preparation of paracetamol

In a small-scale laboratory, paracetamol is prepared by a three-reaction sequence. First, nitration of phenol with sodium nitrate gives a mixture of two isomers, from which the wanted 4-nitrophenol (bp 279 °C) can easily be separated by steam distillation. In this electrophilic aromatic substitution reaction, phenol's oxygen is strongly activating, thus the reaction requires only mild conditions as compared to nitration of benzene itself. The nitro group is then reduced to an amine, giving 4-aminophenol. This reaction can be accomplished using sodium borohydride. Finally, the amine is acetylated with acetic anhydride. The industrial process is analogous, but hydrogenation is used instead of the sodium borohydride reduction.