The reaction of NN′-dimethylimidazolidine-2-thione and of 2,3-dihydro-1,2,5-trimethyl-1,2,4-triazole-3-thione with methyl iodide. Reaction rates, transfer enthalpies, and extended Brönsted treatments in methanol–acetonitrile mixtures

Abstract

The rate constants and activation enthalpies for the reaction of two thione derivatives, NN′-dimethylimidazolidine-2-thione and 2,3-dihydro-1,2,5-trimethyl-1,2,4-triazole-3-thione, with methyl iodide have been measured in acetonitrile–methanol mixtures. Heats of solution were also measured for methyl iodide, two thione derivatives, and two methyl iodide salts of the thione in the same solvent mixtures. Some of the empirical energy correlations which have been carried out for the two reactions, one of the activation enthalpy versus activation free energy plots, and both the extended Brönsted relationships with respect to solvent variation exhibited non-linear behaviour. Transfer enthalpies of the above solutes have been rationalized in terms of ‘more physical’ and of specific interactions. The extended Brönsted plots, which were performed in terms of ‘more physical’ transfer enthalpies, exhibited linear patterns. The physical meaning of these plots is discussed.