THE MOLECULAR INTERACTION GROUP CONTRIBUTIONS FOR DIELECTRIC SOLVENTS

We test the new group division formalism of Wu and Sandler (WS) for the group contribution methods in solution thermodynamics. We employ the reference interaction site method (RISM) of statistical mechanics as the foundation of the group contribution method. The integral equations are solved for amine and alkanolamine molecules (trimethylamine, triethanolamine, and methyldiethanolamine). The site-site potential used is of the Lennard-Jones type. We demonstrate that the WS group identification is useful. Its use simplifies a 6-group, 10-mer (100 pair interactions) RISM equation to a 2-group 3-mer (9 pair interactions) one (for methyldiethanolamine). This renders the RISM method tractable. Common group parameters epsilon and sigma are obtained for all the amines studied, since this is the raison d'etre of the group contribution methods. The results are encouraging for the amines studied.