2482
JOHN
M. DERFER, EDWARD E. PICKETT AND CECILE. BOORD
Vol. 71
A F 13200 - 33.6Tcal./mole AH = 13200 cal./mole A S = 33.6 cal./mole-deg.
expected t o affect the electron density around the two ring nitrogen atoms unequally. Therefore, i t cannot be assumed that AH12 in these cases During these observations it is believed that represents the strength of a single hydrogen bond the temperature measurements were in error but that it is rather the arithmetic average of the by no more than 0.2' K. The sickle gage em- two unequal hydrogen bonds. ployed possessed sufficient sensitivity so that a Compared to the 0-H. . . 0 bonds measured pressure differential of 0.5 mm. could be readily by other worker^,^^^^' the 0-H.. . N bonds detected. The mercury manometer was observed measured in the present work are quite strong. to the nearest 0.1 mm. by the use of a catheIt was desired to study further the effect of tometer. substituents on the strengths of the hydrogen Discussion bonds by measuring the dissociation pressures The reaction for which the thermodynamic of some symmetrically 1,lO-phenanthrolines. quantities have been measured is the removal of a Upon searching for compounds of this class only molecule of water from a molecule of 1,lO- the 5,6-dimethyl derivative was available, but phenanthroline monohydrate, two hydrogen bonds contrary to expectations no hydrate could be being broken in the process. Accordingly values obtained. Perhaps this is due to the extraordiof 14.5, 13.0 and 13.2 cal./mole were obtained for narily high melting point of this compound (272' AH of the hydrates of 1,lO-phenanthroline, the compared to 114' for the anhydrous 5-methyl 5-bromo and the 5-methyl derivatives, respec- compound and 117' for anhydrous 1,lO-phentively. Since the nitrogen atoms in 1,lO-phen- anthroline) . anthroline are equivalent, the value of " / 2 , Acknowledgment.-The authors wish.to thank 7.25 cal./mole, may be considered as representing the G. Frederick Smith Chemical Co. for the loan the strength of one hydrogen bond.1° The pres- of the 1,lO-phenanthroline chemicals, and Mr. ence of a substituent in the 5 position would be Paul Anders who fabricated the glass apparatus employed in this investigation. (10) It is necessary t o consider t h e error introduced by t h e possible change of t h e crystal energies of the solid phases due t o the removal Summary of t h e water molecule. According t o Wenner (Wenner, "Thermochemical Calculations,'' McGraw-Hill Book Company, Inc., New 1. The dissociation pressures a t various temYork, N. Y., 1941, pp. 23-25) the following empirical rule is followed peratures for several 1,lO-phenanthroline monoby organic compounds: hydrates have been measured. From the data AHi/T, = 9 to 11 the thermodynamic quantities K , A F , AH and A S Where A H f is the molar heat of fusion in calories and Tm the absohave been evaluated. lute temperature of t h e melting point. Choosing an average value 2 . The value of the hydrogen bond in 1 , l O of 10 for t h e constant we estimate AHf for 1,lO-phenanthroline monohydrate a t 3730 cal./g. mole and for t h e anhydrous material a t phenanthroline monohydrate was found to be 3900 calories/g. mole. T h e value of AHf is 200 cal./g. mole or co. 7.15 cal.!g. mole. 100 cal./g. mole per bond. When this small correction is applied t h e value for each hydrogen bond becomes 7.15 cal./mole
[CONTRIBUTION FROM THE
DEPARTMENT OF
RECEIVED MARCH 18, 1949
CHEMISTRY AT THE O H I O STATE UNIVERSITY]
Infrared Absorption Spectra of Some Cyclopropane and Cyclobutane Hydrocarbons BY JOHN M. DERFER, EDWARD E. PICKETT' AND CECILE. BOORD The infrared absorption spectra of cyclopropane and cyclobutane have been determined many times and detailed theoretical analyses of these spectra have been carried out.2 To date the infrared spectra of only four alkylsubstituted cyclopropanes have been described in the literature. Lankelma3 and co-workers have published the spectra of 1,1,2-trimethyland 1,2 - dimethyl - 3 - ethylcyclopropane. The (1) Present address: Department of Agricultural Chemistry, University of Missouri, Columbia, Missouri. (2) (a) King, THISJOURNAL,68, 1580 (1936), (b) Linnett, J . Chcm. Phys., 6, 692 (1938); (c) Saksena. Pmc. I n d . A c a d . Sci., 108, 449 (1939); (d) Wilson, J . Chem. P h y s . , 11, 369 (1943); (e) see also Bonner, i b i d . , I , 704 (1937); Eyster, i b i d . , 6 , 576 (1938). (3) Bartleson, Burk and Lankelma, TIIIS J O U R N A L , 68, 2513 (1946).
