""
Journa/ of Mo/eeu/ar Strueture
Elsevier Publishing Company, Amsterdam. Printed in the Netherlands.
]8]
THE MICROW AVE SPECTRA OF CHLOROBROMOACETYLENE,
CHLOROIODOACETYLENE, AND CHLORODIACETYLENE
ALF BJØRSETH, ELSE KLOSTER-JENSEN, K.-M. MARSTOKK AND HARALD MØLLENDAL
Department of Chemistry, University of Oslo, Blindern, Oslo 3 (Norway)
(Received September 18th, 1969)
ABSTRACT
The microwave spectraof35C]-C=C-79Br, 35C]-C=C-81Br, 37C]-C=,C-79Br,
37C]-C=,C-81Br, 35C]-C=,C-I, 37CI-C=,C-I, 35CI-C=,C-C=,C-H, and 37Cl-C=,CC=,C-H in natural abundance are reported. The mo]ecules were all found to be
linear.
The structure of chlorobromoacety]ene was obtained: r(C-CI) = 1.628:!:
0.005 Å; r(C=,C) = 1.209:!:0.008 Å; r(C-Br) = 1.790:!:0.005 Å.
The quadrupole coupling constants were obtained for the bromine nuc1ei of
chlorobromoacetylene, for the iodine nuc1eus of chloroiodoacetylene, and for 35Cl
of ch]orodiacetylene.
A least squares treatment yielded the rotationa] constants, vibration-rotation
interaction and l-type doubling constants for severallow frequency modes of the
three molecules.
INTRODUCTION
A number of structural studiesl has shown that the halogen-carbon and
carbon-carbon distances of symmetrical diha]oacetylenes remain almost unaItered
as compared with the corresponding distances of monohaloacetylenes. No structural work has previous]y been reported for unsymmetrical dihaloacety]enes. Since
these mo]ecules would be expected to possess a dipo]e moment, the accurate
method of microwave spectroscopy may be applied, and information about bond
lengths, quadrupole coupling constants, dipo]e moments, etc., obtained and compared with related compounds. For chlorobromoacetylene the complete structure
has been determined, showing that the bond distances are very similar to those
reported1 for other halo- and dihaloacetylenes.
In parallei with this work, the IR and Raman spectra2of the mo]eculeshave
been examined and completely assigned on the basis of a linear structure.
J. Mo/. Strueture, 6 (1970) 181-204
182
A. BJØRSETH, E. KLOSTER-JENSEN, K.-M. MARSTOKK, H. MØLLENDAL
Chloro-, bromo-, and iodo-diacetylene were prepared by Kloster-Jensen 3.
Their IR spectra4 have been completely assigned and the expected linear structure
confirmed. A force field calcu1ation4 has also been carried out and an electron
diffraction studyS of bromodiacetylene is now completed.
We have attempted to observe the microwave spectra of all three halogenodiaeetylenes but, in the case of bromo- and iodo-diacetylene, we were unsuccessful.
This is believed to be caused mainly by low dipole moments, inaccessibility of the
higher frequency spectral region (above 26 GHz), and the presenee of large quadrupole splitting.
EXPERIMENT
AL
Chlorobromoacetylene, chloroiodoacetylene and chlorodiacetylene were
prepared as described elsewhere3,6, purified by gas chromatography, and kept at
dry ice or liq uid air temperature when not in use.
A conventional Stark-effect speetrometer employing 50 kHz Stark modulation and phase-sensitive detection was used. A maximum field strength of about
4000 V cm -1 was attainable with this equipment. Frequency measurements were
carried out with a frequency standard having a stability of 0.05 p.p.m. and a calibrated communications receiver.
The spectra were obtained in brass cells utilizing a pressure of about 0.04
torr. The cells were cooled to -15 DC when Cl-C=C-Br and Cl-C=C-I were
studied. The spectral region 21.7-26.3 GHz was examined for these two molecules.
The spectral region 12.4-26 GHz was examined for the 3sCl speeies of
chlorodiacetylene. The 12.4-18 GHz and 22-26 GHz regions were studied for the
37Cl speeies. In the 12.4-18 GHz region, the spectra were studied at room tempe rature, while a temperature of -10 DCwas used in the high frequency spectral region.
All three compounds were found to be unstable under these conditions, and
the cells were therefore dosed with fresh sample at regular intervals.
MICROW AVE SPECTRA
The microwave spectra of Cl-C=C-Br, Cl-C=C-I, and Cl-C=C-C=C-H are
typical of linear molecules. They consist of groups of weak lines separate d by constant intervals.
The J = 11 ~ 12, 12 ~ 13, and 13 ~ 14 transitions were examined for
3sCl-C=C-79Br and 3sCl-C=C-81Br, and the 12 ~ 13 and 13 ~ 14 transitions
were studied for the corresponding 37CI speeies. Only lines belonging to the symmetrical (vs) and antisymmetrical (V4)bending modes2 were observed. The ground
state was not modulated at the field strength of about 4000V cm - 1. The spectra
are reported in Tab les 1-4.
J. Mol. Structure, 6 (1970) 181-204
MICROW AVE SPECTRA
183
OF HALOGENOACETYLENES
TABLE l
MICROWAVESPECTRUMOF 35C1-C=C-79Br
J-+J'
11 -+ 12
12 -+ 13
13 -+ 14
Vibrational
state
lib
F-+F'
Calc.
frequency
(MHz)
25/2-27/2
23/2-25/2
19/2-21/2
21/2-23/2
25/2-27/2
23/2-25/2
19/2-21/2
21/2-23/2
25/2-27/2
19/2-21/2
23/2-25/2
21/2-23/2
22247.95
22248.52
22249.56
22250.16
22258.18
22258.75
22259.79
22260.39
22302.58
22303.83
22304.92
22306.27
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
27/2-29/2
21/2-23/2
25/2-27/2
23/2-25/2
24102.03
24102.49
24103.42
24103.89
24113.00
24113.46
24114.39
24114.86
24104.34
24104.80
24105.73
24106.20
24109.35
24109.81
24110.74
24111.21
24161.44
24162.56
24163.28
24164.47
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
25956.08
25956.44
25957.28
25957.66
25967.88
25968.24
25969.09
25969.46
25958.55
25958.91
25959.76
25960.13
V4
Vs
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
2
2
2
2
Is
Is
Is
Is
Is
Is
Is
Is
=
=
Is
Is
Is
Is
=
=
=
=
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
O
O
O
O
l
l
l
l
l
l
l
l
O
O
O
O
O
O
O
O
2
2
2
2
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
14 =
14 =
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
l
l
l
l
O
O
O
O
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
14 =
14 =
14 =
14 =
-1
-1
= -1
= -1
= +l
= +1
= + l
= +l
O,
O,
O,
O,
:::1::2
:::1::2
:::1::2
:::1::2
-1
-1
-1
-1
+1
+1
+l
+1
- l
- l
14 =
14 =
-1
- l
14 = +1
14
14
= +l
= +l
14
= +1
Is
Is
Is
Is
=
=
=
=
O,
O,
O,
O,
:::1::2
:::1::2
:::1::2
:::1::2
-1
-1
-1
-1
+1
+l
+1
+l
-1
-1
-1
-1
Obs."
frequency
(MHz)
22248.03
22249.70
22258.38
22260.17
22302.82
22303.90
24102.16
24103.61
24113.10
24114.54
24104.43
24105.64
24109.53
24110.70
24161.76
24163.65
25956.24
25957.48
25968.06
25969.27
25958.72
25959.90
J. Mol. Structure, 6 (1970) 181-204
184
TABLE
A. BJ0RSETH,
E. KLOSTER-JENSEN,
K.-M. MARSTOKK,
H. M0LLENDAL
l (continued)
J-+J'
Vibrational
state
1'4
Vs
l
l
l
l
O
O
O
O
O
O
O
O
2
2
2
2
lib
F->-F'
Calc.
frequency
(MHz)
Obs.a
frequency
(MHz)
-
+l
14 =
14 =
14 =
14 =
+l
+l
+l
Is
Is
Is
Is
O, :J::2
O, :J::2
O, :J::2
O, :J::2
=
=
=
=
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
23/2-25/2
27/2-29/2
25/2-27/2
25963.98
25964.34
25965.19
25965.56
26020.18
26021.19
26021.66
26022.72
25964.22
25965.44
26020.55
26021.74
a :J::0.20 MHz.
b Negative l denotes the lowest, and positive l the highest frequency.
