Autoprotolysis in aqueous organic solvent mixtures. Water/alcohol binary systems

By use of a previously derived equation, the main factors that contribute to autoprotolysis are studied for different water/ alcohol mixtures. These factors are: autoionization of water, autoionization of the alcohol, and proton transfer from water to the alcohol or from the alcohol to water. The most important factors seem to be the proton transfer from the alcohol to water, and to a much lesser degree, the autoionization of water. The autoionization of the alcohol is only significant for pure alcohol. The different factors have been correlated with the solvent properties polarity and hydrogen-bond ability. An increase in these solvent properties favours autoionization and proton transfer, and therefore decreases the observed autoprotolysis pK value. The proposed equation and the parameters calculated allow an accurate estimation of the autoprotolysis pK value for any studied water/alcohol system.