Nitric acid in the presence of mercuric nitrate

The catalytic action of mercuric nitrate in the nitration of anthraquinone with nitric acid was observed in 1906 by Holdermann [122], Soon after that, Wolffen-stein and Boters [123] observed the specific influence that mercuric nitrate exercised on the formation of the products of nitration of benzene. They showed that at a certain concentration of nitric acid, mostly nitrophenols were formed ( oxy-nitration reaction). 

In his later studies Wolffenstein found that the hydroxyl group could be introduced in this way into the aromatic ring, not only in the case of benzene but also with its derivatives as well. For example, benzoic acid yielded trinitro-m-hydroxy-benzoic acid in the presence of mercuric nitrate  

Broders [124] isolated from the nitration products an organomercuric compound to which he ascribed the following formula  

On this basis Desvergnes [125] suggested a mechanism for nitration in the presence of mercuric nitrate that assumes the formation of diphenylmercury as an intermediate product. 

Nitrobenzene is also formed besides nitrophenols and this has been explained by Desvergnes according to the following series of reaction  

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The catalytic process for the production of picric acid directly from benzene in one step by the action of nitric acid in the presence of mercuric nitrate has much theoretical interest and has been applied, though not extensively, in plant-scale manufacture. It yields about as much picric acid as is procurable from the same weight of benzene by the roundabout method of sulfonating the benzene, converting the benzene sulfonic acid into phenol, and nitrating the phenol to picric acid—and the benzene which is not converted to picric acid is for the most part recovered as such or as nitrobenzene. The first mention of the process appears to be in the patent of Wolffenstein and Boeters.55... 

A partial radical substitution may be responsible for the nitration of nitrobenzene to dinitrobenzenes by nitric acid in the presence of mercuric oxide reported by Ogata and Tsuchida [118]. They found 26% of o- and only 24% m-dinitrobenzenes. 

Mercurous Nitrate. Mercurous nitrate [10415-75-5] Hg2N20 or Hg2(N02)2, is a white monoclinic crystalline compound that is not very soluble in water but hydrolyzes to form a basic, yellow hydrate. This material is, however, soluble in cold, dilute nitric acid, and a solution is used as starting material for other water-insoluble mercurous salts. Mercurous nitrate is difficult to obtain in the pure state directly because some mercuric nitrate formation is almost unavoidable. When mercury is dissolved in hot dilute nitric acid, technical mercurous nitrate crystallizes on cooling. The use of excess mercury is helpful in reducing mercuric content, but an additional separation step is necessary. More concentrated nitric acid solutions should be avoided because these oxidize the mercurous to mercuric salt. Reagent-grade material is obtained by recrystaUization from dilute nitric acid in the presence of excess mercury. 

Davis [127,128] and later Blechta and Patek [129] found that as a result of nitrating toluene in the presence of mercuric nitrate, besides nitrotoluenes, trinitro-m- cresol and p- nitrobenzoic acid could also be obtained. The authors explained the mechanism of the reaction by assuming the formation of toluene and the mercury salt complex to be the first stage. On decomposition of the complex by the action of nitric acid, the activated hydrocarbon thus formed was nitrated. 

McKie [142] found the yield of the nitration product to be higher when mercuric nitrate was present in nitric acid. Thus for example, phenanthrene, when nitrated with anhydrous nitric acid in the presence of Hg(N03)2, gave nitrophenan-threne in a yield higher by 13% than when nitric acid alone had been used. Likewise the yields of nitro derivatives of phenol and a- naphthol could be increased by addition of mercuric nitrate to dilute nitric acid. 

MacKie and Orton [71] found that tetranitromethane could be obtained by reacting anhydrous nitric acid with acetylene in the presence of mercuric nitrate. During World War II the Germans manufactured tetranitromethane by this method on a semi-commercial scale, after they had developed the industrial process (Schim-melschmidt [72]). 

Nitration of acetylene in the presence of mercuric nitrate seems to be the most common method of preparation of TNM. It means that the reaction is not stopped at the stage of the formation of nitroform (144) but the latter is further nitrated under the action of the excess of nitric acid. 

