Azinic acid

The nitro form is much more stable than the aci form in sharp contrast to the parallel case of nitroso-oxime tautomerism, undoubtedly because the nitro form has resonance not found in the nitroso case. Aci forms of nitro compounds are also called nitronic acids and azinic acids. 

The pronounced electron-withdrawing nature of the 1,2,5-thia-diazole ring is evidenced by the fact that its carboxylic acid derivatives are highly acidic. The titration curve of the dicarboxylic acid exhibits two breaks with and Kai, equal to 1.59 and 4.14, respectively. The monocarboxylic acid is also strongly acidic and has a piTa of 2.47, comparable to that of ornitrobenzoic acid 2.18) and pyrazine-2-carboxylic acid (pifa 2.80). In general the piTa values for the thiadiazole carboxylic acids are in fair agreement with the pica s of the corresponding p3U azine acids (see Table II). 

Azo dyes, azines. acid anthraquinone dyes Azo dyes Azo dyes... 

Acid amide herbicides Acid anhydrides Acid azine dyes Acid-base catalysis Acid-base chemistry Acid Black [1064-48-8]... 

Carbon—nitrogen double bonds in imines, hydrazones, oximes, nitrones, azines, and substituted diazomethanes can be cleaved, yielding mainly ketones, aldehydes and/or carboxyHc acids. Ozonation of acetylene gives primarily glyoxal. With substituted compounds, carboxyHc acids and dicarbonyl compounds are obtained for instance, stearoHc acid yields mainly azelaic acid, and a smaH amount of 9,10-diketostearic acid. 

Sodium dichromate and various chromic salts are employed in the textile industry (195,196). The former is used as an oxidant and as a source of chromium, for example, to dye wool and synthetics with mordant acid dyes, oxidi2e vat dyes and indigosol dyes on wool, aftertreat direct dyes and sulfur dyes on cotton to improve washfastness, and oxidi2e dyed wool. Premera11i2ed dyes are also employed. These are hydroxya2o or a2omethine dyes in which chromium or other metals are combined in the dye (see Azine dyes DYES Azo dyes). 

The repeatedly attempted commercialization of hydrazine synthesis via dialkyldiaziridines required hydrolysis of the latter without the use of stoichiometric amounts of acid. Catalytic amounts of acid, e.g. an acidic ion exchanger, were used in the presence of excess ketone, yielding the azine as an intermediate, which could be hydrolyzed without acid above 100 °C to give hydrazine hydrate and the ketone (62GEP1126395, 71JAP7102008). 

H-Bond Acceptor-Donor (HBAD) Phenols Aromatic acids Aromatic amines Alpha H nitriles Iniines Monocarboj hc acids Other monoacids Peracids Alpha H nitros Azines Primary amines Secondary amines n-alcohols Other alcohols Ether alcohols... 

Hydroxy-pyridines (8) and -azines are both weak acids (cf. phe-... 

Acid catalysis increases reactivity both para and ortho to the site of protonation. Coulombic attraction of an anionic nucleophile to the vicinity of the positive center will to some extent remove the proton (65), forming the less reactive azine and the nucleophile s... 

Hydrogen bonding with protic solvents or reagents occurs widely in azines even when they are not appreciably basic and the protic compounds are very poor acids. The latter do not have to be present... 

The effect of partial or complete cationization might be expected to be greater for a mono-azine than for a poly-azine in which the activation is greater. However, the effect in acid-catalyzed aminations was... 

Alkylthio, arylthio, and thioxo. The thioxo group in pyrimidine-2,4-dithione can be displaced by amines, ammonia, and amine acetates, and this amination is specific for the 4-position in pyrimidines and quinazolines. 2-Substitution fails even when a 5-substituent (cf. 134) sterically prevents reaction of a secondary amine at the 4-position. Acid hydrolysis of pyrimidine-2,4-dithione is selective at the 4-position. 2-Amination of 2-thiobarbituric acid and its /S-methyl derivative has been reported. Under more basic conditions, anionization of thioxo compounds decreases the reactivity 2-thiouracil is less reactive toward hot alkali than is the iS-methyl analog. Hydrazine has been reported to replace (95°, 6 hr, 65% 3deld) the 2-thioxo group in 5-hexyl-6-methyl-2-thiouracil. Ortho and para mercapto- or thio- azines are actually in the thione form. ... 

Factor b above is discussed in Sections II, B, 1 II, B, 4 and II, C. A hydrogen-bonded structure such as 221 can account for the facile reaction of 5-bromouracil or for the unique, so-called hydrolyzability of carboxymethylthio-azines (237). The latter may also react via the intramolecular mechanism indicated in 136. The hydrogen-bonded transition state 238 seems a reasonable explanation of the fact that 3,4,6- and 3,4,5-trichloropyridazines react with glacial acetic acid selectively to give 3-pyridazinones while other nucleophiles (alkoxides, hydrazine, ammonia, or sulfanilamide anion) react at the 4- and 5-positions. In this connection, 4-amino-3,5-dichloro-pyridazine in liquid hydrazine gives (95°, 3hr, 60%yield)the isomer-... 

Methylthio and 3-carboxymethylthio substituents are easily hydrolyzed, the latter much more readily (cf. 136 and 237) but only in acid. A 3-sulfonic acid group (cf. 314) is readily displaced, especially in acid solution. Conversion of 3-amino-5,6-diphenyl-as-triazine into the 3-oxo analog with alkali proceeds rather easily (100°, < 4 hr), as it does with other amino-azines. 

---