TABLE 2
MICROWAVE
SPECTRUM
OF 35CI-C"C-81Br
J-+J'
11 -+ 12
12 -+ 13
Vibrational
state
lib
F-+F'
Calc.
frequency
(MHz)
V4
Vs
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
2
2
2
2
Is = -1
Is = -1
Is = -1
Is = -1
15 = + l
15 = + l
Is = + l
Is = + l
Is = O, :J::2
15 = O, :J::2
Is = O, :J::2
Is = O, :J::2
25/2-27/2
23/2-25/2
19/2-21/2
21/2-23/2
25/2-27/2
23/2-25/2
19/2-21/2
21/2-23/2
25/2-27/2
19/2-21/2
23/2-25/2
21/2-23/2
22047.29
22047.78
22048.67
22049.18
22057.37
22057.86
22058.75
22059.26
22101.77
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
l
l
l
l
O
O
O
O
Is =
Is =
Is =
15 =
Is =
Is =
15 =
15 =
14 =
14 =
14 =
14 =
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
23884.62
23885.01
23885.81
23886.21
23895.54
23895.93
23896.73
23897.13
23886.96
23887.35
23888.15
23888.55
J. Mol. Structure, 6 (1970) 181-204
-1
-1
-1
-1
+l
+1
+l
+1
-1
- l
-1
-1
22103.76
22104.91
22102.84)
Obs"
frequency
(MHz)
22047.36
22048.76
22057.59
22059.02
22102.00
22103.20
23884.90
23886.10
23895.66
23896.89
23887.16
23888.32
MICROW AVE SPECTRA
185
OF HALOGENOACETYLENES
TABLE 2 (continued)
J-+J'
13 -+ 14
Vibrational
state
V4
Vs
1
1
1
1
O
O
O
O
O
O
O
O
2
2
2
2
O
O
O
O
O
O
O
O
1
1
1
1
1
1
l
1
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
O
O
O
O
2
2
2
2
14
lib
F-+F'
Calc.
frequency
(MHz)
= +1
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
27/2-29/2
21/2-23/2
25/2-27/2
23/2-25/2
23891.97
23892.36
23893.16
23893.56
23943.82
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
23/2-25/2
27/2-29/2
25/2-27/2
25721.90
25722.21
25722.93
25723.25
25733.67
25733.98
25734.70
25735.02
25724.42
25724.73
25725.45
25725.77
25729.81
25730.12
25730.84
25731.16
25785.80
14 = + 1
14 = + 1
14 = + 1
Is = O, ::1::2
Is = O, ::1::2
Is = O, ::1::2
Is = O, ::1::2
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
14 =
14 =
14 =
14 =
14 =
-1
-1
-1
-1
+1
+1
+1
+1
-1
- 1
- 1
-1
+ 1
14
14
= +1
14
=
=
=
=
=
Is
Is
Is
Is
= +1
+1
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
23945.39
23946.41
23944.79}
25787.05
25787.95
25786.66}
Obs."
frequency
(MHz)
23892.24
23893.46
23943.92
23945.10
25722.19
25723.29
25733.82
25734.85
25724.52
25725.67
25729.99
25731.04
25785.88
25786.90
" ::1::0.20MHz.
b Negative l denotes the lowest, and positive l the highest frequency.
TABLE 3
MICROWAVESPECTRUMOF 37Cl-C=:C-79Br
J-+J'
Vibrational
state
V4
F-+F
li b
Calc.
frequency
(MHz)
V5
Obs."
frequency
(MHz)
--------------------------
12 -+ 13
O
O
O
O
1
l
1
1
Is
Is
Is
Is
=
=
=
=
-1
-1
-1
-1
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
23326.73
23327.19
23328.12
23328.59
23326.90
23328.30
J. Mol. Structure, 6 (1970) 181-204
186
A. BJØRSETH,
E. KLOSTER-JENSEN,
K.-M. MARSTOKK,
H. MØLLENDAL
TABLE 3 (continued)
J-->-J'
13 -->-14
Vibrational
state
114
115
O
O
O
O
O
O
O
O
l
l
l
l
2
2
2
2
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
O
O
O
O
l
l
l
l
l
l
l
l
O
O
O
O
O
O
O
O
2
2
2
2
F-->-F'
lib
Calc.
frequency
(MHz)
Is
=
+l
Is
Is
Is
Is
Is
Is
Is
=
=
=
=
=
=
=
+1
+1
+1
O, :1::2
O, :1::2
O, :1::2
O, :1::2
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
14 =
14
14
-1
-1
-1
-1
+1
+l
+l
+l
-1
= -1
= -1
14 = -1
14
= +l
14 =
14 =
14 =
Is =
Is =
Is =
Is =
+l
+l
+l
O, :1::2
O, :1::2
O, :1::2
O, :1::2
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
27/2-29/2
21/2-23/2
25/2-27/2
23/2-25/2
23337.20
23337.66
23338.59
23339.06
23384.18
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
23/2-25/2
27/2-29/2
25/2-27/2
25121.13
25121.49
25122.34
25122.71
25132.40
25132.76
25133.61
25133.98
25123.68
25124.04
25124.89
25125.26
25128.80
25129.16
25130.01
25130.38
25183.14
25184.14
25184.61
25185.67
23386.02
23385.30}
23387.21
Obs.a
frequency
(MHz)
23337.34
23338.75
23384.35
23386.05
25121.31
25122.60
25132.60
25133.85
25123.73
25125.03
25129.02
25130.25
25183.30
25184.45
25184.70
----
a :1:0.20 MHz.
b Negative l denotes the lowest, and positive l the highest frequency.
TABLE 4
MICROWAVESPECTRUMOF 37CI-C",C-81Br
J -->-J'
12 -->-13
Vibrational
state
114
115
O
O
O
O
l
l
l
l
li b
F-->-F
Calc.
frequency
(MHz)
Is =
Is =
15 =
15 =
J. Mol. Structure, 6 (1970) 181-204
-1
-1
-1
-1
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
23111.74
23112.13
23112.93
23113.33
Obs."
frequency
(MHz)
23111.97
23113.16
MICROW A VE SPECTRA
187
OF HALOGENOACETYLENES
TABLE 4 (continued)
J-+J'
Vibrational
state
V4
V5
lib
F-+F'
Calc.
frequency
(MHz)
27/2-29/2
25/2-27/2
21/2-23/2
23/2-25/2
27/2-29/2
21/2-23/2
25/2-27/2
23/2-25/2
---
Obs."
frequency
(MHz)
<--
Is
= +1
O
O
O
O
O
O
O
1
1
1
1
2
2
2
2
Is
Is
Is
Is
Is
Is
Is
=
=
=
=
=
=
=
O
O
O
O
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
O
O
O
O
2
2
2
2
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
14 =
14 =
14 =
14 =
14 =
14 =
O
13 -+ 14
+1
+1
+1
O, ::J:2
O, ::J:2
O, ::J:2
O, ::J:2
-1
-1
-1
-1
+1
+1
+1
+1
- 1
-1
- 1
-1
+1
+1
14
= +1
14
=
=
=
=
=
Is
Is
Is
Is
+1
O, ::J:2
O, ::J:2
O, ::J:2
O, ::J:2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
27/2-29/2
23/2-25/2
25/2-27/2
29/2-31/2
23/2-25/2
27/2-29/2
25/2-27/2
23122.15
23122.54
23123.16
23123.74
23168.68
23122.38
23123.60
23168.98
23170.25
23171.26
23169.65}
23169.83
24889.57
24889.88
24890.60
24890.92
24900.78
24901.09
24901.81
24902.13
24891.97
24892.28
24893.00
24893.32
24897.03
24897.34
24898.06
24898.38
24951.03
24889.80
24890.81
24900.95
24901.93
24892.19
24893.15
24897.24
24898.15
24950.70
24952.28
24953.18
24951.89}
24952.38
" ::J:0.20 MHz.
b Negative l denotes the lowest, and positive l the highest freqegnncy.
