Nitrous acid properties, chemical

Nor can there be any question of real tautomerism in the case of phenol. In its chemical properties phenol resembles the aliphatic enols in all respects. We need only recall the agreement in the acid character, the production of colour with ferric chloride, and the reactions with halogens, nitrous acid, and aromatic diazo-compounds (coupling), caused by the activity of the double bond and proceeding in the same way in phenols and aliphatic enols. The enol nature of phenol provides valuable support for the conception of the constitution of benzene as expressed in the Kekule-Thiele formula, since it is an expression of the tendency of the ring to maintain the aromatic state of lowest energy. In this connexion the hypothetical keto-form of phenol (A)—not yet obtained—would be of interest in comparison with... 

A 2-amino group in chroman is more labile than its isomers and is hydrolyzed to the alcohol by acids for example both the amines (699) and (700) give the corresponding alcohols by treatment with nitrous acid and 50% hydrochloric acid, respectively. 6-Amino-chromans are of interest because of their chemical and biological resemblance to the tocopherols. The tocopheramines (701 R1, R2, R3 = H or Me) show antioxidant and other properties of the corresponding phenols and are no more toxic. They may be obtained by catalytic or chemical reduction of the nitrochromans (81HC(36)189). 

As a result of its unique structure and properties, the NO molecule exhibits a wide variety of reactions with various chemical species. In particular, it readily releases an electron in the antibonding tt orbital to form the stable nitrosyl cation NO+, increasing the bond order from 2.5 to 3.0, so that the bond distance decreases by 9 pm. The NO species in an aqueous solution of nitrous acid, HONO, is NO+ ... 

A mutagen is a physical agent or chemical reagent that causes mutations. For example, nitrous acid reacts with some DNA bases, changing their chemistry and hydrogen bonding properties, and is a mutagen. 

The chemical properties of nitroestrones are much the same as those of simpler aromatic compounds. The nitro group in 19-1 can, for instance, be converted to the aniline 21-1 for example by reduction with tin and acid treatment of the resulting aniline with nitrous acid then gives the diazonium salt 21-2 (Scheme 3.21). Photolysis of that salt in methanol leads to formation of 2-methoxyestrone, (21-3), in this case confirming the structure of one of the metabolites of estradiol. 

Low-molecular-weight heparins ( 4500 Da, or 15 monosaccharide units) are isolated from standard heparin by gel filtration chromatography, precipitation with ethanol, or partial depolymerization with nitrous acid and other chemical or enzymatic reagents. Low-molecular-weight heparins differ from standard heparin and from each other in their pharmacokinetic properties and mechanism of action ("see below). The biological activity of low-molecular-weight heparin is generally measured with a factor Xa inhibition assay, which is mediated by antithrombin. 

Chemical Reaction Mechanism. Fairly detailed conclusions can often be made concerning the chemical and spin properties of the radical pair intermediates, properties which can be difficult to obtain by other methods. Lehnig et al. report CIDNP studies of the reaction of nitrous acid with hydrogen peroxide... 

Shortly after Perkin had produced the first commercially successful dyestuff, a discovery was made which led to what is now the dominant chemical class of dyestuffs, the azo dyes. This development stemmed from the work of Peter Griess, who in 1858 passed nitrous fumes (which correspond to the formula N203) into a cold alcoholic solution of 2-aminO 4,6 dinitrophenol (picramic acid) and isolated a cationic product, the properties of which showed it to be a member of a new class of compounds [1]. Griess extended his investigations to other primary aromatic amines and showed his reaction to be generally applicable. He named the products diazo compounds and the reaction came to be known as the diazotisation reaction. This reaction can be represented most simply by Scheme 4.1, in which HX stands for a strong monobasic acid and Ar is any aromatic or heteroaromatic nucleus. 

Nitramine has explosive properties but it is not of any practical value for many reasons, primarily because of its high reactivity which impairs its chemical stability. It decomposes at a temperature as low as its melting point. At room temperature it decomposes slowly, to form nitrous oxide and water. On heating to 60-65°C decomposition occurs in an aqueous solution. It decomposes explosively on contact with concentrated sulphuric acid. ... 

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