934
OUSTAV EGLOFF AND ROBERT C. KUDER
STUDIES OF T H E PHYSICAL PROPERTIES OF ALICYCLIC HYDROCARBONS. I1
BOILING POINTS OF MONOCYCLIC HYDROCARBONS GUSTAV EGLOFF
AND
ROBERT C. KUDER
Research Lahoratories, Universal Oil Products Company, Chicago, Illinois Received July 34, 1948 I. INTRODUCTION
In the preceding paper (4) of this series the relationship between the molal volume and the structure of alicyclic hydrocarbons was discussed. Extension of the study to boiling points makes evident that, chaotic though the alicyclic density data are, the boiling-point data are even more discordant and incomplete. It has been powible, nevertheless, from the consideration of over three hundred compounds to make some generalizations and interesting observations on the relationship between the boiling points of alicyclic hydrocarbons (not containing fused rings) and their structure. The data are drawn chiefly from the collected physical constants (3) ; other more recent sources are appropriately indicated. 11. BOILING POINTS OF CYCLANES
It has been recognized for a long time (6, 8) that, in general, the effect of ring formation is an increase in boiling point and that the increase becomes larger as the ring becomes larger. Thus the unsubstituted cyclanes, from cyclopropane to cyclodecane, have boiling points from 9' to 27'C. higher than those of the corresponding normal alkanes and from 15' to 3OOC. higher than those of the isomeric 1-alkenes (see table 1). 111. EFFECTS OF SIDE CHAINS
In the alkane series branching of a straight chain lowers the boiling point (1). The adherence of alkylcyclopentanes to this rule has already been noted by Crane (2), but it also can be carried over to other alkyl-substituted cyclanes and cyclenes. The hydrocarbon with the unbranched side chain always has the highest boiling point (see table 2 for a few examples). Out of twenty-five comparable sets of isomers, comprising a total of seventy-one compounds, only one set (two compounds) appears to be even doubtful in this respect: the boiling point of 1-propylcyclopentene is reported .as 131-133OC. and 131.5-132.5OC., while that of 1-isopropylcyclopenteneis reported as 133-135°C. at 755 mm. and 131.4-133.4'C. at 760 mm.; obviously the data are insufficient to draw any conclusions. Inspection of table 2 shows not only that simple n-alkylcyclanes and -cyclehes have the highest boiling points among isomers but also that among isomeric dicyclohexylalkanes that one has the highe'st boiling point which has the rings at the opposite ends of the straight chain. It was shown previously (4) that the same rule holds for molal volumes of dicyclohexylalkanes. There is a slight
.
BOILING
935
POINTS OF MONOCYCLIC HYDROCARBONS
difference, however, in the molal volumes of the monoalkylcyclancs: while a secondary or tertiary alkyl group gives both molal volumes and boiling points lower than the isomeric straight chain, an isoalkylcyclane has a lower boiling point but higher molal volume than the corresponding n-alkylcyclane. The boiling point is lowered not only by increased branching within a single chain but also by increased branching from the ring; i.e., in isomeric compounds
TABLE 1 Effect of ring closure on boiling point I
BOILING POINT OF CICLANE
1
BOILING POINT 01 1-ALYENF
A
"C.
"C.
"C.
9 12 13 12
-47.7 -6.47 30.1 63.5 93.1 122.5 146 171
15 18 19 17 25
BOILING POINT OF ALKANE
A
'C.
-I1
"C.
-33 11.2 49.3s 80.70 118 146 170-2
mi
~
-42.2 -0.5 36.08 68.8 98.4 125.6 151 174
20
20 20 27
2.3
25 30
TABLE 2
Effectof chain branching on boiling point COMPOUND
1
BOILINO POINT
'c.
Butylcyclohexane.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sec-Butylcyclohexane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Isobutylcyclohexane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . tert-Butylcyclohexane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
179 177.2 170 3-171.7 1-169
1-Amyl-1-cyclohexene .......................................... 1-Isoamyl-1-cyclohexene ...................................... 2-Cyolohexen-l-ylpentane .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
203.4-205 194.5-196.5 194
1,4-Dicyclohexylbu tane.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-Methyl-l ,3-dicyclohexylpropane. ............................
304-306
1,l-Dicyclohexylbutane.. .....................................
