The effect on the rate of reaction of each of a series of Menschutkin processes on changing from a molecular solvent to an ionic liquid was investigated. In each case, the rate acceleration observed at room temperature could be attributed to the change in the entropy of the system on reaching the transition state, offsetting any enthalpic cost.

(79)Br NMR spectroscopy has been used to monitor a series of reactions in which the bromide ion is produced, including the Menschutkin reaction of pyridine with a range of substituted benzyl bromides and a Heck coupling process. In cases where the process could also be monitored using (1)H NMR spectroscopy, the kinetic analyses using heteronuclear magnetic resonance spectroscopy were shown to be completely consistent. Both the utility of the process in following reactions which may be difficult to analyse using other techniques and the practical limitations associated with solvent choice are discussed.