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Nitrous acid

About: Nitrous acid is a research topic. Over the lifetime, 2096 publications have been published within this topic receiving 40237 citations. The topic is also known as: HNO2 & [NO(OH)].


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Journal ArticleDOI
TL;DR: It is demonstrated here that only low pH reaction conditions favor the deamination of N-sulfated D-glucosamine residues; the reaction proceeds very slowly at pH 3.5 or above and at room temperature solutions of nitrous acid lose one-fourth to one-third of their capacity to deaminate amino sugars in 1 h at all pHs.
Abstract: In the reactions used to break heparin down to mono- and oligosaccharides, androsugars are formed at two stages. The first of these is the well-known cleavage of heparin with nitrous acid to convert the N-sulfated D-glucosamines to anhydro-D-mannose residues; this reaction has been studied in detail. It is demonstrated here that only low pH (less than 2.5) reaction conditions favor the deamination of N-sulfated D-glucosamine residues; the reaction proceeds very slowly at pH 3.5 or above. On the other hand, N-unsubstituted amino sugars are deaminated at a maximum rate at pH 4 with markedly reduced rates at pH2 or pH6. At room temperature solutions of nitrous acid lose one-fourth to one-third of their capacity to deaminate amino sugars in 1 h at all pHs. A low pH nitrous acid reagent which will convert heparin quantitatively to its deamination products in 10 min at room temperature is described, and a comparison of the effectiveness of this reagent with other commonly used nitrous acid reagents is presented. It is also shown that conditions used for acid hydrolysis of heparin convert approximately one-fourth of the L-iduronosyluronic acid 2-sulfate residues to a 2,5-anhydrouronic acid. This product is an artifact of the reaction conditions, and its formation represents one of several pathways followed in the acid-catalyzed cleavage of the glycosidic bond of the sulfated L-idosyluronic acid residues.

856 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that an artificial increase of the mixing ratio of the oxides of nitrogen in the stratosphere by about 1×10−8 may lead to observable changes in the atmospheric ozone level.
Abstract: The distribution of the compounds NO, NO2, NO3, N2O5, and HNO3 has been calculated for different choices of relevant parameters, the values of which are uncertain. An appreciable part of the NO and NO2 is converted to NO3, N2O5, HNO3 and possibly HNO2 is the ozone layer. Reactions of odd oxygen with NO and NO2 may be the dominating reassociation processes for odd-oxygen particles in the region below 45 km which is very important for the global ozone budget. Several processes may lead to the presence of significant amounts of nitrogen oxides, nitrous acid, and nitric acid in the stratosphere. Reported variations during the solar cycle of ozone concentrations above 30 km (Dutsch, 1969) can be explained by corresponding variations in the stratospheric odd nitrogen oxide content. An artificial increase of the mixing ratio of the oxides of nitrogen in the stratosphere by about 1×10−8 may lead to observable changes in the atmospheric ozone level. Chains of reactions involving the constituents OH, H2O2, and HO2 also lead to the catalytic destruction of odd oxygen. The presence of nitric acid with a mixing ratio of about 3×10−9 in the ozone layer (Murcray et al., 1968; Rhine et al., 1969) indicates much larger OH and HO2 concentrations than can be explained solely by the reaction O(1D) + H2O → 2 OH. The reaction N2O5 + H2O → 2HNO3 followed by O + HNO3 → OH + NO3 may also be an important source of OH if the rate constants given by Jaffe and Ford (1967) are adopted. It is difficult to explain the measured nitric acid concentrations between 20 and 30 km with the reaction HO2 + NO + M → HNO3 + M. Laboratory data (Asquith and Tyler, 1969) indicate that the reaction H2O2 + NO2 → HNO3 + OH (Nicolet, 1970α) is unimportant in the atmosphere.

551 citations

Journal ArticleDOI
07 Jul 1972-Science
TL;DR: The formation of carcinogenic N-nitroso compounds by the chemical reaction between nitrous acid and oxytetracycline, morpholine, piperazine, N-methylaniline, methylurea, and (in some experiments) dimethylamine was blocked by ascorbic acid.
Abstract: The formation of carcinogenic N-nitroso compounds by the chemical reaction between nitrous acid and oxytetracycline, morpholine, piperazine, N-methylaniline, methylurea, and (in some experiments) dimethylamine was blocked by ascorbic acid. The extent of blocking depended on the compound nitrosated and on the experimental conditions. Urea and ammonium sulfamate were less effective as blocking agents. The possibility of in vivo formation of carcinogenic N-nitroso compounds from drugs could be lessened by the combination of such drugs with the ascorbic acid.

500 citations

Journal ArticleDOI
09 Mar 2006-Nature
TL;DR: This work exposes humic acid films to nitrogen dioxide in an irradiated tubular gas flow reactor and finds that reduction of nitrogen dioxide on light-activated humic acids is an important source of gaseous nitrous acid.
Abstract: Nitrous acid is a major photochemical precursor of the hydroxyl radical, a key oxidant in the degradation of air pollutants in the lower atmosphere. The gas is known to accumulate in the lower troposphere at night, but the recent discovery of enhanced concentrations of nitrous acid measured at various sites both urban and rural during daytime was a surprise. Now the light-induced reaction between soil humic acid and nitrogen dioxide has been put forward as an explanation. The observed reaction rate of nitrous acid formation suggests that this production mechanism could be an important factor in the chemistry of the lower troposphere Nitrous acid is a significant photochemical precursor of the hydroxyl radical1,2,3,4,5,6,7,8,9,10,11,12,13, the key oxidant in the degradation of most air pollutants in the troposphere. The sources of nitrous acid in the troposphere, however, are still poorly understood. Recent atmospheric measurements7,10,11,12,13,14,15,16,17 revealed a strongly enhanced formation of nitrous acid during daytime via unknown mechanisms. Here we expose humic acid films to nitrogen dioxide in an irradiated tubular gas flow reactor and find that reduction of nitrogen dioxide on light-activated humic acids is an important source of gaseous nitrous acid. Our findings indicate that soil and other surfaces containing humic acid exhibit an organic surface photochemistry that produces reductive surface species, which react selectively with nitrogen dioxide. The observed rate of nitrous acid formation could explain the recently observed high daytime concentrations of nitrous acid in the boundary layer, the photolysis of which accounts for up to 60 per cent of the integrated hydroxyl radical source strengths3,6,7,8,9,10,11,12,13. We suggest that this photo-induced nitrous acid production on humic acid could have a potentially significant impact on the chemistry of the lowermost troposphere.

443 citations

Journal ArticleDOI
TL;DR: The ANAMMOX performance recovered under sulfide-S level of 8 mg L(-1) with a steady NRR increasing speed, linear relationship between the NRR and operation time, and the synchronic reduce in the specific ANAM MOX activity and the biomass extended the apparent doubling time of the nitrogen removal capacity and decreased biomass growth rate.

423 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202341
2022123
202129
202024
201931
201833