Nitro compounds, detection nitration

Nitro compounds and their reduction products. Tertiary nitro compounds (these are generally aromatic) are reduced by zinc and ammonium chloride solution to the corresponding hydroxylamines, which may be detected by their reducing action upon an ammoniacal solution of silver nitrate or Tollen s reagent ... 

Fig. 21 Reaction scheme for the detection of aromatics, by means of the reaction sequence, nitration, reduction, diazotization and coupling to an azo dye, and of aliphatic nitro compounds by detection of the primary amino group produced on reduction.

At sufficiently high temperatures, the detector also responds to a variety of nitroaro-matics and to (V-nitrosodimethylamine. NOz yields of 0.70 and 0.90 were obtained for 2,4-DNT and TNT, respectively. The detection system exhibits a linear response for all nitrogen-containing compounds studied, and the detection limit for the determination of organic nitrates was found to be 0.05pmol. The relative response factors for aromatic nitro compounds and nitrosamine for the pyrolyser/luminol detector are presented in Table 3. 

The molecular ion is frequently not detectable in aliphatic alcohols, nitrites, nitrates, nitro compounds, nitriles and in highly branched compounds. 

It is advisable to determine the presence of white compound in the products of nitration of toluene. It is also advised 65 to use the TIC technique on silica-gel the solution of nitro compounds in acetone is put on the staitiitg line and Ihe chromatogram is developed with vapours of benzcne-acctonc -meth-anol dioxane (50 5 30 15 vol.%.)- The chromatogram is treated with ethylene diamine solution in acetone (50/50). White compound can be detected as a magenta coloured spot of Hr = 0.6S. (Nitro derivatives give a reddish-brown coloured spot at Hf= 0.80). 

In a limited number of substances containing nitrogen, the presence of the latter may be proved by heating the substance with an excess of pulverised soda-lime in a test-tube with a Bunsen flame this causes decomposition with evolution of ammonia, which is detected by its odour or by means of a black colour imparted to a piece of filter-paper moistened with a solution of mercurous nitrate. Nitro-compounds, eg., do not give this reaction. 

An attempt to detect the aryne 542 from the in situ diazotization of the amino acid 543 with isoamyl nitrite in the presence of furan (146a) or tetracyclone (151) failed to yield any of the aryne adducts 544 or 545, respectively. The only identifiable products isolated in low yield were the acids 546 and 547 and their corresponding nitro compounds 548 and 549. Although it was considered that the latter two compounds might arise via the unlikely dipolar form (542b) of the aryne, it was demonstrated that they were actually transformation products of the former two compounds, 546 and 547, under the diazotization conditions. Similar decarboxylative nitrations with isoamyl nitrite and nitric acid have been observed in related systems. The acids 546 and 547 were proposed to arise from the dipolar species 550,... 

In order to form the required cyanide and cyanate radicals, the C-N structure must already be present in the molecule. Nitro compounds are detected, but not nitrate esters, ammonia or nitrogen oxides. By taking part in the alkali reaction the cyanide radical receives an electron. Cyanide ions are formed, which react with other radicals to give neutral species. The electron released provides the detector signal. 

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