Effect of solvent on diffusion: probing with nonpolar solutes

Area of Science:

• Physical Chemistry
• Chemical Physics
• Thermodynamics

Background:

• Understanding molecular diffusion is crucial in various chemical processes.
• Previous models have limitations in accurately predicting diffusion coefficients based on solvent properties.

Purpose of the Study:

• To report new diffusion coefficient data for specific solutes and solvents.
• To elucidate the effect of solvent properties on molecular diffusion.
• To develop and validate a more accurate model for solvent dependence of diffusion.

Main Methods:

• Measurement of limiting mutual diffusion coefficients at different temperatures.
• Analysis of existing literature data for various solute-solvent pairs.
• Development and application of a new predictive model for diffusion coefficients.

Main Results:

• New diffusion data reported for carbon tetrachloride, benzene, toluene, naphthalene, and biphenyl in different solvents.
• The previously developed relation for disc-shaped solutes is also valid for spherical solutes.
• A new model incorporating dielectric effects accurately predicts diffusion coefficients (±2.7% deviation).

Conclusions:

• Solvent properties like free volume, molar density, molecular mass, and fractional viscosity significantly influence diffusion.
• The developed model provides a more accurate representation of solvent effects on diffusion compared to other models.
• The study also presents an expression for Zwanzig's effective hydrodynamic radius.