Diffusion in n-alkyl benzenes. Diffusion of 1,1,2,2-tetrabromoethane in a homologous series of n-alkyl benzenes
Abstract
The dependence of the product D0η0(where D0 is the interdiffusion coefficient at infinite dilution and η0 is the solvent viscosity) on the solvent molar volume Vm has been investigated for 1,1,2,2-tetrabromoethane diffusing in n-alkyl benzenes at 20, 25, 35 and 45°C.
The experimental results at 20, 25 and 35°C show that D0η0 is an increasing function of Vm. Anomalous in this respect are the data for benzene and toluene which do not show the progressive increase of D0η0 with Vm. The dependence of D0η0 on Vm at these three temperatures was found to be non-linear over the entire range of Vm employed in the present study and no reasonable extrapolation to zero Vm could be carried out.
The plots of D0η0 against Vm at 35 and 45°C show a discontinuity at C6/C7, the effect becoming more pronounced with increasing temperature. A qualitative explanation for this effect is suggested.
The Stokes–Einstein radius (r) at 45°C calculated for 1,1,2,2-tetrabromoethane using the expression (D0η0)Vm=0 =kT/6πr, for the solvent range C0-C6, was identical to the molecular radii obtained by other methods.