cubical grid of step size smaller than 0.1 bohr. In this framework, the reaction
mechanism can be rationalized in terms of chemical events (bond forming or
breaking processes, creation and annihilation of electron pairs) that drive the
chemical rearrangement. This analysis allows us to understand the electronic
structure and related properties of the reactants as the reaction takes place, providing a further understanding of the chemical reactivity. Starting from the TS, the
reaction path has been traced following the intrinsic reaction coordinate (IRC) [179,
180] using a Rx in mass-weighted step of 0.1 amu
1/2 bohr until reaching the
minimum or until a maximum of 100 steps have been done.
10.5.2.1 Mechanism A, First Step
As explained above, the mechanism A is a stepwise process, whose first step
accounts for the water elimination from glycolic acid to form the α-lactone intermediate. The energy profile along the IRC path down from TS1 to the glycolic acid
in one side, and to the α-lactone intermediate in the other side, is reported in
Fig. 10.6, together with the structural stability domains (SSD) found.
For the process leading from glycolic acid to the α-lactone intermediate through
TS1, seven SSDs have been characterized, and they are indicated in Fig. 10.6.
The series of SSDs found can be viewed as a sequence of chemical events
depicted in Scheme 10.2, which has been represented according to the perspective
of the ELF analysis. In Scheme 10.2 the full lines and the points represent disynaptic and monosynaptic basins, respectively, and the hydrogenated basins have
been represented with ellipses.
O 5
C 3
C 2
H 8
H 9
O 4
O1
H 6
H 7
TS1
-H 2 O
C 3
C 2
H8
H 9
O 4
O 1
TS4
C 3
C 2
H 8
H 9
O 4
O 1
+
Mechanism A
O 5
C 3
C 2
H8
H 9
O 4
O 1
H 6
H 7
TS2
-H 2 O
C 3
C 2
H 8
H 9
O 1
O 4
TS4
C 3
C 2
H 8
H 9
O 1
O 4
+
Mechanism B
O 5
C 3
C 2
H 8
H 9
O 4
O 1
TS3
C 3
C 2
H 8
H 9
O 5
O 4
+
Mechanism C
H 7
H 6
H 7
O 1
+
H 6
Scheme 10.1 The three mechanisms studied and the atom numbering used
10 Quantum Chemical Topology Approach …
271
mechanism can be rationalized in terms of chemical events (bond forming or
breaking processes, creation and annihilation of electron pairs) that drive the
chemical rearrangement. This analysis allows us to understand the electronic
structure and related properties of the reactants as the reaction takes place, providing a further understanding of the chemical reactivity. Starting from the TS, the
reaction path has been traced following the intrinsic reaction coordinate (IRC) [179,
180] using a Rx in mass-weighted step of 0.1 amu
1/2 bohr until reaching the
minimum or until a maximum of 100 steps have been done.
10.5.2.1 Mechanism A, First Step
As explained above, the mechanism A is a stepwise process, whose first step
accounts for the water elimination from glycolic acid to form the α-lactone intermediate. The energy profile along the IRC path down from TS1 to the glycolic acid
in one side, and to the α-lactone intermediate in the other side, is reported in
Fig. 10.6, together with the structural stability domains (SSD) found.
For the process leading from glycolic acid to the α-lactone intermediate through
TS1, seven SSDs have been characterized, and they are indicated in Fig. 10.6.
The series of SSDs found can be viewed as a sequence of chemical events
depicted in Scheme 10.2, which has been represented according to the perspective
of the ELF analysis. In Scheme 10.2 the full lines and the points represent disynaptic and monosynaptic basins, respectively, and the hydrogenated basins have
been represented with ellipses.
O 5
C 3
C 2
H 8
H 9
O 4
O1
H 6
H 7
TS1
-H 2 O
C 3
C 2
H8
H 9
O 4
O 1
TS4
C 3
C 2
H 8
H 9
O 4
O 1
+
Mechanism A
O 5
C 3
C 2
H8
H 9
O 4
O 1
H 6
H 7
TS2
-H 2 O
C 3
C 2
H 8
H 9
O 1
O 4
TS4
C 3
C 2
H 8
H 9
O 1
O 4
+
Mechanism B
O 5
C 3
C 2
H 8
H 9
O 4
O 1
TS3
C 3
C 2
H 8
H 9
O 5
O 4
+
Mechanism C
H 7
H 6
H 7
O 1
+
H 6
Scheme 10.1 The three mechanisms studied and the atom numbering used
10 Quantum Chemical Topology Approach …
271