Cj4NH. (iodol) 112. ° 

(C.oH«0)2.C,H,(OH)j (xesorcia) 80. ° 

(C,„Ha)j.CoH4(OH)»(hydroquinone) 106.5° 

OioSisO . CeHsOH 8. 

CioH«O.CJl40H.CH3 (orthocresol) 50. ° 

CioHuO. thymol 4.5° 

Baeyer °' first pointed out that these addition products, which are 
generally decomposed easily into their original constituents, are prob- 
ably derivatives of quadrivalent basic oxygen. Baeyer regarded the 
comparatively stable compound of ethyl ether and magnesium-alkyl 

X 
halides as "oxonium" compounds of the constitution (C2H5)20< 

MgR 
but more recent investigations point to the structure C2H5 MgX 

>0< 
C2H5 R 

which was proposed by Grignard. When cineol is used as a reaction 
medium instead of ether, the reaction of magnesium, ethyl iodide and 
cineol takes place with almost explosive violence unless the cineol is 
diluted with benzene.'* When cineol is added to a solution of mag- 
nesiumethyl iodide in ethyl ether, the ethyl ether is displaced and the 
cineol compound, (Ci(|Hi80)2MgC2H5l, is precipitated. When this 
compound is decomposed by dilute acids cineol is almost quantitatively 
regenerated, but if the complex is heated to 170°-190° and then care- 
fully decomposed by cold dilute acids, a-terpineol is formed. If the 
conditions are reversed and magnesium-ethyl-bromide is poured into 
cineol, an oil is produced the products of hydrolysis of which have not 
been investigated. l-Ethyl-p-menthanol(8) should be formed if the re- 
action product, like many other Grignard ether complexes which have 
been investigated, is capable of decomposing in several ways. In the 
case of ethylene oxide and phenyl magnesium bromide, phenyl ethyl 
alcohol is the principal product. Cineol reacts with acetic anhydride 
in the presence of metallic chloride ZnCl2 or FeClg to form terpinyl 
acetate and terpin diacetate.'" 

•■Cf. Parry, "Chemistry of Essential Oils," Ed. 3. Vol. I, 321, Vol. II, 256; 
Gildemeister, "Aetherische Oele," Ed. 2, Vol. I, 547. 
••Bellucl & Grassi, Chem. Zentr. 19U (1), 884. 
"Ber. Si, 2679 (1901) ; S5, 1201 (1902). 
"Plckard and Kenyon, J. Chem. Soc. 91, 896 (1907). 
•• Knoevenagel, Ann. 402, 111 (1919). 



346 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The constitution of cineol is clearly indicated by its formation 
from 1.8-terpin by oxalic acid and other dehydrating agents, by the 
formation of dipentene dihydrochloride from cineol by the action of 
hydrogen chloride (in acetic acid), by the absence of a double bond 
and the absence of a carbonyl group. Cineol was formerly regarded 
as the 1.4 oxide but when a-terpineol was shown to be A^-p-men- 
thenol (8) and ordinary terpin to be the 1 . 8 derivative, the constitu- 
tion attributed to cineol was revised to accord with these facts. Hot 
permanganate solution oxidizes cineol to cineolic acid, which sub- 
stance retains the 1.8 oxide grouping. 

CH, 




■^ 



•CO;,H 



cineolic acid, M.-P. 197° 

Cineol occurs in the volatile oil of many species of eucalyptus and 
the commercial valuation of eucalyptus oils is usually determined by 
their cineol content. Commercial oils are derived from a number of 
different species and earlier references to the essential oil of Eucalyp- 
tus globvlus undoubtedly refer to the mixed oil from several species. 
The genuine oil of Eucalyptus globulus contains 50 to 70 per cent of 
cineol, the balance being d-a-pinene, and minor percentages of a ses- 
quiterpene alcohol which has been named globulol, an unidentified 
terpene and very small proportions of butyric, valeric and caproic 
aldehydes. R. T. Baker and H. G. Smith have made a systematic 
survey of the various species of eucalyptus and the volatile oils 
derived from them, the results of which have been published in a 
comprehensive monograph ^"^ and in a series of papers in the Journal 
of Proceedings, Royal Society of New South Wales. Baker and Smith 
find 58 species yielding oils whose principal constituents are cineol and 
pinene, 14 in which pinene and sesquiterpenes are the chief compo- 
nents, 9 which contain notable, percentages of a new aldehyde "aro- 



i»> "Eucalypts of Tasmania, '• 1912; J. Soc. Chem. Ind. S2, 710 (1913). 



THE PARAMENTHANE SERIES 



347 



madendral," "^ 33 species which yield oils characterized by phellan- 
drene and piperitone (q.v.) , and several other species whose oils differ 
markedly from those above mentioned/"^ 

Cineol crystallizes on chilling the fraction boiling at 174°-178° 
from good eucalyptus oil and its isolation in this way is comparatively 
easy, though naturally not quantitative. 

A ketone derivative of cineol has been made from a-terpineol by 
first preparing a-terpineol nitrosochloride, treating this with hydrox- 
ylamine, thus replacing CI by — NH.OH. and hydrolyzing the 
resulting product by water.^"' 




a-terpineol 

1.4-Cineol: This isomer of ordinary cineol has not been found 
in nature, but was discovered by Wallach as one of the products of 
the dehydration of 1.4-terpin by oxalic acid."* It boils at 172° but 
does not crystallize on cooling to — 15°. It is quite stable to per- 
manganate solution. 

Ascaridol is one of the most remarkable organic compounds known. 
It was discovered by Schimmel & Co. in 1908 ^°' in the volatile oil of 
American wormseed or Chenopodium ambrosioides, L., var anthel- 
minticum. It was found to contain two atoms of oxygen and on heat- 
ing to 130°-150° decomposes with explosive violence. On reducing 
by Paal's method, four atoms of hydrogen are taken up and one of 
the stereoisomeric forms of 1.4-terpin are formed. This 1.4-terpin, 
melting at 116°-117°, is regarded by Wallach "° as the cis form. 
(The identity of this terpin was clearly shown by its conversion to 
terpinene dihydrochloride and by its decomposition to 1.4-cineol.) 

'"J. Proc. Roy. Soc. N. S. W. 1900, 1. 

"" An exceUent review of the eucalyptus oils is given in Parry, "Chemistry of 
Essential Oils," Ed. 3, Vol. I, pp. 319-358. 

■"Cusmano & Linari, Gazz. iS (1), 1 (1912). 
'"Ann. 3918, 62 (1912). 
'"•Reports, 1908 (1), 108. 
'"Ann. S9B, 59 (1912). 



348 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



The absence of double bonds and hydroxyl or carbonyl oxygen, its 
peroxide-like properties and its relation to 1.4-terpin, indicates, in 
Wallach's opinion, a peroxide structure. Nelson"^ first showed the 
peroxide character of ascaridol but suggested that the two peroxide 
oxygen atoms connected the 2.5 positions. By treating with ferrous 
sulfate solution in the cold two glycols CioHjsOs, melting at 62.5°-64° 
and 103°-104° are obtained. Heating the higher melting glycol with 
dilute sulfuric acid yields p-cymene. According to Wallach's consti- 
tution for ascaridol, the erythritol CioHjoOi, melting at 128°-130° 
should yield a, a'-methyl-isopropyl-a, a'-dihydroxyadipic acid, and 
Nelson obtained an oxidation product of this acid, i.e., 2-methylhep- 
tane-3 . 6-dione. By acid permanganate Nelson has split the acid 
CiflHieOg, from the lower melting glycol, to 2-methyl-heptane -3.6- 
dione. Nelson suggests the following relationships.. 





ascaridol 



erythritol 



kjVCoH kU<ON k^"^" 



glycol 



1 .4-cineolic acid 



Ascaridolic acid, which possesses the structure of a 1. 4-cineolic acid, 
was resolved by Nelson by means of its cinconidine salt to the d. and 
I. forms. 

The physical properties of ascaridol are, boiling-point 83° under 



5 mm. pressure, sp. gr. (20°) 1.008, [a] 



■ 4° 14 and n- 



20° 



-1.4731. 



'D - D 

Pinol: The resemblance of pinol to the two cineols is indicated 
by its chemical behavior and its methods of preparation. Thus terpi- 
neol dibromide,"^ on treating with aniline or alcoholic alkali loses one 
molecule of hydrogen bromide to form an unsaturated bond and loses 
a second molecule of HBr after the fashion of the bromo-hydrines 
and chlorohydrines to form the oxide pinol. 



""J. Am. Chem. Soc. 33. 1404 (1911) ; 35, 84 (1913). 
'"'Wallach, Ann. 25.1, 254, 261 (1889). 



THE PARAMENTHANE SERIES 



CHj 



349 





CH; XH3 




.0 



CH3 XH, 



a-terpineol dibromide pinol 

Like cineol the oxide ring is quite stable but the double bond 

reacts normally, being oxidized by permanganate to terebinic acid, 

adds bromine to form pinol dibromide, melting-point 94°, gives a 

nitrosochloride, etc. The odor of pinol resembles cineol and camphor. 

With mineral acids it readily yields cymene. Its physical properties 

20° 20° 

are as follows, boiling-point 183°-184°, d 0.942, n.=— 1.4714. 

When pinol is treated with hydrogen bromide in acetic acid solu- 
tion, the oxide ring is broken, as with other oxides, and so-called pinol 
hydrobromide is formed, which on treating with alkali yields "pinol 
hydrate," 




-OH 

pinol pinol hydrate 

The dibromide of pinol hydrate on treating with alkali yields a 
dioxide, (^^ Q^ 

-Br 

Br 

0. 




350 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

On treating pinol tribromide with zinc in acetic acid pinolone is 
formed. This reaction has been a puzzling one and is worth noting 
as an instance, now established beyond question, of the conversion of 
the six carbon ring to the cyclopentane ring. Wallach ^°° has proven 
that dihydropinolone is acetylisopropylcyclopentane. Hydrogenation 
of pinolone yields the saturated ketone dihydropinolone, the constitu- 
tion of which has been shown both by decomposition studies and by 
synthesis, to be 1.3-acetylisopropylpentanone. The synthesis is of 
interest as employing reactions of quite general application. 




dihydropinolone 

The fact of the formation of the cyclopentane ring is thus clearly 
established. Wallach suggests an explanation of this change which 
is based upon the conversion of the glycid group to a ketone group, 
many examples of which are known, particularly as shown by recent 
researches of Darzens.^^" 



H 
Br 


CH3 


'H Br 


CH, 





pinol tribromide 



Br 




'"Arm. S8i, 193 (1911). 

""Compt. rend. US, 443, 1105 (1911). 



THE PARAMENTHANE SERIES 



351 




H,0 



CH3 

CO 

-CH 



or 



H,C. 



CH, 



CH 

pinolone 

As mentioned above, chlorohydrines yield oxides when treated 
with caustic alkali. Slawenski "^ has made pinol and pinol hydrate 
by the action of caustic potash upon the chlorohydrin of terpineol 
(the latter substance being made by the direct addition of hypochlor- 
ous acid to terpineol). The formation of pinol and pinol hydrate 
shows that the chlorine is in position 6. 

An oxide of the diterpene series has been discovered in Java, citro- 
nella oil. The oxide, C^oHg.O, boils at 182°-183° (at 12 mm.). It 
contains two double bonds and is reduced by hydrogen and platinum 
black to C20H38O: it yields a monohydrochloride melting at 107.5°. 
When citronellal is heated with oxalic acid, one of the products is an 
isomeric oxide C^oHsfi.^" 

Other Alcohols of the Faramenthaue Series. 

It is evident that by the partial decomposition of ordinary terpin 
or terpin hydrate, four isomeric terpineols can theoretically be pro- 
duced, i.e., 




CH. 



CH3 



OH 




OH 



"x 



a-terpineol 
Inactive M. 
Active M.-P. 



P. 35 
37°- 



38° 



^-terpineol 
M.-P. 32° 




y-terpineol b-terpineol 

M.-P. 69°-70° (unknown) 



"'Chemik. PoUki, in, 97 (1917) ; Ghem. Abs. IS, 887 (1919). 
'"Semmler, Ber. i7, 2077 (1914) ; Spornitz, Ber. i7, 2478 (1914). 



352 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

a-Terpineol has been described in the foregoing pages on account 
of the importance of its constitution to the structure of the related 
substances of this series. 

^-Terpineol is a constituent of commercial terpineol ^^' made by 
the partial decomposition of terpin hydrate. It has not been found 
in nature. Its physical properties are as follows, melting-point 
32°-33°, boiling-point 209°-210°, d in supercooled state 0.923, 

20° 
n __ 1.4747. Its phenylurethane melts at 85°, the nitrosochloride at 

103°,^^* the nitrolaniline derivative at 110° and the nitrolpiperidine 
derivative at 108°. 

P-Terpineol was made synthetically by Perkin,^^^ in a manner 
which clearly confirms its structure. Incidental to the synthesis of 
a-terpineol, described above, a small amount of hydroxyisopropyl- 
cyclohexane-4-one was formed, which ketone was dehydrated in the 
usual manner. When the resulting unsaturated ketone was treated 
with magnesium-methyl iodide, |3-terpineol was formed. 







CH3 



rCH^MlI 



'^, 



tH, 



H, 




OH 



^-terpineol 



The decomposition of |3-terpineol by oxidation has been studied by 
Stephan and Helle "^ and by Wallach.^^' One of the products of 
oxidation, l-methyl-4-acetyl-A^-cyclohexene has been utilized by 
Wallach ^" for the preparation of a number of saturated and un- 

"' Schimmel & Co. Semi-Ann. Rep. 1901 (1), 79; Stephan & Halle, Ber. S5, 2147 

"'Wallach, Ann. Sis, 128 (1903). 
"'J. Chem. Soc. 85, 659 (1904). 
"'hoc. cit. 

"■•Ann. SSi, 88 (1902). 
^^'Ann. m, 202 (1918). 



THE PARAMENTHANE SERIES 353 

saturated alcohols. Thus magnesium-ethyl iodide yields homo-a- 
terpineol 



!.-<( ^C(OH)< 



CH, 
CoH„ 



Nascent hydrogen reduces the carbonyl group and when the result- 
ing product is treated with dilute sulfuric acid 1.8-dihydroxy-l- 
methyl-4-ethylcyclohexane, melting at 94°, is formed. Two other 
1.8-terpins were described in the same paper, i.e., addition of water 
to homo-a-terpineol yields 

HO / V CH3 

>C<; >C(OH)< 

CH3 \ / C,H, 

melting-point 65°-67°, and secondly hydration of 

CH3 
CH, 



C,H„-<^ )>C(OH)< 



by dilute acids gave the corresponding 1.8-terpin, crystallizing with 
one molecule of water,, melting at 75°-76°. 

y-Terpineol has not been found in nature, but is one of the minor 
reaction products when ordinary 1.8-terpin is partially decomposed 
by oxalic or phosphoric acids. It was prepared by Baeyer incidental 
to his investigation of the constitution of terpinolene (q.v.). It is 
characterized by its relatively high melting-point, 69°-70°, and its 
blue nitrosochloride melting at 82°. On heating with about one 
volume of concentrated formic acid terpinolene results.^^" 

^'-p-Menthenol{8) , was made synthetically by Perkin and Wal- 
lach^^° incidental to their synthesis of A°-*(°>-p-menthadiene. It 
melts at 41°, boils at 205° with slight decomposition and yields a 
phenylurethane melting at about 128°, the melting-point varying 
somewhat with the rate of heating owing to decomposition at this 
temperature. 

A^-p-Menthenolil) , is related to the phellandrenes (q.v.). It is 

"•Wallach, Ann. ses. 11 (1909). 
"'Ann. S7i. 198. 



354 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

easily decomposed by dehydrating agents to give a-phellandrene. It 
was made synthetically by Wallach^^^ by the action of magnesium 
methyl iodide on 4-isopropyl-A^-cyclohexenone. It boils at 92° 
(10 mm.). 

The Terpinenols: Several terpene alcohols are known which can 
be derived from the 1.4-terpin of the terpinene series, and are hence 
called terpinenols. As in the case of 1.8-terpin, noted above, loss of 
one molecule of water from 1.4-terpin can theoretically lead to the 
formation of four isomeric alcohols. 



CH3 




X" 




CH, 



X" 




Terpmeol-4- Terpinenol-l unknown y-Terpineol 



Of the substances indicated above, it will be noted that IV is identical 
with Y-terpineol. 

Terpinenol-4 is found in nature in a number of essential oils, 
juniper, Ceylon cardamon, nutmeg and zedoary.^^^ It is formed by 
the hydration of sabinene by cold dilute sulfuric acid.^^* The physi- 
cal properties of optically active terpinenol-4 are as follows, boiling- 

19° 
point 209°-212°, d^^^ 0.9265, [a]^^ +25° 4', n__ 1.4785. It has 

not been obtained in crystalline form. Both terpinenol-4 and terpi- 
neol-1 give terpinene dihydrochloride when treated with hydrogen 
chloride in glacial acetic acid, and also give 1.4-terpin on hydrating 
with cold, dilute sulfuric acid, although this hydration takes place 
much more slowly than with a-terpineol. The two terpinenols are 
however distinguished by their oxidation products,^^* 

"'Ann. S59, 283 (1908). 

12! Terpinenol — 4 Is present in comparatively large proportions in one of the 
Formosan lauracKe closely , resembling the camphor tree; Schimmel & Co. Semi-Ann. 
Rep. 1915 (2), 42. 

"•Wallach, Ann. SeO, 94, 97 (1908) ; S6e, 279 (1908) 

>«WaUach, Ann. SSe, 210 (1907). 



THE PARAMENTHANE SERIES 



355 



(a) 




terpinenol-4 1 .2.4-- trioxy-p-menthane A'-carvenone 

{^^-p-menthenol 4) M.-P. 116°-117° (H^O). 




terpinenol-1 1, 3, 4-trioxy-p-menthane A^-menthenone "° 

M.-P. 120°-121° 



Terpinenol-1 occurs in commercial terpineol and can be isolated 
from the forenmnings obtained when large quantities of crude terpin- 
eol are distilled with steam. It has also been synthesized by the 
action of magnesium methyl iodide on A^-4-isopropyl cyclohexenone. 
Its physical properties ^^° are as follows, boiling-point 208°-210°, d 

lo 

18° 
0.9265, and n^^ 1.4781. 

Dihydrocarveol, A^*"'-p-menthenoI(2), is found in nature in oil of 
caraway, associated with carvone. Its importance in the work of 
determining the constitutions of limonene and related substances has 
already been pointed out. It can be made by the reduction of carvone 
by sodium and alcohol,^^' or by the reduction of carvoxime to dihy- 
drocarvylamine and treating the latter with nitrous acid. Complete 



"' A'-P-menthenone is characterized by Its boiling-point 235°-237° 
melting at 77°-79° and Its semicarbazone melting at 210°. 
"•WaUach, Ann. sse, 218 (1907). 
""Wallach, Ann. fns. 111 (1893). 



the oxlme 



356 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



reduction yields carvomenthol.^^* The relationships between the more 
important substances of this carvone series may be indicated as fol- 
lows, 




CH, XH^ 



carvacrol ■ carveol dihydrocarveol carvomenthol 




carvone carvotanacetone dihydrocarvone tetrahydro- 

carvone 

Dihydrocarveol is characterized by oxidation by chromic acid to dihy- 
drocarvone, whose oxime melts at 88°-89° (inactive) or 115°-116° 
(active form), and by its physical properties,^^' boiling-point 224°, 

20° 
d 0.9368, and n _- 1.4836. By shaking with 3 per cent sulfuric 

acid it is hydrated to 2 . 8-dioxy-p-menthane (M.-P. 112°-113°). 

Carveol is one of the principal products of the oxidation of limo- 
nene by air in the presence of water.^^" It boils at 226°-227°, yields 
a phenylurethane melting at 94°-95°, and a phthalate melting at 
136°-137°. Its methyl ether (by CHgONa on 1,2,8-tribrom'omen- 
thane) boils at 208°-212.° 

Isopulegol, A'(°)-p-menthenol(3). This alcohol is not found in 
nature but is readily formed from citronellal by the action of acids; 

"'Cf. Henderson & Schotz, J. Chetn. Soc. 101. 2565 (1912). 
"» Schimmel & Co. Semi-Ann. Eep. 1905 (1), 51. 
""Blumann & Zeltschel, Ber. I,T, 2623 (1907). 



THE PARAMENTHANE SERIES 357 

when oils containing citronellal are heated with acetic anhydride this 
aldehyde is almost quantitatively converted into the acetate of iso- 
pulegol. Heating with sodium ethoxide^^^ converts isopulegol to 
citronellol and also decomposes it to acetone and methylcyclohexanol 
(3). Isopulegol is characterized by oxidation to the corresponding 
ketone, isopulegone/^^ which ketone yields an oxime melting at 121° 
(active) and 140° (inactive form). The acetate boils at 104°-105° 
under 10 mm. pressure. Isopulegol boils at 91° under 13 mm. pressure, 
dj^g„ 0.9154, nj^ 1.4729. 

Menthol, para-menthanol(3). This saturated alcohol is a com- 
mon article of commerce. Up to the present it has not been manu- 
factured synthetically but is obtained from oil of peppermint, par- 
ticularly Japanese peppermint. Peppermint has been under cultivation 
in Japan since about 900 A.D., and in Europe for a period probably 
equally long, and, as is usually the case with cultivated plants, there 
are numerous varieties and the number of distinct species is as yet 
an open question. Yet, with the exception of oil of spearmint ^^* 
which is characterized by considerable proportions of carvone, the 
various peppermint oils owe their characteristic flavor and aroma to 
menthol and the corresponding ketone menthone. The menthol occurs 
in these oils partly free and partly in the form of esters of acetic 
and other acids, and on chilling part of the free menthol crystallizes 
from the oil. The melting-point of menthol is 42.5°. According to 
F. E. Wright,^^* ordinary Lmenthol crystallizes in four different forms, 
a, p, Y and 6, only one of which, the a-form, is stable between zero and 
its melting-point, 42.5°. The other three forms are monotropic and 
have lower melting temperatures, i.e., 35.5° (5, 33.5° y, and 31.5° 8; 
all the unstable forms invert finally into the stable a-form. Previous 
work of Schaum,^'', Pope,^^' Hulett^^' and others had shown the 
existence of at least two unstable forms, which investigations were 
confirmed and extended by Wright. Menthol boils at 215°-216°, 

45° 
d. -jl-0.881 and when derived from peppermint is Isevorotatory. Pick- 



""Schimmel & Co. Semi-Ann. Rep. 1913 (2), 91. 

iMWallach, Ann. S65, 251 (1909). 

'" In the United States oil of spearmint is derived from Mentha viriUa (Mentlia 
spicata). The peppermint oil Industry is very fully described by Parry, "Chemistry 
of Essential Oils," Ed. 3, Vol. I, 205-231. 

'"J. Am. Chem. Boo. S9, 1515 (1917). 

"'Ann. SOS, 39 (1899). 

""■7. Chem. Soo. 15, 463 (1899). 

'"J. Phys. Chem. es, 667 (1899). 



358 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



ard and Littlebury ^'' made menthol by the catalytic hydrogenation 
of thymol, and by resolution of the brucine salt of the monomenthyl- 
phthalic ester Z.menthol was obtained [a]^ — 48.76° and d.menthol 

[a]_^ + 48.15°. A very large number of menthyl esters have been 

employed in the study of optical activity."® 

On oxidation, menthol is converted into the corresponding ketone 
menthone, p-menthane-3-one. The relationships between menthol 
and menthone have been made clear by the work of Pickard and 
Littlebury. A ketone of this structure should exist in two stereo- 
isomeric forms of the cis and trans type and these have usually been 
referred to as menthone and isomenthone.^*" Since each of these 
ketones contains an asymmetric 

H CHs 

\ / 

C 



H^C 



CH, 



H CH3 


V 


H,( 


/ \h. 


H,( 


: C = 

V 


C3H 


r\ 



H,C C = 

V 

/ \ 

H C3H7 

carbon atom, each should correspond to a pair of optically active 

isomerides, and when the carbonyl group is reduced to > C < tJ™ 

OH 

the possible number of optically inactive isomerides is increased to 
four and the number of optically active isomerides to eight. By the 
hydrogenation of thymol in the presence of catalytic nickel, which 
had been carried out by Brunei,"^ a mixture containing 60 per cent 
of "menthols," 30 per cent of menthones and 10 per cent of unchanged 
thymol is obtained. After removing the thymol, the alcohols were 
separated by phthalic anhydride, in the usual manner. The semi- 
barbazones of the mixture of menthones proved to have widely dif- 
ferent solubilities in alcohols, one nearly insoluble in cold alcohol 

"'■/. Chem. Soc. 101, 109 (1912). 
m. 227rml!filu^pe';-r^„''s?o-/'8?''lU.'''*^"' ^'^"""' * ^^^^^r.o.. J. Cl^. Soc. 
1905 "° ^*' nomenclature was used by Aschan, "Chemle d. alicykUschen Verblndungen," 
'^^Compt. rend. U,0, 252 (1905), et eeg. 



THE PARAMENTHANE SERIES 



359 



and melting at 217°, previously described by Wallach,"^ and a more 
soluble one melting at 158°. Fractional crystallization of the hydro- 
gen phthalate esters yielded two pure products, one melting at 177° 
and one melting at 130°. The ester melting at 177° on hydrolysis 
yields an optically inactive menthol melting at 51°, "neomenthol," 
previously isolated by Beckmann."^ Hydrolysis of the menthyl 
hydrogen phthalate melting at 130° yields an inactive menthol melt- 
ing at 34°, which can be resolved, by means of the cinchonine or 
brucine salt, to ordinary i.menthol, melting-point 43°, and d.menthol, 
melting-point 43°. These relations are evidently parallel to and of 
the same nature as those between the borneols, isoborneols and cam- 
phors (q.v.). The following diagram summarizes the findings of 
Pickard and Littlebury, 

Thymol, 

I I 4 



menthone 

semicarbazone 

M.-P. 158° 



isomenthone 

semicarbazone 

M.-P. 217° 

\ 



i-Menthol, M.-P. 34° 
(hydrogen phthalate, M.-P. 130° 



z-neo-menthol, M.-P. 67° 
(hydrogen phthalate, M.-P. 177°) 



1-menthol 
M.-P. 43° 
[a] —48.76° 



D 



\ 



\ 



\ 



d. menthol d. neomenthol 
M.-P. 43° oil 
[a] +48.15° [a] +19.6° 
D D 
\ / 

.by. ^ \/ 

oxidation /\ 
\ / \ 

/-menthone d-menthone 


1 . neomenthol 

oil 
[a] — 19.6° 
D 

/ 

/ 



By the hydrogenation of pulegone by the Sabatier and Senderens 
method, Haller and Martine"* obtained two menthols which evi- 

"2 Ann. t6i, 272 (1908). 
'"J. vraU. Chem. (2) 55, 30 (1897). 

'"Compt. rend. 11,0, 1298 (1905). Haller's ;8-pulegomenthol Is probably d-neo- 
menthol and his a-pulegomenthol evidently belongs to tbc isomenthol series. 



360 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

dently are identical with Z.menthol and d.neomenthol described above. 
By electrolytic reduction of menthone in solution in about equal parts 
of 94 per cent alcohol and 75 per cent sulfuric acid a yield of 25 per 
cent of the theory of menthol has been reported."^ Beckmann "^ has 
described an isomenthol melting at 78°-81°, obtained by the reduction 
of a specimen of d.menthone made by inverting i.menthone by 90 per 
cent sulfuric acid. » 

By passing synthetic menthol (from thymol) over copper at 300°, 
it is converted to menthone.^*' 

Substituted menthols of the general constitution indicated below 
have been made from menthone by the Grignard reaction, and by 
zinc and alkyl halides, 

CH, 



CHo — CH — CH 



OH 
CH, — CH — C< 

I R 

CHj — CH — CHj 

Magnesium cyclohexyl bromide ^" gives the cyclohexyl derivative 
melting at 92° together with a cyclohexylmenthene boiling at 265°. 
Methyl iodide and magnesium give chiefly the methyl tertiary alcohol, 
but ethyl iodide and magnesium or zinc yields chiefly a hydrocarbon 
C12H22."* Allyl iodide and zinc ^*^ give the expected allyl derivative, 
boiling-point 246°-252°. 

Hallers' reaction has been employed by Boedtker ^^^ for the prepa- 
ration of alkyl derivatives of menthone in which the alkyl groups are 
in position 2. Thus ethyl iodide and sodium amide, reacting with 
menthone, give 2-ethyl-p-menthanone(3) from which by reducing 
in moist ether by sodium the 2-ethyl menthol was made. The methyl, 
7i-propyl, isoamyl arid benzyl derivatives were prepared in the same 
manner. 

The stereochemistry of substances such as menthone and menthol 
is somewhat involved and has led to some confusion in the description 

"" Matsui, J. Soo. Oliem. Ind. mi, 162A. 

"'Ber. iB, 846 (1909). 

""Murat, J. Ohem. Soo. Ais. 100 (1), 890 (1911). 

i«Vaniii, J. Chem. Soc. Ale. 100 (1), 474 (1911) ; J. Buss. Phya.-Chem. Soo. U, 
1068 (1912). 

"'Saytzeff, J. CUem. Soo. Ais. 100 (1), 474 (1911); Eyachenko, J. Buss. Phyt.- 
Ohem. Soc. 1,1, 1695 (1909). 

"»B»I!. Soo. cMm. (4) tt, 360 (1915) ; Haller, Compt. rend. 156, 1199 (1913). 
Dlmetliylmentlione » dlmethylmenthol, a liquid bolUne at 245°-247°. 



THE PARAMENTHANE SERIES 361 

of these substances and their derivatives. It should be pointed out 
that aside from cis-trans relationships discussed above, menthone pos- 
sesses two and menthol three asymmetric carbon atoms. 



CH3 

HjC CH2 


CH3 

i/ 

H^C CH, 

1 1 H 
H,C *C< 

1 H 
CH 

/\ 

CH3 CH3 


H^C C = 
CH, CH„ 



Theoretically, therefore, menthol should be capable of existing in 
four spatial configurations of which each would have two optical 
antipodes and one racemic form. Kursanov ^", finds that when ordi- 
nary menthol is treated with phosphorus pentachloride, in benzene 
solution, a mixture of menthyl chlorides is obtained, which are of 
markedly different stability to caustic alkali. The stable chloride 
reacts with magnesium in ether to give a menthene, para-menthane, a 
crystalline dimenthyl (CioHiJ, melting at 105°-106°, [a] —51.42° 

(which is identical with the dimenthyl obtained by the action of 
metallic sodium on this chloride) and when the menthyl-magnesium 
chloride thus formed is treated with carbon dioxide, a crystalline 
menthanecarboxylic acid results. The unstable menthyl chloride 
yields a liquid menthanecarboxylic acid and the crude menthyl 
chloride consequently must contain two stereoisomers. Kursanov 
concludes that only the carbon atom (3) attached to the hydroxyl 
group in the original menthol is inverted by the reaction. When 
^.menthone, corresponding in spatial configuration to ordinary Z.men- 
thol, is treated with 90 per cent sulfuric acid, it is partially inverted 
to d.isomenthone and according to Beckmann ^^^ the asymmetric car- 
bon atom involved in the change is the one to which the isopropyl 
group is attached. 

When the potassium derivative of menthol is heated with phenyl 
bromide or iodide the products are benzene and menthone, but in the 

'"J. ahem. Soc. AT>e. 108 (1), 420 (1915). 
^Ber. *e, 846 (1909). 



362 CHEMISTRY OF THE NON-BEN ZENOID HYDROCARBONS 



presence of finely divided copper the reaction gives a high yield of 
menthylphenyl ether. When this ether is heated with concentrated 
hydrochloric acid to 170° this ether is isomerized to menthyl phenol. 
Menthol is relatively very stable and its esters can accordingly be 
easily prepared. The benzoate, melting-point 54°, can be prepared 
by heating with benzoic acid in autoclave to 170°. Although the 
benzoate cannot be made by mixing the alcohol with benzoic and 
sulfuric acids, the phenyl acetate and phenyl propionate can be made 
in this way.^^^ In studying the action of esters on magnesium alkyl 
halides Stadnikow^^* found that magnesium menthyl iodide reacts 
with ethyl acetate to give a practically quantitative yield of menthyl 
acetate; ethyl propionate gave an 80 per cent yield of menthyl pro- 
pionate and ethyl benzoate gave 64.6 per cent menthyl benzoate. 
Tschugaeff ^^^ prepared a series of menthyl esters by acting upon men- 
thol by various acid chlorides in slight excess. A great many esters 
of menthol have been employed in the study of optical activity. The 
following table gives the boiling-point or freezing-point of a number 
of menthyl esters. 

Ester Melting-Point 



Formate 



Boiling-Point 


Density 






20° 


98. ° 


{15min.) 


0.9359 
4° 


108. " 




0.9185 " 


118. ° 




0.9184 " 


129. ° 




0.9114 " 


141. ° 




0.9074 " 


153. ° 




0.9033 " 


165. ° 




0.9006 " 


175. ° 




0.8977 " 



Acetate 

Propionate 

Butyrate 

Valerate 

n.Hexoate 

n.Heptoate 

n.Octoate 

Dimenthyl oxalate 67. °-68.' 

Dinienthyl succinate €2. ° 

Month vl-H-phthalate 110. ° 

Dimenthy] phthalate 132. ° 

Dimenthyl muconate 168. " 

Dimenthyl (3, y-hydromuconate 79. ° 
Dimenthyl, a, 3-hydromuconate 83. ° 

Dimenthyl adipate 61. ° 

Menthyl piperate 83. ° 

Mfcnthyl 0, v-hydropiperate 

Menthyl a, |3-hydropiperate 

Dimenthyl malonate 62. ° 

Menthyl glutarate 

Menthyl pimelate 

Menthyl suberate 

Menthyl azelate 

Menthyl sebacate 

Menthyl benzoate 54.5° 

"»Senderens & Aboulenc, Compt. rend. 1S5, 1254 (1912). 

1" J. Ruaa. Phys.-Chem. Soc. p, 1113 (1&15) ; J. Chem. Soc. Ais. 108, 975 (1915). 

"»Ber. 31, 360 (1898). 



263. ° 
270. ° 

24()-3° 



(25mm.) 



(20mm.) 



248. °-252.°(20mm.) 
257-9' (20mm.) 

254.6° (20mm.) 

256. °-258.°(20mm.) 



THE PARAMENTHANE SERIES 363 

Ester Melting-Point Boiling-Point Density 

20° 

Menthyl phenylacetate 205.5° (25mm.) 

Menthyl phenylproprionate . . . 28.5° 216. ° (25mm.) 

Menthyl acetoacetate 36. ° 154. ° (10mm.) 

Menthyl propyl acetoacetate 162. ° (8mm.) 

Menthyl phenyl acetoacetate . . 69. ° 131-3° (0.1mm.) 

The freezing-point curves of menthyl mandelate indicate "the 
existence to a considerable extent, of undissociated racemate in the 
liquid state." "» 

Ketones of the Para-Menthane Series. 

There are two saturated ketones and one known diketone derived 
from para-menthane. 

Menthone: The stereo isomers of menthone have been discussed in 
connection with menthol. Ordinary menthone isolated from oil of 
peppermint and regenerated from the semicarbazone (melting-point 
184°), boils at 208°, has a density 0.894, and refractive index 1.4496. 

The oxime of menthone is of interest on account of the fact that 
it undergoes a Beckmann rearrangement,^^' with rupture of the cyclo- 
hexane ring, to give menthoneisoxime (by treating with concentrated 
sulfuric acid). By dehydrating agents the isoxime yields mentho- 
nitrile, which on reduction yields menthonylamine and from this 
amine, by heating the nitrile with water, menthocitronellol is formed, 
as indicated in the following outline, 

CH3 CH3 CH, 



,C=N.OH 



■H,0 



i-iH 



c=o 

^C— r^H CH, 



CN 



CH.NH, 



C(CH4 



XH 

11/ V 



CH^OH 

menthocitronellol 



'"Findley & Hlckmans, J. Chem. Soc. 91, 905 (1907). 
'" Wallach, Ann. i96, 124. 



364 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



The reduction of Z.menthone oxime yields a single menthylamine, but 
by heating menthone with ammonium formate a mixture of crystalline 
d. and t.formylmenthylamines CioHigNH.COH is formed, which can 
be separated, and which yields two isomeric menthylamines of the 
cis and trans types and from which a series of isomeric derivatives 
have been prepared.^^' When menthone oxime is heated to 220° with 
caustic potash "' thymol is formed together with about 45 per cent 
of the open chain acid, (CH3),CH. (CHJ3CH(CH3) .CH^CO^H. 

Menthone has been synthesized by Kotz ^^'' from p-methyl-a-iso- 
propylpimelic acid in two ways (1) distillation of its calcium salt 
with soda lime, and (2), intramolecular condensation of its ester by 
sodium ethoxide after the manner of the acetoacetic ester condensa- 
tion, 

CHo CM, 



CH, 



Ah- 



CH2C02li 



CH^ — CH- 



CO,R 



CHj — CH — CHj 



CH, _ CH — CO 



i, 



H, 



C,H, 



Another synthesis of menthone by Wallach and Churchill ^°^ is of 
interest. Reformatsky's reaction was employed for the condensation 
of l-methylcyclohexane-4-one with a-bromoisobutyrate. The unsatu- 
rated acid, derived from the resulting ester, yields A*(*)-p-menthene. 
Substances containing a double bond in this position rearrange under 
the influence of dilute acids, the double bond shifting to the ring, as 
in the case of terpinolene. In the present instance i.A^-p-menthene 
is formed from which i.menthone was synthesized. 



CH, 




CH, 



CH, 



+ Zn 







'•» Wallach, Ann. SiS, 67 ; Si6, 259. 
'" Wallach, Ann. S89, 185. 
^"Ann. SSt, 209. 
"M»m. SeO, 26 (1908). 





OH 

.C<r;CO,H 
erf, CH3 



CHr^CH, 



THE PARAMENTHANE SERIES 
CH, CHj 



365 



+ dil.acid 



h^-p-menthene 




+ N0C1 
> 




-^ 






H. 




N.OH 



Cl 
C,H, 




C3H, 



H 

^ nitrosochloride A^-p-menthenone 



to 



H 



C,H, 

i.-menthone 



In a study of the chlorination and bromination of cyclic ketones 
Kotz ^°^ finds tiiat tiie lialogen always substitutes in an ortho position 
to the carbonyl group. In the case of menthone, 4-chloro or 4-bromo- 
menthane-3-one are obtained, from which aniline or aqueous potas- 
sium carbonate followed by dehydration by oxalic acid, yields A*-p- 
menthenone. Similarly carvomenthone (p.menthane-2-one) yields 
l-chloromenthane-2-one. Wallach has studied the conversion of 
2.4-dibromomenthone to the cyclopentane hydroxy-carboxylic acid. 
(Cf. "Rearrangements.") 

Oxidation of menthol by chromic acid^°^ gives the ketonic acid 

(CH3)2CH.C0.CH2CH2CH.CH,C02H. The same acid is obtained 

I 
CH3 

by treating menthone with amyl nitrite and hydrochloric acid and 
hydrolyzing the nitrosomenthone thus form.ed.^^* This ketonic acid 
is also formed by the air oxidation of menthone, in sunlight. Sun- 
light in the absence of oxygen, however, decomposes menthone giving 
a decoic acid and an aldehyde "''° which is different from Wallach's 
menthocitronellaldehyde, i. e., 

'•'Ann. S97j 1 (1911). Kotz effects this halogenatlon by diluting the chlorine or 
bromine with air and adding water and calcium carbonate to the ketone, 
'"Beckmann, J. Ohem. Soe. Aia. 1896 (1), 312. 
'"Baeyer & Oehler, Ber. 29, 27 (1896). 
■"Ciamlclan & Silber, Ber. ie, 1510 (1909). 



366 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

(CH3),CH.CH CH.CH^.CHCCHa) .CH,CHO."= 

Oxidation by potassivun permanganate yields oxomenthylic acid (1) 
and P-methyladipic acid, and Caro's reagent gives a lactone of di- 
methyloctanolic acid (2), 

(1) (2) 

CH3 CH3 

CH, CH CH, CH, CH CH, 



III >^^ 

CH^ CO CO^H. CH, CH 

I I 

CH, — CH — CH, CH, — CH — CH3 



Menthone can be alkylated by Hallers' reaction ^^° (sodium amide 
and alkyl halide), the alkyl group being substituted in position (2). 
One or both of the hydrogen atoms in the CHj group (2), can be 
replaced by alkyl groups/'^ With hydrazine hydrate, menthone 
reacts to form menthylidene hydrazine, which on heating with caustic 
potash loses N, and gives p-menthane."^ Menthone condenses with 
formic acid esters (amyl formate and sodium) to form oxymethylene 
menthone. Benzaldehyde reacts slowly in the presence of alkalies, 
but rapidly with hydrochloric acid to form benzylidenementhone 
(hydrochloride melting at 140°). Reduction of this compound yields 
benzylmenthol, M.-P. 111°-112°. 

