products of the replacement of hydrogen atoms in the aniline ring, C6H5NH2, by nitro groups, —NO2. They may contain one to five nitro groups.
The meta-, ortho-, and para- isomers of mononitroanilines have industrial significance. They are yellow crystalline compounds that melt at 114.0°, 71.0°, and 147.0°C, respectively, and are poorly soluble in water but readily soluble in organic solvents. The ortho- and para- isomers are weak bases and are less soluble in acids than the meta- isomer, which is a stronger base. Upon heating with aqueous alkaline solutions, the NH2 groups in o-nitroaniline and p-nitroaniline are replaced by OH groups with the formation of nitrophenols.
Nitroanilines with more than one nitro group are explosive. In industry, o-nitroaniline and p-nitroaniline are obtained by heating the corresponding nitrochlorobenzenes with ammonia; m-nitroaniline is produced by partial reduction of m-dinitroben-zene with sodium sulfide. Nitroanilines are blood poisons, and the combined action of nitroanilines and ethyl alcohol is particularly dangerous. Nitroanilines are intermediates in the production of azo dyes and a number of drugs.