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Conformational analysis of (CH3)2CCl(CH2)xCH(CH3)2
Specfnxhimicn Acta, Vol. 38A. No. 11, pp. 1123-l 139, 198.2 Printed in Great Britain.
Conformationai
0584-8539/82/3 1112347503.0010 @I 1982 Pergamon Press Ltd.
analysis of (CH&CCi-(CH&CH(CH&
G. A. CROWDER~~~MARYTOWNSENDRICHARDSON Department
of Chemistry, West Texas State University,
Canyon, TX 79016, U.S.A.
(Receiued 2 November 1981) Abstract-Liquid and solid-state i.r. spectra and liquid-state Raman spectra were obtained for three compounds in a family of compounds with the general formula (CH&CCl-(CH&CH(CH& with x = 0, 1 and 2. Two carbon+hlorine stretching bands were observed in the liquid-state spectra of each of the three: Zchloro-2,3dimethylbutane, 569 and 611 cm-‘; 2-chloro-2,4dimethypentane, 573 and 628 cm-‘; 2-chloro-2,5-dimethylhexane, 561 and 626 cm-‘. It was determined that two conformers .(Tcna and TnHH) exist in the liquid state of 2-chloro-2,3-dimethylbutane and that only the Tnna conformer was present in the crystalline solid. For both 2-chloro-2&dimethylpentane and 2-chloro-2,5_dimethylhexane, the liquid is composed of the Tcan conformer and at least one of the two possible Tnan conformers. The crystalline solid exists as one of the two possible Tana conformers. Normal coordinate calculations were made for all three compounds and a force field was developed for the family. It was not possible to distinguish between the two Tnnn forms of 2-chloro-2,4_dimethylpentane and 2-chloro-2,54methylhexane.
INTRODUCTION
and Raman spectroscopy have been used to study rotational isomerism in primary [l-71, secondary [&lo] tertiary [ 1l-131 alkyl and chlorides. Similar studies have involved several series of various dimethylalkanes [ 14, 151 including 2,3dimethylbutane, 2,4-dimethylpentane and 2,5dimethylhexane. Investigations of dimethylalkyl chlorides involving both a tertiary (dimethyl) chloride and a separate isopropyl group are limited. Although SHIPMAN et al.[16] included 2chloro-2,3dimethylbutane in a study of the carbon stretching frequencies in alkyl chlorides, interpretations of spectra and assignments of frequencies were limited to the range of interest, i.e. 400-700 cm-‘. This study was undertaken in order to extend the work done on tertiary alkyl chlorides and on dimethylalkanes to a series of compounds containing both moieties, (CH3,CCl-(CHzLCH(CH& in order to make complete vibrational assignments for several compounds in that family. Also of interest was the development of a force field that could be used for other related comInfrared
pounds. ExPRRmENTAL
All i.r. spectra were obtained using a Nicolet MX-1 Fourier Transform spectrometer. During this work all wavenumbers were determined using an automatic digital mintout mode. All compounds studied were liquids at room temnerature. The liauid-state spectra for the 5OfMOOOcm-’ region were obtained using KBr plates or commercial fixed-path-length cells fitted with KBr windows. Commercial fixed-path-length polyethylene cells were used for the 2OtMOOcm-’ region. A~ontinuous dry air purge system was used to eliminate water vapor. Solid-state spectra were obtained using a commercial
Beckman VLT-2 cold cell fitted with NaCl windows. Because of the low vapour pressure of the samples, transfer of the vapor to the cold cell could not be accomplished. In order to obtain a solid, the sample was placed-between two KBr plates to form a thin film; then the nlates were nlaced directly into the cold ceh. Cooling the sample rapidly with liquid nitrogen resulted in an amorphous solid. Crystallization was brought about by annealing the solid at a temperature lO-2OY below the melting point. After crystalliiation occurred, the temperature of the sample was reduced to that of liquid nitrogen and the spectrum was obtained, All samples tested underwent crystallization. In order to obtain spectra in the region below 500 cm-‘, the NaCl windows of the cold cell were replaced by polyethylene windows. The sample was placed in a commercial polyethylene cell which was inserted into the cold cell. Rapid cooling with liquid nitrogen produced an amorphous solid which upon annealing yielded crystalline solids for ah samples tested. The temperature of the crystalline solid was reduced to that of liquid nitrogen and the spectrum was obtained. A continuous dry air purge system was again used to eliminate any water vapor. Following solidification, a vacuum was placed on the system to prevent further the formation of ice from water vapor. Raman spectra were obtained using a Spectra Physics 700 spectrometer equipped with a Coherent Radiation Labs CR-2 argon ion laser. The wavenumbers were read from a digital readout, accurate to between ?5 and f 10 cm-‘, depending on the slit width that was used. The sample of 2-chloro-2,3-dimethylbutane was obtained from Albany International and had a stated purity of %%, which was verified by gas chromatoaranhv. Both 2-chloro-2.~diiethyhYentane and 2-chloro5,S:dimethylhexane were obtained-from Chemical Samples Co. Since the purity of neither sample was certain, both were purified by vacuum distillation. Subsequent gas chromatography showed the purity of both the 2chloro-2,4-dimethylpentane and the 2-chloro-2,5dimethylhexane to be 100%. CAL.CULATIONS
Normal coordinate calculations were made with 1123
1124
G.
A.
CROWDER and M. T. RICHARIWN
a DEC PDP-10 computer. The vibrational problem setup utilized the FG-matrix method of WILSON 117, 181. The computer programs written by SCHACHTSCHNEIDER[19, 201 were used for solution of the vibrational secular equation (VSEC), the calculation of the G-matrix (GMAT) and for least-squares refinement of certain force constants to fit the calculated frequencies to the observed frequencies (FPERT). The initial force constant matrix was set up by the use of a program written by CROWDER and PoTr~~[21]. The molecular parameters used were: C-C = 1.54& C-H = 1.09 A, C-Cl = 1.77 A, all angles were assumed to be tetrahedral (109.47”), and atomic weights used were: Cl = 35.453, C = 12.01115, H = 1.00797.
RESULTSANDDISCUSSION 2-Chloro-2,fdimethylbutane SHIPMAN et al. [ 161 included 2-chloro-2,3dimethylbutane in a study of characteristic carbon-chlorine stretching frequencies of primary, secondary and tertiary alkyl chlorides. Although the entire redrawn liquid-state i.r. spectrum was included in the paper, considerations were limited to the carbon-chlorine stretching frequency only. Further, neither Raman nor solid-state i.r. spectra were included in the study; therefore, liquid- and solid-state i.r. spectra (Figs. 1 and 2) and liquidstate Raman Spectra (Fig. 3) were obtained and are given in this work. SHIPMAN et al. reported C-Cl stretching frequencies at 611 and 569 cm-’ which he attributed, respectively, to the TCHH(C,) and T,,, (C,) conformers (Fig. 4). Their assignments were substantiated in this work. Examination of the solid-state i.r. spectrum reveals that the 569 cm-’ band is present in the spectrum of the crystalline solid, while that at 611 cm-’ is not. This evidence shows that the THHIr conformer is the one present in the crystalline solid. As an aid to vibrational analysis, normal coordinate calculations were included in this work. The beginning force constant values were compiled from branched alkanes[l9] and from tertiary alkyl chlorides[ll] and were used to make zero-order calculations. Observed frequencies from i.r. and Raman spectra were matched to calculated frequencies with an average difference of 8.1 cm-‘. Subsequent refinement of force constants eventually yielded an average error between observed and calculated frequencies of 6.2 cm-‘. Several low-wavenumber values were not fitted well, and an additional force constant, F,, was included. Only one more computer run was necessary. In that final run, 12 force constants of a 40 parameter modified valence force field were adjusted to fit 63 frequencies below 1500 cm-’ with an average error of 5.5 cm-‘. Eventually, three conformers of 2chloro-2,4-dimethylpentane and three conformers of 2-chloro-2,5_dimethylhexane were included and
calculations were made for all three compounds simultaneously. The observed and calculated frequencies of the two molecular conformations of 2-chloro-2,3dimtthylbutane are shown in Table 1. Of 63 assigned frequencies, 12 were unique to the l’HHH conformer and 12 others to the TCHHconformer. Only one band, that at 1069 cm-‘, was not assigned as a fundamental. Since both possible conformers of this compound were considered, this band cannot be attributed to a fundamental vibration but can be assigned as a combination band. The potential energy distribution as represented by symmetry coordinates accompanies the calculated frequencies in Table 1 and can be used to interpret the computer assignments of those frequencies in terms of symmetry coordinates. Shipman et al. reported bands at 743 and 508 cm-’ in the i.r. spectrum of this compound, which were labelled “unassignable at present”. Computer calculations predicted frequencies close to the values in question. A frequency calculated at 742cm-’ (73% C-C stretch and 25% CH3 rock) for the THHH conformer only was assigned to a 755 cm-’ band, while the corresponding frequency calculated at 737cm-’ (81% C-C stretch and 15% CH, rock) for the TCHH conformer only was assigned to a band at 741 cm-‘. The observed band at 508 cm-’ was assigned to mixed modes calculated near 502cm-’ for both conformers. The remainder of the computer assignments are presented in Table 1 without comment here. 2-Chloro-2,4_dimethylpentane and 2-chloro-2,5dimethylhexane Each of the next two compounds in the family, 2-chloro-2,4_dimethylpentane and 2-chloro-2,5dimethylhexane, can exist in a large number of rotational isomeric forms. Initial efforts to identify the major stable spectroscopically distinguishable forms began with the generation of liquid- and solid-state i.r. spectra (Figs. 5, 6, 8 and 9) and liquid-state Raman spectra (Figs. 7 and 10) for each compound. Two bands were apparent in the carbonchlorine stretching region of the liquid-state spectrum of 2-chloro-2&dimethylpentane. The band at 628cm-’ falls within the typical range for TCHH[161 and was assigned to that conformer. Likewise, the 573 cm-’ band was assigned to a T,,, conformer for the same reason. However, inspection of all conformers in which five carbon atoms are coplanar reveals that two THHH forms are possible, which are designated here at THHH and T&.,, (Figs. 11 and 12). This evidence suggested two possibilities: (1) The two observed bands account for two conformers only (in which case, the 573 cm-’ band is due to either the THHHor the T;I&. (2) The two observed bands account for three
112s
Conformational analysis of (CH,)FCl~CH3,-CH(CH,)z
I E
x
SAA Vol. 38. No. II-B
1126
G. A. CROWDERand M. T.
F~~~RDs~N
Conformational analysis of (CH32CCI-(CH3,-CH(CH32
600 cm-’ 400
800
1400
200
1127
1200
1000
Fig. 3. Raman spectrum of 2-chloro-2,3_dimethylbutane liquid.
conformers
THHH
(in which case, the 573 cm-’ band is due to both the THm and the T;I&. Further, because the 628 cm-’ band disappeared from the spectrum of the annealed solid, it was concluded that the crystalline solid was composed of a THHHconformer. Since only one conformer is usually present in the crystalline solid, it remained to be determined which of the two possible forms, THHHor T;IHH, is the one actually present in the solid.