Menthone,"^ like camphor, carvomenthone and cyclohexanone, 
acts as a catalyst in the combination of sulfur dioxide and chlorine 
to form SOjCl^. 

The optical inversion of Z.menthone by sodium ethylate has been 
suggested as a means of determining the per cent of i.menthone in 
pine oils.^'" 

Menthone reacts normally in the Reformatsky reaction,^'^ with 
bromacetic ester and zinc, to give the ester of mentholacetic acid, the 
free acid readily losing water and carbon dioxide to give homomen- 
thene CnH^o, boiling at 186°-187°. 

""Boedtker, Bull. soc. chim. n, 360 (1915). 

'" Ealler, Compt. rend. 1S6, 1199 (1913). 

•MKlzhner. J. Rues. Phys. Uhem. Soc., U, 1754 (1912) 

'»»Cusmano, aazz. Chem. ItaZ. m (2), 70 (1920). 

"»Gruse & Acree, Science U, 64 (1916). Tubandt lAnn. sm, 284 (19101 shows 
that the rate of Inversion of menthone by acids Is not proportional to the H Ion con- 
centration. The speed of Inversion Is greatly retarded by water 

"1 Wallach, Ann. S5S. 313. 



THE PARAMENTHANE SERIES 



367 



H3C 



Ah 
/ \ 



CH, 



H,C 



H,C 



CH3 



CH, 



\ / 
CH 



C = H,C 



C< 



OH 



-^ homomenthene 



C3H7 



\ / CH^CO^H +HjO + CO, 
CH 

I 
CsHj 



Normal Menthone, l-methyl-4-propylcyclohexane-3-one. This 
ketone, synthesized by Wallach,^" does not smell like ordinary men- 
thone, illustrating the marked influence of slight differences of con- 
stitution on odor, noted also in the case of unsaturated ketones similar 



HjC 



CH3 



CH, 



H,C C = 

\ / 
CH 

I 
CHjCHjCHs 

to ionone and also in the case of artificial musk when the tertiary 
butyl group in Musk Bauer is replaced by similar alkyl groups. Nor- 
mal menthone boils at 215°-217°. 

A^-p-Menthenone, has been found in Japanese oil of peppermint ^^' 
and in one of the Cymbopogon grass oils, C. senaarensis, Chiov."* 

19° 
It boils at 235°-237°, density — 0.9375, [a]^ 1.4875. It forms a 

very sparingly soluble semicarbazone melting at 212° and yields a 
dibromide which, by the action of aqueous caustic potash and heat, 
is converted almost quantitatively to thymol. 

Piperitone: This menthenone occurs in the essential oils from 
several species of eucalyptus, particularly in E. dives, the oil of which 
contains 40 to 50 per cent of this ketone. It occurs associated with 
the corresponding alcohol "piperitol." As this oil is available in large 

"'Chem. Zentr. 1915 (2), 824 

"' ScMmmel & Co. Semi-Arm. Rep. 1910 (2), 79. 

"' Roberts, J. Ohem. Soc. MIS, 1465. 



368 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

t 

quantities it is probably only a question of a short time before men- 
thol, and possibly thymol, will be manufactured from this material; 
in fact. Smith and Penfold"" have reported that with hydrogen and 
catalytic nickel menthone is formed almost quantitatively. 

The constitution of piperitone is not definitely known. Smith 
and Penfold suggest that it may prove to be identical with A^-p- 
menthenone. They describe it as boiling at 229°-230° at 760 mm. or 

D 

106°-107° at 10 mm., d^^o 0-9348, [a] j.^— 40.05° and n_ 1.4837. It 

forms a semicarbazone melting at 219°-220° and an oxime melt- 
ing at 110°-111°. The most characteristic derivative is the 
compound formed with benzaldehyde, benzylidene d.Z.piperitone, 
CioHj^O . CH . CsHb, melting at 61°. By oxidation, by boiling with 
ferric chloride in dilute acetic acid, a yield of thymol corresponding 
to 25 per cent of the theory was obtained. 

Pulegone, A*-°(')-p-menthenone: This ketone occurs in the essen- 
tial oils of Mentha pulegium and Hedeoma pulegioides and imparts 
its characteristic odor to oil of pennyroyal. Its physical properties,^'* 
are, boiling-point 224° (750 mm.) or 93°-94° at 869 mm., d 0.9405, 

20° ^ 

[a]j^ 20° 28' and n_- 1.48796. 

By reducing energetically with nascent hydrogen "'' menthol may 
be obtained. When reduced by sodium and alcohol, about 30 per 
cent of a yellow resin, CjoHj^Oa, is formed,"^ a similar product being 
formed when employing the aluminum-mercury couple.^'* Paolini 
has separated the alcoholic reduction products (by sodium and alco- 
hol) and has identified ordinary /.menthol of peppermint, a solid 
d.menthol melting at 88°-89°, boiling-point 214°, [a] — 11.7°, and 
Z.pulegol. 

Pulegone is of special interest as furnishing an example of the 
conversion of the cyclohexane ring into the cyclopentane ring. When 
pulegone dibromide is heated with sodium methylate in alcoholic solu- 
tion pulegenic acid results, and when pulegenic acid is oxidized by 
permanganate a glycol is formed which then forms a lactone; by a 
pinacoline rearrangement the cyclopentane ring is enlarged to give 
CO2 (loss of 1 carbon atom) and pulenone, CoHibO.^'" Pulegenic 

"•J. Proo. Boy. 8oc. N. S. W. H. 40 (1920). 

"" Gildemelster, "Die Aetherlschen Oele," Ed. 2, Vol. I, 463. 

"'Beckmann & Pleifisner, Ann. i62, 30 (1891). 

"•Paollnl, J. Chem. Soc. Ata. 19X0 (1), 171. 

"•Harries & Boeder, Ber. SS. 3357 (1899). 

>•» Wallach, A7m. Si9, 82 ; 876. 154. 



THE PARAMENTHANE SERIES 



369 



acid also decomposes with loss of one molecule of carbon dioxide to 
give pulegene, CjHi,,. 




cA H,6Q,.(z:i) 
>C0 — 

C-C(-CH, 

in ^"3 



pulenone 



The ring in pulenone can be broken by converting the oxime into the 
isoxime, in the same manner as menthone, described above. Thus, 
heating with acetic anhydride gives the nitrile of a nonylenic acid, 



CHj 



CH, 



CH3 




J=NOH CH, 




^ ' CH, CH3 

pulenoneoxime isoxime 

>"WaUacb, Aim. it9, 100 (1903). 



C=0 CH, 

NH (C;^OH 



CH, 
9 Hi CHj 



CONHi CH 



CONHi 



a( CH, 



A nonylenic 
CH, CH, acid^'^ 
nitrile 



370 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Pulegene yields a nitrosochloride, melting-point 74° to 75°, which 
on decomposing with alkali yields the oxime of a ketone, pulege- 
none,^'^ 



H,C 



H,C 



CH3 

CH 



CH 



•C 



CH« 



H,C 



H,C 



CH 



C = N.OH 



C— CI 



I 



CH(CH3), CH(CH3), 

pulegene nitrosochloride 



H,C 



CH3 

1 
CH 



C = N.OH 



HC==C 

CH(CH3), 
oxime of pulegenone 



The corresponding saturated ketone, l-methyI-3-isopropylcyclopen- 
tane-2-one, is identical with camphorphorone. 

When a halogen, chlorine or bromine, is introduced into a ketone, in 
the ortho position to the carbonyl group, the resulting halogen deriva- 
tive is unstable. Kotz ^'^ noted that the bromo ketones are particu- 
larly unstable, fuming in the air and decomposing rapidly when 
warmed. Wallach ^'* showed that the dihalogen ketones react rapidly 
with aqueous alkali at room temperature and that cyclohexanones 
could be converted into cyclopentanones by evaporating the alkaline 
solution, thus obtaining an oxy acid which on distilling with lead 
peroxide and sulfuric acid yields the pentanone. 




'■N^' 



M 
'OH 



- 8 H,/ 



CH, 



-CH. ° 



-C=0 



OH 



H,C- 



'8= Wallach. Ann. 327. 133 (1903). 

^"Ann. J,00, 47 (1913). 

"*Nachr. Ooettingen 1915, 244; J. Chem. Soc. Aia. 110 (1), 487 (1916). 



THE PARAMENTHANE SERIES 371 

By a similar series of reactions niethylcyclohexane-2-one gives 
1 - methycyclopentane - 2 - one ; 1 - methylcyclohexane - 3 - one gives 
l-methycyclopentane-3-one ; the ketone 1.3-dimethylcyclohexane-5- 
one yields 1.3-dimethylcyclopentane-2-one; from 1 . 3 . 3-trimethyl- 
cyclohexane-5-one there was obtained 1.3.3-trimethylcyclopentane- 
5-one. 

CH3 CH3 

CH CH 

/\ /\ 

H^C C = H,C C = 

I T — ^ T I 

HjC CI12 HjC CI12 

C 

CH. CH. 



'■s 



H 



CH c: 

/\ /\ 

HjC CHj HjC CH2 

ii,c C = H,C — c = o 

\/ . 

c 

CH3 CH3 

CH CH 

/\ /\ 

H^C CH2 = C CH2 

I I CH3 > I I CH3 

= C C< H^C C< 

\/ CH3 CH3 

c 

Menthone similarly gives l-methyl-3-i8opropylcyclopentane-2-one 
(dihydrocamphorphorone) , and carvomenthone gives the same 
oxidation products. Menthone can also be converted into pule- 
genone by slightly modifying the above procedure. Wallach finds 
that menthone dibromide first yields two isomeric substances 
CioHijOz, one of which proved to be buchu camphor. 



372 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 




menthone 



C3H, 
buchu camphor 



The dibromide of buchu camphor, when treated with aqueous alkali, 
gives an oxy-acid which on distillation yields pulegenone.^"* 

The hydrazine derivative of menthone yields para-menthane when 
heated with caustic potash. Pulegohydrazine, however, yields the 
bicyclic hydrocarbon carane, under these conditions.^*" 



CH, 




CHf CH3 
pulegone 



CH, 




■um. 



CK 



:^~~x, 



CH, 




carane 



This substance, also called diosphenol, is found in nature in the 
essential oil of buchu leaves. It is of considerable interest in that 
its chemical behavior gives no indication of the existence of the tau- 
tomeric diketo form, analogous to camphor quinone, although its for- 
mation from the dibromine substitution products of both menthone 
and carvomenthone indicate that the diketone must be an intermediate 
product.^*' 

"'Wallach, J. Chem. 800. Ahs. 114, 544 (1918). 
'MKizhner. J. Rusa. Phya.-Chem. Soc, iS, 1132 (1911). 

"' Cusmano, J. Chem. Soc. Ais. 1911, (1), 303: AtH accad. Uncei (5), U. 520 
(1915). 



CH. 



H,C 



CH 



CHBr 

I 



I 
HjC C = 

C— Br 



THE PARAMENTHANE SERIES 
CH3 

in 

H,C CH.OH 

> I I 



373 



HC C = 

V 



CH3 
C— Br 

Hfi C = 

I I -^ 

Hfi CHBr 

\/ 
CH 



A, 



H, \ 



HC 



CH3 
C 



^H,C 



CH3 
CH 



C: 



CH3 

c 

/\ 

H,C C- 



OH 



/ 



A 



H,C C = H^C C = 

\/ \/ 

CH CH 



C = 



C3H7 



CgH^ 



I 



H,C CH.OH 
CH 



CjHj C3H7 

Carvone, A°''(^>-p-menthadiene-2-one. The constitution of car- 
vone and much of the chemical behavior has been shown above, in 
connection with the discussion of limonene and the terpineols. Car- 
vone is of further interest, however, on account of its conversion to the 
cylcoheptane derivative eucarvone, and derivatives of the bicyclic 
carane series. Baeyer^'^ showed that the hydrobromide of carvone 
gave, by loss of HBr, an isomeric ketone which he called eucarvone. 
Baeyer originally suggested that the constitution of eucarvone was 
that represented as I, below, but Wallach was able to show that 
eucarvone is a cycloheptane derivative II, and that Baeyer's structure 
for eucarvone is in fact possessed by an intermediate product in the 
reaction. Wallach "" represents these reactions as follows, 




'"Ber, «7, 810 (1894). 
'"Ann. aS9, 94. 



eucarvone 



374 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Baeyer regarded dihydro and tetrahydroeucarvone as cycloheptane 
derivatives and showed that the completely reduced tetrahydroeucar- 
vone was broken up by oxidation to p, p-dimethylpimelic acid which 
in turn yields 1 . l-dimethylhexane-3-one, in the usual manner: 

CH, CH, 



cJo 



H,C C = H,C CO,H CO,H 






H,C CH^ > H^C CHa > H^C CO^H. 



H,C C(CH3), H,C C(CH3), H,C CH, 

HgC C (CH3) 2 

tetrahydro-eucarvone, | 

(1 .^.4-tri-methylcyclohe'ptane-2-one,) j, 

H^C C = 

I I 

HjC CH, 

H,C C(CH3)3 

dimethylcyclohexanone 

Eucarvone boils at 85°-87° (12 mm.); its density at 21° is 0.949 

20° 
and n — — 1.5048. It yields a semicarbazone melting at 183°-185° 

and a benzylidene derivative melting at 112°-113°. The oxime melt- 
ing-point, 106°, may be reduced by sodium and alcohol to dihydro- 
eucarvylamine and, by more energetic reduction, to the saturated 
amine CioHig.NHj. Reduction of the oxime by hydrogen and pal- 
ladium yields the dihydro and tetrahydrooximes, melting at 122°-123° 
and 56°-57° respectively. The alcohol, tetrahydroeucarveol [1.4.4- 
trimethylcycloheptanol(2)], a product of reduction by sodium, boils 
at 216°. 

When carvone is reduced by nascent hydrogen the double bond 
next to the CO group is first reduced, dihydrocarvone being A'(°>-p- 
menthene-2-one. Wallach, Albright and Klein"" have made the 
interesting observation that when the CO group is converted to the 

^A.nn. iOS. 74 (1914). 



THE PARAMENTHANE SERIES 375 

oxime and the resulting carvoxime then reduced by one mole of 
hydrogen, in the presence of Paal's colloidal palladium, the double 
bond in the side chain is first reduced. In this case the oxime of 
carvotanacetone (A''-p-menthene-2-one) is formed. Vavon "^ also 
showed that, in the presence of platinum black (Willstatter's method) , 
carvone itself was reduced first to carvotanacetone. This ketone is 
also formed by the rupture of the three carbon ring in thujone, effected 
by heating.^'^ 

Carvone boils at 230° and occurs in d. and I. forms [a] ± 60° 

D 
Carvone, dihydrocarveol and limonene are the principal constituents 
of oil of caraway, used in making the liqueur "kiimmel"; carvone is 
also an important constituent of dill and. spearmint oils. Like citral 
and other substances containing the group — CH = CH — CO — 
carvone reacts to form an unstable bisulfite compound from which 
carvone can be regenerated by alkali, and also forms stable salts of 
the dihydrosulfonic acid derivative, from which the ketone cannot be 
regenerated. Carvone forms a crystalline compound with hydrogen 
sulfide, (CioHi40)2.H2S, from which carvone can be regenerated.^" 
The bisulfite method is preferable for the isolation of carvone. For 
its identification, the following derivatives are characteristic: the d. 
and J.oxime, melting-point 72°, i-carvoxime melting-point 93° (when 
too great an excess of hydroxyamine is employed a compound of car- 
voxime and hydroxylamine, CioHi^NOH . NHjOH., melting at 174°- 
175°, is formed. It will be of interest to note that in the preparation 
of carvoxime a Walden inversion occurs, d. carvone yielding i.carvox- 
ime and Z.carvone yielding dcarvoxime. With phenylhydrazine car- 
vone forms a phenylhydrazone melting at 109°-110° and semicarbazid 
forms a semicarbazone melting at 162°-163° in the case of d. or 
i.carvone but i-carvone yields the racemic semicarbazone melting at 
154°-156°. The original ketones are readily regenerated by warm- 
ing the semicarbazones with oxalic acid. 

Carvoxime rearranges to amido thymol when treated with con- 
centrated sulfuric acid, 

'"Oompt. rend. 15S, 68 (1911). 

■"Semmler, Ber. Srt, 895 (1894). 

'" Wallach, Awn. SOS, 224 (1889) ; Claus & Fahrion, J. prakt. Chem. (2), S9, 365 
(1889). The product from d. or I. carvone melts at 210°-211° ; that from i. carvone 
melts at 189°-190°. It is dlmolecular in benzene but monomolecular in glacial acetic 
acid. Deussen, ArcJi. Pharm. SSI, 285 (1883). 



376 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 
CHg CHj CHj 

c c c 

HC C = N.OH. HC C = N.OH 



CH 



HC CH2 

Y 



HC C — NH, 



HOC CH 

Y 



CH, 



C 



CH, 



CH, 



CH 



CH, 



CH 
/\ 

CHj CHg 

amidothymol 



By the Grignard reaction, using methyl-magnesium iodide, a hy- 
drocarbon, CnHie, results.^'* Klages regards this hydrocarbon as 
2-methyl-A^'°-^(°)-menthatriene on account of the ease with which it 
is ispmerized to 2-methylcymene by boiling with a 2 per cent solu- 
tion of hydrogen chloride in acetic acid.^^° The reaction is worth 
noting as one of the many instances of the migration of a double bond 
from a side chain to the cyclohexadiene nucleus to give a benzene 
derivativ-e. 




CHf "^H^ 



CH 



-\ 



carvone 2-methylcarveol 



CH3 Ci^ CHj GHj 

2-methylcymene 



When dihydrocarvone is similarly treated, 2-methyldihydrocarveol 
results which can be decomposed directly, or better by converting to 
the corresponding chloride, to 2-methylhomolimonene, or hydrated 
by the action of alcoholic sulfuric acid to 2,8-dihydroxy-2-methyl- 
menthane."^ The main product of the action of magnesium-benzyl- 

'"Eupe & Liechtenhan, Ber. S9, 1119 (1906). 

"'Ber. S9, 2306 (1906) ; Eupe & Emmerich, Ber. il, 1393 (1908). 

'»» Eupe & Emmerich, loc. cit. 



THE PARAMENTHANE SERIES 



3^7 



chloride is a ketone, 6-benzyl-A*-p-menthene-2-one, [or 6-benzyldi- 
hydrocarvone] , melting at 73°. The a-naphthyldihydrocarvone, 
melting-point 150°, was prepared in the same manner.^" 

Semmler ^°' has employed the reaction of carvone with magnesium- 
isoamylbromide for the synthesis of a hydrocarbon of the sesquiter- 
pene class. (When ether is used as a solvent in the Grignard reac- 
tion, instead of benzene, a large proportion of isoamyldihydrocarvone 
is formed.) The synthetic sesquiterpene thus prepared is monocyclic, 
contains three double bonds and has been named isoamyl-a-dehydro- 
phellandrene by Semmler. 

Carvone is isomerized by sunlight forming a resin and a crystal- 
line camphor-like substance, melting at 100°, which Ciamician and 
Silber named carvone-camphor.^°° This substance has been carefully 
investigated by Sernagiotto,^"" who showed that, in sealed tubes, the 
sunlight causes both double bonds in carvone to combine to form a 
four-carbon ring. Ciamician had suggested that the isomerization of 
carvone resembled that of the condensation of two molecules of cin- 
namic acid to form truxillic acid. The work of Semagiotto shows 
that the chemical behavior of the substance may be indicated as 
follows, 

CHo CH CHo 



-CH3 



CH==C C = 



:;h3 

carvone 
CH, — CH CH„ 



i 



■CH, 



CH C C = 



CH, — C = 
C — CH3 

/ CH, 

/ I 
CH C CO,H 



CH3 

carvone-camphor 



CH3 

ketonic acid 



'"Rupe & Tomi, Ber. 47, 3064 (191i) ; Zellnakl, German Pat. 202,720 (1909). 

>"Ber. 50. 1838 (1917). 

'"Ber. a, 1928 (1908). 

'»»Atti aecad. Lincei 2S (2), 70 (1914) ; 26; 238 (1917). 



m CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Carvone camphor melts at 100°, boils at 205.5°, forms an oxime melt- 
ing at 126°-128° and a semicarbazone melting at 239°. 

Like menthone, pulegone and camphor, carvone can be condensed 
with aniline by heating with aniline in the presence of a little zinc 
chloride [or ZnClg. (C6H5NH2)2]. The resulting carvoneanil is 
an oil.2°i 

It is pointed out by Lapworth ^"^ that when the double bond in the 
ring of carvone combines with hydrogen cyanide, the resulting 



CH3 

C 

/\ 
HC C = 



H,C 



+ HCN- 



CH3 







CH, 



CH 

i 

CH, CH„ 



H,C 



CH, 

w 

CH 



i 



CH, CHo 



cyanodihydrocarvone should theoretically be capable of existence in 
four stereoisomeric forms having three asymmetric carbons, as shown. 
By employing Aschan's scheme of representing the section of the 
ring plane by a line, these four isomerides can be represented as fol- 

CH3 

/ 

lows, Pr representing the group — C 

Pr Pr 



Pr 

CN 
CH, 



CH, 



CN 



CN 
CH, 



CN 



Pr 



CH, 



(1) (2) (3) (4) 

The ordinary form, melting-point 93.5°-94.5°, is obtained in excellent 
yields when an alcoholic solution of carvone and potassium cyanide 
is treated with acetic acid in amounts which insure the presence of a 



M'Eeddelien & Meyn, Ber. 53, B. 345 (1920). 
'•"J. Chem. Soc. 89^ 946 (1906). 



THE PARAMENTHANE SERIES 



m 



little excess potassium cyanide. When the addition of hydrogen 
cyanide takes place in hot solutions a different crystalline isomeride 
is produced in considerable quantity which has a rotatory power in 
the opposite sense to that of the substance described above [a]-^ — 39°, 

instead of [a]_^ -f 15.4°. The Z.isomeride exhibits slight mutarota- 

tion and Lapworth considers that the four isomerides may be divided 
into two pairs, the two members of each pair being dynamic isomer- 
ides at ordinary temperatures.^"' 

PerilUc aldehyde, occurring in the essential oil of Perilla nan- 
kinensis, has been found to contain two double bonds in the A"'^*") 
positions, as in limonene. By reduction with zinc dust and acetic 
acid an alcohol is produced which is identical with the so-called dihy- 
drocuminic alcohol previously found in gingergrass oil. Its constitu- 
tion was shown by converting the CHjOH group of perillic alcohol 
to the chloride which on reducing by sodium and alcohol gave Z.limo- 
nene. On dehydrating the oxime of perillic aldehyde the correspond- 
ing nitrile is formed which on hydrolysis yields perillic acid. Reduc- 
tion of the ester of perillic acid with sodium in absolute alcohol 
reduced one of the double bonds and gave dihydroperillic alcohol.^"* 



CHO 



i 



HC CH, 



HjC CHj 

\/ 
CH 

A 

CHg CIlj 

perillic 
aldehyde ^«' 



CH,OH 



C 

/\ 
HC CH^ 



\/ 
CH 



CO^H 



C 

/\ 
HC CH, 



HoC CH, 



CH.OH 



H— C 

/\ 

H,C ' 



CH, 



CH 



HjC CH2 

\/ 

CH 



CH, 



C 

■/v 



i 



CH, 



perillic 
alcohol 



/\ 
CH3 CHj 

perillic 
acid 



CH, 



C 



CH, 



dihydroperillic 
alcohol 



"•Lapworth & Steel, J. Olwm. Soc. 99, 1877 (1911). 

™ Semmler & Zaar, Ber. u, 52 (1911). 

201 ipije physical properties of these substances are as follows : 



BolUng-polnt (10mm.) 



PeHllic 
aldehyde 
104°-105° 



PerilUa 
alcohol 



PerUlio 
nitrile 



Density 0.9617(18°) 

[o] D —146° 



119°-121° (11mm.) 116° (11mm) 



0.9640 (20°) 
- 68.5° 



»D 



1.5074 1.4996 

Perillic acid melts at 130°-131°. 



0.9439 
— 115° 



1.4977 



Perillic 
acid 
164° 

— 20° (25% 
alcohol) 



m CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



The Phellandrenes. 

As early as 1842, Cahours noted a terpene boiling at 173°-175° 
in the essential oil of bitter fennel, which gave a crystalline nitrosite. 
The correct empirical formula of this nitrosite, CmHieNaOg, was first 
established by Pesci,^''^ who showed that "phellandrene" from the 
essential oil of water fennel, Phellandrium acquaticum, also yielded a 
nitrosite of the same empirical formula. Both phellandrenes were 
dextro-rotatory and yielded Isevo nitrosites of nearly identical physi- 
cal properties; the phellandrenes from both sources were unstable and 
even by repeated distillation were converted to limonene. Wallach 
took up the study of the phellandrenes in 1902 and a little later ^"^ 
showed that d.phellandrene from elemi oil and d.phellandrene from 
bitter fennel oil were identical in every respect and that f.phellandrene 
from Eucalyptus amygdalina oil was the corresponding Isevo form; 
that the d.phellandrene from water fennel oil is a different hydro- 
carbon, and therefore designated the two hydrocarbons as a-phellan- 
drene and p-phellandrene, respectively. 

That a-phellandrene belonged to the paramenthane series of hydro- 
carbons was early recognized by reason of the easy conversion of the 
dibromide to cymene.^"* 

The constitution ^°^ of a-phellandrene is indicated by its conversion 
to carvotanacetone (A°-p-menthene-2-one) . When a-phellandrene 
nitrite is heated with alcoholic caustic potash, nitro-a-phellandrene is 
formed which, on careful reduction by zinc and acetic acid, yields 
carvotanacetone, the constitution of which had previously been estab- 
lished, 




a-phellandrene 



a-phellandrene 
nitrite 



'"Oanz. cTUm. Hal. 16, 225 (1886). 
^<" Ann. SS6, 9 (1904). 
'"Ann. 887, 383. 
!»• Wallach, loc. oit. 



nitro-a- 
phellandrene 



carvo- 
tanacetone 



THE PARAMENTHANE SERIES 



381 



The constitution of a-phellandrene shown above is confirmed by its 
synthesis from 4-isopropyl-A''-cyclohexenone.''^" 



H,C 



O 

II 

c 



CH 



CH3 

C— OH 

/\ 

H,C CH 



H,C 



MgCHjI 
CH H,C 



CH 



CH 
CjH, 



CH 

I 
CgH^ 



CH3 

i 

HC CH 



H,C CH 

\y 

CH 



CsHj 



In carrying out the above synthesis the intermediate alcohol is not 
liberated as such but the magnesium-methyl halide addition product 
decomposes in the reaction mixture to give the hydrocarbon. Hydro- 
carbon formation is often observed under these conditions. 

a-Phellandrene nitrite is known in two forms. It is best pre- 
pared ^^^ in ligroin solution, shaking the ligroin-phellandrene mixture 
with concentrated aqueous sodium nitrite acidified by acetic acid. 
The two nitrites may be separated by crystallization from dilute 
acetone. The sparingly soluble a-nitrite, melts at 112°-113°, 
[a] -f 136° to 143°, [a]_ — 138°. The P-nitrite is more soluble 

and melts at 105° [a] + 45.8° and [a] —40.8°. On reduction 

these nitrites give a diamine, the hydrochloride of which decomposes 
on distillation yielding cymene. 

P-Phellandrene also yields two known nitrites, the so-called 
a-nitrite melting at 102° and the p-nitrite melting at 97°-98°. When 
P-phellandrene nitrite is converted to nitro-|3-phellandrene and when 
this is reduced by sodium and alcohol, dihydrocumin aldehyde is pro- 
duced,^" indicating that its structure is either 



"■'Wallach, Ann. SB9, 285. 

'" Wallach, Ann. SIS. 345 ; SS6. 13. 

»" Wallach, Ann. SiO, 9. 



382 



CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 
CH, 



H,C 



C 



CH 



H,C 



CH, 



CH, 



or 



II 



H,C CH 

\/ 
CH 



Co. 



H,C CH 

\// 
C 



sHt CgH^ 

However, P-phellandrene is optically active which eliminates II, which 
has no asymmetric carbon atom. The decomposition of nitro deriva- 
tives with the formation of aldehydes has been observed by Kono- 
walow ^^^ and others. Careful oxidation of P-phellandrene by per- 
manganate yields first a glycol which on decomposing with acids, 
yields tetrahydrocuminaldehyde, 

CH. CH,OH _ CHOH _ CHO 

3H 



CA 



^-■phellandrene 



glycol 




C,H, 



^ 




tetrahydro- 
cuminaldehyde 

Isopropylcyclohexenone is formed by air oxidation of P-phellandrene 
in the presence of moisture,^^* which may be expressed, according to 
Engler's theory of air oxidation, as follows. 




"• CTheffi. Zentr. 1889, 1, 1238. 
•"Wallacli, Ann. SiS, 29 (1905). 



THE PARAMENTHANE SERIES 383 

The following physical properties of the phellandrenes have been 
noted: 

l.a-phellandrene, boiling-point 65° (12mm.), d 0.8465, n_ 1.488. 

ly xj 

d.a-'phellandrene, boiling-point 61° (11mm.), d 0.844, n_ 

1.4732. 

Synthetic a-phellandrene, boiling-point 175°-176° d_„o 0.841, 

n 1.4760, Mj^ 45.61. 

20° 
d.^-phellandrene, boiling-point 57° (11mm.), d 0.8520, n^pr- 

1.4788, [a]j^ + 18.54 (?). 

The essential oil of Bwpleurum fruticosum yields d.p-phellandrene 
showing an optical rotation of [a] _ 65.2°, from which fact, together 

with evidence obtained by a study of the oxidation products and the 
nitrosochlorides, the discoverers ^^^ conclude that the d.p-phellandrene 
of Pesci and Wallach, which showed a much lower rotatory value, 
is a mixture of the two optical antipodes. A terpene fraction boiling 
at 169°-171°, isolated ^^^ from the volatile oil of Rubieva multifida of 
California, and consisting "largely" of p-phellandrene, showed 
[a]p-f46.4°. 

Hydrogen chloride passed into an alcoholic solution of P-phellan- 
drene gives a-terpinene dihydrochloride.^^^ 

2i» Pransesconi & Sernagiotto, Ckiza. chvm. Ital. 46 (1), 119 (1916). 

■"w Nelson, J. Am. Chen. Soo. 1,%, 1286 (1920). 

"' Fransesconi & Sernagiotto, Gazz. chim. Ital. U (2), 456 (1914). 



Chapter X. Cyclic Non-benzenoid 
Hydrocarbons. 

Ortho- and Meta-Meuthanes and Their Derivatives. 

Sylvestrene: The most important derivative of this series is syl- 
vestrene, a terpene discovered by Atterberg in Swedish oil of turpen- 
tine, from Pinus sylvestris. Its physical properties are nearly identi- 
cal with those of limonene, boiling at 175°-176°. It is one of the 
most stable of the terpenes and is not isomerized to other terpene 
hydrocarbons either by the action of heat or dilute acids. Its rela- 
tion to meta-cymene was shown by Baeyer by first reacting upon it 
by hydrogen bromide forming the dihydrobromide (melting-point 
72°), introducing a third bromine atom and treating the tribromide 
with zinc dust and alcoholic hydrochloric acid when TOeta-cymene was 
produced. Under these same condition limonene gives para-cymene. 
The inactive form of this terpene has been called carvestrene and 
bears the same relation to sylvestrene that dipentene bears to limo- 
nene. Baeyer "■ made i-sylvestrene from carvone by reducing this 
ketone by sodium and alcohol to dihydrocarveol, oxidizing this alcohol 
to dihydrocarvone and adding hydrogen bromide to the latter ketone; 
when the hydrobromide of dihydrocarvone is treated with cold alco- 
holic caustic potash, carone is formed, which substance has been 
shown to have a cyclopropane ring. The oxime of carone is reduced 
in the usual manner to the corresponding amine, and warming with 
dilute acids ruptures the three-carbon ring. When the hydrochloride 
of this amine is heated, ammonium chloride is split off and i-sylves- 
trene (carvestrene) is produced. 

'Ber. fft, 3485. 

384 



ORTHO AND METAMENTHANES 



3S5 




carvone 



dihydrocarveol dihydrocarvone 





vestrylamine i-sylvestrene 

The nature of the reaction taking place when the hydrobromide 
of dihydrocarvone is treated with alkali to form carone, and the con- 
stitution of carone, was first suggested by Wagner, whose views were 
accepted by Baeyer. In conjunction with Ipatiev, Baeyer investi- 
gated the oxidation of carone by permanganate '^ and showed the 
formation of two isomeric dibasic acids, C6H8(C02H)2, one of which 
readily forms an anhydride (when boiled with acetyl chloride) but 
the other does not form an anhydride under these conditions. Their 
research led Baeyer and Ipatiev to the conclusion that these two 
carordc acids were cis and trans modifications of the following struc- 
ture, 

C(CH3), C(CH3), 

/\ /\ 

HO,C — C C — CO,H H — C C — H 



H H 

trans-car onic acid 

'Ber. B9. 2796 (1896). 



CO,H CO,H 

cis-caronic acid 



386 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The correctness of the constitutions shown above was proven by 
W. H. Perkin, Jr., and J. F. Thorpe,^ who synthesized the caronic 
acids from bromodimethylglutaric ester, 



C2H5O2C 



C(CH3)2 
/\ 
/ \ 
CHBr H.CH.CO2C3H5 



RO2C 



C(CH3), 
-CH CH.CO^R 



Trans-caronic acid is converted to the anhydride of cis-caronic acid 
by heating with acetic anhydride at 220°. 

Inactive sylvestrene has been synthesized by Perkin ^ by means of 
the Grignard reaction. Starting with meta-hydroxybenzoic acid, 
which was reduced to cyclohexanol-3-carboxylic acid and this oxi- 
dized to the corresponding ketone, the reactions may be represented 
as follows, being parallel to the reactions employed by Perkin for the 
synthesis of limonene. 



fCH3M3l 




0,H 




•OH 

:h. 



,qH 



-CH3 

or 



I 



CO^R 




0J{ 



+ 2CH3M3: 



Mai r^^r^H^ 




r^^CH, 




It is evident that Baeyer's i-sylvestrene can be only the A^ hydro- 
carbon, but Perkin's synthetic hydrocarbon may, from the method of 
its preparation, be either A^ or A° hydrocarbon, although Perkin's 
results indicate that his synthetic sylvestrene consists at least mainly 
of the A^ product. 

'J. Cfhem. Soc. 75, 49 (1899). 

'J. Chem. Soo. 91, 482 (1907). It was believed at the time that the unsaturated 
acid was II, but later work (J. Chem. Soc. 103, 2227 [1913]), showecl that the product 
is a mixture of the two acids I and II. 



ORTHO AND METAMENTHANES 



387 



Sylvestrene cannot be isolated from Swedish oil of turpentine by 
fractional distillation on account of the presence of other terpenes of 
practically the same boiling point. It has usually been prepared by 
making the crystalline dihydrochloride from the fraction boiling at 
173°-178° and decomposing this with an alkali or an organic base. 
Wallach observed that the terpene so prepared was not pure but by 
fractional distillation of the product obtained by decomposition of the 
dihydrochloride obtained a sylvestrene of the following physical prop- 
erties. 

Blg.-pt. 175°-176°; d 0.848; n 1.4757; [a] +66.32. 
20° D D 

It is well known that the decomposition of dipentene dihydro- 
chloride or ordinary terpin, and also terpinene dihydrochloride or 
terpinene-terpin (1.4 terpin) yields mixtures of terpenes and it would 
therefore appear probable that the decomposition of sylvestrene dihy- 
drochloride would also yield a mixture of hydrocarbons. The first 
definite demonstration that sylvestrene dihydrochloride is 1.8-di- 
chloro-m.-menthane was the conversion of dl.-m.-^^-menthenol(8) and 
di.-m.-A*-menthenol (8) into this dihydrochloride," 




4-m-menTbenol(8) CK 



^^ zHCi 




zl''-m-merithenol(8l 
C(CH3i 



^ylvesTrene- 
dih_ydrochloride 

c(cH4 
Cl 



OH 

The decomposition of this dihydrochloride could possibly yield the 
following six isomeric meta-menthadienes. 



•Perkln & Tattersall, J. Chem. Soc. 91, 481 (1907) ; Perkln & Fisher, ihid., 93, 1888 
(lOOS). 



388 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



CH3 
i 
HC CH, 



(1) 



H,C 



C 
H, 



C = C 



/ 



CH, 



\ 



CH, 



CH, 

i 

H,C CH 



(2) 



CH, 



H^C C — C 
\/H \ 
C CH3 

H, 



CH, 



H,C 



C 



CH, 



(3) 



H,C 



CH, 

C CH3 

H, 



CH, 
C 
HC CH^ 



(4) 



H,C 



C=:C 



/ 



CH, 



C 
H, 



\ 



CH, 



CH, 



H,C 



C 



CH 



(5) 



H,C 



CH, 



/ 

c = c 

\/ \ 

c 

H, 



CH, 



CH, 



H,C 



C 



CH, 



(6) 



H,C 



\/ 

C 
H, 



C = C 



/ 



CH, 



\ 



CH, 



The hydrocarbons represented by (4), (5), and (6) have no asym- 
metric carbon atom and since sylvestrene is optically active its struc- 
ture cannot be (4), (5) or (6). Also, sylvestrene does not show the 
chemical behavior of a substance having a semicyclic >C = CH2 
group, which renders the structure (3) very improbable. Haworth, 
Perkin and Wallach * have shown that repeated fractionation of the 
crude sylvestrene, made by heating the dihydrochloride with 
diethylaniline, yields a sylvestrene boiling at 175° (751mm.) and 
[a]^ + 83.18° at 18°. A higher boiling fraction was also isolated, 

boiling at 182°-184° and [a] -{- 45.42°. This terpene resinifies 

rapidly on exposure to air, or in contact with sodium, and the authors 
conclude that it contains a considerable proportion of inactive syl- 
veterpinolene together with some isomeride of similar boiling-point 
but optically active. The purest sylvestrene thus obtained, boiling 
at 175°, is regarded as a mixture of the A^ and A* isomerides, (1) and 
(2) above. All efforts to obtain a pure sylvestrene of definite con- 

*J. Chem. Eoc. 103, 1230 (1913). 



ORTHO AND METAMENTHANES 



389 



stitution by the dehydration of sylveterpin, under different conditions, 
were without success owing to the marked tendency of the sylveterpin 
to form meta-cineol, 





The complexity of the problem is indicated in the foregoing discus- 
sion but, nevertheless, Haworth and Perkin^ were able to synthesize 
both optically active forms of sylvestrene and their research, cul- 
minating with the synthesis of d. and Z.sylvestrene, is one of the most 
interesting examples of refined experimental method and application 
of the theories of organic chemistry. 

The removal of hydrogen bromide from 1-bromo-l-methylcyclo- 
hexane-3-carboxylic acid yields a mixture of the A^ and A" unsaturated 
acids. 



CH, 



CO,H 




By fractional crystallization of the brucine salt an optically active 
acid [a]_^ -|- 108° was isolated, and from the mother liquors, by em- 
ploying i.menthylamine, another acid [a]_ — 49.7° was obtained. 

In order to show which of these acids was the A^ and which the A* 
acid, the latter was synthesized from l-methylcyclohexane-6-one-3- 
carboxylic acid, 



»./. Chem. Soc. MS. 2229 (1918). 



390 



H- 



CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 
CH, CH3 CK 



CHj 



H 



HO 
H 




Br. 

H 





•CQH 



and this, on resolution by brucine, also gave an acid [a]_^+108° 

and the Isevo form [a]„ — 98.6°. This dextro-rotatory acid, from 

both sources, was converted into d-A°-m-menthenol (8) , which in turn 
was changed to d.-sylvestrene dihydrochloride, [o.]y^ + 22.5°, which 

on decomposition by diethylaniline gave d-sylvestrene, [«]t-v + 67.5°. 

The laevo A« acid, [a] —98.6°, and the Isevo A^ acid, [a] j^ — 49.7° 

both gave l-sylvestrene, by similar reactions, the rotation being 
— 66.5° in one case and — 68.2° in the other. 

