Nitration of Phenol

Phenol gives a mixture of 2-nitro and 4-nitrophenols on nitration with dilute nitric acid.

The mixture of nitrophenols so obtained is separated using steam distillation. Both these products show hydrogen bonding. In case of 2-nitrophenol, the hydrogen bonding is intramolecular (in the same molecule) whereas in case of 4-nitrophenol, it is intermolecular(between different molecules).

2-Nitrophenol is steam volatile and distills out on passing steam whereas 4-nitrophenol is less volatile due to intermolecular hydrogen bonding.

Treatment of phenol with a mixture of conc. nitric acid and conc. sulphuric acid at 323K yields 2,4,6-trinitrophenol also known as picric acid.