Which of the following compounds will react with sodium hydroxide solution in water?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → C6H5OH
An –OH compound reacts with aqueous NaOH only if it is a stronger acid than water. Phenol is: its –OH is on an sp2 carbon of the benzene ring, and the phenoxide ion is stabilised by resonance. Phenol therefore gives up its proton to the hydroxide ion:
\( \displaystyle \ce{C6H5OH + NaOH -> C6H5O^-Na^+ + H2O} \)
The product is sodium phenoxide.
Why the other options are incorrect
Option (2) C6H5CH2OH — Incorrect. In benzyl alcohol the –OH is on a \( \ce{CH2} \) group, not on the ring; it is an alcohol, a weaker acid than water.
Option (3) (CH3)3COH — Incorrect. tert-Butyl alcohol is an alcohol; its three electron-releasing methyl groups make it an even weaker acid.
Option (4) C2H5OH — Incorrect. Ethanol is a weaker acid than water, so hydroxide ion cannot take its proton; ethanol reacts with sodium metal, not with aqueous NaOH.
NCERT (2026-27 edition):
7.4.4 Chemical Reactions – “In addition to this, phenols react with aqueous sodium hydroxide to form sodium phenoxides.”
“The reaction of phenol with aqueous sodium hydroxide indicates that phenols are stronger acids than alcohols and water.”