Investigating the origin of entropy-derived rate accelerations in ionic liquids

The effects on the rate and activation parameters of a series of Menschutkin processes on changing from a molecular solvent to an ionic liquid were investigated. The removal of delocalised pi-systems from the reagents does not affect the change in activation parameters on changing solvent. In each of the cases investigated, rate accelerations observed on moving to the ionic liquid could be attributed to an increase in reaction entropy. This suggests a specific interaction of the ionic liquid with the nucleophilic centre, rather than the delocalised pi-systems of either the electrophile or the nucleophile.