At the glycolic acid, the first point of the SSD-I, nineteen basins can be found,
corresponding to the five core basins, five disynaptic basins (accounting for the C–C
bond, the two C–O bonds and two basins for the C=O double bond), four hydrogenated basins, and five monosynaptic basins associated with the oxygen atoms lone
pairs. In particular, we have found two monosynaptic basins corresponding to the O4
atom, also two monosynaptic basins for the O5 oxygen atom, and only one
monosynaptic basin corresponding to the O1 atom.
The first topological change connecting SSD-I and SSD-II is associated with a
cusp-type catastrophe. The disynaptic basin V(O1,H6) splits in two monosynaptic
-303.5
-303.49
-303.48
-303.47
-303.46
-303.45
-303.44
-303.43
-303.42
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
Total Energy (Hartree)
Reaction Coordinate (amu
1/2 bohr)
SSD-I
SSD-II
SSD-III
SSD-IV
SSD-V
SSD-VI
SSD-VII
Fig. 10.6 Energy profile for the water elimination from glycolic acid (left side) to obtain the
α-lactone intermediate through TS1, calculated by means of the IRC method. The SSDs found are
indicated
O 5
C 3
C 2
O 4
O 1
H 6
H 9
H 8
H 7
SSD-I
O 5
C 3
C 2
O 4
O 1
H 6
H 9
H 8
H 7
SSD-II
O 5
C 3
C 2
O 4
O 1
H 6
H 9
H 8
H 7
SSD-III
O 5
C 3
C 2
O 4
O 1
H 6
H 9
H 8
H 7
SSD-IV
O 5
C 3
C 2
O 4
O 1
H 6
H 9
H 8
H 7
SSD-V
O 5
C 3
C 2
O 4
O 1
H 6
H 9
H 8
H 7
SSD-VI
O 5
C 3
C 2
O 4
O 1
H 6
H 9
H 8
H 7
SSD-VII
Scheme 10.2 Representation of the first step of the glycolic acid decomposition through the
mechanism A, depicted from the ELF viewpoint
272
J. Andrés et al.