Catalyse par les acides de Lewis—I : Etude cinetique de la reaction d'esterification des olefines catalysee par SnCl 4

Abstract

Lewis acids, such as SnCl 4, TiCl 4, FeCl 3 AlCl 3 and ZnCl 2 catalyze the esterification of olefins in CH 3CO 2H or CH 3CH 2CO 2H. SnCl 4 reacts with carboxylic acids to give the acid complex SnCl 4.2(RCO 2H), which raises the level of acidity. The following relation applies: log k ex = αH o + β (α≠−1), activation energy (7·5 kcal/mole) and activation entropy (−28 cal/M°K). Solvent isotope effects are measured (k H/k D>1). The mechanism implies a slow proton transfer.