SPECTRAOF CYCLOPENTAMETHYLENEDIALKYLSILANES
May 5, 1957 TABLE I
HEATCAPACITIES (CAL./DEG.-MOLE) T , OK.
Cp
54.01 58.57 62.80 67.29 71.81 76.33 80.98 85.79 95.40 105.04
1.659 2.025 2.380 2.770 3.165 3.555 3.955 4.355 5.110 5.808
53.65 56.69 57.89 61.01 65.62 70.32 74.88 82.19 86.30 94.60 104.82
1.774 2.013 2.110 2.380 2.782 3.206 3.623 4.304 4.685 5.463 6.404
53.66 57.94 62.32 66.53
T,O K . CD T,OK. NaF (mol. wt., 41.991) 114.61 124.46 135.98 145.74 155.77 165.84 175.84 186.05 195.79 205.89
6.434 7.007 7.606 8.060 8.460 8.815 9.124 9.413 9.650 9.882
CP
216.14 10.08 225.80 10.27 10.44 235.96 245.66 10.57 256.40 10.73 266.20 10.91 10.97 276.20 287.15 11.09 295.86 11.17 298.15 (11.19)
AlFs (mol. wt., 83.98) 114.53 7.268 215.91 14.48 124.39 8.131 226.20 15.02 135.56 9.077 235.93 15.50 145.35 9.879 245.55 15.92 155.75 10.68 256.18 16.39 165.58 11.38 266.31 16.80 175.81 12.08 276.22 17.19 185.93 12.75 286.59 17.54 195.84 13.35 296.10 17.88 206.14 13.93 298.15 (17.95)
NaaAlFa (mol. 10.10 114.69 11.39 124.69 12.76 136.00 14.13 145.51
wt., 209.953) 27.62 216.05 29.95 226.06 32.37 236.20 34.35 245.81
[CONTRIBUTION FROM
44.67 45.70 46.70 47.63
THE
70.94 75.55 80.79 84.45 94.77 105.20
15.54 17.00 18.55 19.61 22.46 25.24
155.82 165.66 175.91 185.85 195.95 206.18
36.27 37.91 39.50 40.90 42.25 43.58
2057
256.33 48.53 266.23 49.30 276.24 50.02 286.47 50.76 296.00 51.49 298.15 (51.60)
The curves were extrapolated below 51°K. by means of the following Debye and Einstein function sums, which fit the measured data within the limits of temperature and percentage of the heat capacity shown below
+ 4E(236/T) + 5E(568/T) (51-29S°K., 1.7%) NaF: D(340/T) + E(391/T) (51-115OK., 0.270) A1Fa: D(326/T) + E(385/T) + 2E(767/T) (51-298 OK., 0.8yc) NaaAlF6: D(144/T)
The entropy values are listed in Table 11. The extrapolated portions of the total entropies a t 298.15'K. are cryolite, 7.2%; sodium fluoride, 4.1%: and aluminum fluoride, 3.5%. TABLE I1 ESTROPIESAT 298.15"K. ( CAL./DEG.-MOLE) NaaAlFs
NaF
0-51°K. (extrap.) 51-298.15'K.
4.12 52.86
0.50 11.76
s * o : . 1 6
5 7 . 0 1 0 . 4 1 2 . 2 6 4 ~0.07
AlFt
0.56 15.33 15.89f0.08
The entropy of formation of cryolite from sodium and aluminum fluorides is 4.3 & 0.5 cal./ deg. mole a t 298.15' K. BERKELEY 4, CALIFORNIA
WRIGHT AIR DEVELOPMENT CENTER]
Infrared Spectra of Cyclopentamethylenedialkylsilaneslin the 2-35-Region BY GORDON D. OSHESKYAND FREEMAN F. BENTLEY RECEIVED NOVEMBER 28, 1956 The infrared absorption spectra of 21 cyclopentamethylenedialkylsilanes have been obtained from 2-35 p and empirical assignments made for specific vibrations. The series begins with cyclopentamethylene-silane and ends with cyclpentamethylenedioctadecylsilane. Absorption bands a t 10.93 to 11.00 and 20.20 to 20.85 p are tentatively assigned to vibrations arising from the heterocyclic ring. All the observed absorption bands are given in a table showing their position and relative intensities.
