Abstract:

Using density functional theory at the level of B3LYP/6-31+g(d,p), we investigated the chiral transition process of the isolated α-alanine molecule. Further more, 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 hydrogen atom on the chiral carbon atom of Sα-alanine molecule can transfer to the other side of the carbon atom via the oxygen atoms of carboxyl atoms as a bridge, to achieve the chiral transition of α-alanine molecule from Stype to Rtype. On this path there is one intermediate and two transition states. The biggest reaction energy barrier is 326.6 kJ/mol derived from the first transition state TS1.

Key words: chiral, α-alanine, density functional theory (DFT), transition state, frontier molecular orbital