Nitrosylsulfuric acid

Solubility sol sulfuric add slightly sol acetic add, acetonitrile, nitromethane, DMF Insol most other organic solvents. 

Form Supplied in pale yellow crystals commercially available. Preparative Method dry SO2 is allowed to pass Into a mixture of 98% nitric acid and acetic acid (3 1) at 0 °C the precipitated NOHSO4 is washed with acetic acid and carbon tetrachloride and dried under vacuum to give the analytically pure reagent. Handling, Storage, and Precautions stable at rt protect from moisture use In a fume hood. 

Nitrosation. Like other nitrosonium salts, namely nitro-sonium tetrafluoroborate and NOPFe, nitrosylsulfuric acid is an efficient nitrosating agent. It has been reported that NOHSO4 

A list of General Abbreviations appears on the front Endpapers 

Ar-NHNHi toAr-Nj. Aryl and acyl hydrazines are converted to azides in good yields on treatment with an equimolar amount ofNOHS04 orNOBF4 (eq7).l  

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At high flame temperatures, small amounts of nitrogen react with oxygen to form nitrogen oxides, NO, primarily nitric oxide, NO. The chemistry of these nitrogen oxides is complex. Ultimately, however, some form nitrosylsulfuric acid, which ends up either as trace amounts in product acids or, in considerably higher concentrations, as condensed acid collected at mist eliminators. 

Caprolactam. At the same time that Dow was constmcting toluene to phenol plants, Snia Viscosa (28—30) introduced two processes for the manufacture of caprolactam (qv) from benzoic acid. The earlier process produced ammonium sulfate as a by-product, but the latter process did not. In either process benzoic acid is hydrogenated to cyclohexanecarboxyHc acid [98-89-5] which then reacts with nitrosylsulfuric acid to form caprolactam [105-60-2]. 

Toray. The photonitrosation of cyclohexane or PNC process results in the direct conversion of cyclohexane to cyclohexanone oxime hydrochloride by reaction with nitrosyl chloride in the presence of uv light (15) (see Photochemical technology). Beckmann rearrangement of the cyclohexanone oxime hydrochloride in oleum results in the evolution of HCl, which is recycled to form NOCl by reaction with nitrosylsulfuric acid. The latter is produced by conventional absorption of NO from ammonia oxidation in oleum. Neutralization of the rearrangement mass with ammonia yields 1.7 kg ammonium sulfate per kilogram of caprolactam. Purification is by vacuum distillation. The novel chemistry is as follows ... 

Snia Viscosa. Catalytic air oxidation of toluene gives benzoic acid (qv) in ca 90% yield. The benzoic acid is hydrogenated over a palladium catalyst to cyclohexanecarboxyhc acid [98-89-5]. This is converted directiy to cmde caprolactam by nitrosation with nitrosylsulfuric acid, which is produced by conventional absorption of NO in oleum. Normally, the reaction mass is neutralized with ammonia to form 4 kg ammonium sulfate per kilogram of caprolactam (16). In a no-sulfate version of the process, the reaction mass is diluted with water and is extracted with an alkylphenol solvent. The aqueous phase is decomposed by thermal means for recovery of sulfur dioxide, which is recycled (17). The basic process chemistry is as follows ... 

Alkyl-5-acetamidoisothiazoles are nitrosated at the 4-position by nitrosylsulfuric acid (78JOC4154). Isothiazoles are sulfonated at the 4-position using either oleum or sulfur trioxide <72AHQ14)1). 

By treating anthraquinone with nitrosylsulfuric acid in the presence of mercury or a mercury compound. Brit. pat. 346,355 [C. A. 26, 1948 (1932)]. 

The starting semicarbazones were most often prepared directly from the a-keto acids. Godfrin proceeded from a-alkyl acetoacetates, which were converted by oxidation with nitrosylsulfuric acid to a-keto-acid oximes and the latter transformed to semicarbazones or thioseraicarbazones by applying semicarbazide or thiosemicarbazide. For glyoxylic acid semicarbazone a very convenient procedure was employed, making use of the hydrolysis of nonisolated chloral semicarbazone. ... 

Nitrosyl-saure, /. nitrosylic acid (hyponitrous acid). -schwefelskure, /. nitrosylsulfuric acid. 

