Menschutkin reactions of N-methylimidazole and of N-methylbenzimidazole with methyl iodide in acetonitrile–methanol. Family-dependent and family-independent properties

Abstract

Rate constants and activation parameters have been determined for the reactions of the aromatic amines N-methylimidazole and N-methylbenzimidazole with methyl iodide in acetonitrile–methanol. The enthalpies of solution have also been determined for the relevant species in the same solvent mixtures. Activation enthalpies in acetonitrile and the specific interaction enthalpies between the amine and methanol show a linear correlation with pK_a values determined in water only over a narrowly defined type of structure. However, transition-state indices for the two reactions defined in terms of physical interaction energy, α_phys and β_phys, show the behaviour anticipated by analogy, with reactions of pyridine derivatives (i.e., family-independent character).