Self-diffusion and molecular association in the binary systems dimethyl sulfoxide – chloroform and acetone – chloroform

The self-diffusion of components of such binary mixtures as dimethyl sulfoxide (DMSO) – chloroform and acetone – chloroform has been investigated by pulsed gradient spin-echo nuclear magnetic resonance (PGSE NMR) method and molecular dynamics (MD) simulation at ambient conditions. The self-diffusion coefficients obtained by the experimental and theoretical methods are well agreed with each other. Detailed analysis of structural characteristics (fraction of molecules with i hydrogen bonds, the average number of hydrogen bonds), as well as interaction energy in hydrogen-bonded complexes of DMSO – DMSO, DMSO – chloroform, acetone – acetone, acetone – chloroform made it possible to estimate the influence of the self- and heteroassociation on the self-diffusion of the mixture components. A set of methods showed that it is necessary to take into account not only heteroassociates with a composition of 1:1 just like acetone – chloroform mixture for sufficient approximation of the experimental data for DMSO – chloroform mixture. It has been established that for cosolvents (DMSO and acetone) with a similar molecular structure, a different behavior of concentration dependences of the self-diffusion coefficients in binary systems is connected with the features of self-association and heteroassociation.