The error limit of the frequency determination for ch1orobromoacety1ene
was rather large (0.20 MHz), due mai nI y to the low intensities of the lines, unresolved quadrupole effects, incomplete modulation and overlapping of neighbouring lines and Star k components.
For chloroiodoacetylene
the J = 14 -dS, 15 --+ 16, 16 --+ 17, and 17 --+ 18
transitions were examined for the 3sCI-species while, for 37CI-C=C-I, the 15 --+ 16,
16 --+ 17, and 17 --+ 18 transitions were measured. Lines belonging to the ground
and the symmetrical bending (vs) states2 were observed. The spectra are reported
in Tables 5 and 6.
For the 3sCI species of chlorodiacetylene
the transitions
J
= 4 --+ 5, 5 --+ 6,
6 --+ 7, 7 --+ 8, and 8 --+ 9 were observed. For the 37CI species the 5 --+ 6 and 8 --+ 9
J. Mol. Structure, 6 (1970) 181-204
188
A. BJØRSETH,
E. KLOSTER-JENSEN,
K.-M. MARSTOKK,
H. MØLLENDAL
T ABLE 5
MICROWAVESPECTRUMOF 35CI-C=C-I
J --+J'
Vibrational
state
Vs
14 --+ 15
O
O
O
O
O
O
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
15
O
O
O
O
O
O
l
l
l
1
l
l
1
1
l
l
1
1
2
2
15 = O
15 = O
15 = O
15 --+16
lib
= O
15 = O
15
= O
15 = O
15
15
= O
= O
15 =
15 =
15 =
15 =
15 =
15 =
-I
-1
-1
-1
-1
-1
15 =
15 =
+1
15 =
+1
+1
15 = + 1
15 = + 1
15 = +1
15 = O, :::!::2
15 = O, :::1::2
15
= O, :::!::2
15
=
15
= O, :::!::2
15
=
15
15
O, :::!::2
O, :::!::2
= O
= O
15 = O
15 = -1
15
= -1
15 =
15 =
15 =
15 =
15 =
-1
-1
-1
-1
+1
15 = + 1
15 = +1
15
= +1
15 = +1
15 = + 1
15
=
O, :::!::2
15
=
O, :::!::2
J. Mol. Structure, 6 (1970) 181-204
F --+F'
Calc.
frequency
(MHz)
Obs."
frequency
(MHz)
25/2-27/2
27/2-29/2
23/2-25/2
29/2-31/2
33/2-35/2
31/2-33/2
25/2-27/2
27/2-29/2
23/2-25/2
29/2-31/2
33/2-35/2
31/2-33/2
25/2-27/2
27/2-29/2
23/2-25/2
29/2-31/2
33/2-35/2
31/2-33/2
25/2-27/2
27/2-29/2
29/2-31/2
23/2-25/2
31/2-33/2
33/2-35/2
21738.66
21738.58
21740.51
21740.32)
21743.55
21744.56
21745.95
21786.54
21787.83
21788.90
21790.92
21792.83
21793.51
21795.14
21796.43
21797.50
21799.52
21801.43
21802.11
21740.37
27/2-29/2
29/2-31/2
25/2-27/2
31/2-33/2
35/2-37/2
33/2-35/2
27/2-29/2
29/2-31/2
25/2-27/2
31/2-33/2
35/2-37/2
33/2-35/2
27/2-29/2
29/2-31/2
25/2-27/2
31/2-33/2
35/2-37/2
33/2-35/2
27/2-29/2
29/2-31/2
23188.64
21843.34
21843.14)
21846.00
21847.03
21849.18
21850.62
23190.25
23190.11)
23192.95
23193.80
23195.03
23239.70
23240.87
23241.73
23243.60
23245.20
23245.85
23248.87
23250.04
23250.90
23252.77
23254.37
23255.02
23300.28
23300.00)
21743.62
21744.65
21746.00
21786.40
21787.80
21788.78
21790.82
21792.74
21793.42
21795.14
21796.47
21797.49
21799.54
21801.35
21802.08
21843.25
21845.95
21847.10
21849.25
21850.65
23188.65
23190.14
23192.95
23193.85
23195.05
23239.69
23240.86
23241.72
23243.65
23245.15
23245.88
23249.00
23250.16
23251.01
23252.78
23254.35
23255.06
23300.40
MICROW AVE SPECTRA
189
OF HALOGENOACETYLENES
TABLE 5 (continued)
J
-->- J'
Vibrational
state
F-->-F'
l;b
V5
16 -->-17
17 -> 18
2
2
2
2
Is
Is
Is
Is
=
=
=
=
O
O
O
O
O
O
l
l
l
l
l
l
l
l
l
l
l
l
2
2
2
2
2
2
Is
= O
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
=
=
=
=
=
=
O
O
O
O
O
-1
=
-1
O
O
O
O
O
O
l
l
I
l
I
l
l
l
l
l
I
Is = O
Is = O
Is = O
15 = O
= -1
= -1
= -1
=
=
=
=
=
=
=
=
=
=
15 =
15 =
15 =
15
-1
+1
+1
+1
+1
+1
+l
O, ::1:2
O, ::1:2
O, ::1:2
O, ::1:2
O, ::1:2
O, ::1:2
= O
Is =
15 =
15 =
Is =
Is =
15 =
15
15
O, ::1:2
O, ::1:2
O, ::1:2
O, ::1:2
O
-1
-1
-1
-1
-1
= -1
= +1
15 = +1
= +l
15
15
15
= +1
= +1
31/2-33/2
25/2-27/2
33/2-35/2
35/2-37/2
29/2-31/2
31/2-33/2
27/2-29/2
33/2-35/2
37/2-39/2
35/2-37/2
29/2-31/2
31/2-33/2
27/2-29/2
33/2-35/2
37/2-39/2
35/2-37/2
29/2-31/2
31/2-33/2
27/2-29/2
33/2-35/2
37/2-39/2
35/2-37/2
29/2-31/2
31/2-33/2
33/2-35/2
27/2-29/2
35/2-37/2
37/2-39/2
31/2-33/2
33/2-35/2
29/2-31/2
35/2-37/2
39/2-41/2
37/2-39/2
31/2-33/2
33/2-35/2
29/2-31/2
35/2-37/2
39/2-41/2
37/2-39/2
31/2-33/2
33/2-35/2
29/2-31/2
35/2-37/2
39/2-41/2
Calc.
frequency
(MHz)
Obs.a
frequency
(MHz)
23302.70
23303.31
23302.68)
23305.44
23306.52
23305.50
23306.55
24638.52
24638.5]
24639.93
24639.84)
24642.35
24643.08
24644.18
24692.74
24693.73
24694.52
24696.24
24697.59
24698.21
24702.49
24703.57
24704.27
24705.99
24707.34
24707.96
24642.37
24643.15
24644.22
24692.67
24693.74
24694.50
24696.25
24697.56
24698.15
24702.51
24703.59
24704.25
24706.00
24707.34
24707.94
24757.11
24756.77)
24759.62
24759.27)
24761.68
24762.49
24639.89
24757.05
24759.43
24761.75
24762.54
26088.31
26088.35
26089.51
26089.44)
26091.74
26092.37
26093.36
26145.71
26146.70
26147.28
26148.86
26150.01
26150.60
26156.03
26157.02
26157.60
26159.18
26160.34
26091.78
26092.45
26093.48
26145.66
26146.65
26147.22
26148.80
26149.89
26150.50
26156.04
26157.02
26157.61
26159.17
26160.27
26089.35
J. Mol. Structure, 6 (1970) 181-204
190
A. BJØRSETH,
E. KLOSTER-JENSEN,
K.-M. MARSTOKK,
H. MØLLENDAL
TABLE 5 (continued)
J
-;o. J'
Vibrational
state
Vs
l
2
2
2
2
2
2
Is
Is
Is
Is
Is
Is
Is
lib
F-->-F'
Cale.
frequency
(MHz)
Obs.a
frequency
(MHz)
=
=
=
=
=
=
=
37/2-39/2
31/2-33/2
33/2-35/2
35/2-37/2
29/2-31/2
37/2-39/2
39/2-41/2
26160.93
26160.87
26213.85
26213.49)
26213.75
+l
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
26215.96
26215.81)
26217.90
26218.53
26215.90
26217.93
26218.54
a ::1::0.10MHz.
b Negative l denotes the lowest, and positive l the highest frequency.
