What amount of bromine will be required to convert 2 g of phenol into 2, 4, 6-tribromophenol? (Given molar mass in \(\mathrm{g} \mathrm{mol}^{-1}\) of \(\mathrm{C}, \mathrm{H}, \mathrm{O}, \mathrm{Br}\) are 12, \(1,16,80\) respectively)

JEE Main · 2025 · 23 Jan 2025 · Shift 1 · Alcohols Phenols and Ethers

What amount of bromine will be required to convert 2 g of phenol into 2, 4, 6-tribromophenol? (Given molar mass in

g mol^{- 1}

C, H, O, Br

are 12,

1, 16, 80

respectively)

(A)10.22 g✓ Correct
(B)6.0 g
(C)4.0 g
(D)20.44 g

Answer: (A)

Solution

Phenol undergoes electrophilic aromatic substitution with bromine; the strongly activating hydroxyl group directs bromination to both ortho positions and the para position, giving 2,4,6-tribromophenol:

C_{6} H_{5} OH + 3B r_{2} \to C_{6} H_{2} B r_{3} OH + 3HBr

Molar mass of phenol

= 6 (12) + 6 (1) + 16 = 94 g mo l^{- 1}

.

Moles of phenol

= \frac{2}{94} = 0.0213 mol

.

Each mole of phenol consumes 3 mol of

B r_{2}

, so moles of

B r_{2}

required

= 3 \times 0.0213 = 0.0638 mol

.

Mass of

B r_{2}

= 0.0638 \times 160 = 10.22 g

JEE Main · 2025 · 23 Jan 2025 · Shift 1 · Single correct option

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JEE Main · 2025 · 23 Jan 2025 · Shift 1 · Alcohols Phenols and Ethers

Solution

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