THE MECHANISM OF OXYMERCURATION OF ALKENES

Abstract

A factual test of several possible mechanisms by which alkenes are oxymercurated shows that while addition of mercuric acetate to cyclohexene can be effected smoothly, this 1-acetoxy-2-acetoxymercuricyclohexane cannot be an intermediate in the conversion of cyclohexene in methanolic mercuric acetate to 1-methoxy-2-acetoxymercuricyclohexane. The rate at which the first compound is converted to the second in methanol is much too slow to account for the rate of methoxymercuration. Indeed the behavior of conversion indicates that the first compound reverts in methanol to cyclohexene which then combines with the elements of methoxymercuric acetate. Ionic mechanisms have been shown to be untenable since hydroxymercuration is slower than methoxymercuration although it occurs in a solvent which is much more polar than methanol. A co-ordinative dipole mechanism is suggested which explains the complete retention of configuration during addition as well as the function of boron trifluoride as an accelerator in this reaction.