Question

(X) $\xrightarrow[\text{FeBr}_3]{\text{Br}_2}$ (i) $\text{NaOH}$, 623 K, 300 atm; (ii) dil. HCl $\xrightarrow{\text{HNO}_3}$ A + B. The organic product (A) and (B) can be separated by :

• A. Steam distillation
• B. Fractional distillation
• C. Distillation under reduced pressure
• D. Azeotropic distillation

Hint:

Differences in volatility due to H-bonding type (Intra vs Inter) allow separation of ortho and para isomers of nitrophenols and hydroxybenzaldehydes via steam distillation.

Answer 1

The Correct Option is A

Step 1: Benzene (X) is brominated to Bromobenzene.
Step 2: Bromobenzene is converted to Phenol (Dow's Process condition).
Step 3: Phenol is nitrated to give o-Nitrophenol (A) and p-Nitrophenol (B).
Separation Principle:
o-Nitrophenol forms Intramolecular Hydrogen Bonds (Chelation), lowering its boiling point and making it steam volatile.
p-Nitrophenol forms Intermolecular Hydrogen Bonds (Association), increasing its boiling point and making it non-volatile in steam.
The mixture is separated by Steam Distillation.