Pub Date : 2005-01-01DOI: 10.1515/IRM.2005.5.3.173
S. K. Bera, Swapan K. Chandra, G. S. De
{"title":"Kinetic and Mechanistic Study of the Interaction Between cis-[Pt(N-N)(H2O)2](ClO4)2 (N-N = ethylenediamine or N,N′-dimethylethylenediamine) and L-glutamic Acid in Aqueous Medium","authors":"S. K. Bera, Swapan K. Chandra, G. S. De","doi":"10.1515/IRM.2005.5.3.173","DOIUrl":"https://doi.org/10.1515/IRM.2005.5.3.173","url":null,"abstract":"","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":"2 1","pages":"173 - 180"},"PeriodicalIF":0.0,"publicationDate":"2005-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78778152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-01-01DOI: 10.1515/IRM.2005.5.3.197
Dwight C. Ramdon, D. Dixon, T. Dasgupta
Thioglycolic Acid, H2TGA, containing a reactive sulphydryl group, has been shown to reduce Cr(VI). The experimental conditions were [Cr(VI)]T = 0.20 mM, [TGA]T = 22 – 100 mM, 15.0 ≤ T ≤ 30.0 °C, 2.66 ≤ pH ≤ 4.66 (TGA self-buffer) or 2.74 ≤ pH ≤ 6.05 (citric acid-phosphate) at a constant ionic strength of 0.50 M (NaClO4). The reaction was studied using rapid scanning stopped-flow spectrophotometry at λ = 425 nm. The kinetics of the reaction showed distinct spectral evidence for the formation of an intermediate that was subsequently followed by a slower, bimolecular redox process leading to the formation of the final products. Based on the analysis of the experimental data, the formation of the intermediate involved the conversion of an O-bonded Cr(VI)-thioglycolate intermediate, O3CrOC(O)CH2SH, to the Sbonded type O3CrSCH2COOH, prior to the redox step. Normal acid-base equilibria of thioglycolate ( H2TGA / HTGA) and chromate species ( HCrO4 / CrO4 2) were found to be inadequate to explain the overall mechanism. Instead, the facile reactions of both O-bonded and S-bonded Cr(VI)-thioglycolate intermediates were seen to be influenced by their own proton dependency. It was found that depending on the nature of the buffer used, some catalytic effects were evident, but the complete pH profile obtained was inherently peculiar to the reaction involving the main reactants. Added metal ions such as Cu2+ and Zn2+ are implicated in the overall course of the reaction, and their effects also seem to be determined by the concentration of [H +] utilized.
{"title":"Mechanistic Studies of the Reaction between Thioglycolic Acid and Chromium(VI): Substitution, Isomerisation, and Electron Transfer","authors":"Dwight C. Ramdon, D. Dixon, T. Dasgupta","doi":"10.1515/IRM.2005.5.3.197","DOIUrl":"https://doi.org/10.1515/IRM.2005.5.3.197","url":null,"abstract":"Thioglycolic Acid, H2TGA, containing a reactive sulphydryl group, has been shown to reduce Cr(VI). The experimental conditions were [Cr(VI)]T = 0.20 mM, [TGA]T = 22 – 100 mM, 15.0 ≤ T ≤ 30.0 °C, 2.66 ≤ pH ≤ 4.66 (TGA self-buffer) or 2.74 ≤ pH ≤ 6.05 (citric acid-phosphate) at a constant ionic strength of 0.50 M (NaClO4). The reaction was studied using rapid scanning stopped-flow spectrophotometry at λ = 425 nm. The kinetics of the reaction showed distinct spectral evidence for the formation of an intermediate that was subsequently followed by a slower, bimolecular redox process leading to the formation of the final products. Based on the analysis of the experimental data, the formation of the intermediate involved the conversion of an O-bonded Cr(VI)-thioglycolate intermediate, O3CrOC(O)CH2SH, to the Sbonded type O3CrSCH2COOH, prior to the redox step. Normal acid-base equilibria of thioglycolate ( H2TGA / HTGA) and chromate species ( HCrO4 / CrO4 2) were found to be inadequate to explain the overall mechanism. Instead, the facile reactions of both O-bonded and S-bonded Cr(VI)-thioglycolate intermediates were seen to be influenced by their own proton dependency. It was found that depending on the nature of the buffer used, some catalytic effects were evident, but the complete pH profile obtained was inherently peculiar to the reaction involving the main reactants. Added metal ions such as Cu2+ and Zn2+ are implicated in the overall course of the reaction, and their effects also seem to be determined by the concentration of [H +] utilized.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":"150 1","pages":"197 - 211"},"PeriodicalIF":0.0,"publicationDate":"2005-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75774042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-01-01DOI: 10.1515/IRM.2005.5.4.305
