Electrophilic Substitution and the Nitration of Benzene
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. If you want the nitration mechanism explained to you in detail, there is a link at the bottom of the page.
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.
The concentrated sulfuric acid is acting as a catalyst.
The Formation of the Electrophile
The electrophile is the "nitronium ion" or the "nitryl cation", NO2+. This is formed by reaction between the nitric acid and the sulfuric acid.