280-282
290-292
of given alicyclic content, the boiling point in general decreases as the number of aliphatic side chains increases (neglecting the effect of any other contributing factors such as further branching within a single chain, double-bond position, etc.). This rule is illustrated in table 3 with six alicyclic and four aliphatic carbon atoms. The effect of the relative position of the side chains in dialkylcyclanes is definite and can be related to the corresponding effect in alkanes. Among
936
GUSTAV EGLOFF AND ROBERT C. KUDER
isomeric dimethylalkanes the one with both methyl groups on the same penultimate carbon atom of the straight chain (Le., the 2,2-dimethylalkane) has the lowest boiling point and those with the two methyl groups on adjacent carbon atoms (2,3- or 3,4-dimethylalkane) have the highest boiling points (1, 5 ) . Likewise in isomeric dimethylcyclanes, the one with both methyl groups attached to the same carbon atom (a 1,l-dimethylcyclane) has the lowest boiling point
TABLE 3 Effectof number of side chains on boiling point BOILING POINT
‘C.
i
Butylcyclohexane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-Methyl-4-propylcyclohexane ............................... 1,4-Diethylcyclohexane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
179 171 3-177.1 174.6-176.4 168-170 168-170at 762 rnm. 162-164 at 765 mrn.
~
1,3-Dimethyl-5-ethylcyclohexane. ....... . . . . . . . . . . .................... cis-1 ,2,3,5-Tetramethylcyclohesane. trans-l,2,3.5-Tetramethylryclohexane.. . . . . . . . . . . . . . . . . . . . I
.I
TABLE 4
EffectoJ position of methyl groups on boiling point BOLLISG P O l N I
CO\IPIIL.&O
--
~
_______
“C.
I
cis(?)-l ,2-Dimethylcyclopropane. . . . . . . . trans(?)-1,2-Dimethylcyclopropane. . . . . . . 1 , l-Dimethylcyclopropane. . . . . . . . . . . ,
:::
~
~
cis-1,2-Dimethylcyclopentane . . . .,............I trans-l,2-Dirnethylcyclopentnne. . . , . . . . . . . . . . . . ., 1,3-DirnethyIcyclopentane.. . . . . . . . . . 1,l-Dimethylcyclopentsne . ,... . . . . . . .
i
37.2-37.7at 755.5mm. 28.8-29 at 758.9m m . 21 99.2 91.8 90.5-90.8 86.5-87.5
I
cis-l,2-Dimethylcyclohexane. . . . . . . I trans-1, 2-Dimethylcyclohexane . . . . . . . cis-l ,i-Dimethylcyclohesane , , , ........ cis-l,3-Dirnethylcyclohesnne. . . . .... trans-1.3-Dimethylcyclohexnne ........ trans-1, ?-Dimethylcyclohexane. . . . . . . . . . . 1,l-Dirneti~ylcyclohexane . . . ., . . . ~
..............
. .
I
129 124 123 122
120.5 120 119.9
~___
and the one with the two methyl radicals on adjacent carbon atoms (e.g., 1,2dimcthylcyclanes) has the highest boiling point. The 1,3-and 1,4- isomers haye boiling points between those of the 1 , l -and 1,2- isomers. These relationships are exemplified in table 4. vodified relationships necessary for cyclenes are discussed later in the section on double bonds. The same rules which apply to the dimethyl derivatives apparently apply also
BOILIXG POINTS OF MONOCYCLIC HYDROCARBONS
937
to other dialkyl derivatives, even when both groups are not the same, as indicated in table 5 . TWOexceptions, probably due to insufficient data, arc the 1,2-and 1,3-methylisoamylcyclohexanesand the 1 , l - and 1,3-diethylcyclopentanes. trans-1 ,2-Diethylcyclopentane also occupies an unexpected position, TABLE 5
Effectof poaitzon o j hzgher alkyl groups on boding poznt "C.
in. 7 - m.3 121.35-121.75 120.5-121at 756 mm. 152.58 146.37-146.38 146-148 at 742 mm
1-Methyl-3-propylcyclopentane
142 5 at 759 mm. 142-144 cis-l,2-Diethylcyclopentane. ................... .......................... 1,l-Diethylcyclopentane. l13-Diethylcyclopentane, ........................ trans-1,2-Diethylcyclopentane ....................
153.55-153.58 150.5at 757 mm. 148-9 at 767 mm. 147.53-147.55
1-Methyl-2-ethylcyclohexane .. . . . . . . . . . . . . . . . . . . . 1-Methyl-4-ethylcyclohexane. ...................... 1-Methyl-3-ethylcyclohexane.. . . . . . . . . . . . . . . . . . . .
