Influence of substituents in the 3-position of cyclohexene oxides on the rates of their reactions with hydrogen chloride in low polarity aprotic solvents

Rates of reactions of cyclohexene oxide and of its cis- and trans-3-methyl and 3-t-butyl derivatives with HCl were measured in toluene and CCl4 by a calorimetric method. Although these rates are very sensitive to trace impurities, satisfactory second-order kinetics were obtained in the presence of small amounts of water or tetrahydrofuran. An equatorial substituent in the 3-position trans to the epoxide oxygen has a rate-retarding effect which is larger for t-butyl than for methyl. The qualitative agreement between the ratios of the rates of formation of the four trans-chlorohydrins from each cis–trans pair of the 3-alkylcyclohexene oxides and the molar ratios of the bromohydrins obtained in the reactions of the corresponding alkylcyclohexenes with NBS in DMSO–water supports the hypothesis that in the latter reaction the nucleophillic step, rather than the electrophilic one, is rate determining.