A DFT Study on the Tautomerization of β‐Alanine

Abstract

AbstractTautomerization paths of β‐alanine with explicit inclusion of water molecules, (H2O)n, were investigated by DFT calculations, wB97X‐D/6‐311+G(d,p) SCRF=PCM. Structures of zwitterions of the alanine of trans (t−) and gauche (g−) conformations with seven water molecules (n=7) were examined. On the basis of those geometries, elementary processes of the tautomerization were investigated. For the t‐conformer of β‐alanine, reaction models of n=8, 10, 14, 18 and 24 were scrutinized. While reaction processes are slightly modified with different number of water molecules, n=18 and 24 models afforded three elementary reactions, t‐alanine with cis‐COOH→t‐ion pair→t‐alanine with trans‐COOH→t‐zwitterion. The (H2O)4 hydrogen‐bonded chain participates in the reactions. For the g‐conformer, models of n=7, 10, 14 and 18 were investigated, and the tautomerization was found to take place concertedly via (H2O)2.