The reaction of compound $\mathbf{P}$ with $\mathrm{CH}_{3} \mathrm{MgBr}$ (excess) in $\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{O}$ followed by addition of $\mathrm{H}_{2} \mathrm{O}$ gives $\mathbf{Q}$. The compound $\mathbf{Q}$ on treatment with $\mathrm{H}_{2} \mathrm{SO}_{4}$ at $0^{\circ} \mathrm{C}$ gives $\mathbf{R}$. The reaction of $\mathbf{R}$ with $\mathrm{CH}_{3} \mathrm{COCl}$ in the presence of anhydrous $\mathrm{AlCl}_{3}$ in $\mathrm{CH}_{2} \mathrm{Cl}_{2}$ followed by treatment with $\mathrm{H}_{2} \mathrm{O}$ produces compound $\mathbf{S}$. [Et in compound $\mathbf{P}$ is ethyl group] (see structure) The reactions, $\mathbf{Q}$ to $\mathbf{R}$ and $\mathbf{R}$ to $\mathbf{S}$, are

(D) Friedel-Crafts alkylation and Friedel-Crafts acylation

(A) Dehydration and Friedel-Crafts acylation

(B) Aromatic sulfonation and Friedel-Crafts acylation

(C) Friedel-Crafts alkylation, dehydration and Friedel-Crafts acylation

Alcohols Phenols and Ethers — JEE Advanced · 2017 · 21 May 2017 · Paper 2 Question with Solution

Passage

The reaction of compound

P

with

CH_{3} MgBr

(excess) in

(C_{2} H_{5})_{2} O

followed by addition of

H_{2} O

gives

Q

. The compound

Q

on treatment with

H_{2} SO_{4}

0^{\circ} C

gives

R

. The reaction of

R

with

CH_{3} COCl

in the presence of anhydrous

AlCl_{3}

CH_{2} Cl_{2}

followed by treatment with

H_{2} O

produces compound

S

. [Et in compound

P

is ethyl group]

(see structure)

The reaction of compound

P

with

CH_{3} MgBr

(excess) in

(C_{2} H_{5})_{2} O

followed by addition of

H_{2} O

gives

Q

. The compound

Q

on treatment with

H_{2} SO_{4}

0^{\circ} C

gives

R

. The reaction of

R

with

CH_{3} COCl

in the presence of anhydrous

AlCl_{3}

CH_{2} Cl_{2}

followed by treatment with

H_{2} O

produces compound

S

. [Et in compound

P

is ethyl group]

(see structure)

The reactions,

Q

R

and

R

S

, are

(A)Dehydration and Friedel-Crafts acylation
(B)Aromatic sulfonation and Friedel-Crafts acylation
(C)Friedel-Crafts alkylation, dehydration and Friedel-Crafts acylation
(D)Friedel-Crafts alkylation and Friedel-Crafts acylation✓ Correct

Answer: (D)

Solution

Q to R: The tertiary alcohol Q undergoes acid-catalyzed dehydration with

H_{2} SO_{4}

to form a carbocation, which then undergoes intramolecular Friedel-Crafts alkylation (electrophilic aromatic substitution) to form a new ring, giving R. This is both dehydration and Friedel-Crafts alkylation.

R to S: R undergoes Friedel-Crafts acylation with

CH_{3} COCl

and

AlCl_{3}

to introduce an acetyl group, forming S.

Therefore, the reactions are: Friedel-Crafts alkylation (with dehydration) and Friedel-Crafts acylation.

JEE Advanced · 2017 · 21 May 2017 · Paper 2 · Single correct option

JEE Advanced · 2017 · 21 May 2017 · Paper 2 · Alcohols Phenols and Ethers

Solution

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