Nitration with nitric acid vapour

The nitration of aliphatic hydrocarbons may be accomplished in the vapour phase, at 410-430°C, using nitric acid vapour. A number of papers describing this method of nitration were published by Hass and co-workers [29] between 1936 and 1940. 

Under the influence of a high temperature during the reaction the hydrocarbon chain is split off to give shorter ones and such compounds as nitromethane and nitroethane are formed. For example, the authors obtained the following products in the nitration of n-pentane at 400°C  

Higher temperature enhances the formation of nitroparaflfins with shorter chains. 

This is seen clearly in Table 10, which shows the results of nitration of butane at various temperatures. 

COMPOSITION OF THE PRODUCTS OF THE BUTANE NITRATION AT VARIOUS TEMPERATURES 

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Similar conclusions have been reached by Champetier and Foex [70] and by Trombe, Foex and Champetier [71]. Wilson and Miles also studied the kinetics of nitration in nitric acid vapour. On the basis of these investigations they concluded that two molecules of nitric acid take part in the reaction with one OH group ... 

During World War II, a method of two-stage cellulose nitration was used in Germany on a semi-plant scale (10 tons a month). Cellulose was first treated with air saturated with nitric acid vapours, and then the partially nitrated cellulose was immersed in 98% nitric acid. The initial treatment of the cellulose with vapours of nitric acid prevents the surface gelatinization that ordinarily occurs if cellulose is introduced direct into concentrated nitric acid. The product obtained in this way... 

Sato, H., Hirose, K., Nagai, K., Yoshioka, H. and Nagaoka, Y. Vapour phase nitration of benzene over solid acid catalysts II. Nitration with nitric acid (1) montmorillonite and mixed metal oxide catalysts, Appl. Catal., A, 1998, 175, 201-207. 

Nitromethane, CH3N02, is a volatile liquid. It may be obtained by direct vapour phase nitration of paraffinic hydrocarbons either with nitric acid vapours (Hass et al. [1-8]) or with nitrogen dioxide (T. Urbanski and Slebodzinski [9]). It may also be prepared by the action of sodium- or potassium nitrite on chloroacetic acid... 

As is known (Vol. I). alkanes can be nitrated in vapour phase by nitric acid or nitrogen dioxide. Nitration with nitric acid at temperatures of 400-435 C (method of Hass, Vol. I. p. 86) became a well established commercial method of making nitroalkanes. A considerable number of papers mainly by Hass and co-workers (Vol. 1) and Titov (Vol. I) gave both theoretical and practical foundations for this remarkable process and subsequently less theoretical work has appeared. Less attention was paid to the nitration of alkanes with nitrogen... 

Investigations carried out have shown that controlled hydrolysis co-precipitation method and sol-gel method with use of polyvinylalcohol as template allow to prepare superacid WO3/Z1O2 materials which are highly active in n-hexane isomerization and vapour-phase benzene nitration with nitric acid. Doping of WO3/Z1O2 with Fe and Mn ions, as well as with silica and alumina [6] does not improve the catalytic properties in n-hexane isomerization. 

Wilson and Miles suggest the following second order equation for the rate of nitration with nitric acid in vapour phase ... 

Lee, Chung and Albright [57] examined the nitration of propane with nitric acid vapours at 425-430°C when propane to nitric acid ratios were 6 1 and... 

Early attempts to nitrate thiophene and to reduce a nitro-product, in analogy with benzene chemistry, were unsuccessful until the conditions for nitration of thiophene were found. Eventually, rather special conditions were developed thiophene vapour mixed with air was passed for several hours through fuming nitric acid. After work-up, mononitrothiophene and a dinitrothiophene were isolated [125], Later it became clear that the failure in thiophene nitration with nitric acid is due to the presence of nitrous acid that led to the formation of nitrosothiophene, which is prone to decomposition [ 126]. A mixture of nitric acid with acetic anhydride in glacial acetic acid can mononitrate thiophene very effectively (Scheme 84) [127]. 

