Nitric acid
Precursor to organic nitrogen compounds

In organic synthesis, industrial and otherwise, the nitro group is a versatile functional group. A mixture of nitric and sulfuric acids introduces a nitro substituent onto various aromatic compounds by electrophilic aromatic substitution. Many explosives, such as TNT, are prepared this way:

Either concentrated sulfuric acid or oleum absorbs the excess water.

The nitro group can be reduced to give an amine group, allowing synthesis of aniline compounds from various nitrobenzenes:
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