- Email: [email protected]
Infrared and Raman spectra of fluorinated ethanes part XVIII. 1, 1, 1, 2-Tetrafluoroethane
JOURNAL
OF MOLECULAR
Infrared
SPECTROSCOPY
17,
341-347 (1965)
and Raman Spectra of Fluorinated Part XVIII. 1 ,l,l,2-Tetrafluoroethane J. RUD NIELSEN
Department
Ethanes
*
AND C. J. HALLEY+
of Physics, University of Oklahoma, Norman, Oklahoma
The infrared absorption spectrum of gaseous CFI-CFH, between 309 and 6969 cm-r has been obtained with a Perkin-Elmer model 112 double-pass spectrometer equipped with CsBr, NaCI, and LiF prisms. The Ramen spectrum of the liquid at -70°C has been photographed with a three-prism glass spectrograph of reciprocal linear dispersion 15 d/mm at 4358.%.The vibrational fundamentals are tentatively assigned as follows: Species a’: 2934, 1464, 1427. 1298, 1103, 972, 343, 665, 549, 408, and 225 cm-r; species a”: 3013, 1182, 665, 539, 352, 225, and 129 cm-l. The two lowest fundamentals are taken from previous work by Danti and Wood. I. INTRODUCTION
Although t,he infrared spectrum of CFs--CFHZ undoubtedly has been obtained in more than one laboratory, the only published data appear to be those found in a paper by Danti and Wood (1) dealing with the far infrared spectrum and the barrier to internal rotation. No Raman spectral data have been reported. In the present paper the infrared spectrum of gaseous CF3--CFH2 between 300 and 6000 cm-’ and the Raman spectrum of the liquid will be reported, and an attempt will be made to assign the vibrational fundamentals. II. EXPERIMENTAL
RESULTS
The sample of 1 , 1 , 1,2_tetrafluoroethane was prepared in the laboratory of Professor J. D. Park at the University of Colorado. No information was available about its purity. The infrared absorption spectrum of the gas at room temperature was obtained with a Perkin-Elmer model 112 double-pass spectrometer equipped with CsBr, NaCl, and LiF prisms and a l-m cell. The Raman spectrum of t.he liquid at - 70°C was photographed with a three-prism glass spectrograph of reciprocal linear dispersion 15 A/mm at 4358A. An attempt to obtain the Raman spectrum of the gaseous phase yielded only the two strongest bands. No polarization measurements were made. The infrared spect,rum is reproduced in Fig. l-3. The Raman data are listed in Table I. * This work has been supported by the U. S. Atomic Energy Commission No. AT-(40-l)-1074. t Present address: Oklahoma Baptist University, Shawnee, Oklahoma. 341
under Contract
i
0
2
c .P x 0 ..c 14
20
40
60
80
FIG.
I5
17
1. Infrared
16
absorption
spectrum
23
24
1,1,1,2-tetrafluoroethane.
I rnnth ;n ~irrc.n.
‘“-we
of gaseous
Wwe
22
angth in Microns Numbers in cm-l
Cesium
25
I
bromide
26
28
prism.
UNIVERSITY OF OKL4HOMA
L*IORATOI”
CF3-CH2F
27
;
%
80
8100
E
6 c’
v
FIG.
2.
Infrared
absorption
spectrum
l,l,
1,2-tetrafluoroethane.
Length in Microns
of gaseous
Wave
Numbers
in cm-t
length in Microns
in cm-f
Wave
Numbers
Wave
Wave
Sodium
chloride
CF3-CH2F
OF
prism.
OKLAHOMA
UNIVERSITY
,ABO”ATOII
NOCI
J.D. PARK
SOURCE AND ,“I,11
0
1.5
ti
E
5.0
0
80
2000 (UIOO
z
E z e I-
._6 .-D
20
40
60
80
FIG.
1900
I
3. Infrared
5.5
I600 I
2.0
6.0
absorption
A
1700
2.5
spectrum
r7lmm
1600
3500
Wave
in cm-t
l,l,
4.0
2500
1,2-tetrafluoroethane.
Length in Microns
in cm-t
3.5 Length in Microns
Wave Numbers
Wave
of gaseous
6.5
3.0
3000
Wave Numbere
Lithium
fluoride
485
prism.
