Question

In the nitration of benzene using a mixture of conc. \[\ce{H2SO4}\] and conc. \[\ce{HNO3}\], the species which initiates the reaction is ______.

Options

• \[\ce{NO2}\]

• \[\ce{NO+}\]

• \[\ce{NO^{+}2}\]

• \[\ce{NO^{-}2}\]

Answer 1

In the nitration of benzene using a mixture of conc. \[\ce{H2SO4}\] and conc. \[\ce{HNO3}\], the species which initiates the reaction is \[\ce{NO^{+}2}\].

Explanation:

In the process of nitration of benzene, firstly \[\ce{H2SO4}\] dissociates into \[\ce{H+}\] and \[\ce{HSO^{-}4}\]. The proton produced further reacts with \[\ce{HNO4}\] to give a positively charged complex that is unstable and dissociates into nitronium ions and water as products. The nitronium ion is an electron-deficient species i.e. electrophile that attacks the electron cloud of the benzene ring.

\[\ce{H2SO4 (conc_.) -> H- + HSO^{-}4}\]

\[\ce{H+ + HNO3 -> H2NO^{+}3}\]

\[\ce{H2NO^{+}3 -> NO^{+}2 + H2O}\]