NITRO-CELLULOSE POWDER: see GUNCOTTON. NITRO-CELLULOSE SILK: see SILK, ARTIFICIAL. NITRO-COMPOUNDS, in organic chemistry, compounds containing the univalent radical directly combined with carbon.
Aromatic most important pounds are those of the aromatic series derived from benzene, toluene, xylene and naphthalene, since they find extensive use either in the manufacture of synthetic dyes (q.v.) or in the pro duction of high explosives. (See articles under EXPLOSIVES and T.N.T.) These aromatic nitro-compounds are manufactured by the direct action of nitric acid on the hydrocarbon, this re action being generally carried out in the presence of concentrated sulphuric acid which absorbs the water formed during nitration.
In this way benzene can be nitrated in three stages to furnish nitrobenzene (q.v.), I :3-dinitrobenzene and I : 3 : 5-trinitroben zene. Toluene gives rise to ortho- and para-nitrotoluene with a small amount of meta-nitrotoluene. (See CHEMISTRY : Organic.) These three isomeric nitro-toluenes undergo further nitration yielding various di- and tri-nitrotoluenes. Of these higher nitra tion products the most important is 2:4 :6-trinitrotoluene or T.N.T.
Naphthalene on nitration yields almost exclusively a-nitro naphthalene, and energetic nitration of this product gives I :5 and I :8-dinitronaphthalenes. These dinitro-compounds and their higher nitration products have been utilised in explosives. (See also NAPHTHALENE.) Nitrobenzene (q.v.) and ortho-nitrotoluene (m.p. 10.5° C, b.p. 218° C) are pale yellow oils distilling without decomposition and having characteristic odours (artificial oil of mirbane) re calling that of oil of bitter almonds. Para-nitrotoluene melts at C and boils at 230° C.
These nitro-compounds yield on reduction in acid media the aromatic amines, nitrobenzene giving aniline and the nitrotoluenes furnishing the corresponding toluidines. In alkaline media the reduction leads successively to azoxy-, azo- and hydrazo-com pounds. Thus nitrobenzene passes successively into azoxybenzene, azobenzene and hydrazobenzene. The last of these on treatment with acid changes into benzidine (q.v.). This series of chemical changes constitutes an important use for nitrobenzene, and in a similar manner ortho-nitrotoluene is employed in the manufacture of tolidine, a valuable colour intermediate.
The aromatic dinitro-compounds are also reducible to aro matic bases, I :3-dinitrobenzene giving metaphenylenediamine, and 2 :4-dinitrotoluene giving 2 :4-tolylenediamine. Both these dia mines are used in colour making. The partial reduction of :3 dinitrobenzene with sodium disulphide gives metanitroaniline, NO2.C6114.NH2, this base being useful in the colour industry and also in the production of an exceptionally powerful high explosive, tetranitroaniline or T.N.A., C6H(NO2)4.NH2. Nitrobenzene re duced in neutral solution furnishes 13-phenylhydroxylamine, and this is readily transformed to para-aminophenol, which is both a colour intermediate and a photographic developer ("Rodinal").
The aromatic nitro-compounds are employed as oxidising agents. Nitrobenzene or ortho-nitrotoluene is employed with a ferrous chloride catalyst to oxidise a mixture of aniline and toluidine in the manufacture of magenta. Nitrobenzene and its
homologues are also used as the oxidising agent in the Skraup reaction for quinoline and allied bases.
Aliphatic Nitro-conrpounds (Nitro-paraffins).—In this series the nitro-group is attached directly to an alkyl radical. These aliphatic nitro-compounds are chiefly of academic interest but they are also useful in the diagnosis of the various types of alcohols (q.v.). They are prepared by the action of alkyl iodides on silver nitrite (V. Meyer, 1874). They are also produced by the action of sodium nitrite on the a-halogenated fatty acids; the a-nitro- fatty acids first formed readily lose carbon dioxide and yield the nitro-paraffin (H. Kolbe, 1872).
Among the higher paraffins, for example normal hexane and octane, nitro-paraffins are obtainable by direct nitration as in the aromatic series (M. Konowalow, 1892; R. A. Worstall, 1898). The nitro-paraffins are colourless, fragrant liquids distilling with out decomposition. Primary and secondary aliphatic nitro-com pounds containing respectively the groups and >CH.NO2 form Metallic derivatives, for example sodium salts, which according to A. Hantzsch are derived from the isomeric iso-nitro-compounds, R :NO.OH. This variety is the truly acidic form and the ordinary primary and secondary nitro-paraffins are to be regarded as pseudo-acids. The reactions of the nitro-paraf fins with nitrous acid are characteristic and utilisable in discrimi nating between primary, secondary and tertiary alcohols (V. Meyer, 1875). The alcohols are converted successively into iodides and nitro-paraffins. The primary paraffin yields a colour less nitrolic acid, R.C(NOH).NO, which forms a red alkali salt; the secondary paraffin gives a blue pseudonitrole, whereas the tertiary nitro-paraffin, is not acted on by nitrous acid and no colour effect is observed.
The nitro-paraffins are reduced by stannous chloride to 13-alkylhydroxylamines and thence to aliphatic amines.
Nitromethane, a colourless oil boiling at tot° C, is obtained by the action of methyl-iodide on silver nitrite.
Chloropicrin, a substance employed in chemical warfare (q.v.), is a liquid of suffocating odour, boils at 112° C, and is obtained by the action of calcium chlorohypochlorite (chloride of lime) on picric acid.
Phenylnitromethane, an interesting example of a nitro-compound of mixed aliphatic-aromatic type and isomeric with the nitrotoluenes (v. supra), prepared by the action of benzyl chloride on silver nitrite, is a colourless oily liquid boiling at C and somewhat soluble in water. It does not give a coloration with ferric chloride. It forms a sodium salt, how ever, from the aqueous solution of which mineral acid precipitates a solid isomeric form of phenylnitromethane melting at 84° C. This solid form gradually passes into the oily variety. The solid isomeride gives a reddish-brown coloration with ferric chloride and reacts with other reagents which serve to identify the hy droxyl group. Hence it is to be regarded as the aci-form of phenyl-nitromethane having the constitution and its existence affords support to Hantzsch's theory that the ordinary primary and secondary aliphatic nitro-compounds are pseudo-acids. (G. T. M.)