OKLAHOMA
L*lol*ToI” UNIVERSITY OF
LiF
J.D. PARK
CFy CH2F SO”RCs Mm S”“lTl
COMPOUND
SPECTRA OF 1, 1 , 1,2-TETRAFLUOROETHANE TABLE I RAMAN SPECTRUMOF 1,1,1,2-TETRAFLUOROETHME LIQUID AT - 70°C Wave number 358 cm-r 410 466 534 548 663 823 839b 968 1028 1063 1081 1178 1200 1290 1428 1461 2832 29QOc
Interpretation
Description& W s, sh VVW W m W VW vs, sh W vvw VW m, d w, d VW m, d VW, d s, sh W VS
a” fundamental a’ fundamental 2 x 225 = 450 A’? a” fundamental a’ fundamental a’ + a” fundamentals 2X410=82OA’ a’ fundamental a’ fundamental 2 X 534 = 1074 A’? a’ fundamental a” fundamental 539 + 665 = 1294 ? a’ fundamental a’ fundamental a’ fundamental 2 X 1428 = 2856 A’ a’ + a” fundamentals
BThe following abbreviations are used: s strong, m medium, w weak, v very, sh sharp, and d diffuse. b In the Raman spectrum of gaseous CF3CFH2 a strong sharp band was found at 841 cm-r. 0 In the Raman spectrum of gaseous CF&FH, a strong sharp band was found at 2984 cm-r. III. INTERPRETATION
The CF,CFH2 molecule may be assumed to have the symmetry C,, and the divide themselves into 11 of species a’ and 7 of species a”. The principal moments of inertia of the molecule have been calculated by Danti and Wood (1). They found the values 99.4, 186.4, and 187.0 amu A2, showing that the molecule is very nearly a symmetrical top. From the theory of Gerhard and Dennison (2) it is found that parallel infrared bands should have a P-R branch separation of approximately 15 cm-l and that the zero branch should have an intensity equal to 26 per cent of that of the entire band. Perpendicular bands should be fairly broad with only an indication of P&R structure. Infrared bands of species a” should be perpendicular, whereas bands of species a’ should have hybrid contours. Unfortunately, only the infrared bands at 352, 408, and 843 cm-1 have so well-resolved contours that their species are revealed with certainty. For this reason, and because of the absence of Raman polarization data, the assignment of the vibrational fundamentals given here must be regarded as in part tentative. 18 normal vibrations
NIELSEN
346
AND
HALLEY
The strong infrared bands at 3013 and 2984 cm-i can with confidence be interpreted as a” and a’ fundamentals, respectively, associated with asymmetrical and symmetrical C-H stretching. In the Raman spectrum of gaseous CF&FH2 only the a’ fundamental is observed, while in the Raman spectrum of the liquid the two bands appear to be unresolved, giving rise to a single maximum at 2990 cm-l. The infrared band at 1464 cm-i has a strong and sharp counterpart in the Raman spectrum. It is undoubtedly an a’ fundamental involving mainly CH2 deformation, The four strong infrared bands at 1427, 1298, 1182, and 1103 cm-l must be interpreted as fundamentals associated largely with C-F stretching. Three of these should belong to species a’ and one to species a”. All of the corresponding Raman bands are quite diffuse, as are most Raman bands arising from C-F stretching. However, the bands at 1178 and 1428 cm-i are more diffuse and weaker than the other two Raman bands, and one of these two most likely represents the a” fundamental. Somewhat arbitrarily the former has been so assigned. TABLE
II
FUNDAMENTAL VIBRATIONALFREQUENCIESOF 1 ,1,l ,2-TETRAFLUORETHANE Species a’ a’ a’ a’ a’ a’ a’ a’ a’ a’ a’ a” a” arr a” a” a” a”
Infrared (gas)a 2984
5
1464 8 1427 s 1298 vs 1103 vs 972 vs 843 vs 665 vs 549 vs 408 m 225d 3013 vs 1182 vs 665 vs 539 m 352 s 225d 120d
Raman (liquid)8 299Obvs 1461 s, sh 1428 VW, d 1290 m, d 1081 m, d 96Sw 839” vs, sh 663 w 548 m, sh 410 s, sh 2990 vs 1178 w, d 663 w 534 w 358 s -
-
8 For abbreviations used, see footnote to Table I. b In the Raman spectrum of gaseous CFaCFHz the measured wave number was 2984 cm-r. c In the Raman spectrum of gaseous CF3CFH2 the measured wave number was 841 cm-r. d This band was observed by Danti and Wood (1).
