Assertion (A): Hydroboration-oxidation of an alkene gives the anti-Markovnikov alcohol without rearrangement. Reason (R): In the addition of $B - H$ , boron adds to the more substituted alkene carbon.

ABoth A and R are true and R is the correct explanation of A
BBoth A and R are true but R is not the correct explanation of A
CA is true but R is false
DA is false but R is true

Answer: C

A is true: the concerted four-centre addition involves no carbocation, and B (hence OH) goes to the less hindered carbon, giving the anti-Markovnikov alcohol. R is false because boron adds to the less substituted carbon for steric (and electronic) reasons.

Practice Organic Reaction Mechanisms II: Electrophilic and Radical Reactions More on Electrophilic addition to alkenes and Markovnikov rule

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Assertion (A): Hydroboration-oxidation of an alkene gives the anti-Markovnikov alcohol without rearrangement. Reason (R): In the addition of B−H, boron adds to the more substituted alkene carbon.

Answer: C

More questions on Electrophilic addition to alkenes and Markovnikov rule

Assertion (A): Hydroboration-oxidation of an alkene gives the anti-Markovnikov alcohol without rearrangement. Reason (R): In the addition of $B - H$ , boron adds to the more substituted alkene carbon.