Fred L. Voelz, Forrest F. Cleveland, Arnold G. Meister, and Richard B. Bernstein, "Substituted Methanes. XVII.* Vibrational Spectra, Potential Constants, and Calculated Thermodynamic Properties of Diiodomethane," J. Opt. Soc. Am. 43, 1061-1064 (1953)
Raman displacements, semiquantitative relative intensities, quantitative depolarization factors, and wave numbers for the infrared bands in the region 400–3800 cm−1 have been obtained for liquid CH2I2. A normal coordinate treatment was carried out, and a reasonable set of potential constants was determined, using the most general quadratic potential energy function. Assignments were made for all observed Raman and infrared bands. The heat content, free energy, entropy, and heat capacity at constant pressure were calculated for 12 temperatures from 100° to 1000°K.
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DK=Dadieu and Kohlrausch, reference 1; KY=Kohlrausch and Ypsilanti, reference 2; BW=Bacher and Wagner, reference 3; W=Wagner, reference 4; PR=Present results; PV=Probable values; Δν=Raman displacement in cm−1; I=relative intensity (b=broad, w=weak, v=very); ρ=depolarization factor; PS=deduced polarization state (P=polarized D=depolarized); and values in regard to which there is some uncertainty are enclosed by parentheses.
The uncertain 1197 observed only by W is probably 2968 cm−1 excited by Hg 4047A.
ν=wave number in cm−1 (at point of maximum absorption); I=intensity (w=weak, m=medium, s=strong, v=very).
Infrared not investigated below 525 cm−1.
Infrared not investigated above 400 cm−1.
Infrared not investigated below 275 cm−1.
Infrared not investigated below 400 cm−1.
Center of a broad band.
This band is resolved into two bands (1105 and 1110 cm−1) in the vapor state.
Uncertain values are enclosed in parentheses.
The present intensity symbols were determined by percent transmission as follows: vw, 95–100; w, 90–95; m, 60–90; s, 20–60; vs, 5–20; vvs, 0–5.
Table III
Probable values of the Raman and infrared spectral data, calculated wave numbers, and assignments for liquid CH2I2.a
Raman
Infrared
Δν
I
PS
ν
I
νc
Assignment
Type
121
61
P
…
…
127
ν4
a1
…
…
…
(208)
…
205
(ν4+ν9−ν3)
B2
236
1
P
238
…
242
2ν4
A1
…
…
…
(274)
…
299
(2ν7−2ν9)
A1
365
8
P
(350)
…
365
ν3−ν4
A1
…
…
…
(377)
…
386
ν2−2ν3
A1
…
…
…
444
w
449
ν9−ν4
B2
486
100
P
486
m
487
ν3
a1
567
37
D
573
s
567
ν9
b2
(598)
w
…
…
…
595
ν7−ν4
B1
…
…
…
639
w
635
ν2−ν7
B1
714
5
D
717
s
716
ν7
b1
781
w
…
780
m
781
ν2−ν9
B2
…
…
…
832
w
837
ν4+ν7
B1
965
5
D
…
…
972
2ν3
A1
1028
4
D
…
…
1028
ν5
a2
…
…
…
1034
s
1056
ν3+ν9
B2
1104
14
D
1106
vvs
1105
ν8
b2
1131
17
P
…
…
1140
2ν9
A1
…
…
…
1182
vw
1202
ν3+ν7
B1
…
…
…
1226
s
1226
ν4+ν8
B2
1230
ν2−ν4
A1
1350
24
P
1351
s
1348
ν2
a1
1429
5
P
1432
m
1432
2ν7
A1
(1571)
vw
…
1596
vw
1591
ν3+ν8
B2
1598
ν5+ν9
B1
1670
2
…
1667
vw
1675
ν8+ν9
A1
(1754)
vw
…
1749
w
1744
ν5+ν7
B2
…
…
…
1839
m
1837
ν2+ν3
A1
(1885)
vw
1921
w
1921
ν2+ν9
B2
…
…
…
2058
s
2056
2v5
A1
2067
ν2+ν7
B1
…
…
…
2132
m
2133
ν5+ν8
B1
…
…
…
2206
m
2210
2ν8
A1
…
…
…
2390
w
2398
ν1−ν9
B2
…
…
…
2456
m
2456
ν2+ν8
B2
…
…
…
2551
w
2563
ν6−ν3
B1
…
…
…
2850
m
2847
ν1−ν4
A1
2968
59
P
2967
s
2968
ν1
a1
3049
17
D
3049
vs
3050
ν6
b1
…
…
…
3450
m
3454
ν1+ν3
A1
…
…
…
(3510)
m
3535
ν3+ν6
B1
…
…
…
(3670)
m
3684
ν1+ν7
B1
…
…
…
3759
m
3765
ν6+ν7
A1
…
…
…
4065
m
4073
ν1+ν8
B2
4077
ν5+ν6
B2
…
…
…
4397
m
4400
ν2+ν6
B1
νc=calculated wave number in cm−1 and all other symbols have the same meaning as in Tables I and II.