TCHH
Fig. 4. Conformers of 2-chloro-2,3-dimethylbutane. Cl = chlorine, Me = methyl.
Table 1. Observed and calculated wavenumbers for 2-chloro-2,3-dimethylbutane
Anled.&
solid
solid 1468s 146Om
1456m
13% VW
l3JJ
VW
131521
1198w
1462s
co.1442sh 1393m 1381w 1371vs
1321nw
1460s
1454lILs
1440~ l391m 1380s
1439Ire -l379 vs
1370vs
1372vs
1320nw
1238vs 1240VW 1221m.l 1221* 1194In? 11% w
TomOmfonmti
~calfmtial
Iu -led
cal$
(a
)sym.
1467
1458 1458 1456 1455 1455 1454 1454 __
1363
I.393 1385 l3JJ 1371 1363
1329m
1336
-1224uw 1196w
__ 1220 1201
P.E.D. GY 3(JJ).100.2) 3(89) 3(87) 3(92) 3(92) 3(92) 3(93) 304) 4(80),2(25) 4m* 2a5) 4(93) 4(%)
Qlcl (a ) 1465 1458 1458 1456 1455 1455 1454 1452 1392 1384 1378 1371 1356
P.E.D. RF X80) X89) 3&w 3(91) 3(92) 3(92) 3(93) 3@4) 4(79),2(25) 400)~ ~(14) 4(89) 4(91),2w 6(59),4Ul)
6(67),4(11) 1248 10(36),206) -2(48),lO(18). 1190 ll(16).6(10)
2(52),lO(28)
1128
G.
A.CROWDERand MT.
RICHARDSON
Table 1. (Contd) b
Iu
~~1157 sh
(an )sym.
L157m
1163 m
1153
a'
lW&
1149 s
1131
a'
lO(57).2(17)
1159 w
1146 8
L146 s
ll3Onw
1129 w
1129vs 1100nw
1088 US
LOa8m
1070 w
lC69m
1069m
1050 w
1050 m
1049m
943m
-11Olm --
6(19),
__ 1110
a"
2(4&10(16).
__
Tm
'Zcmfonmth
&lEl (a )
P.E.D.
CO=
-1152
lO(W,
1139
lO(49).2(17)
2W)
-1104
lO(44).2(31),6Ul)
1048
10(55),6(18)
506 + 568 = 1074 1051m
1054
10(64),6(20)
999 VW
998 VW
1009VW
998
lO(87)
998
%lw
96ovw
962 w
973
lO(88)
972
lOW lO(83)
945Iw
945 w
947 m
944
lO(81).20.5)
943
10(80),2(14)
922 w
922 VW
920 rat?
927
10(69),2W
925
10(63),2(31)
911 VW
9l3 _-
2(52),lO(47)
898
2(59), lO(47)
880
2(57).1004)
871
2(65),lO(30) 2(73),lO(25)
918 w 882 m
P.E.D. UY
c=lfl
Liquid 1159 w
canfmtim
888 m
883nw 878 IIW
-879 m 754vs
--
756 m 741 m
755 IILS 756 m 741m
741m
--
742 -_
612 vs
612 s
611~x3
--
__
568 vvs
56anrs
568nm
567 I~EI
576
1(97),l2(26)
--
507 s
506m
506w
502 m
502
1(35).603, 20.3).12w 11(69),2(13)
503
-737
2(81),lO(15)
619
1(98),12(31) 6;:wj 11(32),
--
462w
wvw
460
450
427 nw
429 w
397 s
397 m
428 _-
423 __
357 s
358 m
__
__
349
348
336
x2(89),ll(17)
303
11(76).12(M)
294
12(85).ll(10)
273
12(51),ll(40)
245
14(87),ll(11)
255
‘W’;.
242
14(96)
243
14(97)
241
14(98)
241
14(95)
241
14(92)
240
14(96)
212
11(86),14(12)
221
171
12(72),6(27)
178
14(41),ll(35).609) l2(69),ll(42)
226 m
eneqyofless
ll(53).l2(16),2(10)
407
ll(52).1(15),12(14)
353
ll(61).12(32)
l5(97)
85 kmn5htions to thepotential the follauingdefinitions:
11(79),lO(12) 428
thm10%arenot
--
82
12(22), 11(16),
15(98)
included. lhe cmrdinatenurbers refer to
1 C-Cl stretch
7
M2"p
13 c-c-c bend
2 c-c stretch 3 CH3 antisym.deformation
a 9
Gi2twist CZ-$rock
14 CN3 torsion
4 CH3 syramtricdeformtim
10 CH3nxk
16 C-C torsion
596 C-H bend
11 cc3tmd 12 c-c-Clbend
17Q$=w
Analogous to 2-chloro-2&dimethylpentane, only two bands were apparent in the carbon4rlorine stretching region for Zchloro-2,5dimethylhexane. The band at 626 cm-’ was assigned to TcHH; that at 561 cm-’ was assigned to THHH. Once again, the 561 cm-’ band could be due to THHH, to Tr&.n.r,or to both. Likewise, the band at 561 cm-’ was observed in the solid-state spectrum, indicating that again one of the two possible THHH conformers is present in the solid. Consequently normal coordinate calculations were initiated in an attempt to determine which of the above alternatives was correct. Although neither compound exhibits symmetry, symmetry
15 cH2c1 torsion
coordinates were developed as an aid for interpretation of computer assignments. Force constants were transferred from 2-chloro-2,3dimethylbutane. Since both compounds under consideration include methylene (-CHT) groups not present in 2-chloro-2,3_dimethylbutane, additional force constants for this group were included. Zero-order calculations and subsequent assignments of observed to calculated frequencies were carried out. The resultant average difference (error) between observed and calculated frequencies was 8.1 cm-’ for all six molecules from the two compounds. Since all six molecules utilized the same force
Conformational analysis of (CHs)2CCI~CH3,-CH(CH,)2
1129
1130
G. A. CROWDERand M. T.
&CHARDSON
Conformational analysis of (CH,)zCCI-(CH&-CH(CH~)z
1131
l-
,
u,
1 800
*
I
600 cm-’ 400
I
I
.
200
Fig. 7. Raman spectrum of 2-chloro-2,4-dimethylpentane liquid.
field and since the development of a force field with general application within the family of compounds was desired, all further computer calculations were carried out on the entire group of conformers simultaneously. The tirst such leastsquares refinement lowered the overall average error for the group from 8.1 to 6.9 cm-‘. At that time it was noted that the individual average errors of all molecules except the THHH and the T&M conformers of 2-chloro-2,4dimethylpentane were 6.5 cm-’ or less. Such a bimodality in errors of individual molecular conformations was unexpected and suggested that perhaps one of the THHH conformers of 2-chloro-2&dimethylpentane was favored over the other. In order to test the hypothesis, computer input data for the two THHH conformers (THHH and Tr!r,r.,) were separated and a least-squares refinement was made for each independently to achieve the best possible fit by adjusting the same set of force constants. The resulting average error for the THHHconformer was 5.7 cm-’ and that for TkHH was 4.9cm-‘. Each of the two force fields generated in the independent refinements was then used to make individual zero-order calculations for the four remaining conformers. It was anticipated that if one of the THHH conformers under consideration were indeed superior to the other, the average error produced by zero-order calculations using its force ‘constants would be significantly lower than the corresponding error generated when force constants of the alternative conformer were used. Unfortunately, average errors so produced showed too little difference to dis-
tinguish conclusively between the conformers in question. Since neither the THHHnor the T;IHH conformer could be eliminated from consideration, normal coordinate analysis proceeded on all conformers. In order to develop a force field with truly broad application, the THHH and TcHH conformers of 2-chloro-2,3dimethylbutane were added to the group of molecules already under consideration and the least-squares refinement process was continued. In the final run, seventeen force constants of a 48 parameter modified valence force field were adjusted to fit 255 frequencies below lSOOcm-’ with an overall average error of 6.1 cm-‘. The resulting force constant values are given in Table 2. From the relatively low average error, it is reasonable to conclude that the resultant force field is equally applicable to the three compounds considered. This is a little surprising because the methyl-methyl or methyl-chlorine interactions are different in all three compounds. Indeed, the THHHconformer of the butane is a true H’ conformer, i.e. the Cl atom bisects a C-C-C angle, as for PH’ conformers, whereas the 4methyl group is forced into 1,3-parallel repulsion with either the 2-methyl or the chlorine in the two THHH conformers of the pentane. On the other hand, there is essentially no such interaction in the hexane conformers. The observed and calculated frequencies of 2chloro-2,4-dimethylpentane are presented in Table 3 and those for 2-chloro-2,S-dimethylhexane are shown in Table 4. The potential energy distributions accompanying the calculated &&en-
1132
G. A. CROWDER and ht. T. lb%ARLWN
Conformational analysis of (CH,)*CCI~CH3,-CH(CH,)2
-2
c
-
1133
G. A. CROWDER and M. T.
RICHARDSON
-
/
J Fig. 10. Raman spectrum of 2-chloro-2,Sdimethylhexane liquid.
T’HHH
TCHH
Fig. 11. Conformers of 2-chloro-2&dimethylpentane for which calculations were made. Cl= chlorine; Me= methyl.
