Claus, Ber., 1873, 6, p. 723); by passing aniline vapour over lead oxide, or by the oxidation of dihydrophenazine, which is prepared by heating pyrocatechin with orthophenylene diamine (C. Ris, Ber., 1886, 19, p. 2206).
All four mono-hydroxyxanthones are known, and are prepared by heating salicylic acid with either resorcin, pyrocatechin or hydroquinone; they are yellow crystalline solids, which act as dyestuffs.
Orthophenylene diamine, C 6 H 4 (NH2)2, crystallizes from water in plates, which melt at 102 -103° C. and boil at 256-258° C. When heated with io% hydrochloric acid to 180° C. it yields pyrocatechin (Jacob Meyer, Ber., 1897, 30, p. 2569).
Jour., 1901, 26, p. to) attempted to prepare this compound by the action of iodine on the lead salt of pyrocatechin suspended in chloroform.
Willstatter (Ber., 1904, 37, p. 4744), by dissolving pyrocatechin in absolute ether containing ignited sodium sulphate and then adding dry silver oxide, obtained the quinone in dark red crystalline plates which decompose between 60° and 70° C.
Vorlander); when fused with caustic potash, resorcin yields phloroglucin, pyrocatechin and diresorcin.
PYROCATECHIN, or Pyrocatechol, ortho-dioxybenzene, C 6 H 4 (OH) 2, first prepared in 1839 by H.
Pyrocatechin crystallizes in white rhombic prisms, which melt at 104° and boil at 245°; it is readily soluble in water, alcohol and ether.
Guaiacol may be obtained directly from beechwood tar, from pyrocatechin by methylation with potash and potassium methyl sulphate at 180°, or from anisol by nitration, reduction of the ortho-nitroanisol to amino-anisol, which is then diazotized and boiled with water.
Many other pyrocatechin derivatives have been suggested for therapeutic application.
Pyrocatechin readily condenses to form heterocyclic compounds; cyclic esters are formed by phosphorus trichloride and oxychloride, carbonyl chloride, sulphuryl chloride, &c.; whilst ortho-phenylenediamine, o-aminophenol, and o-aminothiophenol give phenazine, phenoxazine and thiodiphenylamine.