{"title":"八氰钨酸盐(IV)在酸性介质中还原反式二氰二溴酸盐(III)的动力学研究中反应过程中顺序变化的观察","authors":"Jannie C. Swarts, C. Robert Dennis","doi":"10.1007/s11144-024-02743-6","DOIUrl":null,"url":null,"abstract":"<div><p>The reduction of dibromodicyanoaurate(III) ion by octacyanotungstate(IV) ions was studied under near stoichiometric conditions in an acidic medium. An order change occurred during the course of the reaction. The reaction was first order in Au(CN)<sub>2</sub>(Br)<sub>2</sub><sup>–</sup> and second order in W(CN)<sub>8</sub><sup>4–</sup> for the first half-life, but after ca. 60% conversion became first order in both reactants. The order change is ascribed to two different Au<sup>II</sup> intermediates that form during the reaction course. A third order rate constant of k<sub>3</sub> = 7.80 × 10<sup>5</sup> M<sup>−2</sup> min<sup>−1</sup> and a second order rate constant of k<sub>2</sub> = 108 M<sup>−1</sup> min<sup>−1</sup> was found at [H<sup>+</sup>] = 1.633 × 10<sup>–3</sup> M, an ionic strength of I = 0.11 M (NaBr) and at 25.0 ± 0.1 °C for the reaction. The reaction rate decreases with increasing [H<sup>+</sup>] in the reaction mixture at low pH and an experimental pK<sub>a</sub> of 1.80 ± 0.03 was found at 25.0 ± 0.1 °C for the deprotonation of HW(CN)<sub>8</sub><sup>3–</sup>. The reaction rate is independent of [Br<sup>−</sup>] and decrease with addition of W(CN)<sub>8</sub><sup>3–</sup> in the reaction mixture. Activation parameters have been obtained by a least-squares fit of the temperature data directly to the Eyring equation.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":750,"journal":{"name":"Reaction Kinetics, Mechanisms and Catalysis","volume":"138 1","pages":"31 - 45"},"PeriodicalIF":1.7000,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11144-024-02743-6.pdf","citationCount":"0","resultStr":"{\"title\":\"Observation of an order change during the course of a reaction in a kinetic study of the reduction of trans-dicyanodibromoaurate(III) by octacyanotungstate(IV) in an acidic medium\",\"authors\":\"Jannie C. Swarts, C. Robert Dennis\",\"doi\":\"10.1007/s11144-024-02743-6\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>The reduction of dibromodicyanoaurate(III) ion by octacyanotungstate(IV) ions was studied under near stoichiometric conditions in an acidic medium. An order change occurred during the course of the reaction. The reaction was first order in Au(CN)<sub>2</sub>(Br)<sub>2</sub><sup>–</sup> and second order in W(CN)<sub>8</sub><sup>4–</sup> for the first half-life, but after ca. 60% conversion became first order in both reactants. The order change is ascribed to two different Au<sup>II</sup> intermediates that form during the reaction course. A third order rate constant of k<sub>3</sub> = 7.80 × 10<sup>5</sup> M<sup>−2</sup> min<sup>−1</sup> and a second order rate constant of k<sub>2</sub> = 108 M<sup>−1</sup> min<sup>−1</sup> was found at [H<sup>+</sup>] = 1.633 × 10<sup>–3</sup> M, an ionic strength of I = 0.11 M (NaBr) and at 25.0 ± 0.1 °C for the reaction. The reaction rate decreases with increasing [H<sup>+</sup>] in the reaction mixture at low pH and an experimental pK<sub>a</sub> of 1.80 ± 0.03 was found at 25.0 ± 0.1 °C for the deprotonation of HW(CN)<sub>8</sub><sup>3–</sup>. The reaction rate is independent of [Br<sup>−</sup>] and decrease with addition of W(CN)<sub>8</sub><sup>3–</sup> in the reaction mixture. Activation parameters have been obtained by a least-squares fit of the temperature data directly to the Eyring equation.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>\",\"PeriodicalId\":750,\"journal\":{\"name\":\"Reaction Kinetics, Mechanisms and Catalysis\",\"volume\":\"138 1\",\"pages\":\"31 - 45\"},\"PeriodicalIF\":1.7000,\"publicationDate\":\"2024-11-18\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://link.springer.com/content/pdf/10.1007/s11144-024-02743-6.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Reaction Kinetics, Mechanisms and Catalysis\",\"FirstCategoryId\":\"92\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s11144-024-02743-6\",\"RegionNum\":4,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"CHEMISTRY, PHYSICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Reaction Kinetics, Mechanisms and Catalysis","FirstCategoryId":"92","ListUrlMain":"https://link.springer.com/article/10.1007/s11144-024-02743-6","RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
Observation of an order change during the course of a reaction in a kinetic study of the reduction of trans-dicyanodibromoaurate(III) by octacyanotungstate(IV) in an acidic medium
The reduction of dibromodicyanoaurate(III) ion by octacyanotungstate(IV) ions was studied under near stoichiometric conditions in an acidic medium. An order change occurred during the course of the reaction. The reaction was first order in Au(CN)2(Br)2– and second order in W(CN)84– for the first half-life, but after ca. 60% conversion became first order in both reactants. The order change is ascribed to two different AuII intermediates that form during the reaction course. A third order rate constant of k3 = 7.80 × 105 M−2 min−1 and a second order rate constant of k2 = 108 M−1 min−1 was found at [H+] = 1.633 × 10–3 M, an ionic strength of I = 0.11 M (NaBr) and at 25.0 ± 0.1 °C for the reaction. The reaction rate decreases with increasing [H+] in the reaction mixture at low pH and an experimental pKa of 1.80 ± 0.03 was found at 25.0 ± 0.1 °C for the deprotonation of HW(CN)83–. The reaction rate is independent of [Br−] and decrease with addition of W(CN)83– in the reaction mixture. Activation parameters have been obtained by a least-squares fit of the temperature data directly to the Eyring equation.
期刊介绍:
Reaction Kinetics, Mechanisms and Catalysis is a medium for original contributions in the following fields:
-kinetics of homogeneous reactions in gas, liquid and solid phase;
-Homogeneous catalysis;
-Heterogeneous catalysis;
-Adsorption in heterogeneous catalysis;
-Transport processes related to reaction kinetics and catalysis;
-Preparation and study of catalysts;
-Reactors and apparatus.
Reaction Kinetics, Mechanisms and Catalysis was formerly published under the title Reaction Kinetics and Catalysis Letters.