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Simon F, Fábián I, Szabó M. Oxidation of branched chain amino acids by HOCl: Kinetics and mechanism. JOURNAL OF HAZARDOUS MATERIALS 2024; 470:134145. [PMID: 38565013 DOI: 10.1016/j.jhazmat.2024.134145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 03/13/2024] [Accepted: 03/26/2024] [Indexed: 04/04/2024]
Abstract
The kinetics of the chlorination of leucine, isoleucine, and valine (BCAAs) was studied in excess HOCl by stopped-flow and spectrophotometric methods (25 ◦C, I = 1.0 M NaClO4). The intermediates and products were identified and monitored by 1H NMR spectroscopy. It was established that these reactions are fully analogous and proceed according to distinct mechanisms under alkaline and neutral conditions. At high pH, the formation and subsequent rate determining decomposition of N-monochloroamino acid control the process. The decomposition occurs via competing pH-independent and OH--assisted reaction paths and the sequence of chlorination, dichlorination and decarboxylation steps leads to the formation of N-chloroimines and their carbanionic forms, which are in fast acid - base equilibria. The dechlorination of the carbanions yields nitriles as the main products. The hydration of the N-chloro imines produces chloramine and aldehydes which are involved in further oxidation reactions with HOCl. The formation of chloroform and chloroacetaldehyde was confirmed in each system. At pH 7.0, the N-chloro derivatives of BCAAs form immediately and are converted into the corresponding N,N-dichloro species within a few seconds after mixing the reactants. In this reaction, the reactive form of the oxidant is Cl2O. The first-order decomposition of the dichloroamino acids occurs on stopped-flow timescale (k = 0.5 - 0.7 s-1) and yields N-chloroimines which slowly decompose with a characteristic first-order rate constant on the order of a few times 10-5 s-1. The main products are the corresponding nitriles that account for about 80% and 60% of the original amounts of amino acids under neutral and alkaline (cOH- = 5.00 × 10-2 M) conditions, respectively. Aldehydes, carboxylic acids, chloroform and NCl3 were also identified as by-products. The results unequivocally confirm that harmful chlorinated species may form from amino acids long after the chlorination step in water treatment technologies that deteriorates the quality of the finished water. ENVIRONMENTAL IMPLICATION: In source waters, amino acids account for about 75% of the total dissolved nitrogen. Therefore, it is an essential issue how the reactions of these compounds with hypochlorite ion can be controlled to avoid the formation of toxic compounds. The compounds formed from BCAAs are considered to be harmful both under alkaline and neutral conditions (chloroacetaldehyde, chloroform, nitriles). However, some of the intermediates have extended lifetime in these systems and they may also react with other components of raw water during water treatment processes.
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Affiliation(s)
- Fruzsina Simon
- HUN-REN-UD Mechanisms of Complex Homogeneous and Heterogeneous Chemical, Reactions Research Group, University of Debrecen, Debrecen, Hungary
| | - István Fábián
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary; HUN-REN-UD Mechanisms of Complex Homogeneous and Heterogeneous Chemical, Reactions Research Group, University of Debrecen, Debrecen, Hungary
| | - Mária Szabó
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary; HUN-REN-UD Mechanisms of Complex Homogeneous and Heterogeneous Chemical, Reactions Research Group, University of Debrecen, Debrecen, Hungary.
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2
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Tran NH, Mosa FES, Barakat K, El-Kadi AOS, Whittal R, Siraki AG. Comparing the oxidative functions of neutrophil myeloperoxidase and cytochrome P450 enzymes in drug metabolism. Chem Biol Interact 2024; 392:110942. [PMID: 38458309 DOI: 10.1016/j.cbi.2024.110942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 02/14/2024] [Accepted: 03/06/2024] [Indexed: 03/10/2024]
Abstract
Drug metabolism is an essential process that chemically alters xenobiotic substrates to activate or terminate drug activity. Myeloperoxidase (MPO) is a neutrophil-derived haem-containing enzyme that is involved in killing invading pathogens, although consequentially, this same oxidative activity can produce metabolites that damage host tissue and play a role in various human pathologies. Cytochrome P450s (CYPs) are a superfamily of haem-containing enzymes that are significantly involved in the metabolism of drugs by functioning as monooxygenases and can be induced or inhibited, resulting in significant drug-drug interactions that lead to unanticipated adverse drug reactions. In this review, the functions of drug metabolism of MPO and CYPs are explored, along with their involvement and association for common enzymatic pathways by certain xenobiotics. MPO and CYPs metabolize numerous xenobiotics, although few reported studies have made a direct comparison between both enzymes. Additionally, we employed molecular docking to compare the active site and haem prosthetic group of MPO and CYPs, supporting their similar catalytic activities. Furthermore, we performed LCMS analysis and observed a shared hydroxylated mefenamic acid metabolite produced in both enzymatic systems. A proper understanding of the enzymology and mechanisms of action of MPO and CYPs is of significant importance when enhancing the beneficial functions of drugs in health and diminishing their damaging effects on diseases. Therefore, awareness of drugs and xenobiotic substrates involved in MPO and CYPs metabolism pathways will add to the knowledge base to foresee and prevent potential drug interactions and adverse events.
