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In organic chemistry, nitration is a general class of for the introduction of a nitro group () into an organic compound. The term also is applied incorrectly to the different process of forming () between alcohols and nitric acid (as occurs in the synthesis of nitroglycerin). The difference between the resulting molecular structures of nitro compounds and () is that the nitrogen atom in nitro compounds is directly Chemical bond to a non-oxygen atom (typically carbon or another nitrogen atom), whereas in nitrate esters (also called organic nitrates), the nitrogen is bonded to an oxygen atom that in turn usually is bonded to a carbon atom (nitrito group).
There are many major industrial applications of nitration in the strict sense; the most important by volume are for the production of nitroaromatic compounds such as nitrobenzene. The technology is long-standing and mature.* (1989). 9780471186953, VCH. ISBN 9780471186953
Nitration reactions are notably used for the production of explosives, for example the conversion of guanidine to nitroguanidine and the conversion of toluene to trinitrotoluene (TNT). Nitrations are, however, of wide importance as virtually all aromatic amines () are produced from nitro precursors. Millions of tons of nitroaromatics are produced annually.
Alternative mechanisms have also been proposed, including one involving single electron transfer (SET).
Regioselectivity is strongly affected by substituents on aromatic rings (see electrophilic aromatic substitution). For example, nitration of nitrobenzene gives all three isomers of in a ratio of 93:6:1 (respectively meta, ortho, para). Electron-withdrawing groups such as other nitro compound are deactivating. Nitration is accelerated by the presence of such as amino, Hydroxyl and methyl groups also and resulting in para and ortho isomers. In addition to regioselectivity, the degree of nitration is of interest. Fluorenone, for example, can be selectively trinitrated or tetranitrated.
The direct nitration of aniline with nitric acid and sulfuric acid, according to one source,Web resource: warren-wilson.edu results in a 50/50 mixture of para- and meta-nitroaniline isomers. In this reaction the fast-reacting and activating aniline (ArNH2) exists in equilibrium with the more abundant but less reactive (deactivated) anilinium ion (ArNH3+), which may explain this reaction product distribution. According to another source, Mechanism and synthesis Peter Taylor, Royal Society of Chemistry (Great Britain), Open University a more controlled nitration of aniline starts with the formation of acetanilide by reaction with acetic anhydride followed by the actual nitration. Because the amide is a regular activating group the products formed are the para and ortho isomers. Heating the reaction mixture is sufficient to hydrolyze the amide back to the nitrated aniline.
In the Wolffenstein–Böters reaction, benzene reacts with nitric acid and mercury(II) nitrate to give picric acid.
In the second half of the 20th century, new reagents were developed for laboratory usage, mainly N-nitro heterocyclic compounds.
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