Hydroboration-oxidation of an alkene yields what type of alcohol and is Markovnikov or anti-Markovnikov?

• A. Anti-Markovnikov alcohol (BH3 adds to less substituted carbon)
• B. Markovnikov alcohol
• C. Ketone
• D. Ether

Answer: (A)

Hydroboration-oxidation gives an alcohol with anti-Markovnikov regiochemistry. In the hydroboration step, the boron atom adds to the less substituted carbon of the double bond and hydrogen adds to the more substituted carbon, doing so in a concerted, syn fashion. This preference arises because bulky boron prefers the less hindered carbon and no carbocation is formed. When the boron–carbon bond is then oxidized, the boron is replaced by a hydroxyl group. Since boron was attached to the less substituted carbon, the resulting alcohol places the OH on that same, less substituted carbon, giving an anti-Markovnikov product. The other options describe products that don’t come from this sequence: a Markovnikov alcohol would arise from acid-catalyzed hydration, while ketones or ethers aren’t formed by hydroboration-oxidation.