NEET 2017 · ChemistryPrevious Year Question
The most suitable method of separation of a mixture of ortho- and para-nitrophenols is
Answer: (D) (D) Steam distillation. \textbf{Answer:} (D) Steam distillation \textbf{Solution:} In o-nitrophenol the and groups are adjacent, allowing \emph{intramolecular} hydrogen bonding (chelation).
- A.(A) Sublimation
- B.(B) Chromatography
- C.(C) Crystallisation
- D.(D) Steam distillation✓
Correct Answer
(D) (D) Steam distillation
Solution & Explanation
\textbf{Answer:} (D) Steam distillation \textbf{Solution:} In o-nitrophenol the and groups are adjacent, allowing \emph{intramolecular} hydrogen bonding (chelation). This makes it volatile and steam-volatile. In p-nitrophenol the groups are far apart, so it forms \emph{intermolecular} hydrogen bonds, making it less volatile (higher boiling, not steam-volatile). Hence steam distillation carries over o-nitrophenol while p-nitrophenol remains, separating the mixture.
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