Chemistry Reference
In-Depth Information
Table 19 Symmetry analysis of the twisted to
anti
-folded conformational isomerization
Permutation-inversion operators
E
, (18)(1
0
8
0
), (11
0
)(88
0
)(99
0
), (18
0
)(81
0
)(99
0
)
Symmetry operators of t-
D
2
E
, (11
0
)(88
0
)(99
0
), (18)(1
0
8
0
)*, (18
0
)(81
0
)(99
0
)*
Symmetry operators of a-
C
2h
(
y
)
E
, (11
0
)(88
0
)(99
0
)
Largest common subgroup
Table 20 Possible point groups and conformations of the transition state for interconversion of
the t-
D
2
twisted and a-
C
2h
(
y
)
anti
-folded conformations
Group of permutation-inversion operators
a
b
TS
h
TS
n
TS
{
E
, (11
0
)(88
0
)(99
0
)} ta-
C
2
(
y
) 2 8
C
2
(
y
) A
{
E
} ft-
C
1
1 16
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
])
Fig. 35 Schematic
mechanism for the
interconversion of the t-
D
2
twisted and a-
C
2h
(
y
)
anti
-
folded conformations via a
transition state ta-
C
2
(
y
)
1'
1'
1
1'
1
ta
Z-RPR'
ta
1
Z-RMR'
a
Z-RR'
1'
1
1'
1
t
t
Z-P
Z-M
1
1'
1
1'
1'
1
ta
ta
a
Z-SPS'
Z-SMS'
Z-SS'
1'
1'
1
1'
1
ta
ta
E-RPS'
E-RMS'
1
a
E-RS'
1'
1
1
1'
t
t
E-P
E-M
1
1
1'
1
1'
ta
1'
ta
a
E-SPR'
E-SMR'
E-SR'
interconvert independently via analogous mechanisms. Fig.
36
may be derived
from Fig.
35
by replacing each transition state and the corresponding pathway by
two. In one transition state the first tricyclic moiety is more folded than the second,
while in the other transition state the second moiety is more folded than the first.