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Affiliation(s)
- Newton H Tran
- Faculty of Pharmacy and Pharmaceutical Sciences, College of Health Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Farag E S Mosa
- Faculty of Pharmacy and Pharmaceutical Sciences, College of Health Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Khaled Barakat
- Faculty of Pharmacy and Pharmaceutical Sciences, College of Health Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Ayman O S El-Kadi
- Faculty of Pharmacy and Pharmaceutical Sciences, College of Health Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Randy Whittal
- Department of Chemistry, Faculty of Sciences, College of Natural and Applied Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Arno G Siraki
- Faculty of Pharmacy and Pharmaceutical Sciences, College of Health Sciences, University of Alberta, Edmonton, Alberta, Canada.
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Simon F, Szabó M, Fábián I. The chlorination of glycine and α-alanine at excess HOCl: Kinetics and mechanism. JOURNAL OF HAZARDOUS MATERIALS 2023; 447:130794. [PMID: 36669404 DOI: 10.1016/j.jhazmat.2023.130794] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 01/08/2023] [Accepted: 01/12/2023] [Indexed: 06/17/2023]
Abstract
The chlorination of the two simplest amino acids at HOCl excess was studied by stopped-flow, conventional spectrophotometric and time resolved 1H NMR kinetic methods at 25 °C. These reactions show distinct characteristics under neutral and alkaline conditions. At high pH, the common feature of the two systems is that the N-dichloroamino carboxylate ion does not form and the overall process is controlled by the initial decomposition of the N-monochloro derivative. Under such conditions, carbanions form in equilibrium acid - base processes and open alternative reaction paths, resulting in enhanced complexity of the corresponding mechanisms. In the case of α-alanine, the formation of acetonitrile and N-chloro acetamide as main products; acetate ion, acetaldehyde, chloroacetaldehyde, chloroform as byproducts; acetamide and N-chloro ethanimine as intermediates was confirmed. In the case of glycine, the final products are formamide and OCN-. Under neutral conditions, monochloroamino acid forms immediately upon mixing the reactants, and subsequently it is converted into dichloroamino acid by Cl2O in a fast process. In considerably slower further reaction steps, acetonitrile and acetate ion form as final products in the α-alanine system, while the chlorination of glycine proceeds to full mineralization. The detailed mechanisms suggested for these reactions postulate the formation of various imines and N-chloro imines which are involved in decarboxylation, dechlorination, hydration and hydrolytic reaction steps.
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Affiliation(s)
- Fruzsina Simon
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary; ELKH - DE Mechanisms of Complex Homogeneous and Heterogeneous Chemical Reactions Research Group, University of Debrecen, Debrecen, Hungary
| | - Mária Szabó
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary; ELKH - DE Mechanisms of Complex Homogeneous and Heterogeneous Chemical Reactions Research Group, University of Debrecen, Debrecen, Hungary.
