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PYROCATECHIN, or PYROCATECHOL

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Originally appearing in Volume V22, Page 693 of the 1911 Encyclopedia Britannica.
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PYROCATECHIN, or PYROCATECHOL , ortho-dioxybenzene, See also:C6H4(OH)2, first prepared in 1839 by H. Reinsch on distilling catechin (the juice of See also:Mimosa See also:catechu); occurs See also:free in kino and in beechwood See also:tar; its sulphonic See also:acid is See also:present in the urine of the See also:horse and See also:man. It results in the alkaline See also:fusion of many resins, and may be prepared by fusing ortho-phenolsulphonic acid, o-chlorphenol, o-bromphenol, and o-phenoldisulphonic acid with potash, or, better, by See also:heating its methyl See also:ether, guaiacol, C6H4(OH) (OCH3), a constituent of beechwood tar, with hydriodic acid. Pyrocatechin crystallizes in See also:white rhombic prisms, which melt at 104° and See also:boil at 245°; it is readily soluble in See also:water, See also:alcohol and ether. Ferric chloride gives a See also:green coloration with the aqueous See also:solution, whilst the alkaline solution rapidly changes to a green and finally to a See also:black See also:colour on exposure to the See also:air. It reduces See also:silver solutions in the See also:cold and alkaline See also:copper on heating. Guaiacol may be obtained directly from beechwood tar, from pyrocatechin by methylation with potash and See also:potassium methyl sulphate at 18o°, or from anisol by nitration, reduction of the ortho-nitroanisol to amino-anisol, which is then diazotized and boiled with water. It melts at 28° and boils at 25o°. It is employed in See also:medicine as an expectorant. The dimethyl ether or veratrol i phosphate (PbCl)Pb4(PO4)3, sometimes occurring in sufficient is also used in medicine. Many other pyrocatechin derivatives have abundance to be See also:mined as an ore of See also:lead. been suggested for therapeutic application. Guaiacol carbonate is known as duotal, the phosphate as phosphatol, the phosphite as guaiaco-phosphal; phosphotal is a mixture of the phosphites of See also:creosote phenols.

The valerianic ester of guaiacol is known as geosote, the benzoic as benzosol, the salicylic as guaiacolsalol, while the See also:

glycerin ether appears as guaiamar. Pyrocatechin readily condenses to See also:form heterocyclic compounds; cyclic See also:esters are formed by See also:phosphorus trichloride and oxychloride, carbonyl chloride, sulphuryl chloride, &c.; whilst ortho-phenylenediamine, o-aminophenol, and o-aminothiophenol give See also:phenazine, phenoxazine and thiodiphenylamine.

End of Article: PYROCATECHIN, or PYROCATECHOL

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