SPECTRA OF
1,1,1,2-TETRAFLUOROETHANE
347
The very strong infrared band at 972 cm-l has a weak but sharp counterpart in the Raman spectrum. It is interpreted as an a’ fundamental probably arising from a vibration involving mainly CH2 wagging. The very strong infrared band at 843 cm-l has a contour which indicates that it is a parallel band. It is very sharp and intense in the Raman spectra of both liquid and gaseous CF&FHz. It certainly represents an a’ fundamental. The corresponding vibration may be characterized as largely C-C stretching. The deformation of the CF, group may be expected to give rise to an a’ fundamental near 600 cm-l and to a’ and a” fundamentals near 550 cm-‘. The infrared bands observed at 665 and 549 cm-l are identified as the a’ fundamentals in question. With less certainty because of its sharp appearance in the Raman spectrum, the band at 539 cm-i is assigned as the corresponding a” fundamental. Of the remaining two a’ fundamentals one can be identified unambiguously with the infrared bands at 408 cm-1 which has a contour typical of parallel bands. The lowest a’ fundamental has been tentatively identified with the band at 225 cm-’ of indistinct contour observed by Danti and Wood (1). The vibrations associated with these two fundamentals may be characterized as rockings parallel to the symmetry plane. Of the remaining four a” fundamentals, two can be assigned with certainty. The strong infrared band at 352 cm-1 has perpendicular contour and a fairly diffuse counterpart in the Raman spectrum. It must be an a” fundamental associated with rocking perpendicular to the symmetry plane of the molecule. The infrared band at 120 cm-l observed by Danti and Wood (1) also is undoubtedly an a” fundamental associated with a torsional motion. There appears to be little basis for assigning the two remaining a” fundamentals. One of them, associated with out-of-plane rocking, probably lies below the wave-number range studied in the present work. Since the band at 225 observed by Danti and Wood has no typical contour, it is assumed tentatively that it represents overlapping a” and a’ fundamentals. The last a” fundamental is either very weak in both spectra or is also masked by one of the other fundamentals. We have assumed, somewhat arbitarily, that it overlaps the a’ fundamental at 665 cm-l. It is possible, however, that it lies higher and is represented by one of the very weak bands near 770, 885, and 1065 cm-‘. The assigned vibrational fundamentals are listed in Table II. RECEIVED May 15,196s REFERENCES I. A. DANTI AND J. L. WOOD, J. Chem. Phys. 30, 582 (1959). 2. S. L. GERHARD AND D. M. DENNISON, Phys. Rev. 43, 197 (1933).
OF MOLECULAR
Infrared
SPECTROSCOPY
17,
341-347 (1965)
and Raman Spectra of Fluorinated Part XVIII. 1 ,l,l,2-Tetrafluoroethane J. RUD NIELSEN
Department
Ethanes
*
AND C. J. HALLEY+
of Physics, University of Oklahoma, Norman, Oklahoma
The infrared absorption spectrum of gaseous CFI-CFH, between 309 and 6969 cm-r has been obtained with a Perkin-Elmer model 112 double-pass spectrometer equipped with CsBr, NaCI, and LiF prisms. The Ramen spectrum of the liquid at -70°C has been photographed with a three-prism glass spectrograph of reciprocal linear dispersion 15 d/mm at 4358.%.The vibrational fundamentals are tentatively assigned as follows: Species a’: 2934, 1464, 1427. 1298, 1103, 972, 343, 665, 549, 408, and 225 cm-r; species a”: 3013, 1182, 665, 539, 352, 225, and 129 cm-l. The two lowest fundamentals are taken from previous work by Danti and Wood. I. INTRODUCTION
Although t,he infrared spectrum of CFs--CFHZ undoubtedly has been obtained in more than one laboratory, the only published data appear to be those found in a paper by Danti and Wood (1) dealing with the far infrared spectrum and the barrier to internal rotation. No Raman spectral data have been reported. In the present paper the infrared spectrum of gaseous CF3--CFH2 between 300 and 6000 cm-’ and the Raman spectrum of the liquid will be reported, and an attempt will be made to assign the vibrational fundamentals. II. EXPERIMENTAL
RESULTS
The sample of 1 , 1 , 1,2_tetrafluoroethane was prepared in the laboratory of Professor J. D. Park at the University of Colorado. No information was available about its purity. The infrared absorption spectrum of the gas at room temperature was obtained with a Perkin-Elmer model 112 double-pass spectrometer equipped with CsBr, NaCl, and LiF prisms and a l-m cell. The Raman spectrum of t.he liquid at - 70°C was photographed with a three-prism glass spectrograph of reciprocal linear dispersion 15 A/mm at 4358A. An attempt to obtain the Raman spectrum of the gaseous phase yielded only the two strongest bands. No polarization measurements were made. The infrared spect,rum is reproduced in Fig. l-3. The Raman data are listed in Table I. * This work has been supported by the U. S. Atomic Energy Commission No. AT-(40-l)-1074. t Present address: Oklahoma Baptist University, Shawnee, Oklahoma. 341
under Contract
i
0
2
c .P x 0 ..c 14
20
40
60
80
FIG.