| | - István Fábián
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary; ELKH - DE Mechanisms of Complex Homogeneous and Heterogeneous Chemical Reactions Research Group, University of Debrecen, Debrecen, Hungary
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Truzsi A, Kovács B, Bodnár I, Fábián I. Controlling the formation of halogenated byproducts in the chlorination of source waters by oxidative pre-treatment with the Fe(II)/Fe(III)-S(IV)-air system. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2022; 244:114036. [PMID: 36049334 DOI: 10.1016/j.ecoenv.2022.114036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 08/22/2022] [Accepted: 08/26/2022] [Indexed: 06/15/2023]
Abstract
Breakpoint chlorination is a generally accepted method for removing ammonium ion from source waters in drinking water treatment technologies. This process is often accompanied by the formation of halogenated organic byproducts. The presence of these compounds in potable water is of primary concern. In this paper, we demonstrate that the concentration of the precursors of the halogenated species can sufficiently be decreased by oxidizing the organic pollutants with the Fe(II)/Fe(III) - S(IV) - air system. Pre-oxidative treatment of the source waters results in a substantial reduction of chemical oxygen demand, while the ammonium ion concentration remains unaffected. The breakpoint chlorination produces substantially less trihalomethanes (THMs) and adsorbable halogenated organic compounds (AOXs) in oxidatively pre-treated source waters than in raw waters. These results offer a possibility to improve drinking water treatment technologies for better controlling the formation of antagonistic byproducts. It is demonstrated that reaching the regulated concentration levels of THMs is feasible with this method even in source waters containing organic pollutants at relatively high concentration levels. The main advantage of the procedure is that the reagents used for the oxidative pre-treatment are converted into non-toxic products (Fe(III) and SO42-) by the end of the process.
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Affiliation(s)
- Alexandra Truzsi
- Department of Environmental Engineering, University of Debrecen, Ótemető u. 2-4., Debrecen H-4028, Hungary; Doctoral School of Chemistry, University of Debrecen, Egyetem tér 1., Debrecen H-4032, Hungary
| | - Boglárka Kovács
- Debrecen Waterworks Ltd., Benczúr Gyula u. 7., Debrecen H-4032, Hungary
| | - Ildikó Bodnár
- Department of Environmental Engineering, University of Debrecen, Ótemető u. 2-4., Debrecen H-4028, Hungary
| | - István Fábián
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem tér 1., Debrecen H-4032, Hungary; ELKH-DE Mechanisms of Complex Homogeneous and Heterogeneous Chemical Reactions Research Group, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary.
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Siraki AG. The many roles of myeloperoxidase: From inflammation and immunity to biomarkers, drug metabolism and drug discovery. Redox Biol 2021; 46:102109. [PMID: 34455146 PMCID: PMC8403760 DOI: 10.1016/j.redox.2021.102109] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 08/12/2021] [Accepted: 08/16/2021] [Indexed: 12/11/2022] Open
Abstract
This review provides a practical guide to myeloperoxidase (MPO) and presents to the reader the diversity of its presence in biology. The review provides a historical background, from peroxidase activity to the discovery of MPO, to its role in disease and drug development. MPO is discussed in terms of its necessity, as specific individuals lack MPO expression. An underlying theme presented throughout brings up the question of the benefit and burden of MPO activity. Enzyme structure is discussed, including accurate masses and glycosylation sites. The catalytic cycle of MPO and its corresponding pathways are presented, with a discussion of the importance of the redox couples of the different states of MPO. Cell lines expressing MPO are discussed and practically summarized for the reader, and locations of MPO (primary and secondary) are provided. Useful methods of MPO detection are discussed, and how these can be used for studying disease processes are implied through the presentation of MPO as a biomarker. The presence of MPO in neutrophil extracellular traps is presented, and the activators of the former are provided. Lastly, the transition from drug metabolism to a target for drug development is where the review concludes.
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Affiliation(s)
- Arno G Siraki
- Faculty of Pharmacy & Pharmaceutical Sciences, University of Alberta, Edmonton, AB, Canada.