Sylveterpin and Sylveterpineols : When sylvestrene dihydrochlo- 
ride is shaken with dilute aqueous caustic potash the corresponding 
terpin is formed. Like ordinary terpin, sylveterpin exists in two 
modifications of the cis and trans type, the cis form melting at 
137°-138°, being less soluble, was discovered first,' and the more solu- 
ble trans form, melting at 70°-75°, was recently discovered ° in the 
mother liquors after separating the first or cis form. The cis and 
trans forms of sylveterpin are the d. constituents of the inactive or 
cis and trans carveterpins. Trans-carveterpin, melting at 126°-127°, 
was discovered by Baeyer during his researches on i-sylvestrene (or 
"carvestrene") }" 

Sylveterpineol, the chief product of the action of dilute alkali on 
sylvestrene dihydrochloride, has been shown,^^ by study of its oxida- 
tion products to be a mixture of A°-m-menthenol (8), and A^-m-men- 
thenol(8). The mixture distills at 214°. The menthenols obtained 
by synthesis, employing the Grignard reaction as described in the 
foregoing pages, are usually obtained quite pure. All of the six 
theoretically possible meia-menthenols, having the hydroxy! group 
in position (8) are known.^^ When these meta-menthenols are decom- 

'Wallacli, Ann. S57, 73 (190T). 

•Haworth, Perkin & WaUach, /. Chem. Soo. lOS, 1234 (1913). 

"Ber. S7, 3490 (1894). 

" Haworth, Perkin & WaUacb, loc. cit. 

"Perkin, J. Ohem. Soc. 97, 2129 (1910). 



ORTHO AND METAMENTHANES 



391 



posed a mixture of hydrocarbons results except in the case of A^ or 
A^-m-menthenol(8), which can decompose with loss of water only in 
one way. 



CH3 

CH 
/\ 



H,C C — C 



CH3 

I 

\ 
HCH, 



i-^ 



\// 

C 

H 

A^-m-menthenol(8) 



H,C 



H,C 



CH3 
CH 



cm 



/ 



CH, 



C — C 

" \// \ 

C CH, 

H 

^s-^W-m-menthadiene 



This hydrocarbon is of interest as showing the effect of the conjugation 
of the two double bonds upon the physical properties, as compared 
with the isomeric meto-menthadienes.^^ Its physical properties closely 
resemble the similarly constituted A^-^^^^-p-menthadiene. 

I. A^^C)— m-menthadiene" 

II. A'^^") — m-menthadiene 

III. A'^^") — p-menthadiene 

IV. A^-**") — p-menthadiene (limonene). 

/. 77. 777. IV. 

Boiling-point 182° 181°-182° 184°-185° 175°-176° 

20° 

d|^ 0.8624 0.8609 0.8580 0.8460 

nD 1.5030 1.4975 1.4924 1.4746 

M 46.6 46.3 46.02 45.23 

M. calc. for CioHie/=' 45.24. 

Dihydrosylveterpineol [m-menthanol(8)] possesses two asym- 
metric carbon atoms and accordingly exists in two slightly different 
isomeric forms, the activity of one being due to the carbon atom (1), 
and in the isomer carbon atom (3) is active. The latter substance 
is obtained by the catalytic hydrogenation of sylveterpineol and the 
former is prepared by synthesis from l-methyl-3-acetylcyclohexane.^^ 

"Luff & Perkin, J. Chem. Boc. 97, 2154 (1910). 
"Haworth, Perkin & Wallach, J. Chem. Soc. 99, 120 (19111. 

" Haworth, Perkin & Wallach, J. Chem. Soc. lOS, 1228 (1913). Wallach, Ann. S81, 
51 (1911). 



392 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 




d(3) form, 
[a]j^+10.35 

ph. methane, M.-P. 77° 
CH3 



d(l) form, 
[a]j^+1.96° 

ph. methane, M.-P. 83° 



Ortho-Menthane Derivatives: Menthenols and menthadienes of 
the ortho series have not been found in nature but we have a fairly 
complete knowledge of them due largely to the systematic researches 
of Perkin, Jr., and his assistants. The methods of synthesis employed 
by Perkin to obtain the substances of this series are quite closely 
analogous to those already described in connection with the para and 
meia-menthane derivatives. Of the six possible ori/io-menthenols, in 
which the hydroxyl group occupies postion (8) , five are known. Their 
boiling-points under 30mm. pressure are given for the known ortho- 
menthenols, 




A" 110° 



ORTHO AND METAMENTHANES 



393 



Like the m-menthenols, these of the ortho series have odors closely 
resembling a mixture of terpineol and menthol. No attempt has been 
made to resolve the synthetic inactive o-menthenols into their active 
d and I constituents. A^-o-menthenol (8) was synthesized from ortho 
toluic acid, which will serve to illustrate a typical synthesis of this 
series. Reduction by sodium and amyl alcohol gave 1-methyl-cyclo- 
hexane-2-carboxylic acid which was then brominated and then decom- 
posed to the unsaturated acid which was proven to be 1-methyl-A^- 
cyclohexene-2-carboxylic acid by oxidation with permanganate to 
3-acetobutyric acid. 




1.8(9) 



CON 



.CO,H 



A'-0-menlhenol(8) ^'^-O-merithadiene ""CH^ 

a-aceiobuT^ric acid 



As in the case of A^-m-menthenol(8), this o-menthenol can decom- 
pose with the formation of a double bond in only one direction and 
accordingly the resulting A^-^c^-o-menthadiene is quite pure. It ex- 
hibits the usual characteristics of a hydrocarbon containing conjugated 
double bonds, combines with only one molecule of a halogen or halo- 
gen acid, exhibits exaltation of the molecular refraction, has a boiling- 
point higher than its isomers which do not have their double bonds in 
conjugated position, resinifies rapidly in contact with air or on warm- 
ing with metallic sodium, etc. The same o-menthenol and o-men- 
thadiene was synthesized in quite a different manner by condensing 
diacetylpentane (by means of sulfuric acid) and treating the resulting 
unsaturated ketone with magnesium-methyl-iodide in the usual manner. 



394 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



/ 



CH, 
C = 



C — COCH3 
CH, 



CH3 
C 
H,C C — COCH3 



H,C 

\/ 

C 

diacetylpentane 



C 



H, 



CHs 
C 

HjC C — 0(0113)2 
OH 



H,0 



OH, 



\/ 


H. 

For the preparation of the A° and A°-o-menthenols and the o-men- 
thadienes resulting from their decomposition Perkin was compelled 
to make use of an ingenious method of separating the 1-methyl-A' 
and l-methyl-A^-cyclohexenecarboxylic acids. Haworth and Per- 
kin ^° had observed that of the following two acids the A* acid esteri- 
fies much more rapidly and the ester is hydrolyzed or saponified much 
more rapidly than the A^ acid. 

OHg CHj 

CH 

HC OH — CO,H HO OH — OO2H 



HO — OH, 



H2O 



OH2 

A* acid A" acid 

It was found that the methylcyclohexenecarboxylic acids showed a 
parallel behavior, the 6-acid esterifying much less rapidly than the 
5-acid. 

'•J. Chem. Boc. 9S, 57T (1908). 



ORTHO AND METAMENTHANES 
CH3 CH3 

CH i 



395 



HC 






CHCO,H. 



HC CH, 

\/ 

CH, 



HC CHCO^H. 



HjC CH2 

\/ 
C 



H, 



A'-esterifies much more rapidly than A". Perkin was able to effect a 
fractional separation of these two acids by making use of this fact, 
and then synthesized the corresponding o-menthenols in the usual 
manner. 

O-Menthane-5-One: The first o-menthanone to be described was 
prepared by reduction of l-methyl-2-isopropyl-A'-cyclohexene-5- 
one.^^ This o-menthone boils at 204° and yields an oxime melting 
at 75°. 



"KStz and Anger, Ber. U, 466 (1911). 



Chapter XL Cyclic Non-benzenoid 
Hydrocarbons. 

Bicyclic and Tricyclic Non-benzenoid Hydrocarbons. 

Camphene, bornylene and the pinenes are bicyclic hydrocarbons 
which might be considered as derivatives of cyclohexane but on 
account of their importance and the volume of their literature these 
hydrocarbons are considered in separate chapters. The three simplest 
bridged cyclohexane hydrocarbons are not known. 



/ 



H 
C 



H,C 



\ 



CH, 



CH, 



H,C 



\ 



C 

/ \ 

H,C CH 

/ 



C 

/ \ 

H,C CH, 



/ 



CH, 



CH, 



H,C 



C 
H 

norcamphane 



\ 



/ 



CH, 



H,C 



CH. 
\ 



C 
H 

norpinane 



\ 



/ 



CH 



C 
H 

norcarane 



These hypothetical hydrocarbons have the cyclic structures of cam- 
phene, pinene and carene respectively. A ketone having the structure 
of norpinane has recently been made by heating the calcimn salt of 
cyclohexane-1 . 3-dicarboxylic acid and it would probably not prove 
difficult to prepare the hydrocarbon from the ketone. Norpinane and 
particularly norcarane would probably prove to be unstable, lacking 
the gem. dimethyl group.^ 

When indene is reduced by sodium and alcohol, two atoms of 
hydrogen are added, forming hydrindene, a large number of deriva- 
tives of which are known. Willstatter and King noted that the double 

»Cf. Ingold, J. Ohem. Soc. US, 952 (1921). 

396 



CYCLIC NON-BENZENOID HYDROCARBONS 397 

bond in styrene was reduced by hydrogen and platinum very much 
more rapidly than the benzene ring and by interrupting the hydro- 
genation good yields of ethylbenzene could be obtained. Similarly, 
indene may be hydrogenated in contact with nickel at 200° to hydrin- 
dene/ boiling-point 177°. At 300°, in contact with nickel and hydro- 
gen, hydrindene is not further hydrogenated but is partly decomposed 
and partly converted to indene and hydrogen. At 250°-260°, in the 
presence of nickel oxide and hydrogen under 110 atmospheres pres- 
sure, indene and hydrindene are completely reduced to octohydroin- 
dene," a stable oil, boiling-point 165°-167° (757mm.), d 0.8334, 

nj^ 1.46287. 

Santene, C9H14. This hydrocarbon, discovered in oil of sandal- 
wood by Miiller * and in Siberian pine-needle oil by Aschan ° is note- 
worthy as being one of the few hydrocarbons, occurring in essential 
oils, having other than ten or fifteen carbon atoms. Santene is char- 
acterized by the formation of a nitrosochloride melting at 109°-110°, 
a nitrosite melting at 125° and a hydrochloride melting at 80°-81°. 
The alcohol, santenol, formed by treating with glacial acetic and sul- 
furic acids (Bertram and Walbaum's method) melts at 97°-98° and 
distills at 195°-196° (phenylurethane melting at 61°-62°). The 
acetate has an odor resembling bornyl acetate and distills at 215°- 
219°. The physical properties of santene noted by different observers 
are as follows. 

7' ir 

Boiling-point 31 °-33.°(9mm.) 140.° 

d 0.863 0.8698(15°) 

20° 
n 1.46658 1.4696 

D 

The constitution of santene has been shown by Semmler and Bar- 
telt * by means of oxidation by ozone and by permanganate in dilute 
acetone to be as represented in the following, 

2 Padoa & Fabrls, J. CJiem. Soc. Aha. 1908, I, 255. 

■ Ipatiev, J. Euss. Phys.-Chem. Soe. 1,5, 994 (1913). 

^Arch. Pharm. 238, 366 (1900). 

•Bee. iO, 4918 (1907). 

'Santene from sandal-wood oil, Semmler, Ber. 1,0, 4591 (1907). 

' Santene from Siberian pine-needle oil, Ashcan, Ber. 1,0, 4918 (1907). 

'Ber. 41, 385, 866 (1908). 



398 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 




glycol, M.-P 193° 



the constitution being clearly indicated by the formation of cyclo- 
pentane irans-dicarboxylic acid melting-point 86°, which acid was 
previously known. The formation of santene from camphenilone has 
recently been accomplished by Komppa and Hintikka ° by decompos- 
ing the corresponding alcohol, camphenilol, by sodium acid sulfate and 
also by heating camphenilyl chloride with aniline. A mixture of 
hydrocarbons is obtained but santene is the principal product. A 
little confusion is cleared up by Komppa and Hintikka by showing 
that santenol is identical with isocamphenilol and Semmler's K-nor- 
bomeol, and that santenone is identical with isocamphenilone and 
Semmler's jt-norcamphor. In the conversion of camphenilone or 
camphenilol a rearrangement occurs, such as is frequently observed 
among the terpenes and cyclohexane derivatives. 






santene 



Sabinene and Thujene may be considered as derivatives of para- 
menthane but they are both bicyclic and the bridged ring, common to 
both hydrocarbons, is a three carbon ring. Thujene (Semmler's tan- 



>Bull. aoc. cMm. U, 13 (1917). 



CYCLIC NON-BENZENOID HYDROCARBONS 



399 



acetene) has not been found in any essential oil but sabinene occurs 
in the essential oil of savin and as a subordinate constituent in a 
number of other essential oils. Sabinene purified by fractional dis- 
tillation, carried out by Schimmel and Company, showed a boiling- 
point of 163°-164° and an optical rotation of [a]y^ + 63°. Although 

the active hydrocarbon does not appear to have been obtained in a 
high degree of purity, it can be differentiated from other hydrocarbons 
of approximately this boiling-point, by its low specific gravity 0.8480 
(15°). The molecular refraction owes its exaltation over the calcu- 
lated value CipHie/^^ to the presence of the three carbon ring. 
M (observed) 44.88, calculated, 43.53. It is readily converted to 1.4- 
terpin, terpinenol (4) and terpinene by the action of dilute sulfuric 
acid. 

On oxidation by alkaline permanganate sabinene behaves very 
much like p-pinene and other substances having a semicyclic methene 
group; it yields first sabineneglycol (melting-point 54°), then sabi- 
nenic acid, the sparingly soluble nature of the sodium salt making 
its isolation easy.^" Sabinenic acid melts at 57° and on further oxida- 
tion by lead peroxide and sulfuric acid yields sabina ketone.^^ The 
three carbon ring in sabina ketone is readily broken by hydrogen 
chloride in methyl alcohol and when the product is heated with 
aniline two isopropylcyclohexenones are produced. These ketones 
have been useful as serving for the synthesis of a-terpinene and a and 
P-phellandrene. 




sabinene 




glycol 
M.-P. 54° 





sabinenic acid 
M.-P. 57° 



sabina 
ketone 



'"WaUach, 4«n. S59, 266 (1908). . ^, ,,.,.„. 

" Sabina ketone boils at 218°-219° and yields a semicarbazone melting at 141°-142'. 



400 CHEMISTRY OF THE NON-BENZENOIEf HYDROCARBONS 




+ HCl 



a 




Cl 



C,H, 



» M o( 




^^ 



Thujene has been made indirectly from thujone, a ketone occuring 
in the oils of thuja, wormwood, tansy and sage. (The ketone has 
also been called tanacetone.) The ketone can be isolated by its bisul- 
fite compound, using ammonium bisulfite and adding a little alcohol 
to increase the solubility of the ketone, and allowing to stand. The 
ketone may be liberated from the crystalline bisulfite compound by 
adding alkali and distilling with steam. There are two physically 
isomeric thujones, designated as a and |3, and when they occur to- 
gether they can be separated by fractional crystallization of the 
semicarbazones and regeneration of the ketones from the purified 
semicarbazones. The a- thujone, which is the chief ketone in thuja 
oil, boils at 200.°-201°, specific gravity 0.9125, [a] — 10° 23' and 

n 1.4510. It appears to yield two dextro-rotatory semicarbazones 

melting at 110° and 186°-188°. Heating with alcoholic caustic alkali 
or alcoholic sulfuric acid converts a-thujone partially into p-thujone. 
When p-thujone is liberated from its semicarbazone (melting-point 
170°-172° or 174°-176°) it is dextro-rotatory [a] -f- 76.16°. Its 

oxime melts at 54°-55°. The conversion of a to P-thujone by alco- 
holic alkali is reversible. Both ketones yield the same bisulfite 
compound. 

When the three-carbon ring of thujone is broken by heating with 
40 per cent sulfuric acid an isomeric ketone, isothujone (boiling-point 
231°-232°, d 0.9285) is formed, which change is represented by Wal- 
lach " and by Semmler ^^ as follows, 



"Ann. SBS, 371 (1902). 
"Ber. S3, 275, 2454 (1900). 



CYCLIC NON-BENZENOID HYDROCARBONS 



401 




thujone 




isothujone 



Hydrogen chloride breaks the three-carbon ring in a different manner, 
a-thujene giving terpinene dihydrochloride.^* Isothujone yields two 
physically isomeric thujamenthols according to whether the reduction 
is carried out by sodium and alcohol (a-thujamenthol, boiling-point 
212°-214°, d Qo 0.8990) or by hydrogen and palladium which yields 

P-thujamenthone and then by farther reduction by alcohol and sodium 
P-thujamenthone^^ yields the p-alcohol, which boils about 2° higher 
than the a- form. Thujone may be reduced to the corresponding alco- 
hol, thujyl alcohol (boiling-point 210°-212°, d^^o 0.9265), which 

alcohol is also formed by the action of nitrous acid on thujyl amine 
(the yields of alcohol by this reaction in most cases are very poor) . 
Thujylamine is obtained in the usual manner, by reduction of thu- 
jone oxime. Oxidation of thujone yields first a keto acid, melting- 
point 75°-76°, and then by further oxidation a dicarboxylic acid melt- 
ing at 141°-142°, both still retaining the three carbon ring but the 
cyclopropane ring is much more stable in the dicarboxylic acid. 




CO,H 



-> 




a-thujaketonic acid 
M.-P. 75°-76° labil 



a-dicarboxylic acid 
M.-P- 141°-142° stable 



"Wallacli, Arm. S60, 97. 



402 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The constitution of thujene has not yet been clearly shown but it 
is believed to be as follows, 



CH, 




The physical properties of the hydrocarbon, prepared' by different 
methods, indicate that "thujene" is probably a mixture of hydrocar- 
bons, one of which probably has the constitution shown above. The 
name was formerly applied to the hydrocarbon made by the dry dis- 
tillation of the hydrochloride of thujylamine or isothujylamine. 
Tschugaeff prepared thujene by heating thujyl xanthogenate, and also 
by heating and decomposing trimethylthujyl-ammonium hydroxide, 
the latter method giving a hydrocarbon of considerably higher optical 
rotation than the former. The highest rotation observed is that 
noted by Kondakow and Skworzow,^" i.e., + 109°. The following 
physical properties have been noted, 

Observer Boiling-Point Density 16" n 

D 

Semmler" 60°- 63° (14mm.) 0.8508 1.4760 

Wallach 170°-172° (760mm.) 0.8360 1.47145 

Tschugaeff" 151 °-152° (670mm.) 0.8275 1.45042 

Thujane was made by Tschugaeff and Formin^' by catalytic 
hydrogenation, in the presence of platinum, of the thujene made by 
decomposing thujylmethyl xanthogenate. Thujane is readily oxidized 
by permanganate. Sabinene also gives the same hydrocarbon by 
hydrogenation under the same conditions. The following physical 
properties were noted, boiling-point 157° (758 mm.), d^„o 0.8190, Mol. 

" Ctiem. Zentr. 1910, II, 467. 
'■• Ber. 25. 3345 (1892). 
^'Ber. SS, 3118 (1900). 
^'Compt. rend. 151. 1058 (1910). 



CYCLIC NON-BENZENOID HYDROCARBONS 



403 



Refraction— 44.54 to 44.80, calculated 43.92, the difference being 

attributed to the presence of the cyclopropane ring. Thujane pre- 
pared by Kishner^" from thujone by his hydrazine method showed 
the following physical properties, boiling-point 157.5° (741 mm.), d 

0.8164, [a]j^ +53.41, n^^ 1.4398. 

Carene: This terpene, recently found in Indian turpentine (from 
Pinus longifoUa, Roxb.) is one of the few hydrocarbons occurring in 
nature which contains a three-carbon ring. It has frequently been 
noted that this turpentine contained a terpene which yields sylvestrene 
hydrochloride and it is usually stated that sylvestrene is present in 
this oil, although Robinson ^^ stated that the terpene was probably an 
isomer of sylvestrene. Simonsen ^^ isolated the hydrocarbon, boiling- 
point 168°-169° (750 mm.) by fractional distillation, and had no diflS- 
culty in preparing d-sylvestrene hydrochloride from this fraction. The 
liquid hydrochloride mixture gave sylvestrene and dipentene on heat- 
ing with sodium acetate in acetic acid. Oxidation by permanganate 
gave a glycol melting at 69°-70° which apparently contains no pri- 
mary alcohol group indicating the absence of the methene group. 
Oxidation by permanganate under the conditions recommended by 
Baeyer and Ipatiev gave trans-caronic acid, from which facts Simon- 
sen concludes that carene has one of the two following structures, or 
is perhaps a mixture of the two. 



CH. 



CH, 



H 




H. 



H. 



CH 



H. 




^X^.CH, ^V<\ 



CH 



-\ 



CH, 



/CH, 
'^CHj 



30° 



d. Carene is slightly dextro-rotatory, [a] + 7.69°, D — - 0.8586, 

30° 
n^p- 1.469 and from the refractive index M 44.23; M calculated for 

"J. Buaa. Phut.-Chem. 8oc. iB, 1198 (1910). 
"Proc. Chem. Boo. 187, 247 (1911). 
''J. Chem. Soc. 117, 570 (1920). 



404 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

CjoHie/^^ = 43.5 and adding the increment usually observed in cases 
where a cyclopropane ring is present M calc. becomes 43.5 + 0.69 
= 44.19. 

Naphthalene is readily hydrogenated in the presence of finely 
divided platinum. When dihydronaphthalene is employed as the 
raw material, two atoms of hydrogen are very rapidly taken up and 
if the hydrogenation is then interrupted a good yield of tetrahydro- 
naphthalene can be obtained but when starting with naphthalene and 
stopping the operation after four atoms of hydrogen had been taken 
up, the product was found to be a mixture of unchanged naphthalene 
and decahydronaphthalene.^' 

Tetrahydronaphthalene and the completely hydrogenated decahy- 
dronaphthalene were widely used in Europe, during the war period, as 
solvents, particularly as paint and varnish thinners.^* A mixture of 
the hydrocarbons is manufactured under various trade names. Their 
solvent values are not accurately known but they are miscible with 
petroleum oils and are good solvents for coumarone resin, many 
natural resins, waxes, fats and oils. Their manufacture appears to 
be carried out in accordance with the well-known conditions of hydro- 
genation, employing temperatures within the range 120°-150°, and 
pressures within the range 3 to 100 atmospheres.^^ A preliminary 
purification from sulfur compounds by heating with metallic sodium, 
or with sodium amide is advised.^^ Tetrahydronaphthalene distills 
at 205°-207°, d 0.975, flash-point 78°. Decahydronaphthalene dis- 
tills at 189°-191°, d 0.8827, flash-point 57.3°." Auwers =' notes 

the molecular refraction (D line) of tetrahydronaphthalene as 42.91 
and that of decahydronaphthalene as 43.85. 

The action of bromine on tetrahydronaphthalene is of interest as 
indicating the relative ease of bromine substitution in the two types 
of rings. No reaction takes place in the dark except in the presence 
of a catalyst such as iron or iodine when substitution in the benzene 
ring takes place. At higher temperatures, or in the light, the reduced 
ring is rapidly attacked but the only product isolated was a (3-dibromo- 
tetrahydronaphthalene ^^ (melting-point 70°). 

2=WiUstatter & King, Ber. iS, 527 (1913). 

" Frydlender, Rev. prod. oMm. 23, 437 (1920). 

=»Brlt. Pat. 147,474 (1920). 

=«Brit. Pat. 147,488 (1920); 147,580 (1920). 

'"Vollman, Fiirher Ztg. 2Jt, 1689 (1919). 

"Ber. i6, 2988 (1913). 

"V. Braun & Kirschbaum, Ber. Si, 597 (1921). 



CYCLIC NON-BENZENOID HYDROCARBONS 



405 



The alcohols a and P-naphthanol were prepared by Ipatiev by his 
high pressure method.'"' P-Naphthanol Ci„Hi,.OH distills at 242°- 
244° and melts at 99°-100°; a-naphthanol, CioHi^OH, distills at 
245°-250° and melts at 57°-59°, but Mascarelli" states that this 
alcohol can be separated into two stereo-isomers melting at 75° and 
103°. Both alcohols resemble cyclohexanol and the aliphatic sec- 
ondary alcohols in their chemical behavior. Naphthane-2 . 2-diol has 
been obtained in cis and transiorms; by the action of dilute caustic 
potash on 2 . 2-dibromonaphthane the cis form melting at 160° is 
obtained, while silver acetate on the dibromide yields the trans diol, 
melting at 141°.=2 

The ketone p-naphthanone has been very little studied but evi- 
dently undergoes the reactions of ether alicyclic ketones. Darzens 
and Leroux'^ condensed p-naphthanone with chloroacetic ester in the 
presence of sodium ethylate to the glycidic ester, the free acid from 
which loses carbon dioxide on distillation giving P-naphthanoic alde- 
hyde (boiling-point 95°-96° at 3 mm.). 



H,C 



C C 

/ \H/ \ 

C C: 







H,C 



C 



CH, 



RC — CH.COjR- 

\/ 





H^C 



C C 

/ \H/ \ H 
C C< 

CHO 



\ /H\ / 

c c 



H,C 



C 



CH, 



\ /H\ / 

c c 



H, 



H, 



H, 



H, 



a, a-Dicyclohexylethane, < > — CHgCHa — < > This hydro- 
carbon was made by Sabatier and Murat ** by the hydrogenation of 
diphenylethane in the presence of catalytic nickel and hydrogen at 
220°. Its physical properties are as follows: Boiling-point 256°-257°, 

The Nomenclature of spiro and other bridged ring hydrocarbons 
is in a very unsatisfactory state and none of the systems thus far 
proposed are very satisfactory except for certain types or classes of 
hydrocarbons. Probably the most flexible and least confusing is that 

"Ber. 1,0, 1288 (1907). 

" Ohem. Ais. 1912, 83. 

'^Leroux, Oompt. rend. US, 1614 (1909). 

''Uompt. rend, m, 1812 (1912). 

'^Compt. rend, m, 1771 (1912). 



406 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

recently proposed by Beesley and Thorpe. The scheme advocated by 
Baeyer °° rests upon the fact that all dicyclic systems contain three 
bridged rings which makes it possible to distinguish them by prefixed 
numerals such as (0.1.2), (1.2.3), (0.1.4) and so on, depending 
upon whether the "bridge" is formed by the linking of two tertiary 
carbon atoms (0), or whether it is itself formed by 1,2 or more carbon 
atoms. When Baeyer's system is extended to tricyclic substances it 
becomes exceedingly cumbersome and complex. The plans suggested 
by Borsche ^^ and by Bredt and Savelsberg " are open to the objection 
that terms such as methylene are used to denote ring formation and 
not unsaturation, and that the names of the compounds do not neces- 
sarily indicate to which of the cyclic systems they belong. Thus 
pinene by these systems would be named as follows, 

Borsche. l-Methyl-l-r-^'*)-dimethylmethylene-A*(*)-cyclohexene. 

Bredt and Savelsberg: rw-meso-methylene-4.4.2|3-trimethylcyclo- 
A^-^P-hexene. 

Beesley and Thorpe (see below) : dimethylmethane-II^'-4-methyI- 
A*-cyclohexene. 

The hydrocarbon of the following structure, 
CHj CH CHj 

CH, — C — CH, 

CH, C CH 



ch: 



2 



would be named, according to Bredt and Savelsberg, p-mesometh- 
ylene-1 . l-dimethylcyclohexane-amphi-2^ . 3^-methylene. By Beesley 
and Thorpe's system, the name would be methane-IP- "-cyclohexane- 
^■*II-dimethylmethane. Beesley and Thorpe's system appears to the 
writer to be much more easily grasped and easier to apply than the 
others, — and much more definite. It may be briefly outlined as 
follows: 

A compound containing associated rings may be of two kinds. 

A. It may be formed from a simple ring compound having a side 
chain of carbon atoms from which another ring is produced by a link- 
ing between another carbon atom of the ring and another of the side 
chain, thus: 

"Ber. SS, 3771 (1900). 
"Ann. S77, 70 (1910). 
"J. prakt. Chem. (2) 97, 1 (1918). 



CYCLIC NON-BENZENOID HYDROCARBONS 



407 



\ 



/^ 



CH-CHCH^CH, (1) 



\ 



-CHi 



CH-CH,CH,CH/ 



\ 
d 



CH-CHjCHCHj 



(2) 



\ 



.ci 



CH-CH^CH^CH; 



(3) 



In these cases the side chain and the ring would be given their usual 
names, the number of linkings joining the two would be indicated by 
a Roman numeral, and the carbon atoms of the two series participat- 
ing in the ring complex would be indicated by means of index figures 
on which the particular residue is placed. Thus, the above hydrocar- 
bons (1), (2) and (3) would be named as follows, 

(1) is Ethylmethane-IP^ — cyclopentane. 

(2) is 2-Methylethane— ^-^IP-^ — cyclopentane. 

(3) is Propane — i-snis — cyclopentane. 

The following is an example of the nomenclature of derivatives accord- 
ing to this system. 

CHg — CH — - CHj 

>CH — CH.Br 



CH, 



-C- 

I 
Br 



l-bromo-2-methylethane- 



CH.CH„ —12 II 1.2. 



-2-bromo-4-methyl- 
cyclopentane. 



CH 

/ \ 

CH^ CH 

\ / 

CH 



I 



IH 2-methylethane— 11-2— III1-2-* — 

CH . CHg • — cyclobutane. 

B. The associated ring may be considered as formed by linking 
pairs of carbon atoms in a ring to which another ring is already 
attached, as for example, the following, 



408 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 
HjC CH2 HoC CH CH 



\ CH, 

CH — CH<| 
/ CH 



2 



CH — CH 
/ \ 



HjC CHj HjC CH2 CH2 

cyclopropane-^-^ II ^•^- 
-cyclopentane 

The only rules which seem to be necessary are: (1) That one of 
the linked carbon atoms in the ring should be called 1, and that the 
corresponding carbon atom in the chain should also be called 1. The 
numbering would then proceed in the ring clockwise, and in the side 
chain in the usual manner. (2) That the name of the simplest por- 
tion of the chain entering into ring formation should be used first, 
and any attached groups should be named as derivatives of the 
simplest chain, for example, 

CH, — CH 1 



/ \ I 

CH2 CH — CH.CH — CHa 



CH, — CH- 



'■2 

2-methyl — ^-^ III ^-^-^ — cyclohexane 

For further details and possible extensions of the system to hetero- 
cyclic compounds, the original paper of Beesley and Thorpe should be 
consulted."* 

S.S-Dimethyl-[0.1 .S]-Dicyclohexane: This hydrocarbon was 
synthesized by Zelinski'^ by reducing 1 . 1-dimethylcyclohexane 3.5- 
dione to the corresponding diol, converting the diol to the correspond- 
ing dibromide by phosphorus tribromide and finally treating the dibro- 
mide with zinc dust in aqueous alcoholic solution. The chemical and 
physical properties of the resulting hydrocarbon, boiling-point 115° 

20° 20° 
(corr), d 0.7962, n 1.4331, particularly when compared with 

the isomeric 1 . l-dimethyl-A°-cyclohexene led Zelinsky to propose 
the bicyclic structure shown below. The three carbon ring is broken 
in two ways under different conditions. (1) By heating with hydri- 
odic acid to give a hydrocarbon boiling at 115°-116° and indifferent 
to bromine and permanganate, probably 1.1. 3-trimethylcyclopentane, 
and (2) by catalytic hydrogenation in the presence of platinum black, 

"J. Ohem. Soc. 117, 591 (1920). 
"Ber. ie. 1466 (1913). 



CYCLIC NON-BBNZBNOID HYDROCARBONS 



409 



yielding a hydrocarbon distilling at 109.5°-110.5°, which Zelinski 
claims is l-methyl-2-isobutylcycIopropane. 

CH — CH, CH^ — CH, 



H,C 



/ 

\ 



CH — CH, 



\ CH3 

C< 
/ CH3 



CH, 


\ CH 

c< 


\ 


/ CH 



\ 



CH 



\ CH 

\ H,C<T 



■CH, 
•CH3 
CHa — CH< 



CH3 
^CH, 



The stability of this hydrocarbon to heat was not investigated but 
it is acted upon rather energetically by concentrated sulfuric acid. 
A similar dicyclohexane derivative was discovered by Kishner,*" 
in quite a different manner. When camphophorone is treated with 
hydrazine a pyrazolone base is first formed, which on heating with 
caustic potash yields the hydrocarbon 2.6.6.-trimethyl-[0.1 .3.]- 
dicyclohexane. It has a petroleum-like odor, boils at 140° (752 mm.), 

20° 
d -— - 0.8223 ; does not decolorize permanganate, dissolves in fummg 

nitric acid and reacts with hydrogen bromide to give a bromomethyl- 
isopropylcyclopentane. 



CHj — CH2 CH3 

>CH— C< + KOH 



CH,— CH — C 



+ HBr 



\n- 



CH, 



NH 



CH, 



CH, 



CH, 
-CH 



-CH— CH 

/I CH3 
-CH — C< 

CH, 



■ CH2 — CHj 
/ 

/ 

CH3 — CH — C 

\ 
H \ 

CBr.(CH3)2 

Caryophellene: The hydrocarbon oil described in the older litera- 
ture under this name has been shown by Deussen and his students to 
be a mixture of at least two and probably three hydrocarbons. The 

"J. Ruse. Phya.-Chem. Soo. U. 849 (1912). 



41d CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

hydrocarbon mixture, isolated from copaiba balsam, clove oil and 
other essential oils, which distills at about 258°-261°, d 0.905 to 0.910 
and which yields a crystalline dihydrochloride (by passing dry HCl 
into a dry ethereal solution) melting at 69°-70°, has been called 
caryophellene. The easiest crystalline derivative to prepare is caryo- 
phellene alcohol, CigHjeO, readily prepared from the hydrocarbon by 
Bertram and Walbaum's method. The alcohol melts at 94°-96° and 
yields a phenylurethane, melting at 136°-137°. 

The work of Deussen and others on caryophellene clearly shows 
the diflSculties of working with mixtures of hydrocarbons and the 
almost impossible task of determining the constitution of such sub- 
stances when present together and when they cannot easily be sepa- 
rated. It is worth while to examine Deussen's work as indicating 
to a limited extent the diflBculties with which one would be confronted 
in attempting to ascertain the structure of the hydrocarbons occurring 
in the higher boiling distillates of petroleums.*^ 

Wallach obtained a crystalline nitrosochloride melting at 161°- 
163° from the hydrocarbon fraction boiling at 250°-270°, derived 
from oil of cloves. Kremers and Schreiner prepared the nitrosochlo- 
ride and after reacting with benzylamine, were able to separate the 
nitrolbenzylamine by fractional crystallization into fractions melting 
at 167° (named a-caryophellenenitrolbenzylamine) and at 128° 
(named p-caryophellenenitrolbenzylamine) . Deussen *^ found that 
by heating the crude nitrosochloride in alcohol, cooling and separating 
the crystals, the melting-point was raised to 177°-179°. The behavior 
of the nitrosochlorides led Deussen to suspect the presence of one or 
more other hydrocarbons. Repeated fractional distillation *^ resolved 
the crude caryophellene into three fractions, fractions I and III hav- 
ing different optical rotation and slightly different boiling-points, but 
otherwise very much alike, 

/ III 

Boiling-point 132.°-134.°(16mm.) 123.°-124.° (14.5mm.) 

Uljj —4.67° —25.03° 

dgo 0.90346 0.8990 

n j3 0.49973 1.49617 

MR 66.45 66.31 

MR <for /=") 66.15 

*' It Is the writer's belief that the only practical way of throwing any light on 
the character of such petroleu.-u hydrocarbons is to synthesize hydrocarbons of different 
types and compare the properties of such synthetic hydrocarbons with close cut petro- 
leum fractions. 

"Ann. S56, 5 (1907). 

"Ann. S59, 246 (1908). 



CYCLIC NON-BENZENOID HYDROCARBONS 411 

Fraction I. was believed to be inactive, so-called a-caryophellene con- 
taminated with a small proportion of the Isevo-p-caryophellene. The 
latter hydrocarbon yields a blue nitrosite from which Deussen con- 
cludes ** (from Baeyer's work on terpinolene) that p-caryophellene 
contains a double bond of the type shown in the following structure, 
which he proposed. 



CH3 



H. 



CH C 

/\H/\ 

HoC C CH„ 



HjC C CH2 

\/H\/ 

C C 



C CH3 

/\ 

CHg CH3 

When an excess of N2O3 (from the reaction of arsenious acid and 
nitric acid) is passed into an ethereal solution of caryophellene a blue 
color first appears, followed by the formation of a voluminous yellow- 
ish white precipitate and the discharge of the blue color,*^ this be- 
havior resembling the formation of caoutchouc nitrosite.*" The volu- 
minous precipitate from caryophellene crystallizes from ethyl acetate 
in silky needles melting with decomposition at 159°-160°, the separa- 
tion of this substance being regarded by Deussen as a delicate test for 
P-caryophellene. The formation of this substance is attended by the 
removal by oxidation of the isopropyl group. 

\/ 

C — NO \/ 

1 CH 

0_ONO > ...1.... ONO \/ 

/\ C / > HC — ONO 

CH3 CH3 / \ 

CH3 CH^NO + C3 residue 

Deussen advanced this explanation of the change by reason of the 
fact that the product is soluble in alkali, a property only of primary 

"Am». ses, 55 (1909). 
"Deussen, Ann. S8S, 138 (1912). 
"Harries, Ann. S83, 198 (1911). 



412 CHEMISTRY OF THS NON-BENZENOlD HYDttOCARBOliS 

and secondary nitro derivatives. Deussen " represents the deriva- 
tives of a and P-caryophellene diagranunatically as follows, 

a-caryophellene 

/ (Humulene) \ \ 

i/ \ \ 

nitrosochloride nitrosate nitrosite 

M.-P. 177° M.-P. 161° M.-P. 116° 

\ I 

+ Na ethylate \ | 

nitrolbenzylamine 
i M.-P. 126°-128° 

nitrosocaryophellene 
M.-P. 128° 

6-caryophellene 

, , / / \ \ 

glycol / / \ \ 

M.-P. 120.5° / nitrosite dihydrochloride 

/ M.-P. 115° M.-P.69°-70° 



\ \ 

\ \ 

\ \ 



nitrosochloride / 
M.-P. 159° / 

/ \ / 

[/ \i/ CiaHjgNgOe isocaryophellene 
nitrolbenzylamine\ M.-P. 159.5° \ 

M.-P. 172°-173° \ \ 

a-form < nitrosochloride 

M.-P. 122° M.-P. 120° 

\ / 

\ i/ 

P-form 

M.-P. 146° 

Although Semmler and Mayer ** have proposed structural formulae for 
what he terms (using a curious nomenclature of his own) Terp-caryo- 
phellene and Lim-caryophellene, these structures can hardly be con- 
sidered as proven and will not be given space in this brief review. 
The above outline will indicate the variety of the isomeric derivatives 
and the diflBculty of clearing up the constitution of such mixtures of 
oils. Humulene is the name given by Chapman to a sesquiterpene 
fraction isolated from oil of hops, but Deussen considers it to be 
identical with a-caryophellene. 

Cadinene is the name given to a hydrocarbon or rather a mixture of 

"Ann. S69, 41 (1910). 

"Ber. iS, 3451 (1910) ; U, 3651 (1911). 



CYCLIC NON-BENZENOID HYDROCARBONS 413 

hydrocarbons occurring in camphor oil, cedar wood and other essen- 
tial oils; it is characterized by the formation of a dihydrochloride 
melting at 117°-118° and this dihydrochloride may be prepared from 
the crude hydrocarbon mixture distilling at 260°-280°. Pure cadi- 
nene has never been obtained from natural oils but the sesquiterpene 
regenerated from the dihydrochloride (which is perhaps not identical 
with the natural hydrocarbon) is usually regarded as nearly pure 
"cadinene." The hydrocarbon may be prepared by decomposing the 
dihydrocMloride by the usual methods, heating with alcoholic caustic 
alkali, with aniline, or with sodium acetate in acetic acid. The 
physical properties of regenerated cadinene are as follows, 

I» II» III" 

Boiling-point 274.°-275.° 271.°-273.° 271.°-272.° 

dggo 0.918 0.9215(15°) 0.9183 

[o]j5 —98.56° —105.° 30' —111.° 

n-Q 1.50647 1.5073 

Dextro-rotatory cadinene has been observed in the essential oil of the 
Atlas cedar. 

Cadinene resinifies very rapidly and is very easily polymerized, 
an indication that the two double bonds are in conjugated positions. 
The dihydrobromide, melting-point 124°-125°, and the dihydroiodide, 
melting at 105°-106°, are best made in glacial acetic acid solution. 
By catalytic hydrogenation, in the presence of platinum, tetrahydro- 
cadinene is produced, boiling at 125°-128° (10mm.), d 0.8838, 

n^ 1.48045. 

The constitution of cadinene is not known. 

