THE EFFECTS OF MOLECULAR ASSOCIATION ON MUTUAL DIFFUSION IN ACETONE

Limiting mutual diffusion coefficients of aromatic compounds in aceton e have been measured at 298.2 K by using the chromatographic peak-broa dening method. The data of the polar and nonpolar pseudoplanar solutes are compared, and the effects of molecular association on diffusion a s well as the solvation numbers are determined. It is found that the e ffects of hydrogen bonding are such that -OH>-NH2>-SH, and that the so lvation numbers are approximately equal for solutes containing the sam e polar group. Using ab initio molecular orbital theory, molecular sol ute-acetone interaction energies have been calculated. There exists a nearly linear relationship between the interaction energy and the effe ct of solute-solvent association on diffusion. The applicability of th e rough-hard-sphere theory to the diffusion of associated molecules is discussed. (C) 1997 American Institute of Physics.