The reactions of alkoxide-alkanol negative ions with carbonyl compounds. An ion cyclotron resonance and ab initio study

Abstract

Simple alkyl aldehydes, ketones and esters containing the unit >: CH-CO-react with alkoxide-alkanol negative ions [RO----HOR] to form stable [M+RO-] negative ions (neutral denoted by M). The initial intermediate in the reaction sequence is produced by the formation of a hydrogen bond between the negatively charged oxygen of [RO----HOR] and the hydrogen of the > >CH-CO- unit. This intermediate decomposes to the stable product ion by two reaction sequences: (i) by direct elimination of ROH, and (ii) by rearrangement to a decomposing 'doubly-solvated' negative ion in which the central hydrogen of [RO----HOR] and the hydrogen of the >CH-CO unit become identical. As both reaction pathways are complex, all intermediates and certain transition states have been properly defined by using ab initio calculations at the 4-31G level.