T ABLE 6
MICROWAVESPECTRUMOF 37CI-C"C-I
J -->-J'
Vibrational
state
Vs
15 -->-16
O
O
O
O
O
O
l
l
l
l
l
l
1
l
l
l
l
l
2
2
2
2
2
2
Is =
+l
+l
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
+1
+1
+ l
+l
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
O
O
O
Is = O
Is = O
Is = O
16 -->-17
lib
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
=
=
=
=
=
=
=
=
=
=
J. Mol. Structure, 6 (1970) 181-204
O
O
O
O
O
O
-1
-1
-I
-1
-1
-1
F-->-F'
Calc.
frequency
(MHz)
Obs."
frequency
(MHz)
27/2-29/2
29/2-31/2
25/2-27/2
31/2-33/2
35/2-37/2
33/2-35/2
27/2-29/2
29/2-31/2
25/2-27/2
31/2-33/2
35/2-37/2
33/2-35/2
27/2-29/2
29/2-31/2
25/2-27/2
31/2-33/2
35/2-37/2
33/2-35/2
27/2-29/2
29/2-31/2
31/2-33/2
25/2-27/2
33/2-35/2
35/2-37/2
22374.35
22374.38
29/2-31/2
31/2-33/2
27/2-29/2
22375.97
22375.83)
22378.67
22379.53
22380.75
22423.75
22424.93
22425.79
22427.64
22439.26
22429.91
22432.25
22433.43
22434.29
22436.15
22437.76
22438.41
22482.03
22481.75)
22485.06
22484.43)
22487.19
22488.27
22375.91
22378.69
22379.57
22388.77
22423.70
22424.85
22425.72
22427.53
22429.17
22429.81
22432.29
22433.48
22434.30
22436.12
22437.75
22438.36
22482.20
22484.95
22487.28
22488.36
23773.34
23773.36
23774.76
23774.66)
23774.74
MICROW A VE SPECTRA
OF HALOGENOACETYLENES
191
TABLE 6 (continued)
J-+J'
Vibrational
state
lib
F-+F'
Calc.
frequency
(MHz)
Obs."
frequency
(MHz)
23777.18
23777.91
23779.01
23825.81
23826.88
23827.57
23829.30
23830.66
23831.28
23834.85
23835.92
23836.63
23838.35
23839.71
23840.33
23777.22
23778.00
23779.11
23825.72
23826.78
23827.47
23829.20
23830.57
23831.20
23834.90
23835.95
23836.66
23838.34
23839.70
23840.29
23887.71
23887.38)
23889.88\
23890.231
23892.29
23893.11
23892.39
23893.12
25172.24
25172.29
'1'5
17 -+ 18
--
O
O
O
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
Is =
+1
Is
Is
Is
Is
Is
Is
Is
=
=
=
=
=
=
=
+1
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
33/2-35/2
37/2-39/2
35/2-37/2
29/2-31/2
31/2-33/2
27/2-39/2
33/2-35/2
37/2-29/2
35/2-37/2
29/2-31/2
31/2-33/2
27/2-29/2
33/2-35/2
37/2-39/2
35/2-37/2
29/2-31/2
31/2-33/2
33/2-35/2
27/2-29/2
35/2-37/2
37/2-39/2
O
O
O
O
O
O
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
O
O
O
O
O
O
-1
-1
-1
-1
-1
-1
+1
+1
+1
+1
+1
+1
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
O, ::1::2
31/2-33/2
33/2-35/2
29/2-31/2
35/2-37/2
39/2-41/2
37/2-39/2
31/2-33/2
33/2-35/2
29/2-31/2
35/2-37/2
39/2-41/2
37/2-39/2
31/2-33/2
33/2-35/2
29/2-31/2
35/2-37/2
39/2-41/2
37/2-39/2
31/2-33/2
33/2-35/2
35/2-37/2
29/2-31/2
37/2-39/2
39/2-41/2
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
Is
=
=
=
=
=
=
=
=
=
=
=
=
=
O
O
O
-1
-1
-1
-1
-1
-1
+ 1
+1
+1
+1
25173.50
25173.43)
25175.67
25176.31
25177.30
25227.79
25228.77
25229.35
25230.94
25232.10
25232.69
25237.36
25238.34
25238.92
25240.51
25241.67
25242.26
25293.30
25292.94)
25295.41
25285.27)
25297.39
25298.00
23887.75
23890.23
25173.53
25175.75
25176.41
25177.40
25227.74
25228.70
25229.28
25230.95
25232.04
25232.61
25237.42
25238.37
25238.90
25240.54
25241.68
25242.26
25293.00
25295.40
25297.40
25298.10
::1::0.10MHz.
b Negative l denotes the lowest, and positive l the highest frequency.
a
J. Mol. Structure, 6 (1970) 181-204
192
A. BJØRSETH, E. KLOSTER-JENSEN, K.-M. MARSTOKK,
H. MØLLENDAL
T ABLE 7
MICROWAVESPECTRUMOF H-C"C-C"C-35Cl
J->-J+l
Vibrational state
V7
Vs
Vg
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
l
l
l
l
l
l
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
l
l
O
O
O
O
O
O
O
O
l
l
l
l
O
O
O
O
l
l
l
l
l
l
l
O
O
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
2
2
2
2
l:
F ->-F'
Calc.
frequency
(MHz)
Obs.b
frequency
(MHz)
11/2-13/2
9/2-11/2
5/2- 7/2
7/2- 9/2
11/2-13/2
9/2-11/2
5/2- 7/2
11/2-13/2
9/2-11/2
5/2- 7/2
7/2- 9/2
11/2-13/2
9/2-11/2
5/2- 7/2
13755.31
13755.28
--4->-5
5->-6
19 = -1
19 = -1
19 = -1
19 = -1
19 =
19 =
19 =
+1
+1
+1
ls
ls
Is
Is
Is
=
=
=
=
=
-1
-1
-1
-1
+l
Is =
+l
Is =
+l
19 = -1
19 = -1
19 = - l
19 =
19 =
19 =
19 =
Is =
ls =
Is =
ls =
Is =
Is =
l7 =
l7 =
l7 =
17 =
17 =
- l
+l
+l
+l
-1
-1
-1
+l
+l
+l
-1
-1
-1
- l
+l
17 = + l
17 = + l
l7 = +1
19 = O, ::1::2
19 = O, :1:2
19 = O, ::1::2
19
=
J. Mol. Structure, 6 (1970) 181-204
O, ::1::2
13/2-15/2
11/2-13/2
7/2- 9/2
9/2-11/2
13/2-15/2
11/2-13/2
7/2- 9/2
13/2-15/2
11/2-13/2
7/2- 9/2
13/2-15/2
11/2-13/2
7/2- 9/2
13/2-15/2
11/2-13/2
9/2-11/2
7/2- 9/2
13/2-15/2
11/2-13/2
9/2-11/2
7/2- 9/2
13/2-15/2
7/2- 9/2
11/2-13/2
9/2-11/2
13/2-15/2
7/2- 9/2
11/2-13/2
9/2-11/2
13754.43
13754.32)
13753.45
13765.84
13764.96
13764.85)
13754.92
13754.04
13753.06
13753.93}
13759.79
13758.91
13758.80)
16505.99
16505.31
16505.42)
16504.74
16518.63
16517.95
16518.06)
16505.52
16504.84
16504.95)
16510.80
16510.69
16511.37}
16498.07
16497.41
16497.98
16498.66)
16502.31
16501.63
16502.20
[6502.")
