The self-diffusion of parabens (methyl-, propylparaben) and tetramethylsilane in the binary solvent carbon tetrachloride – Co-solvent (methanol‑d4, acetone‑d6) at 278, 298 and 318 K

Abstract The self-diffusion of parabens (methylparaben, propylparaben) and tetramethylsilane in the binary solvents carbon tetrachloride – co-solvent (methanol‑ d 4 , acetone‑ d 6 ) has been investigated by the pulsed gradient spin-echo nuclear magnetic resonance (PGSE NMR) method in the range of temperatures from 278 to 318 K. The self-diffusion coefficients of paraben and tetramethylsilane increase as the concentration of acetone‑ d 6 increases and have a minimum for paraben and an inflection point for tetramethylsilane when the methanol‑ d 4 concentration increases. Based on the Stokes-Einstein equation it is shown that the paraben hydrodynamic radius in the binary solvent acetone‑ d 6 – carbon tetrachloride is practically independent of the acetone‑ d 6 concentration and has a maximum in the binary solvent methanol‑ d 4 – carbon tetrachloride. This behavior in both cases is explained by the paraben self-association degree and the heteroassociation degree of paraben – co-solvent.