2-Methylbut-2-ene is treated separately with (i) BH3.THF then H2O2/NaOH and (ii) Hg(OAc)2, H2O then NaBH4. Which statement is correct?

(i) gives chiral 3-methylbutan-2-ol, formed as a racemate; (ii) gives achiral 2-methylbutan-2-ol

(i) gives achiral 3-methylbutan-1-ol; (ii) gives chiral 3-methylbutan-2-ol

(i) gives 2-methylbutan-2-ol; (ii) gives 3-methylbutan-2-ol

(i) and (ii) both give 2-methylbutan-2-ol

JEE Advanced levelSingle correct optionDifficulty 3 of 3o2207

2-Methylbut-2-ene is treated separately with (i) $BH X_{3} \cdot THF$ then $H X_{2} O X_{2} / NaOH$ and (ii) $Hg (OAc) X_{2}, H X_{2} O$ then $NaBH X_{4}$ . Which statement is correct?

A(i) gives chiral 3-methylbutan-2-ol, formed as a racemate; (ii) gives achiral 2-methylbutan-2-ol
B(i) gives achiral 3-methylbutan-1-ol; (ii) gives chiral 3-methylbutan-2-ol
C(i) gives 2-methylbutan-2-ol; (ii) gives 3-methylbutan-2-ol
D(i) and (ii) both give 2-methylbutan-2-ol

Hydroboration puts OH on the less substituted C3, giving

(CH X_{3}) X_{2} CH - CH (OH) CH X_{3}

, which has a stereocentre and is racemic. Oxymercuration puts OH on the tertiary C2, giving

(CH X_{3}) X_{2} C (OH) CH X_{2} CH X_{3}

, which has no stereocentre.