Self-diffusion of caffeine and methanol in ternary mixtures caffeine–methanol–carbon tetrachloride at temperatures of 298 and 313 K

Abstract

The self-diffusion of caffeine and methanol in the ternary mixtures methanol–carbon tetrachloride (binary solvent)–caffeine (solute) have been investigated by the pulsed gradient spin-echo nuclear magnetic resonance (PGSE NMR) method at the temperatures of 298 and 313K. The dependences of self-diffusion coefficients on the composition of binary solvent have a minimum in the region of 0.2mol fraction of methanol. It has been found that self-diffusion of caffeine is mainly determined by the binary solvent viscosity. As it has been shown, in order to describe the experimental data correctly, the molecular association model of methanol should include cyclic tetramers. The self-association constants, the enthalpies of hydrogen bonds formation and the microfriction factors of the chain associates and the cyclic tetramers of methanol have been estimated.