This paper presents infrared absorption spectra of a series of cyclopentamethylenedialkylsilanes in the liquid state from 2 to 35 p . This series of compounds was studied by this Laboratory for the purpose of correlating various physical properties with molecular structure.2 This paper will deal solely with the infrared absorption bands of this and mainly with the tentative band assignment of the organosilicon ring vibration.
Experimental Apparatus and Technique.-The infrared spectra in the 2 to 15 p region were obtained with a Baird Associates, Model (1) Opinions expressed are those of t h e authors and do not necessarily express the official opinions of the U. S. Air Force or the Wright Air Development Center. (2) This series of compounds was prepared by Dr. Christ T a m borski, Dr. Harold Rosenberg and Mr. James Groves, and the details of their physical properties and preparation will be published elsewhere
B, automatic recording spectrophotometer equipped with a sodium chloride prism. This instrument was calibrated to within 2 ~ 0 . 0 5p by using ammonia and polystyrene. The liquid samples were recorded in a 0.028 mm. cell with sodium chloride windows. The thin capillary thicknesses were obtained by placing a drop of liquid between two rock salt plates, which were then fastened tightly together. The spectra in the 15-35 ,.J region were obtained on a Perkin-Elmer Model 21, double beam recording spectrophotom ter equipped with cesium bromide optics. This prism was calibrated by using atmospheric carbon dioxide and water vapor bands. The accuracy of the wave lengths as recorded here is probably better than &0.05 p , which in this region of the spectrum is equivalent to about 1 1 . 5 ern.-'. The liquid samples were measured in 0.510 and 0.053 mm. cells with cesium bromide windows. All measurements in the 2 to 35 ,.J region were made a t 24.0 10.5" and a t a relative humidity of 35 & 570. Due to insufficient sample the spectra of the diethyl and 2-ethylbutyl derivatives could not be obtained in the 15 to 35 p regon.
2058
GORDON D. OSHESKYAND FREEMAN F. BENTLEY
2
5
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Fig. 1.-Tabulated
IN
25
30
35
MICRONS.
absorption frequencies of 21 cyclopentamethylenedidlkylsilanederivatives.
Materials.-The cyclopentamethylenedialkylsilanesused i n this study were fractionated through a 30-cm. short-path Yigreux column. Carbon. hydrogen and silicon analyses were performed on each compound of this series and they were found t o be 9970 pure. The compounds were analyzed by the Schwarzkopf Microanalytical Laboratory.
Results and Discussion The difficulty in establishing the presence of a ring in organic molecules by chemical means has promoted interest in identifying the presence of cyclic structures by infrared techniques. Saturated cyclic systems have characteristic frequencies arising from the bond stretching and valence angle iiiodes which occur in the fundamental region. There is a great number of articles in the literature dealing with attempts to characterize alicyclic systems, particularly cyclopropane and cyclobutane, from the infrared spectra, but the situation is still o b s c ~ r e . ~ With - ~ the possible exception of cyclopropane6 no certain means of identifying ring systems by the out-of-plane and torsional bending modes beyond 20 p has so far been realized. .\ few band assignments for some of the saturated cyclic hydrocarbons are given in Table I. Tentative frequency assignments have been iiiade for the cyclopentamethylenedialkylsilanes investigated in these studies. Figure 1 lists the 21 compounds recorded and pictorially indicates the h:xncl positions arid their relative intensities. The ylcr .md N A c q u i i t a , J . Rcserirrh A‘nfl. Bur. Standards,
( t l ii. IC. Flyer, R. Stair and C. J. Humphreys, ibid., 38, 211 (11147). ( 5 ) R . N. Jones and C. Sandorfy, “Chemical Applications of Spectro;copy,” Interscience Publishers, New York, N. Y . , 1956, p. 366. (6) T. K. McCubbin, Jr., and W. M . Stiston, J . O p l . SOC.Amev., 40, 3; (1950).
20
LENGTH
lrol. 79
infrared spectra of eight of the derivatives of this series are shown in Figs. 2 to 6, inclusively. Carbon-Hydrogen Deformation Frequencies.Absorption arising from the CH deformation frcquencies of these molecules present some interesting TABLE I Structure
-4ssigned ring vibrations
Ref.
