Preparation of Alcohols - Oxymercuration-Demercuration

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

Concept: A two-step hydration process where mercuric acetate reacts with an alkene to form a cyclic mercurinium ion, followed by reductive demercuration with sodium borohydride.

Notation & Key Points:

• Regioselectivity: Gives Markovnikov's addition of water without forming a free carbocation.
• Intermediate: Involves a cyclic mercurinium ion intermediate.
• Rearrangements: No carbocation rearrangements occur, making it ideal for obtaining Markovnikov alcohols from alkenes prone to rearrangement.