Nitric-sulphuric acid mixtures

High silicon iron offers excellent resistance to attack by all concentrations of nitric-sulphuric acid mixtures. The mixed acid corrodes the iron at rates never greater and often lower than the individual acids of comparable concentration. 

Naoum [4] nitrated 1,3-butylene glycol and obtained a yield of 93.7%, i.e. from 100 parts of butylene glycol, 187.5 parts of dinitrate were obtained. (See also Mati-gnon et al. [36], Aubry [37]). Aubertein [42], however, pointed out the difficulty of nitrating 1,3-butylene glycol with nitric-sulphuric acid mixtures. 

On a small scale methyl nitrate can be obtained by carefully distilling a mixture of methyl alcohol with nitric add containing urea nitrate [18] or with nitric-sulphuric acid mixture at 40 or 18°C [19]. 

Oxidation of the dihydropyridine derivative is most conveniently carried out with an aqueous nitric-sulphuric acid mixture. Removal of the ethoxycarbonyl groups may be achieved by a stepwise hydrolysis and decarboxylation sequence, but the one-step reaction described in Expt 8.29 using soda-lime is convenient. 

As pointed out in Vol. I. p. 146 nitrate ester of -niiroeihanol can be formed by passing ethylene into a nitric-sulphuric acid mixture, and a side reaction is the formation of ethylene glycol dinitratc. However in most experiments nitro-niiraie ester is the minor product of the reaction. The reactions of aikencs with N2O4 were described in the excellent review paper by Shechtcr [50]. The classic work of N. Levy. Scaife et al. (Vol. 1. pp. 594-5) [51 53] should be mentioned... 

Butanotriol is nitrated to trinitrate with a nitric -sulphuric acid mixture. The nitrated product shows good stability. Il is less volatile than nitroglycerine and according to. Meyer is in use for tropic-proof double base powder. 

Nitration with nitric acid-sulphuric acid. The addition of a small proportion of sulphuric acid to nitric acid prevents dissolving PVA in nitric acid. A suspension of PVA in nitric/sulphuric acid mixture is formed. Tlic yield of PVN is best when the concentration of 112804 in the mixed acid is 10-30% (Fig. 64). In such a mixed acid the solubility of PV.N is negligible and the only substances dissolved in the acid are some degradation viscous products in quantity of 2-3%. They can be precipitated with water. 

Fieser and Campbell [71] nitrated dehydroabietic acid with nitric-sulphuric acid mixtures and obtained a product Ci9H25(N02)2C00H, decomposition 178-185 C, identical with this described by Johansson. This was 6,8-dinitro-dehydroabietic acid. It seems to be identical with one of the non-identihed products with three ( ) NO2 groups of Dubourg [69]. 

In a nitric-sulphuric acid mixture at 0 °C, the diethoxyphosphinylamino group in dialkyl A -phenylphosphoramidates is mostly meta directing, although with substantial para directing ability, whereas the dimethoxyphosphinothioyl group is almost completely para directing. ... 

Chromic acid, nitric acid, hydroxyl-containing compounds, ethylene glycol, perchloric acid, peroxides, or permanganates Concentrated nitric and sulphuric acid mixtures Chlorine, bromine, copper, silver, fluorine or mercury Carbon dioxide, carbon tetrachloride, or other chlorinated... 

The furnace scales which form on alloy steels are thin, adherent, complex in composition, and more difficult to remove than scale from non-alloy steels. Several mixed acid pickles have been recommended for stainless steel, the type of pickle depending on the composition and thickness of the scale For lightly-scaled stainless steel, a nitric/hydrofluoric acid mixture is suitable, the ratio of the acids being varied to suit the type of scale. An increase in the ratio of hydrofluoric acid to nitric acid increases the whitening effect, but also increases the metal loss. Strict chemical control of this mixture is necessary, since it tends to pit the steel when the acid is nearing exhaustion. For heavy scale, two separate pickles are often used. The first conditions the scale and the second removes it. For example, a sulphuric/hydrochloric mixture is recommended as a scale conditioner on heavily scaled chromium steels, and a nitric/hydrochloric mixture for scale removal. A ferric sulphate/ hydrofluoric acid mixture has advantages over a nitric/hydrofluoric acid mixture in that the loss of metal is reduced and the pickling time is shorter, but strict chemical control of the bath is necessary. 

The conclusion that the nitration of quinoline in sulphuric acid takes place via the conjugate acid has been confirmed by Moodie et al.50, who measured the rates of nitration of a wide range of heterocyclic compounds in nitric acid-sulphuric acid mixtures at a range of temperatures. A summary of the second-order rate coefficients and Arrhenius parameters is given in Table 4. From an analysis of the shapes of the plots of log k2 versus sulphuric acid acidity (or some function of this), it was concluded that all of the compounds starred in Table 4... 

Arrhenius parameters for nitration of 4-aikylphenyltrimethyiammonium ions in nitric acid-sulphuric acid mixtures (Table 12). It was argued that the observed Baker-Nathan order of alkyl substituent effect was, in fact, the result of a steric effect superimposed upon an inductive order. However, a number of assumptions were involved in this deduction, and these render the conclusion less reliable than one would like it would be useful to have the thermodynamic parameters for nitration of the methyl substituted compound in particular, in order to compare with the data for the /-butyl compound, though experimental difficulties may preclude this. It would not be surprising if a true Baker-Nathan order were observed because it is observed for all other electrophilic substitutions in this medium1. 

