The self-diffusion of parabens (methyl-, propylparaben) and tetramethylsilane in the binary solvent carbon tetrachloride - Co-solvent (methanol-d(4), acetone-d(6)) at 278, 298 and 318 K

摘要

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. (C) 2019 Elsevier B.V. All rights reserved.