Chemistry Reference
In-Depth Information
Table 9 Possible point groups and conformations of the transition state for conformational
inversion of the
anti
-folded conformation a-
C
2h
(
y
)
Group of permutation-inversion operators
h
TS
n
TS
Cp
a
b
TS
{
E
, (18)(1
0
8
0
), (11
0
)(88
0
)(99
0
), (18
0
)(81
0
)(99
0
),
E
*, (18)(1
0
8
0
)*, (11
0
)(88
0
)(99
0
)*, (18
0
)(81
0
)(99
0
)*}
p-
D
2h
8
2
1 1
C
2h
(
y
)B
2g
{
E
, (18)(1
0
8
0
), (11
0
)(88
0
)(99
0
), (18
0
)(81
0
)(99
0
)}
t-
D
2
4
4
1 2
C
2
(
y
)B
2
{
E
, (18)(1
0
8
0
),
E
*, (18)(1
0
8
0
)*}
p-
C
2v
(
z
)4 412
C
s
(
xz
)B
1
{
E
, (11
0
)(88
0
)(99
0
),
E
*, (11
0
)(88
0
)(99
0
)*}
p-
C
2v
(
y
)4 412
C
2
(
y
)A
2
{
E
, (18
0
)(81
0
)(99
0
), (18)(1
0
8
0
)*,
(11
0
)(88
0
)(99
0
)*}
s-
C
2v
(
x
)4 412
C
s
(
xz
)B
2
{
E
, (18)(1
0
8
0
), (11
0
)(88
0
)(99
0
)*, (18
0
)(81
0
)(99
0
)}
pt-
C
2h
(
z
)4 4 12
C
i
B
g
{
E
, (11
0
)(88
0
)(99
0
), (18)(1
0
8
0
)*,
(18
0
)(81
0
)(99
0
)*}
a-
C
2h
(
y
)4 412
C
2h
(
y
)A
g
{
E
, (18
0
)(81
0
)(99
0
),
E
*, (18
0
)(81
0
)(99
0
)*}
p-
C
2h
(
x
)4 412
C
i
B
g
{
E
, (18)(1
0
8
0
)}
t-
C
2
(
z
) 2814
C
1
B
{
E
, (11
0
)(88
0
)(99
0
)}
ta-
C
2
(
y
)2 814
C
2
(
y
)A
{
E
, (18
0
)(81
0
)(99
0
)}
ts-
C
2
(
x
)2 814
C
1
B
{
E
,
E
*}
p-
C
s
(
yz
)2 814
C
1
A”
{
E
, (18)(1
0
8
0
)*}
f-
C
s
(
xz
)2 814
C
s
(
xz
)A'
{
E
, (11
0
)(88
0
)(99
0
)*}
s-
C
s
(
xy
)2 814
C
1
A”
{
E
, (18
0
)(81
0
)(99
0
)*}
a-
C
i
2
8
1 4
C
i
A
g
{
E
}
ft-
C
1
1618
C
1
A
a
Point group symmetry along pathway from transition state to reactant or product, i.e., maximum
common subgroup of transition state and reactant or product
b
Symmetry species of the mode of the transition vector (using the conventional setting of the
transition state point group [
279
])
Conformational Inversion of the
anti
-Folded Conformation
In a conformational inversion of the
anti
-folded conformation the folding direction
of both moieties is inverted simultaneously. The
E
-or
Z
-configuration of the
version is not affected. The symmetry operators of a-
C
2h
(
y
),
E
, (11
0
)(88
0
)(99
0
),
(18)(1
0
8
0
)*, (18
0
)(81
0
)(99
0
)*, and the permutation-inversion operators resulting in a
conformational inversion, (18)(1
0
8
0
), (18
0
)(81
0
)(99
0
),
E*
, (11
0
)(88
0
)(99
0
)*, combined
give the point group
D
2h
. This is the highest possible symmetry for the transition
state. Subgroups of
D
2h
may also be considered. All possible groups of
permutation-inversion operators and the corresponding transition state conforma-
tion and point group are listed in Table
9
. The order of the transition state point
group
h
TS
, the number of versions of this transition state
n
TS
- see (
3
), the
connectivity
C
, and the number of parallel pathways
p
- see (
4
), the point group
symmetry along the pathways from the transition state to the educt and product, and
the symmetry species of the transition vector are also given.
The highest possible symmetry for a transition state is p-
D
2h
(
h
TS
¼
8). There
are
n
TS
¼
2 versions of this conformation corresponding to an
E
- and a
Z
-config-
uration. Equation (
4
) predicts a connectivity
C
1).
The connectivity of the four versions of the a-
C
2h
(
y
)
anti
-folded conformation via
this process and its mechanism are schematically shown in Fig.
23
.
¼
1 and only one pathway (
p
¼
