Ab Initio Calculations of Absolute pKa Values in Aqueous Solution II. Aliphatic Alcohols, Thiols, and Halogenated Carboxylic Acids

A thermodynamical cycle is proposed to calculate absolute p K a values for Brönsted acids in aqueous solution. The polarizable continuum model (PCM) was used to describe the solvent, and absolute p K a values were computed for different classes of organic compounds: aliphatic alcohols, thiols, and halogenated derivatives of carboxylic aliphatic acids. The model furnishes p K a values in good agreement with the experimental results for some classes of compounds. For the cases where appreciable deviations are observed, we have tried to establish a correlation among the neglected components of Δ G solv resulting from the model adopted, the level of calculation employed, and the p K a deviations relative to the experimental results.