By the distillation of galbanum resin Semmler and Jonas ^^ ob- 
tained a sesquiterpene alcohol, cadinol, which on decomposition by 
potassiuna acid sulfate, formic acid or phthalic anhydride yields 
cadinene. 

Selinene: A sesquiterpene distilling at 262°-269° was discovered 
in oil of celery seed by Ciamician and Silber ^' and the hydrocarbon 
was later recognized as a new hydrocarbon by Schimmel & Co.,°* 
who characterized it by the formation of a dihydrochloride melting 

"Wallach, Ann. 252, 150 (1889) ; sri, 207 (1892). 

'» Schimmel & Co. ; Gildemeister, "Die Aetherischen Oele," Ed. II, Vol. I, 347. 
"J. Ruas. Phps.-Chem. «or. iO, 698 (1908). 

" Ber. kl, 2068 (1914). Cadinol distills at 155°-165° (iSmm.), d„„ 0.9720 
[a] p + 22°. 20 

"Ber. it, 496 (1897). 

" Schimmel & Co. Semi-Ann. Eep. ISIO (1), 32. 



414 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



at 72°-74°. Semmler and Risse" prepared the dihydrochloride (by 
HCl into the ethereal solution) and regenerated what they regard as 
selinene, identical with the original hydrocarbon but purer, by decom- 
posing the dihydrochloride by alcoholic caustic potash. The hydro- 
carbon thus obtained distills at 128°-132° (11 mm.), d^^^ 0.919, n^^ 

1.5092, [a]_ + 61° 36'. Reduction by sodium and alcohol yields 

tetrahydroselinene having the following physical properties, boiling- 
point 125°-126° (10 mm.), d^^^ 0.888, [a]j-j+ 1° 12', n^^ 148375. 

By shaking the dihydrochloride with milk of lime for 36 hours 
at 95° an alcohol, selinol, CigHjeO, is formed, which may be reduced 
by hydrogen (Willstatter's method) to dihydroselinol, CigHjaO, melt- 
ing-point 86°-87°. 

On account of differences observed in the products obtained by 
treating natural and regenerated selinene with ozone and hydrolyzing 
the ozonides, Semmler regards natural selinene as a mixture of two 
hydrocarbons, both of which are believed to yield the same dihydro- 
chloride. Semmler regards these two hydrocarbons as related to each 
other in the same way as a and P-pinene, the hydrocarbon predomi- 
nating in natural selinene having a >C = CHj group, the double 
bond in the regenerated selinene being in the ring. Many will regard 
the constitutions proposed by Semmler as guesses, perhaps to be 
proven correct by further work but not clearly shown up to the 
present time. The two selinenes are bicyclic, contain two double 
bonds, and are believed by Senamler to be represented by the two 
following structures, 

CH, CH, 



CH, — C 



H. II 
C C 

H / \H/ \ 



H, 



C 



CH, 



\ /H\ / 

C CH 

H, 



c- i 

H / \H/ \ 
CH3 — C C CH 



HjC C CH2 



A 



C CH 



CH3 CH2 

natural selinene 

"Ber. iS, 3301 (1912) ; ^6, 599 (1913). 



i 



CH3 CH2 

regenerated selinene 



CYCLIC NON-BENZENOID HYDROCARBONS 415 

Eudesmene: A sesquiterpene alcohol discovered by Smith ^' in 
numerous eucalyptus oils, and named eudesmol, yields the sesquiter- 
pene eudesmene, C15H24, when decomposed by heating with 90 per cent 
formic acid. The alcohol is a bicyclic unsaturated alcohol, melting- 
point^' 84° and distilling at 156° (10 mm.). It adds two atoms of 
hydrogen when reduced by Willstatter's method (hydrogen and plati- 
num black in acetic acid solution) and the resulting dihydro-eudesmol 
melts at 82° and distills at 155°-160° (12.5mm.). When eudesmene 
or the alcohol is treated with hydrogen chloride in acetic acid a dihy- 
drochloride, melting at 79'°-80°, is formed. The dihydrobromide 
melts at 104°-105°. Eudesmene also combines with four atoms of 
hydrogen when reduced by the Willstatter method.^^ The physical 
properties of the two hydrocarbons are as follows, 

Eudesmene Telrahydro-eudesmene 

Boiling-point 122.°-124.° (7mm.) 122.°-122.5° (7.5mm.) 

dgQO 0.91964 0.8893 

[o]j^ + 54.6° + 10.2° 

n^ 1.50874 0.48278 

Santalenes : The sesquiterpene fraction of East Indian sandal- 
wood oil apparently contains two hydrocarbons, which Guerbet =" has 
called a and p-santalene. Their physical properties do not differ 
widely, a-santalene distilling about 10° lower than |3-santalene. Both 
hydrocarbons give liquid hydrochlorides but a-santalene forms a 
nitrosochloride melting at 122° (nitrolpiperidide melting at 108°- 
109°) and p-santalene forms a mixture of two nitrosochlorides which 
can be separated by fractional crystallization to one melting at 106° 
and another melting at 152°. Probably neither hydrocarbon has ever 
been isolated in a very pure state. Semmler*" gives the following 
physical properties of the two hydrocarbons. 

Boiling-Point d^QO '•C^D "/) 

. , ( 253°-254° (Corr.) 0.8984 -15° 1 .491 

a-santalene -j n8°-120°(9mm.) 

fl =„„tol<.r,<. i 263°-264°(Corr.) 

^-santalene ^ i25M27°(9mm.) 0.892 -35° 1.4932 

" J. <6 Proc. Boy. Soc. N. S. W. SS, 86 (1899). 

»' Semmler & Tobias, Ber. J,6, 2026 (1913). The melting-point previously recorded 
by Semmlcr, Ber. iS, 1390 (1912), was 78°. 
"SemmJer & Kisse, Ber. 46, 2303 (1913). 
"Bull. Soc. cMm. (3) S3, 217 (1900). 
"Ber. ifi, 3321 (1907). 



416 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Semmler'^ regards a-santalene as bicyclic and p-santalene as 
tricyclic. 

Associated with the santalenes in sandal-wood oil are two alcohols, 
a and p-santalol, but their relation to the hydrocarbons has not been 
shown and Guerbet prefers to distinguish the hydrocarbons formed by 
the decomposition of the alcohols by the names a-iso and P-isosanta- 
lene. The santalols are both primary alcohols, yield an aldehyde, 
by oxidizing with chromic acid, whose semicarbazone melts at 230°. 
Oxidation with permanganate yields chiefly tricycloeksantalic acid, 
C11H15O2, melting at 71°-72°. According to Guerbet a-santalol dis- 
tills at 300°-301° and p-santalol at 309°-310°. The former is nearly 
inactive, [a]]-) — -1.2° and P-santalol has the rotation [a]j) — 56°. 

When a-santalol is reduced by hydrogen in the presence of platinum 
the hydroxyl group is replaced by hydrogen; the product is tetra- 
hydrosantalene,^^ a bicyclic hydrocarbon, CibHss, distilling at 115°- 
116° (9 mm.). p-Santalol behaves similarly, giving mainly tetrahy- 
drosantalene. 

By heating I. a-phellandrene and isoprene together in a sealed tube, 
Semmler obtained a hydrocarbon C15H24 boiling-point 129°-132° (at 
15 mm.), d2oo 0.8976, n-Q 1.4949, which he regarded as p-santalene. 

Limonene and isoprene under the same conditions do not react. In 
a series of such experiments Semmler showed that generally conden- 
sation of isoprene with the terpenes can be effected at about 275° 
but at 330° and higher, the sesquiterpenes are decomposed.*^ 

Cedrene: This sesquiterpene, occurring in cedar- wood oil associ- 
ated with the closely related alcohol, cedrenol, is of imknown consti- 
tution although considerable effort has been spent in research on this 
hydrocarbon. It forms a dihydrocedrene when catalytically reduced 
in the presence of platinum. Cedrene distills at 262°-263°, or 124° to 
126° at 12 mm., d^^o 0.9354, [a]^ — 55°, n^^ 1.50233. Oxidation by 

permanganate (in acetone solution) yields a glycol melting at 160°, 
also a diketone or ketoaldehyde of the empirical formula C15H21O2 
and a keto acid of unknown constitution, C15H24O3 (oxime melting at 
60°). By oxidation of cedrene by chromic acid in acetic acid solution 
a ketone, cedrone, is produced, this ketone having a strong odor of 
cedar wood, distills at 147°-150.5°, d ^3.5° l-OHO." 

"Ber. 1120 (1907). 

•= Semmler & Hisse, Ber. i6, 2303 (1913). 

"Ber. 1,7, 2252 (1914). 

" Semmler & Hoffman, Ber. ie, 768 (1913). 



CYCLIC NON-BENZENOW HYDROCARBONS 417 

Cedar-wood oil appears to contain two sesquiterpene alcohols 
related to cedrene."^ 

Dihydrocedrene, obtained from natural cedrene by catalytic hydro- 
genation, distills at 122°-123° (10 mm.), d 0.9204, n^^ 1.4929. No 

crystalline hydrochlorides or hydrobromides of cedrene are known. 

Tricyclic non-benzenoid hydrocarbons have been made by the 
catalytic hydrogenation of tricyclic benzenoid hydrocarbons such as 
anthracene and phenanthrene. By the hydrogenation of phenan- 
threne at the remarkably high temperatures of 360°, under high pres- 
sure, Ipatiev °^ obtained the completely reduced hydrocarbon Ci^Hj^, 
which he calls perhydroanthracene. It is an oil distilling at 270°- 
276° and does not crystallize at 15°. It is inert to permanganate solu- 
tion and bromine in the cold, and also practically unacted upon by 
sulfuric-nitric acid nitrating mixture. 

Anthracene was reduced by Godchof" over nickel at 260° to 
tetrahydroanthracene, the constitution of which is unknown. It crys- 
tallizes from alcohol in plates melting at 89° and distilling at 309°. 
At a little higher temperature, 200°-205° octohydroanthracene, melt- 
ing-point 71° and distilling at 292°-295°, is formed, and at 260°-270° 
and under about 125 atmospheres pressure Ipatiev ^^ succeeded in 
reducing it to decahydroanthracene, melting-point 73°-74°, and finally 
to the completely reduced hydrocarbon, perhydroanthracene, an oily 
liquid. 

Copcene: This name has been given by Semmler and Stenzel °' to 
a sesquiterpene occurring, together with caryophellene, in African 
copaiba balsam. The hydrocarbon was separated by fractional dis- 
tillation, its constants as thus isolated, being as follows, boiling-point 
119°-120° (10mm.), d^^,, 0.9077, [a]^ —13.35°, n^^ 1.48943. It 

gives a hydrochloride identical with that formed by cadinene. The 
new hydrocarbon is apparently tricyclic, combining with two atoms 
of hydrogen, by catalytic hydrogenation to give dihydrocopsene, 
Ci^H^s (boiling-point 118°-121° at 12 mm., n^^ 1.47987, d 0.8926). 

Semmler has proposed a constitution for copsene. • 

Abietic Acid: Ordinary commercial rosin consists chiefly of abietic 
acid. Its constitution is not definitely known but it has been shown 

"•Semmler & Mayer, Ber. 1,5, 1384 (1912). 

"Ber. J,l, 999 (1908). 

'^ Awn. chim. phys. (8) J2, 468 (1907). 

''Ber. J,l, 996 (1908). 

"Ber. p, 255 (1914). 



418 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

to have the three ring carbon structure of phenanthrene. Heating 
with sulfur forms H2S, carbon dioxide and retene, which hydrocarbon 
is believed to be a methyl isopropyl derivative of phenanthrene. The 
fossil substance fichtelite, CigHgj, is regarded as completely reduced 
retene. Schulze '" showed that rosin oil, obtained by the destructive 
distillation of rosin, contains hydrogenated retene derivatives and by 
oxidation 1.2.4-benzene tricarboxylic acid was obtained. The for- 
mation of this acid from abietic acid would show that the methyl and 
isopropyl groups are not attached to the same ring. Although com- 
bustion analyses of abietic acid, reported by different observers, agree 
almost equally well with the empirical formulse CigH^gOj and 
CjoHjoOj, it may be pointed out that the formula CigHjgOa agrees 
best with the known evidence that abietic acid has the carbon skeleton 
of phenanthrene together with a carboxyl group, a methyl and an 
isopropyl group, or 19 carbon atoms in all. Easterfield and Bagley " 
found that abietic acid was esterified with diflBculty and therefore sug- 
gested that the methyl and isopropyl groups were in ortho positions 
with respect to the carboxyl group, thus assigning these two groups 
positions in one of the rings. Bucher''^ has reviewed the literature 
and, in view of the character of the oxidation products, states that 
one of the alkyl groups must be in position (8) and the other in posi- 
tion (2) or (3) . Bucher also notes that an alkyl group in position (2) 
and the carboxyl group in position (1) would satisfy the condition 
which Easterfield and Bagley believed to be required by the slow rate 
of esterification. It need hardly be pointed out that much of this 
rests upon very slender evidence. As regards the difficulty of esteri- 
fying acids by saturating an alcoholic solution with hydrochloric acid 
gas, it may be pointed out that instances are known in which esteri- 
fication with the aid of hydrogen chloride proceeds with difficulty, 
but with relative ease when the alcohol and acid are heated together. 
The formula CigHjsOj and the tricyclic structure of reduced retene 
leaves two double bonds to be accounted for. 

Griin,^^ who adheres to the CjoHgoO^ formula, has recently pro- 
posed a constitution for abietic acid which has only one double bond '* 

■"Ann. SB9, 132 (1908). 

"J. Chem. Soc. 85, 1238 (1904). 

"J. Am. Chem. Soc. SB, 374 (1910). 

".A. Chem. Soc. Aba. 1921 (1), 344. 

" Unpublished work of the writer has shown that when abietic acid, recrystalllzed 
from alcohol containing a little hydrochloric acid, is hydrogenated in dilute alcohol by 
Skita's method, the quantity of hydrogen absorbed is that required by two double 
bonds (within a very small experimental error). This, however, may nevertheless be 
in accord with Grfln's formula and it may also be pointed out that Grfln's formula 
may also account for the peculiar behavior noted in recrystallizing abietic acid. The 



CYCLIC NON-BEN ZENOID HYDROCARBONS 



419 



and has a bridged ring as in pinene, with which hydrocarbon abietic 
acid is associated in the natural oleo-resin. The formulae which have 
been suggested are as follows, 

Hqc 

CO,H 




C3H; 




-CH, 




CQ,H 

Easterfield & Bagley Bucher 

• (Double bonds not placed) 



Griin 



Rosin oil has been manufactured on a large scale and the heavier, 
neutral fractions used as a lubricant. As noted above such oils con- 
tain hydrogenated phenanthrene or retene derivatives. The crude oil 
contains about 30 per cent by volume of organic acids, has a marked 
greenish-blue fluorescence, and distills over a wide range of tem- 
perature. Its density varies from about 0.945 to 1.010. The lighter 
fractions, consisting of hydrocarbons of unknown character, are some- 
times distilled and collected separately, being known industrially as 
rosin spirit. The fraction distilling at 343°-346° is believed to be a 
diterpene, CaoHgo. Rosin oil resinifies on air oxidation; its solu- 
bility in 96 per cent alcohol varies rather widely, i.e., 50 to 70 per cent 
at ordinary temperatures, depending upon the conditions under which 
the oil has been made. 



bridged ring structure of Griin may account for this change by the rupture of the 
bridged ring by the hydrochloric acid. 



Chapter XII. Bicyclic Non-benzenoid 
Hydrocarbons. 

Turpentine and the Pinenes. 

Probably the most outstanding fact with regard to turpentine is 
its rapidly decreasing production. This is having the result that 
turpentine is being replaced in many of its applications by light petro- 
leum fractions, particularly in the case of paints and varnishes where 
it functions merely as a solvent. There are many industrial uses of 
turpentine, however, in which it appears to be indispensable, as in the 
manufacture of artificial camphor, terpineol and dammar varnish. 
The extent of the forests of the world, capable of producing turpen- 
tine, is well known and although the production of turpentine has been 
rapidly diminishing, reasonable sylviculture, as in France,^ will insure 
a supply of turpentine easily adequate for chemical and other special 
purposes. The United States, the principal turpentine producing 
country, produced 27,073,000 gallons of oil of turpentine in 1914, but 
only 17,737,000 gallons in 1919 in spite of a considerable increase in 
the number of producing plants, much higher prices per gallon in 
1919 and an increase in the output of "wood turpentine" and similar 
products of about one million gallons.^ At the present time the United 
States produces 75 per cent of the world's turpentine supply. Not 
many years ago the greater part of the world's turpentine supply was 
derived from North Carolina alone, but the turpentine forests of that 
State have practically disappeared, North and South Carolina together 
now producing less than one per cent of the American output. It is 
worth while to call attention to these facts, and a knowledge of the 
physical properties and chemical behavior of the pinenes should be 
brought to bear upon every important industrial use of turpentine 
with the object of conserving the supply for uses for which it is indis- 

' The pine tree plantations in Southwestern France cover an area of about 
2.5 million acres, o£ which about 2 million acres are privately owned. 

' Special Eeport on Turpentine, U. S. Bureau of the Census, Washington, May, 
1921; Veitch, U. S. Bur. Chem. Bull. 898 (1920). 

420 



BICYCLIC NON-BENZENOID HYDROCARBONS 421 

pensable and also affording relief by the substitution of cheaper 
material, so far as possible, in the case of consumers now handicapped 
by the high price of this solvent. 

In the United States the only important sources are the long leaf 
yellow pine, Pinus palustris, and Pinus heterophylla, both of which 
yield turpentine oils consisting of more than 90 per cent of the two 
pinenes. The terms gum turpentine, gum spirits or spirits of turpen- 
tine refer to the volatile oil, distilled unchanged, from the natural 
oleoresin collected from the trees. Wood turpentine ' made by distill- 
ing the wood in closed retorts with steam, or recovered by extracting 
the wood with a low boiling solvent, can be refined so as to replace 
turpentine for practically all solvent purposes, but when old stump 
wood is distilled an entirely different product is obtained, known com- 
mercially as "long leaf pine oil" or "pine oil," the chief constituent of 
which is terpineol * but other minor constituents which have been 
identified in it include the pinenes, Llimonene and dipentene, a and 
y-terpinene, borneol, fenchyl alcohol and traces of cineol and camphor. 
The greater part of such pine oil distills from 190°-220° and is useful 
for the manufacture of terpin hydrate and terpineol, for the flotation 
of copper sulfide ores and in certain solvent mixtures and cleansing 
compositions. Rosin spirit is a term employed for the mixture of 
hydrocarbons obtained by the destructive distillation of rosin. It 
contains very little of the pinenes, boils over a wide range of tem- 
perature and usually contains organic acids of unknown character; it 
usually gives the Liebermann-Storch color reaction with acetic anhy- 
dride and sulfuric acid. It will be obvious from their composition that 
neither pine oil nor rosin spirit can be substituted for turpentine in the 
manufacture of artificial camphor. 

Other products resembling turpentine find their way into com- 
mercial channels. "Recovered turpentine," a name sometimes applied 
to the mixture of terpenes, chiefly i-limonene, is produced by decom- 
posing the liquid hydrochlorides obtained as a by-product in the 
manufacture of bornyl chloride and artificial camphor. Approxi- 
mately 90 per cent of this product boils within the range 170°-180°, 
depending upon the rectification and purification of the product. The 
presence of chlorides, as indicated by the Beilstein or other halogen 
tests, is indicative' of such an origin. The oils given off during the 

»Cf. Frankforter, J. Am. (hem. 8oc. 28, 1467 (1906) ; Hawley & Palmer, TJ. S. 
Forest Service Bull. 109 (1912) ; French & Withrow, J. Ind. d Eng. Chem. 6, 148 (1914). 
•Teeple, J. Am. Ohem. Soc. SO, 412 (1908). 



422 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

melting of varnish gums are sometimes recovered but, even after good 
purification, have never found favor as thinners with paint and varnish 
manufacturers. The softer grades of Manila copal ° yield 10 to 12 per 
cent of its weight of oil, largely limonene and i-limonene, during the 
first part of the fusion, up to about 330°. Fresh Queensland Kauri 
gum, from Agathis robusta, yields about 11.6 per cent of nearly pure 
a-pinene.^ 

Parry ^ gives the following physical properties of turpentine as 
the result of the examination of a large number of commercial samples. 

Specific gravity at 15° 0.862- 0.870 

n 1.468- 1.473 

D 

Initial boiling-point 154.° -155.5° 

Distillate below 160° 72.% - 74.5% 

Distillate below 170° 95.% - 97.5% 

Iodine value, Hvibl 360. -375. 

Iodine value, Wijs 335. -350. 

The optical rotatory power is subject to considerable variation. 
Herty ' found the oil from P. palustris to vary from — 7° 26' to 
+ 18° 18' and that from P. heterophylla, — 29° 26' to -|- 0° 15'. 

The volatile oils of several species of pine found in the western 
States have been examined by A. W. Schorger,^ who finds that the 
turpentine from P. Ponderosa (Laws) and P. Scopulorum (Eng.) con- 
sists largely of P-pinene (q.v.) : that from P. Sabiniana is practically 
pure n. heptane and that from P. contorta consists largely of p-phel- 
landrene. These oils are not likely to become of commercial im- 
portance. 

Pinv^ sylvestris is the chief source of Swedish and Russian tur- 
pentine and contains sylvestrene in addition to dipentene and 
P-pinene " and possibly a-pinene and Z.camphene. Russian turpen- 
tine is a very indefinite product containing considerable proportions of 
phenolic or acid substances and oil boiling above 180°. 

French oil of turpentine, which constitutes nearly 20 per cent of 
the world's supply, is derived from Pinus pinaster (Pinus maritima) 
and is a true pinene turpentine consisting chiefly ^^ of Z.-a-pinene, 
[a] — 20° to — 38°. It is suitable for the manufacture of artificial 

' Brooks, PMUppine J. Set. 1910, 203. 

•Baker & Smith, "A Research on the Pines of Australia," Sydney, 1910, p. 376. 
' Chemistry of Essential Oils, Ed. 3, Vol. I, 17. 
'J. Am. Chem. 8oc. SO, 863 (1908). 
'Bull. 119, V. S. Dept. Agriculture. 
"Chem. Ztg. S2, 8 (1908). 

iiDarmois (Chem. Zentr. 1910 [1], 30) concludes, from studies on its optical rota- 
tion, that this turpentine consists of approximately 62% a-pineue and 38% ^-pinene. 



BICYCLIC NON-BENZENOID HYDROCARBONS 423 

camphor or other uses to which a true pinene oil can be put. With 
this brief review of the character of commercial turpentines the chem- 
istry of the pinenes and their more important derivatives will be 
noted. With the elucidation of the constitution of P-pinene and its 
synthesis by Wallach in 1908, the chemistry of the pinenes is prac- 
tically complete. 

a-Pinene is one of the most widely distributed of the terpenes, 
having been found in the essential oils of a large number of Coniferae, 
the grass oils, Lauraceae, Labiatas, etc. 

When it occurs together with other terpenes in oils used for the 
manufacture of flavoring extracts or perfumes, it is common practice 
to separate the terpenes by making use of their lesser solubility in 
dilute alcohol,^^ as compared with the esters, alcohols, aldehydes and 
the like which give such oils their aromatic value. The resulting ter- 
pene-free oils can be dissolved in much more dilute alcohol, thereby 
effecting considerable saving in the preparation of these solutions. 

Inactive a-pinene is one of the few terpenes which have been iso- 
lated in quite a pure condition. Fairly pure a-pinene can be obtained 
by fractional distillation of turpentine^' but a purer product can be 
obtained by preparing the nitrosochloride, purifying this by fractional 
crystallization and regenerating the a-pinene by decomposing the 
nitrosochloride by aniline ^* in alcoholic solution. Such a sample 
described by Schimmel & Co.^^ had the following physical properties: 

20° 

boiling-point 154.5°-155°, d 0.8634, n_-1.4664, optically inactive. 

lo ±J 

The highest observed optical rotations of a-pinene are [a]p. + 51-52° 

in the case of pinene isolated by A. W. Schorger ^^ from the oil of the 
Port Orford cedar (Chamcecyparis lawsoniana) . This is probably the 
purest natural a-pinene thus far discovered. A very pure d. a-pinene 
[aL, + 48.4° has been noted in the case of a specimen isolated from 

Greek turpentine (from the Aleppo pine, P. halepensis) ," and a laevo- 
pinene [o.]-p. — 48.63° from one of the eucalyptus oils, E. Icevopinea}^ 

"Bocker, J. prakt. Chem. (2) S9, 199 (1914) ; Vezes & MouUne, Bull. soo. chim. 
(3) SI, 1043 (1904). See section on physical properties (solubility). 

" Henderson & Sutherland recommend fractional distillation with steam, followed 
by ordinary distillation, taking the fraction boiling at 155°-156° as a-pinene. (J. 
Chem. Soc. 101, 2289 [1912]). 

"Wallach, Ann. 258, 343 (1890). 

=' Glldemeister, "Die Aetherisehen Oele," Ed. 2, Vol. 1, 308. 

"J. Ind. d Eng. Chem. 6, 631 (1914). 

" vezes, Bull. soc. chim. (4) 5, 932 (1909). 

"Smith, J. d Proc. Soc. H. S. W. Ji, 195 (1898). 



424 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Oils of high optical rotation give very poor yields of crystalline nitro- 
sochloride. 

a-Pinene is usually identified by preparing the nitrosochloride of 
the fraction boiling below 160°, which preparation is carried out by 
slowly adding concentrated hydrochloric acid to a strongly cooled 
solution of the hydrocarbon in glacial acetic acid and ethyl or amyl 
nitrite. On standing the crystalline nitrosochloride separates. After 
separating the crystals and recrystallization by dissolving in chloro- 
form and precipitating with methyl alcohol, the nitrosochloride melts 
at 103° but the nitrolamines give melting-points which are more use- 
ful and reliable for identification purposes. The pinene nitrolpiperi- 
dine melts at 118°-119° and the nitrobenzylamine melts at 122°-123°. 
In preparing the nitrolpiperidine a small proportion of nitrosopinene is 
simultaneously formed.^' In the case of pinene of high optical 
activity recourse may be had to oxidation by permanganate to the 
pinonic acids.^" The hydrochloride (bornyl chloride) made by pass- 
ing dry hydrogen chloride into cooled pinene, carefully dried by dis- 
tillation over sodium, has also been employed for the detection of 
pinene although both a and |3-pinenes give the same hydrochloride, 
melting-point 127°. 

The constitution of a-pinene has been determined largely by a 
study of its oxidation products. One of the most important advances 
made in clearing up the chemistry of the terpenes was the recognition, 
first clearly set forth by Wagner, that the hydroxyl group in a-terpi- 
neol is in position (8) and not position (4) . In this same remarkable 
communication of Wagner,^^ which was published in full in the Rus- 




a-pinene (Wagner) 



"Wallach, Ann. S^S, 252 (1888). Confirmed by Bushujew, J. Ruaa. Phys.-Chem. 
Soc. J,l; 1481 (1910). 

»Schimmel & Co. Semi-Ann. Kep. 1909 (1), 120. 
"Ber. 27, 2270 (1894). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



425 



sian language, Wagner published what have proven to be the correct 
constitutions of limonene, carvone, dihydrocarvone, carone and 
a-pinene. According to Wagner's structure for a-pinene, the forma- 
tion of a-terpineol and terpin is formulated as shown on the preced- 
ing page. Wagner seemed to have an almost uncanny ability to 
visualize the constitution of such substances. 

Baeyer showed that a series of oxidation products obtained by him 
also are in accord with Wagner's a-pinene constitution, which oxida- 
tions he expressed as follows,^^ 




a-pinene 




Hac 



:oM 



oc 



CH3-C-CH3 




a-pinonic acid pinoylformic acid 



HO,C 



CO,H 



CH,-C-CH, 
pinic acid 




Hqc. 

norpinic acid^^ 



Just as the four carbon ring in pinene is broken by dilute acids to 
form terpineol, so also is the four carbon ring in a-pinonic acid broken 
to give the methyl ketone of homoterpenylic acid, identical with the 
product of the oxidation of terpineol itself. (See page 426.) 

a-Pinene is usually associated with the isomeric hydrocarbon, 
P-pinene, and oxidation by permanganate gives the products of oxida- 

''Ber. 29, 2775 (1896). 

28 The cyclobutane ring has about equal stability In pinene, plnonic acid and 
pinoylformic acid, being split with about equal ease by diltite acids. In pinic and 
norpinic acid it is yery much more stable, this stablity being due apparently to the 
influence of the carboxyl group, parallel to the observations of Buchner on the effect 
of the carboxyl group on the stability of the cyclopropane ring. 



426 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



HOX 




a-pinonic acid 
CH, 




methyl ketone of 
homoterpenylic acid ^* 



a-terpineol 



tion characteristic of these two hydrocarbons. The oxidation is car- 
ried out^^ as follows: 5 cc. of the hydrocarbon are shaken for about 
three hours with an ice cold solution of 12 g. potassium permanganate, 
2.5 g. caustic soda, 200 cc. of water and 500 g. ice. After 3 hours 
saturate with carbon dioxide and remove the volatile unoxidized oil 
by distillation with steam, filter and evaporate in a current of carbon 
dioxide to about 200 cc. and extract several times with chloroform. On 
further evaporation the first salt to separate out is sodium nopinate, 
which on acidifying gives crystalline nopinic acid, melting at 125°. 
This acid is characteristic for |3-pinene. The sodium salt of pinonic 
acid is more soluble than the nopinate. Barbier and Grignard ^' have 
investigated the optically active forms of pinonic acid obtained by 
the oxidation of d. and J.a-pinene of high optical rotation. From 
J.pinene, [a] — 37.2° Z.pinonic acid was obtained, by permanganate 

oxidation and after distillation in vacuo, 189°-195° at 18 mm., sepa- 
rated in long crystals melting at 67°-69°, and [a] — 90.5°. From 

'* The constitution of homoterpenylic and terpenylic acids is discussed In connec- 
tion with terpineol and Umonene. 

^'sSchimmel & Co, Semi-Ann. Rep. 1910 (1), 165. 
"Compt. rend. Vfl. 597 (1908). 



BICYCLIC NON-BENZENOID HYDROCARBONS 427 

d.a-pinene, [a] + 39.4°, they obtained a mixture of racemic and 

d.pinonic acids, the latter melting when recrystallized at 67°-68°, 
[a]_^ + 89.0° and when mixed with the i.pinonic acid the racemic 

acid melting at 104° was obtained. 

Harries " investigated the action of ozone on a-pinene and by 
heating the resulting ozonide with acetic acid to 90° obtained an oil 
boiling over the wide range of 100°-142° under 12 mm., from which he 
prepared a semicarbazone melting at 214°-215° which was "prob- 
ably" pinonic aldehyde. On standing in contact with moist air, as 
in loosely stoppered containers, particularly in sunlight, turpentine or 
a-pinene is oxidized to pinol hydrate (sobrerol) which crystallizes 
from the oil.^^ From d. or ^.turpentine the correspondingly active 
pinol hydrates, melting-point 150°, are obtained. The d-l hydrate is 
formed on treating pinol with hydrogen bromide followed by hydrol- 
ysis by alkali. The relations of pinol hydrate and pinol are indicated 
by the results on oxidizing with permanganate. Each adds two 
hydroxyl groups, pinol to form pinol glycol, Ci^H-^fi . (OH) ^ and the 
hydrate to form sobrerythrite ^° CioHi^ (OH) ^. Pinol glycol is also 
formed by the action of dilute acids on the dioxide, pinol oxide, 
C10H16O2. Sobrerythrite is also formed by the action of hypochlorous 
acid on pinene and hydrolysis of the dichlorohydrin. In accord with 
the general behavior of the higher alkylene oxides (q.v.) concentrated 
alkalies convert the dichlorohydrin to the dioxide, pinol oxide, and on 
treating pinol oxide with dilute acids the 1.2 oxide is hydrolyzed to 
pinol glycol, leaving the oxide ring of four carbon atoms unchanged. 
Parallel with the behavior described in connection with cineol and 
other oxides, heating pinol hydrate with dilute acids causes the for- 
mation of the oxide pinol. These facts show clearly the relation be- 
tween the number of carbon atoms in the oxide ring and their relative 
stability. (See figure on page 428.) 

The behavior of turpentine or pinene on air oxidation is, in gen- 
eral, typical of the behavior of the olefines, including unsaturated 
petroleum oils. With all such substances air oxidation is accom- 

"Ber. i2, 879 (1909). 

" Formic acid is one of the products of the oxidation of turpentine by air and 
metal containers are accordingly sometimes corroded by old turpentine. Formic acid 
produced In this way is probably a product of the oxidation of yS-plnene, not a-pinene. 

" The sobrerythrite made from pinol hydrate melts at 156° ; a stereolsomerlc 
sobrerythrite made by the action of hypochlorous acid on pinene melts at 194°. 



428 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 




dicMorohydnne 



Ly cone KOH 




«.-pinene 

CK 
HO ' ' 




OH 
CH3-C-CH3 



OH 
H ' 



pinol hydrate 

/ 

fieatino + dil. acidi 



0. 



CH, 




9- 

CHrC-CH, 



HO. 
d.l H 

acids 



6obrerythriTe 

CH, 
HO 




CH, 



CHrC-CK 





KMnQ. 



CH3-C-CH3 



iinol oxide 



binol at y col 



inol 



panied by the formation of organic peroxides, water, carbon dioxide, 
simple organic acids, resinous substances and other oxidation products 
among which alcohols, aldehydes and ketones have frequently been 
noted. The oxidizing power of old turpentine was observed by Schon- 
bein and frequently investigated subsequently by others. The organic 
peroxides formed in this way are rapidly destroyed by heating to 140° 
and are hydrolyzed by water. As pointed out by Engler and Weiss- 
berg"^ the peroxides decompose, causing further oxidation of other 

■» The positions of the chlorine atoms and hydroxy! groups may be reversed ; in the 
above constitution their positions are arbitrarily assigned. The dichlorohydrine of 
pinene may be a mixture of Isomers, just as the addition of HOC! fo propylene gives 
a mixture of CHaCHCl.CH^OH and CH3CHOH.CH2CI. 

•1 Vorgange der Autoxidation, 1904, 



BICYCLIC NON-BENZENOID HYDROCARBONS 429 

material ^^ or unchanged oil or may even decompose breaking up the 
pinene molecule ; the formation of peroxides cannot be observed above 
160° although very rapid oxidation by air occurs at this temperature. 
It is well known that old oxidized turpentine "dries" more rapidly 
than freshly distilled turpentine and it is also a fact very generally 
observed that air oxidation greatly promotes resinification. Krumb- 
haar^^ noted that a sample of oil containing 0.002 g. active oxygen 
per cubic centimeter of turpentine "dried" very much faster than one 
containing 0.00057 g. active oxygen."* Among the products of the 
oxidation of turpentine by moist air in iron vessels is verbenone and 
the corresponding alcohol verberwl. From Grecian turpentine d.ver- 
benone was obtained and from French turpentine Z.verbenone and 
d.verbenol.'^ By the oxidation of pinene by benzoyl peroxide, an 
oxide is produced boiling at 102°-103° (50 mm.) which yields pinol 
hydrate on hydrolysis."* On oxidizing with hydrogen peroxide "' or 
mercuric acetate the four-carbon ring is broken; the chief product of 
the action of hydrogen peroxide on pinene (by 30 per cent hydrogen 
peroxide and glacial acetic acid) is a-terpineol. Small proportions of 
borneol, a little menthane-1.4.8-triol and resinous material are also 
formed. The expected pineneglycol was not found. Oxidation by 
mercuric acetate gave pinol hydrate."* 

By hydrogenating a-pinene in the presence of reduced nickel 
Sabatier "" obtained pinane, boiling-point 166°, and in the presence 
of catalytic copper an impure pinane, boiling at 163°-170°, results." 
Skita,*^ using platinum black, evidently did not get pure pinane, but 
Vavon*^ reports a quantitative yield of pinane, boiling-point 166° 
(755 mm.), [a]^ _|_ 22.7° from d.pinene or —21.3° for Lpinane from 

15° 
l.pinene from French turpentine, d -— ^ 0.861, and solidifying-point 

Xo 

about — 45°. Boeseken *" used pinene and platinum black in study- 

'= Sleburg (Biochem. Zt. J,S, 280 [1913]), Investigating the reputed efficacy of 
oxidized turpentine as an antidote for yellow phosphorus poisoning found that a com- 
pound of pinene and "phosphorous or hypophosphorous acid" was formed, but Will- 
statter and Sonnenfeld, Ber. 1,1, 3172 (1914), isolated a yellow crystalline compound, 
CioHiePaOj, by treating a solution of pinene and yellow phosphorus with dry air. 

" Farben Ztg. 18, 1280 (1913). 

** Determined by Klasson's method, Chem. Ats. 5, 3345. 

"Blumann & Zeltschel, Ber. I,e, 1178 (1913). 

=« Prileschajew, Ber. J,2, 4811 (1809). 

"Henderson & Sutherland, J. Ohem. Soo. 101, 2288 (1912). 

"Henderson & Agnew, J. GJiem. Soc. 9S, 285 (1909). 

"Oompt. rend. 1S2, 1254 (1901). 

"Ipatiev, Ber. i^, 3546 (1910). 

'^Ber. J,S, 3585 (1912). 

*'Compt. rend. 11,9, 997 (1909). 

"iJec. trail. cMm. So, 288 (1916). 



430 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

ing the effect of solvents on the rate of hydrogenation; in formic acid 
and in ethyl alcohol the hydrogenation is very slow and the catalyst 
becomes poisoned. Glacial acetic acid, as recommended by Will- 
statter, was most satisfactory. When using this solvent cyclopropane 
is slowly reduced to propane but under the same conditions the cyclo- 
butane ring in pinene is not attacked. During the war Sabatier, 
Mailhe and Gaudion** investigated the decomposition of pinene at 
high temperatures in the presence of various metallic catalysts. 
Large scale experiments on several tons of turpentine, using catalytic 
copper at 550°, gave about 21 per cent of hydrocarbons capable of 
being nitrated. No dehydrogenation was observed at 350°. At 600° 
to 630° in the presence of copper the decomposition was extensive, 
forming considerable gas and a mixture of hydrocarbons boiling from 
30° upwards and containing butylenes, amylenes, isoprene, hexylenes, 
aromatic hydrocarbons, etc., the mixture closely resembling the prod- 
ucts resulting from the decomposition of petroleum oils under these 
conditions, or the light liquid condensed from Pintsch gas. Also as 
in the case of petroleum hydrocarbons, passing turpentine over nickel 
at 600° gave rapid deposition of carbon and much gas rich in hydro- 
gen until the catalyst was rendered inoperative by the deposited 
carbon. 

As noted above, in connection with the identification of a-pinene, 
pinenes of very high optical activity give no crystalline nitrosochloride 
when the usual method of preparation is followed, and Kramers*' 
showed that the yield of the nitrosochloride varied inversely as the 
rotation although the yield almost never exceeds 40 per cent of the 
theory. The crystalline nitrosochloride obtained is optically inactive 
and although a crystalline product can be obtained by first mixing 
strongly d. and J.pinenes, no crystalline product can be obtained by 
mixing the nitrosochloride solutions obtained by separately treating 
strongly rotatory d. and Z.pinenes.*^ Tilden investigated the matter 
and concluded that the poor yield from pinene of high rotation is due 
to the destructive effects of the heat internally or locally generated in 
the reaction mixtiure.*' Lynn^* has recently succeeded in preparing 
optically active a-pinene nitrosochloride from the highly rotatory 

"Compt. rend. 168, 926 (1919). 

"Proc. Wise. Pharm. Assoc. 1892, 66. 

" Glldemeister & Kohler, Wallach Festschr. 1909, 432. 

"J. Chem. Soc. 85, 759 (1904). 

"J. Am. Ohem. Soc. U, 361 (1919). For this purpose Lynn modlfled the usual 
method for preparing nitrosochlorldes, using ethyl nitrite, absolute alcohol and alcoholic 
hydrogen chloride, the acid not beine in excess. 



BICYCLIC NON-BENZENOID HYDROCARBONS 



431 



d.a-pinene from the Port Orford cedar, previously described by 
Schorger, and also regenerated d.a-pinene from this nitrosochloride 
having a rotation of [a] -|- 53.75° (in 4 per cent alcoholic solution) 

which is the highest value yet reported and agrees well with the high 
value, + 51.52°, previously reported by Schorger for the natural 
pinene from this cedar. The active nitrosochloride, [a] -|- 322°, 

melts at 81°-81.5°, and is markedly soluble in all the common sol- 
vents, which probably accounts for the fact that it was not discovered 
earlier. The d.nitrolbenzylamine melts at 144°-145° and the nitrol- 
piperidine at 84°. Nevertheless, to account for the low yields of 
nitrosochloride Lynn suggests that the four-carbon ring may be broken 
to give 6-nitroso-8-chloro-A'-p-menthene, or may react to give a 
product CioHjoNO + HCl in a manner similar to the reaction of 
nitrosyl chloride on n.heptane.*' 

When pinene nitrosochloride is treated with sodium methoxide, 
a methyl ether derivative is formed,^" melting-point 102°, whose 
chemical behavior indicates the constitution. 



