Nitrointi

Nitrointi (nitration) is a chemical reaction that introduces a nitro group (-NO2) into an organic molecule. The most common route for aromatic substrates is electrophilic aromatic substitution, in which the nitronium ion (NO2+) generated from a mixture of concentrated nitric acid and sulfuric acid attacks the substrate to form nitroarene derivatives. For aliphatic substrates, nitration can proceed via nitronium salts or strongly acidic systems, producing nitroalkanes or nitroesters under controlled conditions.

Industrial nitrations typically employ a mixed acid system of sulfuric and nitric acids, with reaction temperatures carefully controlled, often near 0 to 5 °C for arenes, to moderate the exotherm and limit poly-nitration or rearrangements. The choice of substrate and reaction conditions determines regioselectivity and the degree of nitration, yielding compounds such as nitrobenzene, nitrotoluenes, and nitrobenzoic derivatives.

Nitro compounds have wide applications as intermediates in the manufacture of dyes, pigments, pharmaceuticals, agrochemicals, and energetic materials. A well-known sequence is the nitration of toluene to form dinitrotoluenes, followed by further nitration to trinitrotoluene (TNT). Nitrobenzene itself is a common chemical feedstock for aniline production and other syntheses.

Safety and environmental aspects are important: nitration is highly exothermic and can lead to runaway reactions if not properly cooled; it generates corrosive acidic waste and nitrogen oxides, requiring appropriate containment, ventilation, and waste treatment.