(i) toluene → p-toluidine

Toluene is allowed to react with nitrating reagent to form p-nitrotoulene and the nitro group is further reduced to p-toluidine by Fe/HCl.

(ii) p-toluidine diazonium chloride → p-toluic acid

The chloride ion in p-toluidine diazonium chloride is replaced by –CN group in the presence of Cu⁺ ion. This reaction is called Sandmeyer reaction. The –CN group in then hydrolysed to -COOH group.