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Abdighahroudi MS, Schmidt TC, Lutze HV. Determination of free chlorine based on ion chromatography-application of glycine as a selective scavenger. Anal Bioanal Chem 2020; 412:7713-7722. [PMID: 32944811 PMCID: PMC7550385 DOI: 10.1007/s00216-020-02885-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 08/04/2020] [Accepted: 08/13/2020] [Indexed: 12/14/2022]
Abstract
Free available chlorine (FAC) is the most widely used chemical for disinfection and in secondary disinfection; a minimum chlorine residual must be present in the distribution system. FAC can also be formed as an impurity in ClO2 production as well as a secondary oxidant in the ClO2 application, which has to be monitored. In this study, a new method is developed based on the reaction of FAC with glycine in which the amine group selectively scavenges FAC and the N-chloroglycine formed can be measured by ion chromatography with conductivity detector (IC-CD). Utilizing IC for N-chloroglycine measurement allows this method to be incorporated into routine monitoring of drinking water anions. For improving the sensitivity, IC was coupled with post-column reaction and UV detection (IC-PCR-UV), which was based on iodide oxidation by N-chloroglycine resulting in triiodide. The method performance was quantified by comparison of the results with the N,N-diethyl-p-phenylenediamine (DPD) method due to the unavailability of an N-chloroglycine standard. The N-chloroglycine method showed limits of quantification (LOQ) of 24 μg L-1 Cl2 and 13 μg L-1 Cl2 for IC-CD and IC-PCR-UV, respectively. These values were lower than those of DPD achieved in this research and in ultrapure water. Measurement of FAC in the drinking water matrix showed comparable robustness and sensitivity with statistically equivalent concentration that translated to recoveries of 102% for IC-CD and 105% for IC-PCR-UV. Repeatability and reproducibility performance were enhanced in the order of DPD, IC-CD, and IC-PCR-UV. Measurement of intrinsic FAC in the ClO2 application revealed that the N-chloroglycine method performed considerably better in such a system where different oxidant species (ClO2, FAC, chlorite, etc.) were present.
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Affiliation(s)
- Mohammad Sajjad Abdighahroudi
- Faculty of Chemistry, Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstraße 5, 45141, Essen, Germany.,Department of Civil and Environmental Engineering, Institute IWAR, Chair of Environmental Analytics and Pollutants, Technical University of Darmstadt, Franziska-Braun-Straße 7, 64287, Darmstadt, Germany
| | - Torsten C Schmidt
- Faculty of Chemistry, Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstraße 5, 45141, Essen, Germany.,IWW Water Centre, Moritzstraße 26, 45476, Mülheim an der Ruhr, Germany.,Centre for Water and Environmental Research (ZWU), Universitätsstraße 5, 45141, Essen, Germany
| | - Holger V Lutze
- Faculty of Chemistry, Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstraße 5, 45141, Essen, Germany. .,Department of Civil and Environmental Engineering, Institute IWAR, Chair of Environmental Analytics and Pollutants, Technical University of Darmstadt, Franziska-Braun-Straße 7, 64287, Darmstadt, Germany. .,IWW Water Centre, Moritzstraße 26, 45476, Mülheim an der Ruhr, Germany. .,Centre for Water and Environmental Research (ZWU), Universitätsstraße 5, 45141, Essen, Germany.
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Simon F, Kiss E, Szabó M, Fábián I. The Chlorination of N-Methyl Amino Acids with Hypochlorous Acid: Kinetics and Mechanisms. Chem Res Toxicol 2020; 33:2189-2196. [PMID: 32633499 DOI: 10.1021/acs.chemrestox.0c00222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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.
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Affiliation(s)
- Fruzsina Simon
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary
| | - Eszter Kiss
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary
| | - Mária Szabó
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary
| | - István Fábián
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary.,MTA-DE Redox and Homogeneous Catalytic Reaction Mechanisms Research Group, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary
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Zhao H, Zhou Y, Han C, Liu YD, Zhong R. Degradation Mechanisms and Substituent Effects of N-Chloro-α-Amino Acids: A Computational Study. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:2635-2645. [PMID: 32033516 DOI: 10.1021/acs.est.9b04440] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
N-Chloro-α-amino acids formed in the chlorination disinfection treatment of water or wastewater and in living organisms have attracted extensive attention due to the potential toxicities of themselves and their decomposition products. The degradation mechanisms of three N-chloro-α-amino acids, i.e., N-chloro-glycine, N-chloro-alanine, and N-chloro-valine, have been systematically investigated using quantum chemical computations. The results indicate that N-chloro-α-amino acid anions undergo two competitive degradation pathways: a concerted Grob fragmentation (CGF) and β-elimination (β-E). Generally, the former predominates over the latter under neutral conditions and finally generates amines and carbonyls, while the latter is preferred under base-promoted conditions and mainly produces the respective α-keto acid anions or nitriles in the end. To gain deeper insights into the substitution effects, in view of the advantages of quantum chemical computations, a number of real or designed N-chloro-α-amino acids with traditional electron-donating groups (EDG) or electron-withdrawing groups (EWG) have been studied. All of the substituted N-chloro-α-amino acids, regardless of the type and position of substituents, are kinetically more favorable than N-monochloro-glycine for degradation via the CGF pathway. Moreover, conjugated EDG substituted on the N-terminal facilitate both CGF and β-E reactions, whereas conjugated EDG and EWG on the α-carbon are only favorable for the CGF and β-E reactions, respectively. These results are expected to expand our understanding of organic N-chloramine degradation mechanisms and chlorination reaction characteristics.
