Nitropyridines alkaline

Oxidation of aminopyridines with Caro s acid gives nitropyridines the use of peroxy-trifluoroacetic acid leads to nitropyridine JV-oxides (60JOC1716). Oxidation with alkaline hypochlorite converts aminopyridines into symmetrical azopyridines, and azoxypyridines are formed by oxidation with persulfate (59YZ549). 

Rearrangement of the 2-ethoxycarbonylmcthyl-l,4,6-trimethylpyrimi-dinium salt with alcoholic aqueous methylamine gave the respective 2-mcthylaminopyridine-3-carboxylate (94MI2) (Scheme 39a). Similarly, in alkaline medium, even nonquaternized 2-methyl-5-nitropyrimidine gave 2-amino-5-nitropyridine (94MI2) (Scheme 39A). 

The oxidation of thiols is accelerated remarkably by traces of catalyst and this reaction forms the basis of petroleum sweetening processes. Although transition metal ions are the most effective catalysts, any additive capable of catalysing electron transfer accelerates the reaction. Nitrobenzene in dimethylformamide/potassium hydroxide [118], 2-nitro-thiophene, tetracyanoethylene, and 4-nitropyridine-N-oxide [118] are all good catalysts for the oxidation of 1-butane thiol. The alkaline hydrolysis of disulphides containing aryl, carbonyl, and alpha unsaturated groups also results in catalysis, apparently due to the setting up of a sulphinate—sulphenate redox cycle [119—121]. 

Pyridine is a tertiary amine its aqueous solution shows an alkaline reaction and precipitates the hydroxides of metals, some of which are soluble in an excess of the amine. Salts of pyridine like those of other amines form characteristic double salts with metallic halides. The ferrocyanide of pyridine and the addition-product of pyridine and mercuric chloride are difficultly soluble in water these compounds are used in the purification of the base. Pyridine is a very stable compound it can be heated with nitric acid or chromic acid without undergoing change but at 330° it is converted by a mixture of nitric acid and fuming sulphuric acid into nitropyridine, a colorless compound that melts at 41° and boils at 216°. At a high temperature pyridine is converted into a sulphonic acid by sulphuric acid. Chlorine and bromine form addition-products, e.g., C5H5N.CI2, at the ordinary temperature when these are heated to above 200°, substitution-products are formed. The hydroxyl derivative of pyridine is made by fusing the sulphonic acid with sodium hydroxide it resembles phenol in chemical properties. The three possible carboxyl derivatives of pyridine are known. The a-acid is called picolinic acid, the jS-acid nicotinic acid (664), and the 7-acid isonicotinic acid. 

Alkaline cleavages are rare. 3-Ethoxy-6-nitropyridine is very sensitive to alkali , but the result of the reaction is obscured by decomposition. What is happening in the conversion of 5-methoxy-l,2-dimethyl-4-pyridone into 5-hydroxy-l,2-dimethylpyrid-4-one by sodium and amyl alcohol i is not clear. 

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