Solvation differences in the hydrolysis of certain alicyclic bromides

A detailed study of the hydrolysis in water of the cis and trans cyclopentyl and cyclohexyl bromohydrins reveals significant differences in the apparent heat capacity of activation (ΔCp≠). The cis isomers have values of[Formula: see text]; the same value as found for cyclopentyl bromide, but more negative by 10 caldeg−1 mole−1 than that found for the hydrolysis of cyclohexyl bromide. By contrast, the corresponding value for trans isomers was about −45 cal deg−1 mole−1. The differences in ΔCP≠ can be explained in terms of different mechanisms. Secondary β-deuterium isotope effects of 2.28 for the cis-2-bromocyclopentanol-1-d and 2.45 for cis-2-bromocyclohexanol-1-d confirm hydrogen participation in these cases. The corresponding ketones were the only products detected.