152.6-154.7 150 .l-151 148.4-150
1-Methyl-2-propylcyclohexane. ................... 1-Methyl-4-propylcyclohexane.. . . . . . . . . . . . . . . . . . . l-~Methyl-3-propylcyclohexane. ..................
175.2-177.O 174.3-177.1 171 .O-173.O
1-Methyl-2-isopropylcyclohexane. ................ cia-I-Methyl-4-isopropylcyclohexane ..............
171 168.5 166-168 161 .O
i
1-Methyl-3-iaopropylcyclohexane. ..................
I ~
trans-1-Methyl-4-isopropylcyclohexane .........
1
1-Methyl-2-butylcyclohexane. ......... 1-Methyl-4-butylcyclohexane,. . . . . . . . . . . . . . . . . . . . I-Methyl-3-bu tylcyclohexane.. . . . . . . . . . . . . . . . . . . . " " " "
i
1 -Methyl-3-isoarnylcyclohexane. . . . . . . . . . . . . . . . I. 1-Methyl-2-isoamylcyclohexane . . . . . . . . . . . . . . . . .
i
195.6-198.1 195.9-196.6 194.8-195.2 205 204
but its low boiling point is possibly due to the low boiling points possessed in general by trum compounds. In twenty sets of cis-trans isomers the difference in boiling points ranges from 0' to 7.5'C. (see table 6). It was shown previously (4)for the same twenty sets that the molal volume relationships are just the
938
GUSTAV EGLOFF AND ROBERT C. KUDER
reverse (i.e., the trans compound has the higher molal volume but the lower boiling point). TABLE 6 Effect of cis-trans isomerism on boiling point
1-Methyl-4-isopropylcyclohexane. .............................. ' 1,2-Dimethylcyclopentane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i 1-Methyl-2-ethylcyclopentane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-Methyl-3-propylcyclopentane ................................ , 1,2-Diethylcyclopentane.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,2.3,5-Tetramethylcyclohexane. ............................ 1,2-Dimethylcyclohexane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,2c,4-Trimethylcyclohexane. .................................. ! 1,2,4,5-Tetramethylcyclohexane, ............................. 1,4-DimethylcycIohexane: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l e , 2,4-Trimethylcyclohexane. ........................... 1,2c,4'-Trimethylcyclohexane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,3-Dimethylcyclohexane.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1C,2,4'-Trimethylcyclohexane.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,2,3-Trimethylcyclohexane.. . . . . . . . . . . . . . . . . . . . . . . . . . Il 1,3,5-Trimethylcyclohexane. ................................ ' 1c,2c, 4-Trimethylcyclohexane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.5 7.4 6.4 6.2 6 .O 6 5 4 4 3 3
i
I
~
~
~
3 2 2 2
'
lC,2.4,5-Tetramethyl-l-cyclohexene ........................... 1,4,5-Trimethyl-l-cyclohexene. ...............................
1.5 1
I
3 2
~
4-Methyl-5-isopropenyl-1-cyclohexene .......................... IV. EFFECTS OF DOUBLE BOKDS
In discussing the effects of unsaturation it will be convenient to use the classification of Boord (1) for the different types of double bonds. This system divides alkenes into five types, depending on the amount of substitution a t the double bond:
R
R-CH-CH-R Type I1 R
\ R
/
\
C=CH-R
Type I V
R
\
R' Type I11 R
c=c /
'
R'
Type V
939
BOILING POINTS OF MONOCYCLIC HYDROCARBONS
Although this classification was originally devised for aliphatic double bonds, it may also be used in the alicyclic field for double bonds which are cyclic (in cyclenes and alkylcyclenes), semicyclic (in alkylidenecyclanes), or aliphatic (in alkenylcyclanes). The introduction of a Type I double bond into any alkane, branched or unbranched, lowers its boiling point. The only Type I alicyclic hydrocarbons possible are certain w-alkenylcyclanes;of these the boiling points of only five are known, three of which have boiling points lower than the corresponding alkylcyclanes, one higher, and one doubtful (see table 7). It is interesting to note that the one exception to the general Type I d e , vinylcyclopropane, waa previously shown to be the only exception to the rule that the shift of a double bond from the side chain to the ring causes a reduction in molal volume (4). The introduction of a Type I1 double bond into alkanes, branched or unbranched, usually causes a lowering of the boiling point; the only exceptions are TABLE 7 T y p e I alkenylcyclanes
1
COYWUND
I
Vinylcyclopropane... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Allylcyclopentsne . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I Vinylcyclohexane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Allylcyclohexane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Cyclohexyl-l-butene , , . , . . . . , , . , , , , . . , . . , , . , , , , , , . .I ~
i
~
, ,
,
, ,
,
,
, ,
,
DOUBLE-BOND INCPEYENI I N BOILING POINT
"C.
