Diffusion Studies of Phenylenediamine Isomers in Water-Monohydric-Alcohol Systems

The study of isomer diffusion provides useful information regarding solvent effects for mixture analysis. Isomers, particularly those with similar hydrodynamic radii, provide a mechanism for probing solute–solvent interactions. Here nuclear magnetic resonance was used to measure the self-diffusion of phenylenediamine isomers in various water–monohydric-alcohol (i.e. methanol, ethanol, 1-propanol, and tert-butanol) solvents. These systems allowed the effect of solvent modulation on isomer diffusion to be examined. It was found that the resonances of phenylenediamine isomers in a mixture were separable via diffusion, with the separation becoming greater at higher concentration of monohydric-alcohols. Unlike previously shown for dihydroxybenzene isomers, all three phenylenediamine isomers were differentiable via diffusion.