Nitrous acid absorption spectra

In aqueous solutions of sulphuric (< 50%) and perchloric acid (< 45 %) nitrous acid is present predominantly in the molecular form, although some dehydration to dinitrogen trioxide does occur.In solutions contairdng more than 60 % and 65 % of perchloric and sulphuric acid respectively, the stoichiometric concentration of nitrous acid is present entirely as the nitrosonium ion (see the discussion of dinitrogen trioxide 4.1). Evidence for the formation of this ion comes from the occurrence of an absorption band in the Raman spectrum almost identical with the relevant absorption observed in crystalline nitrosonium perchlorate. Under conditions in which molecular nitrous... 

Treatment of cordycepin with nitrous acid, and subsequent hydrolysis of the deaminated product, yields hypoxanthine, indicating that in the adenine moiety the primary amino group is free and the glycosidic linkage involves C7 or C9. The close similarity between the ultraviolet absorption spectrum of cordycepin and those of 9-methyladenine and adenosine63 (9-/3-J>-ribofuranosyladenineMa) favors the latter possibility. The complete stereoisomeric description of cordycepin (XXVIII), formulation of which... 

A yellow solution is formed when nitrous acid is added to thiosulphate ion in water84. This is believed to be due to the formation of nitrosyl thiosulphate [O3SSNOI, although this has not been isolated and even in solution decomposition is fairly rapid. The equilibrium constant for its formation Wxno is 1.66 x 107 dm6 mol 2 at 25 °C and the UV-visible absorption spectrum is very similar to that of other S -nitroso compounds85. The rate constant for its formation is very large and is believed to represent a diffusion controlled process. Thiosulphate ion does appear to catalyse nitrosation but, over the range studied... 

Fox Talbot (24), an English scientist, found in 1834 that, with the aid of a prism, he could distinguish lithium from strontium, even though the salts of both give red flames (4, 26, 32). He stated that the dark lines previously observed by Sir David Brewster (33) in the spectrum of light which had passed through vapors of nitrous acid were caused by absorption of light (5,25). 

Figure 4.14 shows the absorption spectrum of gas-phase nitrous acid and Table 4.13 gives absorption... 

King, G.W. and Moule, D. (1962). The ultraviolet absorption spectrum of nitrous acid in the vapor state, Can. J. Chem. 40, 2057-2065. 

Vasudev R., Absorption spectrum and solar photodissociation of gaseous nitrous acid in the actinic wavelength region. Geophys Res. Lett 17, 2153, 1990. 

Crystals from water + acetone, mp 196-200". [alff -47,5 (c = 2, 2% NaOH) -26.0 (c = 2, 10% HCI). pK, -- 3.8 pKj — 6.2. aM (molar absorbancy) 15.4 X I03 at 259 nm (pH 7.0). Readily sol in boiling water. The compound is readily deaminated by nitrous acid to form inosinic acid less rapidly hydrolyzed than 3 -adenylic acid by sulfuric acid. Furfural is formed only in traces On distillation with 20% HCI, cf. Levene, Bass, Nucleic Acids (New York, 1931) pp 230-232. Absorption spectrum Kalckar. foe. cir. thERap cat-. Nutrient. 

The plasma level of paracetamol can be determined by gas-liquid chromatography, by its UV absorption spectrum following extraction, and by its colorimetric reaction with nitrous acid to form a yellow coloured nitrophenol (the Glynn and Kendal method). Paracetamol can be detected in urine by a screening test which consists of its hydrolysis to /7-aminophenol, followed by its reaction with o-cresol and ammonia to form a blue in-dophenol. 

Cox, R.A., Derwent, R.G. The ultra-violet absorption spectrum of gaseous nitrous acid. J. Photochem. 6, 23-34 (1976)... 

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