Nitration with mixtures of nitric and sulphuric acids

NITRATION WITH MIXTURES OF NITRIC AND SULPHURIC ACIDS 

The first attempts to nitrate cellulose by means of mixtures made up from nitric and sulphuric acids were made as early ashy Vieille who in 1884 [1] also found that increasing the concentration of sulphuric acid in the mixture diminished the rate of the nitration reaction. 

The rate of nitration of cellulose is dependent both on the rate of the chemical reaction of esterification itself, and on the rate of diffusion of the nitrating add into the cellulose fibres. This is discussed later (p. 356). 

The first extensive investigations into the relation between the nitrogen content of nitrocellulose and the composition of the mixed add were carried out by Bruley (14]. They are summarized graphically in Fig. 119. 

Lunge et al. [15] examined the effect of the composition of mixed add, and the influence of the nitration temperature within the range from 0 to 80°C on the nitrogen content of nitrocellulose, the content of non-nitrated cellulose, the yield, the solubility of the products in ether-alcohol mixture and the viscosity of the acetone solution. Cotton linters were used. From these experiments it has been established that nitrocellulose containing more than 13.5% N is unstable and decomposed readily, as mentioned before. 

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Liquid-liquid reactions occur between two or more liquid phases whereby a system consisting of an organic and an aqueous phase is applied most frequently. Usually reaction takes place in one phase only. Phase-transfer catalysts are sometimes used to make transfer of a reactant to the reacting phase easier. Among typical liquid-liquid reactions utilized in fine chemicals manufacture are nitrations with mixtures of nitric and sulphuric acid, conventional hydroxylations performed with hydrogen peroxide, esterifications, alkylations, brominations, and iodinations. 

Absorption of nitric acid by cellulose and nitrocellulose Nitration with mixtures of nitric and sulphuric acids... 

A similar scheme for the nitration process was given by Reddelien [5] who expressed the view that nitration of aromatic hydrocarbons with mixtures of nitric and sulphuric acids gave addition products, e.g. 

Holleman [55] gives the following data on the composition of the nitration products obtained in the nitration of different monosubstituted benzene derivatives with mixtures of nitric and sulphuric acids (Table 2). As appears from the data shown below, the substituent already present affects the orientation of the group which is being introduced. It is evident that nitration can be influenced by the steric factor. For exampl tert.-butylbenzene is mainly nitrated in para (72.7%) and to a much lesser extent in ortho (15.8%) positions (H. C. Brown and Nelson [88]). 

Prepared by the direct nitration of naphthalene with a mixture of nitric and sulphuric acids. Its chief use was for the preparation of l-naphthyiamine and its derivatives. 

It is prepared by the direct nitration of toluene with a mixture of nitric and sulphuric acids. TNT is a very stable, violent and powerful high explosive, but less sensitive to shock and friction than picric acid. It is widely used as a filling for shells, bombs, etc. often mixed with ammonium nitrate and other high explosives. The lower grades of TNT may contain isomers which under hot storage conditions may give rise to exudation. 

Although these nitrations proceed smoothly, attempted nitration of an unidentified substance should always be carried out with extreme care, e.g., by working in a fume-cupboard and pointing the boiling-tube away from the operator. Many organic substances e.g., alcohols and phenols) react with great violence with a mixture of nitric and sulphuric acids. 

The first nitration to be reported was that of beri2ene itself. Mitscher-lich in 1834 prepared nitrobenzene by treating benzene with fuming nitric acid. Not long afterwards the important method of effecting nitration with a mixture of nitric and sulphuric acids ( mixed acid ) was introduced, evidently in a patent by Mansfield the poor quality of early nitric acid was probably the reason why the method was developed. Since these beginnings, nitration has been the subject of continuous study. 

Franchimont and Klobbie [17] prepared ethylenedinitramine (EDNA, Haleite) by the nitration of ethylene urea (2-imidazolidone) with a mixture of nitric and sulphuric acids. (According to Schweitzer [18], ethylene urea is obtainable either by the action of urea on ethylenediamine at 110°C (initially) to 240-250°C (finally) in quantitative yield or by the action of urea on ethylene glycol at 160-240°C in 55% yield. W. E. Bachmann et al. [19] prepared ethylene urea by the action of ethyl carbonate on ethylenediamine in approximately 60% yield.) Hydrolysis of the dinitroethy-lene urea so formed gives ethylenedinitramine. Bachmann recommends nitration with mixed nitric acid and acetic anhydride ... 

Noma, Oya and Nakamura [33] examined the reaction of nitrating polyvinyl alcohol and concluded that neither nitration with a mixture of nitric and sulphuric acid, nor nitration with nitric and acetic acid can bring about the esterification of all the hydroxyl group. This is probably due to simultaneous hydrolysis. They recommend nitrating either with a composition of nitric add and acetic anhydride or a solution of nitric acid in carbon tetrachloride, where by a higher nitrated product, softening at a temperature of 40-50°C, is obtained. 

The degradation of nitrostarch is also considerable, if starch is nitrated by means of a mixed acid composed of nitric and sulphuric acid. On the contrary, application of nitrating mixture consisting of nitric acid and ortho-phosphoric acid makes it possible to obtain a product nearly twice as viscous as that obtained by treatment with a mixture of nitric and sulphuric acid (T. Urbanski and Kapu-Scihski [36]). This shows that the mixture of nitric and phosphoric acid causes less degradation of starch than nitric acid alone or mixed with sulphuric acid. Previously, Berl and Kunze [37] had come to the same conclusion. They found the product of... 

