Diffusion Coefficients of Substituted Benzenes at High Dilution in Water

The interdiffusion coefficient D a w of six hydrophobic benzene derivatives ( a = chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, bromobenzene, 1,2-dibromobenzene, 1,4-dibromobenzene) in aqueous solution (w) at 25 °C is measured at different concentrations below 10 -5 solute mole fractions using the Taylor dispersion technique. On the basis of the experimental uncertainty around 4%, a distinct concentration dependence is not recognizable. Analysis of the interdiffusion coefficients with the Stokes−Einstein equation shows greater values than expected from the limit of a complete solute−solvent contact (“stick limit”), and in addition substance-specific deviations. Chemical engineering correlations for presently available from the literature yield unsatisfactory results for this class of predominantly hydrophobic compounds.