Oxymercuration-Demercuration (OMDM)

$$\text{R--CH=CH}_2 \xrightarrow{1) \, \text{Hg(OAc)}_2, \, \text{H}_2\text{O} \quad 2) \, \text{NaBH}_4 / \text{OH}^-} \text{R--CH(OH)--CH}_3$$

Concept: A two-step conversion of alkenes into alcohols without carbocation rearrangement. Follows Markovnikov's Addition of water ($$\text{H}$$ and $$\text{OH}$$). Proceeds via a cyclic mercurinium ion intermediate, so no carbocation rearrangement takes place. Overall stereochemistry is anti-addition.

• Step 1 (Oxymercuration): Mercuric acetate [$$\text{Hg(OAc)}_2$$] in aqueous THF.
• Step 2 (Demercuration): Sodium borohydride [$$\text{NaBH}_4$$] in basic medium.