Nitrous acid constitution

Deamination of aminoaldohexoses with nitrous acid constitutes the oldest route of access to the 2,5-anhydroaldohexoses (see the Introduction). It is only in recent years, however, that the results obtained by this method could be rationalized on a theoretical basis as a consequence of concomitant developments in certain other areas of organic chemistry. 

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... 

The first investigations on the constitution of cystine are those of Dewar and Gamgee in 1871, who, on treating cystine with nitrous acid, obtained an acid which they thought was pyruvic acid, CH3. CO. COOH,... 

Such being the rational formula of leuoin, its transformation into leueio acid by nitrous acid determines the constitution of leuoio aeid... 

Tlic foregoing sulphonic acids are all known, at least in the form of their salts, and are obtainable, directly or indirectly, by the interaction of sulphurous and nitrous acids or their salts. Isomerides of some of the sulphonic acids are also known, for example, hydroxylaminc-iso-sulphonic acid, NH. O.SOo.OH,1 which is obtainable by the action of chlorosulphonic acid on hydroxylamine hydrochloride. As its constitution indicates, this isomeric acid is in reality a derivative of permono-sulphuric acid (see p. 192). 

The full discussion of these diazo compounds with the explanation of their constitution will come later but, as they are involved in the preparation of some of the azo compounds, it is necessary to introduce the subject at this time. They are formed by the action of nitrous acid... 

What now is the constitution of these diazo compounds The facts thus far considered and which must be explained by an accepted constitutional formula are, (i) Their formation by the action of nitrous acid on a primary- amine, (2) Their conversion into azo, amino azo, hydroxy azo and hydrazine compounds and (3) the basic character of the hydroxy compound, diazo benzene, and the true salt character of the compounds formed with strong acids. 

The constitution is proven by the fact that the compound may be prepared from para-nitroso di-methyl aniline which is the characteristic product of the reaction of nitrous acid on di-methyl aniline (p. 553). 

Quinone Oximes.—The most interesting of the derivatives of quinones are the oximes. As stated in the discussion of the ketone structure for quinones one of the proofs for this constitution is the fact that benzoquinone forms both a mono-and a di-oxime when treated with hydroxyl-amine. The mono- oxime of benzoquinone would have the structure as written below and as given on page 638. Now as previously mentioned, (p. 628), para-nitroso phenol, which is made by the action of nitrous acid upon phenol and the constitution of which is established by other methods of synthesis, (p. 627), proves to be one and the same compound with this mono-oxine of para-benzoquinone, the constitution of which is likewise established by the above reaction of hydroxyl amine upon quinone. This is explained by a rearrangement as shown in the following ,... 

Stereochemical Configuration. Deamination by means of nitrous acid transforms adenosine into inosine (ribosyl-hypoxanthine), and guanosine into xanthosine (ribosyl-xanthine). These four purine nucleosides are hydrolyzed rapidly, and with equal ease, by dilute mineral acids. They are also all hydrolyzed by the same enzyme, so it is reasonable to presume that they are similarly constituted as regards the stereochemical disposition at the sugar-base link. Whether this is of the a- or i8-configuration is still unknown. 

Only the /8-nitro-compound (of the constitution OH OH NO3) possesses technical interest. It may be obtained by treating alizarin, suspended in toluene or nitrobenzene, with nitrous acid, or by cautious nitration of alizarin dissolved in glacial acetic acid with nitric acid. 

On heating indigo blue with acetic anhydride, sodium acetate, and zinc powder, a diacetylindigo white is obtained. On oxidation with nitrous acid in presence of acetic acid, diacetylindigo blue is formed. This compound forms small glittering red crystals, soluble in benzene with a beautiful red colour. Its constitution is expressed by the formula ... 

It constitutes a voluminous, reddish, ciystalline powder readily soluble in water, ether, alcohol, and chloroform. With nitrous-acid, or the nitrites (sp. aeth. nitr.) in the presence of free acids, it forms a green, crystalline, sparingly soluble nitro-derivative which... 

Tertiary amines which contain both alkyl and aryl radicals resemble, in general, the aliphatic tertiary amines in their chemical behavior. The two classes are sharply differentiated, however, by their behavior with nitrous acid. While the aliphatic amines are either unaffected or oxidized by this reagent, the aromatic amines are converted into nitroso compounds. The nitroso derivatives of a secondary aromatic amine has a structure analogous to that of the nitroso derivatives of aliphatic amines. The constitution of nitroso-methylaniline and that of nitroso-dimethylamine are expressed, respectively, by the following formulas —... 

The principal by-products formed during the mixed-acid mononitration of toluene are nitrous acid and nitrated phenolic compounds, of which 2, 6 dinitro p-cresol constitutes etbout 80%. 

In the blurredness of his strange theory Blomstrand discussed the properties and constitution of all types of compounds in the second half of his book. In discussing nitrogen compounds he had to explain why nitrous acid decomposes to form nitrogen oxide (NO) with a divalent rather than an od alent nitrogen atom ... 

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