The effects of using an ionic liquid as a solvent for a reaction that proceeds through a phenonium ion

Abstract

AbstractA unimolecular reaction that proceeds predominantly through a phenonium ion intermediate was investigated in mixtures of an ionic liquid and methanol. Varying the proportion of the ionic liquid in the reaction mixture led to an increase in the rate constant compared with methanol when very small amounts of ionic liquid were present in the reaction mixture and a decrease when higher proportions of the salt were present. Activation parameters determined for the process showed that the effect of changing the solvent composition on the rate constant was due to a key interaction between the ionic liquid and the transition state of the process, similar to other unimolecular processes. Analysis of the stereochemistry of the products demonstrated that the ionic liquid had no effect on either the ratio of the stereochemistry of the substitution products, or the ratio of the substitution and eliminations mechanisms occurring in solution.