SCRF CALCULATION OF THE EFFECT OF HYDRATION ON THE TOPOLOGY OF THE MOLECULAR ELECTROSTATIC POTENTIAL

The effect of water on the topology of the molecular electrostatic pot ential (MEP) of eight small prototypical molecules (H2O, NH3, CH3OH, C H3NH2, CH2O, HF, CH4, and HCOOH) has been studied at the ab initio 6-3 1G level by using the Miertus-Scrocco-Tomasi self-consistent reaction field method. Both the general MEP distribution and the critical poin ts of the MEP have been used to quantify the magnitude of the polarizi ng effect of water. The results demonstrate the complexity and specifi city of the water effect on the solute charge distribution. The formal dehyde is the most polarizable molecule, while the methane is least af fected by the water. The analysis of the MEP distributions and critica l points demonstrates that most of the changes induced by the solvent happen in the lone pair region and in the vicinity of acidic hydrogens . The importance of the polarizing effect of the water on the chemical reactivity of the molecules in aqueous environments is discussed.