Observation of an unusually large rate acceleration caused by a homoallylic double bond in the solvolyses of an unstrained secondary adamantyl tosylate

Abstract

The solvolysis of 2-adamantylideneadamantyl tosylate 1c in aqueous solvent mixtures shows a sensitivity to the ionizing power of the solvent (m value) of 0.66 ± 0.01, 0.65 ± 0.01 and 0.66 ± 0.02 for mixtures of methanol, ethanol and acetone respectively. 1c reacts 4 × 10⁵ faster than 2-adamantyl tosylate in 80:20 v/v ethanol–water, this rate acceleration is caused by a reduction in the enthalpy of activation (ΔH^‡= 19.2 kcal mol^–1 for 1cvs. 26.9 kcal mol^–1 for 2-adamantyl tosylate).