Kinetics of the addition of hydroxide ions to substituted benzaldehydes

Abstract

Rates and equilibria have been investigated for the addition of hydroxide ions to ten substituted benzaldehydes in aqueous solution at 25 °C. Enthalpies of reaction are also reported, and the extent of hydration of five of the aidehydes. The rates of addition of hydroxide ions are almost proportional to the corresponding equilibrium constants; the rate of dissociation of the adduct is almost unaffected by substitution. It is concluded that the state of the carbon–oxygen bonds in the transition state corresponds closely to that in the adduct, but that the state of solvation of the transition state resembles that of the initial reactants.