重铬酸乙二铵在乙醇水溶液介质中乙醇酸和乳酸氧化的动力学和机理分析中的作用

IF 1.4 4区 化学 Q4 CHEMISTRY, PHYSICAL Journal of Solution Chemistry Pub Date : 2024-02-10 DOI:10.1007/s10953-023-01359-z
H. Jain, P. Kharetiya, D. Panday
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引用次数: 0

摘要

在乙酸水介质中,研究人员探讨了乙醇酸和乳酸被乙二胺重铬酸盐[enH2Cr2O7]氧化的动力学。氧化产物是相应的氧化酸。采用传统的紫外-可见分光光度法研究反应动力学。观察到[enH2Cr2O7]的一阶动力学,而底物的一阶动力学小于二阶。与底物的分数阶相关性证实了氧化剂和底物在决定速率的步骤之前结合形成复合物。反应速率随着[H+]浓度的增加而增加。在 298K 时,乙醇酸存在主要动力学同位素效应 kH/kD = 5.97(原乙醇酸和氘代乙醇酸的速率常数之比),这表明是 C-H 键裂解而不是 C-C 键裂解。溶剂极性的变化对氧化速率有显著影响。根据实验数据,提出了在分子内质子转移后形成不稳定的环状过渡态的观点。在类似条件下,对乳酸的氧化进行了研究。
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Role of Ethylenediammonium Dichromate in the Kinetic and Mechanistic Analysis of the Oxidation of Glycolic and Lactic Acids in Aqueous AcOH Medium

In aqueous acetic acid medium, the kinetics of oxidation of glycolic and lactic acid by ethylenediammonium dichromate [enH2Cr2O7] have been explored. The oxidation product is the corresponding oxoacid. The conventional UV–vis spectrophotometric method is used to study the reaction kinetics. First-order kinetics has been observed concerning [enH2Cr2O7] and with substrate the order is less than two. The fractional-order dependency with respect to substrate confirms the binding of oxidant and substrate to form a complex before rate-determining step. The rate of reaction increases with an increase in [H+] concentration. The existence of primary kinetic isotope effect, kH/kD = 5.97 at 298K for glycolic acid (ratio of rate constants for protio- and deuterio-glycolic acid) indicated a C–H bond cleavage rather than C–C bond cleavage. Variation of solvent polarity is found to impose a remarkable impact on the rate of oxidation. From the experimental data, formation of an unstable cyclic transition state followed by intra-molecular proton transfer has been proposed. Under similar conditions oxidation of lactic acid was studied.

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来源期刊
Journal of Solution Chemistry
Journal of Solution Chemistry 化学-物理化学
CiteScore
2.30
自引率
0.00%
发文量
87
审稿时长
3-8 weeks
期刊介绍: Journal of Solution Chemistry offers a forum for research on the physical chemistry of liquid solutions in such fields as physical chemistry, chemical physics, molecular biology, statistical mechanics, biochemistry, and biophysics. The emphasis is on papers in which the solvent plays a dominant rather than incidental role. Featured topics include experimental investigations of the dielectric, spectroscopic, thermodynamic, transport, or relaxation properties of both electrolytes and nonelectrolytes in liquid solutions.
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