spectra of and 1,l-dimethylcyclopropane6 also have been published recently; a tentative assignment of frequencies was presented for the latter. A theoretical analysis of the infrared absorption spectra. of 1-methylcyclobutene and methylenecyclobutane has also been carried out6; no spectra of other hydrocarbons of the cyclobutane series have been described. The paucity of published spectra of substituted cyclopropanes and cyclobutanes is due chiefly to the fact that hydrocarbons of these types are relatively rare and have seldom been synthesized in quantities sufficient to allow a high degree of (4) Condon and Smith, i b i d . , 69, 965 (1947). (5) Cleveland, Murray and Gallaway, J . Ckem Phys., 16, 742 (1947).
July, 1949
2483 INFRARED SPECTRA OF S O M E CYCLOPROPANE AND CYCLOBUTANE HYDROCARBONS
purification. Reliable infrared spectra of such compounds would be an invaluable aid to workers in this field, since even small quantities of an impure hydrocarbon might then suffice for identification. The present paper presents infrared absorption spectra of fourteen individual cyclopropane hydrocarbons and seven individual cyclobutane hydrocarbons ; the experimental samples, with two exceptions, were available in amounts which permitted obtaining materials of a high degree of purity. These spectrograms not only characterize the compounds for which they were determined, but may be of use in distinguishing between a 3 - and 4-membered ring when the presence of one or the other is reasonably expected. No detailed theoretical analysis of any of these spectra has been attempted.
TABLE I
SPECTROGRAMS
No.
Hydrocarbon
Cyclopropanes 1 Ethyl2 Isopropyl3 Isopropenyl1 1,l-Dimethyl5 1,l-Diethyl6 l-htethyl-l-ethyl7 1-Methyl-2 -ethyl-'I 8 1-Methyl-1-isopropyl9 1-Ethyl-1-butyl10 l-Methyl-2-n-propyl-" 11 1,1,2-Trimethyl12 1,1,2,2-Tetramethyl13 1 , 2 , 3 - T r i m e t h ~ l - ~ 14 1,2-Dimethyl-3-ethyl-"
Estimated minimum punty mole yo
99 90 99 97 99 99 97 97 97 97 99 99 95 90
State
Cell length, mm.
Pressure, mm.
\.apor \'apor Vapor \.apor Liq. \.apor Yapor Liq. Liq. Liq. Vapor Yapor Liq. Liq.
