The Chlorination of N-Methyl Amino Acids with Hypochlorous Acid: Kinetics and Mechanisms

Fruzsina Simon, Eszter Kiss, Mária Szabó, István Fábián

Research output: Contribution to journalArticle

Abstract

The formation and decomposition kinetics of N-chloro-N-methyl amino acids were studied to predict the fate and impact of these compounds in water treatment technologies and biological systems. These compounds form in fast second-order reactions between N-methyl amino acids and hypochlorous acid. The comparison of the activation parameters for the reactions of N-methyl substituted and nonsubstituted branched-chain amino acids reveals the transition-state features less organized structure and stronger bonds between the reactants in the reactions with the N-methyl derivatives. This is due to a combined positive inductive effect of the N-methyl group and the alkyl side chain as well as to the steric effects of the substituents. N-Methyl-N-chloro amino acids decompose much faster than the nonsubstituted compounds. The reaction rates do not depend on the pH, and the same final product is formed in the entire pH range. N-Chlorosarcosine is an exception, as it decomposes via competing paths, kdobs = kd + kdOH[OH-], yielding different final products. This feature is most likely due to the lack of an alkyl substituent on the α-carbon atom. Under physiological pH, aldehydes and methylamine form in these reactions, which are not particularly toxic.

Original languageEnglish
Pages (from-to)2189-2196
Number of pages8
JournalChemical Research in Toxicology
Volume33
Issue number8
DOIs
Publication statusPublished - Aug 17 2020

ASJC Scopus subject areas

  • Toxicology

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