Nitro compound

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Nitro compounds are organic compounds that contain one or more nitro functional groups (-Template:NitrogenO₂). They are often highly explosive; various impurities or improper handling can easily trigger a violent exothermic decomposition.

Aromatic nitro compounds are typically synthesized by the action of a mixture of nitric and sulfuric acids on a suitable organic molecule. Some examples of such compounds are trinitrophenol (picric acid), trinitrotoluene (TNT), and trinitroresorcinol (styphnic acid).

Preparation

In organic synthesis various methods exists to prepare nitro compounds.

Aliphatic nitro compounds

• Nitromethane adds to aldehydes in 1,2-addition in the nitroaldol reaction
• Nitromethane adds to alpha-Beta unsaturated carbonyl compounds as a 1,4-addition in the Michael reaction as a Michael donor
• Nitroethylene is a Michael acceptor in a Michael reaction with enolate compounds
• In nucleophilic aliphatic substitution sodium nitrite (NaNO₂) replaces an alkyl halide. In the so-called ter Meer reaction (1876)

^[1] the reactant is a 1,1-halonitroalkane:

Image:Ter Meer reaction.png

In one study, a reaction mechanism is proposed in which in the first slow step a proton is abstracted from nitroalkane 1 to a carbanion 2 followed by isomerization to a sodium nitronate 3 and finally nucleophilic displacement of chlorine based on an experimentally observed kinetic isotope effect of 3.3 ^[2]. When the same reactant is reacted with potassium hydroxide the reaction product is the 1,2-dinitro dimer ^[3]

Aromatic nitro compounds

• In electrophilic substitution nitric acid reacts with aromatic compounds in nitration
• A classic method starting from halogenated phenols is the Zinke nitration

Reactions

Nitro compounds participate in several organic reactions.

Aliphatic nitro compounds

• Aliphatic nitro compounds are reduced to amines with hydrochloric acid and an iron catalyst
• Nitronates form by adding acids to nitro salts.
• Hydrolysis of the salts of nitro compounds yield aldehydes or ketones in the Nef reaction

Aromatic nitro compounds

• Reduction of aromatic nitro compounds with hydrogen gas over a platinum catalyst gives anilines.
• The presence of nitro groups facilitates nucleophilic aromatic substitution.

See also

• Functional group
• Reduction of nitro compounds

References

1. ↑ Edm. ter Meer (1876). "Ueber Dinitroverbindungen der Fettreihe". Justus Liebigs Annalen der Chemie 181 (1): 1 - 22. doi:10.1002/jlac.18761810102.
2. ↑ aci-Nitroalkanes. I. The Mechanism of the ter Meer Reaction M. Frederick Hawthorne J. Am. Chem. Soc.; 1956; 78(19) pp 4980 - 4984; doi:10.1021/ja01600a048
3. ↑ 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)

v • d • e Functional groups

Chemical class: Alcohol • Aldehyde • Alkane • Alkene • Alkyne • Amide • Amine • Azo compound • Benzene derivative • Carboxylic acid • Cyanate • Disulfide • Ester • Ether • Haloalkane • Hydrazone • Imine • Isocyanide • Isocyanate • Ketone • Oxime • Nitrile • Nitro compound • Nitroso compound • Peroxide • Phosphoric acid • Pyridine derivative • Sulfone • Sulfonic acid • Sulfoxide • Thioester • Thioether • Thiol

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