Limiting mutual diffusion of nonassociated aromatic solutes

Abstract

Limiting mutual diffusion coefficients D12 of benzene, chlorobenzene, toluene, ethylbenzene, naphthalene, 1,2,4-trichlorobenzene, propylbenzene, mesitylene and biphenyl in cyclohexane and acetone have been measured at selected temperatures by using the chromatographic peak-broadening method. When 1/D12 is plotted against the van der Waals volume of the solutes, a straight line is obtained for each temperature of the liquid systems studied. It is also found that the diffusion data measured at different temperatures obey the Arrhenius equation. The activation energies calculated from this equation for all solutes in a given solvent are about the same. The experimental mutual diffusion coefficients of the nonassociated aromatic molecules measured in this work were fitted by the following equation: D12=T/(pVvdw+q)(Vf/Vm)/n2/3d1/3 where p and q are constants, T is the system temperature, n and d is the solvent viscosity and density, respectively, Vf/Vm is the ratio of the free volume to the molar volume of a solvent, and Vvdm is the van der Waals volume of solute. The equation fits all data for each solvent system studied to within +(-) 2.2%. Other diffusion data of pseudoplanar solutes in various organic solvents were collected from the literature. The same equation above fits a total of all 318 data collected and measured to within +(-)4.3%.