Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

QUINIZAKIN 335
collecting the substance at the pump, wash with water and dry.
Recrystallise from glacial acetic acid. Fine pale yellow needles ;
melting point 285°.
When completely pure the compound is colourless. Compare with
benzoquinone and naphthoquinone.
Anthraquinone is reduced by heating with sodium hydroxide and
zinc dust: the deep red disodium salt of anthraquinol goes into solution.
Carry out the reduction and filter the red solution. Anthraquinone
soon separates again from the nitrate on exposure to the air.
Details of the interesting desmotropic phenomena exhibited by the
hydroxyanthracenes are given by K. H. Meyer (Annalen, 1911, 379, 37).
Meso-hydroxy- and dihydroxyanthracene exist in two forms, a genuine,
coloured acidic enol which fluoresces in solution and a colourless,
neutral keto-iovm.
OH
\
H H
H OH
Anthranol •—•->-
Anthrone Anthraquinol -