.
5.6
-6 -1 (?)
-3 -4
trans-2-butene and a few high-boiling cis-2-alkenes. In alicyclic hydrocarbons a Type I1 double bond causes a lowering of the boiling point unless i t i s in a six-membered ring, in which case it causes a raising of the boiling point. This peculiarity of the six-membered ring is well illustrated by comparing cyclohexene, which boils 2'C. higher than cyclohexane, with cyclopentene, which boils 4.9'C. lower than cyclopentane. I t has already been pointed out by Crane (2) that for a number of 3-alkylcyclopentenes the boiling points are about 5°C. lower than for the corresponding alkylcyclopentanes; the boiling-point increments for all the known Type I1 alicyclic hydrocarbons are shown in table 8. Exceptions to the rule are 4-methyl-l-cyclopentene, 3,5-diethyl-l-cyclohexane, and 3-methyl-6-isopropyl-1-cyclohexene when compared to the cis-cyclane; it will also be noticed throughout the comparisons of the other three types that the high boiling points of the cis-polyalkylcyclanes often cause apparent exceptions to the general rules. In the case of aliphatic hydrocarbons it was noted by Boord (1) that a Type I11 alkene boils just slightly above the parent alkane. Likewise, in Type I11 alkenylcyclanes the boiling points are a few degrees above those of the corresponding alkylcyclanes (see table 9). Exceptions are 2-methylene-1,4- and
940
GCSTAV EGLOFF AXD ROBERT C. KUDER
l-methylene-3,5-dimethylcyclohexanes; there are also a few which boil lower than the parent cis-dialkylcyclanes. Introduction of a Type IV or Type V double bond into branched alkanes produces a fairly large increase in the boiling point. Similarly, a Type IV or V TABLE 8 T y p e II unsaturated alicyclic hydrocarbons ComOuND
DOUBLE-BOSD INCREYPSI
,
IN BOlLlNC POINT
'C
Cyclohutene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclopentene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-Methyl-l-cyclopentenea.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-Methyl-1-cyclopentene.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-Ethyl-l-cyclopentene* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,3-Dimethyl-l-cyclopehtene. ............................ 3-Propyl-1-cyclopentene* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-Isopropyl-l-cyclopentene*. ................................. 1-Cyclopentyl-2-butene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-Butyl-l-cyclopptene' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-sec-Butyl-l-cyclopentene*~ .................................. 3-Isobutyl-l-cyclopentene*. ............................ 3-lerl-Butyl-l-cyclopentene* .............................. 3,3-Diethyl-1 -cyclopentene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-.4myl-l-cyclopenteriet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-Hesyl-1-cyclopentenet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-Cyclohexyl-2-butene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cycloheptene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cycloijctene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclohesene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-Methyl-l-cyclohexene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Methyl-1-cyclohexene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4,4-Dimethyl-l-cyclohexene.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,5-Dimethyl-l-cyclohexene. . . . . . . . . . . . . . . . . . . . . . . . 3-Propyl-l-cyclohexene, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.5-Trimethyl-l-cyclohexene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-krt-Butyl-1-cyclohexene ................................... 3-Methyl-6-isopropyl-l-cyclohexene . . . . . . . . . . . . . . . . . . . . . . . . .
