Hydrogen abstraction by chlorine atom from amino acids: Remarkable influence of polar effects on regioselectivity

Robert J. Oreilly, Bun Chan, Mark S. Taylor, Sandra Ivanic, George B. Bacskay, Christopher J. Easton, Leo Radom

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31 Citations (Scopus)

Abstract

Quantum chemistry computations have been used to investigate hydrogen-atom abstraction by chlorine atom from protonated and N-acetylated amino acids. The results are consistent with the decreased reactivity at the backbone α-carbon and adjacent side-chain positions that is observed experimentally. The individual effects of NH 3 +, COOH, and NHAc substituents have been examined and reveal important insights. The NH 3 + group in isolation is found to be deactivating at the α-position, while the acetamido group is activating. For the COOH group, polar effects lead to a contrathermodynamic deactivation of the thermodynamically most favorable α-abstraction. In the N-acetylamino acid, the α-position is deactivated by the combined inductive effect of the substituents and the presence of an early transition structure, again overriding the greater thermodynamic stability of the α-centered radical product. Deactivation of the α-, β-, and γ-positions results in a peculiar stability for amino acids and peptides and their derivatives with respect to radical degradation.

Original languageEnglish
Pages (from-to)16553-16559
Number of pages7
JournalJournal of the American Chemical Society
Volume133
Issue number41
DOIs
Publication statusPublished - Oct 19 2011

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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    Oreilly, R. J., Chan, B., Taylor, M. S., Ivanic, S., Bacskay, G. B., Easton, C. J., & Radom, L. (2011). Hydrogen abstraction by chlorine atom from amino acids: Remarkable influence of polar effects on regioselectivity. Journal of the American Chemical Society, 133(41), 16553-16559. https://doi.org/10.1021/ja205962b