Kinetics of the Acid-Catalyzed Hydration of Allene and Propyne

Article abstract of DOI:10.1021/jo00326a016

The kinetics of the conversion of allene and propyne to acetone in aqueous sulfuric acid have been measured.The solvent isotope effects k_H+/k_D+ and the dependence of the rates on acidity are consistent with the Ad_E2 mechanism of rate-limiting protonation at the terminal carbons leading to the intermediate 2-propenyl cation CH3C⁺H=CH2 in each case, followed by hydration to the enol and isomerization to acetone.This route is strongly favored by published theoretical studies.