'
-9 -4.9 -7 4 -5.3 -9 -4.9 -5.2 ? -5.1 - 4 .8 -4.7 -5.8 -6
'
i
' ~
~
~
~
-5
-4 -2 -3 -3 2 4.1 3
i
I
5 (trans)
'
2 (cis) 1
,
2 (?) 5
'
6.1 (trans) 1.4 ( c i s ) - 10
-
~
~
3,5-Diethyl-l-cyclohexene. . . . . . . . . . . . . . . . . . . . . -
* Reference 2.
t Reference 7 . double bond causes increases in the boiling points of alicyclic compounds, as illustrated in tables 10 and 11; there are several exceptions, however, particularly among Type IT cyclopentenes: 2,2-dimethyl-l-isobutylidenecyclopropane, 2,3,3-trimethyl-l-cyclopentene, 3-methyl-l-isopropyl-l-cyclopentene, l-heptyl-
941
BOILING POIXTS O F MOKOCYCLIC HYDROCARBOSS
1-cyclopentene, 1-sec-butyl-1-cyclohexene, 3-methyl-l-(3-methylc~clohex~l)-lcyclohexene. and 1-methyl-2-isopropylidenecyclohexane. The generalization that the boiling points of isomeric alkenes increase with the type number (1) holds only in a rough sense for unsaturated alicyclic compounds. When the double bond is restricted, however, to the ring (Types 11, IF', and V alkylcyclenes), the rule is followed definitely. Thus, among monoalkyl-lcyclenes the 1-alkyl isomer has a higher boiling point than either the 3- or the TABLE 9 T y p e I I I alkenylcyclanes DOLBLE B O N D IYCREYEhI
COYPOITNI)
I Y BOlLlNC POlVI
I
Methylenecyclobutane Methylenecyclopentnne 1-Methylene-3-methylcyclopentane l-1Rlethyl-2-1sopropenylcq clopentane Methylenecyclohe\ane 1-Methylene 2-methylcyclohexane
5 3 7
I
1 Rlethylene-3-meth>lcyclohexsne 1-Methylene 4-methylcyclohexane Isopropenylcyclohexane 1 Methylene-3 3 dimethylcyclohexane 2-Methylene-1 4-d1methyleyclohexane
I
I
3 2 7 (trans) -3 (czs) 3 (trans) 7 (czs) 2 (trans)
-6"
2
-5
l-lhIethylene-3,5-dimethylcyclohevane 1-hlethyl-3-~sopropenglcyclohexane 1 Methyl 4 isopropenl lcyclohevane
'C
3
I
I
-3 (trans) - 5 (czs) 3 b (trans)
1(as) hlethylenecycloheptane
5
4-alkyl isomer. Among isomeric dialkyl-1-cyclenes (the alkyl groups need not be alike) the order for increasing order of boiling points is as follow:
An example of tkis order is shown in table 12. .1reversal of these relationships applies to molal volumes, since it has been shown (4) that for monoalkylcyclenes the Type 11-isomer has the smallest molal volume at 2OOC. and that for dialkylcyclenes the Type V isomer has the smallest volume. (It was not found possible, however, to establish a definite molal volume order for the Type I1 and Type IF' isomeric dialkylcyclenes alone.) I n alicyclic dienes conjugation of a double bond in the ring with one completely
942
.
GUST.4V EGLOFF AKD ROBERT C KUDER
TABLE 10 Type IV unsaturated alicyclic hydrocarbons I
COMPOUND
'
DOUBLE-BOXD INCREXEST IN BOILING P O I N I
'C
Ethylidenecyclopropane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,2-Dimethyl-l-isobutylidenecyclopropane. .................. 1.Methyl.l.cyclobutene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.Methyl.l.cyclopentene . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ethylidenecyclopentane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 1.Ethyl.l.cyclopentene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 2,3.Dimethyl-l-cyclopentene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~
~
~
1-Propyl-1-cyclopentene ..................................... i 1 -Isopropyl-1-cyclopentene . . . . . . . . . . . . . . . . . . . . . . ........I 2.Methyl.l.ethylidenecyclopentane. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1-Methyl-3-isopropyl-l-cyclopentene . . . . . . . . . . . . . . . . . . . . . . . . . 1-Methyl-4-isopropyl-l-oyclopentene . . . . . . . . . . . . . . . . . . . . . . . . . . 3-Methyl-l-isopropyl-l-cyclopentene . . . . . . . . . . . . . . . . . . . . . . . . . 1-Amyl-1-cyclopentene'. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-Isoamyl-1-cyclopentene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,3-Dimethyl-4-isopropyl-l-cyclopentene ...................... 1-Hexyl-1-cyclopentene* ...................................... 1-Heptyl-1-cyclopentene' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-Methyl-1-cyclohexene ........................................ 1-Ethyl-1-cyclohexene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ethylidenecyclohexane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1,3-Dirnethyl-l-cyclohexene ..................................
'
. 13 ?
