Parity-violating energy for the chirality-producing step in Strecker synthesis of l-alanine

Abstract

The potential energy curve for the reaction of the ethaniminium ion (CH3CHNH2+) and the cyanide anion (CN−) to give 2-amino-propanenitrile (APN) in aqueous solution which is the chirality-producing step of Strecker synthesis of l-alanine was obtained by ab initio GB 6-31G∗∗ calculation including the solvent effect. The transition state was located at 2.13Å of the Cα–C(N) distance. The barrier height for this reaction was 16.6kcal/mol and the reaction is expected to occur easily in aqueous solution. The parity-violating interaction energy (Epv) was calculated by using the spin–orbit-coupling SCF wavefunction and the [5s2p1d/3s1p] basis set. The Epv value of the association state of the two ions is zero, while the reaction product l-APN has the positive value of +0.17×10−20hartree. Epv was positive for all reaction stages including the transition state, suggesting that the formation of l-APN is not more favorable than d-APN in the Strecker synthesis of alanine due to the parity-violating weak neutral current interaction.