Chemistry Reference
In-Depth Information
17.5 C
5
H
2
ISOMERS
17.5.1 I
NTRODUCTION
Whereas C
3
H
2
and C
4
H
2
molecules have been found in interstellar media
and in atmospheres of the giant planets of the Solar System and their
satellites, this is not the case for C
5
H
2
. Only an upper limit of its abundance
in the pre-protostellar core TMC-1 was reported [113]. However, the open
molecule 5O1(s) and the highly polar ring-chain molecule 5C9(s) were
detected in the laboratory in a diacetylene-neon discharge [114]. Experi-
mental evidence for the existence of three isomeric C
5
H
2
molecules was
reported [115]. Results of theoretical calculations for C
5
H
2
isomers are
available [7,17,115]. Rotational constants for 5O2(s) are available [69].
As stated in the introduction, we have treated with quantum mechanical
calculations all but the branched open constructs of the formula C
5
H
2
.
These 41 constructs produced 16 molecules of which five are open and 11
cyclic. Because of this large number we present our results and literature
data in a different format as follows: 1. open molecules, Tables 17.18 and
17.19
;
2. cyclic molecules with one five-ring,
Tables 17.20
and
17.21
;
3. cyclic
molecules with one four-ring,
Tables 17.22
and
17.23
;
4. cyclic molecules
TABLE 17.18
Relative SCF Energy, Zero Point Vibrational Energy (ZPVE), and Dipole
Moment of the Open C
5
H
2
Molecules
"ESCF (kJ mol
1
)
ZPVE (kJ mol
1)
Molecule
Dipole (debye)
Reference
5O1(t)
0.00
96.75
0.00
This work
5O1(t)
0.00
93.847
-
[7]
5O1(t)
0.00
103.13
-
[115]
5O2(s)
56.3
107.99
6.05
This work
5O2(s)
-
-
5.9
[69]
5O2(s)
63.0
106.69
5.584
[7]
-
74.4
-
5.792
-
-
57.8
-
5.829
-
29.3
a
5O2(s)
109.92
-
[115]
5O3(s)
84.7
108.39
5.27
This work
5O3(s)
58.33
107.53
4.461
[7]
-
69.54
-
4.616
-
-
70.21
-
4.787
-
33.5
a
5O3(s)
110.43
-
[115]
5O4(s)
274
104.44
3.14
This work
5O5(s)
232
103.06
5.11
This work
Note: E
SCF
of 5O1(t):
191.560863 hartree (this work).
a
Includes zero-point energy correction. Fan and Pfeiffer [17] have reported calculated total
energies for 5O1(t) only.
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