The effect of pressure on the [2 + 2 → 4] cycloaddition of diphenylketen to enol ethers

Abstract

The volume profiles for the [2 + 2] cycloaddition reactions between diphenylketen and butyl vinyl ether, 2-methoxypropene, and 2,3-dihydro-4H-pyran, respectively, have been determined. For the first example a wide range of solvents was studied. The Kirkwood theory seems to be not fully adequate for the description of the solvent effects found for the rate constant and especially for the partial molar volumes. Solvent cohesive energy densities offer an alternative description. In most solvents the volumes of reaction and the volumes of activation are similar in magnitude and support a concerted mechanism for the cycloaddition.