[CONTRIBUTIONS No. 60
AND
61 FROY
THE
CHEMICALLABORATORY OF
THE
UNIVERSITY OF UTAH]
A SYSTEM CORRELATING MOLECULAR STRUCTURE OF ORGANIC COMPOUNDS WITH THEIR BOILING POINTS CORLISS R. K I N N E P Received October 81, 1940 IV. FUSED POLYCYCLIC AROMATIC HYDROCARBONS
The boiling points of the polycyclic aromatic hydrocarbons, including their aliphatic derivatives, may be calculated using the boiling point equation (l),the boiling point numbers given in Parts I1 (2) and I11 (3), and two or three additional boiling point numbers characteristic of the various combinations of these rings. Using these b.p.n's. it is possible to calculate the boiling points of 84.7% of the known hydrocarbons in these classes to within &lo0, the average deviation being +0.34'. The additional b.p.n. characteristic of an aliphatic ring, either saturated or unsaturated, fused to an aromatic ring is 1.5. The boiling point of naphthalene may now be calculated very satisfactorily using the following structure. CH
Phenylene radical.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon in the alicyclic portion .................... Hydrogen in the alicyclic portion.. ................................ Double bonds, 2 of the type RCH=CHR.. . . . . . . . . . . . . . . . . . . . . . . . . Conjugation of the double bonds., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Phenyl attached to double bonds (2 X 1.0). ....................... Six membered alicyclic ring.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alicyclic ring fused t o benzene.. . . ...........................
...................................... Calculated B.P., ......................... ...... ............................................
18.O 3.2 4 .O 3.8 0.8 2.0 2.7 1.5
218.0"
In calculating the boiling point of derivatives of naphthalene the B.P.N. of naphthalene (36.0) is lowered one unit for each hydrogen displaced and the b.p.n. of the group introduced added in. From the B.P.N. thus obtained for the molecule the boiling point is calculated by use of the 220
221
STRUCTURE AND BOILING POINTS
boiling point equation or more easily from the data in Table I1 in Part I1 (2). The position taken by the substituent in naphthalene should, in general, make only a small difference in the boiling point and the @-substitutionproducts would be expected to have the higher boiling point. This is borne out by a comparison of the known boiling points of seven pairs of a,p-substitution-products. In four of the seven cases the @-isomer is higher-boiling, although one of these is only half a degree higher, in two cases the a is higher-boiling and in one case the two isomers have the same recorded boiling point. In view of the latter irregularities it would appear that the boiling points of these isomers should be redetermined carefully, especially the ethyl and isoamyl derivatives, the @-isomersof which have unusually low observed boiling points. The calculation of the boiling points of a- and @-phenylnaphthalene involves the exaltation of the boiling point caused by attachment of two aryl groups, for which in diphenyl a b.p.n. of 2.5 gave Sstisfactory results. With the phenylnaphthalenes this value gives a calculated boiling point midway between the observed boiling points of the a- and @-isomers,which may be considered satisfactory for the present.
.................
35.0
19.0 ...................... ond.. ................. 2.5
.......... Calculated B.P.. ................................................. Observed B.P. a-isomer ................................................... 8-isomer ......................