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Affiliation(s)
- Huiyuan Zhao
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
| | - Yingying Zhou
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
| | - Chunxiu Han
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
| | - Yong Dong Liu
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
| | - Rugang Zhong
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
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Szabó M, Bíró V, Simon F, Fábián I. The decomposition of N-chloro amino acids of essential branched-chain amino acids: Kinetics and mechanism. JOURNAL OF HAZARDOUS MATERIALS 2020; 382:120988. [PMID: 31484104 DOI: 10.1016/j.jhazmat.2019.120988] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 07/26/2019] [Accepted: 08/07/2019] [Indexed: 06/10/2023]
Abstract
The formation of N-chloro-amino acids is of outmost importance in water treatment technologies and also in vivo processes. These compounds are considered as secondary disinfectants and play important role in the defense mechanism against invading pathogens in biological systems. Adversary effects, such as apoptosis or necrosis are also associated with these compounds and the intermediates and final products formed during their decomposition. In the present study, the decomposition kinetics of the N-chloro derivatives of branched chain amino acids (BCAAs) - leucine, isoleucine, valine - were studied. On the basis of spectrophotometric measurements, it was confirmed that the decomposition proceeds via a spontaneous and an OH- assisted path in each case: kobs = k + kOH[OH-]. 1H, 13C NMR and MS experiments were also performed to identify the products and to monitor the progress of the reactions. It was established that the pH independent and the [OH-] dependent paths lead to the formation of the same aldehyde in each system (isovaleraldehyde, 2-methyl-butyraldehyde, and isobutyraldehyde) as a primary product. Under alkaline conditions, a portion of the aldehydes are converted into the corresponding Schiff-bases by the excess amino acid in a reversible process. A common mechanism was proposed for these reactions which postulates the formation of imines and hemiaminals as reactive intermediates.
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Affiliation(s)
- Mária Szabó
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary
| | - Vivien Bíró
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary
| | - Fruzsina Simon
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary
| | - István Fábián
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary; MTA-DE Redox and Homogeneous Catalytic Reaction Mechanisms Research Group, University of Debrecen, Debrecen, Hungary.
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Szabó M, Simon F, Fábián I. The formation of N-chloramines with proteinogenic amino acids. WATER RESEARCH 2019; 165:114994. [PMID: 31445310 DOI: 10.1016/j.watres.2019.114994] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 08/12/2019] [Accepted: 08/15/2019] [Indexed: 06/10/2023]
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.
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Affiliation(s)
- Mária Szabó
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary
| | - Fruzsina Simon
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary
| | - István Fábián
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary; MTA-DE Redox and Homogeneous Catalytic Reaction Mechanisms Research Group, University of Debrecen, Debrecen, Hungary.
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11
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Simon F, Szabó M, Fábián I. pH controlled byproduct formation in aqueous decomposition of N-chloro-α-alanine. JOURNAL OF HAZARDOUS MATERIALS 2019; 362:286-293. [PMID: 30243251 DOI: 10.1016/j.jhazmat.2018.09.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 08/09/2018] [Accepted: 09/02/2018] [Indexed: 06/08/2023]
Abstract
N-chloro-amino acids are readily formed in chlorination water treatment technologies. These reactions are also important in biological systems where HOCl plays an important role in the defense mechanism against invading pathogens. The intermediates and the products formed are of primary concern because they may have significant biological activities. In order to clarify intimate details and resolve discrepancies in the literature, the decomposition kinetics of N-chloro-α-alanine (MCA) was studied in the neutral - alkaline pH range by UV-vis spectrophotometry and 1H-NMR method. In contrast to earlier reports, the decomposition reaction proceeds via two distinct reaction paths: kobs1 = kOH[OH-] + k, where kOH = (1.38 ± 0.02) × 10-2 M-1s-1 and k = (2.95 ± 0.09) × 10-4 s-1. In slightly alkaline solution, the sole product is acetaldehyde. Under alkaline conditions, the main product is pyruvate ion, however, N-acetyl-α-alanine is also formed in a subsequent reaction sequence. A detailed kinetic model is postulated which involves the rate determining dissociation of MCA into Cl- and ethanimine which produces acetaldehyde in further reaction steps. Via the OH- assisted path, first a carbanion is formed which undergoes dechlorination and produces iminopropionate ion. This species is transformed into pyruvate ion through hydration and deamination steps.
