Possible role of nonclassical ions in acid catalysed dehydration of ethanol

Abstract

On the basis of CNDO/2 calculations,the geometrical changes accompanying the activation of the ethanol molecule in the acid catalysed dehydration have been analysed. The activation of the ethanol molecule via protonation of its hydroxyl group manifests itself above all in the lengthening of the C-O bond. Further elongation of this bond leads to the formation of nonclassical structure, in extreme case to the nonclassical ion which is more stable then the classical one. The above reaction mechanism is confronted with the known facts and provides acceptable unifiying explanation of e.g. the stereoselectivity anomalies and the isotope effect of β-deuterated alcohols as well as other experimental and theoretical data.