Halogens in γ-position enhance the acidity of alkyl aryl sulfones and alkane nitriles

On the basis of measuring the rates of base-catalyzed deuterium exchange the pKa values of a series of 3-halopropyl aryl sulfones and 4-halobutyronitriles were estimated. It was shown that halogen substituents, although separated from the carbanionic site, exert a substantial carbanion stabilizing effect. These effects were rationalized by DFT calculations.