Nitration occurs with aromatic organic compounds via an electrophilic substitution mechanism involving the attack of the electron-rich benzene ring by the nitryl (nitronium) cation.
Benzene is nitrated by refluxing with concentrated sulfuric acid and concentrated nitric acid at 50°C.
(1) 2H2SO4 + HNO3 ---> 2HSO42- + NO2+ + H3O+
(2) C6H6 + NO2+ ---> C6H5NO2 + H+
(3) H+ + H3O+ + 2HSO42- ---> H2O + 2H2SO4
The sulfuric acid is regenerated and hence acts as a catalyst.
