Effect of Medium on the Kinetics of Stereoselective Synthesis of a Highly Functionalized Cyclopropanesame

Abstract

The effect of different media on the kinetics and mechanism of formation of diethyl (1S, 2S)-3, 3-dibenzoylcyclopropane-1, 2-dicarboxylate was investigated. The reaction was accelerated with changing the medium from non-ionic to ionic. Among the selected ionic salts, NaCl was the best salt to increase the reaction rate of the titled synthesis about 2.5-fold (kobs = 1.295 M-1.min-1 against kobs = 3.105 M-1.min-1). The incremental effect of ionic salts was found to be in this order: NaCl > NaBr > KBr > KCl. Isokinetic plots for the reaction in the presence of different salts were obtained and a linear relationship which indicated an identical mechanism for all reactions, was found. Moreover, the effect of cationic, nonionic, and anionic surfactants on the reaction rate was evaluated. Substantial reduction on the reaction rate and change in the mechanism was observed with the addition of an anionic surfactant such as sodium dodecyl sulfate. The values of activation parameters were also estimated (ΔH‡ = 80.1 ± 0.6 kJ.mol-1, ΔS‡ = 23.9 ± 2.0 J.mol-1.K-1, and ΔG‡ = 72.9 ± 1.1 kJ.mol-1) and the positive value of ΔH‡ confirmed the endothermic process and entropy value referred to an associative mechanism.