Triphenylarsine as an effective catalyst in a mechanistic investigation of trans- 1, 2-di (methoxycarbonyl)-6, 6-dimethyl-5, 7-dioxaspiro [2, 5] octane-4, 8-dione formation

Phosphorus Sulfur and Silicon and The Related Elements Pub Date : 2017-03-03 DOI:10.1080/10426507.2017.1302448

F. Ghodsi, S. Habibi‐Khorassani, M. Shahraki

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引用次数: 7

Abstract

ABSTRACT The kinetics and mechanism of the reaction between dimethyl acetylendicarboxylate (DMAD) and Meldrum's acid (MA) in the presence of triphenylarsine (TPA) as a catalyst were investigated in a methanol environment by the UV/vis spectrophotometry technique. In this work, the reaction followed second- order kinetics and the first and second steps of the reaction mechanism were recognized as the fast and rate-determining step (RDS), respectively. A significant point in this reaction “in comparison with previous work” is related to the change in behavior of the kinetics and reaction mechanism in the presence of triphenylarsine (TPA). Activation energy and parameters (Ea, ΔH‡, ΔS‡, and ΔG‡) were determined for the reaction and a comparison between ΔH‡ and TΔS‡ values showed that the reaction is entropy-controlled. High values of the activation Gibbs free energy indicated that the reaction was chemically controlled. Also, the large negative value of ΔS‡ implied an associative mechanism. GRAPHICAL ABSTRACT

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三苯larsin在反式- 1,2 -二(甲氧羰基)- 6,6 -二甲基- 5,7 -二氧辛烷[2,5]- 4,8 -二酮生成机理研究中的有效催化剂

摘要以三苯larsine (TPA)为催化剂，采用紫外/可见分光光度法研究了甲醇环境下，乙酰二羧酸二甲酯(DMAD)与Meldrum's acid (MA)的反应动力学和反应机理。在本研究中，反应遵循二级动力学，反应机理的第一步和第二步分别被认为是快速和速度决定步骤(RDS)。该反应“与以前的工作相比”的一个重要点与三苯larsin (TPA)存在时动力学行为和反应机理的变化有关。测定了反应的活化能和参数(Ea、ΔH‡、ΔS‡和ΔG‡)，ΔH‡和TΔS‡值的比较表明反应是熵控的。活化吉布斯自由能的高值表明该反应是化学控制的。此外，ΔS‡的大负值暗示了一种关联机制。图形抽象

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Phosphorus Sulfur and Silicon and The Related Elements

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