HON 




HON 




However, the chief result of the action of alcoholic caustic alkali on 
pinene nitrosochloride is the elimination of HCl in the usual way to 
■ form nitrosopinene, 



HON=i 




HON 




a-pinene nitrosochloride nitrosopinene, M.-P. 130°-131° 

"Lynn, J. Am. Chem. Soc. il, 367 (1919), finds that n. heptane reacts with NOCl 
In sunlight to give HCl. ammonium chloride and a mixture of heptanones. 
"Deussen & Phillpp, Ann. 369, 62 (1909) ; S7i, 112 (1910). 



432 CHEMISTRY OF THE NON-BENZBNOID HYDROCARBONS 



By warming with aqueous oxalic acid the oodme group is hydrolyzed 
to the ketone, carvopinone,^^ but in acetic acid solution with oxalic or 
hydrochloric acids the four-carbon ring is broken forming carvone. 



HON 





carvopmone 



by dilute acids 



carvone 



By reduction with zinc dust and acetic acid nitrosopinene yields the 
unsaturated amine, pinylamine '^ and a saturated ketone, pinocam- 
phone ^^ CH 



HON 




pinylamine 



pinocamphone 



" Wallach, Ann. S^e, 231 (1906) ; boiling-point 94°-96° (12mm.), readily converted 
to carvone by heating with dilute acids. 

=2 Wallach, loc. cit.; Pinylamine boils at 207°-208°, dj^g„ 0.944. The nitrate Is 

sparingly soluble in water which can be used for its recrystallizatlon. The hydrochloride, 
meltlnK-nolnt 229°-230°, decomposes on heating to give ammonium chloride and cymene. 
"Wallach, Sl,6, 235 (1906) ; seo, 92 (1908) ; S89, 185 (1912). The yield of pino- 
camphone by the reduction of nitrosopinene is about 22%. It boils at 211°-213° and 



BICYCLIC NON-BENZENOID HYDROCARBONS 



433 



The first application of the method of exhaustive methylation of 
amines and their subsequent decomposition, which has been exceed- 
ingly useful in the study of the constitution of alkaloids, to the prepa- 
ration of terpenes is the recent work of Ruzicka." On hydrogenating 
pinylamine the saturated amine pinocamphylamine is formed, which 
on exhaustive methylation gives the trimethylpinocamphyl-ammo- 
nium hydroxide, the decomposition of which yields pure a-pinene, as 
follows, 




pinylamine pinocamphylamine 



trimethyl 
base 



a-pinene 



It is of interest to note that the four-carbon ring in pinocamphone is 
very much more stable to acids than the unsaturated ketone, carvo- 
pinone. The same stability is noted in the corresponding alcohol, 
pinocampheol,'^ made by the reduction of pinocamphone. 

In general the halogen of alkyl halides ^^ may be substituted by 

N 
the triazo group, — N< 1 1 . When a-pinene nitrosochloride is treated 

N 
in alcoholic solution, with sodium azide, reaction takes place at about 
40° to give a beautifully crystalline pinenenitrosoazide melting at 
120°. Sodium ethoxide decomposes the azide to nitrosopinene. The 
chemical behavior of pinenenitrosoazide, and its physiological effect, 
is that of the aliphatic triazo derivatives in general. By heating with 
water the azide melting at 120° is partially isomerized to an azide 
melting at 126° and hot water alone breaks the four-carbon ring in 
the latter azide, losing nitrogen also, to form hydroxydihydrocarvox- 
ime." 

has a density of 0.959 (20). It yields an oxime melting at 86°-87° and a semicar- 
bazoue melting-point 208°. On oxidation it gives a-pinonic acid and an isomeric cam- 
phoric acid, CioHisOi, melting at 186°-187°. 

"Ruzlcka & Trebler, Helv. OUm. Acta. S, 756 (1920). 

"Wallach, Ann. S89, 188 (1912). 

»<| Thus ethylenechlorohydrin reacts with NaNj to give trlazoethyl alcohol. Vinyl 
bromide, which does not react with sodium azide, is an exception, which is another 
illustration of the stabilizing effect of an adjacent double bond upon a halogen atom, 

"Forster & Newman, J. Chem. Soc. 99, 245 (1911). 



434 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



HONq 




nitrosoazide, M.-P. 120° nitrosoazide, M.-P. 126° 

When a solution of ethyl diazoacetate in a little d.l.a-pinene is 
slowly added to a mixture of the pinene and copper powder at 160°- 
165°, nitrogen is vigorously evolved and the resulting ester can be 
oxidized, through several intermediate products, to methylcyclopro- 
pane -1.2. 3. -tricarboxylic acid. Buchner,^* who has also applied 
this method to the study of the constitution of camphene and bor- 
nylene, considers that the results are best interpreted by Wagner's 
formula for a-pinene. 




tricyclooctane 
derivative 



RQC-CH ^"' 



^ CH'^ N 



CC^H 



CQH 



methylcyclopropane- 

1 .2.3.-carhoxylic 

acid 



Bromine reacts energetically with a-pinene in cooled, dry carbon 
bisulfide to give a dibromide (reaction proceeds further with excess 
bromine, HBr being simultaneously evolved). When the crude di- 
bromide is distilled with steam considerable decomposition occurs but 
one of the products is a crystalline dibromide, CioHjeBrj, of unknown 
constitution but which probably belongs to the camphor series."' 

Verbenone: This ketone derivative of pinene was discovered in the 



''Ber. Ii6, 2680 (1913). The trlmetbyltricyclooctanecarboxyllc acid, noted above, 
melts at 165° 

"Wagner & Ginsberg, Ber. 29, 890 (1896). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



435 



essential oil of verbena °'' and has more recently been investigated by 
Blumann and Zeitschel, who found it in turpentine which had been 
considerably oxidized by the air.°^ It has a camphor and mint-like 
odor and its constitution was shown (by oxidation to pinononic acid, 
and other properties) to be as follows: 



HC 




CH3 

C 
\ 



CH, 



= C 



\ 



\ 



\ 



\ 



\ 



\ 







CH3 / 
\ / 

c 

\ 



/ 



CH 



\ 



\ 



\ 



\ 



\ 



CH, 



CH3 / 

\ / 

C 

\ 



/ 



CH 



CH, 



HO,C 



/ 



/ 



/ 



\ 



\ 



/ 



\ 



\ 



CH, 



/ 



/ 



./ 



CH, 



/ 



H 

verbenone 



C 
H 

pinononic acid 



The fact that the double bond in pinene should apparently be pre- 
served, may be explained by the initial hydration of the double bond, 
then oxidation of the CHj group and subsequent splitting off of water 
to form a double bond in the original position. Catalytic hydrogena- 
tion, using colloidal palladium, yields the saturated ketone, dihydro- 
verbenone,*^ isomeric with pinocamphone. 

The corresponding alcohol, verbenol,^^ also occurs in turpentine 
oxidized by air. The alcohol readily composes when distilled or when 
heated with acetic anhydride, forming verbenene, CjoH^^, which 

«° Kerschbaum, Ber. .13, 885 (1900). 

"Ber. ie, 1178 (1913). Verbenone boils at 227°-228°, or 100° at 16mm. melts at 
6.5, has a density of 0.9780 at 15° and [a]j-, + 249.62°. Its oxime melts at 115°. 
■2 Dihydro-d.verbenone, CioHioO, is an oil boiling at 222°, dj^go 0.9685, semiear- 

bazone melting at 220°-221° and oxime at 77°-78°. 
" BoiUng-polnt 216°-218°, djg. 0.9742. 



436 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

hydrocarbon probably has two double bonds in a conjugated position 
as in a-terpinene. Dehydration of verbenol with phosphoric oxide or 
zinc chloride gave cymene. When Z.verbenene, prepared from ver- 
benol, is brominated in chloroform the crystalline dibromide, melt- 
ing at 70°-72°, is formed. The d.dibromide from d.verbenene nat- 
urally melts at the same temperature but the racemic dibromide melts 
at 50°-52°. Oxidation of verbenene by permanganate yields norpinic 
acid melting at 175.5°-176.5°, and treatment with zinc chloride yields 
p-cymene. Blumann and Zeitschel '* regard verbenene as having the 
constitution shown below, I ; on reduction by sodium and alcohol two 
atoms of hydrogen are added (a reduction usually possible when the 
double bonds are conjugated) and the resulting hydrocarbon, dihydro- 
verbenene or "8-pinene" they regard as having the constitution indi- 
cated by II. 





/. verbenene 


", 




II. 


dihydroverbenene? 


d,,o 


0.8867 


B.-P. 




158° 


-159° (762 mm.) 


"15° 


1.4980 
159°-160° 


^20°- 
,20° 






0.8625 


20° 








° D 

B.-P 


1.4662 


"Ber. Si. 887 (1921). 




'__ 









BICYCLIC NON-BENZENOID HYDROCARBONS 



437 





verbenol 



verbenene 



An alcohol isomeric with verbenol and also possessing the bridged 
ring structure of pinene, is myrtenol, an alcohol occurring in myrtle 
oil as the acetate.^^ Its constitution is shown by the fact that reduc- 
tion of the corresponding chloride by sodium and alcohol yields 
a-pinene.°^ 




Oxidation by chromic acid yields the corresponding aldehyde myr- 
tenal, but permanganate oxidizes it to d.pinic acid. 

The conversion of pinene to derivatives of borneol is well known, 
the best example being the formation of bornyl chloride (so-called 
pinene hydrochloride) by the action of dry hydrogen chloride on 



"Soden & Elze, Chem. Ztg. 89, 1031 (1905). 

"•Semmler & Bartelt, Ber. iO, 1363 (1907) ; myrtenol boils at 222°-224° (760rom.) 
or 102°-105'' {9mm.). 



438 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

pinene at about 15°. When bornyl chloride is prepared from pinene 
in the usual manner, the product is usually optically inactive but 
Barbier and Grignard*' noted a rotation of [a] — 25.20° for the 

hydrochloride, melting-point 127°, made from i.-a-pinene from 
French turpentine, and a d.pinene hydrochloride (bornyl chloride), 
[«]„+ 33.19°, melting-point 127.1°, has been prepared ^^ from d.a- 

pinene from Greek turpentine. The hydrochloride made by Lynn 
from highly active d.a-pinene from the Port Orford cedar was inac- 
tive, from which observations, together with many other observations 
of similar kind, it is evident that racemization occurs very readily, 
but under certain conditions, eflBciency of cooling or rate of reaction, 
the activity may be partially preserved. In preparing limonene mono- 
hydrochloride partial racemization occurs, the degree of racemization 
apparently being influenced by the rate of introducing the hydrogen 
chloride, as shown by Vavon."' Pinene hydroiodide (bornyl iodide) 
was made by Aschan'" by digesting bornyl chloride in ether with 
magnesium iodide; the iodide is easily reduced by zinc in acetic acid 
to camphane. 

True pinene hydrochloride has not been detected among the reac- 
tion products of a-pinene and hydrogen chloride, but was synthesized 
by Wallach from nopinone by the Grignard reaction, thus making 
m^hylnopinol, and replacing the hydroxy 1 group in this alcohol by 
chlorine by means of phosphorus pentachloride,'^ 




nopinone 




methyl nopinol 



pinene 
hydrochloride 



"Bull. 800. chim. (4) 15, 26 (1914). 

" Tsakalotos, J. pharm. chim. i), 97 (1916). 

"Bull. soc. chim (4) 15, 282 (1914). 

'"' Ber. J5j 2395 (1912) ; d. or (.pinene gives a h.vdroiodide melting at —3° to — 5° ; 
d.l.pinene gives the racemic hydroiodide melting at — 12°. Silver oxide in dilute alcohol 
converts the iodide into an evidently new unsaturated alcohol, CioHnOH, boiling-point 
a07°-211°. 

"WaUach, Ann. S5S, 246 (1907). 



BICYCLIC NON-BENZENOID HYDROCARBONS 439 

True pinene hydrochloride, as contrasted with bornyl chloride, is 
very unstable and decomposes at its boiling-point, 200°-205°, and 
is very readily converted to dipentene dihydrochloride by the action 
of hydrogen chloride; bornyl chloride is not affected by hydrogen 
chloride. By treating pinene dibromide with zinc in alcoholic solu- 
tion a tricyclic hydrocarbon, melting at 65°-66°, is obtained. A di- 
iodide, prepared by Frankforter and Poppe,'^ is very unstable, entirely 
losing its iodine merely on standing or by distilling a few times. 

Anhydrous oxalic acid gives a relatively small yield of bornyl 
esters, dipentene and terpinenes being the chief products (see Artifi- 
cial Camphor). Acetic acid at 200° also gives a certain amount of 
bornyl acetate.'^ The oxalic acid reaction was the basis of the first 
industrial process for the manufacture of artificial camphor. 

When pinene is treated with HCl in the presence of moisture, or 
at too high temperatures, oily mixtures are obtained, the chief product 
being dipentene dihydrochloride. Under the best conditions the yield 
of crystalline bornyl chloride does not exceed 75 to 78 per cent of 
the theory. The liquid, oily chloride mixture contains bornyl chloride 
in solution, also dipentene dihydrochloride and lesser amounts of other 
substances. Barbier and Grignard'* have investigated these hydro- 
chloride oils, converting these hydrochloride oils into the magnesium 
compounds and treating the latter with oxygen and also with carbon 
dioxide. In addition to bornyl chloride, they found indications of the 
presence of fenchyl chloride. AschanJ^ has carefully investigated 
these oily hydrochlorides, having at his disposal comparatively large 
quantities of material made incidental to the manufacture of artificial 
camphor. By the action of alkali on the chlorides he obtained a com- 
plex mixture of hydrocarbons and showed that the low-boiling fraction 
contained (1) d.Lbornylene (which yields d.Z.camphoric acid on oxida- 
tion) , (2) a bicyclic hydrocarbon boiling at 144°-145° which he called 
a-pinolene, and (3), a tricyclic hydrocarbon, boiling-point 143°, which 
was quite stable to permanganate and which he named ^-pinolene or 
tricyclene. This hydrocarbon, which has been obtained as one of the 
products of the decomposition of fenchyl chloride by Aschan ^^ and by 
Sandelin,'' is probably identical with the cyclofenchene of Quist.^' 

^'J. Am. Ghem. Soo. 88, 1461 (1906). 

"Austerweil, Compt. rend. V,8, 1197 (1909). 

■••■Bull. aoc. chim. (4) 7, 342 (1916). 

"Ber. J/O, 2750 (1907) ; Ann. 337, 27 (1912). 

"Ann. SSy, 27 (1912). 

"4»n-. S96, 297 (1913). 

■"Ann. in, 278 (1918). 



440 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

By decomposing fenchyl alcohol by heating with potassium acid sul- 
fate, Quist obtained two hydrocarbons, one being the low-boiling 
"cyclofenchene" or P-pinolene. Fenchyl alcohol cannot decompose to 
water and an unsaturated hydrocarbon, forming a double bond with an 
adjacent carbon atom, as will be evident from its constitution. Other 
hydrocarbons may be formed from p-pinolene by rearrangement. Quist 
confirms Aschan as to its stability to permanganate but discovered 
that the three-carbon ring is evidently broken by the addition of 
bromine, forming a well crystalline dibromide of unknown constitu- 
tion. The chemistry of the fenchenes (q.v.) into which these deriva- 
tives of pinene lead, is still in a very unsettled condition. As regards 
their formation from a-pinene Aschan recalls that when hydrogen 
chloride reacts with tetramethyl ethylene, a rearrangement occurs. 



CH3 CH3 

\ / 

C = C 

/ \ 

CHo CH, 



+ HCl CH3 

> \ 

CH3 — C — CHCI.CH3 

/ 
CH, 



which is analogous to the addition of HCl to pinene, and if we recall 

CH3 

that the CHj and >C< groups in the four-carbon ring are 

CH3 

equivalent as regards their spatial relations to the rest of the mole- 
cule, we may write the rearrangement of the initial hydrochloride as 
follows, 



CH 




bomyl 
chloride 



BICYCLIC NON-BENZENOID HYDROCARBONS 



441 



H,C- 



H,C 



CH, 



CH- 



-CH 



/ 



CH, 



CH- 



./ 



./ 



-C< 



CH, 



CH, 




CH3 

chloride of fenchyl alcohol 



According to Aschan and Quist the formation of P-pinolene (cyclo- 
fenchene), from fenchyl alcohol or fenchyl chloride is to be expressed 
as follows, 




fenchyl alcohol 



Isopinene is the name given by Aschan " to a hydrocarbon, boiling- 
point 154.5°-155.5°, d 0.8658, n 1.47025, obtained by reacting 

upon (3-pinolene with hydrogen chloride and then decomposing the 
hydrochloride with aniline. Aschan identified cis-apocamphoric acid 
among the oxidation products of iso-pinene. Aschan reasons that 
isopinene, barring rearrangements, can have only structure I or II 



" Chem. Zentr. 1909 (2), 26. 



442 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



H,C 



H 
-C- 



2y vy C/ — CHj IljC'- 



H 
-C- 



-C — CH, 



CH, — C — CH, 



H,C 



-i: 



H- 



or 



-CH, 



H,C 



CH3 — C — CH3 

CH 

II 



CH 



Wallach considers that di.fenchene has the constitution represented 
by I, and also II best accounts for the formation of apocamphoric 
acid. 

H H 

-C C — CH, H,C C CO-CH, 




CH 



CH, 



-i- 



CH, 



H,C 



isoptnene 



H^C- 



H^C 



H 

-C- 



c 

H 

fenchenonic acid 

— CO,H 



-CO,H 



CH, — — C — CH, 



-C- 
H 



-CO,H 



apocamphoric acid 

The formation of isopinene by the rupture of the three-carbon ring 
in (3-pinol€fne and the subsequent removal of HCl may be understood 
by the following reactions, 




^-pinolene 
B.-P. 142°-144° 



^-pinolene 

hydrochloride 

M.-P. 26° 



BICYCLIC NON-BENZENOID HYDROCARBONS 



443 




H 

isopinene 

Tricyclen: When camphene is treated with nitrous acid, cam- 
phenylnitrite, CmHuNOa, is formed *° and when this derivative is 
treated with concentrated sulfuric acid, with good cooling an excellent 
yield of tricyclenic acid is obtained.*^ Its constitution has been shown 
by Komppa ^^ to be as shown below. Attempts to oxidize tricyclenic 
acid or the hydrocarbon tricyclene by permanganate to a cyclopro- 
panetricarboxylic acid, as Buchner and Weigard have done in the case 
of the condensation product of bornylene (q.v.) and diazoacetic ester, 
was without definite result^' but the three-carbon ring in oo-amino- 
tricyclene is split by concentrated hydrochloric acid to form cam- 
phenilane aldehyde and ammonium chloride. The ester of tricyclenic 
acid can be reduced by the method of Bouveault and Blanc to "tri- 
cyclol" and the latter can be oxidized by chromic acid in acetic acid 
solution, without breaking the three-carbon ring, to the corresponding 
aldehyde. This aldehyde is readily converted by the hydrazine 
method of Kishner ^* and Wolff ^^ to tricyclene, the yield being prac- 
tically quantitative.'" 




H 
tricyclenic acid tricyclal tricyclol tricyclene 

Pure tricyclene (Lipp) boils at 151.6°-152° and melts at 64°-65°." 
Tricyclene is unchanged by boiling (in benzene) with zinc chloride 

»» Jagelklsche, Ber. SB, 1501 (1902). 

" Bredt & May, Chem. Ztg. 1909, 1265. 

"Ber. il, 2747 (1908) ; U. 1536 (1911). 

•'Komppa, loc. cit. Lipp, Ber. 53, 771 (1920). 

"Chem. Zentr. 1911 (2) 363, 1925. 

"Atm. S9i, 86 (1912). 

'"Lipp, Ber. S3, 772 (1920) ; tricyclol melts at 111°-112° and tricyclal melts at 
85°-90° (semlcarbazone 219°-220°). 

"Moycho & Zlenkowski, Ann. 3^0, 24 (1905), give M.-P. 67.5°-68° 
Eilkman {Chem. Zentr. 1907 [2], 1210), gives M.-P. 66.5°, B.-P. 152.5 
(Sen 46, 312 [1913]), gives M.-P. 62.5°-63°, B.-P. 152°. 



B.-P. 152°-152.8°. 
Roth & Ostling 



444 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

but is converted to camphene by heating to 160° with sodium bisul- 
fate. 

Tricyclene is also formed by the action of mercuric oxide on 
camphor hydrazone {v. camphene) . 

When tricyclene reacts with chloroacetic acid, an ester of cam- 
phene hydrate is first formed.^* This and other evidence indicates 
that the three-carbon ring is easiest broken between carbon atoms 1 
and 2 or 1 and 6. Thus tricyclene yields isocamphane *^ when hydro- 
genated over catalytic nickel at 180°, but when passed over nickel 
at 180° without adding hydrogen, tricyclene is isomerized to cam- 
phene. Bromine yields a liquid dibromide of unknown constitution. 
Hydrogen chloride passed into a cold ethereal solution of tricyclene 
forms a well crystalline hydrochloride melting at 125°-127° and 
camphene yields the same hydrochloride under the same conditions. 
Meerwein regards this chloride as the true camphene hydrochloride 
corresponding to Aschan's camphene hydrate. This hydrochloride 
decomposes on standing at room temperature, recalling the similar 
behavior of chlorinated gasoline and kerosene hydrocarbons (of un- 
known constitution). Free hydrogen chloride, particularly in alcohol 
solution, accelerates the change of this chloride to isobornyl chloride, 
melting-point 158°. 

^eta-pinene is a constituent of commercial American and French 
turpentine and, according to Vavon,"" American turpentine contains 
about 27 per cent of this terpene. Baeyer and Villiger discovered 
the, sparingly soluble nopinic acid by the oxidation of turpentine by 
cold, alkaline permanganate solution. Further oxidation of nopinic 
acid by heating with lead peroxide (in water) yields nopinone.'^ This 
ketone is converted to 4-isopropylcyclohexenone by heating with 
dilute acids. The constitutions of nopinone and nopinic acid have 
been shown to be those suggested by Baeyer. The oxidation of 
P-pinene by the customary reactions proceeds normally. The yields 
of the various oxidation products are small but nopinic acid can be 
isolated without great difficulty. Small proportions of P-pinene can 
thus be detected with certainty. 

M Meerwein, Ber. 5S, 1820 (1920). 
'"Lipp, Ann. 382, 265 (1911). 
"Compt. rend, m, 997 (1909). 

"Ber. 29, 25, 1923 (1896). The oxime of nopinone is an oil, but the semiear- 
bazone melts at 188.5° ; nitric acid oxidizes nopinone to homoterpenylie acid. 



BICYCLIC NON-BENZENOID HYDROCARBONS 



445 




^-pinene 



^-pineneglycol 
M.-P. 75°-77° 



nopinic acid 
M.-P. 126° 



nopmone 



By the use of Reformatsky's reaction, condensation with bromo- 
acetic ester by zinc, Wallach made the nopinol acetic acid which 
decomposes with loss of water and COj in two ways according to the 
conditions employed. By heating with acetic anhydride p-pinene 
and an acid melting at 85°-86° is obtained. Wallach "^ represents 
the synthesis of |3-pinene as follows. 




nopinone 



nopinolacetic 
acid 



^-pinene 



Reduction of nopinone gives the corresponding alcohol, nopinol, in 
two modifications, a crystal form melting at 102° and a liquid form. 
By the Grignard reaction methylnopinol (pinene hydrate), crystals 
melting at 58°-59°, and ethylnopinol, melting-point 43°-45°, have 
been prepared. Methylnopinol is readily changed by five per cent 
sulfuric acid to a-terpineol, but nopinol is stable to dilute acid, illus- 
trating again the influence of changes in other parts of the molecule 
upon the stability of the four-carbon ring in the pinenes. Hydration 
also gives cis-terpin hydrate, melting at 117°. Heating nopinone 
with dilute sulfuric acid gives 4-isopropyl-A^-cyclohexenone.''^ 

Hydrogenation of P-pinene gives pinane identical with that derived 
by the hydrogenation of a-pinene."* P-pinene does not form a nitro- 

" Ann. 36S, 9 (1908) ; 368, 7 (1909) ; 356, 231 (1907). Nopinone melts at about 
0°, boils at 209° ; nopinol acetic acid melts at 85°-86°. 
"Rimini, Oazz. chim. Ital. i6 (2), 119 (1916). 
"Vavon, Compt. rend. ISO, 1127 (1910). 



446 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

sochloride, but nitrous acid yields a nitroso-P-pinene discovered by 

Pesci and Bettelli "^ and which Wallach showed was characteristic 

for p-pinene. When turpentine is hydrated by dissolving in acetic 

acid and acetic anhydride and adding a little 50 per cent aqueous 

benzene-sulfonic acid, the P-pinene reacts first, which behavior may 

be utilized in purifying a-pinene from p-pinene.^* 

Fairly pure p-pinene can be obtained by fractional distillation of 

the terpenes in hyssop oil, taking advantage of the fact that p-pinene 

boils approximately 10° higher than ordinary pinene; p-pinene from 

20° 
this source showed, boiling-point 164°-166° d,.„ 0.8650, n-— 1.47548. 

it) ±j 

Wallach's synthetic P-pinene showed boiling-point 163°-164° d 

22° 
0.8675, [a] — 25° 5', n — - 1.4749. 



The Fenchenes. 

Three hydrocarbons, known as a, p and y-fenchenes, are derived 
from the ketone fenchone or fenchyl alcohol. The fenchenes have 
not been positively identified in any natural product and their struc- 
ture has been arrived at by reference to the parent substances and, 
more recently, by methods of synthesis. Like the chemistry of cam- 
phene and bornylene, the chemistry of the fenchenes has only recently 
been made clear, although the nature of the puzzling rearrangements 
shown to occur in this series, are far from being understood. The 
current literature contains a great deal of work on these derivatives 
but the constitutions of the principal members of the group appear 
to be definitely determined. 

Fenchone: This ketone closely resembles camphor in its chemical 
behavior but is more resistant to oxidizing agents. It can accord- 
ingly be purified from other substances by oxidizing the impurities 
with concentrated nitric acid or by permanganate and can also be 
prepared readily by oxidizing the corresponding alcohol, fenchyl 
alcohol, which occurs in old root wood of the yellow pine, Pinus 
palustris, and is therefore a constituent of wood turpentine distilled 
from old stump wood. d.-Fenchone occurs in fennel oils and i.fen- 

"Oaez. chim. Ital. 16, 337 (1886) ;■ Wallach, Ann. SW, 246 (1906). 
•"Barbier & Grignard, Bull. soc. chim. (4) s, 139 (1908) ; S, 512, 519 (1909). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



447 



chone in thuja oils.°^ Fenchone does not form a hydroxymethylene 
derivative, indicating the absence of a — CHj — CO — group. By 
converting fenchyl alcohol to the chloride and decomposing the 
fenchyl chloride by heating with aniline, "fenchene" was produced. 
By oxidizing this unsaturated hydrocarbon by permanganate oxy- 
fenchenic acid is formed which may be further oxidized to fencho- 
camphorone. As a result of a detailed study of these products and 
the known properties of fenchone Wallach ^^ proposed the constitutions 
shown below for these substances, the correctness of which was soon 
proven by their oxidation to apocamphoric acid."" 

H CO,H. H 

-C C< H,C C C = 

OH 




CH, 




CH, 



oxyfenchenic acid 
H,C- 



CH, 



H^C 



H 
-C- 

-i- 
i- 

H 



fenchocamphorone 
-CO,H 



CH, 



-CO,H 



apocamphoric acid 

Wallach's constitution for fenchocamphorone is also confirmed by its 
synthesis in a very direct manner, by decomposing the lead salt of 
homoapocamphoric acid by heating,^"" 
H,C CH CO,H H^C CH CO 



H,C- 



CH,— C— CHj 
CH — 



CH, 



•CO3H 




CH, 



" Fenchone melts at 5° to 6°. The physical properties of a specimen regenerated 
from the semicarbazone [Wallach, Ann. ses, 195 (1908)] were as follows, boiling-point 

192°-193°, d^go 0.948, [0]^+ 62.76° (higher in alcohol solution) n^^l. 46355. Fen- 
chone does not form a phenylhydrazone but readily gives an oxime, d. and (. melting at 
164°-165°, inactive form melting at 158°-160° [Wallach, Arm. 878, 104 (1893)]. The 
semicarbazone forms very slowly ; Wallach recommends allowing an alcoholic solution 
of the ketone, aemicarbazid hydrochloride and sodium acetate to stand for two weeks 
[Ann. S5S, 211 (1907)]. The semicarbazone crystallizes from dilute alcohol In long 
prisms melting at 182°-183°. 

"Ann. SOO, 320. 

"Ann. 315, 293 (1901). 

'°° Komppa, Ber. 44, 395 (1911). The racemic semicarbazone of fenchocamphorone 
melts at 220°. 



448 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



By reacting upon a-fenchocamphorone with methyl magnesium 
iodide Komppa and Roschier^"^ have synthesized-a-fenchene. The 
tertiary alcohol farmed by this reaction is decomposed by distilling at 
ordinary atmospheric pressure to give the hydrocarbon. 

OH 

CH^ CH C = CH, CH C< 

CH, 
CH,-C;-CH, + CHjMgl 

H CH, CHo 



« • t t 



CH, 



.A 



CH,— C— CH, 



:h- 



CH, 



CH„ 



CH- 



C — CH, 



CH, 



CHg— C— CH3 

-in- 



or 



CH 



CH, 



CH 



i- 



CH, 



CH3-C-CH 
-CH — 



C = CH, 



CH, 



The physical properties and chemical behavior of the synthetic 
a-fenchene ^"^ are practically identical with Aschan's isopinene (q.v.), 
but Wallach considers that a-fenchene contains the >C = CH^ group, 
on account of its formation together with p-pinene when nopinolacetic 
acid is dehydrated.^"^ 

In a similar manner Komppa and Roschier have treated di.p-fen- 
chocamphorone with magnesium-methyl iodide, thus forming methyl- 
P-fenchocamphorol.^"* When this alcohol is heated with potassium 
acid sulfate a mixture of two unsaturated hydrocarbons is obtained, 
consisting mainly of di.p-fenchene and an endocyclic hydrocarbon 
y-fenchene. The p hydrocarbon yields d.l. hydroxy-P-fenchenic acid 
melting at 124°-125° on oxidizing with permanganate, and on further 
oxidation by the lead peroxide and sulfuric acid method dJ.p-fencho- 
camphorone is obtained. The latter ketone by further oxidation 
yields apofenchocamphoric acid. A fourth fenchene, termed isoallo- 
fenchene by Semmler, and isofenchylene by Quist, is called 6 or iso- 
fenchene by Komppa. The p-fenchene of Komppa is Wallach's 
D, d. or L. I. fenchene, or Semmler's isofenchene. 



0.8660 and refractive Index 



20° 



1.47045. The hydrochloride, melting-point 35°-37° 



^'^J. Chem. Soc. 112 (1), 466 (1917). 

"- The synthetic hydrocarbon of Komppa boils at 154°-156°, has a density 
20° 
D 

is Identical with that made from isopinene. Ozone gives racemic fenchocamphorone 
and r a-fenchenylanic acid, melting-point 105°. 
""Ann. 36S, 3 (1908). 
"^Cliem. Abs. IS, 2864 (1919). Fenchocamphorol melts at 66°-67° and bolls at 

77° (9mm.) ; p-fenchene boils at 146°-148», d^ 0.8539. 



BICYCLIC NON-BENZENOID HYDROCARBONS 
CH, 



449 




C = CH, 



OH. 

tnethyl-^-fenchocamphorol 



^-fenchene 




C — CH, 



y-fenchene 



Fenchone itself has been synthesized by Ruzicka ^°^ in the manner 
indicated by the following reactions. 

(1) Levulinic ester and ethyl bromoacetate are condensed by 
means of zinc and the resulting lactonic ester is converted into the 
nitrile by treating with potassium cyanide, 

CH3 

H^C — CO — CH3 HjC — C — CH.CO^R 



HjC — CO2C2H5 



-j-BtCU^.CO^'R 



\ 

OH 

»H,C-COAH, 



CH3 

H^C — C — CH^CO^R 

/ 

H,C — CO 



H,C- 



CH3 

■C — 

A: 



CN 



2V. — v. — COjH. 



H2CO2R 



H,C — COoR 



CH 
H,C — C- 
■ 1 CH2-CO2H. 
H,C — CO,H. 



(2) The above tricarboxylic acid is condensed to a cyclopen- 
tanone derivative by means of sodium in benzene, and the ester of the 
resulting product is condensed with bromoacetic ester. 



>«Ber. 50, 1362 (1917). 



450 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 
CHj CHj 

•C — CO,R H,C — C — < 



H,C- 



H,C 



CH, 
— C = 



CO,R 



+ Br.CH,CO,R 
> 



H,C 



OH 



CHjCOjR 



(3) The above hydroxy acid is converted to the unsaturated acid 
and the latter reduced to the saturated acid. 



H,C- 



H,C- 



CH, 

-h- 

CH, 

i: 



■CO,R 



H,C 



CH3 

-i- 



■CO,R 



CH.CO,R 



i: 
-i: 



H, 



H,C — CH — CH„CO,R 



(4) On heating the lead salt of the above acid methylnorcamphor 
is formed which on methylating by Haller's method, using sodium 
amide and methyl iodide, fenchone and fenchosantenone are formed. 

CH, 



H,C — C CO2H 



i: 



H, 



H^C — CH — CH^ — CO^H 



CH, 



H,C- 



H,C 



■CO 



H- 



:H — CH, 



fenchosantenone 



CH, 

H,C — C CO 

CH, 

I — CH — 6H, 

methylnorcamphor 

CH3 

H,C C— 



H,C- 



CO 



CH, 



H, 



.A 



H- 



C< 



fenchone 



CH, 
CH, 



The above structure of fenchone explains the formation of fencholic 
acid from fenchone by heating with caustic potash.^"* 

'"■Wallacli, Ann. 369, 71 (1909). 



H,C 



BICYCLIC NON-BENZENOID HYDROCARBONS 
CH, CH, 



H^C C- 



CH, 

in- 



-CO 



'< 



CH, 



H,C C- 



by KOH 
CH, > 



CH, 



461 



-CO,H. 



H,C CH CH< 

fencholic acid 



CH3 
^CH, 



By the action of sodium or potassium acid sulfates on fenchyl 
alcohol at 170°-180°, in a current of carbon dioxide, a fenchene is 
obtained boiling at 151°-153°, D 0.8660. On oxidation it yields 
hydroxyfenchenic acid melting at 138°-139°.i" 

Fenchyl chloride, like the higher alkyl halides in general, reacts 
very slowly with magnesium in ether. After one week and treating 
with carbon dioxide the reaction mixture gives chiefly hydrofenchene 
carboxy lie acid and hydrodifenchene.^"' 



CH, 



CH. 



-i 



CH, 



CH, 

-A- 

H 



-CH- 



CO2H 



C< 



CH, 



CH3 

hydrofenchenecarboxylic acid 
M.-P. 45°-46° 
(racemic acid M.-P. 52°-53°) 



CH, 



CH, 



CH3 

-i_ 

CH, 

-A- 



-c- 



H 



C< 



CH3 
~CH. 



hydrodifenchene 



By the action of ozone on a-f enchene Komppa and Hintikka ^"^ 
obtained fenchocamphorone, which behavior is also readily explained 
by Wallach's formula for this hydrocarbon. 



CH, 



CH, 



H 
-C- 



-CH, 



CH3 — C — CH3 

c 

H 



+ O3 



CH, 



H 

-C- 



-CH, 



CH, 



2 Y V 2 

CHo — C — CH, 



CH, 



-A- 

H 



C = 



""J. Chem. 80c. m, 398 (1917). 

'M Komppa & Hintikka, Ber. ifi, 645 (1913). 

"»Ber. 47, 936 (1914). 



452 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The saturated hydrocarbon, fenchane, has been prepared by Kish- 
ner's admirable method. By heating d.fenchone, [a]_^ -j- 62.8°, with 

hydrazine hydrate the d.hydrazone is first formed (melting-point 

66°-57°) and by heating the hydrazone with sodium ethylate fen- 

20° 
chane is formed,^^" boiling-point 149°, d — 0.8316 and Isevorotatory 

4° 

[a]^ — 18.11° (4 per cent solution in alcohol). 

"•Wolff, Ann. S9i, 86 (1912). 



Chapter XIII. Bicyclic Non-benzenoid 
Hydrocarbons. 

Camphene and Bornylene. 

Although these two hydrocarbons have quite different structures 
they are considered together on account of their relations with pinene 
and bomyl halides, and with borneol and camphor. Until recent 
years the existence of bornylene, as distinguished from camphene, was 
not recognized. The chemistry of these two hydrocarbons, particu- 
larly that of camphene and its oxidation products, is somewhat in- 
volved but by 1914 the accumulation of evidence was such that the 
constitution of these two hydrocarbons could be considered as esta'b- 
lished beyond any reasonable doubt. Particularly is this true since 
the synthesis of camphenic acid by Lipp '■ and the investigations of 
Haworth and King.^ 

Camphene and bornylene are both solid and crystalline at ordinary 
temperatures, but only camphene has been found in nature, occurring 
in both d. and I. forms. Camphene was early recognized as a product 
of the decomposition of bornyl chloride, the ^.chloride giving I. cam- 
phene and the d.chloride giving d. camphene.^ 

Although camphene crystallizes well and purification by recrystal- 
lization has been carried out in most cases, the physical properties 
reported for camphene are far from being in agreement. The dif- 
ferences noted in physical properties are doubtless due to the presence 
of bornylene or to some other as yet unidentified hydrocarbon. 

When borneol derivatives are decomposed to hydrocarbon under 
milder conditions the chief product is bornylene, a hydrocarbon first 
recognized by Wagner.* Bornyl iodide, made from borneol and hydri- 
odic acid (which is identical with the product of HI and pinene), 
gives mainly bornylene on treating with alcoholic caustic alkali. 

^Ber. kt, 871 (1914). 
'J. Chem. Soc. 105, 1342 (1914). 

• Bertbelot, Ann. 10, 367 (1859) ; Kachler, Ann. 179, 96 (1879) ; Tilden & Arm- 
Btrong, Ber. IS, 1753 (1879). 
*Ber. Si, 2302 (1899). 

453 



454 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 







O 

S 


i 


o 


o 

S : 




fe 


^ 


r-( 


S 


*^ 




rH 


1-4 


rH 


S 

^ 





o? a> us 
I + + 



o O » O %o 00 ° S* 



M 
a, 



S 






U3 o CO 

»fl 00 30 

00 00 ^ ^ 00 

00 000 



s 




I 

o 



"5 








0' 


0' 


g 


s 



00 






t T T 



W5 



T4 


.9 


■s 


^ 


0> 


-e 


u 




S 




s 


s 




a 


d 


3 









+3 


iwj 











3 


.s 


a 


s 


t4 


p. 


■§ 





+a 


i 


oT 


(U 


•3" 




d 




.3 


4} 


2 


1 


^ 


.a 


.g 


CO 


A* 


Ck 


n 



s 



•a -s 



■3 -3 

oT S 

a o 

CI o 



_aoo'-5 



BICYCLIC NON-BENZENOID HYDROCARBONS 455 

Also when borneol xanthogenate is heated it decomposes to give chiefly 
bornylene, a method discovered by Tschugaeff.^ Henderson and 
Caw ^ showed that when bornylene is prepared by Tschugaeff's 
method, the impurities can be removed by oxidizing with hydrogen 
peroxide, the bornylene so purified melting at 113°, and boiling at 
146°-147° (750 mm.). Bornylene has recently been made from cam- 
phor by Ruzicka ^ by the conversion of camphor to bornylamine by 
heating with ammonium formate in an autoclave at 60 atmospheres 
pressure; the resulting amine was subjected to the method of exhaus- 
tive methylation with methyl iodide (bornyltrimethylammonium 
iodide melts at 245°). The free trimethyl base is gently decomposed 
to give bornylene melting-point 111°-112°. 

Bredt has also made a very pure bornylene from camphocarboxylic 
acid. By electrolytic reduction of this acid to the corresponding 
hydroxy acids ^ and distilling the acetylborneolcarboxylic acid the 
unsaturated acid, bornylenecarboxylic acid,' is obtained and on react- 
ing upon this acid with hydrogen bromide a mixture of a and p-bro- 
mocamphanecarboxylic acids are obtained. The P-bromo acid is 
decomposed on heating with aqueous alkali to bornylene, bornylene- 
carboxylic acid and a lactone. 