100 100 100 100 0.09 80 100 0.025 0.09 0.025 100 100 0.025 0.025
100 150 120 140
... 250 400
... ... ... 100
90 Experimental ... Instrumentation.-The infrared spectra were .. obtained b y means of the Beckman IR-2 specCyclobutanes trophotometer. This instrument, thermostated 98 Yapor 100 105 a t 25 * l o , was calibrated to within 0.03 p 15 Methylby means of the spectra of water, carbon dioxide 16 Ethyl99 Yapor 100 120 and ammonia. The transmissions of the sample 17 Ethylidene99 Vapor 100 90 and sample cell were measured directly, without 18 Isopropyl99 Liq. 0.025 . . . 99 Liq. 0,025 . . . comparison with an empty cell, for the purposes 19 Isopropylideneof the present qualitative study. The spectra 20 n-Butyl98 Liq. 0.025 . . represent a combination of the data obtained from 21 %-Amyl97 Liq. 0.025 . . . recorder tracings and from point-by-point per cent. trans isomer. cis-lvans-cis isomer. cis-cis-cis isotransmission measurements. It was not con- mer. venient to determine the spectra of all of the having a peak between 9.8 and 10.0 p. An absamples in the same physical state because of the sorption band is also prominent in this region in wide differences in their boiling points. the spectrum of methylcyclopropane recently Samples.-Samples numbered 4, 6, 8, 15, 16, p ~ b l i s h e d . ~Examination of about 300 spectro17, 18 and 19 (see Table I) were obtained from grams'O of hydrocarbons of other types showed materials previously described by two of the that strong absorption bands occur in this region present authors6 Numbers 1, 2 and 3 were premore often than would be expected on an acpared by Ross Van Volkenburgh'; Numbers no cidental basis. It appears from our study that 3 and 9 by R. W. Shortridges; Numbers 7, 10, 11, this band, centered a t about 9.9 p (1010 cm.-'), 12, 13 and 14 by R. G. Kelso; Numbers 20 and is characteristic the cyclopropane ring and that 21 by R. C. Krug. Thanks are due to the labora- it should prove ofuseful in the qualitative identitories of the National hdvisory Committee for fication of this ring where its presence may reasonAeronautics which furnished a high-purity sample ably be expected. of methylcyclobutane for checking purposes. The spectrum of cyclopropane i t s e l f 2 a ~ shows b~c~ Forthcoming publications will give the details of a prominent band a t about 1040 cm.-' (9.61 p ) . the synthesis of those products whose preparations LinnettZbassigned a band a t 1051 cm.-l to a mode have not already been r e p ~ r t e d . ~ of vibration in which a methylene group rocks back and forth through the plane of the ring, and Discussion Cyclopropane Derivatives.-The spectra of all another a t 1022 cm.-' to a wagging of methylene the cyclopropane derivatives presented in Fig. 1 groups in the plane of the ring. Two ring def(Nos. 1 to 14) show a strong absorption band ormation frequencies were assigned to absorp.tions a t 1187 cm.-' (8.43 p) and 860 cm.-l (6) Derfer, Greenlee and Boord, T H I S J O U R N A L , 71, 176 (1949). (11.63 p). (7) Van Volkenburgh, Greenlee, Derfer and Boord, i b i d . , 71, 173 It will be noted, however, that the spectra of (1949). ( 8 ) Shortridge, Craig, Greenlee, Derfer and Boord, ibid., 70, the various samples of lI2-dimethyl-3-ethyl946 (1948). cyclopropane prepared by Lankelma, et u Z . , ~ as (9) In t h e four cases where geometrical isomerism is possible, the well as our own, Fig. 1 (No. 14) and also our 1,2,3spectrum of Only one isomer (that obtained in the highest purity) ,
,
(i
has been given; since t h e spectra determined for the other isomers are very similar and less reliable in each case, little would be gained by their inclusion.
110) "Selected Infrared Absorption Spectrograms." The American Petroleum Institute Research Project 44 a t the National Bureau of Standards.
2181
JOHN
M.DERFER,EDWARD E. PICKETT AND CECILE. BOORD
Vol. i l
Wave numbers in cm.-’. 100
80
60 40 20
0 60 40 20
0 60 40 20 >?
0
.d2
60
.I
32
40
b 20 I
0
2
4 6 8 10 12 1 4 2 4 6 8 10 12 14 Wave length, microns. Fig. 1.--Infrared absorption spectra of certain cyclopropane and cyclobutdne hydrocarbons (see Table I). 4
6
8
10
12
142
trimethylcpclopropane, Fig. 1 (No. I:
