Aromatic nitro compounds are typically synthesized by nitration. Nitration is achieved using a mixture of
nitric acid and
sulfuric acid, which produce the
nitronium ion (NO+2), which is the electrophile:
+
H+
The nitration product produced on the largest scale, by far, is
nitrobenzene. Many explosives are produced by nitration including
trinitrophenol (picric acid),
trinitrotoluene (TNT), and
trinitroresorcinol (styphnic acid).[3]
Another but more specialized method for making aryl–NO2 group starts from halogenated phenols, is the
Zinke nitration.
Preparation of aliphatic nitro compounds
Aliphatic nitro compounds can be synthesized by various methods; notable examples include:
Despite the occasional use in pharmaceuticals, the nitro group is associated with
mutagenicity and
genotoxicity and therefore is often regarded as a liability in the
drug discovery process.[20]
Reactions
Nitro compounds participate in several
organic reactions, the most important being their
reduction to the corresponding amines:
Nitronates are also key intermediates in the
Nef reaction: when exposed to acids or oxidants, a nitronate hydrolyzes to a
carbonyl and
azanone.[25]
Grignard reagents combine with nitro compounds to give a
nitrone; but a Grignard reagent with an α hydrogen will then add again to the nitrone to give a
hydroxylamine salt.[26]
Many
flavin-dependent
enzymes are capable of oxidizing aliphatic nitro compounds to less-toxic aldehydes and ketones.
Nitroalkane oxidase and 3-nitropropionate oxidase oxidize aliphatic nitro compounds exclusively, whereas other enzymes such as
glucose oxidase have other physiological substrates.[27]
Explosions
Explosive decomposition of organo nitro compounds are redox reactions, wherein both the oxidant (nitro group) and the fuel (hydrocarbon substituent) are bound within the same molecule. The explosion process generates heat by forming highly stable products including molecular
nitrogen (N2), carbon dioxide, and water. The explosive power of this redox reaction is enhanced because these stable products are gases at mild temperatures. Many
contact explosives contain the nitro group.
^Henry Feuer, ed. (1970). Nitro and Nitroso Groups: Part 2, Volume 2. PATAI'S Chemistry of Functional Groups. Vol. 2. John Wiley & Sons Ltd.
doi:
10.1002/9780470771174.
ISBN978-0-470-77117-4.Saul Patai, ed. (1982). Nitro and Nitroso Groups: Supplement F: Part 2, Volume 2. PATAI'S Chemistry of Functional Groups. John Wiley & Sons Ltd.
doi:
10.1002/9780470771679.
ISBN978-0-470-77167-9.Saul Patai, ed. (1982). Amino, Nitroso and Nitro Compounds and Their Derivatives: Supplement F: Part 1, Volume 1. PATAI'S Chemistry of Functional Groups. John Wiley & Sons Ltd.
doi:
10.1002/9780470771662.
ISBN978-0-470-77166-2.
^Olga V. Dorofeeva; Yuriy V. Vishnevskiy; Natalja Vogt; Jürgen Vogt; Lyudmila V. Khristenko; Sergey V. Krasnoshchekov; Igor F. Shishkov; István Hargittai; Lev V. Vilkov (2007). "Molecular Structure and Conformation of Nitrobenzene Reinvestigated by Combined Analysis of Gas-Phase Electron Diffraction, Rotational Constants, and Theoretical Calculations". Structural Chemistry. 18 (6): 739–753.
doi:
10.1007/s11224-007-9186-6.
S2CID98746905.
^Weygand, Conrad (1972). Hilgetag, G.; Martini, A. (eds.). Weygand/Hilgetag Preparative Organic Chemistry (4th ed.). New York: John Wiley & Sons, Inc. p. 1007.
ISBN978-0-471-93749-4.
^Hawthorne, M. Frederick (1956). "Aci-Nitroalkanes. I. The Mechanism of the ter Meer Reaction1". Journal of the American Chemical Society. 78 (19): 4980–4984.
doi:
10.1021/ja01600a048.
^3-Hexene, 3,4-dinitro- D. E. Bisgrove, J. F. Brown, Jr., and L. B. Clapp. Organic Syntheses, Coll. Vol. 4, p. 372 (1963); Vol. 37, p. 23 (1957). (
Article)
^Zocher, Georg; Winkler, Robert; Hertweck, Christian; Schulz, Georg E (2007). "Structure and Action of the N-oxygenase AurF from Streptomyces thioluteus". Journal of Molecular Biology. 373 (1): 65–74.
doi:
10.1016/j.jmb.2007.06.014.
PMID17765264.
^Bordwell, Frederick G; Satish, A. V (1994). "Is Resonance Important in Determining the Acidities of Weak Acids or the Homolytic Bond Dissociation Enthalpies (BDEs) of Their Acidic H-A Bonds?". Journal of the American Chemical Society. 116 (20): 8885.
doi:
10.1021/ja00099a004.
^Ranganathan, Darshan; Rao, Bhushan; Ranganathan, Subramania; Mehrotra, Ashok & Iyengar, Radha (1980). "Nitroethylene: a stable, clean, and reactive agent for organic synthesis". The Journal of Organic Chemistry. 45 (7): 1185–1189.
doi:
10.1021/jo01295a003.
^Jubert, Carole & Knochel, Paul (1992). "Preparation of polyfunctional nitro olefins and nitroalkanes using the copper-zinc reagents RCu(CN)ZnI". The Journal of Organic Chemistry. 57 (20): 5431–5438.
doi:
10.1021/jo00046a027.
^Bartoli, Giuseppe; Marcantoni, Enrico; Petrini, Marino (1992) [14 Apr 1992]. "Nitrones from addition of benzyl and allyl Grignard reagents to alkyl nitro compounds: chemo-, regio-, and stereoselectivity of the reaction". Journal of Organic Chemistry. 57 (22). American Chemical Society: 5834–5840.
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10.1021/jo00048a012.