THE SOLVENT EFFECT ON THE ACIDITIES OF HALOACETIC ACIDS IN AQUEOUS-SOLUTION - A RISM-SCF STUDY

The acidities of acetic, fluoroacetic and chloroacetic acids in aqueou s solution are calculated by means of the ab initio method combined wi th the reference interaction site method in the statistical mechanics of molecular liquids (the RISM-SCF method). The inversion in the order of acidities experimentally observed when a series of haloacetic acid s is immersed into aqueous solution is reproduced. It is shown that th e inversion is caused by competition between substitution and solvatio n effects. The solvation effect is discussed in molecular detail in te rms of the charge distribution of the solute and the solute-solvent ra dial distribution functions.