3.2 12 5 4 (trans) -3 (cis) 1 6 2 (trans) -4 (cis) -6 1 2 ?
-5 ? ? 3 ( 3 2 -4 9.2 2 5 i
l15-Dimethy1-1 -cyclohexene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1,4-Dimethyl-l-cyclohexene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4-Methyl-l-ethyl-l-cyclohexene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,4,4-Trimethyl-l-cyclohexene ............................... l13,5-Trimethyl-l-cyclohexene ..............................
3
5 (trans)
5 (cis) 7 (trans) 4 (cis) 5 (trans) 4 (cis) 00) 9 6 4 2 2 1 1
~
2 (trans) 1 (cis) 3 -4
943
BOILING POINTS OF MONOCYCLIC HYDROCARBONS
TABLE
10-ConcZuded DOUBLE-BOND INCLEYENT IN BOILIN0 POINT
conmmD
2-Methyl-4-isopropyl-1-cyclohexene ............................ I-Methyl-4-isopropyl-1-cyclohexene
2 15 (trans) 8 (cis) 10 (trans) 3 (cis)
4-Methyl-1-isopropyl-I-cyclohexene 1-Amyl-1-cyclohexene............................... 1-Isoamyl-1-cyclohexene .............................. 4-Methyl-7-butyl-l-oyclohexene . . . . 4-Methyl-l-butyl-l-oyclohexene . . . .
3 1
I-Methyl-1-cycloheptene. .......... 1-Methyl-I-cycloiiotene. . . . . . . . . . . . 1-Cyclopentyl-I-cyclopentene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-Cyclohexyl-1-cyclohexene .................................... 3-Methyl-l-(3-methylcyclohexyl)-l-cyclohexene. ................
0.5 0.5 4 ? ? 3 -6
* Reference 7. T A B L E 11 Type V unsaturated alicyclic hydrocarbons ~
C O W W D
1,2-Dimethyl-l-cyclopentene. ..................................
1
i
Isopropylidenecyclopentane.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-Methyl-2-ethyl-l-cyclopentene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1,2,3-Trimethyl-l-cyclopentene. ............................... 2-Methyl-I-isopropylidenecyclopentane. ....................... 1,2-Diethyl-l-cyclopentene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,2-Dirnethyl-l-cyclohexene. ................................... Isopropylidenecyclohexane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-Methyl-2-ethyl-l-eyclohexene . ...................... I , 2,3-Trimethyl-I-cyclohexene. ................................ 1-Methyl-2-propyl-l-cyclohexene . .............................. 1 -Methyl-2-isopropylidenecyclohexane. ......................... 1-Methyl-3-iaopropylidenecyclohexane . ......................... 1-Methyl-4-isopropylidenecyclohexane. .........................
~
DOUBLE-BOND INCLEMENT IN BOILING POINT
'C.
13 (trans) 6 (cis) 10 6 .O (trans) -0.5 (cis) 7 7 2 (trans) -4 (cis) -5 (?) 13 (trans) 7 (cis) 8 3 7 (trans) 5 (cis) 2 -10
6 11 (trans) 4 (cis) 2
5
TABLE 12 Dimelhylcyclohezenes COYPOVND
IIPE
1,2-Dimethyl-l-cyclohexene. ...................... 1,3-Dirnethyl-l-cyclohexene. ...................... 1,4-Dirnethyl-l-cyclohexene. ...................... 1,5-Dimethyl-l-cyclohexene, ...................... 3,5-Dimethyl-l-cyclohexene.. . . . . . . . . . . . . . . . . . . . , I 4,4-Dimethyl-l-cyclohexene.. . . . . . . . . . . . . . . . . . . . . .I
V IV IV IV I1
i
BOILING POINT
'C
,
~
136 128.0-128.4 127.5 127 124-126 120-122
I1
TrlBLE 13 A Zkenylcyclenes COMPOUND
I
I
BOILING POINT
"C.
1-Methyl-2-isopropenyl-1-cyclopentene ................... 3-Methyl-4-isopropenyl-1-cyclopentene. . . . . . . . . . . . . . . . . .
155-157 143-145 at 770 mm.
1-Vinyl-1-cyclohexene .................................. 4-Vinyl-1-cyclohexene ..................................
