Nitrous acid from nitrogen dioxide

Fig. 5-3. Behavior of nitrous acid and nitrogen dioxide during the night of August 4-5, 1979, at Riverside, California. PDT = Pacific Daylight Time. [From Platt et al. (1980b) with permission.]...

The gas may be made by the reaction of sodium chlorate with hydrochloric acid with the production of coproduct chlorine (56, 106, 197, 206) or by the reaction of chlorate with concentrated sulfuric acid (225) or a reducing agent such as sulfur (205), sulfur dioxide (225), oxalic acid (225), nitrous acid (5), nitrogen dioxide (169, 221), methanol (54), or organic peroxides (124). Chlorine dioxide may be generated electrolytically from chlorite (51, 188). 

Jenkin, M. E., R. A. Cox, and D. J. Williams, Laboratory Studies of the Kinetics of Formation of Nitrous Acid from the Thermal Reaction of Nitrogen Dioxide and Water Vapor, Atmos. Enriron., 22, 487-498 (1988). 

Photolytic. Major products reported from the photooxidation of butane with nitrogen oxides under atmospheric conditions were acetaldehyde, formaldehyde, and 2-butanone. Minor products included peroxyacyl nitrates and methyl, ethyl and propyl nitrates, carbon monoxide, and carbon dioxide. Biacetyl, tert-butyl nitrate, ethanol, and acetone were reported as trace products (Altshuller, 1983 Bufalini et al, 1971). The amount of sec-butyl nitrate formed was about twice that of n-butyl nitrate. 2-Butanone was the major photooxidation product with a yield of 37% (Evmorfopoulos and Glavas, 1998). Irradiation of butane in the presence of chlorine yielded carbon monoxide, carbon dioxide, hydroperoxides, peroxyacid, and other carbonyl compounds (Hanst and Gay, 1983). Nitrous acid vapor and butane in a smog chamber were irradiated with UV light. Major oxidation products identified included 2-butanone, acetaldehyde, and butanal. Minor products included peroxyacetyl nitrate, methyl nitrate, and unidentified compounds (Cox et al., 1981). 

Nitrous acid catalysis also takes place in the nitration of such compounds (naphthalene) that are unable to undergo nitrosation on the given conditions or whose nitrosation proceeds slower than nitration. As accepted, the nitrosonium ion is formed from HNOj in acid media. The nitrosonium ion oxidizes an aromatic substrate into a cation-radical and transforms into nitric oxide. The latter reduces nitronium cation to nitrogen dioxide that gives a a-complex with the aromatic cation-radical ... 

At low acid concentrations, nitric oxide tends to form. This evidently may attack nitrosophenol to form diazonium compounds directly. The diazonium salts, in turn, may couple with unreacted phenol to give colored products. Nitrous acid may also produce nitrophenols from phenols. The mechanism of this reaction may involve oxidation of initially formed nitrosophenols, homolytic attack by nitrogen dioxide, or nucleophilic attack by nitrite ions [1]. 

R. H. Robinson found sodium nitrite to be unsuitable as a fertilizer, particularly in acid soils, owing to losses of nitrogen by decomposition. According to C. Marie and R. Marquis, nitrous acid is liberated from aq. soln. of the alkali nitrites by carbon dioxide, so that a strip of potassium iodide-starch paper suspended over the liquid is coloured blue. 0. Baudisch found that the reduction of nitrite by potassium ferrocyanide and oxygen is sensitive to light. M. Oswald found that the presence of sodium sulphate lowers the solubility of sodium nitrite enormously— at 16°, a sat. soln. of the nitrite alone has 81-6 per cent. NaN02, but a sat. soln. of both salts together has 11-8 per cent, sodium sulphate, and 53-9 per cent, of sodium... 

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