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Nitrous Acid (nitrous + acid)
Selected AbstractsChemInform Abstract: Reaction of Esters of 2-Arylcyclopropanecarboxylic Acids with Nitrous Acid.CHEMINFORM, Issue 5 20103-Ethoxycarbonylisoxazoles., 5-dihydroisoxazoles, Synthesis of Aryl-Substituted 3-Ethoxycarbonyl- Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Oxidative Cyclization of Arenecarbaldehyde 4-Methylquinolin-2-ylhydrazones to 3-Aryl-9-methyl-1,2,4-triazolo[4,3-a]quinolines Using Nitrous Acid: A Reinvestigation.CHEMINFORM, Issue 40 2003Om V. Singh Abstract For Abstract see ChemInform Abstract in Full Text. [source] Indolizines, triazolo[4,3- a]pyridines, benzimidazo[1,2- d]oxadiazoles, and pyrazolo[1,5- c]triazoles via nitrogen and sulfur ylidesHETEROATOM CHEMISTRY, Issue 6 2004Kamal M. Dawood The pyridinium salts 2a,b reacted with dimethyl acetylenedicarboxylate (DMAD) to give the indolizine derivatives 6a,b. Pyridinium salts 2a,b also reacted with pyrazole-5-diazonium salt to afford the hydrazonoyl bromides 8a,b, which on treatment with aqueous ethanolic sodium carbonate furnished the 8aH -1,2,4-triazolo[4,3- a]pyridine 10. When sulfonium bromide 11 was treated with nitrous acid and with pyrazole-5-diazonium salt, it afforded the new hydroximoyl and hydrazonoyl halides 12 and 17, respectively. Compound 12 reacted with 2-methylthiobenzimidazole to furnish benzimidazo[1,2- d]-1,2,4-oxadiazole derivative 14. Treatment of either 12 with 3-phenyl-5-aminopyrazole or 17 with triethylamine resulted in the formation of the same product: pyrazolo[1,5- c]-1,2,4-triazole derivative 16. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:432,436, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20037 [source] Thermochemistry for enthalpies and reaction paths of nitrous acid isomersINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2007Rubik Asatryan Recent studies show that nitrous acid, HONO, a significant precursor of the hydroxyl radical in the atmosphere, is formed during the photolysis of nitrogen dioxide in soils. The term nitrous acid is largely used interchangeably in the atmospheric literature, and the analytical methods employed do not often distinguish between the HONO structure (nitrous acid) and HNO2 (nitryl hydride or isonitrous acid). The objective of this study is to determine the thermochemistry of the HNO2 isomer, which has not been determined experimentally, and to evaluate its thermal and atmospheric stability relative to HONO. The thermochemistry of these isomers is also needed for reference and internal consistency in the calculation of larger nitrite and nitryl systems. We review, evaluate, and compare the thermochemical properties of several small nitric oxide and hydrogen nitrogen oxide molecules. The enthalpies of HONO and HNO2 are calculated using computational chemistry with the following methods of analysis for the atomization, isomerization, and work reactions using closed- and open-shell reference molecules. Three high-level composite methods G3, CBS-QB3, and CBS-APNO are used for the computation of enthalpy. The enthalpy of formation, ,Hof(298 K), for HONO is determined as ,18.90 ± 0.05 kcal mol,1 (,79.08 ± 0.2 kJ mol,1) and as ,10.90 ± 0.05 kcal mol,1 (,45.61 ± 0.2 kJ mol,1) for nitryl hydride (HNO2), which is significantly higher than values used in recent NOx combustion mechanisms. H-NO2 is the weakest bond in isonitrous acid; but HNO2 will isomerize to HONO with a similar barrier to the HONO bond energy; thus, it also serves as a source of OH in atmospheric chemistry. Kinetics of the isomerization is determined; a potential energy diagram of H/N/O2 system is presented, and an analysis of the triplet surface is initiated. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 378,398, 2007 [source] Kinetic study of the nitrosation of 1,3-dialkylureas in aqueous-perchloric acid mediumINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2004Guillermo González-Alatorre The kinetics of the nitrosation of 1,3-dimethyl (DMU), 1,3-diethyl (DEU), 1,3-dipropylurea (DPU), 1,3-dibuthyl (DBU), and 1,3-diallylurea (DAU) were studied in a conventional UV/vis spectrophotometer in aqueous-perchloric acid media. The kinetic study was carried out using the initial rate method. The reaction rate observed was where Ka is the acidity constant of nitrous acid. The diureas exhibited the reactivity order DMU , DEU > DPU > DAU, which can be interpreted as a function of the steric impediment generated by the R alkyl group in the rate controlling step. A probable relationship between both the chemical reactivity and structure of the nitrosable substrate with the biological activity of the N-nitroso compounds generated is proposed. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 273,279, 2004 [source] Studies with 1-functionally substituted alkyl azoles: Novel synthesis of functionally substituted azolylbenzimidazoles and functionally substituted azolyl-1,2,4-triazolesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2002Mohamed Abdel-Megid ,-Azolylacetophenones 1 and 2 react with dimethylformamide dimethylacetal to yield enaminones 7,8 that were converted into azolylazoles via reaction with hydrazine and with hydroxylamine. Compounds 1,2 also coupled with aromatic diazonium salts to yield arylhydrazones and reacted with nitrous acid to yield corresponding oximes. [source] The Molecular Mechanism of Tropospheric Nitrous Acid Production on Mineral Dust SurfacesCHEMPHYSCHEM, Issue 10 2008R. Joel Gustafsson Dr. Tropospheric model: The formation of tropospheric nitrous acid on mineral surfaces does not involve an N2O4 intermediate. Well-defined surface conditions achievable under ultra-high vacuum are utilised to show that the hydrolysis reaction involves dissociated water (see figure). [source] Kinetics and mechanism of the oxidation of carbon by NO2 in the presence of water vaporINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2009M. Jeguirim The kinetics and mechanism of the oxidation of carbon by NO2 in absence and presence of water vapor were studied in a fixed bed reactor. The rate of carbon oxidation by NO2 is enhanced in the presence of water vapor in the range of temperature 300,400°C. The benefit effect of water is attributed to the intermediate formation of traces of nitric and nitrous acids, which enhance the rate of the carbon oxidation without modifying the global mechanism reaction. Therefore, water acts as a catalyst for the carbon oxidation by NO2. A kinetic mechanism derived from this parametric study shows a decrease in the activation energy of carbon oxidation by NO2 in the presence of water vapor. This result is in agreement with the experimental observation. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 236,244, 2009 [source] | ||||||||||