The Hantzsch theory was supported by Lauer and Oda [32], who examined the nitration of anthraquinone Mid nitrobenzene with mixtures of nitric Mid sulphuric acid, the sulphuric acid containing from 20% water to 5% sulphur trioxide. 

Martinsen [83] observed already in 1905 that the rate of nitration of nitrobenzene with a mixture of nitric and sulphuric acids depends on the concentration of sulphuric acid, viz. it increases with the concentration up to 88.7% H2S04, after which further increase in sulphuric acid concentration results in a decreasing rate of nitration. 

In the days when anhydrous nitric acid was not easily available, nitric acid salts (NaN03, KN03) mixed with sulphuric acid were widely used for nitration. Such mixtures acted similarly to the mixture of nitric and sulphuric acids. Later, as synthetic nitric acid became one of the most readily available chemical products, and the production of nitric acid salts from nitric acid had started, nitrating mixtures with sodium or potassium nitrates were abandoned. This is the principal explanation for the scarcity of investigations on the structure and action of such mixtures. It is believed that in such mixtures the nitronium ions are present, according to the equation ... 

The nitration reaction rate depends on the kind nature of the cation. Mixtures of nitric and sulphuric acids nitrate the most slowly, and lithium nitrate acts the most rapidly. With regard to activity cations may be ranged in the following way ... 

According to Schaarschmidt [18] the mechanism of nitration with a mixture of nitric and sulphuric acids consists in the formation of nitric anhydride which becomes attached to the aromatic compound. The addition compound is unstable and decomposes, giving a nitro compound and nitric acid. The mechanism of nitration suggested by Schaarschmidt is ... 

The influence of the nitration temperature on the orientation of a nitro group is in certain cases rather marked When nitrating toluene with a mixture of nitric and sulphuric acids at -5°C, Pictet [56] observed that more para-isomer was obtained than at the temperature of 0°C. 

K. Lauer [62] obtained the results (given in Table 5) by nitrating aniline and anilides with nitric and with mixtures of nitric and sulphuric or acetic acids at 20°C, over 24 hr. 

Kirk Mid Brandt [25] nitrated toluene with a mixture of nitric and sulphuric acids both by the usual method and by the simultaneous use of the electrolytic method Mid found that with the latter technique higher yields could be obtained. AtMiasiu Mid Belcot [26,27] treated aromatic hydrocarbons with a much dilute nitric acid (at a concentration insufficient for nitration) and, due to the electrolysis, which they carried out simultaneously, they succeeded in obtaining nitration in the anode area, hi studying the reaction they observed particularly vigorous oxidation processes. 

Deville [26] first prepared dinitrobenzene in 1841 by treating benzene with concentrated nitric acid and heating it to the boiling point. Soon after that Mus-Pratt and Hofmann [27] obtained it, using a mixture of nitric and sulphuric acid for the nitration. 

They nitrated radioactive toluene-l-14C with a mixture of nitric and sulphuric acid at 0°, 30°, 45° and 60°C. After nitration the whole was diluted, with water and steam distilled. Thus mononitro-products were separated from unnitrated toluene and dinitro products. The weighted sample of isomeric mononitro-toluene was diluted with a known quantity of non-radioactive m- nitrotoluene and the mixture was distilled through an efficient micro-fractionating column in order to recover a pure sample of m- nitrotoluene. The m- nitrotoluene was oxidized by dichromate-sulphuric acid mixture to m- nitrobenzoic acid and this material was radio-assayed. The proportion of m- nitrotoluene in the mixed nitrotoluenes was calculated from the formula... 

Noelting and Forel [11] found that the content of p- nitrotoluene increased gradually with increase in the HN03 content of the nitrating acid. Thus, when nitrating toluene with a mixture of nitric and sulphuric acids, the authors obtained 60% of the p- isomer but if nitric acid alone was used, 66% of p- nitrotoluene was obtained,... 

Beilstein and Kuhlberg [28], by nitrating ethylbenzene with a mixture of nitric and sulphuric acids at a low temperature obtained two oily products which proved to be o- and p- nitroethylbenzenes. 

According to Pictet [28] at very low temperatures ranging from -50°C to -60°C, nitration with a mixture of nitric and sulphuric acids resulted in the formation of a large quantity (about 46%) of the 1,3-isomer. 

By the nitration of commercial dinitronaphthalene a product is obtained which consists of the 1,3,6,8-, 1,3,5,8- and 1,4,5,8-isomers. The existence of the a- isomer is not quite certain. It was reported by d Aguiar [14], who obtained it by the prolonged boiling of 1,5-dinitronaphthalene with nitric acid (sp. gr. 1.45). The exper-riments were repeated by Beilstein and Kuhlberg [15] with a mixture of nitric and sulphuric acids instead of the nitric acid alone. However, Will s investigations [17]... 

Pentanitrophenol (m. p. 190°C) was obtained by Blanksma [21], who nitrated 3,5-dinitrophenol with an anhydrous mixture of nitric and sulphuric acids. The product was precipitated, and could then be recrystallized from chloroform. 

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