Cyclopropyl ring 9 .8-1O .00 7-1 1 Cyclobutyl ring 10.9-11 12-14 Cyclopentyl ring 10.8-11.3 15, 16 Cyclohexyl ring 9.95-10.5,9.5-10 15,lfj Cyclopentamethyleiic silicon ring 10.93-1 1.OOn a Based on the infrared spectra of the cyclic silanes studied in this series.
correlations. Absorption bands a t G.S5 p in the spectra of cycloperitamethylenesilaiie and cyclopentamethylenedichlorosilane are apparently due to the CH2bending modes of the heterocyclic ring. The position of this band remains constant throughout the series. I t is masked to a degree by the CH2 deformation and CH3 asymmetrical deforination absorption of the large alkyl substituents on the silicon atom. Absorbance due to the syni(7) J. D. Bartleson, R. E. Rurk and H. P. Lankelma, TEISJOURNAL, 68, 2513 (1946). (8) J. M. Derfer, E. E. Pickett and C . E. Boord, ihid., 71, 2482 (1949). (9) V. 1.Slahey, i h i d . , 1 4 , 4H28 (19:2). (10) S E. Wiberley and S C . Bruce. A n a l . Chem.. 24, 6 2 3 (1932). (11) M, L. Josien, h-.Fiison and .A. S.Cary, THIS J ~ ~ J ~ X A13, L . 444.5 (1951). 112) R . R. Reid and M. Sack, i b i d . , 73, 1985 (19.51). (13) J. D. Roberts and V . C . Chambers, i b i d . , 73, 3034 ‘1931). (14) J. D . Roberts and H . E . Simmons, Jr., i h i d . , 73, 5 i 8 i (1951). (15) I.. W. Marrison, J . Chem. SOL.,1014 (1951). (16) J . Sheppard, J. I n s f . Pet., 37,95 (1951).
SPECTRA OF CYCLOPENTAMETHYLENEDIALKYLSILANES
May 5, 1057
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of cyclopentamethylene silanes: 1, unsubstituted; 2, dichloro; 3, dimethyl; 4, din-propyl.
metrical bending vibration of the CHa-C group at 7.23 p is clearly present in the spectra of all the molecules of this series containing this group. The intensity of this absorption band gives some indication as t o the number of methyl groups present in the molecule* In the spectrum Of cyclopentamethylenediisoamylsilane the absorption band is
split due to the isopropyl g r ~ u p .As~ would ~ ~ ~be~ expected the absorption band a t 7.23 p is not present in the spectrum of cyclopentamethylenedimethylsilane where the methyl group is linked to a silicon atom. (17) S A. Francis, J . Chcm. Phys., 18, 861 (1950). (18) H.L. M C M U ~and Y v. Thornton, Anal. Chcm., 04,318(1052).
GORDON D. OSHESKYAND FREEMAN F. BENTLEY
2060
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VOl. 79
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16
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WAVE NUM8ERS IN C U I
1
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Fig. 3.--Infrared
spectra from 2-16
p
m *((cRoHs.
7
10
of cyclopent.dmethy1ene silaiies: n-hexyl.
The strong absorption in the 7.03 to 7.10 M region is attributed t o the deformation vibrations of the CH2 group linked t o the silicon atom. The CH bending vibration of the Si-CH, group was observed by Wright and Hunter'g and all the tetraalkylsilanes (more than 30) studied in this Labora(19) N Wright and M J Hunter, TNISJ O U R N A L , 69, 805 (1947)
,
WAVE I1W T H IN 11 MICIONS,
IS
5 , di-n-butyl; 6,di-n-amyl; 7, diisudmyl ; 8, di-
tory absorb in this region. Young and co-workers?" also observed an absorption band a t 7.08 p in the spectra of cyclic disubstituted siloxanes containing Si-CHS and Si-CH2CHS linkages. They tentatively assigned this band to the carbon -hydrogen (20) c w Young, p c serbals c c c u r r l e and 11J Hunter r b z d , 7 0 , 3758 (1948)
SPECTRAOF CYCLOPENTAMETHYLENEDIALKYLSILANES
May 5, 1957 WAVE
IS
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.NUMBERS
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LENQTH IN YICRONS
IS
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NUMBERS
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2061
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25 30 LENQTM IN YIUIONS.
