2, 6-二甲氧基-2-嘧啶氧基-N-芳基苄胺衍生物的酸催化Smiles重排反应动力学

研究了酸催化下的2, 6-二甲氧基-2-嘧啶氧基-N-芳基苄胺衍生物Smiles重排反应的动力学,考察了盐酸的初始浓度、溶剂、反应温度和取代基对反应速率的影响。结果表明,盐酸的初始浓度增加,重排反应速率加快;在单一溶剂中反应速率的顺序为:甲醇>乙醇>二甲基亚砜>乙腈,而在甲醇/水(1:1, V/V)的混合溶剂中反应速率明显增加,其表观反应速率常数(k_obs)值是甲醇溶剂中的5.27倍;在25-45 ℃温度范围内,各衍生物的反应速率随着温度的升高而加快,其活化能(73.99-76.92 kJ·mol^-1)、活化焓(71.57-74.38 kJ·mol^-1)及Gibbs自由能(81.51-85.77 kJ·mol^-1)数值相近,仅活化熵(-24.38 --47.11 J·K^-1·mol^-1)有一定的差别;取代基常数和表观速率常数之间呈现一定的线性关系,环上吸电子基团的存在有利于反应速率的提高;实验验证了反应机理的合理性。

Kinetics of Acid-Catalyzed Smiles Rearrangement of 2,6-Dimethoxy-2-pyrimidinyloxy-N-arylbenzylamine Derivatives

The kinetics of the acid-catalyzed Smiles rearrangement reactions of 2, 6-dimethoxy-2-pyrimidinyloxy-N-arylbenzylamine derivatives was investigated. The effects of initial concentrations of hydrochloric acid, solvent, temperature, and substituent on reaction rates were examined. The results show that the rates increase with an increase in the initial concentration of hydrochloric acid. The reactivity order is CH₃OH > C₂H₅OH > CH₃SOCH₃ > CH₃CN in a single solvent, but rates markedly increase in mixed CH₃OH/H₂O (1:1, V/V) and the apparent reaction rate constant (k_obs) is 5.27 times that of methanol. The rates for the derivatives are found to increase with an increase in temperature at 25-45 ℃, and no significant differences in activation energy (73.99-76.92 kJ·mol^-1), activation enthalpy (71.57-74.38 kJ·mol^-1), and Gibbs free energy (81.51-85.77 kJ·mol^-1) are observed between them, except that there is difference in activation entropy (-24.38 --47.11 J·K^-1·mol^-1). There is a good linear relationship between substituents and the apparent reaction rate constants, and it is speculated that electron-withdrawing groups in the benzene ring will increase the reaction rates. A relevant reaction mechanism is suggested.