Question

A solution of m-chloroaniline, m-chlorophenol and m-chlorobenzoic acid in ethyl acetate was extracted initially with a saturated solution of ${\mathrm{NaHCO}}_3$to give fraction A. The leftover organic phase was extracted with dil. $\mathrm{NaOH}$ solution to give fraction B. The final organic layer was labelled as fraction C. Fractions A, B and C, contain respectively-

• A. $\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid},\mathrm{m}-\mathrm{chlorophenol},\mathrm{m}-\mathrm{chloroaniline}$
• B. $\mathrm{m}-\mathrm{chlorophenol},\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid},\mathrm{m}-\mathrm{chloroaniline}$
• C. $\mathrm{m}-\mathrm{chloroaniline},\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid},\mathrm{m}-\mathrm{chlorophenol}$
• D. $\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid},\mathrm{m}-\mathrm{chloroaniline},\mathrm{m}-\mathrm{chlorophenol}$

Answer 1

The correct option is A

$\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid},\mathrm{m}-\mathrm{chlorophenol},\mathrm{m}-\mathrm{chloroaniline}$

1. In this question, an acid-base reaction is taking place. ${\mathrm{NaHCO}}_3$ is a weak acid and $\mathrm{NaOH}$ is a strong acid. Likewise, $\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid}$ is a strong acid, $\mathrm{m}-\mathrm{chlorophenol}$ is a weak acid and $\mathrm{m}-\mathrm{chloroaniline}$ is not at all acidic in nature.
2. ${\mathrm{NaHCO}}_3$ is a weak base and it will give a reaction only with the strong base available in the solution which is $\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid}$. When the solution is first extracted with ${\mathrm{NaHCO}}_3$, it reacts with $\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid}$ in the solution leaving behind the other two compounds i.e $\mathrm{m}-\mathrm{chloroaniline}$ and $\mathrm{m}-\mathrm{chlorophenol}$ in the solution. So, fraction A contains $\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid}$.
3. $\mathrm{NaOH}$ is a strong base and it gives acid-base reaction with phenolic compounds (phenolic compounds are little acidic in nature). In the second step when the solution is extracted with $\mathrm{NaOH}$, it will react with m-chlorophenol in the solution leaving behind the other compound. So, fraction B contains $\mathrm{m}-\mathrm{chlorophenol}$.
4. The final organic layer which is labelled as C contains $\mathrm{m}-\mathrm{chloroaniline}$.
5. The reactions are given below

Fractions A, B, and C, contain - $\mathrm{m}-\mathrm{chlorobenzoic}\mathrm{acid}$, $\mathrm{m}-\mathrm{chlorophenol}$ and $\mathrm{m}-\mathrm{chloroaniline}$ respectively.

Hence, option A is the correct answer.