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The hydrolysis of α-benzoxystyrene(1) in strong acidic solution has been investigated kinetically. In perchloric acid concentration lower than 5.5 M(Ho < -3.0), hydration paramer ω = + 7.6, and Φ = + 0.54 were obtained. The solvent isotope effect kH2O/KD2O is 0.72. The substituent effect was found to conform to the Hammett σ+ constant with ρ = -0.60. On the basis of these results and other evidence, the hydrolysis of the enol ester proceeds by AAL2 type mechanism. In concentration greater than 5.5 M(Ho > -3.0), isotope effect, kH2O/D2O is 3.32, substituent effect, ρ is -1.60 and the rate is linear with the acidity function, Ho. Thus, the mechanism changes one involving initial, and rate-determining olefin protonation.
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