Oxymercuration Reaction - Oxymercuration-reduction

Oxymercuration-reduction

In practice, the mercury adduct product created by the oxymercuration reaction is almost always treated with sodium borohydride (NaBH₄) in aqueous base in a reaction called demercuration. In demercuration, the acetoxymercury group is replaced with a hydrogen in a stereochemically insensitive reaction known as reductive elimination. The combination of oxymercuration followed immediately by demercuration is called an oxymercuration-reduction reaction.

Therefore, the oxymercuration-reduction reaction is the net addition of water across the double bond. Any stereochemistry set up by the oxymercuration step is scrambled by the demercuration step, so that the hydrogen and hydroxy group may be cis or trans from each other. Oxymercuration-reduction is a popular laboratory technique to achieve alkene hydration with Markovnikov selectivity while avoiding carbocation intermediates and thus the rearrangement which can lead to complex product mixtures.