Benzene is treated with Oleum to give [A], which is then treated with (i) NaOH, heat (ii) H+ to give [B]. Writ

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Q. Benzene is treated with Oleum to give [A], which is then treated with

(i) NaOH, heat

(ii) H+ to give [B]. Write chemical formula of [A] and [B] in the above reaction sequence.

Rajasthan RbseRajasthan Board Senior Secondary Examination 2024Subjective· 2mImportance★★★★★

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This is the industrial route from benzene to phenol: sulphonation to benzenesulphonic acid, followed by alkali fusion and acidification.

Step 1: Benzene reacts with oleum (fuming H2SO4, i.e. SO3 in H2SO4) in an electrophilic aromatic substitution (sulphonation):

C6H6 + SO3 (from oleum) -> C6H5SO3H

[A] = benzenesulphonic acid.

Step 2: [A] is fused with molten NaOH on heating; the sulphonic acid group is displaced by -OH, giving sodium phenoxide: …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2025Set X11 markMCQ
$Q. Cumene hydroperoxide on hydrolysis with dilute acid gives ______.$
(a) alcohol and phenol
(b) only phenol
(c) phenol and acetone
(d) alcohol and acetone
›Reveal solutionSolution

Cumene hydroperoxide, on hydrolysis with dilute acid, cleaves to give phenol and acetone (the industrial "cumene process" for phenol).

In the industrial cumene process, cumene (isopropylbenzene) is air-oxidised to cumene hydroperoxide, $\text{C}_6\text{H}_5\text{C(CH}_3)_2\text{OOH}$ . Treatment with dilute acid then cleaves it: …
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CBSE 2023Set ANNUAL1 markMCQ
$Q. In reaction of manufacturation of phenol from cumene the by-product is$
(a) Tribromophenol
(b) Benzoquenone
(c) Picric acid
(d) Acetone
›Reveal solutionSolution

In the industrial cumene process, oxidation of cumene followed by acid hydrolysis of the hydroperoxide yields both phenol and acetone.

Cumene (isopropylbenzene) is air-oxidised to cumene hydroperoxide. Treating this hydroperoxide with dilute acid causes rearrangement and cleavage to give phenol as the main product, with acetone (propan-2-one …

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CBSE 2022Set ANNUAL1 markMCQ
$Q. Isopropylbenzene on air oxidation followed by decomposition by dilute acid gives _____.$
(a) $C_6H_5OH$
(b) $C_6H_5COOCH_3$
(c) $C_6H_5COOH$
(d) $C_6H_5CHO$
›Reveal solutionSolution

Air oxidation of cumene followed by acid cleavage is the industrial cumene process for making phenol.

Isopropylbenzene (cumene) is air-oxidised to cumene hydroperoxide, which on treatment with dilute acid undergoes rearrangement/cleavage to give phenol and acetone as a co-product: …

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Q.Benzene is treated with Oleum to give [A], which is then treated with

Concept understanding — Preparation of Phenols

Q.Benzene is treated with Oleum to give [A], which is then treated with

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