Intramolecular catalysis. Part 3. The hydration and ionisation of o-phthalaldehyde

Abstract

o-Phthalaldehyde hydrates to form a bridged (cyclic) monohydrate. The hydrate exists as a cis-trans mixture, with the equilibrium constant for hydration, K_H, at 20 °C in water being 9.39. The pk_a value of o-phthalaldehyde hydrate at 20 °C in water is 12.08. The hydration and ionisation have been investigated at several temperatures, as has the rate of the uncatalysed hydration. A mechanism for the uncatalysed hydration is suggested.