JEE Main · 2024 · 27 Jan 2024 · Shift 2 · Hydrocarbons

The final product A, formed in the following reaction sequence is:

Answer: (D)

Solution

Styrene,

P h - C H = C H_{2}

, first undergoes hydroboration with

B H_{3}

: boron adds to the terminal, less-substituted carbon (anti-Markovnikov, syn addition). Oxidative workup with

H_{2} O_{2} / O H^{-}

replaces boron with

- O H

at the same carbon, retaining its position, to give the primary alcohol

P h - C H_{2} - C H_{2} - O H

.

Treating this alcohol with

H B r

converts the –OH to –Br by

S_{N} 2

substitution, giving

P h - C H_{2} - C H_{2} - B r

. Reaction of the bromide with magnesium in dry ether generates the Grignard reagent

P h - C H_{2} - C H_{2} - M g B r

.

This Grignard reagent adds to the carbonyl carbon of formaldehyde

(H C H O)

, and aqueous acidic workup

(H_{3} O^{+})

then hydrolyses the resulting magnesium alkoxide, extending the chain by one carbon to give the final primary alcohol

P h - C H_{2} - C H_{2} - C H_{2} - O H

— product A.

JEE Main · 2024 · 27 Jan 2024 · Shift 2 · Single correct option