TCtfH
Fii. 12. Conformers of 2chloro-2,5diietbylbexane for which calculations were made. Cl = chlorine; Me = methyl.
ties can be used for explanation of computer assignments. Inspection of the data consolidated in Tables 3 and 4 sheds little light on the question of which THHH isomer is responsible for the vibrational bands present for the solid. It is readily obvious that calculated frequencies for the THWHand Tr!u.u., conformers show strong similarities. This is true for both 2-chloro-2&dimethylpentane and 2chloro-2,Sdimethylhexane. When these similarities are considered together with the inconclusive THHH carbon-chlorine stretching data, it appears that there is insufficient evidence to draw conclusions regarding the presence or absence of the two isomers beyond a statement that at least one of the two must be present. Examination of Tables 3 and 4 reveals that the three conformations considered for each compound adequately account for the observed frequencies. For 2-chloro-2,4_dimethylpentane, eleven bands are due solely to the THHH conformer(s) and nine to the TCHH conformer. Likewise, nine bands were assigned exclusively to the THHH conformer(s) and nine bands to the TcHH conformer of 2-chloro-2,Sdimethylhexane. Furthermore, only two observed bands of each compound were unassigned in the computer calculations. The accumulation of evidence cited above suggests that the conformations being considered are the major ones present in the two compounds. The unassigned bands of 2-chloro-2,4dimethylpentane were attributed to summations. It is also possible that those bands as well as the unassigned bands of 2-chloro-2,5-dimethylhexane are due to conformations not considered in this
Conformational
analysis of (CH&Xl+ZH&-CH(CH,),
1135
Table 2. Force constants for (CH3,CCl_(CH3,-CH(CH,), Coordinate(s)
Force Constant
Group
Involved
Atom(s) cormnon Valuea
Standard Error
Stretch Xr Kd Rs KR
C"3 C"2 C-CH-C
KRl
C"2-C"l.2 CH-CH3
RR(X)
C-C-CL
C-Cl XX Stretch-Stretch --
C-H
4.699
C-H
4.546
C-H
4.046
c-c
4.331
c-c
4.623
c-c
4.189
C-Cl
3.231
C
C"3 C-CH2-C
C",C" C".C"
C
0.016
c-c-c
cc,cc
C
0.101
c-ccl-c or C-C-C-Cl C-C-Cl
cc,cc
C
0.320
CC,CCl
C
0.550
C"3 C-CH3
"C"
0.533
0.001
CC"
0.607
0.002
C"2 C-CE2-C
"C"
0.510
CC"
0.656
c-c-c
ccc
1.130
c-c3
ccc
0.713
0.006
C-CH-C
CC"
0.713
0.006
c-c-a
ccc1
0.982
C-CH3
cc,cC"
c-c
0.134
0.011
C-CH2-C
CC,CCB
c-c
0.382
0.013
C-CH2-C
C
0.137
0.014
c-c-c
CC)ccli cc,ccc
c-c
0.394
0.011
FRf
C-C-Cl
CC,CCl
c-c
0.075
FXE
c-c-a
CC1,CCCl
C-Cl
C-C-Cl
ccl,ccc
C-CH3
CC”,
C-CH2-C
FRX Bend H a "6 "6 H -I H w "e "S "_:
0.064
Stretch-Bend -FM FRI F' RY FRW
0.400
C
-0.330
CC”
c-c
-0.029
0.002
CC” ) CC”
c-c
0.003
0.003
c-CH2-c
CC”,
CC”
C-H
0.046
0.004
F+ F YW F;
c-c3
ccc,
ccc
c-c
-0.041
C-CH2-C
CC”,
CCC
c-c
-0.031
c-ccl-c
ccc1.ccc1
C-Cl
-0.050
F_ W1
c3-Cl
ccc.ccc1
c-c
-0.065
ft w
c*-c-c-c+
c*cc ,
c-c
-0.011
fwg
c*-c-c-c+
c*cc ) ccc+ L gaucheb
c-c
0.011
CH2-CH2
"CC,CC” Ltrans.l
c-c
0.022
0.005
c-c
-0.021
0.005
C
0.004
0.003
C
-0.009
0.004
FXU Bend-Bend -F6 F F;
fYt fB Y
CH2-CH2
fyt'
C*-CH2-C+H2
fyB'
C*-CH2-C+H2
ccc+ L trams’
xc*-CC+" lgaucheJ
0.008
1136
G. A. CROWDER and M. T. RNXGuXON Table 2. (Contd) Coordinate(s) Involved
Group
Force Constant
;k~;;) Value=
C-c-m2
CCC,CCH ltransl
C-C
C-C-CH*
ccc, CCH
c-c
-0.052
Standard E?XOr
0.040 0.005
lgauche~ CH2-C-Cl
HCC,CCCl LtransJ
c-c
0.070
CH,-C-Cl
HCC,CCCl Lgauche~
c-c
-0.121
C-C-C-Cl
CCC,CCCl [tram J
c-c
0.041
C-C-C-Cl
CCC,CCCl Lgauche'
c-c
-0.024
CH3-C-
or
c-c
0.012
C-C
0.023
0.015
-CH2-CH*-
(C)2CCl-CH2-
%&retching constants are in units of mdyn/A; stretch-bend constants are in units of mdyn/sad; bending constants are in units of ndyn i/(rad)'.
Table 3. Observed and calculated wavenumbers for 2-chloro-2,4-dimethylpentane
=
Liquid
14648
1469vs
1456 s
1456 s
1468vS
1456 s
1441m
Annealed Calq solid (an ) 1472 vs
1389 s
I.3888
1370 w8
1369 vvs
Gel (a )
TaCm&xmtti
P.E.D. e/.Y
"41 (an )
1472
3(45),j(24), 17(1'3>
1471
P.E.D. W 3(4;;il:)(26),
1460
3(81)
1460
3(81)
1460
3(81)
1457
3(89)
1457
3(81)
1460
3(81)
1456 146ovs r 1456
3(91)
1456
3(91)
1456
3(90)
1456
3(91)
1456
3eJO) 3(91)
1455
3(91)
1455
3(93)
1454
3(91) 3(93)
1455
1454 1452
3(94)
1452
3(94)
1452
1445
3(49).5(36) 559 + 867 = 1426
1448
3(49).X36)
1445
3(91) 3(52).5(33)
1380 1379
4(93)
1380
4(93)
1380
4(93)
404)
1379
4(94)
1379
1378
4(90), 2Ul)
1378
4(91)
1377
4W) 4(93)
1368 ws
1371
4(96).2(11)
1371
4(95)
1371
4(95)
1361 s
1351
7(41) 6(33),
1361
7(39) 6(31).
7w;i4;w)I
1331
2&V 6(56),2W)
1350 1329
6(56), 2(15)
1303
6(33),7(31),
1284
7(37).6(28).
1444mS 1389 ms 1384 s
1362 w
P.E.D. W
1470
1430 m 1389 vw
T~Cmformtim
TmCc&mticn
IR
lkamealed Solid
2&d
1454
3(91) 3(93)
1337w
1327
1306 w
1298 w
1301 w
1306 nw
1288
607)s 2(15) 6(3%&W)
1265 VW
1264 m
1264m
1264 vs
1244
8Wil;,(26’,
1249
8(33) 2(28). 1257 lo&, 6(12)
2~.~~~;(27),
1226 vw
1222 nw
1223m
1226 ws
1222
Z(39).lO(31)
1217
2(52), lO(28)
1189 In?
1186 nw
1188 m
1188 m
1186
10(32),2(20), 904). 6(13)
1208
10(29),2(28), 1226 804) 2(27),lO(26). 1196 9Ul). WO) 10(37),2(28)
--
2($(3‘&(26),
--
1174 w 1151 m
ll39nw 1103 w
1155 s
1170 Ins
1169 s
1165
2(33),1009). 6(13),8(10)
1150
1154 vs
1158s
1136
'NW',,
2W) s
1142
2(17),8W)
WG), 7-U)
10(28),2(20),w
w+; I 9w I
1146llm 1145 s
_-
_-
__
1145
2(;;&10(14),
ll36m
__
-_
__
1128
lo;:mj 2(12),
1088
1094
-_
__
1059
1064
1101 ml 1098m
1081m
9
1078 m
1136 m 1103 m 1094 m 1079 m
1105 m __ 1079 n.3
lo@), 2(22), 8(17),6(16)
-1090
10;Wj
2(27). 1058
lWWj
2(18),
'Oi:O;j2(34),
1137
Conformational analysis of (CH~)#XI-(CH&CH(CH3~
1023 V-VW 1026 VUJ 989 w
990 nw
989 m
1031V-VW __
985 aw
948m
94s VW
986 m
573 + 445 - 1018
__ 1003
__ 1001
lO(81)
lO(J9)
974
lO(J4).2(11)
976
l;;W9],2(14),
974
10(75),2(U)
955
lO(49).9(30)
972
lO(65).2(12)
953
'Wj
908),
947 w
951 nw
948
10(55),2(35)
931
10(67),2(28)
942
10(53),2(40)
935 w
935 Iw __
932 __
lO(63).2(32)
926 _-
10(57),2(31)
929
10(59),2(30) lo(%), 2&O)
921
10$:Wj 2(3J).
928 --
903
2(52),lO(4J)
--
927 w 922 w
928 w 919 w
917 m
921
876 w
876 cw
__
_-
,868"
867 w
865 m
885
844m
842m.I
843w
84&m
835
2(60).lO(17)
811 s
80911~
808111
798 __
2CJ9)
073 IIW
1006 __
lO(80)
8-42 2(57),lO(22) 790 2(79)
835 __
2(61). lO(l8)
__ __
777
2(82)
621 __
l(100).12(31)
786 m
785 w
788 "
805 m __
630 m
629 m
628 m
-_
__
576 vvs
573 s
570 s
559 m
562
l(126)
560
l(137)
512 vs
507 V\NJ --
510
514
ll~~~W)2(20).
516
11(33),2(17), -13(17),l2(12)
473 m
472
_-
__
471
11(49),l(22)
449m
44s
447
445
6(55).ll(19)
442
6(58),ll(18)
448
6WilU23).