56.5 340.1" 334.0"
345.5"
The boiling point of @,pi-bmaphthylof 452' requires a b.p.n. of 10.0 for the union of two naphthyl groups in the p-position. This is an unusually high exaltation but is of the same order of size as that for pterphenyl which required a b.p.n. of 9.0. The boiling points of other aromatic polycyclic hydrocarbons containing aliphatic rings may be calculated using the b.p.n. of 1.5 for the fusing of the alicyclic ring to the aromatic. These calculations are given in Table I. For those hydrocarbons in which rings are formed by linking aryl groups by single bonds or unsubstituted carbon chains the appropriate b.p.n. must be included for those factors [see Part I11 (3)]. Fluorene, 9,lOdihydroanthracene, and 9 , lodihydrophenanthrene are examples of this class. A comparison of the boiling points of the polycyclic aromatic hydrocarbons containing only aromatic nuclei shows a marked difference between naphthalene and the higher members. This is shown by the difference in B.P.N's. for these hydrocarbons. The B.P.N. of naphthalene
222
CORLISS R. KINNEY
hm been calculated to be 36.0 of which 18.0 units were due to the introduction of the second ring. To account satisfactorily for the boiling points of the higher members of this series containing three or more aromatic rings, a b.p.n. of 23.0 must be added for each additional ring introduced beginning with naphthalene. Since B.P.N’s. may be compared directly this indicates a marked alteration in the difference between the B.P.N’s. of benzene and naphthalene as compared with the difference between the B.P.N’s. of the higher members of the series. These differTHE CALCULATED AND
TABLE I OBSERVEDBOILINGPOINTS OF THE FUSED POLYCYCLIC AROMATIC HYDROCARBONS B.P.N. (CAIC’D)
HYDBOCABBON
Indane . . . . . . . . Indene. . . , . . . Tetralin . . . . . . , Tetrahydroacenaphthene , . . . . . , Acenaphthene Acenaphthylene . . . , . . . . Fluorene, . . , . 9,lO-Dihydroanthracene. 9,lO-Dihydrophenanthrene. , . . . . , Anthracene. . Phenanthrene Chrysene.. . . . Picene , . . . . . .
18+ 2.5+ 2.5 18 3.2 18
+
+
+
34 36
+ +
+
+ +
+
17 34+
2.5+ 4 4 - 2.5 1.9 8 2.7 6+
+ + +
+
+
41.0 250.6254.0 4-3.4 43.6 267.0277.5 i-10.5
2 f 2.5 1.9 2.0 1.5 2 f 2 . 5 + 2 . 5 + 1 . 8 + 1.5
45.5278.6270.0 -8.6 47.1 288.1295.0 f 6 . 9
+ 1.8 + 1 . 5
49.4301.4305.0 f 3 . 6
5.2 2.5+
+
36+
1.6+ 4 +
36+ 34 34 32 32
1.6
+
+ 1.0 +
3.0 1.5
4.8 11 l.6+ 4 + 1.6 0.8
+
--1.5 = 30.5 175.3 176.5 f 1 . 2 1.5 31.3 182.3182.4 f 0 . l 1.5 33.4 198.1 206.4 $8.4
2.7 f 1.8
+
4 f 2.7 + 2 . 5 + 1.8
+ 23 + 23 + 23 + 23 + 23 + 23 + 23
+
+ 1.5
50.1305.4313.0 57.0 342.7342.3 57.0 342.7 340.0 78.0 440.3 448.0 99,0521.7520.0
f7.6 -0.4 -2.7 f7.7 -1.7
ences indicate a marked change in the structure of the higher aromatic hydrocarbons as compared with that of naphthalene. In calculating the boiling points of the higher members, the B.P.N. of naphthalene may be considered to be the fundamental unit which is altered by the introduction of additional aromatic rings, the amount of change being represented by 23.0 units instead of 18.0. In calculating the B.P.N’s. of the higher members, the B.P.N. of the naphthalene nucleus is lowered two units for the two hydrogen atoms displaced by each additional aromatic ring introduced. Calculations of the boiling points of the four hydrocarbons whose boiling points have been determined (anthracene, phenanthrene, chrysene, and picene) appear in Table I.
223
STRUCTURE AND BOILING POINTS
The B.P.X"s. of the alkyl derivatives of the parent hydrocarbons given in Table I may be calculated from the B.P.N's. of the parent hydrocarbon by lowering the B.P.N. one unit for each hydrogen atom displaced and adding the normal b.p.n. of the group introduced. The boiling point is then obtained in the usual way from the B.P.N. of the molecule. The boiling point of retene, 1-methyl-7-isopropyl phenanthrene, may be calculated as an example. Phenanthrene, less two hydrogen atoms. ..........................
55 .O
Isopropyl .........................................................
8.65 67.45 393.8" 394.0'
............................... Calculated B.P.. ................................................. Observed B.P.. ...................................................
