ALKYNE HYDRATION PROMOTED BY RHCL3 AND QUATERNARY AMMONIUM-SALTS

lon pairs generated from RhCl3 and quaternary ammonium salts were shown to promote the addition of water to carbon-carbon triple bonds. Terminal alkynes were found to form exclusively ketones. The reaction proved to take place in wet THF, as well as under phase transfer conditions. Under the latter conditions the rhodium catalyst could be recovered as NaRhCl4 in the aqueous phase by addition of aqueous NaClO4. Kinetic studies with 1-octyne and phenylacetylene revealed that the rate of hydration depends on the concentrations of the alkyne, water, rhodium and quaternary ammonium salt. The observed activation energy values of 14.2 and 12.8 kcal mol-1 for the hydration of 1-octyne and phenylacetylene, respectively, indicate that these reactions are both chemically and diffusion controlled.