Table IV
Molecular quantities for CH2I2.
Quantity
Value
C–H=h
1.093 A
C–I=i
2.12 A
All angles
109°28′
mI
126.92 awu
mH
1.008 awu
mC
12.010 awu
M
267.87 awu
σ
2
Ixx
380.4 awu A2
Iyy
1139 awu A2
Izz
762.1 awu A2
IAIBIC
3.302 × 108 (awu A2)3
Table V
Comparison of the observed and calculated wave numbers for liquid CH2I2.
Designation
Type
Observed
Calculated
ν1
a1
2968
2968
ν2
a1
1351
1348
ν3
a1
486
487
ν4
a1
121
127
ν5
a2
1028
1028
ν6
b1
3049
3050
ν7
b1
716
716
ν8
b2
1105
1105
ν9
b2
570
567
Table VI
Potential constants for CH2I2 compared with those of CH2CIBr and CH3I.a
Bond constants and bond-bond interaction constants are in md/A; bond-angle interactions are in md/rad; and angle constants and angle-angle interaction constants are in md A/rad2.
This number of significant figures is not really justified but is necessary to give the best reproduction of the observed frequencies and to secure internal consistency in the calculations.
For CH3I, these constants occur only as the combination fihh−fihi=−0.12144. For CH2I2, the value of this combination is −0.16771.
Table VII
Heat content, free energy, entropy, and heat capacity of CH2I2 for the ideal gaseous state at 1-atmos pressure.a
T
(H0−E00)/T
−(F0−E00)/T
S0
Cp0
100
8.70
56.10
64.80
9.63
200
9.63
62.41
72.03
11.62
273.16
10.38
65.52
75.90
13.27
298.16
10.65
66.20
76.84
13.81
300
10.66
66.51
77.17
13.85
400
11.71
69.72
81.43
15.75
500
12.67
72.45
85.12
17.22
600
13.53
74.82
88.35
18.37
700
14.29
76.97
91.26
19.30
800
14.96
78.92
93.89
20.07
900
15.57
80.72
96.29
20.72
1000
16.11
82.39
98.50
21.29
T is in degrees Kelvin and all other quantities are in units of cal deg−1 mole−1.
DK=Dadieu and Kohlrausch, reference 1; KY=Kohlrausch and Ypsilanti, reference 2; BW=Bacher and Wagner, reference 3; W=Wagner, reference 4; PR=Present results; PV=Probable values; Δν=Raman displacement in cm−1; I=relative intensity (b=broad, w=weak, v=very); ρ=depolarization factor; PS=deduced polarization state (P=polarized D=depolarized); and values in regard to which there is some uncertainty are enclosed by parentheses.
The uncertain 1197 observed only by W is probably 2968 cm−1 excited by Hg 4047A.
ν=wave number in cm−1 (at point of maximum absorption); I=intensity (w=weak, m=medium, s=strong, v=very).
Infrared not investigated below 525 cm−1.
Infrared not investigated above 400 cm−1.
Infrared not investigated below 275 cm−1.
Infrared not investigated below 400 cm−1.
Center of a broad band.
This band is resolved into two bands (1105 and 1110 cm−1) in the vapor state.
Uncertain values are enclosed in parentheses.
The present intensity symbols were determined by percent transmission as follows: vw, 95–100; w, 90–95; m, 60–90; s, 20–60; vs, 5–20; vvs, 0–5.