The hydrocarbons of the types included in this paper whose boiling points differ from the calculated by more than f l O ' are given in Table 11. TABLE I1 THECALCULATED AND OBSERVED BOILINGPOINTS O F THOSE HYDROCARBONS WHO6E OBSERVED BOILINGPOINTS DEVIATEFROM THE CALCULATED BY f 10"
I
HYDROCAEBON
1,4-Dimethy1-6-ethyl naphthalene. . . . . . . 2-(3-Methylbutyl)naphthalene. . . . . . . I-Methylindane.. . . . . 2-Methylindane .. . . . 2-Methylindene . . . . . 1,4-Dihydronaphtha. lene. . . . . . . . . . . . . . . Acenaphthene . . . . . . . Hexahydrofluorene . . 9-Methylfluorene. . . .
B.P.N.
(CALC'D)
+ 7.6 + 6 . 6 = 47.2 35 + 11.2 + 3.05 49.25 18 + 9.9 + 3.8 + 1.5 33.2 18 + 9.9 i3.8 + 1 . 5 33.2 18 + 7.9 + 3.8 f 3 . 3 f 1.5 34.5 1.9 + 1.5 33.3 18 + 11.9 + 3 4 + 8.1 + 1.5 43.6 3.0 41.8 18 + 22.3 + .I 36 + 4.3 + 3.8 + 5.0 49.1 33
288.7300.0+11.3 300.6290.0 -10.6 196.6182.5 -14.1 196.6 184.0 -12.6 206.2184.5-21.7 197.4212.0 +14.6 267.0277.5+10.5 255.7245.0 -10.7 1299.71320.01+20.3
Many of these boiling points appear to be incorrect when compared with the boiling points of similarly constituted hydrocarbons and should be redetermined. On the other hand, it is possible that some of these hydrocarbons need additional b.p.n's. to account for the boiling point given by a particular structure. Acenaphthene is one of these. The recorded boiling point is 10.5' higher than the Calculated, and if this boiling point is correct an additional b.p.n. should be included to account for the higher boiling point given by the acenaphthene structure. However, the observed boiling point of the similarly constituted acenaphthylene is 8.6" lower than the calculated, but possibly is low because the substance decomposes slowly at the boiling point.
224
CORLISS R. KINNEY V. ALIPHATIC POLYCYCLIC HYDROCARBONS
The calculation of the boiling points of the aliphatic polycyclic hydrocarbons may be made using the b.p.n's. obtained for the simple alicyclic hydrocarbons (2) and the following additional b.p.n's. which account for the various combinations of the rings. The effect upon the boiling point is, in many cases, similar to that of the analogously constituted aromatic polycyclic hydrocarbons, Part IV, and emphasizes the important effect of molecular configuration on the boiling point of compounds. When two alicyclic rings are attached by a single bond or to the ends of an unsubstituted carbon chain a b.p.n. of 1.5 should be added in obtaining the B.P.N. for the molecule. The presence of alkyl groups on the chain between the rings destroys the effect and the b.p.n. should not be used for these derivatives. This difference is shown by the boiling points of the following related hydrocarbons. 1.8-DICYcLOHEXTLPBOPANE
Cyclohexyl groups. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon in the aliphatic chain. ..................... Hydrogen in the aliphatic chain.. . . . . . . . . . . . . . . . . . . Methyl group... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Two rings at the end of an unsubstituted chain.. . . . Calculated B.P.N.................................. Calculated B . P . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Observed B . P . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37.0 2.4 6.0 1.5 46.9 286.9' 289.5"
1, ~-DICTCLOHEXYL2-YETHYZPBOPANE
37.0 2.4 5.0 3.05 47.45 290.1' 291.0"
The boiling points of only two spirobicyclic hydrocarbons were found in the literature. They were spiro4,5decane and s-spirohendecane. By using a b.p.n. of 0.5 for the spiro configuration the calculated boiling points fall within a few tenths of a degree of the observed. The boiling points of the various fused bi- and tri-cyclic hydrocarbons are calculated in the same general way as those of the monocyclic hydrocarbons described in Part I1 (2) with the additional rules that all alkyl radicals attached to the rings be assigned the branched chain b.p.n's. and that a b.p.n. of 0.5 be added to the B.P.N. of those derivatives in which there are no carbon atoms between the points of attachment of the rings and 0.5 subtracted from the B.P.N. of those in which there are carbon atoms between the points of attachment. The difference is probably due to the greater symmetry of the former class of compound. By way of example, carene, 3 7,7-trimethylbicyclo [4,1,O]hept-3-ene, which does not have a carbon atom between the points of attachment, has a higher boilingpoint by 13.7" than the isomeric pinene, 2,7,7-trimethylbicyclo[3,1,l]hept-2ene. The addition of 0.5 to the B.P.N. of the former compound and the substraction of 0.5 from the latter accounts for the difference fairly well. These boiling points are calculated as follows.