J. F. Read, S. Bewick
The kinetics and mechanism of the reaction between a series of inorganic oxysulfur compounds and potassium ferrate have been studied. Although a clear pattern has been developed, there are certain anomalous results, often pH dependent, which could be occurring because of hydrolysis or impurities. This paper addresses this problem by examining four theoretical models applied to some of the kinetic results obtained for trithionate, tetrathionate and pentathionate ions. The models examined are:
{"title":"The Kinetics and Mechanism of the Oxidation of Inorganic Oxysulfur Compounds by Potassium Ferrate Part IV - A Theoretical Analysis of Four Models Proposed to Explain Some of the Unusual Results for Trithionate, Tetrathionate and Pentathionate Ions","authors":"J. F. Read, S. Bewick","doi":"10.1515/IRM.2005.5.4.305","DOIUrl":"https://doi.org/10.1515/IRM.2005.5.4.305","url":null,"abstract":"The kinetics and mechanism of the reaction between a series of inorganic oxysulfur compounds and potassium ferrate have been studied. Although a clear pattern has been developed, there are certain anomalous results, often pH dependent, which could be occurring because of hydrolysis or impurities. This paper addresses this problem by examining four theoretical models applied to some of the kinetic results obtained for trithionate, tetrathionate and pentathionate ions. The models examined are:","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":"180 1","pages":"305 - 330"},"PeriodicalIF":0.0,"publicationDate":"2005-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77620590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-01-01DOI: 10.1515/IRM.2005.5.3.167
G. Huo, Xuguang Zhao, Bao-Sheng Liu
Heteropolyacids and their salts are known as acidic and redox catalysts in some reactions [1-3]. Studies of the kinetics and mechanism of redox reactions of heteropolyacids and their salts are instructive, given their value as redox reaction catalysts. Ammonium enneamolybdonickelate(IV) {(NH4)6[NiMo9O32]6H2O} is a Waugh-type heteropolyacid salt. It can oxidize a range of substances, including organic and inorganic reagents [4]. However, very few reports on the kinetics and mechanism of this type of heteropolyacid salts as oxidant have appeared. This paper reports the kinetics and mechanism of the reduction of enneamolybdonickelate(IV) by oxalate.
{"title":"Kinetics and Mechanism of the Reduction of Enneamolybdonickelate(IV) by Oxalate","authors":"G. Huo, Xuguang Zhao, Bao-Sheng Liu","doi":"10.1515/IRM.2005.5.3.167","DOIUrl":"https://doi.org/10.1515/IRM.2005.5.3.167","url":null,"abstract":"Heteropolyacids and their salts are known as acidic and redox catalysts in some reactions [1-3]. Studies of the kinetics and mechanism of redox reactions of heteropolyacids and their salts are instructive, given their value as redox reaction catalysts. Ammonium enneamolybdonickelate(IV) {(NH4)6[NiMo9O32]6H2O} is a Waugh-type heteropolyacid salt. It can oxidize a range of substances, including organic and inorganic reagents [4]. However, very few reports on the kinetics and mechanism of this type of heteropolyacid salts as oxidant have appeared. This paper reports the kinetics and mechanism of the reduction of enneamolybdonickelate(IV) by oxalate.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":"27 1","pages":"167 - 172"},"PeriodicalIF":0.0,"publicationDate":"2005-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82635436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ruthenium(III)-catalysed arsenic(III) oxidation by 12-tungstocobaltate(III) was found to proceed with transfer of an electron from catalyst to oxidant generating an intermediate ruthenium(IV). In the next step ruthenium(IV) abstract an electron from arsenic(III) leading to form arsenic(IV), which further reacts with oxidant to give arsenic(V). The active catalyst species was RuCl5(H2O) and due to formation of the inactive higher chloro-complex, RuCl6, inhibition of the reaction occurs as chloride ion concentration increases. There was no effect of hydrogen ion concentration on the reaction due to absence of any protonation equilibria under experimental conditions. The reaction was also catalysed by alkali metal cations due to ion pair formation between 12-tungstocobaltate(III) and alkali metal cations.