Table III
Probable values of the Raman and infrared spectral data, calculated wave numbers, and assignments for liquid CH2I2.a
Raman
Infrared
Δν
I
PS
ν
I
νc
Assignment
Type
121
61
P
…
…
127
ν4
a1
…
…
…
(208)
…
205
(ν4+ν9−ν3)
B2
236
1
P
238
…
242
2ν4
A1
…
…
…
(274)
…
299
(2ν7−2ν9)
A1
365
8
P
(350)
…
365
ν3−ν4
A1
…
…
…
(377)
…
386
ν2−2ν3
A1
…
…
…
444
w
449
ν9−ν4
B2
486
100
P
486
m
487
ν3
a1
567
37
D
573
s
567
ν9
b2
(598)
w
…
…
…
595
ν7−ν4
B1
…
…
…
639
w
635
ν2−ν7
B1
714
5
D
717
s
716
ν7
b1
781
w
…
780
m
781
ν2−ν9
B2
…
…
…
832
w
837
ν4+ν7
B1
965
5
D
…
…
972
2ν3
A1
1028
4
D
…
…
1028
ν5
a2
…
…
…
1034
s
1056
ν3+ν9
B2
1104
14
D
1106
vvs
1105
ν8
b2
1131
17
P
…
…
1140
2ν9
A1
…
…
…
1182
vw
1202
ν3+ν7
B1
…
…
…
1226
s
1226
ν4+ν8
B2
1230
ν2−ν4
A1
1350
24
P
1351
s
1348
ν2
a1
1429
5
P
1432
m
1432
2ν7
A1
(1571)
vw
…
1596
vw
1591
ν3+ν8
B2
1598
ν5+ν9
B1
1670
2
…
1667
vw
1675
ν8+ν9
A1
(1754)
vw
…
1749
w
1744
ν5+ν7
B2
…
…
…
1839
m
1837
ν2+ν3
A1
(1885)
vw
1921
w
1921
ν2+ν9
B2
…
…
…
2058
s
2056
2v5
A1
2067
ν2+ν7
B1
…
…
…
2132
m
2133
ν5+ν8
B1
…
…
…
2206
m
2210
2ν8
A1
…
…
…
2390
w
2398
ν1−ν9
B2
…
…
…
2456
m
2456
ν2+ν8
B2
…
…
…
2551
w
2563
ν6−ν3
B1
…
…
…
2850
m
2847
ν1−ν4
A1
2968
59
P
2967
s
2968
ν1
a1
3049
17
D
3049
vs
3050
ν6
b1
…
…
…
3450
m
3454
ν1+ν3
A1
…
…
…
(3510)
m
3535
ν3+ν6
B1
…
…
…
(3670)
m
3684
ν1+ν7
B1
…
…
…
3759
m
3765
ν6+ν7
A1
…
…
…
4065
m
4073
ν1+ν8
B2
4077
ν5+ν6
B2
…
…
…
4397
m
4400
ν2+ν6
B1
νc=calculated wave number in cm−1 and all other symbols have the same meaning as in Tables I and II.
Table IV
Molecular quantities for CH2I2.
Quantity
Value
C–H=h
1.093 A
C–I=i
2.12 A
All angles
109°28′
mI
126.92 awu
mH
1.008 awu
mC
12.010 awu
M
267.87 awu
σ
2
Ixx
380.4 awu A2
Iyy
1139 awu A2
Izz
762.1 awu A2
IAIBIC
3.302 × 108 (awu A2)3
Table V
Comparison of the observed and calculated wave numbers for liquid CH2I2.
Designation
Type
Observed
Calculated
ν1
a1
2968
2968
ν2
a1
1351
1348
ν3
a1
486
487
ν4
a1
121
127
ν5
a2
1028
1028
ν6
b1
3049
3050
ν7
b1
716
716
ν8
b2
1105
1105
ν9
b2
570
567
Table VI
Potential constants for CH2I2 compared with those of CH2CIBr and CH3I.a
Bond constants and bond-bond interaction constants are in md/A; bond-angle interactions are in md/rad; and angle constants and angle-angle interaction constants are in md A/rad2.
This number of significant figures is not really justified but is necessary to give the best reproduction of the observed frequencies and to secure internal consistency in the calculations.
For CH3I, these constants occur only as the combination fihh−fihi=−0.12144. For CH2I2, the value of this combination is −0.16771.
Table VII
Heat content, free energy, entropy, and heat capacity of CH2I2 for the ideal gaseous state at 1-atmos pressure.a
T
(H0−E00)/T
−(F0−E00)/T
S0
Cp0
100
8.70
56.10
64.80
9.63
200
9.63
62.41
72.03
11.62
273.16
10.38
65.52
75.90
13.27
298.16
10.65
66.20
76.84
13.81
300
10.66
66.51
77.17
13.85
400
11.71
69.72
81.43
15.75
500
12.67
72.45
85.12
17.22
600
13.53
74.82
88.35
18.37
700
14.29
76.97
91.26
19.30
800
14.96
78.92
93.89
20.07
900
15.57
80.72
96.29
20.72
1000
16.11
82.39
98.50
21.29
T is in degrees Kelvin and all other quantities are in units of cal deg−1 mole−1.