CABENBI
I
PINBINBI
5.6 7 Carbons in rings. . . . . . . . . . . . . . . . 5.6 7.0 7 Hydrogens attached to rings, . . . 7.0 9.15 3 Methyl radicals.. . . . . . . . . . . . . . . . 9.15 1 3-membered ring., . . . . . . . . . . . . . . 2.1 2.3 14-membered ring.. . . . . . . . . . . . . . . 2.7 1 6-membered ring.. . . . . . . . . . . . . . . 2.7 2.3 1 Double bond, type R2C = CHR, 2.3 A carbon atom between the points S o carbon atom between the points of attachment of the rings.. . . . .-0.5 of attachment of the rings, . . , . . $0.5 28.55 Calculated B.P.N.. . . . . . . . . . . . . . . . 29.35 160.4" Calculated B.P.. . . . . . . . . . . . . . . . . .,166.9"
HYDROCARBON
Tricyclo[4,3,0, i e 4 -
deca-2,7diene (dicyclopen tadiene) . , . Tricyclo[4,3,0,4'9']tridecane (dodecahydrofluorene) .Decahydrofluorene. , . . Octahydrofluorene. . . . 'Tricyclo[4,4,0,4a*'Itetradecane (tetradecahydrophenanthrene) . . Tricyclo[4,4,0,4',']tedradecene (-1) (dodec ahydrophen anthrene. . . Tricyclo[4,4,0,4'8']tetradecadiene(?) (decahydrophenanthrene). ...
8.0+12+2.5+2.5+2.5+3.8-0.5=30.8
10.4
+ 22 + 2.7 + 2.5 + 2.7 +
1.0
178.4170.0-8.4
41.3 252.5253.0 $0.5
10.4+20+2.7+2.5+2.7+2.8+1.0
42.1 257.6258.0+0.4
10.4+18+2.7+2.5+2.7+6.4+1.0
43.7 267.6273.5+5.9
11.2
+ 24 + 2.7 + 2.7 + 2.7 +
11.2
+ 22 + 2.7 + 2.7 + 2.7 + 1.9 + 1.0
44.2 270.7268.5-2.2
11.2
+ u) + 2.7 + 2.7 + 2.7 + 5.5 + 1.0
41.3
225
1.0
44.3 271.3272.5+0.8
226
CORLISS R. KINNEY
The fused tricyclic hydrocarbons (so-called) may be divided into two classes, those which are actually tricyclic and those which are tetracyclic. The latter hydrocarbons contain a bicyclic ring system with an additional bridge or bond from the outside of one ring to the outside of the other. Apocyclene, tricyclene, and adamantane are examples. The calculation of the boiling points of the true tricyclic hydrocarbons (excluding the spiro derivatives) may be accomplished using the same b.p.n's. as for bicyclic derivatives. The boiling points of seven hydrocarbons were obtained from the literature and all were well within f l O o of the calculated boiling point. Calculations for these hydrocarbons are given in Table I. TABLE I1 THECALCULATED AND OBSERVED BOILING POINTSOF THE FUSEDALIPHATIC TRICYCLIC FOURRINGS HYDROCARBONS CONTAINING B.P.
B.P.N.
XTDEOCABBOX
DDVI-
(OB- ATION,
(CAIC'D)
B'D)
'c.