Salpeter-schwefels ure, /. nitrosulfuric acid (a mixture) nitrosylsulfuric acid, -siederei, /. saltpeter works, -stkrkemehl, n. nitrated starch, -stoff, m. nitrogen, -strauch, m. niter bush Nitraria). -ung,/. nitrification, -verbindung, /. nitrate. -waC4)ge, /. nitrometer. 

Nitrosylsulfuric acid. As specified by contract or purchase order... 

Nitrosylsulfuric Acid (Nitroso, Nitrosyl Sulfate, Nitrosulfuric Acid, Nitroxylsulfuric Acid, Nitro-sulfonic Acid, Nitrosyl Hydrogen Sulfate, Nitro Acid Sulfite). HNOs S, NO HS03, HNOS04, ONOSO3H, mw 127.08, N 11.02%, colorl prisms mp, decomps 73.5°. In moist air the crysts decomp with the formation of sulfuric and nitric... 

In the expl industry, it is constantly necessary to deal with nitrosylsulfuric acid, because it forms during the nitration of organic compds as a result of the partial oxidation of the compds by nitric acid. For example, in the manuf of TNT, a small amt forms during the mononitration ... 

HN0S04 +6CO2+17H20 Nitrosylsulfuric acid is highly toxic, and a strong irritant to skin and mucous membranes (Refs 10 11)... 

The diazotization of heteroaromatic amines is basically analogous to that of aromatic amines. Among the five-membered systems the amino-azoles (pyrroles, diazoles, triazoles, tetrazoles, oxazoles, isooxazoles, thia-, selena-, and dithiazoles) have all been diazotized. In general, diazotization in dilute mineral acid is possible, but diazotization in concentrated sulfuric acid (nitrosylsulfuric acid, see Sec. 2.2) or in organic solvents using an ester of nitrous acid (ethyl or isopentyl nitrite) is often preferable. Amino derivatives of aromatic heterocycles without ring nitrogen (furan and thiophene) can also be diazotized. 

For these reasons there are limits to the extent to which the acid concentration can be increased gradually as the basicity of the amines decreases. Nevertheless, diazotization can be carried out without difficulty in 90-96% sulfuric acid. It has already been mentioned that nitrous fumes are given off as soon as nitrite is added to sulfuric acid of lower concentration, but solid sodium nitrite can be dissolved in 90-96% sulfuric acid at 0-10°C smoothly and without evolution of gas. Nitrosylsulfuric acid, N0+HS04, is formed. Directions for the preparation of 2 m nitrosylsulfuric acid are given by Fierz-David and Blangey (1952, p. 244), but sodium hydrogen sulfate crystallizes after some time from acid of this strength so that it is best to prepare a stock solution of 1 m sodium nitrite in 96% sulfuric acid, which is quite stable at room temperature. 

More concentrated solutions of nitrosylsulfuric acid containing no sodium ions can be obtained by reducing a solution of nitric acid in concentrated sulfuric acid with gaseous S02. 

The nitrosylsulfuric acid method is particularly suitable for the diazotization of di- and trinitroanilines and aminoanthraquinones. Such amines may be added directly to the nitrosylsulfuric acid, but it is preferable to run the appropriate amount of nitrosylsulfuric acid into a solution of the amine in 96% sulfuric acid. In general, these diazotizations can be carried out at room temperature. The end-point is determined in the usual manner with iodide paper, but only after first diluting a few drops with ice. On completion, the whole is diluted with ice. The test with iodide paper fails in the case of polynitrodiazonium salts. 

In 1969 a serious explosion took place in Basle when 287 kg (1.3 kmol) of 2-chloro-4,6-dinitroaniline was diazotized in 384 kg 40% nitrosylsulfuric acid. The temperature was increased from 30 °C to 50 °C and kept at that level. Shortly afterwards the explosion occurred three workers were killed and 31 injured, some seriously. The reaction had been carried out twice before in the same way without difficulty. Detailed investigations (Bersier et al., 1971) with the help of differential scanning calorimetry showed that, at the high concentration of that batch, a strongly exothermic reaction (1500 kJ/kg) starts at about 77 °C. In contrast, when the reactants were diluted with 96% sulfuric acid to twice the volume, the reaction was found to begin at 146 °C, generating only 200 kJ/kg. 

