Oxidation of Organic Sulfides by Imidazolium Fluorochromate: A Kinetic and Mechanistic Approach
作者:Lokesh Mathur、A. Choudhary、Om Prakash、Pradeep K. Sharma
DOI:10.14233/ajchem.2014.15753
日期:——
The oxidation of organic sulfides by imidazolium fluorochromate resulted in the formation of the corresponding sulfoxides. The reaction is first order with respect to imidazolium fluorochromate. A Michaelis-Menten type kinetics was observed with respect to the reactants. The reaction is catalyzed by toluene-p-sulfonic acid. The oxidation was studied in nineteen different organic solvents. An analysis of the solvent effect by Swains equation showed that the both cation- and anion-solvating powers of the solvents play important roles. The correlation analyses of the rate of oxidation of thirty four sulfides were performed in terms of various single and multiparametric equations. For the aryl methyl sulfides, the best correlation is obtained with Chartons LDR and LDRS equations. The oxidation of alkyl phenyl sulfides exhibited a good correlation in terms of Pavelich-Taft equation. The polar reaction constants are negative indicating an electron-deficient sulfur centre in the rate-determining step. A mechanism involving formation of a sulphenium cation intermediate in the slow step has been proposed.
有机硫化物在咪唑鎓氟铬酸盐的作用下被氧化,形成相应的亚砜。该反应对咪唑鎓氟铬酸盐呈一阶动力学。对反应物观察到米哈伊利斯-门腾型动力学。该反应由对甲苯磺酸催化。氧化反应在十九种不同有机溶剂中进行了研究。根据斯温方程对溶剂效应的分析表明,溶剂的阳离子和阴离子溶剂作用力均起着重要作用。对三十四种硫化物氧化速率的相关性分析采用了不同的单参数和多参数方程。对于芳基甲基硫化物,最佳相关性出现在查顿的LDR和LDRS方程中。烷基芳基硫化物的氧化在帕维利奇-塔夫特方程下表现出良好的相关性。极性反应常数为负,表明在速率决定步骤中存在电子缺乏的硫中心。提出了一种涉及在慢步骤中形成亚砜阳离子中间体的机制。