--
7,7-Dimethyltricyclo[2,2,1,o*4heptane (apo, 136.2 .38.5 +O.S cyclene). . . . 5 . 6 + 8 + 6 . 1 + 2 . 5 + 2 . 5 + 2 . 5 - 1 . 5 = 2 5 . 7 l17,7-Trimethyltricyclo[2,2,1,0'86 heptane (tri1 . 5 27.75153.7 .53.0 -0.7 cyclene) . . . . 5 . 6 + 7 + 9 . 1 5 + 2 . 5 + 2 . 5 + 2 . 5 4,7,7-Trimethyltricyclo [2,2,1,02 -8 heptane... . . 5.6 7 9.15 2 . 5 2 . 5 2 . 5 - 1 . 5 27.75153.7 5 0 . 5 -3.2
+ +
+
+
+
The boiling points of the tricyclic hydrocarbons which actually contain four rings are calculated on the basis of the three largest rings in the molecule using the same b.p.n's. as for the true tricyclic hydrocarbons. The boiling points of only three hydrocarbons were obtained from the literature, but all of these are close to the calculated. The calculations for these compounds appear in Table 11. A very interesting hydrocarbon, adamantane, has been obtained from a petroleum fraction boiling from 190" to 195". This substance has a melting point in a sealed tube of 268", but apparently has a vapor pressure equal to 760 111111. at a much lower temperature. Because of the high melting point and other properties the substance was given the highly symmetrical structure
STRUCTURE AND BOILING POINTS
227
CH
If the boiling point of this structure is calculated on the basis of three rings as before we obtain a value which is too low, but on the basis of four rings the boiling point obtained coincides with the boiling point of the petroleum fraction from which the compound was taken. 10 Carbon atoms.. . . . . . . . . . . . . . . . . . 8.0 8.0 16.0 16 Hydrogen atoms. . . . . . . . . . . . . . . . 16.0 3 6-membered rings. . . . . . . . . . . . . . . . 8.1 4 6-membered rings. . . . . . . . . . . . . . 10.8 4 Rings containing carbon atoms 3 Rings containing carbon atoms between the points of attachbetween the points of attachment. . . . . . . . . . . . . . . . . . . . . . . . . . -2.0 ment . . . . . . . . . . . . . . . . . . . . . . . . . . . -1.5 Calculated B.P.N.. . . . . . . . . . . . . . . . . 30.6 32.8 Calculated B.P.. . . . . . . . . . . . . . . . . . . ,176.9' 193 7" I
[n view of the high symmetry of the molecule it may be desirable to calculate the boiling points of such molecules using b.p.n's. for all four rings in the molecule or even possibly an additional b.p.n. as it is possible that the temperature at which the vapor pressure of the molecule reaches 760 mm. is higher than that indicated by the boiling range of the petroleum fraction. The question can best be settled by the synthesis of this hydrocarbon and the determination of its boiling point. The boiling point of one spiro tricyclic hydrocarbon appears in the literature, that of 6,6-tetramethylenebicyclo[3,l ,O]hexane. The boiling point may be calculated using the boiling point number of 0.5 for the spiro configuration. 10 Carbon atoms.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Hydrogen atoms ........................ 2 5-membered rings.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-membered ring.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Two rings containing carbon atoms between the points of attachment. 0.5 Spiro configuration of the third ring.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 Calculated B.P.N. ....................... 32.1 Calculated B.P.. . . . . . . . . . . . . . . 188.4" Observed B.P.. . . . . . . . . . . . . 189.5"
228
CORLISS R. RINNEY SUMMARIES IV
B.p.n's. have been obtained to account for the boiling points of the polycyclic aromatic hydrocarbons. For 84.7%, the observed boiling points deviate from the calculated by less than &loo. The average deviation is +0.34'. V
The boiling points of the polycyclic aliphatic hydrocarbons may be calculated using the b.p.n's. of the simple alicyclic hydrocarbons together with additional b.p.n's. characteristic of the various combinations of rings. The boiling points of a total of 78 aliphatic polycyclic hydrocarbons have been calculated and compared with the observed values. The deviation of 91.1% is less than =tlO'. The average deviation is -0.34'. SALTLAKECITY, UTAH.
REFERENCES (1) KINNEY,J . Am. Chem. SOC.,60,3032 (1938). (2) KINNEY,Ind. Eng. Chem., 32,559 (1940). (3) KINNEY,Ind. Eng. Chem., in press.