16543.59
16543.61)
13754.42
13753.58
13765.80
13764.87
13754.42
13753.58
13759.71
13758.85
16506.03
16505.44
16504.87
16518.50
16517.97
16505.44
16504.87
16510.98
16498.00
16502.20
16543.90
16541.70
16541.34
16541.35)
16547.58
16547.46
16547.48)
16545.21
16545.22)
16545.37
MICROW AVE SPECTRA
193
OF HALOGENOACETYLENES
TAB LE 7 (continued)
--
J-+ J+1
6-+7
7-+8
Vibrational state
V7
Vs
Vo
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
O
O
O
O
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
O
O
O
O
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
2
2
2
2
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
O
O
O
O
F-+F'
Ila
lo = + 1
lo
= +1
lo = + 1
lo = + 1
lo
= -1
lo
lo
lo
Is
Is
Is
Is
= -1
= -1
=
=
=
=
=
-1
-1
-1
-1
-1
Is =
Is =
+1
+1
Is =
Is =
17 =
17 =
17 =
17 =
17 =
+ 1
+1
- 1
-1
-1
-1
17
+1
= +1
17 =
17 =
lo =
lo =
lo =
lo =
+1
+1
O, ::1:2
O, ::1:2
O, ::1:2
O, ::1:2
lo = + 1
lo =
lo =
lo =
lo =
lo =
lo =
lo =
Is =
Is =
Is =
Is =
Is =
18 =
Is =
Is =
+1
+1
+1
- 1
-1
-1
-1
-1
-1
-1
-1
+1
+1
+1
+ 1
15/2-17/2
13/2-15/2
11/2-13/2
9/2-11/2
15/2-17/2
13/2-15/2
11/2-13/2
9/2-11/2
15/2-17/2
13/2-15/2
11/2-13/2
9/2-11/2
15/2-17/2
9/2-11/2
13/2-15/2
11/2-13/2
15/2-17/2
13/2-15/2
9/2-11/2
11/2-13/2
15/2-17/2
13/2-15/2
9/2-11/2
11/2-13/2
15/2-17/2
9/2-11/2
13/2-15/2
11/2-13/2
17/2-19/2
15/2-17/2
13/2-15/2
11/2-13/2
17/2-19/2
15/2-17/2
13/2-15/2
11/2-13/2
17/2-19/2
15/2-17/2
11/2-13/2
13/2-15/2
17/2-19/2
15/2-17/2
13/2-15/2
11/2-13/2
17/2-19/2
15/2-17/2
13/2-15/2
11/2-13/2
Calc.
frequency
(MHz)
19271.15
19271.50)
19270.97
19270.62)
19256.41
19256.76)
19256.23
19256.20
19255.85
19255.32
In55"}
19255.67
Obs."
frequency
(MHz)
19271.37
19270.97
19256.43
19256.00
19262.84
19263.03)
19262.91
19262.15
19262.68)
19262.46
19247.85
19247.67
19248.20}
19247.32
19247.74
19252.77
19252.60
19253.12}
19252.24
19304.68
19304.86)
19303.27
19303.44)
21969.80
21969.80)
21969.32
21969.32)
22024.17
22023.74
22024.00
22024.41]
22007.33
22007.15
22007.57}
22006.94
22006.70
22006.29
22006.52
22n}
22014.49
22014.08
22014.32
22014.73]
19247.40
19252.74
19252.30
19304.70
19303.32
21969.88
21969.40
22024.14
22007.25
22006.75
22014.46
J. Mol. Structure, 6 (1970) 181-204
194
A. BJ0RSETH,
E. KLOSTER-JENSEN,
K.-M. MARSTOKK,
H. M0LLENDA
TABLE 7 (continued)
J-,>J+l
8-'>9
Vibrational state
V7
Vs
Vg
1
1
1
1
1
1
1
1
1
1
1
1
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
2
2
2
2
1
1
1
1
O
O
O
O
O
O
O
O
O
O
O
O
1
1
1
1
O
O
O
O
1
1
1
1
2
2
2
2
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
1
1
1
O
O
O
O
O
O
O
O
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
O
O
O
1
1
1
1
1
1
1
1
O
O
O
O
O
O
O
O
O
O
O
F -'> F'
lia
17 =
17 =
17 =
17 =
17 =
17 =
17 =
17 =
Is
Is
Is
Is
19
19
19
19
=
=
=
=
=
=
=
=
-1
-1
-1
-1
+1
+1
+1
+1
O, ::\::2
O, ::\::2
O, ::\::2
O, ::\::2
O, ::\::2
O, ::\::2
O, ::\::2
O, ::\::2
17/2-19/2
15/2-17/2
13/2-15/2
11/2-13/2
17/2-19/2
15/2-17/2
13/2-15/2
11/2-13/2
17/2-19/2
11/2-13/2
15/2-17/2
13/2-15/2
17/2-19/2
11/2-13/2
15/2-17/2
13/2-15/2
17/2-19/2
11/2-13/2
15/2-17/2
13/2-15/2
17/2-19/2
11/2-13/2
15/2-17/2
13/2-15/2
19/2-21/2)
17/2-19/2
19 = +1
= +1
19 = + 1
19 = + 1
19
19 =
19 =
19 =
19 =
-1
-1
-1
- 1
Is =
Is =
Is =
Is =
Is =
Is =
Is =
Is =
17 =
17 =
17 =
-1
- l
-1
-1
+ 1
+ 1
+1
+ 1
-1
-1
-1
J. Mol. Structure, 6 (1970) 181-204
13/2-15/2
15/2-17/2)
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
13/2-15/2
15/2-17/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
Calc.
frequency
(MHz)
21997.54
21997.13
21997.37
21997.78 J
22003.19
22002.77
22003.00
22003.42 J
22046.75
22046.97)
22045.82
22046.03)
22051.82
22052.04)
22050.89
22051.10)
22056.99
22057.21)
22056.06
22056.27)
22062.14
22062.36)
22061.21
22061.42)
Obs.b
frequency
(MHz)
21997.49
22003.15
22047.03
22046.16
22051.67
22050.83
22057.29
22056.40
22062.19
22061.38
24715.95
24716.02
24715.57
24715.60
24777.19
24776.87
24777.02
24777.36J
24758.23
24758.06
24758.40}
24757.69
24757.52
24757.19
24757.36
24moo}
24766.30
24765.96
24766.12 J
24766.46
24747.23
24746.90
24747.40}
24777.20
24758.19
24757.74
24766.19
24747.15
MICROW AVE SPECTRA
195
OF HALOGENOACETYLENES
TABLE 7 (continued)
J--->-J+1
a
Vibrational state
V7
Vs
Vg
l
l
l
l
l
l
I
l
l
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
2
2
2
2
O
O
O
O
l
l
l
l
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
O
O
O
O
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
3
3
Ila
17 =
17 =
17 =
17 =
17 =
Is =
Is =
Is =
Is =
Ig =
Ig =
Ig =
Ig =
Ig =
Ig =
Ig =
Ig =
-l
+l
+l
+l
+l
O, ::1:2
O, ::1:2
O, ::1:2
O, ::1:2
O,::1:2
O, ::1:2
O, ::1:2
O, ::1:2
- l
-1
-I
-I
Ig
Ig
= +1
Ig
= +1
= +1
= +1
Ig = ::1:3
Ig
Ig
=
::1:3
Ig = ::1:3
Ig
=
::1:3
F--->-F'
Calc.
frequency
(MHz)
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
13/2-15/2
17/2-19/2
15/2-17/2
19/2-21/2
13/2-15/2
17/2-19/2
15/2-17/2
19/2-21/2
13/2-15/2
17/2-19/2
15/2-17/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
13/2-15/2
17/2-19/2
15/2-17/2
24747.06
24753.61
ObS.b
frequency
(MHz)
24753.12
24753.45}
24753.28
24802.63 \
2480 I.76
24802.41
24801.97
24814.13
24813.48
24753.41
24802.30
;
24814.17
24813.56
24813.92
24813.27)
24813.69
24808.12
24808.33}
24808.10
24807.47
24807.68}
24807.50
24819.73
24819.94}
24819.08
24819.29}
24866.33
24866.33}
24864.64
24864.65}
24852.49
24852.16
24852.32
24852.66)
24890.40
24890.06
24890.")
