The formation of N-chloramines with proteinogenic amino acids

Mária Szabó, Fruzsina Simon, I. Fábián

Research output: Contribution to journalArticle

Abstract

In this study, the formation of 17 N-chloramines from proteinogenic amino acids and HOCl was studied by direct kinetic method in the pH = 3–13 range. Thus, the uncertainties associated with the indirect methods used in some of the previous studies were eliminated. Each reaction proceeds according to an overall second order kinetics: v = − k [HOCl][R–NH2] and the rate constants are several times 107 M−1s−1. A very slight correlation was found between the lgk and the pKAA of the amino acids. The results make possible to predict the reactivity order of the amino acids toward HOCl under various conditions. A comparison of the parameters of activation indicates that the presence of a bulky substituent on the side chain close to the α-carbon atom decreases the strength of bonding between the reactants and make the structure more diffuse in the transition state. The chlorination of histidine proceeds via two pH dependent paths presumably leading to the formation of N-chloramine and a side chain chlorinated product. The latter compound may be involved in fast subsequent trans-chlorination reactions. The results presented here resolve earlier discrepancies in the literature and are relevant in chlorination water treatment technologies as well as in the interpretation of in vivo processes involving the formation of N-chloro amino acids in a wide pH range.

Original languageEnglish
Article number114994
JournalWater Research
Volume165
DOIs
Publication statusPublished - Nov 15 2019

Fingerprint

Amino acids
Chlorination
chlorination
amino acid
kinetics
Kinetics
Water treatment
Rate constants
water treatment
Chemical activation
Atoms
Carbon
carbon
method

Keywords

  • Chlorination
  • Hypochlorous acid
  • Kinetics
  • N-Chloro-amino acid
  • pH dependence
  • Stopped-flow method

ASJC Scopus subject areas

  • Ecological Modelling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

Cite this

The formation of N-chloramines with proteinogenic amino acids. / Szabó, Mária; Simon, Fruzsina; Fábián, I.

In: Water Research, Vol. 165, 114994, 15.11.2019.

Research output: Contribution to journalArticle

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N2 - In this study, the formation of 17 N-chloramines from proteinogenic amino acids and HOCl was studied by direct kinetic method in the pH = 3–13 range. Thus, the uncertainties associated with the indirect methods used in some of the previous studies were eliminated. Each reaction proceeds according to an overall second order kinetics: v = − k [HOCl][R–NH2] and the rate constants are several times 107 M−1s−1. A very slight correlation was found between the lgk and the pKAA of the amino acids. The results make possible to predict the reactivity order of the amino acids toward HOCl under various conditions. A comparison of the parameters of activation indicates that the presence of a bulky substituent on the side chain close to the α-carbon atom decreases the strength of bonding between the reactants and make the structure more diffuse in the transition state. The chlorination of histidine proceeds via two pH dependent paths presumably leading to the formation of N-chloramine and a side chain chlorinated product. The latter compound may be involved in fast subsequent trans-chlorination reactions. The results presented here resolve earlier discrepancies in the literature and are relevant in chlorination water treatment technologies as well as in the interpretation of in vivo processes involving the formation of N-chloro amino acids in a wide pH range.

AB - In this study, the formation of 17 N-chloramines from proteinogenic amino acids and HOCl was studied by direct kinetic method in the pH = 3–13 range. Thus, the uncertainties associated with the indirect methods used in some of the previous studies were eliminated. Each reaction proceeds according to an overall second order kinetics: v = − k [HOCl][R–NH2] and the rate constants are several times 107 M−1s−1. A very slight correlation was found between the lgk and the pKAA of the amino acids. The results make possible to predict the reactivity order of the amino acids toward HOCl under various conditions. A comparison of the parameters of activation indicates that the presence of a bulky substituent on the side chain close to the α-carbon atom decreases the strength of bonding between the reactants and make the structure more diffuse in the transition state. The chlorination of histidine proceeds via two pH dependent paths presumably leading to the formation of N-chloramine and a side chain chlorinated product. The latter compound may be involved in fast subsequent trans-chlorination reactions. The results presented here resolve earlier discrepancies in the literature and are relevant in chlorination water treatment technologies as well as in the interpretation of in vivo processes involving the formation of N-chloro amino acids in a wide pH range.

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