Abstract:

Using B3LYP methods of density functional theory, we investigated the chiral transition process of nonrestricted area monomer isoleucine molecule
at the 6-311+G(-2df-) basis set level. A complete chiral transition path reaction potential energy surface was drawn by looking for the extreme value point structures including the transition state and intermediate, and the geometry and electronic structure properties of extreme value points were also analyzed. The results show that the H atom on the chiral C  atom of Sisoleucine molecule can transfer to the other side of the C atom via the O atoms of carboxyl atoms as a bridge, to achieve the chiral transition of isoleucine molecule from Stype to Rtype. There are four intermediates and five transition states on this path under the condition of nonrestricted area. The biggest reaction energy barrier is 325.824 6 kJ/mol derived from the second transition state TS₂-S-Ile.

Key words: chiral, isoleucine, transition state, non-restricted area