Editing TNT (section)

== Preparation ==
In industry, TNT is produced in a three-step process. First, [[toluene]] is [[nitration|nitrated]] with a mixture of [[sulfuric acid|sulfuric]] and [[nitric acid]] to produce [[mononitrotoluene]] (MNT). The MNT is separated and then renitrated to [[dinitrotoluene]] (DNT). In the final step, the DNT is nitrated to trinitrotoluene (TNT) using an [[anhydrous]] mixture of nitric acid and [[oleum]]. Nitric acid is consumed by the manufacturing process, but the diluted sulfuric acid can be reconcentrated and reused.

After nitration, TNT can either be purified by crystallization from an organic solvent or stabilized by a process called sulfitation, where the crude TNT is treated with aqueous [[sodium sulfite]] solution to remove less stable isomers of TNT and other undesired reaction products.  The rinse water from sulfitation is known as [[#Pink and red water|red water]] and is a significant pollutant and waste product of TNT manufacture.<ref>{{cite book|title=Chemistry and Technology of Explosives|publisher=Pergamon Press|year=1964|isbn=978-0-08-010238-2|volume=1|pages=389–91|author=Urbanski T}}
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Control of [[nitrogen oxide]]s in feed nitric acid is very important because free [[nitrogen dioxide]] can result in oxidation of the methyl group of toluene.  This reaction is highly [[exothermic]] and carries with it the risk of a runaway reaction leading to an explosion.{{Cn|date=January 2021}}

In the laboratory, 2,4,6-trinitrotoluene is produced by a two-step process.  A nitrating mixture of concentrated nitric and sulfuric acids is used to nitrate toluene to a mixture of mono- and di-nitrotoluene isomers, with careful cooling to maintain temperature.  The nitrated toluenes are then separated, washed with dilute [[sodium bicarbonate]] to remove oxides of nitrogen, and then carefully nitrated with a mixture of [[fuming nitric acid]] and sulfuric acid.{{Cn|date=January 2021}}

[[X-ray crystallography]] determined that each of the three planar nitro groups is substantially rotated out of the plane of the benzene ring.<ref>{{cite journal |doi=10.1016/0584-8539(89)80010-8 |title=Molecular structure and vibrational analysis of 2,4,6-trinitrotoluene and 2,4,6-trinitrotoluene-α-''d''<sub>3</sub> |year=1989 |last1=Nash|first1=C.P. |last2=Nelson |first2=T.E.|last3=Stewart |first3=J.J.P. |last4=Carper |first4=W.R.|journal=[[Spectrochimica Acta Part A]] |volume=45 |issue=5 |pages=585–588|bibcode=1989AcSpA..45..585N }}</ref>