Treatment of benzene with CO/HCl in the presence of anhydrous $\mathrm{AlCl}_{3} / \mathrm{CuCl}$ followed by reaction with $\mathrm{Ac}_{2} \mathrm{O} / \mathrm{NaOAc}$ gives compound $\mathbf{X}$ as the major product. Compound $\mathbf{X}$ upon reaction with $\mathrm{Br}_{2} / \mathrm{Na}_{2} \mathrm{CO}_{3}$, followed by heating at 473 K with moist KOH furnishes $\mathbf{Y}$ as the major product. Reaction of $\mathbf{X}$ with $\mathrm{H}_{2} / \mathrm{Pd}-\mathrm{C}$, followed by $\mathrm{H}_{3} \mathrm{PO}_{4}$ treatment gives $\mathbf{Z}$ as the major product. The compound $\mathbf{Y}$ is

Hydrocarbons — JEE Advanced · 2018 · 20 May 2018 · Paper 1 Question with Solution

Passage

Treatment of benzene with CO/HCl in the presence of anhydrous

AlCl_{3} / CuCl

followed by reaction with

Ac_{2} O / NaOAc

gives compound

X

as the major product. Compound X upon reaction with

Br_{2} / Na_{2} CO_{3}

, followed by heating at 473 K with moist KOH furnishes

Y

as the major product. Reaction of

X

with

H_{2} / Pd - C

, followed by

H_{3} PO_{4}

treatment gives Z as the major product.

Treatment of benzene with CO/HCl in the presence of anhydrous

AlCl_{3} / CuCl

followed by reaction with

Ac_{2} O / NaOAc

gives compound

X

as the major product. Compound

X

upon reaction with

Br_{2} / Na_{2} CO_{3}

, followed by heating at 473 K with moist KOH furnishes

Y

as the major product. Reaction of

X

with

H_{2} / Pd - C

, followed by

H_{3} PO_{4}

treatment gives

Z

as the major product.

The compound

Y

Answer: (C)

The reaction sequence:

Benzene + CO/HCl with $AlCl_{3} / CuCl$ gives benzaldehyde (Gattermann-Koch reaction).
Benzaldehyde + $Ac_{2} O / NaOAc$ gives cinnamic acid (Perkin reaction), which is compound X: $C_{6} H_{5} CH = CHCOOH$ .
X + $Br_{2} / Na_{2} CO_{3}$ followed by heating with moist KOH at 473 K gives phenylacetylene (decarboxylation and elimination), which is compound Y.

Compound Y is phenylacetylene:

C_{6} H_{5} C \equiv CH

Correct answer: (C)

JEE Advanced · 2018 · 20 May 2018 · Paper 1 · Single correct option