In the titrmetric procedure, the serum is diluted in 0.07 N nitric acid and titrated with a dilute mercuric nitrate solution in the presence of diphenylcarbazone (34). A purple color forms when excess mercury ions appear, over that needed to complex the chloride. Using an ultramicro buret this method has found wide use in the past. The microburets which are available such as the Rehburg buret are typified in Figure 22. 

Many metal chlorides when heated with an excess of nitric acid are converted into the nitrates. Thus, J. L. Smith found that the transformation occurs with potassium or sodium chloride in the presence of 7 to 8 parts of nitric acid J. S. Stas said that at 40°-50°, potassium, sodium, or lithium chloride require respectively 3, 4, and 5-5 parts of nitric acid. J. L. Smith said that ammonium chloride and nitric acid yield nitrous oxide. H. Wurtz found that auric, cadmium, cerium, lanthanum, didymium, ferric, and platinic chlorides are decomposed by nitric acid incompletely and with difficulty. S. Schlesinger said that the two copper chlorides, mercurous, zinc, and lead chlorides, are decomposed, but, added H. Wurtz, with difficulty and incompletely while mercuric ajid silver chlorides are not attacked. F. Rose found cobalt amminochlorides are readily converted into the nitrate. 

It seems to be certain that the oxynitration reaction in the presence of mercury salts proceeds through the formation of phenylmercuric nitrate. The isolation of phenylmercuric nitrate from a reaction mixture in dilute nitric acid by several authors (Carmack and his co-workers [135], Titov and Laptev [71], and also Bro-ders [124]) favours this view. If an intermediate nitroso compound is formed in the reaction its formation should be ascribed to the reaction between phenylmercuric nitrate and nitrous acid. This view, based on earlier experiments of Baeyer [136], Bamberger [137], Smith and Taylor [137a], has since been confirmed by Westheimer, Segel and Schramm [138], who considered the nitroso compound formed from an organo-mercuric compound to be the principal intermediate product in the Wolffenstein and Boters reaction. 

It is rather important to note that if an aromatic nitro compound is the substance being nitrated, addition of mercuric nitrate to the nitric acid has no effect on the reaction. For example, nitrobenzene is nitrated to dinitrobezene in the same yield both in the presence of a mercury salt and in its absence. This can be explained by the fact that nitro compounds such as nitrobenzene do not yield addition product with mercuric salts. 

If the mercuric nitrate solution contains an excess of potassium nitrite and 1 per cent, nitric acid and acetylene be passed into the cold mixture, mtritoHliynercuracetaldehycU is precipitated as a bright yellow powder. It is explosive, and is proved to be a nitrite by its behaviour towards a-naphthy]amine in the presence of acetic and hydrochloric aeids. ... 

MERCURIC THIOCYANATE (592-85-8) Hg(SCN)i Moderately unstable solid. Possible violent reaction with strong oxidizers strong acids organic peroxides, peroxides and hydroperoxides potassium chlorate potassium iodate, silver nitrate, sodium chlorate, nitric acid. Incompatible with ammonia, chlorates, hydrozoic acid, methyl isocyanoacetate, nitrates, nitrites, perchlorates, sodium peroxyborate, trinitrobenzoic acid, urea nitrate. When heated, this material swells to many times its original bulk. Attacks aluminum in the presence of moisture. Decomposes above 329°F/165°C, releasing toxic mercury and cyanide fumes, and sulfur and nitrogen oxides. On small fires, use dry chemical powder (such as Purple-K-Powder), alcohol-resistant foam, or COj extinguishers. MERCURIC (Spanish) (7439-97-6) see mercury. 

BARIUM CYANIDE (542-62-1) Violent reaction with sodium nitrite. Reacts, possibly violently, with metal chlorates, fluorine, magnesium, mercurous chloride, nitrates, nitrites, nitric acid, perchlorates, strong oxidizers. Forms sensitive explosive mixtures with potassium chlorate. Corrosive to metals, especially in the presence of moisture. 

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