24890.22
24872.13
24872.13}
24870.64
24870.65)
24819.72
24819.08
24866.46
24865.03
24852.18
24890.40
24872.25
24870.54
Negative I denotes the lowest, and positive I the highest frequency.
b ::1:0.15MHz.
transitions
were examined.
The 4 -+ 5 transition
ofthis
speeies falling
in the accessi-
ble spectral region, had insufficient intensity to be observed. The spectra are reported in Tables 7 and 8. Lines belonging to the antisymmetrical (V7)' symmetrical
(Vg) C=C-C=C bending modes4, and to the C=C-CI bending vibration4 (Vg) were
J. Mol. Structure, 6 (1970) 181-204
196
A. BJØRSETH,
E. KLOSTER-JENSEN,
K.-M. MARSTOKK,
H. MØLLENDAL
T ABLE 8
MICROWAVESPECTRUMOF H-C==C-C==C_37C]
J->-J+l
5->-6
8->-9
Vibrational state
V7
Va
Vg
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
l
l
l
l
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
l
l
l
l
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
l
l
l
l
F ->-F'
l,a
19 = + l
19 = + l
19 = + l
19 = + l
19 = - l
19 = -1
19
=
19 =
la =
la =
la =
la =
la =
la =
la =
la =
-1
- l
-1
-1
-1
-1
+l
+l
+l
+l
19 = +1
19
19
= +l
= +l
19 =
19 =
19 =
19 =
19 =
la =
la =
la =
la =
la =
la =
la =
la =
17 =
17 =
17 =
17 =
17
17
+l
-1
-1
-1
-1
-1
-1
-1
-1
+l
+l
+l
+l
-1
-1
-1
-1
= +1
= +l
17 = + l
17 = +1
--J. Mol. Structure, 6 (1970) 181-204
13/2-15/2
11/2-13/2
9/2-11/2
7/2- 9/2
13/2-15/2
11/2-13/2
9/2-11/2
7/2- 9/2
13/2-15/2
11/2-13/2
9/2-11/2
7/2- 9/2
13/2-15/2
11/2-13/2
9/2-11/2
7/2- 9/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
Calc.
frequency
(MHz)
Obs.b
frequency
(MHz)
16143.96
]6144.41)
16144.15
16143.87
16143.42)
]6132.23
16131.78
16131.24
16131.69
16131.87
16131.42
16130.88
16131.33
16137.03
16136.49
16136.94
16137.48]
24215.66
24215.39
24215.52
24215.79]
24197.39
24197.12
24197.25
24196.97
24107'52}
24196.83
16]43.65
16131.73
16137.19
24215.58
24197.27
24196.70
24196.57)
24205.25
24204.99
24205.12
24205.39]
24186.77
24186.50
24186.9<>]
24186.63
24192.64
24192.37
24192.50
24192.,,]
24240.02
24239.85
24240.37
2424<>.54]
24205.15
24186.31
24192.60
24240.40
MICROW AVE SPECTRA
197
OF HALOGENOACETYLENES
T ABLE 8 (continued)
J-;.J+l
Vibrational state
V7
V8
Vo
O
2
2
2
2
1
1
1
1
O
O
O
O
1
1
1
1
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
1
1
1
1
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
3
3
o
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
a
F -;. F'
It
18 =
18 =
18 =
18 =
lo
lo
lo
lo
lo
lo
lo
lo
lo
=
=
=
=
O, :1:2
O, :1:2
O, :1:2
O, :1:2
O, :1:2
O, :1:2
O, :1:2
='=- 1
= - 1
= - 1
= -1
= +1
lo =
lo =
lo
lo
lo
lo
lo
O, :1:2
=
=
=
=
=
+1
+1
+1
:1:3
:1:3
:1:3
:1:3
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
13/2-15/2
17/2-19/2
15/2-17/2
19/2-21/2
13/2-15/2
17/2-19/2
15/2-17/2
19/2-21/2
13/2-15/2
17/2-19/2
15/2-17/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
17/2-19/2
15/2-17/2
13/2-15/2
19/2-21/2
13/2-15/2
17/2-19/2
15/2-17/2
Obs.b
Calc.
frequency
(MHz)
frequency
(MHz)
24245.89
24245.72
24246.24
24246.41 J
24251.72
24251.89)
24251.20
24251.3 7)
24257.19
24257.36)
24256.67
24256.84)
24302.70
24302.70)
24301.52
24301.52)
24289.36
24289.10
24289.50
24289.23 J
24325.91
24326.041
24325.77
24325.64
24245.90
24251.93
24251.48
24257.29
24256.72
24302.90
24301.80
24289.40
24325.92
j
24308.18
24308.18)
24308.28
24307.00
24307.00)
24307.02
Negative l denotes the lowest, and positive l the highest frequency.
b :1:0.15 MHz.
observed. The uncertainty of the frequency determination is as large as 0.15 MHz
for similar reasons as for chlorobromoacetylene.
Spectra of 13C-species in natural abundances for all three molecules were
searched for, but were not observed.
METHOD OF CALCULATION
For a linear molecule the frequency v of a transition from J, F to J', F' is
given by7
v = [2Bv:J::~(V+~)J(J+l)-4D(J+l)[(J+I)2-12]+Eq
(l)
J. Mol. Structure, 6 (1970) 181~204
198
A. BJØRSETH,
E. KLOSTER-JENSEN,
K.-M. MARSTOKK,
H. MØLLENI
where
B = B -La.
vei
Bv is the rotational
( ) = Bo-La.v.
V'+~
I
I
2
constant,
i
l I
q is the l-type doubling constant,
distortion constant, Eq represents the quadrupole
vibration interaction constant.
D is the centrifl
fine structure, and aj the rotati
Chlorobromoacetylene
The quadrupole coupling constants for the two bromine nuclei were de
mined from the 11 -+ 12 transitions of 81Br-C=C-35Cl and 79Br-C=C-35C1. ~
splitting due to the chlorine nuclei was ca1culated to give a negligible contribut
to the observed quadrupole fine structure. This effect was therefore omitted in
ca1culations. Only two quadrupole components were observed for each transiti,
while four lines are predicted for the F -+ F + 1 transitions which were observ
These four components form two pairs of closely spaced lines which were ]
resolved. It was assumed in the ca1culations that the observed frequencies cO!
spond to the centre frequencies ca1culated for the two unresolved components. 1
quadrupole coupling constants obtained in this way are 685:!::50 MHz for 79
and 581:!:50 MHz for 81Br.
In the least squares fitting of the lines to eqn. (l) the quadrupole coupll
constants were kept constant. However, it was found that the centrifugal distorti
constant D could not be determined. Reasonable values of D were then gues~
and kept constant in the least squares adjustment. A value of D = 0.08 kHz yiek
the lowest error square sum. The ca1culated frequencies under these assumptions ;
found in Tables 1-4 and the result of the least squares fitting in Table 9.