{"title":"Oxidation of Arsenous Acid by 12-Tungstocobaltate(III) Catalysed by Ruthenium(III) in Aqueous Acid Medium","authors":"B. D. Bhosale, G. Gokavi","doi":"10.1515/IRM.2004.5.2.79","DOIUrl":"https://doi.org/10.1515/IRM.2004.5.2.79","url":null,"abstract":"Ruthenium(III)-catalysed arsenic(III) oxidation by 12-tungstocobaltate(III) was found to proceed with transfer of an electron from catalyst to oxidant generating an intermediate ruthenium(IV). In the next step ruthenium(IV) abstract an electron from arsenic(III) leading to form arsenic(IV), which further reacts with oxidant to give arsenic(V). The active catalyst species was RuCl5(H2O) and due to formation of the inactive higher chloro-complex, RuCl6, inhibition of the reaction occurs as chloride ion concentration increases. There was no effect of hydrogen ion concentration on the reaction due to absence of any protonation equilibria under experimental conditions. The reaction was also catalysed by alkali metal cations due to ion pair formation between 12-tungstocobaltate(III) and alkali metal cations.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":"172 1","pages":"79 - 85"},"PeriodicalIF":0.0,"publicationDate":"2004-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86965562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2004-01-01DOI: 10.1515/IRM.2004.5.2.135
J. F. Read, B. Griffiths, L. Lynch, K. Maccormick, Nga Chiu Tam
The kinetics and mechanism of the oxidation of phenylthioacetic acid and thiodiglycolic acid by potassium ferrate were investigated under pseudo and non pseudo first-order conditions. Phenylthioacetic acid was oxidized to the sulfone and Fe(II) within 300s and thiodiglycolic acid was oxidized to the sulfoxide and Fe(III) within 1000s. Above a pH value of 8.7 for phenylthioacetic acid and 8.3 for thiodiglycolic acid the kinetics were firstorder in the concentration of the hydrogen ions, the organosulfur compound and the ferrate ions, whereas below these pH values the kinetics were independent of the hydrogen ion concentration. A possible mechanism involves reaction between protonated ferrate and the organosulfur compound as the rate-determining step with a rate constant of 35 M-1s-1. These results are comparable with other similar compounds.
{"title":"The Kinetics and Mechanism of the Oxidation of Phenylthioacetic Acid and Thiodiglycolic Acid by Potassium Ferrate","authors":"J. F. Read, B. Griffiths, L. Lynch, K. Maccormick, Nga Chiu Tam","doi":"10.1515/IRM.2004.5.2.135","DOIUrl":"https://doi.org/10.1515/IRM.2004.5.2.135","url":null,"abstract":"The kinetics and mechanism of the oxidation of phenylthioacetic acid and thiodiglycolic acid by potassium ferrate were investigated under pseudo and non pseudo first-order conditions. Phenylthioacetic acid was oxidized to the sulfone and Fe(II) within 300s and thiodiglycolic acid was oxidized to the sulfoxide and Fe(III) within 1000s. Above a pH value of 8.7 for phenylthioacetic acid and 8.3 for thiodiglycolic acid the kinetics were firstorder in the concentration of the hydrogen ions, the organosulfur compound and the ferrate ions, whereas below these pH values the kinetics were independent of the hydrogen ion concentration. A possible mechanism involves reaction between protonated ferrate and the organosulfur compound as the rate-determining step with a rate constant of 35 M-1s-1. These results are comparable with other similar compounds.","PeriodicalId":8996,"journal":{"name":"BioInorganic Reaction Mechanisms","volume":"30 2 1","pages":"135 - 150"},"PeriodicalIF":0.0,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90206152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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