3s
40
Fig. 4.-Infrared spectra from 15-35 fi of cyclopentamethylene silanes: 1, unsubstituted; 2, dichloro; 3, dimethyl; 4,di-n-propyl.
Fig. 5.-Infrared spectra from 15-35 p of cyclopentamethylene silanes: 5, di-n-butyl; 6, di-n-amyl; 7, diisoamyl; 8, di-n-hexyl.
bending vibrations of the methylene group linked to the silicon atom. Vibrations Attributed to the Heterocyclic Ring,Analysis of the spectra of the cyclic silanes led to empirical assignments for the characteristic vibrations of the heterocyclic ring. Absorption bands at 10.93 to 11.00 p and 20.20 to 20.85 p in the spectra of these compounds are tentatively assigned to this structure. The sharp absorption band a t 10.93 t o 11.00 p appears t o be the most promising band for determining the presence of the heterocyclic ring. It is a strong band and is very constant in wave length position throughout this series of compounds. The second band absorbs strongly at 20.20 to 20.85 p and is present in the spectra of all the cyclic silanes except cyclopentamethylenesilane and cyclopentamethylenediphenylsilane. In the latter spectrum the band is at 21.00 p , just outside the above range, but in the spectrum of the silane it has shifted to longer wave lengths a t 22.30 p. This band is attributed t o the out-of-plane bending mode of the heterocyclic ring. Several other absorption bands in the spectra of these cyclic silanes appear to be characteristic of the cyclopentamethylene silicon ring, and serve to
identify this class of compounds. A weak absorption band a t 3.70 to 3.75 p is present in the spectra of all the cyclic silanes in this series, and most of the cyclopentane and cyclohexane derivatives in the API spectra. It appears to be a characteristic feature of these aliphatic ring systems. A study in the 3 to 4 p region with a lithium fluoride prism would probably disclose a band characteristic of the C-H vibration of the heterocyclic ring. The weak absorption band a t 7.83 to 7.90 p is present in the spectra of all the cyclic silanes in this series and appears to be characteristic of the heterocyclic ring. Since Si-CHa always absorbs in this region, however, this band is a risky one for other correlations. Cyclohexane has an absorption band a t 7.95 p and most of its derivatives absorb in this region. The 7.83 to 7.90 p band appears t o be associated with the vibrations of the methylene linkage in the heterocyclic ring. The strong absorption band a t 9.95 to 10.05 p decreases in intensity as heavier alkyl substituents are linked to the silicon atom. The relative position of this band is constant throughout the series. Marrison15 has noted that most of the published spectra of cyclohexane derivatives show bands in
2062
GORDON D. OSHESKYAND FREEMAN F. BENTLEY
Vol. 79
the 8.95 to 10.50 p and 9.48 to 10.00 p region, and the spectrum of cyclopentamethylenesilane. This cyclopentane and c y c l ~ p r o p a n ederivatives ~~~ ab- band is in agreement in frequency and intensity sorb in the 10 1.1 region. Absorption in the 10 p with the band for the SiH? bending frequency region also appears to arise from vibrations of the occurring a t 10.50 p for dichlorosilaneZ7and 10.62 p methylene group in the heterocyclic ring. for dibromosilane.2a This band has been observed Vibrations Attributed to the Alkyl-Silicon Link- to remain essentially constant throughout the age.-There has been some dispute over the spectra of 38 compounds containing two and three assignment of absorption bands arising from vibra- hydrogens on s i l i c ~ n . ~ ~ ~ ~ ~ tions of the methylene groups bonded to a silicon Two strong absorption bands are present in the atom as to whether i t should be assigned to the spectra of the cyclic silanes a t 10.0 and 11.0 p . 11.6 or 8 p region2lSz2and as to whether it is a de- These bands occur at wave lengths which have formation or rocking v i b r a t i ~ n . ‘ ~A* ~strong ~ ab- been assigned to the terminal vinyl linkage, sorption band a t 8.42 p was observed in the spectra -C=CHz, in the l i t a r a t ~ r e . ~ l J ~ of all the cyclic silanes studied. The relative Spectra of the Cyclic Silanes in the Long Wave intensity and position of this band is constant Length Region.