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

IF 1.7 4区 化学 Q4 CHEMISTRY, PHYSICAL
Jannie C. Swarts, C. Robert Dennis
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引用次数: 0

摘要

在接近化学计量的条件下,研究了八氰钨酸盐(IV)离子在酸性介质中还原二溴二氰酸盐(III)离子的反应。在反应过程中发生了顺序变化。在前半衰期,Au(CN)2(Br)2 -为一级反应,W(CN)84 -为二级反应,但在转化率约60%后,两种反应物均为一级反应。顺序变化归因于在反应过程中形成的两种不同的AuII中间体。在[H+] = 1.633 × 10-3 M、离子强度I = 0.11 M (NaBr)和25.0±0.1℃条件下,反应的三级速率常数k3 = 7.80 × 105 M−2 min−1,二级速率常数k2 = 108 M−1 min−1。在低pH条件下,反应速率随[H+]的增加而降低,在25.0±0.1°C条件下,HW(CN)83 -去质子化的实验pKa为1.80±0.03。反应速率与[Br−]无关,随W(CN)83 -的加入而降低。活化参数由温度数据直接与Eyring方程进行最小二乘拟合得到。图形抽象
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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.

Graphical abstract

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来源期刊
CiteScore
3.30
自引率
5.60%
发文量
201
审稿时长
2.8 months
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.
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