I5
17
1. Infrared
16
absorption
spectrum
23
24
1,1,1,2-tetrafluoroethane.
I rnnth ;n ~irrc.n.
‘“-we
of gaseous
Wwe
22
angth in Microns Numbers in cm-l
Cesium
25
I
bromide
26
28
prism.
UNIVERSITY OF OKL4HOMA
L*IORATOI”
CF3-CH2F
27
;
%
80
8100
E
6 c’
v
FIG.
2.
Infrared
absorption
spectrum
l,l,
1,2-tetrafluoroethane.
Length in Microns
of gaseous
Wave
Numbers
in cm-t
length in Microns
in cm-f
Wave
Numbers
Wave
Wave
Sodium
chloride
CF3-CH2F
OF
prism.
OKLAHOMA
UNIVERSITY
,ABO”ATOII
NOCI
J.D. PARK
SOURCE AND ,“I,11
0
1.5
ti
E
5.0
0
80
2000 (UIOO
z
E z e I-
._6 .-D
20
40
60
80
FIG.
1900
I
3. Infrared
5.5
I600 I
2.0
6.0
absorption
A
1700
2.5
spectrum
r7lmm
1600
3500
Wave
in cm-t
l,l,
4.0
2500
1,2-tetrafluoroethane.
Length in Microns
in cm-t
3.5 Length in Microns
Wave Numbers
Wave
of gaseous
6.5
3.0
3000
Wave Numbere
Lithium
fluoride
485
prism.
OKLAHOMA
L*lol*ToI” UNIVERSITY OF
LiF
J.D. PARK
CFy CH2F SO”RCs Mm S”“lTl
COMPOUND
SPECTRA OF 1, 1 , 1,2-TETRAFLUOROETHANE TABLE I RAMAN SPECTRUMOF 1,1,1,2-TETRAFLUOROETHME LIQUID AT - 70°C Wave number 358 cm-r 410 466 534 548 663 823 839b 968 1028 1063 1081 1178 1200 1290 1428 1461 2832 29QOc
Interpretation
Description& W s, sh VVW W m W VW vs, sh W vvw VW m, d w, d VW m, d VW, d s, sh W VS
a” fundamental a’ fundamental 2 x 225 = 450 A’? a” fundamental a’ fundamental a’ + a” fundamentals 2X410=82OA’ a’ fundamental a’ fundamental 2 X 534 = 1074 A’? a’ fundamental a” fundamental 539 + 665 = 1294 ? a’ fundamental a’ fundamental a’ fundamental 2 X 1428 = 2856 A’ a’ + a” fundamentals
BThe following abbreviations are used: s strong, m medium, w weak, v very, sh sharp, and d diffuse. b In the Raman spectrum of gaseous CF3CFH2 a strong sharp band was found at 841 cm-r. 0 In the Raman spectrum of gaseous CF&FH, a strong sharp band was found at 2984 cm-r. III. INTERPRETATION
The CF,CFH2 molecule may be assumed to have the symmetry C,, and the divide themselves into 11 of species a’ and 7 of species a”. The principal moments of inertia of the molecule have been calculated by Danti and Wood (1). They found the values 99.4, 186.4, and 187.0 amu A2, showing that the molecule is very nearly a symmetrical top. From the theory of Gerhard and Dennison (2) it is found that parallel infrared bands should have a P-R branch separation of approximately 15 cm-l and that the zero branch should have an intensity equal to 26 per cent of that of the entire band. Perpendicular bands should be fairly broad with only an indication of P&R structure. Infrared bands of species a” should be perpendicular, whereas bands of species a’ should have hybrid contours. Unfortunately, only the infrared bands at 352, 408, and 843 cm-1 have so well-resolved contours that their species are revealed with certainty. For this reason, and because of the absence of Raman polarization data, the assignment of the vibrational fundamentals given here must be regarded as in part tentative. 18 normal vibrations
NIELSEN
346
AND
HALLEY
The strong infrared bands at 3013 and 2984 cm-i can with confidence be interpreted as a” and a’ fundamentals, respectively, associated with asymmetrical and symmetrical C-H stretching. In the Raman spectrum of gaseous CF&FH2 only the a’ fundamental is observed, while in the Raman spectrum of the liquid the two bands appear to be unresolved, giving rise to a single maximum at 2990 cm-l. The infrared band at 1464 cm-i has a strong and sharp counterpart in the Raman spectrum. It is undoubtedly an a’ fundamental involving mainly CH2 deformation, The four strong infrared bands at 1427, 1298, 1182, and 1103 cm-l must be interpreted as fundamentals associated largely with C-F stretching. Three of these should belong to species a’ and one to species a”. All of the corresponding Raman bands are quite diffuse, as are most Raman bands arising from C-F stretching. However, the bands at 1178 and 1428 cm-i are more diffuse and weaker than the other two Raman bands, and one of these two most likely represents the a” fundamental. Somewhat arbitrarily the former has been so assigned. TABLE