-The infrared spectrum of most throughout the series. This band was also observed materials in the wave length region beyond 8 p in the spectra of alkyl silanes by Kaye and Tan- is quite sensitive to change in structure, as pointed ~ ~ spectra nenbaumZ3and i t was attributed to the symmetrical out many times in the l i t e r a t ~ r e . The deformation vibration of the methylene groups of this series of cyclopentamethylenedialkylsilanes attached alpha to the silicon atom. exhibits this sensitivity to a degree. A noticeable An absorption band in the 11.6 p region was not change can be observed in the spectra up to the observed in the cyclopentamethylenedialkylsilane dinonyl derivatives. Beyond the dinonyl derivaseries, but strong bands in the 12 to 13 p region were tive the change may be considered negligible. observed. These bands are attributed to the Several absorption bands in the wave length methylene groups in the alkyl radical which are region beyond 15 p are of interest. The medium bonded to the silicon atom, Young, Koehler and band a t 15.4 to 15.8 p is very consistent in wave McKinney2* observed an absorption band at 11.5 length position in the dialkyl derivatives, and may be related to vibrations of the heterocyclic ring. p in the spectrum of tetramethylsilane and assigned this band to a methyl rocking vibration. A strong The medium band a t 16.6 p and the strong broad absorption band is observed a t slightly longer band a t 26 to 29 p in the spectra of the dialkyl wave lengths, 11.90 p, in the spectrum of cyclo- silanes are apparently due to vibrations arising pentamethylenedimethylsilane. This band is at- from the alkyl substituents linked to the silicon tributed to a methyl rocking vibration. Absorp- atom. Similar absorption bands are observed in tion bands a t 7.97 p in the latter spectrum and a t the spectra of long chain esters studied in this 8.03 p in the spectrum of cyclopentaniethylenedi- Laboratory. The presence of these bands gives ethylsilane apparently are due to symmetrical some indication as to the size of the alkyl groups in deformation vibrations of the methyl and ethyl this type of molecule. The strong band a t 29.9 p in the spectra of cyclopentamethylenedimethylgroups bonded to the silicon atom. Absorption Characteristic of Disubstituted silane is observed in the spectra of toluene and Silanes.-An absorption band in the 10.6 to other cyclic systems containing methyl groups 10.7 I.L region, characteristic of disubstituted silanes, and may be indicative of this group. was observed and reported by West and R o c h o ~ , ~ ~Acknowledgments.-The authors wish to thank but no frequency assignments were made in that Dr. C. Tamborski, Dr. H. Rosenberg and Mr. J. paper. A strong band in this region was also Groves of this Laboratory for preparing the samples observed by OpitzZ6in the spectra of monosubsti- used in this investigation. tuted silanes. He assigned the 10.60 to 10.90 p DAYTOX, OHIO region, which is common to disubstituted silanes, (27) J A. Hawkins and &I. K. Wilson, J . Chcm. P h y s . , 21, 380 to a deformation mode of the S i H F group. An 53). absorption band has been observed a t 10.58 p in (19(28) J. A. Hawkins, S. R. Polo and M.K. Wilson, ibid., 21, 1122 (21) W. F. Edge11 and C. H. Ward, THISJ O U R N A7L7, , 6486 (1955). (22) D. H. Rank, B. D. Saksena and E. R. Shull, Disc. Fnrodoy SOC.,9, 187 (1950). (23) S. Kaye and S. Tannenbaum, J . Org. Chcm., 18, 1750 (1953). (24) C. W, Young, J. S. Koehler and D. S . McKinney, THIS JOURN A L , 69, 1410 (1947). ( 2 5 ) R. West and E. G. Rochow, J . Org Chem., 18, 303 (1953). (26) H. E . Opitz, J. S. Peake and W. H. Nebergall, THISJ O U R N A L , 78, 292 (1956).
(1953). (29) J. S. Peake, W. H. Nebergall and Chen Yun-Ti, THISJ O U R N A L , 74, 1526 (1952). (30) E. L. Warrick, ibid., 68, 2455 (1946). (31) F. A. Miller, “Organic Chemistry,” Vol. 111, Edited by H. Gilman, John Wiley and Sons, New York. N. Y., 1953, p. 138. (32) L J. Bellamy, “The Infrared Spectra of Complex Molecules,” John Wiley and Sons. New York, h’. Y., 1954. (33) K. Dobriner, e l al., J . B i d . Chcm., 172, 241 (1949).
