S. Okovytyy
302
the activation barrier is as small as 2.38 kJ/mol, which is not quite consistent with
the experimental data [27]. In addition, the ∆Н
≠
values for compounds (9, 10) are
considerably underestimated.
The supermolecular approximation provides a more appropriate description of
specific solvation and reaction mechanisms, where solvent molecules are considered to be reagents. Successful application of the supermolecular approach requires
Table 10.4 Calculated geometric parameters of transition states for opening of the oxirane ring
and corresponding activation barriers for compounds (1, 3–10) [30]
Compound
no.
Bond length (Å)
Angle (deg.)
∆Н
≠
(kJ/mol)
СО 1
СО 2
ССО 1
β
γ
In vacuo
1
1.740
1.995
74.5
167.9
175.6
108.74
3
1.779
2.071
76.1
147.8
−157.6
133.55
4
1.775
2.005
76.6
150.9
−158.5
129.91
5
a
1.787
2.000
76.8
152.5
159.6
120.58
6
1.837
2.036
79.3
148.8
162.8
134.08
7
1.854
2.058
80.3
144.0
−142.7
141.24
8
1.876
2.064
81.5
144.4
−144.9
135.60
9
1.867
2.043
81.2
148.0
−148.5
136.20
10
1.737
1.982
74.1
159.3
175.1
115.23
Macroscopic approximation
1
1.772
2.065
76.1
154.7
179.5
128.24
3
1.841
2.193
79.0
142.3
−153.1
149.66
4
1.832
2.142
79.1
145.8
−157.6
156.98
5
a
1.826
2.101
78.7
148.1
−151.7
150.37
6
1.873
2.124
81.3
147.8
−151.5
127.32
7
1.893
2.155
82.2
139.3
−137.2
169.74
8
1.981
2.292
87.0
137.0
−136.8
172.05
9
1.903
2.152
82.8
144.0
−144.5
132.97
10
1.775
2.014
75.9
159.5
176.1
149.62
Supermolecular approximation
1
1.862
1.991
81.3
156.0
179.6
141.46
3
1.950
2.088
85.5
147.5
16.1
179.79
4
1.890
2.046
82.2
145.0
157.8
163.43
5
a
1.892
2.030
82.3
143.3
155.5
188.28
6
2.046
2.298
91.1
143.7
138.8
205.23
7
2.078
2.205
92.8
134.5
124.3
214.85
8
2.015
2.190
89.4
138.4
134.3
198.76
9
1.871
1.993
81.1
158.1
174.8
148.82
a
For the reaction at C 1 (favorable attack); the value of ΔH
≠
for gas-phase attack on C 2 is equal
to 129.12 kJ/mol
302
the activation barrier is as small as 2.38 kJ/mol, which is not quite consistent with
the experimental data [27]. In addition, the ∆Н
≠
values for compounds (9, 10) are
considerably underestimated.
The supermolecular approximation provides a more appropriate description of
specific solvation and reaction mechanisms, where solvent molecules are considered to be reagents. Successful application of the supermolecular approach requires
Table 10.4 Calculated geometric parameters of transition states for opening of the oxirane ring
and corresponding activation barriers for compounds (1, 3–10) [30]
Compound
no.
Bond length (Å)
Angle (deg.)
∆Н
≠
(kJ/mol)
СО 1
СО 2
ССО 1
β
γ
In vacuo
1
1.740
1.995
74.5
167.9
175.6
108.74
3
1.779
2.071
76.1
147.8
−157.6
133.55
4
1.775
2.005
76.6
150.9
−158.5
129.91
5
a
1.787
2.000
76.8
152.5
159.6
120.58
6
1.837
2.036
79.3
148.8
162.8
134.08
7
1.854
2.058
80.3
144.0
−142.7
141.24
8
1.876
2.064
81.5
144.4
−144.9
135.60
9
1.867
2.043
81.2
148.0
−148.5
136.20
10
1.737
1.982
74.1
159.3
175.1
115.23
Macroscopic approximation
1
1.772
2.065
76.1
154.7
179.5
128.24
3
1.841
2.193
79.0
142.3
−153.1
149.66
4
1.832
2.142
79.1
145.8
−157.6
156.98
5
a
1.826
2.101
78.7
148.1
−151.7
150.37
6
1.873
2.124
81.3
147.8
−151.5
127.32
7
1.893
2.155
82.2
139.3
−137.2
169.74
8
1.981
2.292
87.0
137.0
−136.8
172.05
9
1.903
2.152
82.8
144.0
−144.5
132.97
10
1.775
2.014
75.9
159.5
176.1
149.62
Supermolecular approximation
1
1.862
1.991
81.3
156.0
179.6
141.46
3
1.950
2.088
85.5
147.5
16.1
179.79
4
1.890
2.046
82.2
145.0
157.8
163.43
5
a
1.892
2.030
82.3
143.3
155.5
188.28
6
2.046
2.298
91.1
143.7
138.8
205.23
7
2.078
2.205
92.8
134.5
124.3
214.85
8
2.015
2.190
89.4
138.4
134.3
198.76
9
1.871
1.993
81.1
158.1
174.8
148.82
a
For the reaction at C 1 (favorable attack); the value of ΔH
≠
for gas-phase attack on C 2 is equal
to 129.12 kJ/mol