Novel kinetics model for third-liquid phase-transfer catalysis system of the "complex" carbanion: Competitive role between catalytic cycles

Kinetic model for Homer-Wadsworth-Emerson (HWE) reaction of the "complex" carbanion in the third-liquid phase-transfer catalysis (TLPTC) system was proposed and the factors that influenced the model parameters were investigated in details. The generation process and the composition of the third phase revealed that there were two catalytic cycles (the third phase reaction and the organic phase reaction) in this TLPTC system. Kinetic model which consisted of ion-exchange reaction rate constant, bond-forming reaction rate constant and the contribution ratio between each two catalytic cycle was deduced. Distribution of the carbanion ion-pair between the third phase and the organic phase caused the competitive relationship between these two catalytic cycles. Third phase was the preferred region for the bond-forming reaction, and which contribution was always 5-6 times higher than that of the organic phase reaction. Reaction rate of each catalytic cycle was also affected by lipophilicity of the anion in this TLPTC system. The steric hindrance, lipophilicity of the catalyst cation and polarity of the third phase were primary factors influencing catalyst activity. (C) 2015 Elsevier B.V. All rights reserved.