Ab initio calculations of absolute pK(a) values in aqueous solution II. Aliphatic alcohols, thiols, and halogenated carboxylic acids

A thermodynamical cycle is proposed to calculate absolute pK(a) values for Bronsted acids in aqueous solution. The polarizable continuum model (PCM) w as used to describe the solvent, and absolute pK(a) values were computed fo r different classes of organic compounds: aliphatic alcohols, thiols, and h alogenated derivatives of carboxylic aliphatic acids. The model furnishes p K(a) values in good agreement with the experimental results for some classe s of compounds. For the cases where appreciable deviations are, observed, w e have tried to establish a correlation among the neglected components of D elta G(solv) resulting from the model adopted, the level of calculation emp loyed, and the pK(a) deviations relative to the experimental results.