Nitro Compounds

(redirected from Nitro compound)
Also found in: Dictionary, Thesaurus, Wikipedia.

Nitro Compounds

 

organic compounds containing one or more nitro groups, —NO2, bound to carbon atoms. A distinction is made among mono-, di-, tri-, and poly-nitro compounds.

Nitro compounds may be aliphatic (nitroparaffins and ni-troolefins); aromatic, containing nitro groups in the aromatic ring (for example, nitroanilines, nitrobenzene, nitrotoluenes, and nitronaphthalene); and aliphatic-aromatic compounds, containing nitro groups only in the aliphatic side chain (for example, phenylnitromethane, C6H5CH2NO2, and nitrostyrene, C6H5-CH—CHNO2), as well as compounds with nitro groups in the side chain and the aromatic ring, such as p-nitrophenylnitro-methane, O2NC6H4CH2NO2.

The aromatic nitro compounds are yellowish liquids or crystalline compounds that dissolve readily in organic solvents and poorly in water. They are synthesized in industry and under laboratory conditions by nitration of aromatic compounds by nitrating mixtures. Aromatic polynitro compounds are used as explosives (trinitrotoluene, the ammonium salt of trinitrophenol [picrates], and trinitrophenylmethylnitramine). The reduction of nitro groups leads to aromatic amines, which are intermediates in the production of various dyes.

Aliphatic nitro compounds are produced in industry mainly by the nitration of paraffins by nitric acid or nitrogen oxides. The simplest mononitroparaffins are colorless liquids with a characteristic odor. Nitroparaffins reduce readily, with the formation of hydroxylamines and amines. The action of bases on primary and secondary nitro compounds leads to the formation of salts of the aci form of nitro compounds, which are called isonitro compounds (I) and are readily converted into aldehydes or ketones (II):

where R is an alkyl group and Rʹ is a hydrogen atom or alkyl group.

Treatment of the salts of nitro compounds (III)—and, in some cases, the nitro compounds themselves or their aci forms—with alkylating agents can produce O-alkylation, with the formation of nitronic acid esters (IV):

or C-alkylation:

where X is a halogen atom. The direction of the reaction depends both on the structure of the salt and on the nature of the alkylating agent.

The action of concentrated acids on nitro compounds leads to the formation of carboxylic acids. Aliphatic nitro compounds are readily condensed with aldehydes and ketones, with the formation of nitroalcohols, which may be dehydrated to give ni-troolefins. These reactions are widely used in laboratory practice. Nitroparaffins readily dissolve various organic compounds.

Some nitro compounds have toxic properties and may injure the liver or, sometimes, the eyes (cataracts).

REFERENCES

Khimiia nitro- i nitrozogrupp. Edited by H. Feuer. Moscow, 1972. (Translated from English.)
Topchiev, A. V. Nitrovanie uglevodorodov i drugikh organicheskikh so-edinenii, 2nd ed. Moscow, 1956.
Orlova, E. Iu. Khimiia i tekhnologiia brizantnykh vzryvchatykh ve-shchestv, 2nd ed. Leningrad, 1973.

M. M. KRAIUSHKIN

References in periodicals archive ?
In line with the outlined strategies, herein, we wish to introduce an easy, efficient and practical protocol for solvent-free reduction of various aromatic and aliphatic nitro compounds to the corresponding amines with NaBH4 in the presence of bis-thiourea complexes of bivalent cobalt, nickel, copper and zinc chlorides at room temperature (Scheme 1).
A literature review shows that though the application of NaBH4 in the presence of various Lewis acids or promoters has been used for reduction of nitro compounds to amines, however, the combination system of bis-thiourea complexes of bivalent transition metal chlorides with NaBH4 has not been investigated yet.
This subject and continuation of our research program directed to the development of new protocols for NaBH4 reduction of nitro compounds [18,21,23,26-29] encouraged us to investigate the facility of NaBH4/MII(tu)2Cl2 systems (M: Co, Ni, Cu and Zn) for the titled transformation.
The scope and generality of this synthetic protocol was then studied through the reduction of structurally different aromatic nitro compounds at the optimized conditions.
Reducing capability of NaBH4/MII(tu)2Cl2 system towards aliphatic nitro compounds was also studied by the reduction of 1-nitrohexane and 2-nitroheptane at the optimized reaction conditions.
High yields, easy work-up procedure, ability to reduce aromatic and aliphatic nitro compounds as well as the benefits of using solvent- free conditions are the significant advantages that make this protocol a synthetically useful addition to the present methodologies.
Weiguny, A Review of the Selective Catalytic Reduction of Aromatic Nitro Compounds into Aromatic Amines, Isocyanates, Carbamates, and Ureas Using CO, Chem.
Reduction of Aromatic Nitro Compounds with the Sodium Borohydride-Nickelous Chloride System, Chem.
Ganem, Rapid and Efficient Reduction of Aliphatic Nitro Compounds to Amines, Tetrahedron Lett.
Iyengar, Reductions Using ZrCl4/NaBH4: A Novel and Efficient Conversion of Aromatic, Aliphatic Nitro Compounds to Primary Amines, Synlett, 683 (2000).
Ooi, Selective Reduction of Aromatic Nitro Compounds with Sodium Borohydride-Stannous Chloride, Chem.
Ghasemi, A Mild and Convenient Reduction of Nitro Compounds with NaBH4/SbF3 System in Wet CH3CN, J.