Acetone Concentrated nitric and sulphuric acid mixtures... 

Bakke et al. (1982) have shown how montmorillonite catalyses chlorination and nitration of toluene nitration leads to 56 % para and 41 % ortho derivative compared to approximately 40 % para and 60 % ortho derivatives in the absence of the catalyst. Montmorillonite clays have an acidity comparable to nitric acid / sulphuric acid mixtures and the use of iron-exchanged material (Clayfen) gives a remarkable improvement in the para, ortho ratio in the nitration of phenols. The nitration of estrones, which is relevant in making various estrogenic drugs, can be improved in a remarkable way by using molecular engineered layer structures (MELS), while a reduction in the cost by a factor of six has been indicated. With a Clayfen type catalyst, it seems possible to manipulate the para, ortho ratio drastically for a variety of substrates and this should be useful in the manufacture of fine chemicals. In principle, such catalysts may approach biomimetic chemistry our ability to predict selectivity is very limited. 

Nitrobenzene was submitted to the action of a nitric acid/sulphuric acid mixture. The mixture detonated. It was thought that this accident was caused by a lack of stirring, which caused the reagents to accumulate. A study showed that during this reaction the temperature could reach 2000°C/s. 

Tetranitronaphthalene was prepared by adding nitric acid/sulphuric acid mixture to 1-nitronaphthalene. A solid residue formed after a valve had broken down. The medium was heated to try to melt the residue. This operation gives rise to a precipitate present in large quantities that blocked the stirrer and caused the reactor to detonate violently. 

It is fairly generally believed that nitrosulphonic acid plays an important part in the lead chamber process for the manufacture of sulphuric acid (see p. 153). The vapour pressures of mixtures of sulphuric acid with nitrous or nitric acid or with both these acids, within the range occurring in the chambers, increase with the nitrogen acid content and with rise in temperature, and the total pressure is always higher than the sum of the individual pressures, especially when the sulphuric acid is concentrated, for nitric acid - sulphuric acid mixtures this may be explained 1 by the occurrence of the following... 

The action of concentrated sulphuric acid and the formation of mixed sulphuric-nitric esters, as well as the action of nitric add and mixtures of nitric—sulphuric acid and water and of hydrochloric acid have been discussed above. Concentrated hydriodic acid of 1.5 density decomposes nitroglycerine to glycerol and nitric oxides. 

Since according to Hantzsch the H2N03+ ion is the principal nitrating agent, these reactions could account for the fact that oiganic compounds are best nitrated with a nitric mid sulphuric acid mixture with a water content of 10%. 

In his experiments on the nitration of naphthalenesulphonic acid Lantz [85] found that the rate of nitration with a nitric acid and sulphuric acid mixture was highest when the concentration of sulphuric acid used was about 90% H2S04... 

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. 

In the U.S.S.R., the D.V.S. is often named the coefficient of dehydration and a slightly different way of calculating the nitric composition of sulphuric acid mixtures is in use there. This is

nitrating activity suggested by Kholevo. According to Gorst [2], it is the concentration of sulphuric acid in the mixture when the nitric acid is converted into the equivalent quantity of water. 

It has been shown recently by den Hertog and Overhoff [78] that N-pyridine oxide can readily be nitrated with a nitric and sulphuric acid mixture. 4-Nitro-pyridine is formed in good yield-about 81%. 

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... 

The solubility of styphnic acid in nitric acid-sulphuric acid mixtures is very low. 

Giles, Hanson and Ismail [19 found that in mononitration of toluene with a standard nitration mixture of nitric-sulphuric acid and water, the organic phase contained nitric and nitrous acids, but did not include sulphuric acid and water. The authors also studied the role of agitation. Their conclusion was simitar to that reported previously [2) that mass transfer between the phases plays an important role, and a fast reaction takes place in a zone in the aqueous phase adjacent to the interface. It is important to know the diffusivity of the aromatic substrate in the aqueous phase which depends on the design of the nitra-tor. The paper by Strachan [20j also points out the importance of mass transfer in agreement with a previously described statement (Vol. 1, p. 49). 

Diepold [25j described two methods of nitrating PVA with nitric acid alone and with nitric acid/sulphuric acid mixtures. 

Among nitrating agents the most important still remain nitric acid-sulphuric acid mixtures, but some other very efficient nitrating agents related to nitric acid have been found and are in use, mainly on a laboratory scale. 

It is now generally accepted that the nitronium ion NOj is the main nitrat ing agent. Although most industrial nitrations are carried out by nitric acid -sulphuric acid mixtures, some compounds can be nitrated with nitric acid alone (production of tetryl, Vol. Ill, p. 42). Some products, such as PETN (Vol. II, p. 185) are usually obtained by nitration with nitric acid alone and Cyclonite (if made by nitration) is produced exclusively with nitric acid free of N2O4 (Vol. Ill, p. 87). 

Treatment of an aminonitrile with a nitric acid-sulphuric acid mixture at about 0 C produces this ring, probably through the formation of the yV-nitro compound. 

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