TABLE 9
MOLECULAR
PARAMETERS FOR CHLOROBROMOACETYLENE
Parameter
35CI-C=C-79Br
3SCI-C=C_81 Br
37CI-C=C-79
Bo (MHz)
0(4 (MHz)
O(s (MHz)
q4 (MHz)
qs (MHz)
lo (amu A2)b
D (kHz)&
eqQ (MHz)
925.181
::1::0.006
916.824
::1::0.004
895.418
::1::0.010
-2.071
::1::0.004
-2.062
::1::0.003
-2.012
::1::0.010
-2.096
::1::0.002
-2.086
::1::0.001
-2.031
::1::0.002
0.1932::1::0.0028
0.4218::1::0.0002
546.413
::1::0.004
0.08
685
0.1925
0.4200::1::0.0001
551.394
::1::0.003
0.08
581
Uncertainties are standard deviations.
aAssumed.
b Conversion facto r 505531 MHz amu A2.
J. Mol. Structure, 6 (1970) 181-204
::1::0.0018
Br
0.1829::1::0.0028
0.4025
564.575
::1::0.0001
::1::0.006
0.08
685
37CI-C=C-811
887.165 ::I::O.O
-1.985
::1::0.0<
-2.009
::I::O.O
0.1806::1::0.0(
0.4001 ::I::O.O
569.827 ::I::O.O
0.08
581
MICROW
AVE SPECTRA
199
OF HALOGENOACETYLENES
Chloroiodoacetylene
The quadrupole coupling constant for the iodine nuc1eus was obtained from
the fine structure of the 14 -+ 15 transition. Lines belanging both to the ground and
vibrational excited sta!es were used and it was assumed that the quadrupole coupling constant is independent of the observed vibrational states. A value of
-2280:t40 MHz was obtained. Both first and second order quadrupole theory7
was used in the ca1culations. As for chlorobromoacetylene, the contribution to the
quadrupole fine structure from the chlorine nuc1ei was ca1culated to be negligible.
In the least squares treatment, eqQ was kept constant. Again, the centrifugal
distortion constant could not be found significantJy different from zero. In the least
squares fitting, plausible values of D were preset to a constant value. D = 0.03
kHz yielded the lowest error square sum for both chlorine species. The observed
and ca1culated spectra are found in Tables 5 and 6, and the molecular parameters
in Table 10.
TABLEIO
MOLECULAR PARAMETERS FOR CHLOROIODOACETYLENE
Parameter
3sCI-C=.C-I
37Cl-C=C-I
Bo
CXs
qs
lo
eqQ
D
724.7721 :!::0.0013
-1.7376:!::0.0007
0.2876:!::0.0009
697.503 :!::0.001
- 2280
0.03
699.326 :!::0.002
-1.676
:!::0.001
0.2657 :!::0.OOI4
722.883 :!::0.OO2
- 2280
0.03
(MHz)
(MHz)
(MHz)
(amu A2)b
(MHz)
(kHz)"
.------
" Assumed.
b Conversion
facto r 505531 MHz amu A2.
Chlorodiacetylene
Due to the small quadrupole splitting and large uncertainty of the frequency
determination, the evaluation of the quadrupole coupling constants was difficult.
For 35Cl-chlorodiacetylene the most reliable estimate was obtained from the 7 -+ 8
transition of the ground vibrational state. A value of eqQ = - 79:t 10 MHz was
obtained.
For the 37Cl species, no lines were measured in the ground state and a reIiable determination of eqQ was not possible.
In the least squares fitting of the lines of H-C=.C-C=.C-35Cl to eqn. (l), eqQ
was constrained to -79 MHz. However, the centrifugal distortion constant D was
indeterminable by the ordinary least squares procedure. Reasonable values of D
were then preset to a constant value in the least squares treatment. A value of
D = 0.03 kHz yielded the lowest error square sum.
T
~Æn'
<:f.,,~fHM
(; (10'7C1\
l Ql
~"A
200
A. BJØRSETH,
E. KLOSTER-JENSEN,
K.-M. MARSTOKK,
H. MØLLENI
In the least squares fitting of the lines of the 37Cl species, the quadruI
coupling constant was assumed to be - 63.1 MHz. This was found to be the va
for chloroacetylene12, and was kept constant at this value in the least squares 1
cedure. Again it was found that the centrifugal distortion constant was inde
minable. Reasonable values of D were preset to a constant value, and it was ,
found for this species that D = 0.03 kHz yielded the lowest error square sum.
The calculated frequencies under these assumptions are found in Tabl,
and 8, and the result of the least squares analysis is given in Table Il.
TABLE 11
MOLECULAR
PARAMETERS OF CHLORODIACETYLENE
Parameter
H-C==C-C==C_35
Bo
10
fX7
fX8
fX9
q7
q8
q9
eqQ
D
1373.10
368.168
-1.919
-2.559
-2.881
0.352
0.487
1.053
(MHz)
(amu A2)a
(MHz)
(MHz)
(MHz)
(MHz)
(MHz)
(MHz)
(MHz)
(kHz)b
Cl
::1::0.01
::1::0.003
::1::0.006
::1::0.003
::1::0.002
::1::0.001
::1::0.003
::1::0.001
-79
0.03
H-C==C-C==C_37
1342.04
376.69
-1.87
-2.50
- 2.809
0.326
0.468
1.015
-63.1b
0.03
Cl
::1::0.04
::1::0.01
::1::0.02
::1::0.01
::1::0.008
::1::0.005
::1::0.010
::1::0.002
Uncertainties are standard deviations.
a Conversion facto r 505531 MHz amu A2.
bAssumed.
STRUCTURE
Chlorobromoacetylene
A complete rs structure cannot be given since 13C-species were not obsen
However, the rsparameters9 of the chlorine and bromine nuc1ei have been calcu
ed. From these the overalllength (rs) of the molecule was calculated to range fl
4.625 Å to 4.626 Å depending on which parent molecule was chosen.
Two methods were used for calculating the structure of the molecule. .
first is the familiar ro-method, whereby the structural parameters are fitted to
observed moments of inertia. In the other method, a bond shrinkagelO on s
stitution by heavier atoms was assumed. A shrinkage of l x 10-4 Å and 5 x 10-
for the chlorine-carbon, and 5 x 10- 5 Å and l x 10-
5
Å for the bromine-car
distance were used. Under these assumptions, the structural parameters were fi
to the moments of inertia. The results are given in Table 12. The error limits ref
only the uncertainty of the fitting procedure.
T
~Ænl<:f.urf".o
F. (1 Q7())
1 Rl_7()J.
MICROW AVE SPECTRA
OF HALOGENOACETYLENES
201
TAB LE 12
RESULT OF STRUCTURE CALCULATIONSFOR CHLOROBROMOACETYLENE
Method
r( C-CI)
(A)
r( c,,,c)
(A)
r(C-Br)
(A)
r(CI' . Br)
(A)
1.624:1:0.001
1.212:1:0.005
1.789 :1:0.005
4.625
1.630:1:0.001
1.208:1:0.001
1.788 :1:0.004
4.626
1.631 :1:0.001
1.206:1:0.001
1.790:1:0.005
4.627
1.628 :1:0.005
1.209 :1:0.008
1.790:1:0.005
4.627
---ro-structure
ro-structure
with shrinkage
r(C-Cl)
r(C-Br)
= 1 X 10-4 A
= 5 X 10-5 A
ro-structure
with shrinkage
r(C-CI)
r(C-Br)
Final
= 5 X 10-5 A
= 1 X 10-5 A
structure
It is seen from Table 12 that the C-CI and C=C distances are somewhat influenced by the assumed shrinkage, while the C-Br distance is almost unaffected.
