GAS-PHASE AMBIDENT REACTIVITY OF ACYCLIC ENOLATE ANIONS

The gas-phase reactions between acyclic enolate anions and unsaturated perfluorocarbon compounds have been studied with use of the method of Fourier transform ion cyclotron resonance. Unsaturated perfluorocarbon compounds react in a characteristic way with either the oxygen or carbon end of an enolate anion to produce distinctive ionic products. The relative yields of ionic products formed in the reactions of a series of ambident acyclic enolate anions of the type R1HC=CR2O-, reveal the whole spectrum of ambident reactivity from 100% addition via the carbon nucleophilic center up to 99% addition via the oxygen nucleophilic center. There appears to be a correlation between the reaction selectivity and the experimental electron detachment threshold energies, and thus the energy of the HOMO, of the enolate anions. The nature of this correlation suggests that the competition between the reaction channels is controlled by specific frontier orbital interactions of the reactants rather than by the charge distribution in the enolate anions alone.