Phenol is manufactured from cumene (isopropylbenzene). Which compound is obtained as a by-product in this process?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Acetone
In the cumene process, cumene is first oxidised by air to cumene hydroperoxide. Dilute acid then splits the hydroperoxide into phenol and acetone:
\( \displaystyle \ce{C6H5CH(CH3)2} \xrightarrow{\ce{O2}\text{ (air)}} \ce{C6H5C(CH3)2OOH} \xrightarrow{\ce{H+}/\ce{H2O}} \ce{C6H5OH + CH3COCH3} \)
The six carbons of the ring stay in phenol, and the three side-chain carbons leave as acetone. Large amounts of acetone are obtained this way.
NCERT (2026-27 edition):
7.4.2 Preparation of Phenols – “Phenol is manufactured from the hydrocarbon, cumene. Cumene (isopropylbenzene) is oxidised in the presence of air to cumene hydroperoxide. It is converted to phenol and acetone by treating it with dilute acid. Acetone, a by-product of this reaction, is also obtained in large quantities by this method.”