In the following reaction, two products X and Y are formed: $\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{OH}\underset{\text{conc. }\mathrm{H}{}_2\mathrm{SO}{}_4}{\overset{\text{conc. }\mathrm{HNO}{}_3}{\to }}\mathrm{X}+\mathrm{Y}$ where X and Y are $o$-nitrophenol and $p$-nitrophenol. The suitable method that can be used for the separation of products X and Y is:

Solution & Explanation

\textbf{Answer:} (A) Fractional distillation \textbf{Solution:} Nitration of phenol gives a mixture of $o$-nitrophenol and $p$-nitrophenol. These differ appreciably in boiling point ($o$-nitrophenol b.p. $222{}^{\circ }$C, $p$-nitrophenol b.p. $238{}^{\circ }$C), because $o$-nitrophenol has intramolecular H-bonding (more volatile) while $p$-nitrophenol has intermolecular H-bonding (less volatile). A mixture of two liquids/low-melting solids whose boiling points differ can be separated by fractional distillation (under reduced pressure). Hence the correct method is fractional distillation.