The solvent deuterium isotope effect on the hydroxide-ion-catalyzed conversion of acetaldehyde to its enolate ion

Rates of proton transfer from acetaldehyde to the hydroxide ion were measured by iodine scavenging in H 2 O and in D 2 O solution at 25 °C; the results give the solvent isotope effect . This value is somewhat more consistent with an estimate, made using fractionation factor theory, for hydron transfer directly from the substrate to the hydroxide ion than with another estimate, made similarly, for hydron transfer through an intervening water molecule.