Kinetic Study on Chalcones and Schiff Base Proton Transfer Reactions

摘要

The rate of kinetics reaction of Schiff bases [N-(4-nitrobenzylidene-l-phenyl methanamine)] [N-(4-bromobenzylidene-l-phenyl methanamine)] and their derivatives with chalcone (2-benzylidine-l-tetralone) are investigated in this work. These compounds were prepared via Claisen-Schmidt condensation of drug ketones and the appropriate benzaldehyde derivative to form spiropyrrolidine. The kinetics was studied using spectrophotometer in dichloroethane as a solvent. The study was carried out in liquid phase using several techniques to follow the rates of the mechanistic; first step, the formation of the intermediate was followed by spectroscopic analysis. This study indicated a pseudo first order dependence with reaction rates of furan ring >H >p-NO2 at any temperature range from 293 to 333 K. The second step involves measurement the rate of its cyclization to form the product. The reaction kinetics was monitored using spectrophotometer indicating a first order dependence with sequence of p-NO2>H >furan ring. A suitable mechanism for this type of reaction was proposed. The kinetic study provides information about the formation of the intermediate and cyclic process. Moreover, the calculated activation parameters and entropies of activation are used to support the proposed mechanism.