A COMPARATIVE-STUDY OF ELECTROSTATIC SIMILARITY INDEXES

In this study, the ethanol molecule was superimposed on a set of molec ules (ethane, ethantiol, ethilamine, methanol, propane and water). Sim ilarity, on the basis of the molecular electrostatic potential (MEP), was evaluated on the semiempirical AM1 and HF/6-31+G. The Carbo index was used as a measure of similarity and three different formalisms we re used for similarity evaluations: the MEP by the grid method, the ES P charge by the grid method and the ESP charge by the Gaussian approxi mation. It was found that the choice of the MO method and formalism do not play an important role when indices are high. When we superimpose two electrostatic potentials of molecules that are not similar, as fo r example electrostatic potentials of ethanol and ethane, the Gaussian approximation gives evidently higher values of the similarity indices than the grid method.