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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
\[\ce{NO2}\]
\[\ce{NO+}\]
\[\ce{NO^{+}2}\]
\[\ce{NO^{-}2}\]
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Solution
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.
\[\ce{H2SO4 (conc_.) -> H- + HSO^{-}4}\]
\[\ce{H+ + HNO3 -> H2NO^{+}3}\]
\[\ce{H2NO^{+}3 -> NO^{+}2 + H2O}\]
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