Laboratory preparation of nitrobenzene

Aromatic compounds can be directly nitrated using a mixture of concentrated nitric acid and sulphuric acid.

formation of nitrobenzene from benzene

formation of nitro toulene from toulene

This reaction is an example of electrophilic substitution of benzene. The electrophile is a nitronium

electrophile of nitronium

The nitronium ion attacks to the benzene ring resulting in the formation of a carbocation. Electron releasing substituents like -CH3, -OCH3, -OH, -NH2 etc activate the ring and stabilize the carbocation while electron withdrawing groups like -NO2, -CN, -SO3H, -X activate the carbocation. The nitrating mixture of conc H2SO4 and conc HNO3 con nitrate even deactivated compounds like nitrobenzene under refluxing conditions to get m-dinitrobenzene. For nitration of activated aromatic systems like phenol and then ether derivatives, even milder conditions can be used.

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