II
FUNDAMENTAL VIBRATIONALFREQUENCIESOF 1 ,1,l ,2-TETRAFLUORETHANE Species a’ a’ a’ a’ a’ a’ a’ a’ a’ a’ a’ a” a” arr a” a” a” a”
Infrared (gas)a 2984
5
1464 8 1427 s 1298 vs 1103 vs 972 vs 843 vs 665 vs 549 vs 408 m 225d 3013 vs 1182 vs 665 vs 539 m 352 s 225d 120d
Raman (liquid)8 299Obvs 1461 s, sh 1428 VW, d 1290 m, d 1081 m, d 96Sw 839” vs, sh 663 w 548 m, sh 410 s, sh 2990 vs 1178 w, d 663 w 534 w 358 s -
-
8 For abbreviations used, see footnote to Table I. b In the Raman spectrum of gaseous CFaCFHz the measured wave number was 2984 cm-r. c In the Raman spectrum of gaseous CF3CFH2 the measured wave number was 841 cm-r. d This band was observed by Danti and Wood (1).
SPECTRA OF
1,1,1,2-TETRAFLUOROETHANE
347
The very strong infrared band at 972 cm-l has a weak but sharp counterpart in the Raman spectrum. It is interpreted as an a’ fundamental probably arising from a vibration involving mainly CH2 wagging. The very strong infrared band at 843 cm-l has a contour which indicates that it is a parallel band. It is very sharp and intense in the Raman spectra of both liquid and gaseous CF&FHz. It certainly represents an a’ fundamental. The corresponding vibration may be characterized as largely C-C stretching. The deformation of the CF, group may be expected to give rise to an a’ fundamental near 600 cm-l and to a’ and a” fundamentals near 550 cm-‘. The infrared bands observed at 665 and 549 cm-l are identified as the a’ fundamentals in question. With less certainty because of its sharp appearance in the Raman spectrum, the band at 539 cm-i is assigned as the corresponding a” fundamental. Of the remaining two a’ fundamentals one can be identified unambiguously with the infrared bands at 408 cm-1 which has a contour typical of parallel bands. The lowest a’ fundamental has been tentatively identified with the band at 225 cm-’ of indistinct contour observed by Danti and Wood (1). The vibrations associated with these two fundamentals may be characterized as rockings parallel to the symmetry plane. Of the remaining four a” fundamentals, two can be assigned with certainty. The strong infrared band at 352 cm-1 has perpendicular contour and a fairly diffuse counterpart in the Raman spectrum. It must be an a” fundamental associated with rocking perpendicular to the symmetry plane of the molecule. The infrared band at 120 cm-l observed by Danti and Wood (1) also is undoubtedly an a” fundamental associated with a torsional motion. There appears to be little basis for assigning the two remaining a” fundamentals. One of them, associated with out-of-plane rocking, probably lies below the wave-number range studied in the present work. Since the band at 225 observed by Danti and Wood has no typical contour, it is assumed tentatively that it represents overlapping a” and a’ fundamentals. The last a” fundamental is either very weak in both spectra or is also masked by one of the other fundamentals. We have assumed, somewhat arbitarily, that it overlaps the a’ fundamental at 665 cm-l. It is possible, however, that it lies higher and is represented by one of the very weak bands near 770, 885, and 1065 cm-‘. The assigned vibrational fundamentals are listed in Table II. RECEIVED May 15,196s REFERENCES I. A. DANTI AND J. L. WOOD, J. Chem. Phys. 30, 582 (1959). 2. S. L. GERHARD AND D. M. DENNISON, Phys. Rev. 43, 197 (1933).