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THIAZOLES, in organic chemistry, a series of heterocydic compounds containing the grouping shown below; the replaceable hydrogen atoms in which are designated o, /3 and p. They are prepared by condensing thio-amides with a-haloid ketones or aldehydes, the thio-amide reacting as the tautomeric thio-imino acid. Amino derivatives similarly result from thio-ureas and a-haloid ketones; the oxy derivatives from a-sulphocyanoketones by the action of caustic alkali; and the carboxylic adds from chloro-aceto-acetic ester, etc. and thioamides. The thiazoles are somewhat basic in character, and combine with the alkyl iodides to form thiazolium iodides.

Dihydrothiazoles, or thiazolines, are obtained by condensing ethylene dibromides with thio-amides; by the action of /S-haloid alkylamines on thio-amides (S. Gabriel, Ber., 1891, 24, p. 783; 1896, 29, p. 2610) ; and by the action of phosphorus pentasulphide on acyI-0-bromalkylamides (A. Salomon, Ber., 1893, 26, p. 1328). Thy are much less stable than the thiazoles. The benzotbiazoles are a series of weak bases formed by condensing carboxylic acids with ortho-aminothiophenols (A. W. Hofmann, Ber., 1880, 13, p. 1224), by heating the acid anilides with sulphur or by the oxidation of thio-anilides. On fusion with caustic alkalis they decompose into their constituent aminothiophenol and acid. Derivatives of this group are important as substantive cotton dyestuffs.

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Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)

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