MP2 study of the gas phase elimination mechanism of some neutral amino acids and their ethyl esters

The mechanisms of the gas phase elimination of N , N ‐dimethylglycine, picolinic acid, and N ‐phenylglycine and their ethyl esters have been examined at Möller–Plesset MP2/6‐31G (d, p) level of theory. The ethyl esters of these 2‐amino carboxylic acids produce the corresponding amino carboxylic acid and ethylene in a rate‐determining step. However, the unstable intermediate amino carboxylic acid rapidly decarboxylate to give the corresponding amino compound. These calculations imply a concerted, semi‐polar six‐membered cyclic transition state type of mechanism for the ethyl esters, and a non‐synchronous five‐membered cyclic transition state for the amino acids decarboxylation. The present results support previous mechanistic consideration of the elimination of the above‐mentioned compounds in the gas phase. Copyright © 2008 John Wiley & Sons, Ltd.