Question

$C_6{H}_6\stackrel{\left(X\right)}{\to }Ph-S{O}_{3}H\underset{\Delta }{\overset{NaOH,H^{+}}{\to }}Ph-OH$
Identify $X$ in the above reaction.

• A. Sulphuric acid
• B. Caro's acid
• C. Oleum
• D. Sulphurous acid

Answer 1

The correct option is C Oleum

Benzenesulphonic acid can be obtained from benzene by reacting it with oleum $\left(H_2{S}_2{O}_7\right)$. This benzene sulphonic acid can be treated with molten sodium hydroxide at high temperatures to encourage the formation of sodium phenoxide. Finally, sodium phenoxide on acidification gives phenol.