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Ab initio study of catalyzed and uncatalyzed amide bond formation as a model for peptide bond formation: Ammonia‐Glycine reactions
Author(s) -
Oie Tetsuro,
Loew Gilda H.,
Burt Stanley K.,
Macelroy Robert D.
Publication year - 1983
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540040402
Subject(s) - chemistry , concerted reaction , catalysis , reaction mechanism , ab initio , transition state , amide , peptide bond , computational chemistry , reaction intermediate , ammonia , molecule , amine gas treating , ab initio quantum chemistry methods , photochemistry , peptide , organic chemistry , biochemistry
As a model reaction for peptide and bond formation, the S N 2 reactions between glycine and ammonia have been studied with and without amine catalysis:\documentclass{article}\pagestyle{empty}\begin{document}$${\rm NH}_3 + {\rm NH}_2 {\rm CH}_2 {\rm COOH} + ({\rm NH}_3 ) \to {\rm NH}_2 {\rm CH}_2 {\rm CONH}_2 + {\rm H}_2 {\rm O} + ({\rm NH}_3 )$$\end{document}using ab initio molecular‐orbital methods. For each of the catalyzed and uncatalyzed reactions, two reaction mechanisms have been examined: a two‐step and a concerted mechanism. The stationary points of each reaction, including intermediate and transition states, have been identified and free energies calculated for all geometry‐optimized reaction species to determine the thermodynamics and kinetics of the reaction. The calculations demonstrate that a second ammonia molecule catalyzes amide bond formation, and that the two‐step mechanism is more favorable than the concerted one for the catalyzed reaction, while for the uncatalyzed reaction both mechanisms are competitive.