__
415
406
ll(J8)
406
ll(80)
408
i1(68),6(U)
380 ms
382
383
366
12(85),ll(11)
386
11(59),12(25)
390
11(~~Nh)12(20),
356
410 nw
360 s
356
334
12(50),ll(4.4)
344
12(80).ll(26)
346
12(50),ll(45)
328m
328
320
11(64),12(25)
305
12(56).ll(32)
311
11(65),12(32)
298 m
303
290
282
12(43),ll(30)
290
12(69).ll(28)
263 ms
263
270
252
12~~~W)11(32),
--
b181 m
243 241
14(99) 14(98)
244 241
14(94) 14(94)
246 243
14(81) 14(99)
240
14(96)
240
14(88)
241
14(98)
236
14(82),12(10)
239
14(88)
239
14(95)
235
12~;;Wjj14(1J),
132
12(50),l3(40)
132
13(43),11(28), 12(22)
81
"$:wj
55
16(72).15(23)
16(16),
146
13(41).ll(31)
ww.
75
15~~~~i~9W),
84
“;:89j
55
16(76),1507)
59
16(72),15(23)
a See note a, Table 1.
b Not used
inccoputerrefinenent.
Table 4. Observed and calculated wavenumbers for 2-chloro-2,Sdimethylhexane
1469ws
1453 w
1469vs
1452 s
5w~iL&0.
1476
‘v+%3’:5”‘,
1462
3(73),5W)
1462
1459 1456
3(82)
1459
3(83)
1456
1471 ms
1476
1464IW
1453 s
1444m
1476
5wj(;$:”
3(73).501)
1462
3(72), 5&l)
3(82) 3FJ3
1459 1457
3(82) X85)
14%
3(91)
1456
3W)
3(89)
1456
3(91) 3(89)
1456
1456
1455
3(91)
1455
3(87)
1455
3(87)
1455
3(82)
1454
3(93)
1454
3(94)
1454
1452 1435
3W) 5(5;)(ioJ(18),
1452
3(94)
1452
3(93) 304)
1435
5Wio;JW.
1436
5i5io;J(18),
I
G. A.
1138
CROWDER
and hf. T.
bCHARDSON
Table 4. (Contd)
1393 1384 1378 1371 l358
1334
4(69).2~27) 4(91),204) 4(95) 4(95) 6(36).7(24), 4(18),2Cl6) 6$$gj 7(3l),
l304m
1317
6$;0ij7(36),
1317 6$6ij 7(36), 1315 7$;Wj 6(32),
7;0Qj 8(W.
1263 7(45),2(20)
l39ovs
l3a6vs
13a5vs
I.382 s
I.370 w
l37Ows
l369ws
l370vvs
134Onw
1338nw
1339IIW
1334w
1393 1385 1378 1371 1358
1328ow
1328m
1328w
1305nw
1305m
l305m
4(69),2(27) 4(91),2(14) 4(95) 4(95) 6(35),7(24), 4(18).2(16) 1334 6$0& 7(31),
1393 1385 1377 l371 l358
4(69),2(27) 4(91),204) 4(96) 4(%), 2(12) 6(36),7(24), 4(17),207) 1333 6$:'2ij 7(26),
1275VW
I.269 w
1269w
I.272 nw
1271
1243w
I.241 m
l241m
I.243 m
1237
1219w
1216m
12171118
1220m
1214
8(30),7(27). 2(B), 6(12) NW;], 2(31),
1249 8(4;(il;(17),1259 .7(39), 2(19), 8(10).6(lO) 1214 2(4f;il;~C32), I.214 27(Wj lO(27).
1181m
1187nw
1189tn
1192m
I.200 WW',, 2(26),
1187 8(4;:ioO(23).1194 8(25),lO(23).
1170m
1169sh
1169m
1168nw
1175
1170 8(3;(&&(28). 1173 8(50),9(23)
1150m
ll54m
1156118
1153m
1149
__
1140Ill 1134m
1134m
1130m cu.1124 sh
1124VW
1120
1113nw
lx? m
1113m
1117
108onw 1055WI 1010w a.975
953 m 94Onw 920w
1102m
1102IM
108om
1080s
1054vvw 1055w 1010VW 1010VW 979 VW
979 w
972VW
972 VW
952vd 94ovw 920 w
952VW 939vv.4 920w
846ms
847m
846111
819 m 811 Iw 766w
817 sh 808111
819nw 808m 763IW 759Iw 626m 575 s 533
__
1093
1055w lOO8w 980m
1048 1004 987
_-
__
955w 936w 922Ew 917m
970 943 933 916 910
847m
861
10(42),8(23). 2(13) 2(69) 10(58),9(17)
1092 W;,
8(24), 1097 8;&2(26),
1048 2(69),lO(10) 1044 2(75) 1004 10(59),9(16) 1010 lO(72)
10(56),9(l9), 2W)
__
973
910
971 948 937 923 907
w5
849
2(55),lO(22)
849
2(53),lO(23)
969, 2W) 269). 9W)
803 ___
9(7l).2u.5)
819 781 __ -r
775 617 L-
970
2(52),10(44) 2(M), 10(4a
926
941 931
__
_805 786 _-_
‘SW, 2G33 2~821
563m __
561 __
l(132)
561 _-
l(131)
496
llW, WO), 13(20),2(10)
496
l;g;], 13(19),
462
11(26),l3(20). -6(19);2(10! l;?;;, 13(19), 471
469 8
469
469
460
444m
445
__
__
~a.421sh
421
410 m 394m
412 397
__ __
375 s 356nx
370 356
377 347
383 365 328 319 281
b310 b282
_422
__ _ll(93)
12(67),ll(27) 12(72),ll(27) 12(53),ll(33) 12(44).ll(39)
lO(%), 9(26) lO(83) 10(60),2(25) lO(63).2(30) 2(49),lO(47)
10(a) 10(77),2(16) 10(54),2(37) lO(51).2(44) 2(48).lO(42)
lO(82) 10(80),2(15) lO(61).2(32)
-_
759m 626m 576 s 533 502
b3llln¶ b282
1119 10(31),2(22), -8(10).6(10) 1113 2(38),10(24), 1119 7(33),10(32), 7(14),6(10) 2(22),8UO) -_ 1109 1;{4$, 208).
e
808111 762m __ __
628m 578VI5 534m 502m
2(23),
2(25) 6(U), 7ClO) xwj lO(251, 10(30),
_-
1078m
208). 600)
1167 lO(19) 6(14), -8d') __ 1145 lW&
-_
114.0 m
1113ills
8(56),9(3U
1269 8$:W;j2(21).
10(39),
__
453
ll(20).6(18), 11(35),6(19), W14). ml)
6$;;ij11(27), --
-_
416
11(46),6(25)
-_
388
Wj
383 362 327. 320 281
6W).
ll(93) 383 ll(90) E l2(83),ll(16) -l2(66),11(29)- 349 12(60),1106) 12(50),ll(33) 300 12(88).2(U) l2(43).ll(39) 263 14(38),11(28), W17)
Conformational
251
14&u)
251
14(82)
243
14(94)
243 242
14(99)
243 242
243 242
14(98)
14(99)
14(99) 14(99)
240
14(96)
240
14(96)
236
207
13(24), 11(18), L2(16), 140.5)
205
13(27). l2(20), 213 11(19), 14(14)
12(29), ~(25)~ y&‘, ll(12) *
127
15(37), 16(23), 13(17), ll(15)
139
15(40), 16(27). 13(U), ll(lO)
15(49), 16(32)
117
lpj
112
13(45), 11(17), 106 12(15), 16(10)
13(55), 1208)
56
16(63), l2(11).
62
16(76), 905)
47
l5(10) 16(71), 15(25)
48
16@4), 1500)
5s
12(18) *
16(66), 9(18), 12(10)
47
a See
I'bte a,
Table
1139
analysis of (CH&CCl_(CH&CH(CH32
16(68), 15(28)
138
14(99)
1.
b Not used in cmputlz refinanent.
work. No doubt rotations occur that produce conformers in which the skeletal carbons are no longer coplanar. Acknowledgements-The authors are grateful to The Robert A. Welch Foundation, Houston, Texas, and the Killgore Research Center for financial support of this work. REFERENCES
r11 J. K. BROWN and N. SHEPPARD, Trans. Faraday sot. so, 1164 (1964). PI G. A. CROWDER and W. Lm, J. Mol. Strut. 64, 193 (1980). 131 V. SCHEITINA and E. BENJZDEITI,Spectrochimica Acta 34A, 353 (1978). r41 Y. OGAWA,S. IMAZEKI,H. YAMAG&HI, H. MATSUURA, I. HARADAand T. SHIMANOUCHI,Bull. Chem. Sot. Jpn. 51, 748 (1978). 151 G. W. F. PARDOE, Spectrochimica Acfa 27A, 203 (1971). [61 I. HARADA, H. TAKENCIU, M. SAKAKIB~RA, H. MATSUURAand T. SIUMAN~IJ~HI,Bull. Chem. Sot. Jpn. so, 102 (1977). 171 G. A. CROWDER and M. R. JALILIAN, Can. J. Spectros. 22, 1 (1977).
[8] P. N. GATES, E. F. MOONEY and H. A. WILLIS. Spectrochimica Acta 23A, 2043 (1%7). r91 G. A. CROWDER and M. IWUNZE, Con. J. Chem. 55, 3413 (1977). WI W. J. MOORE and S. KRIMM, Spectrochimica Acta 29A, 2025 (1973). [ill G. A. CROWDER and C. HARPER, J. Mol. Stract. 68, 89 (1980). [l21 R. P. HIRSCHMANNand R. N. KNISELEY, U.S. At. Energy Comm. IS-641 (1963). [I31 N. T. McD~vrrr, U.S. Dept. Corn. Ojice Tech. Seru., AD 268,648, 1 (1961). [I41 C. TOSI and A. PINTO, Spectrochimica Acra 28A, 585 (1972). wd H. LUTHERand H. H. OELERT, .J. Anal. Chem. 183, 161 (1961). WI J. J. SHIPMAN, V. L. FOLT and S. KRIMM, Spectrochimica Acto 18, 1603 (1%2). [I71 E. B. W~SON, JR., J. Chem. Phys. 7, 1047 (1939). WI E. B. WILSON, JR., J. C. DIKIUS and P. C. CROSS, Molecular Vibrations. McGraw-Hill, New York (1955). and R. G. SNYDER,Spec[I91 J. H. SCHACHTSCHNEIDER trochimica Acta 19, 117 (1%3). Shell Development Co. m J. H. SCHACHTSCHNEIDER, Tech. Repts. Nos. 231-64 (1964) and 57-65 (1%5). Appl. Spectrosc. ml G. A. CROWDERand J. K. Pm, 33,649 (1979).
