Nitro compound

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Nitro compounds are organic compounds that contain one or more nitro functional groups (-N O₂). 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).

1 Preparation
- 1.1 Aliphatic nitro compounds
- 1.2 Aromatic nitro compounds
2 Reactions
- 2.1 Aliphatic nitro compounds
- 2.2 Aromatic nitro compounds
3 See also
4 References

[edit] Preparation

In organic synthesis various methods exists to prepare nitro compounds.

[edit] 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) <ref>E ter Meer, Ann , 181, 4 (1876)</ref> 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 <ref>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</ref>. When the same reactant is reacted with potassium hydroxide the reaction product is the 1,2-dinitro dimer <ref>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)</ref>

[edit] 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

[edit] Reactions

Nitro compounds participate in several organic reactions.

[edit] 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

[edit] 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.