Phenol on reaction with dilute nitric acid, gives two products. Which method will be most efficient for large scale separation?

When phenol reacts with dilute nitric acid (dilute $$HNO_3$$), it undergoes electrophilic aromatic substitution to produce a mixture of:

1. ortho-nitrophenol (2-nitrophenol)

2. para-nitrophenol (4-nitrophenol)

Key difference between the two products:

ortho-Nitrophenol has intramolecular hydrogen bonding between the $$-OH$$ group and the adjacent $$-NO_2$$ group. This reduces its ability to form intermolecular hydrogen bonds with water, making it steam-volatile (lower boiling point, less soluble in water).

para-Nitrophenol has intermolecular hydrogen bonding (the $$-OH$$ and $$-NO_2$$ groups are far apart). This makes it non-volatile with steam (higher boiling point, more soluble in water).

Separation method:

Steam distillation is the most efficient method for large-scale separation. When steam is passed through the mixture, ortho-nitrophenol (being steam-volatile) distils over with the steam, while para-nitrophenol remains behind in the residue.

The correct answer is Option B: Steam distillation.