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Affiliation(s)
- Fruzsina Simon
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary
| | - Mária Szabó
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary.
| | - István Fábián
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Debrecen, Hungary; MTA-DE Redox and Homogeneous Catalytic Reaction Mechanisms Research Group, University of Debrecen, Debrecen, Hungary
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12
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Kalmár J, Szabó M, Simic N, Fábián I. Kinetics and mechanism of the chromium(vi) catalyzed decomposition of hypochlorous acid at elevated temperature and high ionic strength. Dalton Trans 2018; 47:3831-3840. [DOI: 10.1039/c8dt00120k] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The decomposition of hypochlorous acid was studied under industrially relevant conditions (6.0 M NaClO3, 80 °C). Chromium(vi) catalyzes the decomposition and the catalytically active form is CrO42−. A detailed kinetic model is proposed for the process.
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Affiliation(s)
- József Kalmár
- Department of Inorganic and Analytical Chemistry
- University of Debrecen
- H-4032 Debrecen
- Hungary
| | - Mária Szabó
- Department of Inorganic and Analytical Chemistry
- University of Debrecen
- H-4032 Debrecen
- Hungary
| | - Nina Simic
- AkzoNobel Pulp and Performance Chemicals AB
- SE 44580 Bohus
- Sweden
| | - István Fábián
- Department of Inorganic and Analytical Chemistry
- University of Debrecen
- H-4032 Debrecen
- Hungary
- MTA-DE Redox and Homogeneous Catalytic Reaction Mechanisms Research Group
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13
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Šakić D, Hanževački M, Smith DM, Vrček V. A computational study of the chlorination and hydroxylation of amines by hypochlorous acid. Org Biomol Chem 2015; 13:11740-52. [PMID: 26486691 DOI: 10.1039/c5ob01823d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The reactions of hypochlorous acid (HOCl) with ammonia, (di)methylamine, and heterocyclic amines have been studied computationally using double-hybrid DFT methods (B2PLYP-D and BK-PLYP) and a G3B3 composite scheme. In the gas phase the calculated energy barriers for N- and/or C-hydroxylation are ca. 100 kJ mol(-1) lower than the barrier for N-chlorination of amines. In the model solvent, however, the latter process becomes kinetically more favored. The explicit solvent effects are crucial for determination of the reaction mechanism. The N-chlorination is extremely susceptible to the presence of explicit water molecules, while no beneficial solvation effect has been found for the N- or C-hydroxylation of amines. The origin of the observed solvent effects arises from differential solvation of the respective transition states for chlorine- and oxygen-transfers, respectively. The nature of solvation of the transition state structures has been explored in more detail by classical molecular dynamics (MD) simulation. In agreement with the quantum mechanical approach, the most stable structural motif, which includes the amine, HOCl, and two reactive waters, has been identified during the MD simulation. The inclusion of 5 or 6 explicit water molecules is required to reproduce the experimental barriers for HOCl-induced formation of N-chloramines in an aqueous environment.
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Affiliation(s)
- Davor Šakić
- Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10000 Zagreb, Croatia.
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14
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Bogdándi V, Lente G, Fábián I. Kinetics of the oxidation of isoniazid with the hypochlorite ion. RSC Adv 2015. [DOI: 10.1039/c5ra13540k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Isoniazid is oxidized within 1–10 seconds by the hypochlorite ion in a process that is first order with respect to both reactants and shows somewhat complicated stoichiometry.
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Affiliation(s)
- Virág Bogdándi
- Department of Inorganic and Analytical Chemistry
- University of Debrecen
- Debrecen
- Hungary
| | - Gábor Lente
- Department of Inorganic and Analytical Chemistry
- University of Debrecen
- Debrecen
- Hungary
| | - István Fábián
- Department of Inorganic and Analytical Chemistry
- University of Debrecen
- Debrecen
- Hungary
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