RELATIVE RATES OF BASE-CATALYZED EXCHANGE OF ALPHA- AND GAMMA-HYDROGEN IN AN α,β-UNSATURATED KETONE

Abstract

Relative rates of base-catalyzed exchange of vinylic and allylic hydrogen, in an α,β-unsaturated ketone, have been determined. In refluxing heavy water, with OD− catalyst, vinyl hydrogen was exchanged about 170 times as rapidly as allyl hydrogen. In CD3OD containing CD3O− the two rates were equal or nearly equal at ambient temperature. Factors which may contribute to the observed difference between the relative rates are discussed and results of simple molecular orbital calculations are presented.