nitrobenzene-----(1)----->anniline------(2)---->benzene diazonium chloride--------(3)----->benzene

1)Fe/Hcl

2)NaNo2/Hcl

3)Ethanal or phosphorous acid

nitrobenzene--->aniline-->benzene diazonium chloride--->benzene

1) Zn/HCl 2) NaNO3/HCl  3) steam

1) Nitrobenzene to aniline by reduction with metal and acid ( Fe,Zn,Sn + HCl)

2) Aniline to benzene diazonium chloride by reaction with NaNO2+HCl at 273-278K.

3) Deamination of diazonium salt with hypophorous acid (H3PO2) at room temp. in presence of Cu+ salt as a catalyst gives benzene.