The simpler nitrop>arafIins (nitromethane, nitroethane, 1- and 2-nitroproj)ane) are now cheap commercial products. They are obtained by the vapour phase nitration of the hydrocarbons a gaseous mixture of two mols of hydrocarbon and 1 mol of nitric acid vapour is passed through a narrow reaction tube at 420-476°. Thus with methane at 476° a 13 per cent, conversion into nitro methane is obtained ethane at 420° gives a 9 1 mixture of nitroethane (b.p. 114°) and nitromethane (b.p. 102°) propane at 420° afifords a 21 per cent, yield of a complex mixture of 1- (b.p. 130-6°) and 2-nitropropane (b.p. 120°), nitroethane and nitromethane, which are separated by fractional distillation. 

Both nitric acid and nitrogen dioxide, in the liquid and vapour phase, have been used for the nitration of the alkyl side chains of various alkyl-substituted aromatics without affecting the aromatic nucleus.Thus, treatment of ethylbenzene with nitric acid of 12.5 % concentration in a sealed tube at 105-108 °C is reported to generate a 44 % yield of phenylnitroethane. The nitration of toluene with nitrogen dioxide at a temperature between 20-95 °C yields a mixture of phenylnitromethane and phenyldinitromethane with the proportion of the latter increasing with reaction temperature. ... 

Ammonium nitrate mixed with litharge expels ammonia from the solid salt at ordinary temp. T. J. Pelouze found that when ammonium nitrate is treated with a little sulphuric acid, ammonium sulphate and nitric acid are formed the same result obtains with the dried salt in fifty times itB weight of sulphuric acid provided the temp, is below 120° but at 150°, nitrous oxide mixed with a little nitric oxide and nitric acid vapour is evolved, and sulphuric acid and water remain. If the salt be mixed with ten times its weight of sulphuric acid, about 75 per cent, of the. salt forms nitric acid and ammonium sulphate, and 25 per cent, forms nitrous... 

If concentrated sulfuric acid is heated with a metal nitrate such as sodium nitrate, nitric acid vapour is produced. 

In favour of the view, that postulates the formation of an addition product during the first stage of nitration this fact should be known to all who are practically engaged in nitration of aromatic hydrocarbons. Immediately before contacting the nitrating acid (HN03 or nitric and sulphuric acids mixture), benzene and toluene give brown coloured products amid nitric acid vapours. On dissolution in the acid these products decolourize at once. It is quite possible they arc addition products formed by nitric acid vapours with the hydrocarbon. 

McCleary and Degering [36] present a different mechanism for the nitration of paraffins with the nitric acid vapour, although like Titov they also assume the formation of free radicals ... 

A number of explosions in French TNT factories which occurred during 1917-18, in particular the one at Neuville-sur-Saone (1917) which caused the destruction of the whole plant, were presumably due to the decomposition of the products of reaction of metals, such as lead or iron, with TNT under the conditions described in a paper by Kovache and Thibon [31]. Products readily decomposed, and sensitive to friction and impact, were formed in various parts of the plant where contact between these metals and the TNT could occur in the presence of dilute nitric acid, for example in the TNT washing tank and granulators. Similar compounds were found in a nitrator where part of the TNT in close contact with metals was subjected to the action of nitric acid vapours, for example around the seals at the stirrer shaft bearings. 

Detection of Ruthenium in Platinum Alloys.—In order to detect the presence of ruthenium in platinum alloys, a portion of the alloy is fused with lead. The melt is extracted with nitric acid and the residue ignited in contact with air in order to volatilise the osmium. The mass may now contain platinum, iridium, rhodium and ruthenium, and is fused with potassium nitrate and hydroxide. The whole is dissolved in water, treated with excess of nitric acid and allowed to stand in a flask covered with filter-paper. In a few hours (12-24) the filter-paper darkens if ruthenium is present, in consequence of the evolution of vapour of its tetroxide. To confirm the presence of ruthenium, the paper is ignited and the ash fused with potassium nitrate and hydroxide. On extraction with water the orange colour of potassium ruthenate is obtained.1... 

The nitration of propionic acid with nitric acid in the vapour phase gave a small yield (5%) of 3-nitropropioiiic acid according to Hass and Hudgin (209). 

Albright ct al (971 examined the inlluence of gamma radiation upon Ihc vapour phase nitration of propane with nitric acid at 400 450°(. There was a slight effect of irradiation on the yield of nitro products, in agreement with the above finding (Ob). The increase of the yield o nitro alkanes was of the order of onlv 10 15%. 

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