Base-catalyzed hydrogen isotope exchange and the aqueous acidity of toluene

Measurements of hydrogen isotope exchange of toluene-α-d and -α-t in aqueous sodium hydroxide are reported for temperatures of 150–200°C. The reaction shows essentially no primary isotope effect. The rate extrapolated to 24°C is combined with the rate constant for reaction of benzyl anion with water obtained earlier by Bockrath and Dorfman⁸ to derive the aqueous pk_a, of toluene as 39.6 (per hydrogen basis).