Carboxylic Acids and their Derivatives 2 Question 17
17. Identify the binary mixture(s) that can be separated into individual compounds, by differential extraction, as shown in the given scheme.
(2012)
| Binary mixture containing Compound 1 and Compound 2 |
$\mathrm{NaOH}(a q)$ |
|---|---|
| Compound 1 | + Compound 2 |
| Compound 1 | + Compound 2 |
(a) $\mathrm{C}{6} \mathrm{H}{5} \mathrm{OH}$ and $\mathrm{C}{6} \mathrm{H}{5} \mathrm{COOH}$
(b) $\mathrm{C}{6} \mathrm{H}{5} \mathrm{COOH}$ and $\mathrm{C}{6} \mathrm{H}{5} \mathrm{CH}_{2} \mathrm{OH}$
(c) $\mathrm{C}{6} \mathrm{H}{5} \mathrm{CH}{2} \mathrm{OH}$ and $\mathrm{C}{6} \mathrm{H}_{5} \mathrm{OH}$
(d) $\mathrm{C}{6} \mathrm{H}{5} \mathrm{CH}{2} \mathrm{OH}$ and $\mathrm{C}{6} \mathrm{H}{5} \mathrm{CH}{2} \mathrm{COOH}$
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Answer:
Correct Answer: 17. (d)
Solution:
- For separation by differential extraction one of the component must form salt with the given base so that the salt will be extracted in aqueous layer leaving other component in organic layer.
(a) Both phenol and benzoic acid forms salt with $\mathrm{NaOH}$, hence this mixture can’t be separated.
(b) Benzoic acid forms salt with $\mathrm{NaOH}$ while benzyl alcohol does not, hence the mixture can be separated using $\mathrm{NaOH}$. Also benzoic acid forms salt with $\mathrm{NaHCO}{3}$ but benzyl alcohol does not, hence $\mathrm{NaHCO}{3}$ can be used for separation.
(c) Neither benzyl alcohol nor phenol forms salt with $\mathrm{NaHCO}{3}$, mixture cannot be separated using $\mathrm{NaHCO}{3}$.
(d) $\mathrm{C}{6} \mathrm{H}{5} \mathrm{CH}{2} \mathrm{COOH}$ forms salt with $\mathrm{NaOH}, \mathrm{C}{6} \mathrm{H}{5} \mathrm{CH}{2} \mathrm{OH}$ does not, hence mixture can be separated using $\mathrm{NaOH}$. $\mathrm{C}{6} \mathrm{H}{5} \mathrm{CH}{2} \mathrm{COOH}$ forms salt with $\mathrm{NaHCO}{3} . \mathrm{C}{6} \mathrm{H}{5} \mathrm{CH}{2} \mathrm{OH}$ does not, hence mixture can be separated using $\mathrm{NaHCO}{3}$.
