Triphase catalysis: a rigorous mechanistic model for nucleophilic substitution reactions based on a modified Langmuir-Hinshelwood/Eley-Rideal approach

Abstract

In the present work, a general kinetic model based on the traditional kinetic mechanisms of the Langmuir-Hinshelwood and Eley-Rideal types has been developed for nucleophilic substitution reaction systems involving a triphase catalyst in which the intrinsic reaction rate at the catalyst active site is the rate-limiting step. The present mechanistic model overcomes the limitation of the commonly used pseudo-first-order model by incorporating the effect of the leaving anion on the ion-exchange step, and can be used to determine whether a triphase catalytic system is limited by the organic reaction step, ion-exchange step, or a combination of both the steps. Reactions to synthesize octyl acetate by using different octyl halides as the organic reactant have been used to show how the parameters values obtained can be used to classify systems. These values showed physical relevance since the data were in high conformity with trends that could be expected from the physical and chemical properties of the halide anions and the corresponding alkyl halides.