The C=C distance is also obtained with a higher degree of precision when shrinkage
effects are introduced. The length of the molecule ca1culated by the different methods agrees well with the length ca1culated from the rs coordinates. The so-called
"final" structure of Table 12, represents the mean of various ca1culated structures.
Chloroiodoacetylene
Only two moments of inertia were obtained for this molecule. Assuming
the C=C distance to be in the 1.206-1.212 Å range, the C-CI and C-I distances may
be calculated by fitting these distances to the observed moments of inertia. The
result of such a procedure is given in Table 13. It was found that the halogen-carbon distances are not very sensitive to the assumed C=C distance.
TABLEI3
STRUCTURE
CALCULATIONS
FOR CHLOROIODOACETYLENE
-r( c=c)a
(A)
r( C-CI)
(A)
r (C-I)
(A)
1.206
1.209
1.212
l. 628
1.627
1.626
1.991
1.989
1.987
aAssumed.
J. Mol. Structure. 6 (1970) 181-204
202
A. BJØRSETH,
E. KLOSTER-JENSEN,
K.-M. MARSTOKK,
H. MØLLENI
Chlorodiacetylene
Chlorodiacetylene has five structural parameters, two of which may be
culated if the other three are assumed. It has been shown8 that the length of
C=C triple bond depends little on the nature of the substituents. Assuming the
C=C bonds to be equal at 1.207 Å 1,9b,11-13,and the C-H bond to be 1.
Å!, 9b,11- 13, one finds the C-Cl bond to be 1.625 Å and the C-C single bond te
1.378 Å. These two distances are, of course, subject to rather large uncertaint
but compare reasonably well with distances reported for similar molecules 1,9b,11-
DISCUSSION
Structure
The structure of chlorobromoacetylene is very similar to those of ot
monohalogeno- and dihalogeno-acetylenes 1. The C=C triple bond distance
been found to lie between 1.204 and 1.209 Å for many molecules, e.g., chIc
acetylene13, propynal14, dimethyldiacetylene15, methylacetylene9b and cya
acetylene9b. The C-Cl distance is a little shorter than the 1.637 Å reported
chloroacetylene13 and methy1chloroacetylene11. However, the difference is
small that it is hardly significant. The C-Br distance is c10seto the value of 1.79
found for methylbromoacetylene16and 1.790Å found for bromine cyanide 17
Since the structure of chloroiodoacetylene given in Table 12 was based U
the assumption of a known C=C distance, a detailed discussion is not justif
However, the C-Cl and C-I distances agree fairly well with reported values
similar molecules, e.g., the C-I distance of methyliodoacetylene16 is repor
to be 1.991 Å, and it is 1.988 Å for iodoacetylene18.
Dipole moment
With our present apparatus, the dipole moments of the three molecules co
not be determined by the conventional method but, by studying the modulatior
the ground and excited state lines, a rough estimate of the order ofmagnitude of
dipole moment was obtained. For chlorobromoacetylene a value of 0.15:i: O.H
was found. The dipole moment of chloroiodoacetylene is somewhat larger. A v
approximate value of 0.30:i: 0.15 D is estimated.
In a similar way the dipole moment of chlorodiacetylene was estimated
be 0.20::t0.lO D. This value is significantly lower than the 0.44 D reported
cWoroacetylene.
Quadrupole coupling constants
The quadrupole coupling constants of the bromine and iodine nuc1ei agl
within the experimentallimits, with literature values for similar compounds. I
79Br, 647 MHz is reported for methylbromoacetylene16 and 686.5:i:0.5 M
J. Mol. Structure. 6 (1970) 1Rl-?04
MICROW
A VE SPECTRA
203
OF HALOGENOACETYLENES
for bromine cyanide17. For the SlBr species the values 539 MHz16 and 573.5:t 0.5
MHz17 have been given for the same two molecules. For the iodine nudeus,
- 2420:t l MHz is reported for iodine cyanide1 7 and - 2230 MHz for methyliodoacetylene16.
The great similarity of the quadrupole coupling constants between the two
dihaloacetylenes reported here and corresponding monohaloacetylenes indicates
a similar electron distribution around the halogen nudei.
l-type doubling constants of chlorodiacetylene
The l-type doubling constant qs is given by 7
qs
=
B2
a~
we
(2)
where
a = 2 l +4:E(;i
(
i
w/
Wj2-WS2
)
(si is the Coriolis coupling constant, and w the vibrational frequency.
The Coriolis coupling constants were kindly computed for us by Dr. Cyvin
from the force field used in ref. 4. Byemploying these in formula (2), we obtain
q7 = 0.3513, qs = 0.4269, q9 = 0.9880 for 35-chlorodiacetylene
and q7 = 0.3356,
qs = 0.4079 and q9 = 0.9439 for 37-chlorodiacetylene. The agreement between the
calculated and observed l-type doubling constants (Table Il) is seen to be fairly
good.
ACKNOWLEDGEMENT
We are grateful to Dr. S. J. Cyvin for supplying us with the Coriolis coupling
constants for chlorodiacetylene. Dr. N. L. Owen is thanked for reading the manuscript, and Dr. T. G. Strand for giving us his generalleast squares program. Financial support from the Norwegian Council for Science and Humanities is gratefully
acknowledged.
REFERENCES
l
2
3
4
K. M. SMIRNOV, A. P. TOMILOV AND A. L SHCHEKOTIKHIN, Russ. Chem. Rev. (English Trans/.),
36 (1967) 326 and references cited therein.
D. CHRISTENSEN, P. KLABOE, E. KLOSTER-JENSEN AND L JOHNSEN, Spectrochim.
Acta, in press.
E. KLOSTER-JENSEN, Tetrahedron, 22 (1966) 965.
P. KLABOE, E. KLOSTER-JENSEN AND S. J. CYVIN, Spectrochim.
Acta, 23A (1967) 2733; D. H.
CHRISTENSEN, L JOHNSEN, P. KLABOE AND E. KLOSTER-JENSEN, Spectrochim. Acta, 25A (1969)
1569.
5
6
L HIRGATTAI AND R. ST0LEVIK, Acta Chem. Scand., in press.
E. KLOSTER-JENSEN, J. Am. Chem. Soc., 91 (1969) 5673.
J. Mol. Structure, 6 (1970) 181-204
204
7
8
9a
9b
10
11
12
13
14
15
16
17
18
A. BJØRSETH,
E. KLOSTER-JENSEN,
C. H. TOWNES AND A. L. SCHAWLOW, Micrawave
1955.
K.-M. MARSTOKK,
Spectrascapy,
H. MØLLEN!
McGraw-HilI,
New \
G. HERZBERG AND B. P. STOICHEFF, Nature, 175 (1955) 79.
J. KRAITCHMAN, Am. J. Phys., 21 (1953) 17.
C. C. COSTAIN, J. Chem. Phys., 29 (1958) 864.
V. W. LAURIE AND D. R. HERSCHBACH, J. Chem. Phys., 37 (1962) 1687.
C. C. COSTAIN, J. Chem. Phys., 23 (1955) 2037.
A. A. WESTENBERG, J. H. GOLDSTEIN AND E. B. WILSON, JR., J. Chem. Phys., 17 (1949) ]
J. K. TYLER AND J. SHERIDAN, Trans. Faraday Sac., 59 (1963) 2661.
C. C. COSTAIN AND J. R. MORTON, J. Chem. Phys., 31 (1959) 389.
A. ALMENNINGEN, O. BASTIANSENAND T. MUNTHE-KAAS, Acta Chem. Scand., 10 (1956)
J. SHERIDAN AND W. GORDY, J. Chem. Phys., 20 (1952) 735.
C. H. TOWNES, A. N. HOLDEN AND F. R. MERRITT, Phys. Rev., 74 (1948) 1113.
W. J. JONES, B. P. STOICHEFF AND J. K. TYLER, Can. J. Phys., 41 (1963) 2098.
J. Mol. Structure, 6 (1970) 181-204