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The Nitration of Benzene

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  • Page ID
    3768
  • This page gives you the facts and a simple, uncluttered mechanism for the electrophilic substitution reaction between benzene and a mixture of concentrated nitric acid and concentrated sulfuric acid.

    The electrophilic substitution reaction between benzene and nitric acid

    Benzene is treated with a mixture of concentrated nitric acid and concentrated sulfuric acid at a temperature not exceeding 50°C. As temperature increases there is a greater chance of getting more than one nitro group, -NO2, substituted onto the ring. Nitrobenzene is formed:

    \[ C_6H_6 + HNO_3 \rightarrow C_6H_5NO_2 + H_2O\]

    or:

    The concentrated sulfuric acid is acting as a catalyst.

    The formation of the electrophile

    The electrophile is the "nitronium ion" or the "nitryl cation", \(NO_2^+\). This is formed by reaction between the nitric acid and the sulphuric acid.

    \[ HNO_3 + 2H_2SO_4 \rightarrow NO_2^+ 2HSO_4^- + H_3O^+\]

    The electrophilic substitution mechanism

    Stage one

    Stage two

     

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