CH.CO^H CH.CO^H C — CO^H. 

C,H,,<| _^C3H,,<| ^CsH,,<|| + HBr 

C = CH.OH. CH > 

CH.CO^H CBr.CO^H. 

> C8Hi,< I and C8H„< | 

CHBr \ CH^ 

\ 

^-bromocamphene- \ 

carboxylic acid. \ CH 

C8Hi4<|| bornylene 

CH. 

The bornylene thus obtained had the following physical properties, 
melting-point 113°, boiling-point 146° (740mm.), [a] —21.69° 

(10.4% in toluene), [a] —26.96° (4.42% in methyl alcohol). 

Bornylene gives camphoric acid on oxidation, which indicates that 

"Tschugaeff & Budriek, Ann. 388, 280 (1912). 
'J. Chem. Soo. 103, 1543 (1912). 
■' Helv. chim. Acta. S, 48 (1920). 

■Bredt, Ann. S66, 1 (1909). These are ois and cis-trans isomeric forms of borneol- 
carboxylic acid, tlie cis acid melting at 102°-103° and the cis-trana melting at 171°. 
•Melting-point 112°-113°, boiling-point 158° at 13mm. 



456 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



the double bond is in the position shown, which structure is that for- 
merly supposed to represent the constitution of camphene, 
CH, CHo 



CH, 



CH 



CH, 



-C- 

-A 



CH 



CH, 



H- 



CH, C- 



CH 



CH 



CH, 



CH, 



,-A. _ 



CO,H. 



CO,H. 



bornylene camphoric acid 

Camphene forms an ozonide which on decomposition gives formal- 
dehyde-camphenilone and dimethylnorcampholide.^" Komppa and 
Hintikka ^^ have synthesized the latter substance and shown its con- 
stitution to be as represented in the following. 

CHj CH3 

CH, CH C< CH, CH C< 



CH, 



CH, 
-CH- 



CH3 + O3 



■ C = CH, 



i: 



camphene (Wagner) 



and 



CH, 



5h, 



CH 



C< 



H, 



CH 



CH3 
CH, 



CH3 
H, 

CH, CH C = 

dimethylnorcampholide 



C = 



camphenilone 
This constitution of camphenilone is supported by the fact that it 
does not form a hydroxymethylene compound ^^ and therefore does 
not possess a CH, group adjacent to the carbonyl group. Further 
evidence of the structure of camphenilone is given by the conversion 
of camphenilone by the action of sodamide, to the amide of the acid, 

CH, 



CH, 



CH., 



CH- 



■CH< 



H, 
H 



CH, 



CO,H 
which substance has also been synthesized.^^ 

"Harries & Palmen, Ber. iS, 1432 (1910). 

"Ber. liB, 898 (1909). 

"Moycho & Zienkowskl, Ann. S^O, 54 (1905). 

"Bouveault & Blanc, Compt. rend. U,t, 1314 (1908). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



457 



When camphene is oxidized by alkaline permanganate the chief 
product is camphenic acid, CiqHijO^, an acid isomeric with camphoric 
acid. A great deal of work has been done upon the structure of this 
acid, based upon which other constitutions for camphene have been 
proposed.^* However no reasonable doubt should exist as to its con- 
stitution since its synthesis by Lipp," in the following manner: The 
ethyl ester of 1 . 3-cyclopentanonecarboxylic acid was condensed, by 
Reformatsky's reaction, with a-bromoisobutyric ester in the presence 
of zinc. By decomposition with loss of water an unsaturated acid 
was formed, whose constitution may be either III or IV but on hydro- 
genating the saturated acid 1 . 3-carboxylcyclopentylisobutyric acid 
formed, which proved to be identical with d.J.cis-camphenic 



was 
acid.^* 



CH, 



CH, 



■CO 



H.CO,R 



CH, 



CH, 



OH 

CH^ 

-in. 

II. 



CH3 

-c< 

I CH3 

CO,R. 
■ CO,R. 



CH, 



CH, 



C- 



CH 



H 



C< 



CH3 
CH, 



CO,R 
CO^R 



III. 



CH==C 



or 



CH, 



CH, 



CH3 
■C< 
I CH3 
CO,R 



-CH — CO,R 
IV. 



CH, 



CH, 



■CH- 
CH3 

in- 



CH3 

■c< 

I CH3 

CO,H 
CO,H 



camphenic acid 



When camphenic acid is distilled it loses CO2 to form a ketonic 
acid, camphenonic acid, whose constitution may be inferred from the 
structure of camphenic acid. The d. and I. forms of camphenonic 

" Cf. review by Haworth & King, J. Chem. Boo. 101, 1975 (1912). 
"Ber. iy. 871 (1914) 

'" Camphenic acid is practically Insoluble in cold water, ligroin and carbon bisul- 
fide, but crystallines from hot water, melting-point 135°-137°, 



458 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

acid together with the d.l. acid are formed from camphenic acid made 
by the oxidation of strongly d. or I. camphene.^' 

CH, CH, 



CH, 



■ CH 



■C< 



CH, 



CH, 



CH- 



CH, 



CO,H 



CO,H 



CH, 



-CH 



■C< 



CH, 



CH, 



C- 



/ 



/ 



CH, 



C = 



CO,H. 



camphenic acid camphenonic acid. 

Fusion of camphenonic acid with caustic alkali or treatment with 
sodium and alcohol regenerates camphenic acid. 

Wagner's constitution for camphene is also supported by the work 
of Buchner and Weigand/* who condensed camphene with diazo- 
acetic ester and oxidized the acid so obtained to 1.1.2-cyclopropane- 
tricarboxylic acid. The camphene employed by Buchner melted at 
44°-45° and distilled at 156°-157°. Treatment with the ester at 
160°-165° in the presence of copper powder gave vigorous evolution of 
nitrogen and a good yield of the condensation product, 2 . 2-dimethyl- 
norcamphane-3-spirocyclopropanemethylcarboxylate. The relation 
of camphene to the condensation product and the oxidation product 
are as follows: 



CH, 



CH, 



H 

-C — 

CH, 



-C 
H 



•C< 



CH3 
CH, 



•C = CH, 



CH, 



CH, 



H 
-C- 



C< 



CH, 



-C- 
H 



CH3 
CH, 



camphene 



C — CH, 



CH.CO,R 



CO,H. 



-CH, 



/\ 

CO,H. CH.CO^H. 

The spiro ester is stable to permanganate in suspension in sodium 
carbonate solution. [Buchner and Weigard also succeeded in mak- 

"ABchan, Ann. J/IO, 240 (1915). 
"Ber. i6, 759 (1913). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



459 



ing the acid chloride, from which the amide was prepared, leaflets 
melting at 124°.] The purified amide readily yields the pure acid, 
melting at 108°. Reduction of the ester, by sodium in absolute 
alcohol, converts the CO2R group to CHjOH with rupture of the 
cyclopropane ring. 

Applying the same method to bomylene Buchner and Weigand " 
obtained 1.2.3-cyclopropane tricarboxylic acid. 




CH.CO^H. 



CH.CO3. 



When camphene hydrochloride is carefully treated with dilute 
alkali, camphene hydrate is formed, which can be decomposed to 
camphene having the same rotatory power as the original hydrocar- 
bon. The hydrate is therefore formed without causing any change 
in the carbon structure of camphene. Only two formulae for this 
hydrate are possible, one being a tertiary and one a primary alcohol, 
but the properties of camphene hydrate are clearly those of a tertiary 
alcohol, i.e., 

CH, 



CH, 



CH- 



i 



C< 



CH, 



H, 



■CH.- 



C< 



CH3 
OH 



CH, 



camphene hydrate 



" Ber. i6, 2108 (1913). The trimethyl ester of 1 . 2 . 3-cyclopropanetrlcarboxylic 
acid melts at 56°-57°, wbicb serves to distinguish It from its isomers. 



460 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

A stereoisomeric form of camphene hydrate is methylcamphenilol, 
obtained by the action of magnesium-methyl iodide on camphenilone. 
Both forms yield camphene on dehydration and probably bear a 
stereochemical relation with each other comparable to borneol and 
isobomeol.^" 

To explain the rearrangement which occurs when isoborneol is 
decomposed to form camphene, the intermediate formation of tri- 
cyclene has usually been assumed, 




isoborneol 



tncy 



:lene 



Tiffeneau^^ has proposed the theory that when alcohols are decom- 
posed with the formation of a hydrocarbon of a different carbon 
structure, as in the decomposition of pinacoline alcohol to tetramethyl- 
ethylene, that the intermediate product is a hydrocarbon having a 
bivalent carbon atom. In the case of isoborneol and its decomposi- 
tion to camphene this would be represented as follows. 




'"Aschan, Ann. ilO, 222 (1916). 
"Rev. gen. d. Sci. 18, 583 (1807). 



BICYCLIC NON-BENZENOID HYDROCARBONS 461 

Meerwein ^^ has tested both of these hypotheses. Camphor hydra- 
zome is decomposed by mercuric oxide, the intermediate compound 

C8H,,<| 

C = N.NH.HgOH being decomposed with evolution of nitro- 
gen, and it is a reasonable supposition that the bivalent carbon com- 

pound C< whose transitory existence is assumed by the Tif- 

feneau theory, would be formed and immediately rearrange to cam- 
phene, if this theory is correct. It is found, however, that tricyclene 
is formed almost quantitatively. 

The properties of tricyclene clearly show that it cannot be an in- 
termediate product in the conversion of isoborneol to camphene. 
Thus Meerwein shows that under the conditions by which isoborneol 
is almost quantitatively changed to camphene (heating with 33% 
sulfuric acid at 100°), tricyclene is practically unchanged. Also, as 
shown by Lipp,^^ heating tricyclene with fused zinc chloride is with- 
out effect although isoborneol is decomposed to camphene under these 
conditions. 

As regards the opposite reaction, the conversion of camphene to 
isoborneol (or acetate) , Meerwein shows that chloroacetic acid reacts 
more rapidly with camphene than with tricyclene, and consequently 
tricyclene cannot be an intermediate product in the conversion of 
camphene to esters of isoborneol. In these experiments evidence was 
found that tricyclene first forms an ester of camphene hydrate. When 
tricyclene or camphene is treated with hydrogen chloride in cold 
ethereal solution, a? very unstable hydrochloride is formed which Meer- 
wein regards as the true chloride of camphene hydrate. It is so 
unstable that on merely shaking the chloride with water at ordinary 
temperatures, camphene hydrate is formed; in alcoholic caustic potash 
the neutralization of the alkali takes place so rapidly that the per 
cent of the hydrochloride present can be titrated in the cold with 
N/2 caustic solution during one half hour. The most striking prop- 
erty of this hydrochloride is its rearrangement to the chloride of 
isoborneol, melting-point 158°, which takes place on warming with 
alcoholic hydrochloric acid, which probably accounts for the fact that 
this camphene hydrochloride was discovered only very recently." 

"Ber. BS, 1815 (1920). 
"Ber. SS, 769 (1920). 
" Meeiwein, loo. oit. 



462 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



Thus, when hydrogen chloride is passed into a solution of camphene 
in alcohol the product is mainly isobornyl chloride, but also contains 
more or less true camphene hydrochloride, thus accounting for the 
various melting-points recorded in the literature for camphene hydro- 
chloride, i.e., 118° to 158°. This chloride melting at 158° is the iso- 
bornyl chloride, evidence for which is its reduction by sodium and 
alcohol to camphane (dihydrobornylene) and its conversion to iso- 
bornyl acetate by treating with silver acetate in glacial acetic 
acid. 

Isobornyl chloride is much more stable than camphene hydro- 
chloride and is practically not affected by alcoholic caustic alkali at 
ordinary temperatures. Nevertheless isobornyl chloride is consider- 
ably less stable than bornyl chloride (made from pinene and HCl) 
since by heating for one hour with alcoholic caustic alkali bornyl 
chloride is scarcely attacked ^^ but isobornyl chloride is completely 
decomposed. In such a chloride mixture it is therefore possible to 
estimate fairly accurately the per cent of camphene hydrochloride, 
isobornyl and bornyl chlorides, by making use of their relative stabil- 
ities to caustic alkali. 

The facts point to reversible reactions between camphene and 
esters of camphene hydrate (chloride or acetate), and between the 
latter and esters of isobomeol. 






camphene 



acetate of 
camphene hydrate 



isobornyl acetate 



Thus, camphene hydrate can be prepared from isobornyl chloride. 
Methyl borneol and methyl fenchyl alcohol also appear to be in 
equilibrium in the presence of acids since Ruzicka ^° finds that by 
the action of sodium acid sulfate on either of these alcohols, the same 
mixture of methylcamphene and methyl-a-fenchene is obtained. 

>» Hesse, Ber. S9, 1127 (1906). 
"Helv. chim. Acta, l, 110 (1918). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



463 





methylborneol methylfenchyl alcohol 

Although Meerwein has produced good evidence to show that in 

the isobomeol ±5 camphene rearrangement the intermediate formation 

of tricyclene or a hydrocarbon containing bivalent carbon is extremely 

improbable, the mechanism of the rearrangement is as obscure as 

ever. This rearrangement is to be classed with others such as that 

discovered by Kishner.^^ 

OH 

/ 
CH2 ■ CH CH3 

-» I c 



CH2 — CH 



C< 

in 



CH3 

CH, 



CHo — CH, 



CH, 



CH, 



CH, 



and the well-known retropinacoline rearrangements; for example, the 
chloride 

CH3 

\ CH3 

CH, — C.CH,C1 * 



CH, 



/ 



CH, 



]> C — CH2CH3 



k 



and the like. , \ 

By the hydrogenation of camphene and bornylene the correspond- 
ing saturated hydrocarbons are obtained, the nomenclature of which 
is unfortunate. By reducing bornylene by the method of Sabatier 
and Senderens a "camphane" melting at 150° and boiling at 161°-162° 
was obtained by Henderson and Pollock ^* and the same hydrocarbon 
in a somewhat purer form was obtained from camphor by the decom- 
position of the hydrazone,^* according to the method of Kishner, the 
hydrocarbon made in this way having a melting-point of 156°-157° 
and boiling at 161° (757 mm.). From its relation to camphor it is 

" Chem. Zentr. 1908 (2), 1342; 19U (1), 543. 
"J. Ohem. Soc. 97, 1620 (1910). 
»Wol£E, Ann. S9i, 86 (1912). 



464 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



perhaps proper to call it camphane, which however confuses it with 
the isomeric hydrocarbon derived from camphene. The terms dihy- 
drocamphene and dihydrobornylene are much to be preferred. 

By heating isoborneol with zinc dust at 220° Semmler '" obtained 
a hydrocarbon, CiqHij, boiling at 162° and melting at 85°, and 
Vavon'^ reduced camphene in ether solution by platinum black and 
hydrogen and obtained a hydrocarbon probably identical with Semm- 
ler 's melting at 87°. Sabatier and Senderens obtained a liquid mix- 
ture from camphene which Henderson and Pollock'^ showed was a 
mixture of the camphane of Vavon and unsaturated hydrocarbons. 
The crude product obtained by Henderson and Pollock melted at 64° 
and the product obtained by Ipatiev,'^ "isocamphane," obtained by 
passing isoborneol over a mixture of nickel oxide and alumina at 
215°-220° with hydrogen at 110 atmospheres, and described as melt- 
ing at 63°-64.5°, is probably the crude camphane. 

A product called cyclocamphane has been made from cyclocam- 
phanone by Kishner's hydrazine method. Cyclocamphane melts at 
117°-118°.'* Angeli,^= who first prepared the ketone by the action of 
nitrous acid on aminocamphor, regarded it as an unsaturated ketone 
and accordingly called it "camphenone." The presence of the three- 
carbon ring in camphanone was shown by converting it (through the 
qxime and nitrile and oxidation) to cyclocampholenic acid and by 
further oxidation to cycloisocamphoronic acid. 



CQH 





cyclocamphane cyclocamphanone cyclocampholenic cycloisocamphoronic 

acid acid, M.-P. 228° 

Reduction of the ketone yields a new borneol, cyclocamphanol, melt- 
ing-point 174°-176°. 

Camphene, like P-pinene, does not form a nitrosite but the nitrosite 

"Ber. SS, 776 (1900). 

•^Compt. rend. Ii9, 997 (1909). 

•2 J. Ctiem. Soc. 107, 1620 (1910). 

"Ber. 45, 3205 (1912). 

"Holz, Z. angew, Ohem. in (1), 347 (1914). 

"Oazz. chim. Ital. iJ, (2), 44, 317 (1894). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



465 



conceivably formed as a labil intermediate product, decomposes to 
give nitrocamphene "" (melting-point of d and I forms 84°-85°, d.l.- 
nitrocamphene melting at 64°-66°). Bromine also shows a similar 
behavior, the group >C = CH2 adding Brj to form the labil 
>CBr — CHjBr which immediately decomposes to give the mono- 
bromo derivative >C ^ CHBr, camphenylidene-6-bromomethane.'' 
This bromide is capable of combining with hydrogen bromide (prob- 
ably reversible) to form 2-bromo-Q-bromo-camphene, melting at 
90°-91°. The corresponding camphenylidene chloride is inert to 
hydrogen chloride. 

Camphene condenses with formaldehyde (trioxymethylene) in 
acetic acid, to form a primary alcohol, from which a large number of 
derivatives have been prepared. Thus, oxidation of the new alcohol 
yields the corresponding aldehyde, which can then react with mag- 
nesium alkyl halides to give a series of diethylenic hydrocarbons of 
the camphenic type. 

Camphene combines with hypochlorous acid in cold dilute solu- 
tions to give a nearly quantitative yield of camphenechlorohydrin, 
melting at 93°. Reduction of this chlorohydrin with zinc and alcohol 
gives isoborneol; camphenechlorohydrin is therefore probably a-chlo- 
roisoborneol.^* Camphenechlorohydrin reacts with caustic alkalies or 
moist silver oxide to form camphenilane aldehyde, which is also 
obtained by treating campheneglycol (obtainable by permanganate 
oxidation of camphene) with dilute acids. The conversion of 1.2- 
glycols to aldehydes or ketones by dilute acids is quite a general 
reaction. The principal oxidation products of camphene are shown 
in the following diagram. 




camphene 



camphene glycol 
M.-P. 200° 



a-oxycamphenilanic 
acid, M.-P. 171° 



•"Llpp, Ann. S99, 241 (1913). 

"Langlols, Ann. chim. IS, 265 (1920). 

"Henaerson, Heilbron & Howie, J. Chem. Soc. lOS, 1367 (1914). 



466 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 




C-CO^H 



camphenilane aldehyde camphenilanic acid 
M.-P. 70° M.-P. 65° 



C-0 




camphenilone 
M.-P. 43° 



Reduction of camphenilone by sodium and alcohol gives camphenilol, 
the corresponding alcohol, CgHi^OH, melting at 84°. 



Camphor. 

The essential oil derived from the leaves or wood of Cinnamomum 
camphora *' is a complex mixture from which camphor is more or less 
perfectly separated before the oil comes into commercial markets. 
According to Bertram and Wahlbaum *" and Schimmel & Co. this 
essential oil contains, in addition to camphor, pinene, phellandrene, 
camphene, dipentene, dfenchene, d.limonene, bisabolene, cineol, safrol, 
eugenol, terpineol, citronellol, borneol and cadinene. Ordinarily a 
light terpene fraction is separated from commercial camphor oil as 
this is of little value, and the heavier oil, containing large proportions 
of safrol and eugenol, constitutes the chief commercial source of safrol, 
employed for the manufacture of piperonal. In addition to the above 
named constituents Semmler and Rosenberg*^ isolated a bicyclic 
sesquiterpene boiling at 129°-133° at 8 mm.; also a monocyclic diter- 
pene, CzoHsj, which they have named a-camphorene, and a second 
diterpene named p-camphorene which is distinguished from the a-hy- 
drocarbon by forming a liquid hydrochloride. So-called camphoro- 
genol reported and very imperfectly characterized by Yoshida,*^ evi- 
dently does not exist. 

The physical properties of camphor, as recorded in the literature, , 
are as follows, melting-point 175°," 176.3° to 176;5°," 178.4°;*^ 

"Parry ("Chemistry of Essential Oils," Ed. 3, p. 160 [1918]), has called atten- 
tion to a bulletin issued by the Monopoly Bureau, Formosa, according to which several 
varieties or species (7) of camphor trees are recognized but not yet distinguished 
botanically, whose essential oils do not yield camphor. 

•'»>/. prakt. Ohem. (2) ^9, 19 (1894). 

"Ber. i6j 768 (1913). 

"J. Ohem. Soc. i1, 782 (1885) ; Cf. Bertram & Wahlbaum, loc cit 

"Landolt, Ann. ma, 333 (1877) ; Beclimann, Ann. SSO, 353 (1889) 

"Foerster, Ber. 23, 2983 (1890). 

"Haller, Compt. rend. 105, 229 (1887). 



BICYCLIC NON-BENZENOID HYDROCARBONS 467 

density at 18° 0.9853; « boiling-point 204°," 209.1;" [a] 44.22° 

in 20 per cent solution in alcohol.*^ The latent heat of fusion** is 
8.23 calories and the latent heat of vaporization is 93.4 calories. 

Identification of camphor is best accomplished by preparing the 
oxime" melting-point 118° to 119°. As pointed out by Beckmann 
{loc. cit.) the oxime of d. camphor is Isevo-rotatory and the oxime of 
J.camphor is dextro-rotatory, amounting to ± 41.3°, in alcoholic solu- 
tion. The semicarbazone, melting-point 236°-238°, the p-bromo- 
phenylhydrazone ™ melting at 101°, the oxymethylene derivative 
melting at 80°-81° and the benzylidene compounds, have also been 
employed for the purpose of detecting or identifying camphor. The 
benzylidene compound of inactive, or synthetic, camphor melts at 78° 
but that of d. or t.camphor melts at 95°-96.° Camphor forms 
a series of compounds with mercuric iodide,'^ CioHi^O. Hgjlj; 
(C,oH,,0),Hg,I,; (C,„H,,0),HgJ, and (C,„H,,0)3HgeI,. Nitric 
acid forms an addition product CioHigO.HNOg, melting at 24°, and the 
existence of a second compound (CioHi80)2HN03, melting at 2.2°, is 
indicated by the freezing-point curves.'^^ Hydriodic acid forms 
(CioHigO) .HI, melting at 29°-30°, and phosphoric acid forms an 
addition product C10H13O.H3PO4, melting at 29°. 

Neither ordinary camphor nor its isomer epicamphor forms a 
cyanohydrin. Camphor, menthone, thujone and fenchone do not react 
with phenyl hydrazine. 



The Constitution of Camphor and Its Oxidation Products. 

The study of the constitution of camphor and its oxidation prod- 
ucts and derived substances constitutes a brilliant chapter of organic 
chemistry, and although the structure of camphor has been known 
with reasonable certainty for some time, the structures of some of 
the derived oxidation products are still subjects of research. Since 
this collection of researches is such a classic and has engaged the 
attention of many of the ablest organic chemists, it is worth while 

" Chautard, Jahreaber, 1863, 555 (ifor I.camphor) ; Malosse, Compt. rend. 15J,, 1697 

(1912), gives d^ 0.963. 

" Beckmann, loc. cit. 

"Jounlaux, Bull. soc. chim. (4) 11, 993 (1912). 

"Auwers, Ber. 2B, 605 (1889) ; Bredt, Ann. 289, 6 (1896). 

•"Tlemann, Ber. 28, 2191 (1895). 

"Marsh and Struthers, Proc. Chem. Soc. 21,, 267 (1909). 

K Shukoff & Kasatkin, J. Rusa. Phya.-Chem. Soc. il, 157 (1909). 



468 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



to review the matter somewhat more fully than some other related 
subjects. For the sake of clearness the historical method of review 
will not be followed. 

In the earlier work undue emphasis was put upon the fact that 
under certain conditions camphor could be converted (with very 
small yields) into para-cymene, also to carvacrol. In 1893 Bredt" 
unraveled the structure of one of the important oxidation products of 
camphor, i.e., camphoronic acid. On heating, camphoronic acid 
breaks up into carbon dioxide, isobutyric acid and trimethyl succinic 
acid, a change which Bredt represented as follows: 



HO,C- 



(a) 



CH, 



CH3 

.i- 

CO,H. 



CH, 



CH, 



CO, 



H 



■^ isobutyric acid 



(b) CH3 

HO2C — C — 

CH3 — • C — CH3 

CO2H. 
camphoronic acid 



CH, — CO,H HO,C 



CH, 

-i:' 



H 



CH3-CH-CO2H 



CH, 



.i- 

CO,: 



CH, or CH, 



CH, 



>C-CO,H 



trimethylsuccinic acid 



A little later Bredt's constitution for camphoronic acid was conclu- 
sively confirmed by Perkin and Thorpe," who made the acid by well- 
known reactions of synthesis. Bredt represented the oxidation of 
camphor, through camphoric acid, to camphoronic acid, as follows. 



CH, 



CH3 
•C — 



CH, 



CO 



CH, 



CH, 



CH, 



-C — CH, 

.in- 



CH, 



CO^H 



CH, 



-i- 

CH3 — i — CH3 — 

— CH CO,H 



camphoric acid 



"Ann. 29i, 55 (1896) ; Ber. SS, 3047 (1893). 
"J. qnem. Boo. 71, 1175 (1897). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



469 



CH, 



CH, 



CH, 



CH, 



-i 
-i. 



CO,H 



CH, 



CH3 

i- 



■CO,H 



CH, 



■CO,H 



CH, 



CH, 



\ 



io 



CH, 



OH 



camphononic acid 



CH, 



CH, 



CO,H 



CH3 
■C — 

.i- 

CO, 



CO,H 



CH, 



H 



camphoronic acid 

The hydroxy acid shown as an intermediate product in the above 
series of oxidations is usually obtained in the form of the lactone, 
camphanic acid, 

CH3 

CH, C C = 

\ 
\ 



CH, 



CH, 







CH, 



C- 



/ 



/ 



/ 



CO,H. 



The correctness of Bredt's constitution for camphoric acid is very 
directly shown by the synthesis of this acid, first by Komppa "^ and 
later by Perkin and Thorpe.^' By condensing ethyl oxalate with 
PP-dimethylglutaric ester, by means of sodium ethoxide, Komppa ob- 
tained the diethyl ester of diketoapocamphoric acid. 



CO,R 



H.CH 

-f- CH3 — C — CH3 
H.CH 



CO^R 



CO 



CH- 



CO,R 



CO2R 

••Ber. Si, 2472 (1901) : S6. 4332 (1903). 
"/. Ohem. Boo. 89. 795 (1906). 



CH, 



CO- 



C — CH3 



CO2R 



CO^R 



470 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



By the action of metallic sodium and methyl iodide a methyl group 
was introduced and the two ketone groups were then reduced, first 
to the dihydroxy acid, then by hydriodic acid and red phosphorus 
to the unsaturated acid dehydrocamphoric acid. The double bond 
in the latter acid was then reduced by adding HBr and reducing the 
resulting product by the well-known method of reduction by zinc 
dust and acetic acid, the product proving to be racemic camphoric 
acid. 



CO 



CH CO^R 



CH, — C — CH, 



CO 



CH CO,R 



CO- 



CH3 

.i- 



CO,R 



-> CH3 — C — CH3 



CO 



.i: 



CH, 



dihydroxy ] (dehydrocamphoric > 

acid J [ acid 



H CO^R 



CH3 

-C CO,H 

I 
J — > 



CH3 — C — CH3 
CHBr CH CO,H. 



CH, 



CH, 



CH, 



CH, 



■C- 

■|- 

-CH 



CO,H. 



CH, 



CO,H 



r — camphoric acid. 

Perkin and Thorpe's synthesis is even more conclusive.^^ Dimethyl- 
cyclopentanonecarboxylic ester was treated with magnesium-methyl 
iodide and the resulting alcohol converted first into the corresponding 
bromide and the latter into the nitrile, which, on hydrolysis, yields 
d.Z.camphoric acid. 

" The experimental details of Komppa's synthesis were published several years 
later (Ann. S68, 126; S70, 209 [1909]). Blanc and J. C. Thorpe published a paper 
calling in question the structure of the acid obtained by methylating diketoapocam- 
phoric ester, claiming this to be an o-methyl ether, not the c-methyl derivative (J. 
Chem. 80c. an, 836 [1910]). After an explanatory reply by Komppa (,ni4., 99, 29 
[1911]), Blanc and Thorpe admitted their error (Hid., 99, 2010 [1911]). Komppa's 
syntbesis has not since been questioned. 



BICYCLIC NON-BENZENOID HYDROCARBONS 

CH, 



471 



CH, 



CH, 



CH, 



CH, 



•CO 

■i- . 

■CH.CO 
CK 
C- 



CH, 



C- 



OH 



CH3 
H 

-Br 



CH, 



CH, 



CH3 — C — CH3 > 

I 
— CH. CO3 



CH3 

■C — 



-CN 



CHg C CH3 

I 

CH, CH CO,H 

CH,— 



CH3 

A- 



CH3 — C — CH3 > 

CH, CH CO,H 



CO^H. 



CHg C CHg 

CH3 ; CH CO^H . 

The conversion of camphoric acid to camphor had- already been 
effected by Haller.''^ Camphoric acid forms an anhydride, which on 
reduction by sodium amalgam, yields campholide, 

CO CO 

> C8H,,< > 



C,H,,< > 
CO 



CH, 



When campholide is heated with potassium cyanide it yields a nitrile 
which on hydrolysis is converted into homocamphoric acid. 

CO CO,K CO,H 

C,H,,< > + KCN ^ C,H,,< ^ C,H,,< 



CH, 



CH,CN 



CH,.CO,H. 



On heating the calcium salt of homocamphoric acid, Haller obtained 
camphor. 

CO, CO, 

C8H,,< > Ca > C,Il,^< 



CH,CO, 



CH, 



Dicarboxylic acids whose carboxyl groups are separated by two or 
three carbon atoms readily yield anhydrides, as in the case of succinic 

"Compt. rend. MS, 446 (1896). 



472 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

and glutaric acids, and the significance of the formation of camphoric 
anhydride was first pointed out by Baeyer.^' Homocamphoric acid, 
however, does not form an anhydride, indicating that the two carboxyl 
groups are separated by at least four carbon atoms, facts which agree 
with Bredt's constitution and the syntheses of camphoric acid, noted 
above. 

Camphoric acid exists in a form which does not yield an anhy- 
dride and to distinguish this form it has been called isocamphoric 
acid. Like ordinary camphoric acid the iso acid exists in d. and I. 
and a racemic form. These facts also harmonize with Bredt's con- 
stitution for camphor and the chemical evidence as to the structure 
of camphoric acid. The four active camphoric acids may be repre- 
sented as follows, 



CH,-C< 
C=H, 



CH3 



CO^H 



CH, — C< 



CO,H 



CH, — C< 



H 
CO,H 



CH, 



c.Hb 



CH, — C< 



CO2H 
H 



d. and I. camphoric acid 
CH, 



CH,-G< 



CO,H 



CH, — C< 



CO,H 



CsHg 



CH, — C< 



CO^H 
H 



CH, 



C.Hb 



H 

CH^ — C< 

CO2H 
d. and I. isocamphoric add 



In camphor, however, the two carbon atoms represented by the car- 
boxyl groups in the camphoric acids, are bound to each other and 
therefore there are only two active forms of camphor, i.e., d. and 
Z.camphor, corresponding to d. and ^.camphoric acid. In camphor the 
asymmetry is due to the CO group and optical activity disappears if 



"Ann. g76, 265. Camphoric anhydride may readily be prepared by heating the 
acid above its melting point, or by dehydrating by means of acetyl chloride. 



BICYCLIC NON-BENZENOID HYDROCARBONS 473 

this ketone group is reduced to CHj, as was shown experimentally by 
Aschan.** 

Epicampkor, or ^-camphor. It will be evident from the structure 
of ordinary camphor that another isomeric ketone should be capable 
of existence, and, in accordance with the nomenclature suggested for 
the hydrocarbon camphane, ordinary camphor would be a-camphor 
and its isomer p-camphor. The two ketones are related structurally 
to each other as follows, 

CH3 



I 
CH, C C = CH, C^ CH, 



'-2 




i 



CH3 — C — CH3 I 

■ CH, CH2 C C = 

H 
ordinary, or a-camphor Epicamphor, or ^-camphor 

In the conversion of camphor to epicamphor a reversal of the 
sign of optical rotation is observed, which may be summarized thus, 

d-camphor, [a] + 39.1° ^=5 Z-epicamphor, {a.]jy — 58.2°. 

CO 

Hydroxymethylene epicamphor, C8Hi^< | , like ordinary 

C = CHOH 

hydroxymethylene camphor, is formed when ^.epicamphor is treated 
with isoamyl formate and sodium in the presence of ether."^ It ex- 
hibits muta-rotation, increasing on standing, particularly in the 
presence of sodium ethylate; freshly prepared material showed 
[a] — 125.5° and after adding a trace of sodium ethylate the rota- 

D 
tion increased to [a] — 146.7°. The decomposition of i.epicam- 

D 
phoroxime by dilute sulfuric acid proceeds in a similar manner to that 
of camphoroxime, forming epicampholenonitrile, with rupture of the 
ring as in ordinary camphoroxime. The nitrile may be hydrolyzed 
to l.a-epicampholenic acid, but the behavior of this acid differs from 
ordinary a-campholenic acid in not rearranging to an isomeric acid 
corresponding to p-campholenic acid. An interesting attempt to pre- 

"Ann. S16, 229 (1901). 

"Perkin & moey, J. Chem. 8oc. 119, 1090 (1921). 



474 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

pare p-camphor was made by Haller and Blanc.^^ Campholide, made 
by reduction of camphoric anhydride, yields homocamphoric acid and 
camphor as follows, 

CO CO^K CO^H CO 

C3H,,< >0^C8H,,< ^C,li,,< ^C8H,,<| 

CH3 CH.CN CH.CO^H CHj 

Haller and Blanc prepared p-campholide but this substance did not 
react with potassium cyanide. Wagner "^ believed that he had suc- 
ceeded in preparing p-borneol by applying the Bertram-Wahlbaum 
reaction to bornylene, but it was later shown that his bomylene must 
have been very impure and his results are considerably variant from 
those of Perkin and Bredt. Wagner's method was carefully tested by 
Bredt and Hilbing,^* who employed a very piure bornylene and a mix- 
ture of borneols was obtained which they were unable to separate 
and on oxidation, ordinary camphor only could be identified. Epi- 
camphor was first described in a preliminary paper by Perkin and 
Lankshear °^ and almost simultaneously by Bredt.®' However much 
the best method of preparation was worked out by Perkin and Bredt 
jointly, their method consisting in treating methyl d-bornylene-3- 
carboxylate "' with hydroxylamine in the presence of sodium meth- 
oxide. On heating, the product decomposes forming epicamphor, the 
reactions involved probably being as follows, 

C.C(OH)=N.OH C-N:C = CNRCO^H 

CsH,,<|| >C,H,,<|| >C«H,,<|| > 

CH CH CH 

bornylene-S-hydroxamic 
acid 

C — NH^ C = NH C = 

CsH,,< II > C,H,,< I > C,H,,< I 

CH CH^ CH, 

epicamphor 

Epicamphor has an odor similar to that of ordinary camphor, it 
melts at 182°, boils at 213°; its oxime melts at 103°-104° and the 

"Compt. rend. HI, 69T (190.5). 
" Ber. S6, 4602 (1903). 
".;. prakt. Chem. (2) 8/,, 783 (1911). 
•■'Proc. Chem. Soc. 27, 167 (1911). 
"Chem. Ztg. 35, 765 (1911). 

"Bredt, Ann. SiS, 200 (1906) ; Sm, 1 (1909) ; Bredt & Perkin, J. Chem. Soc. lOS, 
21S2 (1913) ; Furness & Perkin, J. Chem. Soc. JOS, 2025 (1914). 



BICYCLIC NON-BENZENOID HYDROCARBONS 475 

semicarbazone melts at 237°-238°. Sodium and alcohol reduce epi- 
camphor to the corresponding epiborneol, melting-point 181°-182.5°. 
Like ordinary camphor, the new ketone does not react with hydrogen 
cyanide and is not reduced by zinc dust in acetic acid. The chemi- 
cal properties of epicamphor do not differ markedly from ordinary 
camphor but "favorable action of epicamphor on the beat of the heart 
does not become apparent until the solution administered is about 
four times stronger than that which produces the same effect in the 
case of camphor." 

In connection with the discussion of the constitution of camphor 
and camphoric acid it will be convenient tp review briefly several 
related derivatives. The nomenclature in this series of acids has 
been very much confused and the molecular rearrangements which 
some of them undergo made the determination of their constitution a 
matter of considerable difficulty. An extension of our knowledge of 
the pinacone-pinacoline rearrangement has assisted materially in 
clearing up the relationships of this group of substances. 

Bredt°^ has reviewed the nomenclature of the camphonene and 
laurolene series and suggests abolishing the designations "lauronolic 
acid" and "campholactone." Two series of unibasic unsaturated acids 
are known which are derived from camphoric acid. To one series 
belong camphonenic acid and lauronolic acid and since the latter acid 
is unsaturated it may more appropriately be called laurolenic acid. 
Both of these acids contain a carbonyl group which is attached to 
the tertiary carbon atom of camphoric acid. In the other series the 
carbonyl group is attached to the secondary position and includes 
campholytic and isocampholytic acids (P-campholytic acid). It is 
now known that the substances formerly known as lauronolic and iso- 
lauronolic acids, bihydrolaurolactone and tsobihydrolaurolactone are 
not merely differentiated by the different positions of the double bond, 
as was formerly considered to be the case, but possess different carbon 
structures since camphonenic acid (below) (iso or y-lauronolic acid) 
still contains the grem.dimethyl group of camphoric acid; lauro- 
lenic acid (formerly lauronolic acid) does not possess this 
group. 

For the purpose of a key for reference, the revised nomenclature 
suggested by Bredt is given, as follows. 

"J. pralet. Chem. (2) 87, 1 (1913). 



476 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

I. Camphonene and Camphonone Series. 
CH, 



CH, 



CH. 



i- 
i. 



CO,H. 



CH, 



CH3 

■C — 



CH, 



CH, 



CO2H. 



CH, 



-i 



CO,H 



CH, 



CH 



dehydrocamphoric acid 
CH3 

, C CO,H. 

I 
CH, — C — CH, 



CR^ === CH 

camphonenic acid 

CH. 

-A- 



CH, 



.i 



H, 



CH, 



CH, 



COJi 



CH, — C — CH, 



:h.nh. 



camphonanic acid. 
CH3 
CH, C CO,H 






CH, 



aminocamphonanic acid 
CH3 



CO 



CH, 



CH, 



in. 



CH3 

OH 



CH 



CH3 — C — CH3 



:h- 



camphonolic acid 



CH, 



CH3 

i- 



camphonololactone 



CO,H. 



CH3 — C — CH3 

CH, C = 

camphononic acid. 

II. Lawolene and Laurolane Series. 
CH3 

CH CH, 



CH 



CH, 



CH3 

I 
-C- 



C — CH, 



CH, 



CH, 



i 



c- 



COjH 



•CH, 



CH, 



laurolene 



laurolenic acid 



BICYCLIC NON-BENZENOID HYDROCARBONS 



477 



CH, 



CH, 



A. 



-CO,H 



H — C — CHs 
CH2 CH CHj 

laurolanic acid 

CH,— 



CH. 



CH3 

■C- 



CH. 



CH, 



CH, 



in. 

i- 



CO,H 



CH, 



CH, 



laurololic acid 



CO 



CH.CH3 




laurololactone 



Some of the synonyms of the 

Bredt's nomenclature 

Camphonolic acid 
Laurololic acid 
Camphonololactone 
Laurolanic acid 

Laurololactone 

Laurolenic acid 
Camphonenic acid 



above terms are as follows: 

Synonym 

Hydroxylauronic acid 
Hydroxy acid of campholactone" 
Isocampholactone ''" 
Dihydrolauronolic acid 

{Campholactone 
Bihydrolaurolactone 
Lauronolic acid 
y-lauronolic acid 



Bredt '^ has also suggested that substituents in the single methyl group 
of camphoric acid be designated as Q. Bredt follows Kipping's pro- 
posal that substituents in the gfem.dimethyl group be designated by 
the letter jr. Thus the four known monobromocamphoric acids are, 



••Noyes, J. Am. Chem. Soc. H, 182 (1912). 
'"Noyes, J. Am. Ohem. Soc. SI. 278 (1909). 
".inn. m, 26 (1913). 



478 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



CH, 



CH, 



-CO,H 



H 
Br' 



>C 



CH3 — C 

i- 

H 



CH, 



-CO,H 



S-Bromocamphoric acid 



CH, 



CH3 

i- 



CH, 



CH, 



-i- 
I 

-c- 

I 

Br 



CH, 



-COj,H 



-CO,H 



4-Bromocamphonc acid 



CH, 



CH, 



CH3 

I 
-C— 



-CO,H 



CH, 



-C- 

i- 

H 



• CH^Br 



-CO,H 



n-Bromocamphoric acid'' 



CH, 



CH,Br. 