Conformationai
0584-8539/82/3 1112347503.0010 @I 1982 Pergamon Press Ltd.
analysis of (CH&CCi-(CH&CH(CH&
G. A. CROWDER~~~MARYTOWNSENDRICHARDSON Department
of Chemistry, West Texas State University,
Canyon, TX 79016, U.S.A.
(Receiued 2 November 1981) Abstract-Liquid and solid-state i.r. spectra and liquid-state Raman spectra were obtained for three compounds in a family of compounds with the general formula (CH&CCl-(CH&CH(CH& with x = 0, 1 and 2. Two carbon+hlorine stretching bands were observed in the liquid-state spectra of each of the three: Zchloro-2,3dimethylbutane, 569 and 611 cm-‘; 2-chloro-2,4dimethypentane, 573 and 628 cm-‘; 2-chloro-2,5-dimethylhexane, 561 and 626 cm-‘. It was determined that two conformers .(Tcna and TnHH) exist in the liquid state of 2-chloro-2,3-dimethylbutane and that only the Tnna conformer was present in the crystalline solid. For both 2-chloro-2&dimethylpentane and 2-chloro-2,5_dimethylhexane, the liquid is composed of the Tcan conformer and at least one of the two possible Tnan conformers. The crystalline solid exists as one of the two possible Tana conformers. Normal coordinate calculations were made for all three compounds and a force field was developed for the family. It was not possible to distinguish between the two Tnnn forms of 2-chloro-2,4_dimethylpentane and 2-chloro-2,54methylhexane.
INTRODUCTION
and Raman spectroscopy have been used to study rotational isomerism in primary [l-71, secondary [&lo] tertiary [ 1l-131 alkyl and chlorides. Similar studies have involved several series of various dimethylalkanes [ 14, 151 including 2,3dimethylbutane, 2,4-dimethylpentane and 2,5dimethylhexane. Investigations of dimethylalkyl chlorides involving both a tertiary (dimethyl) chloride and a separate isopropyl group are limited. Although SHIPMAN et al.[16] included 2chloro-2,3dimethylbutane in a study of the carbon stretching frequencies in alkyl chlorides, interpretations of spectra and assignments of frequencies were limited to the range of interest, i.e. 400-700 cm-‘. This study was undertaken in order to extend the work done on tertiary alkyl chlorides and on dimethylalkanes to a series of compounds containing both moieties, (CH3,CCl-(CHzLCH(CH& in order to make complete vibrational assignments for several compounds in that family. Also of interest was the development of a force field that could be used for other related comInfrared
pounds. ExPRRmENTAL
All i.r. spectra were obtained using a Nicolet MX-1 Fourier Transform spectrometer. During this work all wavenumbers were determined using an automatic digital mintout mode. All compounds studied were liquids at room temnerature. The liauid-state spectra for the 5OfMOOOcm-’ region were obtained using KBr plates or commercial fixed-path-length cells fitted with KBr windows. Commercial fixed-path-length polyethylene cells were used for the 2OtMOOcm-’ region. A~ontinuous dry air purge system was used to eliminate water vapor. Solid-state spectra were obtained using a commercial
Beckman VLT-2 cold cell fitted with NaCl windows. Because of the low vapour pressure of the samples, transfer of the vapor to the cold cell could not be accomplished. In order to obtain a solid, the sample was placed-between two KBr plates to form a thin film; then the nlates were nlaced directly into the cold ceh. Cooling the sample rapidly with liquid nitrogen resulted in an amorphous solid. Crystallization was brought about by annealing the solid at a temperature lO-2OY below the melting point. After crystalliiation occurred, the temperature of the sample was reduced to that of liquid nitrogen and the spectrum was obtained, All samples tested underwent crystallization. In order to obtain spectra in the region below 500 cm-‘, the NaCl windows of the cold cell were replaced by polyethylene windows. The sample was placed in a commercial polyethylene cell which was inserted into the cold cell. Rapid cooling with liquid nitrogen produced an amorphous solid which upon annealing yielded crystalline solids for ah samples tested. The temperature of the crystalline solid was reduced to that of liquid nitrogen and the spectrum was obtained. A continuous dry air purge system was again used to eliminate any water vapor. Following solidification, a vacuum was placed on the system to prevent further the formation of ice from water vapor. Raman spectra were obtained using a Spectra Physics 700 spectrometer equipped with a Coherent Radiation Labs CR-2 argon ion laser. The wavenumbers were read from a digital readout, accurate to between ?5 and f 10 cm-‘, depending on the slit width that was used. The sample of 2-chloro-2,3-dimethylbutane was obtained from Albany International and had a stated purity of %%, which was verified by gas chromatoaranhv. Both 2-chloro-2.~diiethyhYentane and 2-chloro5,S:dimethylhexane were obtained-from Chemical Samples Co. Since the purity of neither sample was certain, both were purified by vacuum distillation. Subsequent gas chromatography showed the purity of both the 2chloro-2,4-dimethylpentane and the 2-chloro-2,5dimethylhexane to be 100%. CAL.CULATIONS
Normal coordinate calculations were made with 1123
1124
G.
A.
CROWDER and M. T. RICHARIWN
a DEC PDP-10 computer. The vibrational problem setup utilized the FG-matrix method of WILSON 117, 181. The computer programs written by SCHACHTSCHNEIDER[19, 201 were used for solution of the vibrational secular equation (VSEC), the calculation of the G-matrix (GMAT) and for least-squares refinement of certain force constants to fit the calculated frequencies to the observed frequencies (FPERT). The initial force constant matrix was set up by the use of a program written by CROWDER and PoTr~~[21]. The molecular parameters used were: C-C = 1.54& C-H = 1.09 A, C-Cl = 1.77 A, all angles were assumed to be tetrahedral (109.47”), and atomic weights used were: Cl = 35.453, C = 12.01115, H = 1.00797.
RESULTSANDDISCUSSION 2-Chloro-2,fdimethylbutane SHIPMAN et al. [ 161 included 2-chloro-2,3dimethylbutane in a study of characteristic carbon-chlorine stretching frequencies of primary, secondary and tertiary alkyl chlorides. Although the entire redrawn liquid-state i.r. spectrum was included in the paper, considerations were limited to the carbon-chlorine stretching frequency only. Further, neither Raman nor solid-state i.r. spectra were included in the study; therefore, liquid- and solid-state i.r. spectra (Figs. 1 and 2) and liquidstate Raman Spectra (Fig. 3) were obtained and are given in this work. SHIPMAN et al. reported C-Cl stretching frequencies at 611 and 569 cm-’ which he attributed, respectively, to the TCHH(C,) and T,,, (C,) conformers (Fig. 4). Their assignments were substantiated in this work. Examination of the solid-state i.r. spectrum reveals that the 569 cm-’ band is present in the spectrum of the crystalline solid, while that at 611 cm-’ is not. This evidence shows that the THHIr conformer is the one present in the crystalline solid. As an aid to vibrational analysis, normal coordinate calculations were included in this work. The beginning force constant values were compiled from branched alkanes[l9] and from tertiary alkyl chlorides[ll] and were used to make zero-order calculations. Observed frequencies from i.r. and Raman spectra were matched to calculated frequencies with an average difference of 8.1 cm-‘. Subsequent refinement of force constants eventually yielded an average error between observed and calculated frequencies of 6.2 cm-‘. Several low-wavenumber values were not fitted well, and an additional force constant, F,, was included. Only one more computer run was necessary. In that final run, 12 force constants of a 40 parameter modified valence force field were adjusted to fit 63 frequencies below 1500 cm-’ with an average error of 5.5 cm-‘. Eventually, three conformers of 2chloro-2,4-dimethylpentane and three conformers of 2-chloro-2,5_dimethylhexane were included and
calculations were made for all three compounds simultaneously. The observed and calculated frequencies of the two molecular conformations of 2-chloro-2,3dimtthylbutane are shown in Table 1. Of 63 assigned frequencies, 12 were unique to the l’HHH conformer and 12 others to the TCHHconformer. Only one band, that at 1069 cm-‘, was not assigned as a fundamental. Since both possible conformers of this compound were considered, this band cannot be attributed to a fundamental vibration but can be assigned as a combination band. The potential energy distribution as represented by symmetry coordinates accompanies the calculated frequencies in Table 1 and can be used to interpret the computer assignments of those frequencies in terms of symmetry coordinates. Shipman et al. reported bands at 743 and 508 cm-’ in the i.r. spectrum of this compound, which were labelled “unassignable at present”. Computer calculations predicted frequencies close to the values in question. A frequency calculated at 742cm-’ (73% C-C stretch and 25% CH3 rock) for the THHH conformer only was assigned to a 755 cm-’ band, while the corresponding frequency calculated at 737cm-’ (81% C-C stretch and 15% CH, rock) for the TCHH conformer only was assigned to a band at 741 cm-‘. The observed band at 508 cm-’ was assigned to mixed modes calculated near 502cm-’ for both conformers. The remainder of the computer assignments are presented in Table 1 without comment here. 2-Chloro-2,4_dimethylpentane and 2-chloro-2,5dimethylhexane Each of the next two compounds in the family, 2-chloro-2,4_dimethylpentane and 2-chloro-2,5dimethylhexane, can exist in a large number of rotational isomeric forms. Initial efforts to identify the major stable spectroscopically distinguishable forms began with the generation of liquid- and solid-state i.r. spectra (Figs. 5, 6, 8 and 9) and liquid-state Raman spectra (Figs. 7 and 10) for each compound. Two bands were apparent in the carbonchlorine stretching region of the liquid-state spectrum of 2-chloro-2&dimethylpentane. The band at 628cm-’ falls within the typical range for TCHH[161 and was assigned to that conformer. Likewise, the 573 cm-’ band was assigned to a T,,, conformer for the same reason. However, inspection of all conformers in which five carbon atoms are coplanar reveals that two THHH forms are possible, which are designated here at THHH and T&.,, (Figs. 11 and 12). This evidence suggested two possibilities: (1) The two observed bands account for two conformers only (in which case, the 573 cm-’ band is due to either the THHHor the T;I&. (2) The two observed bands account for three
112s
Conformational analysis of (CH,)FCl~CH3,-CH(CH,)z
I E
x
SAA Vol. 38. No. II-B
1126
G. A. CROWDERand M. T.
F~~~RDs~N
Conformational analysis of (CH32CCI-(CH3,-CH(CH32
600 cm-’ 400
800
1400
200
1127
1200
1000
Fig. 3. Raman spectrum of 2-chloro-2,3_dimethylbutane liquid.
conformers
THHH
(in which case, the 573 cm-’ band is due to both the THm and the T;I&. Further, because the 628 cm-’ band disappeared from the spectrum of the annealed solid, it was concluded that the crystalline solid was composed of a THHHconformer. Since only one conformer is usually present in the crystalline solid, it remained to be determined which of the two possible forms, THHHor T;IHH, is the one actually present in the solid.
