Effect of the Ionic Liquid 1-Butyl-3- Methylimidazolium Bistrifluoromethane- Sulfonamide on Nucleophile Reactivity in Unimolecular Solvolysis Reactions Involving Carbocationic Intermediates

Abstract

Solvolysis studies of pivaloyl triflate were carried out in the ionic liquid 1-butyl-3-methylimidazolium bistrifluoromethanesulfonamide with various cosolvents. Reaction solutions were analyzed by 1 H NMR and the relative amounts of substitution and elimination products measured. It was found that regardless of cosolvent, increasing the ionic liquid:cosolvent ratio leads to increased elimination product. The rate of increase, however, is dependent on the identity of the cosolvent. Kamlet-Taft solvatochromic parameters of hydrogen bond accepting and donating ability were invoked to explain this phenomenon.

Unimolecular Solvolyses in Ionic Liquid: Alcohol Dual Solvent Systems

“…Our preliminary studies have shown that increasing the mole fraction of IL in an IL:alcohol dual solvent system increases the favorability of the elimination pathway vs. nucleophilic attack [15,16]. It was observed that nearly all IL cosolvents caused an increase in the favorability of the elimination pathway.…”

“…The triflate derivative of pivaloin, 1, was prepared from the corresponding alcohol as previously described [15]. The ionic liquid, 1-butyl-3-methylimidazolium bistrifluoromethane-sulfonamide, [C 4 C 1 im][NTf 2 ], was prepared and dried as previously described [12] [18].…”