I 
-C 



-CO,H 



CH, 



CH3 — C- 

I 

CH, C- 

H 

Q-Bromocamphoric acid''^ 



-CO,H 



From chlorocamphoric phenyl ester by heating with quinoline, 
saponifying the resulting unsaturated ester and heating the free acid, 
Bredt '^ obtained an acid whose structure he represented as follows, 



CH, 



CH3 

I 
C — 



CO^R 



CH, 



CH3 



CO,R 



CH, — C — CH, 



CH, 



I 



CO,R 



\ 



CI 



CH, 



CH, — C — CH, 



CH 



CH- 



•CO,R 



CH, 



■A. 



CO3H 



CH3 — c 



CH3 

CH =:==CH 

camphonenic acid 

"Kipping, J. Chem. Soc. 69, 918 (1896). 

"Armstrong & Lowry, J. Chem. Soc. 81, 1467 (1902). 

^' Ber. S5, 1286 (1902). This acid was originally termed "lauronolic acid" by 
Bredt, but later changed to camphonenic acid to avoid confusion with Flttig and 
Worlnger's lauronolic acid. Cf. W. A. Noyes & Burke, J. Am. Chem. Soc. Si, 177 
(1912). In a later paper by Bredt lAnn. S95. 26 (1913)] d.dehydrocaniplioric acid, 
melting-point 202°-203'', and d.I.dehydrocamphoric acid, melting-point 228°, Is described. 



BICYCLIC NON-BENZENOID HYDROCARBONS 



479 



Bredt arrived at this structure from the fact that the acid gives 
camphoronic acid on oxidation. 

CH3 

-A- 



CH, 



CH, 



CH 



-i 



CO,H 



CH, 



CH3 

I 
-C- 



•CO,H 



■CH, 



H 



CH, — C — CH, 

I 
30,H CO^H 

Camphoronic acid 



Camphononic acid is one of the important members of this series. 
On further oxidation it yields camphoronic acid '^ and its constitution 
is as shown in the following, 

CH3 CH3 

— C CO,H CH, — 



CH, 



CH, 



CH, 



A: 



-c- 



CH3 





CH, 



CO2H 



■C — CH3 
CO,H 



■CO^H 



camphononic acid 

By oxidizing dibromocamphor by dilute nitric acid and silver nitrate 
Lapworth and Chapman" obtained homocamphoronic acid, whose 
anhydride loses CO2 yielding camphononic acid. 

CHg CHo 



CH, 



C- 



CO,H CH, 



CH3 — C — CH3 

CH^ C = 

\ \ 

COOH OH 



CH, 



•C- 

i. 



CO,H 



■CH3 +CO,+H,0 



CH, 



C = 



Lapworth and Lenton'^ also made camphononic acid in two other 
ways which also indicate the constitution shown. The amide of cam- 
phanic acid was converted by dehydration to the nitrile and this, on 
treating with concentrated alkali loses HCN to give camphononic acid. 
Their second method also starts with camphanic acid amide; by treat- 
ing with bromine and caustic soda the CONH2 group is replaced by 

"Lapworth and Chapman, J. Chem. Soc. 75, 986 (1899). 
'V. Chem. Spc. 79; 1384 (1901). 



480 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



NHj and the resulting product decomposes yielding ammonia and 
camphononic acid. 

CHj CHg 

— C CO CH, C — 



CH, 



CO 
\ 



■CO,K 



CH, — C — CH, ^nitrile-» 



CH, 



C- 



/ 



/ 



/ 



/ 



CONH, 



CH, 



-i_ 



CH, 



CH, 



C< 



CH 



camphanic acid amide 
CH3 



OH 

CN 



CO,H 



CH, 



CH, 

L 



CO,H 



CH, 



CH, 



i. 



-CH3 
OH 

NH, 



" A- ■ 



CH, 



CH, 



■CH, 



C==0 



When camphononic acid is reduced electrolytically the ketone 
group is reduced without structural change, to give camphonolic acid 
or its lactone.'" 

CH, CH, 



CH, 



COCH 



-COOH 



CH, 



CH, 






■CH, 



CH, 



CH3 

.i- 



CH, C — 

CH3 C CHg 

^H, CH.OH 

camphonolic acid 
cis. trans. M.-P. 249° 



CH, 



— CO 

I \ 

CH, — C — CH3 

/ 
/ 
CH — 



lactone M.-P. 160° 

"Bredt, J. praht. Ohem. (2) 8^, 786 (1911) ; Ann. S6e. 1 (1909). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



481 



It will have been noted that the above substances retain the carbon 
structure of camphoric acid. Fittig and Woringer " had obtained an 
acid by the decomposition of bromocamphoric anhydride which they 
had termed lauronolic acid but since it did not give the oxidation 
products described above many chemists refused to accept Bredt's pro- 
posed constitution of camphoric acid. Fittig and Woringer's lauro- 
nolic acid does not give camphoronic acid on oxidation. What ap- 
pears to be the correct explanation of the structure of this acid was 
given by Lapworth and Lenton'" and also confirmed by other evi- 
dence. In the preparation of Fittig and Woringer's lauronolic acid 
by the decomposition of camphanic acid, Lapworth and Lenton assume 
a structural rearrangement similar to the change of position of a 
methyl group in the pinacone — pinacoline rearrangement. Accord- 
ingly, Fittig and Woringer's lauronolic acid has the structure shown 
in the following. 



CH 




CH, 



camphanic acid 
CH3 

-A- 




CH 



CH, 



■COjH Laurolenic acid (Bredt). 



CH3 — C- 



■ H 



(lauronolic acid) 



CH, 



■C 
\ 



CH, 



This lactone proves, in fact, to be dijferent from the lactone of 
camphonolic acid later made by Bredt. In the light of the fore- 
going, other facts become clear, for example the oxidation of lauro- 
nolic acid by potassium permanganate *° to laurenone. 



■"Ann. 227, 6 (1885). 

" hoc. cit. 

»»Tiemann & Tigges, Ber. 33, 2950 (1900). 



482 CHEMISTRY OF THE NON-BENZENOID HYDROCARBON& 



CH, 



CH3 

I 
■C — 



CH, 



-i- 



CH,H 



CH, 



CH, 



C- 



c 



CH, 
CH, 



CH 



CH, 



H 



C = 



CO 

I 
= CH 



or 



CH, 



CH, 



CH3 

I 
CH, 



CH3 

■A. 



to- 



CO,H 



CH, 



CO — CH, 



CH3 

I 
- CH — C - CH3 

CO — CH 



CH, 



Also the nitro derivative and its reaction products, obtained by 
Schryver*^ are, according to Bredt, also in harmony with the other 
known facts, the nitro group displacing the tertiary hydrogen, as is 
customary, Schryver's nitro derivative probably having the struc- 
ture, 

CH, 



CH,— 




Oxidation to camphoronic acid is therefore the criterion as to whether 
or not the CCCHj), group of camphoric acid is retained, and as sur- 
mised by Lapworth and Lenton, Fittig and Woringer's lauronolic acid 
and its derived lactone (bihydrolaurolactone) and the hydrocarbon 
laurolene, do not possess this structure. 

A similar rearrangement of a methyl group occurs in the conver- 
sion of campholytic acid to isocampholytic acid.*^ 

"J. Chetn. 80c. 7S. 559 (1898). 

" This name has been agreed to by Noyes, Perkin, Aschan and Bredt to replace 
the various other names by which It has been known, e. g., isolauroXonlc, camphothetlc, 
and jS-campholytlc acid. 



BICYCLIC NON-BENZENOID HYDROCARBONS 
CHo CH, 



483 



CH 



CH, 



■C- 



■CH, 



CH, 



CH3 — - C — CHj, 



m- 



CO,H 



C — CH, 



CH, 



CO,H. 



canipholytic acid. 



isocampholytic acid. 



In connection with the relationships just discussed it will be con- 
venient to mention the work indicating the structure of laurolene and 
isolaurolene C8Hi4. Isolaurolene has been obtained by heating copper 
camphorate and also from isocampholytic acid (P-campholytic acid). 
Its structure has been determined by Blanc ^^ by a study of its oxida- 
tion products and confirmed by it« synthesis, to be 1 . 1 . 2-trimethyl- 
A^-cyclopentene. 

CH3 

I 
C CH 



CH, 



i. 



CH, 



isolaurolene 



CH, CH. 



Noyes and Derick '* prepared laurolene by treating aminolauronic 
hydrochloride with sodium nitrite, also by boiling the nitroso deriva- 
tive of aminolauronic anhydride with caustic soda. They found 
experimental evidence which they considered as supporting the struc- 
ture which Eijkmann *^ had proposed on the ground of refractometric 
considerations. Noyes and Kyriakides *° made the hydrocarbon by 
simple methods of synthesis which confirm the structure proposed by 
Eijkmann, i.e., 



CH, 



CH, 



CH- 



CH, 



CH, 



-in'"'- 



< 



CH, 



CH, 



CH, 



CH, 



-CH 

C — CH3 
Ji CH 



laurolene 



"Bull. sac. chim. (3) 19, 703. 

"J. Am. Chem. Soc. SI, 669 (1909). 

"Chem. Zentr. 1907, II, 1208. 

"J. Am. Chem. Soc. S2. 1064 (1910). 



484 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The physical properties of the laurolenes are as follows: d.laurolene, 

ral26.2° 15° 

"• ^_^=+ 28.15°; d— =0.8030; boiling-point 120.3°-121°. Iso- 

laurolene boils at 108°. 

Derivatives of Camphor. 

Camphor Oxime ^' is readily made in good yields by adding the 
calculated quantity of concentrated caustic soda to an alcoholic solu- 
tion of camphor and hydroxylamine hydrochloride and heating on a 
water bath for about one hour. The oxime crystallizes well from 
dilute alcohol, melting-point 120°. It boils at 249°-250° with very 
slight decomposition. Camphor oxime is reduced by hydrogen and 
catalytic nickel at 180°-200° to bornylamine, dibornylamine and 
camphylamine, the second being the principal product.^* 

C = N.OH 

Isonitrosocamphor, C8Hi^<| exists in two forms, melt- 

CO 
ing at 114° and 153°.*° For its preparation"" 102 grams of camphor 
are dissolved in 500 cc. of dry ether and 15.2 grams of sodium as 
sodium wire, are added. Amyl nitrite is then added in small portions 
with cooling, until 78 grams have been added. After standing about 
three hours, add cracked ice and ice water; the sodium salt of isonitroso 
camphor is in the aqueous phase and unchanged camphor and borneol 
in the ether. Acetic acid precipitates the free isonitroso derivative, 
which after recrystallizing from dilute methyl alcohol, or petroleum 
ether, melts at 152°-154°. 

Zinc and dilute acids readily reduce it to amido camphor 

CH.NH^ 
C8Hii<| boiling-point 244°, whose hydrochloride has a 

CO 
physiological action similar to curare, but feebler. Two molecules of 
amidocamphor may be condensed to dihydrocamphenepyrazine."^ 
Amidocamphor and potassium cyanate yield camphorylcarbamide 

CH.NHCONH^ 
C8Hi4<| which may be converted to camphoryliso- 

CO 
cyanate by the action of nitrous acid. Like the well-known reagent, 

"Auwers, Ber. 22, 60o (1889). 

"Aloy & Brustier, Bull. soc. chim. (4) 9, 733 (1911). 

8" Cliem. Zentr. 1908, I, 1270. 

»»Claisen & Manasse, Ann. Zll,, T6 (1893). 

"Ann. 313, 25 (1900). 



BICYCLIC NON-BENZENOID HYDROCARBONS 485 

phenylisocyanate, the camphoryl derivative is very reactive and a 
large number of camphorylurethanes and other derivatives have been 
prepared from it.'^ When amidocamphor hydrochloride is treated 

with nitrous acid, azocamphor, C8Hi4<| is produced."" 

CO 
CO 
Camphor Quinone, C8Hi^<| . When isonitrosocamphor is heated 

CO 
with dilute sulfuric acid, the diketone is formed, as in the hydrolytic 
decomposition of oximes, 

C = N.OH CO 

{a)C,-H,,<\ + H,0 -^ C3H,, < I +H,N.OH 

CO CO 

C = N.OH CO 

(b) CsH,, < I +NO.OH ^ CsH,, < I +N3O + H3O 

CO CO 

Nitrous acid also converts isonitrosocamphor to camphorquinone.'* 
About 9 parts of camphor are dissolved in 15 parts acetic acid and 
4 parts sodium nitrite (dissolved in minimum of water) are carefully 
added. After completion of the reaction the diketone is precipitated 
by diluting with cold water. The diketone is easily volatile, crystal- 
lizes well in yellow needles melting at 198°, and is markedly soluble 
in hot water. 

The effect of the two contiguous CO groups upon the stability of 
the ring is noteworthy, the diketone being easily converted to cam- 
phoric acid or its derivatives under the influence of a wide variety of 

C = N.OH 
reagents.^' The dioxime, C8Hi4< | is best made by the 

C = N.OH 
action of hydroxylamine on isonitroso-camphor. All of the eight pos- 
sible oximino derivatives of camphorquinone are known. The dis- 
covery of the two modifications of isonitrosoepicamphor, constituting 
the third and fourth monoximes of camphor quinone, completes the 
list of theoretically possible oximes and Forster "" has shown the prob- 
able configuration of these derivatives. Their physical properties are 
as follows, 

"= Chem. Zentr. 1908. I, 257. 
"Angeli, Ber. 26, 1718 (1893). 

"Claisen & Manasse, Ann. Srt),, 83 (1893) ; Lapworth, J. Chem. Soc. 69, 322 (1896) ; 
Bredt, Rochussen & Monheim, Ann. SIJ,, 388 (1900). 
"Aschan, Ber. SO, 657, 659 (1897). 
"J. Chem. Soc. 103, 662 (1913). 



486 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

Melting- in in 

Point Chloroform S% NaOH 

Isonitrosocamphor (unstable) 114° 172.9° 275.3° 

Isonitrosooamphor (stable) 162° 197.0° 288.0° 

Isonitrosoepicamphor (unstable) 137° -179.4° -278.5° 

Isonitrosoepioamphor (stable) 170° -200.1° -422.0° 

Camphorquinone, a-dioxime 201° -51.7° -103.8° 

Camphorquinone, g-dioxime 248° -24.5° 

Camphorquinone, y-dioxime 136° 16.4° 14.3° 

Camphorquinone, 8-dioxime 194° 52.8° 87.0° 

Reduction of the diketone by zinc dust and acetic acid gives a-oxy- 

CH.OH 
camphor C8Hi^< I melting-point 203 °-205°. Sodium and alco- 

CO 

CH.OH 
hoi causes further reduction to camphorglycol, C8Hi4<| , 

CH.OH 

melting at 231°. This glycol may be regarded as bornyleneglycol 
and is not identical with the glycol of camphene. Camphor-quinone 
undergoes condensation with nitromethane very readily and nitrome- 
thylenecamphor and the intermediate product, nitrotnethylhydroxy- 
camphor, have been isolated."' 

CO C(0H).CH2N0, 

CgH,, < I H-CH3 = N0.0Na -> C8H,,< I 

CO CO 

C = CH.N02 

> C^H,, < I 

CO 

Condensation with ethyl cyanoacfetate also readily takes place yield- 

CO^Eth 

C = C< 
ing ethyl camphorylidene-cyanoacetate, C8Hi4<| CN 

CO 

from which the corresponding camphorylidenemalonic acid was ob- 
tained. 

Para-diketocamphane : When a mixture of bornyl and isobornyl 
acetates are oxidized, in glacial acetic acid, by chromic acid, an 
acetoxy camphor is produced,"^ and since pure isobornyl acetate does 
not give this result, this derivative must be a product resulting from 

"Forster & Withers, J. Chem. 8oc. 101, 1328 (1912). 
" SchrBtter, Monatsh. 1881, 224. 



BICYCLIC NON-BENZENOID HYDROCARBONS 487 

the oxidation of bornyl acetate. Hydrolysis of the acetate gives 
hydroxycamphor, melting at 238°-246°, this product really consisting 
of two stereoisomerides. Oxidation of hydroxycamphor by chromic 
acid gives para-diketocamphane, melting-point 206.5°-207° and 

13.5° 

Bredt "' finds that the diketone is optically active, [a] ^-- — -|- 103.42°. 

Since this substance is not identical with camphorquinone and since 
a substance in which both CO groups were attached to the same 
bridge carbon atom would be optically inactive, Bredt concludes 
that the constitution of the two substances are as indicated below. 



= C 





H 

Para-diketocamphane 

The relative ease with which camphor reacts with metallic sodium 
or sodium amide to form a sodium derivative, has been made use of 
extensively for the preparation of other derivatives. Thus, sodium 
camphor in benzene solution reacts with COj to give d.camphocarbonic 

CH.CO^H 
acid, CsH.:ii<\ , melting at 128°. A recent synthesis of cam- 

CO 
phocarbonic acid by Ruzicka "" is worth noting since a well-known 
reaction was successfully applied to this synthesis by the simple 
expedient of employing an autoclave to obtain a temperature of 200°. 
The diethyl ester of homocamphoric acid was condensed by sodium 
ethylate in alcohol at 200°. 

CO^R CO 

CH,CO,R CH.CO,R 

Camphocarbonic acid has been employed for the preparation of pure 
bornylene. The a-hydrogen atom in camphocarbonic esters is readily 
displaced by sodium, by which means alkylation is easily effected; 
alkyl halides give C-derivatives but acid chlorides give o-acylated 

"J. prakt. Chem. (2) 101, 273 (1920). 
'"Helv. Chim. Acta. S, 748 (1920). 



488 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

C.CO,R CH.CN 

products, C8Hi4< 1 1 . The closely related nitrile C8Hi4< | 

C.OAc CO 

also forms a monosodium derivative which, by the action of alkyl 
iodides, yields a mixture of and C alkyl derivatives. 

Camphocarbonic acid and its alkyl derivatives readily decompose 
on heating, a molecule of carbon dioxide and camphor or a derivative 

CHR 
C8Hii<| being formed. The introduction of a methyl group in 

CO 
this case has a very marked effect upon the melting-point, methyl- 

CH.CH3 
camphor C8Hi4<| melting at 38°; ethylcamphor and dime- 

CO 
thylcamphor are liquids, their odor being suggestive of menthone 
rather than camphor. 

C = CH.OH 
Oxymethylenecamphor, C8Hi^<| is of interest on 

C = 
account of its strongly acidic character. It is prepared by the action 
of methyl or ethyl formate on sodium camphor or magnesium-camphor 
bromide, or by the action of sodium methoxide on a-mono-halogen 
or a-dihalogen camphor.^"^ As in similar "formyl" derivatives some 
reactions indicate the structure indicated above and other reactions 

CH.CHO 
point to the desmotropic form, C8Hi4<| . It readily forms 

CO 
an acetate and a series of ethers; it combines with nascent hydro- 
cyanic acid to give a cyanhydrine and is reduced by sodium and 

CH.CH.OH 
alcohol to camphylglycol, C8Hi4<| , which is known in two 

CHOH 
forms, cis melting at 87° and trans melting at 118°. The trans- 
glycol is oxidized by potassium permanganate to ira?is-borneolcarbonic 

CH.CO,H 
acid C8Hi4<| but cis-borneolcarbonic acid is unstable and 

CHOH 
oxidation in this case proceeds to camphoric acid.^"^ 

CH.CH.OH 
Reduction of camphylcarbinol C8Hii<| by sodium 



CH^ 



i»>Bruhl, Ber. S7, 2069 (1904). 
""Bredt, Ann. S66, 62 (1909). 



BICYCLIC NON-BEN ZENOID HYDROCARBONS 489 

in moist benzene or condensation of camphylbromomethane ; by 

CHCHj — CHjCH 

sodium/''^' gives dicamphylethane, C8Hi4<| | >CgHi4, 

melting-point 209°-211°. 

Reduction of camphor by passing over catalytic nickel and 
alumina at 200° gives isocamphane,"* melting-point 64.5°, boil- 
ing-point 164°-165°. Camphor condenses with oxalic ester,^''^ 
under the influence of sodium ethylate, to camphoroxalic acid 

CH.COCO,H 
C8Hi4<| melting-point 88°, which has yielded a series 

CO 

of derivatives. The above reactions will serve to make clear the 
very marked reactivity of the CHj group contiguous to the ketone 
group in camphor. 

Camphoric Acid has been discussed above on account of the im- 
portance of its constitution to that of camphor itself. Its preparation 
is not difficult and the original method of Wreden ^'"' gives quite satis- 
factory yields. To 300 grams of camphor 3 liters of nitric acid, Sp. 
Gr. 1.27, are added and the mixture" warmed on a water bath for 
several days. When cold the crude crystals are taken up in about 
1 liter of water and milk of lime made from 50 grams of lime are 
added, which forms the freely soluble acid salt. The soluble salt is 
separated from unchanged camphor and the camphoric acid is then 
precipitated with more milk of lime as the sparingly soluble neutral 
salt, from which the acid may be liberated by hydrochloric acid; 
yield about 250 grams, melting-point 178°. It is soluble in 160 parts 
of water at 12° but is soluble in 10 to 12 parts of water at 100°. In- 
active (d.l.) or para-camphoric acid melts at 204°. 

On heating calcium camphorate the expected ketone formation 
takes place but the bridged ring is also broken, the constitution of the 
resulting product, camphorphorone, having been shown by a study 
of its oxidation products and its synthesis from 2-methyl cyclopen- 
tanone and acetone (by condensing by sodium ethoxide) and the 
hydrolytic decomposition of camphorone by caustic alkali to this 
ketone and acetone."' The latter reaction will recall the similar 

"^ Eupe & Ackermann, Helv. Chim. Acta. 2, 221 (1919). 

>"*Ipatiev, Ber. J,S, 3205 (1912). 

'"Tingle, J. Am. Chem. Soc. 23, 3G3 (1901) : 29, 2T7 (1907). 

""Ann. 163, 323 (1872). 

"'WaUach, Ann. 331, 322 (1904). 



490 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



behavior of citral, pulegone and other substances which possess the 
group (CH3),C = C< 



CH, 



CH3 

.A- 



■CO, 



CH3 — C — CH3 
CH, CH CO, 



\ 

( 



Ca 



CH, 



H 



CH, 



\ 



CH, 



CH, 



-C 

•II- 
-C 



/ 



CO 



■CH, 



CH, 



CH, 



CH, 



CH3 
\ 



CH, 



/ 



CO 



c 



CH, — C — CH, 



CH, 



H 



C 



\ 
( 



C0+(CH3),C0 



H, 



When camphorphorone is reduced by hydrogen over catalytic 
nickel^"' at 130° the saturated ketone, dihydrocamphorphorone, is 
produced, which on reduction at a higher temperature, 280°, is further 
reduced to l-methyl-3-isopropylcyclopentane (boiling-point 132°- 
134°). 




CH CH, 



Camphorimide, melting-point 243°, is readily made when dry am- 
monia is passed into boiling camphoric acid."" 

Camphor reacts normally with magnesium- ally 1 bromide ^^'' to 
C(0H).CH2CH = CH, 
give allyl borneol, C8Hi4<| , which on oxida- 

CH, 

M'Godchot & Taboury, Bull. soc. chim. (4) 13, 599 (1913). 

I™ Evans, J. Chem. Soc. S7, 2237 (1910). 

"»Kholn, J. Buss. Phya.-Ohem. Soc. U, 1844 (1912). 



BICYCLIC NON-BENZENOID HYDROCARBONS 491 

C(0H).CH2C02H. 
tion by permanganate yields the acid C8Hi4<| 

Haller has shown that by the action of alkyl halides and sodium 
amide, camphor may be alkylated, the substitution in such ketones 
replacing one or more hydrogen atoms adjacent to the carbonyl group. 
Haller ^^^ has thus prepared dimethyl, methylethyl, propyl, dipropyl, 
benzyl, dibenzyl and ethylbenzyl camphors. By reduction of these 
ketones the diethyl, methylethyl, propyl and dibenzylborneols were 
obtained. 

The quantitative determination of camphor in commercial prod- 
ucts such as celluloid or spirits of camphor is somewhat difficult on 
account of its volatile character. It can be precipitated from alco- 
holic solutions by concentrated aqueous calcium chloride,^^^ taken up 
in light petroleum ether and finally determined gravimetrically. In 
the case of celluloid, distillation of the finely rasped product with 
steam gives fairly satisfactory results,^^^ if no camphor substitutes are 
present. Extraction of rasped celluloid for 10 hours with petroleum 
ether also gives good results. The use of an immersion refractometer 
on solutions of camphor in methyl alcohol has also been employed.^^* 

Homocamphor: This ketone closely resembles ordinary camphor 
in its physical properties and chemical reactions. It is a white crys- 
talline substance melting at 189°-190°, sublimes easily and has an 
odor closely resembling ordinary camphor. It has one more CHj 
group, in the ring containing the CO group, than ordinary camphor. 
It has recently been made ^^^ from camphoric acid anhydride by con- 
densing with diethyl sodio-malonate, reducing the product thus ob- 
tained and on distilling the resulting acid hydrocamphorylmalonic 
acid is obtained, 

CO C = C(CO,C..HJ, 

CsHi, < > > CsHi, < > " > 

CO CO 

CO,H 
CH2CH< CH^.CH.COoH 

C^H,, < CO,H > C^H,, < " > 

CO^H CO^H 

hydrocamphorylacetic acid. 

'" Haller & Bauer, Compt. rend. 158, 754 (1914) ; Haller & Louvrier, Compt. rend, 
m, 1643 (1909). 

"=Pennlman & Randall, J. Ind. d Eng. Chem. 6, 926. 

1" Barthelemy, Kunatoffe, S, 46 (1913). 

"*Utz, Cliem. Ais. I, 1467 (1907) ; Arnost, Z. Nahr. Oenuaam. M, 532. 

"» Lapworth & Royle, J. Chem. Soe. m, 744 (1920). 



492 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

CHjCHj 

CO 

Heating the lead salt of the last named acid or prolonged heating with 
acetic anhydride yields homocamphor. 

Synthetic Camphor 

The economic balance between the cost of manufacturing camphor 
synthetically and obtaining it from natural sources is at present com- 
paratively even, and success in the manufacture of synthetic camphor 
is very largely determined by factors over which the manufacturing 
chemist has no control. The development of this industry was coin- 
cident with the very great rise in price of natural camphor after 
Japan had succeeded in practically monopolizing the production of 
natural camphor. The large tree Cinnamomum camphora is the only 
commercial source of natural camphor and the production of camphor, 
by steam distilling the chipped wood of large mature trees of sixty 
years or more in age, has been carried out in China and Japan for 
several hundred years. True camphor was known in Europe at least 
as early as 1583, but owing to the custom of cutting down the trees 
for distillation of the wood, together with the increased demands for 
camphor resulting from the development of the celluloid industry, 
large mature trees became more and more scarce in Japan and North 
Central China,^^^ with the result that in 1903 the industry in Japan 
was made a Government monopoly. Camphor had been produced in 
Formosa, coming into the market prior to 1895 as Chinese camphor, 
but after this island was acquired by Japan, camphor production was 
vigorously pushed by the Japanese and Formosa soon became the 
principal producing locality. With the elucidation of the constitution 
of camphor and related substances, its artificial production was prac- 
tically certain to be undertaken, but this was greatly stimulated by 
the attempted price manipulation of the Japanese monopoly. Cellu- 
loid, the manufacture of which was first developed by John W. Hyatt 
of Newark, N. J., is the chief industrial use of camphor, this industry 
consuming seventy to eighty per cent of the world's total camphor 
production. The recent rapid development of the moving picture 
industry has added to the consumption of camphor for the manu- 
facture of films and a further consumption has been brought about 

'^^ Foochow was formerly the center of the Chinese camphor market. During the 
period of high prices in 1919 about 930,000 Jb. of camphor were shipped from Foochow. 



BICYCLIC NON-BENZENOID HYDROCARBONS 493 

by the manufacture of transparent films and sheets for automobile 
curtains. Camphor was used at one time in the manufacture of 
smokeless powder and it is still so used to a limited extent in some 
sporting powders. The United States imports the largest share of 
the annual production of natural camphor but with the development 
of the celluloid industry by the Japanese, the Japanese Monopoly 
Board has seen fit to allot certain proportions of the output to the 
various consuming countries, a situation which is having the natural 
result of stimulating the production of natural camphor in the United 
States. 

All of the successful processes for the manufacture of artificial 
camphor employ pinene or turpentine as a raw material, and while 
the primeval camphor forests in Formosa and the interior of China 
are being rapidly destroyed, the manufacture of artificial camphor is 
dependent upon a raw material the supply of which is likewise rapidly 
diminishing with the destruction of the American turpentine forests. 
Turpentine is the largest item of cost in the manufacture of artificial 
camphor. However, the use of light petroleum fractions and other 
turpentine substitutes, particularly in the pajnt and varnish industry, 
should enable scientific forestry to keep pace with the consumption of 
turpentine in those industries in which it is indispensable. 

Another factor in the situation is the planting of camphor trees 
and the distillation of camphor from the twigs and leaves. (The cam- 
phor tree does not exude an oleoresin which can be collected and sepa- 
rately distilled, as in the case of turpentine.) The cultivation of 
camphor trees and distillation of the leaves has been carried out ex- 
perimentally in numerous subtropical localities, the Bahamas,^^' 
Florida, Ceylon, Java and Formosa, and according to a recent Bul- 
letin of the Imperial Institute (1920) the Japanese Monopoly Board 
are stated to have planted 3,000,000 trees between the years 1900 and 
1906 and 11,000,000 trees in the three years following. In 1913 the 
Board adopted the plan of planting 3,000 acres annually in camphor 
trees. However, leaf distillation has not proven economical and the 
total production of Formosan camphor has declined steadily since 
1916. In 1919 the Japanese Monopoly Board estimated that the 
production of Formosan camphor from old trees would average about 
6,500,000 lb. annually and that the trees set out previously, as before 
mentioned, would be ready for working about 1930. In the United 

"'Emerson & Weidlein, J. Ind. & Eng. Chem. J,, 33 (1912); Eaton, TJ. 8. Dept 
Agrie. Bull. 15 (1912) ; Beille & Lemaire, Bull, de Pharmacie Bordeauw 191S, 521. 



494 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

States one celluloid company has about 3,000 acres planted in cam- 
phor trees near Satsuma, Florida, and another company is reported to 
have about 12,000 acres planted in camphor near Waller, Florida. 
The United States Department of Agriculture has a station at Orange 
City, California, engaged in the study of camphor cultivation. The 
cultivation of camphor and distillation of the leaves has also been 
studied in the Federated Malay States and at the Hakgala Gardens 
in Ceylon. In the former tests the yield of crude camphor varied 
from 1.1 to 2.6 per cent; a yield of about 180 pounds per acre per 
year was estimated. Old wood of mature trees yields on an average 
about 4 per cent of crude camphor oil, and air dry leaves of cultivated 
trees average 1.5 to 2 per cent of camphor oil (75 per cent of which 
is camphor). R. T. Baker ^^* has reported a high yield of camphor 
from the Australian species Cinnamomum olivieri and C. laubatii. 

Formerly, crystalline bornyl chloride (usually miscalled pinene 
hydrochloride) was manufactured and sold under the name of "arti- 
ficial camphor." This product has been known for more than a cen- 
tury but its usefulness in the manufacture of true camphor was not 
appreciated until the development, since 1906, of the processes now 
employed in the making of synthetic camphor. Bornyl chloride can- 
not be substituted for camphor in the manufacture of celluloid and 
it contains unstable hydrochlorides, which liberate free hydrochloric 
acid. It is no longer a common commercial article. 

All known processes for the industrial manufacture of synthetic 
camphor involve the oxidation of borneol or isoborneol. Borneol 
occurs in nature as "Borneo camphor" in the wood of one of the 
Dipterocarpaceoe and in a large number of essential oils, including 
most of the pine needle and cedar leaf oils, ginger oil, et cetera, but 
from none of these natural sources can it be produced cheaply or in 
quantity. The borneols are obtained industrially from bornyl chlo- 
ride, and this explains the use of pinene or turpentine as a raw 
material. No other material is known from which the borneols oi 
camphor can be manufactured cheaply and in quantity. 

Turpentines suitable for the production of bornyl chloride and 
synthetic camphor are derived mostly from the long leaf pine, Pinus 
-palustris, of the southern United States, the Cuban pine, Piniis hetero- 
phylla, and the Pinus pinaster of France. The turpentines from thesf 
species consist almost exclusively of a and p-pinenes. Small propor- 
tions of limonene and phellandrene might occasionally be found in 

'"Schlmmel & Co. Semi-Ann. Rep. 1911 (1), 38. 



BICYCLIC NON-BENZENOID HYDROCARBONS 495 

American turpentine since, as Herty and Dickson ^^° have shown 
Pinus serotina yields a so-called turpentine consisting chiefly of limo- 
nene, but these trees are scattered and relatively unimportant. Syl- 
vestrene, one of the principal constituents of Russian and Finnish 
turpentine, has never been found in the oil from American species. 
The various "process turpentines," made by solvent extraction of pine 
wood or from stumps, is not suitable for the manufacture of bomyl 
chloride since such turpentines commonly contain liberal proportions 
of the solvent employed for its extraction, and other constituents which 
have been noted in such oils are limonene or dipentene, cineol, terpi- 
neols, terpinene and fenchyl alcohol. Turpentine is considerably 
modified by air oxidation, forming alcohols, terpineols, sobrerol, 
formic and acetic acids and resinous substances, and since moisture 
must be rigidly excluded from the preparation of bomyl chloride, the 
presence of very small traces of alcoholic or other oxidation products, 
which can form water by the interaction of hydrogen chloride, very 
materially decreases the yield of bornyl chloride and the use of old 
turpentine which has been exposed to air oxidation should accordingly 
be avoided. 

Testing of Turpentine: 

(a) Specific Gravity: This should be within the limits 0.862 to 
0.870 at 20°C. Lower specific gravity would indicate the presence 

■ of petroleum naphtha. A higher specific gravity would indicate the 
presence of wood turpentine, "pine oil" (terpineols), or that the tur- 
pentine has become oxidized by long storage. 

(b) Boiling-point: Nothing should distill below 154°C. (except a 
drop or two of water), and 75% should distill below 160°. Some 
specifications require that 95% should distill below 170°. Petroleum 
naphthas are sometimes very closely cut so as to boil within this range 
(154° to 170°), but ordinarily will show some distillate below 154°. 
Limonene and dipentene boil at 176° and any considerable amount 
will be thus indicated. The terpineols boil at 210°-218°. Rosin 
spirit has a wide range of boiling-point, like petroleum naphtha, and 
also contains considerable dipentene. 

(c) Optical Rotation: It is not known whether pinenes of low 
optical rotation give better yields of bomyl chloride, as is the case 
with crystalline nitrosyl chlorides, or not. 

"•J. Am. Ohem. Boo. SO. 872 (1908). 



496 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

(d) Refractive Index: At 20°C. this should be within the limits 
1.4680 to 1.4760. Low values would indicate petroleum naphtha. 

(e) Bromine and Iodine Numbers: These are chiefly useful in 
detecting petroleum naphtha but are hardly necessary when the other 
tests are made. It is difiicult to carry out these determinations and 
get accurate, concordant results as with fatty oils, owing to substitu- 
tion reactions taking place with formation of halogen acid. 



Effect of Other Constituents on Bornyl Chloride Preparation: 

(1) p-pinene yields the same hydrochloride as a-pinene: 

(2) Camphene, a minor constituent of turpentine oil, yields a low 
melting, unstable hydrochloride which probably yields camphene 
readily in the autoclave process. Its presence is not objectionable 
but is partly responsible for the partial decomposition of the crude 
bornyl chloride, free HCl being given off. 

(3) Water: The presence of moisture in the reaction mixture 
causes the pinene to be converted chiefly into dipentene dihydro- 
chloride. 




CH, 



i-ZHCl ' 
> 



H, 




Ci 







CH3 ^CH3 



which melts, when pure, at 50°, but the impure mixture remains oily 
and retains considerable bornyl chloride in solution. Dipentene dihy- 
drochloride is much less stable than bornyl chloride and when such 
an oily mixture is heated, it is readily decomposed to free HCl and 
dipentene. 

(4) Limonene, the optically active form of dipentene, forms the 
dihydrochloride and diminishes the yield of bornyl chloride in the 
manner indicated above. 

(5) Terpineols and other Alcohols yield water when treated with 
HCl; cf. item (3). 



BICYCLtC NON-BENZENOID HYDROCARBONS 497 

(6) Organic acids also cause the reaction with hydrogen chloride 
to go too far, with rupture of the Co ring to form dipentene dihydro- 
chloride. 

Distillation and Drying of the Turpentine: The secret of obtain- 
ing good yields of bornyl chloride is effective drying and purification 
of the turpentine. Mere drying is not sufficient as it is necessary to 
remove or destroy alcohols or other substances which yield water when 
treated with HCl, and metallic sodium is therefore best for this dual 
purpose. The still, which may be ol iron or copper, should be pro- 
vided with a stirrer so that after the sodium is melted it will be thor- 
oughly emulsified in the oil. A small fractionating column is advis- 
able, in which case 90 per cent of American turpentine can be used for 
the preparation of bornyl chloride. 

Turpentine and Hydrogen Chloride: When the pinene has been 
well dried and purified from oxidation products and the hydrogen 
chloride is carefully dried, preferably by sulfuric acid Sp. Gr. 1.84, 
a yield of bornyl chloride corresponding to about 75 per cent of the 
theory can be obtained. Lead-lined or glass-enameled mixing vessels 
should be employed; iron, or alloys or other material which can yield 
iron chloride give liquid chlorides. Reaction temperatures above 30° 
yield increasing proportions of liquid chlorides but the reaction with 
hydrogen chloride is slow below — 15°. Dry neutral solvents such as 
petroleum ether or carbon tetrachloride can be employed without 
diminishing the yield of bornyl chloride and the solidification of the 
reaction mixture can thus be prevented, but alcohol, ether or glacial 
acetic acid cause liquid chlorides to be formed. 

Bornyl chloride is remarkably stable for a chlorine derivative of 
the non-benzenoid hydrocarbon series. The statements in the earlier 
literature that it is decomposed slowly at room temperature and fairly 
rapidly at 100° probably refers to the decomposition of the crude 
product containing unstable impurities such as dipentene dihydro- 
chloride and camphene hydrochloride. Wallach "° states that bornyl 
chloride distills practically without decomposition at 207°-208°, a 
fact which is familiar to those experienced in this field. Bornyl chlo- 
ride, once formed, is not changed by further treatment with hydrogen 
chloride, either dry or in the presence of moisture. True pinene hy- 
drochloride is readily converted to dipentene dihydrochloride by HCl. 
Pinene hydrochloride has never been isolated from the products of 

'"Ann. 239, 4 (1887). 



498 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



the reaction of pinene and hydrogen chloride but was made by Wal- 
lach ^^^ from nopinone by means of magnesium-methyl iodide. 




tCH3M^I 




-t-PCi, 




nopmone 



pinene hydrochloride 



The mixture of oily chlorides accompanying the crude bornyl chlo- 
ride contains nearly 50 per cent of bornyl chloride in solution; thus, 
equal quantities of bornyl chloride melting at 131° and dipentene 
dihydrochloride melting at 50°, melt down to an oil at room tempera- 
ture 20° to 22°, and fenchyl chloride, which is an oil, has a similar 
solvent effect. When the oily chloride mixture is heated to about 
180°, the unstable chlorides are decomposed and a fairly brisk libera- 
tion of hydrogen chloride results. The resulting terpenes, chiefly 
dipentene, may then be distilled and the subsequent fractions boiling 
from 185°-215° yield an additional quantity of crystalline bornyl 
chloride. About 10 per cent of the original oily chloride mixture 
remains behind as a heavy viscous mixture of polymers. The amount 
of crystalline bornyl chloride which is recoverable in this way is 
equivalent to about 35 to 38 per cent of the original oily chlorides, 
when these chlorides are separated originally at — 15°. 

The formation of bornyl chloride from pinene and hydrogen chlo- 
ride is exothermic.^^^ 

On account of the extraordinary stability of bornyl chloride many 
attempts have been made to employ catalysts to facilitate either the 
formation of camphene or conversion to bornyl esters. Anhydrous 
aluminum chloride reacts energetically with bornyl chloride, evolving 
hydrogen chloride and causing further decomposition and polymeriza- 
tion. Anhydrous ferric chloride is markedly less active and fused 
zinc chloride is still less active. Stannic chloride and titanium chlo- 
ride are much like zinc chloride in their effect on bornyl chloride. 
Cuprous chloride, or finely divided copper, is claimed to have a cata- 

'"Ann. SS6, 111 (1907). 