TCHH
Fig. 4. Conformers of 2-chloro-2,3-dimethylbutane. Cl = chlorine, Me = methyl.
Table 1. Observed and calculated wavenumbers for 2-chloro-2,3-dimethylbutane
Anled.&
solid
solid 1468s 146Om
1456m
13% VW
l3JJ
VW
131521
1198w
1462s
co.1442sh 1393m 1381w 1371vs
1321nw
1460s
1454lILs
1440~ l391m 1380s
1439Ire -l379 vs
1370vs
1372vs
1320nw
1238vs 1240VW 1221m.l 1221* 1194In? 11% w
TomOmfonmti
~calfmtial
Iu -led
cal$
(a
)sym.
1467
1458 1458 1456 1455 1455 1454 1454 __
1363
I.393 1385 l3JJ 1371 1363
1329m
1336
-1224uw 1196w
__ 1220 1201
P.E.D. GY 3(JJ).100.2) 3(89) 3(87) 3(92) 3(92) 3(92) 3(93) 304) 4(80),2(25) 4m* 2a5) 4(93) 4(%)
Qlcl (a ) 1465 1458 1458 1456 1455 1455 1454 1452 1392 1384 1378 1371 1356
P.E.D. RF X80) X89) 3&w 3(91) 3(92) 3(92) 3(93) 3@4) 4(79),2(25) 400)~ ~(14) 4(89) 4(91),2w 6(59),4Ul)
6(67),4(11) 1248 10(36),206) -2(48),lO(18). 1190 ll(16).6(10)
2(52),lO(28)
1128
G.
A.CROWDERand MT.
RICHARDSON
Table 1. (Contd) b
Iu
~~1157 sh
(an )sym.
L157m
1163 m
1153
a'
lW&
1149 s
1131
a'
lO(57).2(17)
1159 w
1146 8
L146 s
ll3Onw
1129 w
1129vs 1100nw
1088 US
LOa8m
1070 w
lC69m
1069m
1050 w
1050 m
1049m
943m
-11Olm --
6(19),
__ 1110
a"
2(4&10(16).
__
Tm
'Zcmfonmth
&lEl (a )
P.E.D.
CO=
-1152
lO(W,
1139
lO(49).2(17)
2W)
-1104
lO(44).2(31),6Ul)
1048
10(55),6(18)
506 + 568 = 1074 1051m
1054
10(64),6(20)
999 VW
998 VW
1009VW
998
lO(87)
998
%lw
96ovw
962 w
973
lO(88)
972
lOW lO(83)
945Iw
945 w
947 m
944
lO(81).20.5)
943
10(80),2(14)
922 w
922 VW
920 rat?
927
10(69),2W
925
10(63),2(31)
911 VW
9l3 _-
2(52),lO(47)
898
2(59), lO(47)
880
2(57).1004)
871
2(65),lO(30) 2(73),lO(25)
918 w 882 m
P.E.D. UY
c=lfl
Liquid 1159 w
canfmtim
888 m
883nw 878 IIW
-879 m 754vs
--
756 m 741 m
755 IILS 756 m 741m
741m
--
742 -_
612 vs
612 s
611~x3
--
__
568 vvs
56anrs
568nm
567 I~EI
576
1(97),l2(26)
--
507 s
506m
506w
502 m
502
1(35).603, 20.3).12w 11(69),2(13)
503
-737
2(81),lO(15)
619
1(98),12(31) 6;:wj 11(32),
--
462w
wvw
460
450
427 nw
429 w
397 s
397 m
428 _-
423 __
357 s
358 m
__
__
349
348
336
x2(89),ll(17)
303
11(76).12(M)
294
12(85).ll(10)
273
12(51),ll(40)
245
14(87),ll(11)
255
‘W’;.
242
14(96)
243
14(97)
241
14(98)
241
14(95)
241
14(92)
240
14(96)
212
11(86),14(12)
221
171
12(72),6(27)
178
14(41),ll(35).609) l2(69),ll(42)
226 m
eneqyofless
ll(53).l2(16),2(10)
407
ll(52).1(15),12(14)
353
ll(61).12(32)
l5(97)
85 kmn5htions to thepotential the follauingdefinitions:
11(79),lO(12) 428
thm10%arenot
--
82
12(22), 11(16),
15(98)
included. lhe cmrdinatenurbers refer to
1 C-Cl stretch
7
M2"p
13 c-c-c bend
2 c-c stretch 3 CH3 antisym.deformation
a 9
Gi2twist CZ-$rock
14 CN3 torsion
4 CH3 syramtricdeformtim
10 CH3nxk
16 C-C torsion
596 C-H bend
11 cc3tmd 12 c-c-Clbend
17Q$=w
Analogous to 2-chloro-2&dimethylpentane, only two bands were apparent in the carbon4rlorine stretching region for Zchloro-2,5dimethylhexane. The band at 626 cm-’ was assigned to TcHH; that at 561 cm-’ was assigned to THHH. Once again, the 561 cm-’ band could be due to THHH, to Tr&.n.r,or to both. Likewise, the band at 561 cm-’ was observed in the solid-state spectrum, indicating that again one of the two possible THHH conformers is present in the solid. Consequently normal coordinate calculations were initiated in an attempt to determine which of the above alternatives was correct. Although neither compound exhibits symmetry, symmetry
15 cH2c1 torsion
coordinates were developed as an aid for interpretation of computer assignments. Force constants were transferred from 2-chloro-2,3dimethylbutane. Since both compounds under consideration include methylene (-CHT) groups not present in 2-chloro-2,3_dimethylbutane, additional force constants for this group were included. Zero-order calculations and subsequent assignments of observed to calculated frequencies were carried out. The resultant average difference (error) between observed and calculated frequencies was 8.1 cm-’ for all six molecules from the two compounds. Since all six molecules utilized the same force
Conformational analysis of (CHs)2CCI~CH3,-CH(CH,)2
1129
1130
G. A. CROWDERand M. T.
&CHARDSON
Conformational analysis of (CH,)zCCI-(CH&-CH(CH~)z
1131
l-
,
u,
1 800
*
I
600 cm-’ 400
I
I
.
200
Fig. 7. Raman spectrum of 2-chloro-2,4-dimethylpentane liquid.
field and since the development of a force field with general application within the family of compounds was desired, all further computer calculations were carried out on the entire group of conformers simultaneously. The tirst such leastsquares refinement lowered the overall average error for the group from 8.1 to 6.9 cm-‘. At that time it was noted that the individual average errors of all molecules except the THHH and the T&M conformers of 2-chloro-2,4dimethylpentane were 6.5 cm-’ or less. Such a bimodality in errors of individual molecular conformations was unexpected and suggested that perhaps one of the THHH conformers of 2-chloro-2&dimethylpentane was favored over the other. In order to test the hypothesis, computer input data for the two THHH conformers (THHH and Tr!r,r.,) were separated and a least-squares refinement was made for each independently to achieve the best possible fit by adjusting the same set of force constants. The resulting average error for the THHHconformer was 5.7 cm-’ and that for TkHH was 4.9cm-‘. Each of the two force fields generated in the independent refinements was then used to make individual zero-order calculations for the four remaining conformers. It was anticipated that if one of the THHH conformers under consideration were indeed superior to the other, the average error produced by zero-order calculations using its force ‘constants would be significantly lower than the corresponding error generated when force constants of the alternative conformer were used. Unfortunately, average errors so produced showed too little difference to dis-
tinguish conclusively between the conformers in question. Since neither the THHHnor the T;IHH conformer could be eliminated from consideration, normal coordinate analysis proceeded on all conformers. In order to develop a force field with truly broad application, the THHH and TcHH conformers of 2-chloro-2,3dimethylbutane were added to the group of molecules already under consideration and the least-squares refinement process was continued. In the final run, seventeen force constants of a 48 parameter modified valence force field were adjusted to fit 255 frequencies below lSOOcm-’ with an overall average error of 6.1 cm-‘. The resulting force constant values are given in Table 2. From the relatively low average error, it is reasonable to conclude that the resultant force field is equally applicable to the three compounds considered. This is a little surprising because the methyl-methyl or methyl-chlorine interactions are different in all three compounds. Indeed, the THHHconformer of the butane is a true H’ conformer, i.e. the Cl atom bisects a C-C-C angle, as for PH’ conformers, whereas the 4methyl group is forced into 1,3-parallel repulsion with either the 2-methyl or the chlorine in the two THHH conformers of the pentane. On the other hand, there is essentially no such interaction in the hexane conformers. The observed and calculated frequencies of 2chloro-2,4-dimethylpentane are presented in Table 3 and those for 2-chloro-2,S-dimethylhexane are shown in Table 4. The potential energy distributions accompanying the calculated &&en-
1132
G. A. CROWDER and ht. T. lb%ARLWN
Conformational analysis of (CH,)*CCI~CH3,-CH(CH,)2
-2
c
-
1133
G. A. CROWDER and M. T.
RICHARDSON
-
/
J Fig. 10. Raman spectrum of 2-chloro-2,Sdimethylhexane liquid.
T’HHH
TCHH
Fig. 11. Conformers of 2-chloro-2&dimethylpentane for which calculations were made. Cl= chlorine; Me= methyl.
