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Using methods of chemical kinetics and quantum modeling, we investigated the mechanism by which base catalysts affect the regioselectivity of the ring opening of 2‐(chloromethyl)oxirane by benzoic acid. The model reaction was carried out using 2‐(chloromethyl)oxirane as both reagent and solvent at temperatures of 303‐333 K. Rate constants and activation parameters of the ring opening were determined for the overall reaction and for the formation of the isomeric “normal” and “abnormal” products. Density functional theory B3LYP/6‐31+G** was used to examine possible reaction pathways. A comparison of experimental measurements and theoretical calculations confirm that the rate‐limiting step is the attack of the benzoate anion on the C1 and C2 positions of 2‐(chloromethyl)oxirane. The present results indicate that the regioselectivity of the 2‐(chloromethyl)oxirane ring opening by benzoic acid depends on the ratio of A2 mechanisms, SN2 and “borderline” SN2 type. This suggests that weak nucleophilic base catalysts can increase the reaction regiospecificity by increasing the contribution of the SN2 pathway.

A model was constructed for the mechanism of the reaction of aliphatic and aromatic carboxylic acids with epichlorohydrin catalyzed by tertiary amines. A mechanism for the catalysis of the transfer of the anion of the nucleophilic reagent by an ion pair was proposed taking account of the kinetic data and selected chemical and mathematical models.The reaction of oxiranes with nucleophilic reagents is the basis for obtaining epoxide polymer materials [1-3], pharmaceutical agents [4], and the physiological detoxification of the products of the metabolism of exogenous substances [5]. The most convenient model for solving a series of practical aspects in the field of functional polymers, ecology, and biochemistry as well as for studying the mechanism of opening of the oxirane ring by the action of nucleophilic reagents is the reaction of 1-chloro-2,3-epoxypropane (epichlorohydrin (ECH)) with monocarboxylic acids in the presence of base catalysts:Despite the large number of studies on the practical application of reaction (1), the investigations of its kinetics and the mechanism of opening of the oxirane ring by nucleophilic reagents in the presence of a base have not been systematic and, in some cases, are considered questionable [6-9]. Two possible catalysis mechanisms have been discussed in the literature: A) base catalysis and B) nucleophilic catalysis. Mechanism A involves activation of the carboxylic acid by the catalyst with subsequent reaction with the oxirane substrate. Mechanism B involves activation of the substrate by the catalyst with subsequent reaction with the reagent. The realization of mechanism A requires proton transfer by the nucleophile to the base in the initial or transition states. In an aprotic solvent such as ECH, the base catalysis in the case of carboxylic acids with rather high pK a values is unlikely. In this regard, mechanism B is preferred but it accounts only for a first-order reaction and excludes a zero-order reaction.In the present work, we carried out a kinetic study of the mechanism of the catalytic acidolysis of ECH in reaction (1) and constructed a mathematical model. 1680040-5760/10/4603-0168

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