143-145 129.5-130.5
I
I
4-Methyl-1-isopropenyl-1-cyclohexene.. ................ , 4-Methyl-2-isopropenyl-1-cyclohexene ................. 3-Methyl-l-isopropenyl-l-cyclohexene . . . . . . . . . . . . . . . . . . , . 1-Methyl-2-isopropenyl-l-cyclohexene . . . . . . . . . . . . . . . . . . . .i 3-Methyl-5-isopropenyl-l-cyclohexene . . . . . . . . . . . . . . . . . . . 3-Methyl-6-isopropenyl-l-cyclohexene . . . . . . . . . . . . . . . . . . . 2-Methyl-3-isopropenyl-l-cyclohexene . , . . 4-Methyl-5-isopropenyl-l-cyclohexene . . . . . . . . . . . . . . . . . . . .
184-185 181-182 181-182 177 at 755 mm. 175-176 172-174 170-171 at 765 mm. 170
T A B L E 14 Effect of triple bonds on boiling point COMPOUND
BOILING POINT
"C.
Ethynylcyclopentane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...................................
107-109 103.4
1-Cyclopentyl-1-propyne ................................. 3-Cyolopentyl-1-propyne. ................................ Propylcyclopentane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
142-143 132.5-133.5 130.8
1-Cyclopentyl-2-butyne.. .. Butylcyclopentane. . . . . . . . . . . . . . . . . . .
164-165 157 130-132 131.8
1-Cyclohexyl-1-propyne. ................................. 3-Cyclohexyl-1-propyne.. ... Propylcyclohexme............................. ,
162-164 157 154.7
Cycloheptyne............................ Cycloheptane.............. ....................
120-121 117-117.3
BOILING POINTS OF MONOCYCLIC HYDROCARBONS
945
in a side chain always raises the b i g point (sometimes as much as 15OC.) over that of any isomeric non-conjugated alkenylcyclene (examples in table 13). Conjugation of double bonds one of which is cyclic and other semicyclic, or both of which are cyclic, does not always raise the W i g point; e.g., 1,3-cyclohexadiene boils about 4OC. lower than 1,4-cyclohexadiene. I n the few cases known, introduction of a triple bond into either a side chain or a ring raises the boiling point, as shown in table 14. The data in the case of ethynylcyclohexane are queationable. V. SUMMARY
Branching of a chain on an alkylcyclane or alkylcyclene lowers its boiling point. In isomeric alkylcyclanes containing the m e ring the boiling point is lowered by increasing the number of side chains. Among isomeric dialkylcyclanes differing only in position of the alkyl groups the 1,Zdialkyl isomer has the highest boiling point and the 1,1-dialkyl isomer the lowest. Cis compounds boil as much as 7.5OC. higher than the corresponding trans isomers. A Type I double bond lowers the boiling point. A Type I1 double bond also lowers the boiling point except in cyclohexenes, where it raises the boiling point. Type I11 alkenylcyclanes boil slightly above the parent alkylcyclanes. Double bonds of Types IV and V cause boiling points above those of the corresponding dkylcyclanes. The boiling points of isomeric alkylcyclenes differing only in the type of double bonds increase as the type number increases. Conjugation of double bonds consistently raises the boiling point only if one of the bonds is cyclic and the other is in the a-position in the side chain. Introduction of a triple bond into a saturated alicyclic hydrocarbon raises its boiling point. REFERENCES (1) Boom, C. E.: In The Sn'ence of Petroleum, pp. 1349-56. Oxford University Press* London (1938). (2) CBANE,G.: Dissertation, The Ohio State University, 1941. (3) EQLOFF,G.: Physical Cornfanfa of Hydrocarbons, Vol. 11. Reinhold Publishing Corporation, New York (1940). (4) EQLOFF,G., AND KUDER,R. C.: Paper presented at the lOlst Meeting of the American Chemical Society, which waa held at St. Louis, Missouri, April, 1941. (5) EGLOFF, G., SHERMAN, J., AND DULL,R. B . : J. Phys. Chem. 44, 730-45 (1940). (6) KAWFXANN, H. : Beriehungen rwischen physikalischen Eigenschaften und chemiseher Konstitutim, pp. 170-1. Ferdinand Enke, Stuttgart (1920). (7) PLATE,A. F.: Compt. rend. U.R.S.S. !U, 257-62 (1939); Chem. Abstracts S4,994 (1940). (8) SMILEE, S.: The Relations between Chemical Constitution and Some Physical Properties, p. 229. Longmans, Green, and Company, London (1910).