TCtfH
Fii. 12. Conformers of 2chloro-2,5diietbylbexane for which calculations were made. Cl = chlorine; Me = methyl.
ties can be used for explanation of computer assignments. Inspection of the data consolidated in Tables 3 and 4 sheds little light on the question of which THHH isomer is responsible for the vibrational bands present for the solid. It is readily obvious that calculated frequencies for the THWHand Tr!u.u., conformers show strong similarities. This is true for both 2-chloro-2&dimethylpentane and 2chloro-2,Sdimethylhexane. When these similarities are considered together with the inconclusive THHH carbon-chlorine stretching data, it appears that there is insufficient evidence to draw conclusions regarding the presence or absence of the two isomers beyond a statement that at least one of the two must be present. Examination of Tables 3 and 4 reveals that the three conformations considered for each compound adequately account for the observed frequencies. For 2-chloro-2,4_dimethylpentane, eleven bands are due solely to the THHH conformer(s) and nine to the TCHH conformer. Likewise, nine bands were assigned exclusively to the THHH conformer(s) and nine bands to the TcHH conformer of 2-chloro-2,Sdimethylhexane. Furthermore, only two observed bands of each compound were unassigned in the computer calculations. The accumulation of evidence cited above suggests that the conformations being considered are the major ones present in the two compounds. The unassigned bands of 2-chloro-2,4dimethylpentane were attributed to summations. It is also possible that those bands as well as the unassigned bands of 2-chloro-2,5-dimethylhexane are due to conformations not considered in this
Conformational
analysis of (CH&Xl+ZH&-CH(CH,),
1135
Table 2. Force constants for (CH3,CCl_(CH3,-CH(CH,), Coordinate(s)
Force Constant
Group
Involved
Atom(s) cormnon Valuea
Standard Error
Stretch Xr Kd Rs KR
C"3 C"2 C-CH-C
KRl
C"2-C"l.2 CH-CH3
RR(X)
C-C-CL
C-Cl XX Stretch-Stretch --
C-H
4.699
C-H
4.546
C-H
4.046
c-c
4.331
c-c
4.623
c-c
4.189
C-Cl
3.231
C
C"3 C-CH2-C
C",C" C".C"
C
0.016
c-c-c
cc,cc
C
0.101
c-ccl-c or C-C-C-Cl C-C-Cl
cc,cc
C
0.320
CC,CCl
C
0.550
C"3 C-CH3
"C"
0.533
0.001
CC"
0.607
0.002
C"2 C-CE2-C
"C"
0.510
CC"
0.656
c-c-c
ccc
1.130
c-c3
ccc
0.713
0.006
C-CH-C
CC"
0.713
0.006
c-c-a
ccc1
0.982
C-CH3
cc,cC"
c-c
0.134
0.011
C-CH2-C
CC,CCB
c-c
0.382
0.013
C-CH2-C
C
0.137
0.014
c-c-c
CC)ccli cc,ccc
c-c
0.394
0.011
FRf
C-C-Cl
CC,CCl
c-c
0.075
FXE
c-c-a
CC1,CCCl
C-Cl
C-C-Cl
ccl,ccc
C-CH3
CC”,
C-CH2-C
FRX Bend H a "6 "6 H -I H w "e "S "_:
0.064
Stretch-Bend -FM FRI F' RY FRW
0.400
C
-0.330
CC”
c-c
-0.029
0.002
CC” ) CC”
c-c
0.003
0.003
c-CH2-c
CC”,
CC”
C-H
0.046
0.004
F+ F YW F;
c-c3
ccc,
ccc
c-c
-0.041
C-CH2-C
CC”,
CCC
c-c
-0.031
c-ccl-c
ccc1.ccc1
C-Cl
-0.050
F_ W1
c3-Cl
ccc.ccc1
c-c
-0.065
ft w
c*-c-c-c+
c*cc ,
c-c
-0.011
fwg
c*-c-c-c+
c*cc ) ccc+ L gaucheb
c-c
0.011
CH2-CH2
"CC,CC” Ltrans.l
c-c
0.022
0.005
c-c
-0.021
0.005
C
0.004
0.003
C
-0.009
0.004
FXU Bend-Bend -F6 F F;
fYt fB Y
CH2-CH2
fyt'
C*-CH2-C+H2
fyB'
C*-CH2-C+H2
ccc+ L trams’
xc*-CC+" lgaucheJ
0.008
1136
G. A. CROWDER and M. T. RNXGuXON Table 2. (Contd) Coordinate(s) Involved
Group
Force Constant
;k~;;) Value=
C-c-m2
CCC,CCH ltransl
C-C
C-C-CH*
ccc, CCH
c-c
-0.052
Standard E?XOr
0.040 0.005
lgauche~ CH2-C-Cl
HCC,CCCl LtransJ
c-c
0.070
CH,-C-Cl
HCC,CCCl Lgauche~
c-c
-0.121
C-C-C-Cl
CCC,CCCl [tram J
c-c
0.041
C-C-C-Cl
CCC,CCCl Lgauche'
c-c
-0.024
CH3-C-
or
c-c
0.012
C-C
0.023
0.015
-CH2-CH*-
(C)2CCl-CH2-
%&retching constants are in units of mdyn/A; stretch-bend constants are in units of mdyn/sad; bending constants are in units of ndyn i/(rad)'.
Table 3. Observed and calculated wavenumbers for 2-chloro-2,4-dimethylpentane
=
Liquid
14648
1469vs
1456 s
1456 s
1468vS
1456 s
1441m
Annealed Calq solid (an ) 1472 vs
1389 s
I.3888
1370 w8
1369 vvs
Gel (a )
TaCm&xmtti
P.E.D. e/.Y
"41 (an )
1472
3(45),j(24), 17(1'3>
1471
P.E.D. W 3(4;;il:)(26),
1460
3(81)
1460
3(81)
1460
3(81)
1457
3(89)
1457
3(81)
1460
3(81)
1456 146ovs r 1456
3(91)
1456
3(91)
1456
3(90)
1456
3(91)
1456
3eJO) 3(91)
1455
3(91)
1455
3(93)
1454
3(91) 3(93)
1455
1454 1452
3(94)
1452
3(94)
1452
1445
3(49).5(36) 559 + 867 = 1426
1448
3(49).X36)
1445
3(91) 3(52).5(33)
1380 1379
4(93)
1380
4(93)
1380
4(93)
404)
1379
4(94)
1379
1378
4(90), 2Ul)
1378
4(91)
1377
4W) 4(93)
1368 ws
1371
4(96).2(11)
1371
4(95)
1371
4(95)
1361 s
1351
7(41) 6(33),
1361
7(39) 6(31).
7w;i4;w)I
1331
2&V 6(56),2W)
1350 1329
6(56), 2(15)
1303
6(33),7(31),
1284
7(37).6(28).
1444mS 1389 ms 1384 s
1362 w
P.E.D. W
1470
1430 m 1389 vw
T~Cmformtim
TmCc&mticn
IR
lkamealed Solid
2&d
1454
3(91) 3(93)
1337w
1327
1306 w
1298 w
1301 w
1306 nw
1288
607)s 2(15) 6(3%&W)
1265 VW
1264 m
1264m
1264 vs
1244
8Wil;,(26’,
1249
8(33) 2(28). 1257 lo&, 6(12)
2~.~~~;(27),
1226 vw
1222 nw
1223m
1226 ws
1222
Z(39).lO(31)
1217
2(52), lO(28)
1189 In?
1186 nw
1188 m
1188 m
1186
10(32),2(20), 904). 6(13)
1208
10(29),2(28), 1226 804) 2(27),lO(26). 1196 9Ul). WO) 10(37),2(28)
--
2($(3‘&(26),
--
1174 w 1151 m
ll39nw 1103 w
1155 s
1170 Ins
1169 s
1165
2(33),1009). 6(13),8(10)
1150
1154 vs
1158s
1136
'NW',,
2W) s
1142
2(17),8W)
WG), 7-U)
10(28),2(20),w
w+; I 9w I
1146llm 1145 s
_-
_-
__
1145
2(;;&10(14),
ll36m
__
-_
__
1128
lo;:mj 2(12),
1088
1094
-_
__
1059
1064
1101 ml 1098m
1081m
9
1078 m
1136 m 1103 m 1094 m 1079 m
1105 m __ 1079 n.3
lo@), 2(22), 8(17),6(16)
-1090
10;Wj
2(27). 1058
lWWj
2(18),
'Oi:O;j2(34),
1137
Conformational analysis of (CH~)#XI-(CH&CH(CH3~
1023 V-VW 1026 VUJ 989 w
990 nw
989 m
1031V-VW __
985 aw
948m
94s VW
986 m
573 + 445 - 1018
__ 1003
__ 1001
lO(81)
lO(J9)
974
lO(J4).2(11)
976
l;;W9],2(14),
974
10(75),2(U)
955
lO(49).9(30)
972
lO(65).2(12)
953
'Wj
908),
947 w
951 nw
948
10(55),2(35)
931
10(67),2(28)
942
10(53),2(40)
935 w
935 Iw __
932 __
lO(63).2(32)
926 _-
10(57),2(31)
929
10(59),2(30) lo(%), 2&O)
921
10$:Wj 2(3J).
928 --
903
2(52),lO(4J)
--
927 w 922 w
928 w 919 w
917 m
921
876 w
876 cw
__
_-
,868"
867 w
865 m
885
844m
842m.I
843w
84&m
835
2(60).lO(17)
811 s
80911~
808111
798 __
2CJ9)
073 IIW
1006 __
lO(80)
8-42 2(57),lO(22) 790 2(79)
835 __
2(61). lO(l8)
__ __
777
2(82)
621 __
l(100).12(31)
786 m
785 w
788 "
805 m __
630 m
629 m
628 m
-_
__
576 vvs
573 s
570 s
559 m
562
l(126)
560
l(137)
512 vs
507 V\NJ --
510
514
ll~~~W)2(20).
516
11(33),2(17), -13(17),l2(12)
473 m
472
_-
__
471
11(49),l(22)
449m
44s
447
445
6(55).ll(19)
442
6(58),ll(18)
448
6WilU23).