In some cases the use of nitrosylsulfuric acid may be avoided if 1-naphthalenesul-fonic acid is added to moderately concentrated sulfuric acid (20-60%). This greatly reduces the evolution of nitrous fumes compared with a solution of pure sulfuric acid of the same hydrogen ion concentration. It has not yet been investigated whether the phenomenon is due to the formation of an ion pair, [C10H7 —SO NO+], or whether it is simply a solubility effect. In any case, the total acidity range of 4-12 m has thereby become available for diazotization technically crude sulfonation mixtures are used after dilution with water, for example, a solution of total acidity 4 m, of which 2.7 m is due to sulfuric acid. A further advantage of the method lies in the stabilizing effect of the naphthalenesulfonic acid on the diazonium compounds formed (see Sec. 2.3). 

Diazotisation of the potentially explosive 2-chloro-4,6-dinitroaniline in the third batch of a new process (at a higher than usual concentration in 40% nitrosylsulfuric acid) led to a violent explosion soon after the temperature had been increased to 50°C. Subsequent DSC work showed that the temperature at which thermal decomposition of the diazonium sulfate solution or suspension sets in is inversely proportional to the concentration of amine, falling from 160°C at 0.3 mmol/g to 80°C at 2 mmol/g. Thermal stability of 17 other diazonium derivatives was similarly investigated. 

See Nitric acid 4-Chloro-2-nitroaniline Nitrosylsulfuric acid... 

Presence of dinitrogen tetraoxide appears to be essential to catalyse smooth formation of nitrosylsulfuric acid from sulfur dioxide and nitric acid. In its absence, reaction may be delayed and then proceed explosively. 

Diazotization is the reaction of a primary aromatic amine with a nitrosating agent, such as sodium nitrite or, to a lesser extent, with nitrosylsulfuric acid N0S04H, nitrous gases, or organic nitrites in an aqueous acidic solution at a temperature between 0 and 5°C, converting the amine to its diazonium salt ... 

Nitrosylsulfuric acid is employed for amines of very low basicity e.g., those with more than one electronegative function. Compounds such as di- and trinitroani-lines, halogenated nitroanilines, and tetrahalogenanilines will not react under more moderate conditions. If necessary, these amines can also be diazotized after dissolving them in a mixture of glacial acetic acid and concentrated hydrochloric acid. 

Amines of very low basicity undergo diazotization after being dissolved in concentrated sulfuric acid. The nitrosating agent is provided by nitrosylsulfuric acid, which is either purchased commercially or easily prepared by dissolving solid sodium nitrite in concentrated sulfuric acid. 

Sulfuric acid as a reaction medium may be replaced by glacial acetic acid or by a mixture of glacial acetic acid/nitrosylsulfuric acid. In the former case, half-concentrated hydrochloric acid is added, and diazotization proceeds in an aqueous sodium nitrite solution. The combination of glacial acetic acid/nitrosylsulfuric acid is a particularly useful medium for the bisdiazotization of 1,2-, 1,3-, or 1,4-di-aminobenzenes (phenylenediamines). 

Amines which are considerably or entirely insoluble in water are dissolved in glacial acetic acid or in other organic media, possibly mixed with water e.g., alcohols or aprotic solvents. Addition of acid is followed by a typical diazotization reaction in an aqueous sodium nitrite solution. Other possible sources of the nitrosating species NO include nitrosylsulfuric acid, nitrosylchloride, alkylnitrite, and nitrous gases. 

Nitrosylsulfuric acid, prepared by dissolving sodium nitrite in concentrated sulfuric acid, is employed for amines of low basicity, whose diazonium salts will hydrolyze in dilute acid. In order to synthesize Pigment Orange 5, for instance, 2,4-dinitroaniline is dissolved in concentrated sulfuric acid and diazotized preferably with nitrosylsulfuric acid. Coupling is carried out with a (3-naphthol suspension, produced by acidifying a sodium naphtholate solution. 

Aminoanthraquinone is diazotized advantageously with nitrosylsulfuric acid after being dissolved in sulfuric acid. Coupling the diazo compound onto barbituric acid, for instance, affords a yellow pigment [3] with the structure 79 ... 

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