"=Guiselin, Chem. Ztg. Si, 1299 (1910). Large scale work showed 119 000 cnlnrlon 
are liberated on treating 100 kilos of turpentine. ouowea xia.uuu calories 



BICYCLIC NON-BENZENOID HYDROCARBONS 499 

lytic effect upon a wide variety of reactions of both alkyl and aryl 
chlorides, as in the manufacture of glycol,^^" or the conversion of 
chlorobenzene to phenol,^^* but appears to be of no value in reactions 
of bornyl chloride. Barium chloride markedly catalyzes the decom- 
position of simple alkyl chlorides to olefines ^^^ and calcium chloride 
causes rapid condensation of benzyl chloride. But zinc chloride ap- 
pears to be the only catalyst appearing in the patent literature of the 
bornyl chloride reactions.^^^ The purpose of this catalyst is to avoid 
the higher temperatures and pressures usually necessary for the com- 
plete conversion of bornyl chloride to camphene and bornyl acetate, 
when acetic acid and sodium acetate are used. However, considerable 
polymerization invariably takes place and one patentee ^^' seeks to 
avoid this by introducing sodium acetate at intervals which has the 
effect of converting the zinc chloride into zinc acetate and sodium 
chloride, the latter separating on account of its slight solubility in 
acetic acid. Another patentee refluxes a solution of bornyl chloride 
in formic or acetic acids and adds zinc formate or acetate.^^* These 
reactions are quite analogous to the conversion of chloropentanes to 
amyl acetates by heating with sodium acetate in acetic acid solutions. 
In both cases zinc salts cause the formation of 10 to 25 per cent of 
heavy viscous polymerized hydrocarbons. 

Conversion of Bornyl Chloride to Camphene and Bornyl Acetate. 

In the following discussion no attempt is made to distinguish be- 
tween camphene and bornylene. 

The difficulty with most of the processes for making camphene 
from bornyl chloride by heating with alkalies, is chiefly a mechanical 
one, i. e., the insolubility of bornyl chloride in alkalies and inorganic 
alkaline mixtures. Naturally vigorous agitation affords better con- 
tact of the reacting substances and the presence of a fine solid sus- 
pension, milk of lime, assists in the emulsification.^^^ The addition 
of fatty acid soaps has been proposed ^^° and molten alkali pheno- 
lates "^ also have been suggested. Complete miscibility is obtained 

■2« Matter, U. S. Pat. 1,237,076. 

1" Meyer & Bergius, U. S. Pat. 1,062,331; Ber. J,1, 3155 (1914). 
""Braun & Deutsch, Ber. 1,5, 1271 (1912). 

"» Bergs, XJ. S. Pat. 903,047 ; Weizman, D. S. Pat. 910,978 : von Heyden, U. S. 
Pat. 919,762. 

"' Ruder, TJ. S. Pat. 1,105,378. 

"'PhUipp, U. S. Pat. 919,762. 

"• Schmltz & Stalman, U. S. Pat. 1,030,334. 

"oStephan, U. S. Pat. 725,890. 

"'Koch, U. S. Pat. 970,829; Bergs, U. S. Pat. 833,666. 



500 CHEMISTRY OP THE NON-BENZENOID HYDROCARBONS 

when bornyl chloride is heated with organic bases such as aniline "^ 
naphthylamine/^^ pyridine/'* or alcoholic ammonia/^'' The aniline 
process gives very good yields, about 90 per cent of the theory but an 
excess of aniline is necessary, as otherwise, bornyl aniline hydrochlo- 
ride is formed and this substance is not easily decomposed. 

When bornyl chloride is heated with sodium acetate in acetic acid 
in an autoclave to 180° to 200° the bornyl chloride is almost quan- 
titatively converted into camphene ^'"^ and bornyl acetate. The cam- 
phene and acetic acid may be distilled together from the resulting 
reaction mixture and converted to bornyl acetate by the addition of a 
small quantity of sulfuric acid according to the well-known method of 
Bertram and Wahlbaum. (In order to separate the bornyl acetate 
thus formed from the excess acetic acid without diluting with water, 
a slight excess of sodium acetate may be added to form sodium sulfate 
and acetic acid, followed by fractional distillation in vacuo.) 

Bertram and Wahlbaum^'*' originally recommended acetylating 
camphene at 50°, using a mixture such as the following: 2000 cc. 
acetic acid, 1000 cc. camphene, 60 cc. water and 50 g. sulfuric acid. 
Verley ^^^ recommends much more water, as indicated by the follow- 
ing: 450 parts sulfuric acid diluted to 60 to 66 per cent, 100 parts 
camphene, 100 parts acetic acid, the mixture being vigorously agitated 
at 30°. Still better results, according to the writer's experience, are 
obtained by the method of Behal,^^^ according to which the Bertram- 
Wahlbaum mixture is allowed to stand at room temperature for 24 
hours. The formation of polymers is much reduced by operating at 
the lower temperatures. With pure camphene the yield of bornyl 
acetate is 92 to 94 per cent of the theory. When the resulting bornyl 
acetate is fractioned in vacuo, unchanged hydrocarbons pass over with 
the acetic acid fractions. Several other modifications of the Bertram- 
Wahlbaum reaction are obviously mere patent word play. 

It is possible that sodium formate and formic acid can be sub- 
stituted for acetic acid and acetate; in fact, such a process is described 
by Dubosc."" Henry has shown that sodium formate in methyl 
alcohol, and an alkyl halide, gives excellent yields of the corresponding 

"= German Pat. 205,850 (1907) ; Bi-Uhl, Ber. 2S, 146 (1892) ; mimann & Schmid, 
Ber. J,}, 3202 (1910). 

""German Pat. 206,386 (1907). 

■" Weizmann, U. S. Pat. 896,962. 

"'German Pat. 204,246 (1912). 

"«Wallacb, Ann. iJZ, 6. 

'"J. prakt. Chem. (2) 1,9, 1 (1894) ; German Pat. 67,255. 

"»D. S. Pat. 907,428 (1908). 

"•Austrian Pat. 38,203 (1908). 

""Brit. Pat. 14,379 (1907). 



BICYCLIC NON-BENZENOID HYDROCARBONS 501 

alcohol/*^ and ethylene chloride can be smoothly converted to the 
glycol by this reaction.^*^ Bornyl chloride is so remarkably stable, 
however, that, when using methanol, the reaction is slow at 180° and 
330 lbs. pressure. Heating bornyl chloride with alkali oxalates has 
also been tried."^ 

Other Processes for Manufacturing Bonxeol or Bornyl Esters. 

The first attempt to manufacture artificial camphor on an indus- 
trial scale was in 1900 at Niagara Falls, where the Thurlow process ^** 
was operated by the Ampere Electrochemical Co. At that time, tur- 
pentine could be had for about 35 cents per gallon but the yields of 
borneol were so low that the cost of artificial camphor by this method 
was considerably greater than the market price of natural camphor 
and the process was accordingly soon abandoned. In the Thurlow 
process anhydrous oxalic acid was added to dry turpentine at 120°- 
130°. The reaction is energetic and much material was lost by the 
reaction becoming too violent. Dipentene was separated from borneol 
esters by distilling with steam, the esters saponified and the borneol 
oxidized to camphor by chromic acid mixture. It was found most 
expedient to purify the borneol before oxidation rather than to purify 
the camphor made from impure borneol. 

The Thurlow process had quite a few European modifications. 
Zeitschel ^*^ heated pinene and glacial acetic acid to 200° for five 
hours and reported a yield of 10 to 15 per cent camphene, about 40 
per cent bornyl acetate and the remainder was dipentene. According 
to the writer's experience the yields of camphene and bornyl acetate 
are not improved by the addition of acetic anhydride. Tenchyl alco- 
hol is also formed and Bouchardat and Lafont observed ^^^ the forma- 
tion of fenchyl alcohol when using benzoic acid under similar condi- 
tions. Bischler and Baselli ^" treated camphene with anhydrous 
oxalic acid at 110°-115°; Seifert"* used salicyclic acid and pinene at 
110° for 50 hours; Austerweil ^^^ used "poly-substituted acids"; Hert- 
]joj.q15o heated turpentine with boric acid and absolute alcohol, etc. 

^'^ Bull. acad. roy. Belg. lOOZ, 445. 

'« Brooks and Humphrey, U. S. Pat. 1,215,903 ; J. Ind. d Eng. Chem. 9, 750 
(1917). 

""Charles, Eng. Pat. 5.549 (1904). 
'" U. S. Pat. 698,761 ; 833,095. 
"'U. S. Pat. 907,941. 
"• Compt. rend. 113, 551. 
"' U. S. Pat. 876,310. 
"» U. S. Pat. 779,377. 
»»U. S. Pat. 986,038. 
""U. S. Pat 901,293. 



502 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

It is claimed 1^* that by the action of tetrachlorophthalic acid on 
turpentine at 106°-108° (12 hours) and finally at 140° (six hours) 
that esters of borneol are formed and that the borneol thus obtained, 
after saponification of the ester, is quite free from isoborneol. This 
method should therefore be operated to advantage in conjunction with 
the method of catalytically oxidizing the borneol to camphor by pass- 
ing over heated copper, since isoborneol is chiefly decomposed to 
camphene by this treatment. 

Hesse ^^^ has described the reaction of bornyl chloride, with mag- 
nesium in ether, as in the well-known Grignard reaction, and oxidizing 
the magnesium-bornyl chloride by air or oxygen to obtain borneol. 
This reaction, although patented, is of little interest since, like all the 
more complex alkyl halides, the reaction with magnesium is very slow 
and the main reaction is one of condensation, 

(a) C,„H,,C1 + Mg > C,oH„MgCl 

(b) C,„H,,MgCl + CioH,,Cl > MgCl, + C,„H3, 

Regardless of its high cost, this method is not even a good laboratory 
method. 

By reacting upon bornyl chloride with milk of lime vigorously 
stirred, at a comparatively low temperature, 135° to 150° for about 
three days, an alcohol isomeric with borneol is obtained.^^^ This alco- 
hol, camphene hydrate, is much less stable than borneol, melts at 
149°-150°, boils at 206° and on heating with dilute acids is readily 
converted to camphene. This instability would indicate the struc- 
ture of a tertiary alcohol but its constitution is not yet definitely 
known. 

The treatment of pinene with ozone has also been described in a 
patented process ^^* but hydrolysis of pinene ozonide does not really 
give borneol or camphor but pinonic acids (q.v.) and a series of other 
products. Bornylene ozonide might be expected to give camphor on 
hydrolysis. The oxidation of borneols to camphor by ozone has also 
been patented ^^^ but the industrial value of all oxidation methods 
depending upon ozone is questionable. 

"' Brit. Pat. 144,604, to Fabriques de produits cbimiques de Than et de MulhouBe. 

"■' V. S. Pat. 826,105 ; 826,166. 

iM Scherlng, German Pat. 219,243 (1908); Ber. 1,1, 1092 (1908). 

■"Knox, U. S. Pat. 1,086,372 (1914). 

"'Stephan & Hunsalz, U. S. Pat 801,488 (1905). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



503 



Bomeol and Isobomeol 

The relation of camphor to bomeol is shown by the formation of 
borneol from camphor by reduction by sodium and alcohol. 

CHa CH3 

A- 



c = o 





OH 



In addition to borneol, the closely related isoborneol is also formed 
in this reaction. The two borneols are commonly believed to be 
stereoisomers, i. e., 

CH, CH3 

H I OH 

OH 





Both yield camphor on oxidation and their behaviors on oxidation are 
nearly identical and for the purpose of manufacturing synthetic cam- 
phor need not be separately considered. Isobomeol is the principal 
product of the hydration of camphene in the Bertram-Walbaum reac- 
tion. Isobomeol is somewhat less stable than borneol and yields a 
"camphene," melting-point 50°, when decomposed by the action of 
zinc chloride or dilute sulfuric acid. 

Isobomeol Borneol 

Crystal form hexagonal hexagonal 

Melting-point 212° 203°-204° 

Solubility in benzene at 0° 1 :2% 1 :6% 

Solubility in ligroin at 20° 1 :2y2 1:6 

Phenylurethane, M.-P 138°-139° 138°-139° 

Chloral compound, M.-P liquid 55°- 56° 

Bromal compound, M.-P 72° 98°- 99° 

Zinc chloride, conversion to f camphene unchanged 

Dil. sulfuric acid, conversion to \ M.-P. 50° unchanged 

Sulfuric acid -f- CH3OH CH3 ether unchanged 

Oxidation by CrOa camphor camphor 

Oxime of camphor produced, M.-P 118° 118° 

Para-nitrobenzoate ™ 129° 137° 

"'Henderson & Hellbron, Proc. Chem. Sod. 29, 381 (1913). The nitrobenzoate is 
conveniently prepared by treating with p-uitrobenzoyl chloride in pyridine. 



504 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



When borneol or isoborneol is decomposed with loss of water, two 
hydrocarbons are produced, camphene being the principal product. 
The hydrocarbon formed in smaller proportions is bornylene and this 
hydrocarbon retains the structure of the parent alcohols. 




OH 



CH 




A great deal of work has been done upon the structure of camphene 
and bornylene, which is reviewed elsewhere (q.v.) but in the earlier 
literature no distinction is made between these two hydrocarbons. 
Tschugaeff's method of preparing olefines by decomposing the methyl 
xanthate esters gives a fairly pure bornylene when applied to the 
decomposition of borneol.^^' Tschugaeff's bornylene melted at 109° 
to 109.5° and boiled at 146.5°. Dexfro-bornylmethyl xanthate yields 
ZcBiio-bornylene and vice versa, an interesting example of the Walden 
inversion. Bornylene is noteworthy for its high melting-point, as 
compared with all other hydrocarbons, i. e., 113°, and its boiling-point 
146°. Bornylene is less readily acetylated than camphene, by the 
Bertram- Walbaum method. A less pure bornylene may be made by 
treating bornyl iodide with alcoholic caustic potash. Bornylene is 
also more resistant to oxidation than camphene and Henderson and 
Caw ^^^ accordingly purified bornylene by oxidation by hydrogen 
peroxide and obtained a specimen showing the melting-point 113° and 
boiled at 146°. A very pure bornylene made through camphocarbonic 
acid '■='' also showed a melting-point of 113°, and a boiling-point of 
146°. 

CH.CO^H CH.CO^H. C.CO^H CH 

C,H,,< I ^ CsH,,< I ^ C3H,,< II ^ CsH,,< II 

C = CHOH CH CH 



It is still generally believed that "camphene" may be a mixture of 
hydrocarbons, or that camphenes of different origin are not identical. 
The camphenes from various natural sources differ widely in physical 

""Ann. 388, 260 (1912). 

'"J. Chem. 8oe. Ml, 1416 (1912). 

««Bredt, Ann. S66, 11 (1909) ; J. prakt. Chem. (2) 8^, 778 (1911). 



BICYCLIC NON-MNZENOID HYDROCARBONS 505 

properties. Wallach ^'"' isolated a specimen of camphene from a 

Siberian pine-needle oil which showed a low melting-point, 39°, a boil- 

40° 
mg-pomt of 160°-161°, d^^^ 0.8555, [a] —84.9° and n_1.46207. 

Camphene made from bornylamine ^" melts at 50° and showed the 
high rotation of [o.]t^ 103.89° Ordinary camphene hydrochloride, 

melting at 155°, is identical with the chloride of isoborneol. 

Oxidation of Bomeol and Isoborneol 

As stated above, the old Thurlow process, practiced at Niagara 
Falls about 1900, employed chromic acid for oxidation of the borneols 
to camphor. Various special modifications of the chromic acid oxida- 
tion method have been described in the patent literature, and the 
processes of Verley,^^^ Florizoone,^^^ Ruder "^ and Weizmann ^"^ men- 
tion the use of a solvent added to insure thorough exposure of the 
bomeol to the oxidizing solution. Carbon tetrachloride, benzene and 
acetone ^^^ are useful for this purpose, but acetic acid forms appre- 
ciable proportions of bornyl acetate which resist oxidation to cam- 
phor. Verley recommends 50 parts of sodium dichromate, 68 parts 
of sulfuric acid and 600 parts of water but Ruder employs solutions 
of about one third this concentration. Free sulfuric acid should be 
avoided as much as possible on account of the decomposition of iso- 
borneol to camphene, which is more resistant to oxidation, by heating 
with dilute sulfuric acid, as noted above. Gradually acidifying the 
reaction mixture as the oxidation proceeds is therefore advantageous. 
The oxidation of camphene itself by chromic acid has been de- 
scribed ^"^ but the yields are lower than when borneols are employed. 
Another patentee ^" proposed to employ potassium persulfate for the 
oxidation of camphene. The use of sodium dichromate or chromic 
acid for this purpose, on a tonnage scale, involves the electrolytic 
regeneration ^"^ of this oxidizing material or its utilization as basic 
chromium salt solutions in tanning or the mordanting of textile 
goods, otherwise the method would be too costly. 

""Ann. 357, 79 (1907). 
"'Wallach, Ann. 357, 84 (1907). 
"»U. S. Pat. 908,171 (1908). 
>"Brit. Pat. 5,513 (1908). 
"*U. S. Pat. 1,066,758 (1913). 
""Brit. Pat. 21,946 (1907). 

'"Dubosc, Brit. Pat. 8260-A (1906) ; 8356-A (1906). 
"' Sauvage, Freneh Pat. 389,092. 

"" Ges. Chem. Ind. Basel, — French Pat. 387,539 ; LoBlanc, Z. Elektrochem. 7, 290 
(1900) ; McKee & Leo, J. Ind. d Eng. Chem. 12. 16 (1920). 



506 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

The yields of camphor by oxidizing the borneols by air, in the 
absence of catalysts, are very poor,^"" but catalytic dehydrogenation 
of borneol to camphor, by means of finely divided copper ^'"' at 175°- 
180° or reduced nickel "^ at 200°-240° is said to have been practiced 
industrially. Aloy and Brustier ^'^ state that when borneol is passed 
over copper at 300° the yield of camphor is quantitative but that 
above 320° the yield of camphor is progressively diminished until at 
420° hydrocarbons only are produced. Camphor is not reduced to 
borneol by hydrogen and catalytic nickel at 180°-200°, either alone 
or in solution in cyclohexanol. Neave ^" states that borneol yields 
camphor in nearly quantitative yields by passing over finely divided 
copper at 300° but that isoborneol under the same conditions gives 
chiefly camphene. Thorium oxide at 350° yields a terpene mixture 
boiling at 150° to 180°, the constituents of which were not definitely 
characterized.^'^ Small proportions of unchanged bornyl chloride or 
other chlorides poison the catalyst unless the material is previously 
purified to remove such chlorides, as, for example, by digesting with 
a little inert solvent over metallic sodium. 

Quite a number of processes for the oxidation of the borneols by 
nitric acid or oxides of nitrogen have been described. Hesse "^ used 
pure concentrated nitric acid ; another process ^'"^ prescribes nitric acid 
containing oxides of nitrogen, at 10° to 15°, and nitrous acid itself is 
said to give excellent yields.^'' The addition of small amounts of 
vanadium pentoxide to the nitric acid is claimed to be advantageous 
and several patents have recently been granted to Andreau,^'* who 
employs a mixture of about 339 parts of sulfuric acid 66° Be, and 
253 parts of nitric acid, 26° Be, and who notes that once the oxidation 
has been initiated by raising the temperature to about 40°, the reac- 
tion may then be carried out smoothly with cooling so that the tem- 
perature does not rise above 40°. In the nitric acid process the cam- 
phor forms a liquid double compound with the nitric acid, which 
floats on the acid mixture as a sparingly soluble oil layer. This 
obviates the use of a solvent to insure complete oxidation of the 

>»»Cf. Stephan & Eehlander, U. S. Pat. 801,485. 

'T» Sobering, German Pat. 161, . 523 ; Goldsmith, Brit. Pat. 17,573 (1906). 

"'Aschan & Kempe, U. S. Pat. 994,437 (1911); Zimmerman, Brit. Pat. 26,708 
(1904). 

'"Bull. soc. chlm. (4) 9, 733 (1911). 

'"J^. Vhcm. Soc. 101, 513 (1912). 

'"Aloy & Brustier, J. pluirm. clilm. (7) 10, 49 (1914). 

'" Ber. 39, 1144 (19()iji. 

"»Ges. Chem. Ind. Basel, Brit. Pat. 9,857 (1907); Philip, Austrian Pat. 33,720 
(1908). 

■"Boehringer & Son, U. S, Pat. 802,793 (1904). 

"'U. S. Pat. 1,347,071 (1920). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



507 



borneol, enclosure of borneol particles by solid camphor being avoided. 
The oily nitric acid compound is decomposed by water, precipitating 
the camphor. Camphoric acid and nitrocompounds are also formed, 
the latter coloring the crude camphor light yellow, and imparting to 
it a peculiar "nitro" odor. 

Practically every known method of oxidizing organic compounds 
has been proposed for the oxidation of the borneols, or camphene, to 
camphor, including chlorine,^^" hypochlorites,^*" potassium perman- 
ganate both in acid ^^^ and alkaline ^^^ solution, etc. When perman- 
ganate is employed the camphor formed is removed from the spent 
mixtures by distilling with steam. Camphene, in dilute acetone, has 
also been oxidized by potassium permanganate, to camphor.^*' All of 
these methods using permanganate are relatively very costly, except 
where methods for its regeneration have been perfected. 

Impurities of Crude Sjmthetic Camphor 

If the borneol or isoborneol is not purified before oxidation, the 
resulting camphor will contain small proportions of the fenchones, 
which, like camphor, are quite resistant to further oxidation and form 
very stable double compounds with nitric acid. 

The behavior of the fenchenes in the Bertram-Walbaum reaction 
follows the general esterification behavior of unsaturated terpenes. 
Komppa and Hinticka ^^* share Quist 's view that isofenchene, boiling- 
point 152°-155° has the constitution. 

CH3 
CH — CH— C< 

CH, 

CH, 



CH — C- 



CH, 



CH, 



As noted above the chief impurity in bornyl chloride is dipentene 
dihydrochloride but fenchyl chloride is present in the oily part of the 

"» Boehringer & Son, U. S. Pat. 802,792; Brit. Pat. 28,035 (1904). 

"» Hertkorn, U. S. Pat. 901,708 (proposes the addition of salts such as CuCla and 
FeCla) : Glaser, U. S. Pat. 875,062; 864,162 (1907). 

"' Semmler, Ber. 3S, 3430 (1900). 

"'Schering, German Pat. 157,590 (1903) ; Stephan and Hunsalz, U. S. Pat. 770,940 
(1904). 

"sBehal, Austrian Pat. 38,203 (1908). 

'"Ohem. Ais. IS, 2864 (1919). 



508 CHEMISTRY OP THE NON-BENZENOID HYDROCARBONS 

hydrochloride mixture since fenchene has been found in the crude 
camphene made from these chlorides. Aschan ^^^ represents the for- 
mation of bornyl chloride and fenchyl chloride as follows, 




chloride ot fenchyl alcohol 

Crude camphene also contains a very small amount of p-pinolene 
or tricyclene. It will be noted that the fenchyl chloride or the cor- 
responding alcohol whose structure is shown above cannot lose HCl 
or water to form a double bond with either of the adjacent carbon 
atoms. But Quist made tricyclene by decomposing the methyl xan- 
thate ester of fenchyl alcohol and therefore shares Aschan's views as 
to the nature of tricyclene and its method of formation, 




Tricyclene is stable toward alkaline permanganate but, as with 
most cyclopropane structures, acids rupture the 3 carbon ring and 
the Bertram-Walbaum reaction accordingly gives the acetate of iso- 
fenchyl alcohol. Hydrogen chloride at — 10° yields a hydrochloride 



^"Ann. 387, 24 (1912). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



509 



melting at 27.5° to 29°, which on decomposition forms a fenchene 
boiling at 154°. Tricyclene itself, as purified by Aschan by oxidizing 
the accompanying fenchenes by permanganate, boils at 141.5°-143.5.° 
Fenchenes or tricyclene contained in the crude camphene, employed 
for the manufacture of artificial camphor, will accordingly be con- 
verted to fenchyl and isofenchyl alcohols which will in turn be oxi- 
dized to the corresponding ketones. The relations of these substances 
are probably as follows. 




fenchyl alcohol 




CH3 
p-pinolene 
(tricyclene) 



aofenchyl 
alcohol 




fenchone 



isotenchone 



As regards the purification of synthetic camphor for industrial 
purposes, it should be noted that manufacturers of celluloid usually 
specify that the chlorine^*" content shall not exceed 0.1% and borneol 
should not be present in excess of 0.5 per cent. For some grades of 
celluloid a melting-point of 165° is sufiicient but for high-grade ma- 
terial the melting-point should not be lower than 174°. A saturated 
solution in 95 per cent alcohol should show no yellow color and when 
kept in ordinary diffused daylight in a colorless transparent bottle the 

]8B pqj. the quantitative determination of chlorine in synthetic camphor the method 
o£ Drogin and Eosanoff (J. Am. Chem. Soc. 38, 711 [1916]), or that o£ Van Winkle 
and Smith (J. Am. Chem. Soc. J^. 333 [1920]) Is recommended. The per cent, of 
borneol may be determined by acctylating with acetic anhydride, in the usual manner, 
and determining the saponification number of the product ; borneol or isoborneol may 
also be separated from camphor by the phthalic anhydride method. 



510 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

camphor should not become visibly discolored in 30 days. Nitro 
derivatives are very apt to cause the development of a yellow color. 
The presence of nitro derivatives also causes the formation of a slight 
tarry or resinous residue when a few grams of the camphor are sub- 
limed slowly from a watch glass. The chief impurities encountered 
in commercial natural camphor are camphor oil, water and mineral 
matter. 

As regards the yields of synthetic camphor obtained in industrial 
practice there are naturally no reliable published data. Schmidt^" 
gives the following yields : solid bornyl chloride 43 per cent, camphene 
from bornyl chloride 95 per cent, isobornyl acetate from camphene 
86 per cent, saponification to isoborneol 98 per cent, oxidation of iso- 
borneol to camphor about 80 per cent, or a net yield from the original 
turpentine of 24 per cent of the theory. Austerweil ^^* gives the yield 
of crystalline bornyl chloride as 55 to 60 per cent and Ullman ^'° 
gives 55.3 per cent of the theory as the yield of the chloride. Accord- 
ing to the writer's experience these yields are too low, particularly as 
regards bornyl chloride, which with reasonable skill can be obtained 
in yields of 75 to 78 per cent of the theory, and the acetylation of 
camphene can be relief upon to give a yield of isobornyl acetate cor- 
responding to 92 to 94 per cent of the theory. The net yield of cam- 
phor should be 45 to 50 per cent of the theory. Methods for the 
synthesis of camphor which are of theoretical interest are discussed 
in connection with the constitution of camphor. 

'^ Chem. Ind. 29, 241 (1906). 
■«» German Pat. 211,799 (1908). 
"' Enxykl. techn. chem. Ill, 257. 



Chapter XIV. Cyclic Non-benzenoid 
Hydrocarbons. 

Cycloheptane, Cyclooctane, Cyclononane and Polynaphthenes. 

Cycloheptane and its derivatives are difficult to prepare and have 
been comparatively little studied. The ketone, cycloheptanone 
(suberone), is the material most frequently employed for the prepa- 
ration of other cycloheptane derivatives and Willstatter has used the 
cycloheptatriene (tropilidene) formed by the exhaustive methylation 
and decomposition of tropidine, and also cycloheptatriene from anhy- 
dro-ecgonine. Eucarvone has also been employed in the preparation 
of other cycloheptane derivatives. 

The physical properties of cycloheptane, cycloheptene, cyclohep- 
tadiene (hydrotropilidine) and cycloheptatriene (tropilidine) are as 
follows,^ 

Q° 
Boiling-Point d 0° ^D 

Cycloheptane 117. °-117.5° 0.8253 

Cycloheptene 114.5°-115. ° 0.8407 

A''-cycloheptadiene 120. °-121. ° 0.8810 1.495997 

A' '''-cycloheptatriene 116. ° (corr.) 0.9083 1.5175 

Cycloheptane was made by Markownikow ^ from cycloheptanone 
by reducing the ketone to cycloheptanol (suberyl alcohol) and reduc- 
ing the corresponding bromide by zinc dust and alcohol. Willstatter 
and Kametaka ^ reduced cycloheptadiene (hydrotropilidene) by Saba- 
tier and Senderens' method, at 180°. The cycloheptane made under 
these conditions is quite pure but at 235° further hydrogenation to 
normal heptane occurs and at 250° this change is quite rapid. Cyclo- 
heptanol cannot be reduced to cycloheptane by heating with hydri- 
odic acid, methylcyclohexane being formed.* 

The formation of a hydrocarbon, C^JIs, by distilling methyltropine- 

' Willstatter, Ann. Ml, 204 (1901). 

'Ann. SSn, 59 (1903). 

' Ber. 1,1, 1480 (1908). 

'Markownikow, J. praM. Chem. (2) i9, 430 (1894). 

511 



512 CHEMISTRY OF THE NON-BEN ZENOW HYDROCARBONS 

methyl iodide was observed by Ladenburg, and Merling^ obtained 
the hydrocarbon by exhaustive methylation of tropidine and decom- 
posing the tertiary ammonium hydroxide by heat. The conversion of 
tropinic acid to normal pimelic acid led to the view that the tropine 
bases and their nitrogen free decomposition products possessed a 
cycloheptane ring and that tropilidine and hydrotropilidine were 
cycloheptatriene and cycloheptadiene respectively. Willstatter con- 
firmed this by synthesizing both hydrocarbons. 

Cycloheptene can readily be prepared by decomposing cyclo- 
heptyl iodide in the usual manner, and the addition of bromine gives 
1.2-dibromocycloheptane, but when the dibromide is heated with 
quinoline two bromine atoms are removed, not two molecules of hydro- 
bromic acid, the resulting product being cycloheptene, not the expected 
diene. Alcoholic caustic potash converts the dibromide into the un- 
saturated ether, and similarly, heating the dibromide with dimethyl 
amine forms a dimethyl amino derivative, 

CH^ — CH^ — CHBr CH^ — CH^ — CH . N (CH3) ^HBr 

\ +2NH(CH3), \ 

CHBr > CH 

/ / 

CH, — CH3 — CH2 CH, — CH, — CH 

By adding methyl iodide to the resulting base and decomposing the 
tertiary ammonium hydroxide by heat, Willstatter made A^- '-cyclo- 
heptadiene, which proved to be identical with hydrotropilidene 

H 

/ 

CH, — CH, — CN(CH3)3.0H CH, — CH = CH 



\ 
CH 



\ 

CH. 



CH, — CH, — CH CH, — CH, — CH 

Willstatter also made A^-'-cycloheptadiene in another manner." 
From the decomposition products of cocain A^-cycloheptenecarboxylic 
acid was obtained, which was treated with hydrogen bromide to form 
2 bromocycloheptanecarboxylic acid, which was decomposed, losing 

"Ber. %!,, 3109 (1S91). The cycloheptane ring is bridged in the following manner, 
CH2 — CH — CH2 
I 
NH > CH2 (tropane). 

CH2 — CH — CH2 
•Einhorn & Willstatter, Ann. 280, 136 (1894). 



BICYCLIC NON-BENZENOID HYDROCARBONS 



513 



HBr to form a mixture of the A^ and A^ acids. The A^ acid was sepa- 
rated by fractional crystallization, converted to the amide, and the 
latterlreated with bromine and alkali (Hofmann's reaction) to form 
the amine, from which, by the method of exhaustive methylation, the 
conjugated diene was made. 



H 



K 



H^ 



-CH,- 



-CHr 



-CH,- 



-CH, 



-CH 
\ 



-CH 
-CH 



H, 



K 



K 



H, 



■CHr 



-CR- 



-CH 
-CH 



-CH= 



-CH, 



=CH 

> 

-CH 



;CH 



The addition of bromine to A^'-cycloheptadiene takes place in 
accordance with the general rule of the addition of bromine to con- 
jugated dienes, to form 1.4-dibromo-A^-cycloheptene, which by heat- 
ing with quinoline, loses 2 molecules of hydrogen bromide to form 
cycloheptatriene 



CH, — CH 



CH, — CH. 



= CH 

\ 

CH 

— CH 



CH. 



+ Br, 



Br 



H 



CHo — CHj 



— CH 

\h 

/ 

— CH.Br 



CH =CH — CH 
\ 



/ 



CH 



:h, — CH = CH 



Cycloheptatriene resinifies rapidly in contact with the air and follows 
generally the behavior of conjugated dienes. 

Tetramethylcycloheptatriene was made by treating eucarvone with 
magnesium-methyl iodide.' It is not definitely known whether the 



'Eupe 4 KerkoviuB, Ber. U, 2702 (1911). 



514 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 

third double bond is in the ring or semicyclic. The physical proper- 
ties of the hydrocarbon are as follows, boiling-point 67°-67.5° (11 
mm.), d 20° 0.8687, nj) 1.5066, Mj) 50.70, EMp 1.33. Its constitu- 
tion may be inferred from the constitution of eucarvone (q.v.). It is 
very little changed by boiling with 10 per cent sulfuric acid. Reduction 
by sodium and ethyl alcohol yields a diene, CnHig, distilling at 64.5°- 
65.5° (12 mm.). 

Diazoacetic ester combines with toluene and the xylenes to form 
derivatives of norcaradienecarboxylic acid. Thus when toluene and 
diazoacetic ester are boiled together (copper powder as a catalyst is 
not necessary) nitrogen is rapidly evolved and 3-methylnorcara- 
dienene-7-carboxylic ester is formed. Para-xylene, treated in the 
same way, yields the bicyclic ester, and this ester can be treated in 
several ways to break the 3-carbon ring. The first condensation 
product is regarded by Buchner and Schulz * as the ethyl ester of 
2.5-dimethyl-A^*-norcaradienenecarboxylic acid. By heating the 
amide to 160°-170°, or heating the crude condensation product with 
15 per cent sulfuric acid, or by heating with water at 160°-170°, the 
3-carbon ring is broken, forming chiefly 2.5-dimethyl-A^-^'-cyclohep- 
tatriene-7-carboxyIic acid, melting-point 136°-137°. 
CH, CH, 

I I 

CH = C — CH CH, — C==CH 

I |\ 1 \ 

...... CH.COAH5 C.COAH5 

/ 1 / 

CH = C — CH CH =C CH 

CH, CH 



3 



When the A^-°-' acid is reduced by sodium amalgam two atoms of 
hydrogen are added forming what Buchner regards as the A^-^ acid, 
melting-point of the crude acid 38°-40°, but too unstable to purify. 
Obviously a number of isomeric acids containing two double bonds are 
possible, and by adding hydrogen bromide to the A^-^ acid and then 
removing HBr by the action of alkali, Buchner obtained an isomeric 
acid melting at 82°, which he regards as the A^^ acid. Reduction by 
hydrogen and platinum black yields 2 . 5-dimethylcycloheptanecar- 
boxylic acid, an oil at ordinary temperatures (amide melting at 185°- 
186°). 

'Anti. S7S, 259 (1910). 



BICYCLIC NON-BENZENOID HYDROCARBONS 515 

Goldsworthy and Perkin ' made trans. 1.2.4. -cycloheptanetri- 
carboxylic acid by the latter's well-known method of synthesis, using 
sodium ethylate as a condensing agent, 

CO.C^H, 
CH, — CH(C0AH,)2 CH, — CH< 

I CH^Br I CH^ 

CH, + I > CH, I 

I CHBr I CH — COAHb 

CH, — CH(C0AHb)2 I I / 

COAH5 CH, — CH 

CO,C,H, 

The ester was saponified by alcoholic caustic potash in the usual 

manner, the free acid melting at 198°-200°. 

Cycloheptarume, the raw material most frequently employed for 

preparing cycloheptane derivatives, may be prepared by heating the 

calcium salt of suberic acid." When purified by means of the semi- 

carbazone or the bisulfite compound and regenerating the ketone, it 

21.5° 
has the following physical properties, boiling-point 180°, d 0.9498, 

4° 

n 1.46027, M 32.35 (calculated 32.34)." 

Cycloheptanone forms a dibenzylidene derivative, 
CiHsO. (CH.CeH5)2, 
melting at 107°-108°, and like cyclopentanone and cyclohexanone, 
forms a series of well crystallized compounds with other aldehydes 
(with anisaldehyde, melting-point 128°-129° ; with cinnamic aldehyde, 
melting-point 198°; with piperonal, melting-point 137°). It con- 
denses with acetone but with much greater difiiculty than the lower 
cyclic homologues.^^ Like other cyclic ketones the oxime is rear- 
ranged by sulfuric acid to the so-called isooxime, 
CH, — CH., — CH, — CO 
J 



i 



JH, — CH, — CH, — NH • 



J.2 W-1.J.2 ^^^2 



This isooxime is readily split by heating with hydrochloric acid to 
amido-n-heptylic acid. The ketone reacts normally in the Grignard 
reaction, for example, with magnesium-methyl iodide to form 1-meth- 



'J. Ohem. Soc. 105, 26T5 (1914). 
'» Wislicenus & Mager, Ann. 275, 357 (1893). 
"Auwers, Ann. 410, 283 (1915). 
"Wallach, Ann. S9i, 366 (1913). 



516 CHEMISTRY OF THE NON-BENZENOID HYDROCARBONS 



ylcycloheptaiiol-(l), which in turn readily decomposes to ^^-methyl- 
cycloheptene, boiling-point 137.5°-138.5° 



^19.50 '■'''' 



^D 



1.4581. 



The reactions of this hydrocarbon are parallel to those already dis- 
cussed; for example, it forms a nitrosochloride (melting-point 106°) 
which on heating with dimethylaniline yields the unsaturated oxime 
which in turn may then be hydrolysed by dilute acids to the unsatu- 
rated ketone A^-2-methylcycloheptene-3-one (boiling-point 200°- 
205°, d„,„ 0.9695). 



21 



-CH- 



-CH, 



-CH^— CH^ 



-CH,— CH, 



-CH, — CH, 



>c. 



-CH, — CH 
-CH^ — CH^ 



_CH-c/NO« 

V^' ■ 

-CH, — CH, 



-CH,— C^ 

/ 
-CH 



NOH 



;C-CH, 



-CH,- 



-CH,- 



-CHr 



-CO 

> 

-CH 



C-CH, 



It also condenses with bromo- acetic ester in the presence of zinc to 
give cycloheptanol acetic acid, from which Wallach " obtained meth- 
enecycloheptane in the usual manner. Methenecycloheptane dis- 
tills at 138°-140°, d 0.824, n„ 1.4611. This hydrocarbon under- 
goes reactions strictly parallel with those which have already been 
discussed in connection with other hydrocarbons having the methene 
>C =: CHj group, for example, on oxidation it forms a glycol (melt- 
ing-point 50°-51°) which is converted to cycloheptane aldehyde by 
heating with dilute acids. 

Kotz ^* has studied the chlorination and bromination of cyclohep- 
tanone and finds that, like cyclohexanone, the halogen enters the 
ring in the CH2 group adjacent to the carbonyl group, these facts 
harmonizing with the view that the ketone reacts with the halogen in 
the enol form, adding CI2 or Br^ and subsequently splitting off a mole- 
cule 01 halogen acid. The chloroketone is much more stable than the 
bromoketone. The chloroketone is not hydrolyzed by aqueous caustic 
potash at ordinary temperatures but, on warming, the corresponding 
oxyketone is formed (yield poor) . Oxyketones of this type show most 
interesting properties; neither the oxyketone nor its methyl ether 
forms an oxime and the methyl ether may readily be prepared by 

"Ann. Sli, 158; S^S, 146. 
"Ami. iOO.il (1913). 



BlCYCLiC l^ON-MNZENOlD HYDROCARBONS 



517 



saturating the methyl alcohol solution by hydrogen chloride, like the 
esterification of a carboxylic acid. The unsaturated ketone, A^-cyclo- 
heptenone, was reduced by Kotz, by Paal's method, to cycloheptanone, 
confirming Willstatter's ^° constitution for this ketone (tropilene). 

Eucarvone: When carvone combines with one molecule of hydro- 
bromic acid and is then treated with alkali to remove HBr, the result- 
ing ketone proves to be an isomer of carvone. Baeyer, the discoverer 
of the reaction, regarded eucarvone as bicyclic having a cyclopropane 
ring although he himself pointed out several objections to such a 
structure. Dihydroeucarvone and tetrahydroeucarvone he regarded 
as derivatives of cycloheptanone. Further objections to Baeyer 's con- 
stitution for eucarvone 

CH, 



i 



/ \ 

HC C: 







H^C CH 

\ / 

C 



eucarvone (Baeyer) 



C(CH3), 

were pointed out by Wallach, who prepared a condensation product 
with benzaldehyde, clearly indicating the presence of the — CHj — CO — 
group. Also, when prepared f