Orcin

Orcin, or 3,5-dihydroxytoluene, C6H3(CH3)(OH)2, is an organic compound found in many lichens including Rocella tinctoria and Lecanora, and formed by fusing extract of aloes with potash.

It may be synthesized from toluene; more interesting is its production when acetone dicarboxylic ester is condensed with the aid of sodium. It crystallizes in colorless prisms with one molecule of water, which redden on exposure to air. Ferric chloride gives a bluish-violet coloration with the aqueous solution. Unlike resorcinol it does not give a fluorescein with phthalic anhydride. Oxidation of the ammoniacal solution gives orcein, C28H24N2O7, the chief constituent of the natural dye archil. Homo-pyrocatechin is an isomer (CH1: OH: OH= 1 3 :4), found as its methyl ether (creosol) in beech-wood tar.