__
415
406
ll(J8)
406
ll(80)
408
i1(68),6(U)
380 ms
382
383
366
12(85),ll(11)
386
11(59),12(25)
390
11(~~Nh)12(20),
356
410 nw
360 s
356
334
12(50),ll(4.4)
344
12(80).ll(26)
346
12(50),ll(45)
328m
328
320
11(64),12(25)
305
12(56).ll(32)
311
11(65),12(32)
298 m
303
290
282
12(43),ll(30)
290
12(69).ll(28)
263 ms
263
270
252
12~~~W)11(32),
--
b181 m
243 241
14(99) 14(98)
244 241
14(94) 14(94)
246 243
14(81) 14(99)
240
14(96)
240
14(88)
241
14(98)
236
14(82),12(10)
239
14(88)
239
14(95)
235
12~;;Wjj14(1J),
132
12(50),l3(40)
132
13(43),11(28), 12(22)
81
"$:wj
55
16(72).15(23)
16(16),
146
13(41).ll(31)
ww.
75
15~~~~i~9W),
84
“;:89j
55
16(76),1507)
59
16(72),15(23)
a See note a, Table 1.
b Not used
inccoputerrefinenent.
Table 4. Observed and calculated wavenumbers for 2-chloro-2,Sdimethylhexane
1469ws
1453 w
1469vs
1452 s
5w~iL&0.
1476
‘v+%3’:5”‘,
1462
3(73),5W)
1462
1459 1456
3(82)
1459
3(83)
1456
1471 ms
1476
1464IW
1453 s
1444m
1476
5wj(;$:”
3(73).501)
1462
3(72), 5&l)
3(82) 3FJ3
1459 1457
3(82) X85)
14%
3(91)
1456
3W)
3(89)
1456
3(91) 3(89)
1456
1456
1455
3(91)
1455
3(87)
1455
3(87)
1455
3(82)
1454
3(93)
1454
3(94)
1454
1452 1435
3W) 5(5;)(ioJ(18),
1452
3(94)
1452
3(93) 304)
1435
5Wio;JW.
1436
5i5io;J(18),
I
G. A.
1138
CROWDER
and hf. T.
bCHARDSON
Table 4. (Contd)
1393 1384 1378 1371 l358
1334
4(69).2~27) 4(91),204) 4(95) 4(95) 6(36).7(24), 4(18),2Cl6) 6$$gj 7(3l),
l304m
1317
6$;0ij7(36),
1317 6$6ij 7(36), 1315 7$;Wj 6(32),
7;0Qj 8(W.
1263 7(45),2(20)
l39ovs
l3a6vs
13a5vs
I.382 s
I.370 w
l37Ows
l369ws
l370vvs
134Onw
1338nw
1339IIW
1334w
1393 1385 1378 1371 1358
1328ow
1328m
1328w
1305nw
1305m
l305m
4(69),2(27) 4(91),2(14) 4(95) 4(95) 6(35),7(24), 4(18).2(16) 1334 6$0& 7(31),
1393 1385 1377 l371 l358
4(69),2(27) 4(91),204) 4(96) 4(%), 2(12) 6(36),7(24), 4(17),207) 1333 6$:'2ij 7(26),
1275VW
I.269 w
1269w
I.272 nw
1271
1243w
I.241 m
l241m
I.243 m
1237
1219w
1216m
12171118
1220m
1214
8(30),7(27). 2(B), 6(12) NW;], 2(31),
1249 8(4;(il;(17),1259 .7(39), 2(19), 8(10).6(lO) 1214 2(4f;il;~C32), I.214 27(Wj lO(27).
1181m
1187nw
1189tn
1192m
I.200 WW',, 2(26),
1187 8(4;:ioO(23).1194 8(25),lO(23).
1170m
1169sh
1169m
1168nw
1175
1170 8(3;(&&(28). 1173 8(50),9(23)
1150m
ll54m
1156118
1153m
1149
__
1140Ill 1134m
1134m
1130m cu.1124 sh
1124VW
1120
1113nw
lx? m
1113m
1117
108onw 1055WI 1010w a.975
953 m 94Onw 920w
1102m
1102IM
108om
1080s
1054vvw 1055w 1010VW 1010VW 979 VW
979 w
972VW
972 VW
952vd 94ovw 920 w
952VW 939vv.4 920w
846ms
847m
846111
819 m 811 Iw 766w
817 sh 808111
819nw 808m 763IW 759Iw 626m 575 s 533
__
1093
1055w lOO8w 980m
1048 1004 987
_-
__
955w 936w 922Ew 917m
970 943 933 916 910
847m
861
10(42),8(23). 2(13) 2(69) 10(58),9(17)
1092 W;,
8(24), 1097 8;&2(26),
1048 2(69),lO(10) 1044 2(75) 1004 10(59),9(16) 1010 lO(72)
10(56),9(l9), 2W)
__
973
910
971 948 937 923 907
w5
849
2(55),lO(22)
849
2(53),lO(23)
969, 2W) 269). 9W)
803 ___
9(7l).2u.5)
819 781 __ -r
775 617 L-
970
2(52),10(44) 2(M), 10(4a
926
941 931
__
_805 786 _-_
‘SW, 2G33 2~821
563m __
561 __
l(132)
561 _-
l(131)
496
llW, WO), 13(20),2(10)
496
l;g;], 13(19),
462
11(26),l3(20). -6(19);2(10! l;?;;, 13(19), 471
469 8
469
469
460
444m
445
__
__
~a.421sh
421
410 m 394m
412 397
__ __
375 s 356nx
370 356
377 347
383 365 328 319 281
b310 b282
_422
__ _ll(93)
12(67),ll(27) 12(72),ll(27) 12(53),ll(33) 12(44).ll(39)
lO(%), 9(26) lO(83) 10(60),2(25) lO(63).2(30) 2(49),lO(47)
10(a) 10(77),2(16) 10(54),2(37) lO(51).2(44) 2(48).lO(42)
lO(82) 10(80),2(15) lO(61).2(32)
-_
759m 626m 576 s 533 502
b3llln¶ b282
1119 10(31),2(22), -8(10).6(10) 1113 2(38),10(24), 1119 7(33),10(32), 7(14),6(10) 2(22),8UO) -_ 1109 1;{4$, 208).
e
808111 762m __ __
628m 578VI5 534m 502m
2(23),
2(25) 6(U), 7ClO) xwj lO(251, 10(30),
_-
1078m
208). 600)
1167 lO(19) 6(14), -8d') __ 1145 lW&
-_
114.0 m
1113ills
8(56),9(3U
1269 8$:W;j2(21).
10(39),
__
453
ll(20).6(18), 11(35),6(19), W14). ml)
6$;;ij11(27), --
-_
416
11(46),6(25)
-_
388
Wj
383 362 327. 320 281
6W).
ll(93) 383 ll(90) E l2(83),ll(16) -l2(66),11(29)- 349 12(60),1106) 12(50),ll(33) 300 12(88).2(U) l2(43).ll(39) 263 14(38),11(28), W17)
Conformational
251
14&u)
251
14(82)
243
14(94)
243 242
14(99)
243 242
243 242
14(98)
14(99)
14(99) 14(99)
240
14(96)
240
14(96)
236
207
13(24), 11(18), L2(16), 140.5)
205
13(27). l2(20), 213 11(19), 14(14)
12(29), ~(25)~ y&‘, ll(12) *
127
15(37), 16(23), 13(17), ll(15)
139
15(40), 16(27). 13(U), ll(lO)
15(49), 16(32)
117
lpj
112
13(45), 11(17), 106 12(15), 16(10)
13(55), 1208)
56
16(63), l2(11).
62
16(76), 905)
47
l5(10) 16(71), 15(25)
48
16@4), 1500)
5s
12(18) *
16(66), 9(18), 12(10)
47
a See
I'bte a,
Table
1139
analysis of (CH&CCl_(CH&CH(CH32
16(68), 15(28)
138
14(99)
1.
b Not used in cmputlz refinanent.
work. No doubt rotations occur that produce conformers in which the skeletal carbons are no longer coplanar. Acknowledgements-The authors are grateful to The Robert A. Welch Foundation, Houston, Texas, and the Killgore Research Center for financial support of this work. REFERENCES
r11 J. K. BROWN and N. SHEPPARD, Trans. Faraday sot. so, 1164 (1964). PI G. A. CROWDER and W. Lm, J. Mol. Strut. 64, 193 (1980). 131 V. SCHEITINA and E. BENJZDEITI,Spectrochimica Acta 34A, 353 (1978). r41 Y. OGAWA,S. IMAZEKI,H. YAMAG&HI, H. MATSUURA, I. HARADAand T. SHIMANOUCHI,Bull. Chem. Sot. Jpn. 51, 748 (1978). 151 G. W. F. PARDOE, Spectrochimica Acfa 27A, 203 (1971). [61 I. HARADA, H. TAKENCIU, M. SAKAKIB~RA, H. MATSUURAand T. SIUMAN~IJ~HI,Bull. Chem. Sot. Jpn. so, 102 (1977). 171 G. A. CROWDER and M. R. JALILIAN, Can. J. Spectros. 22, 1 (1977).
[8] P. N. GATES, E. F. MOONEY and H. A. WILLIS. Spectrochimica Acta 23A, 2043 (1%7). r91 G. A. CROWDER and M. IWUNZE, Con. J. Chem. 55, 3413 (1977). WI W. J. MOORE and S. KRIMM, Spectrochimica Acta 29A, 2025 (1973). [ill G. A. CROWDER and C. HARPER, J. Mol. Stract. 68, 89 (1980). [l21 R. P. HIRSCHMANNand R. N. KNISELEY, U.S. At. Energy Comm. IS-641 (1963). [I31 N. T. McD~vrrr, U.S. Dept. Corn. Ojice Tech. Seru., AD 268,648, 1 (1961). [I41 C. TOSI and A. PINTO, Spectrochimica Acra 28A, 585 (1972). wd H. LUTHERand H. H. OELERT, .J. Anal. Chem. 183, 161 (1961). WI J. J. SHIPMAN, V. L. FOLT and S. KRIMM, Spectrochimica Acto 18, 1603 (1%2). [I71 E. B. W~SON, JR., J. Chem. Phys. 7, 1047 (1939). WI E. B. WILSON, JR., J. C. DIKIUS and P. C. CROSS, Molecular Vibrations. McGraw-Hill, New York (1955). and R. G. SNYDER,Spec[I91 J. H. SCHACHTSCHNEIDER trochimica Acta 19, 117 (1%3). Shell Development Co. m J. H. SCHACHTSCHNEIDER, Tech. Repts. Nos. 231-64 (1964) and 57-65 (1%5). Appl. Spectrosc. ml G. A. CROWDERand J. K. Pm, 33,649 (1979).