Aryl nitro compounds are prepared by electrophilic aromatic substitution of an aryl hydrogen atoms using a mixture of nitric and sulfuric acids. The electrophile is the nitronium ion (NO2+). The substituents on the ring determine the position of the new nitro group. Multiple nitration is usually not a problem. Because the nitro group is deactivating, addition of subsequent nitro groups is much more difficult (Section 9.7B).