GB340509A - Improvements in the manufacture and production of anthraquinone and homologues of the same - Google Patents

Abstract

Anthraquinone and its homologues are obtained by treating the condensation products from 1 molecular proportion of benzoquinone and 2 molecular proportions of the same 1 : 3-butadiene, or the rearrangement products thereof, or the tetrahydroanthrahydroquinones, tetrahydroanthraquinones or corresponding quinhydrones obtainable therefrom by mild dehydrogenation as described in the parent Specification, with a metal salt, the cation of which is capable of assuming a lower valency, e.g. a ferric, cupric or mercuric salt, in an acid medium. The metal salt may be employed in quantities at least equal to those theoretically necessary for the conversion into anthraquinones, or smaller quantities may be employed if the reaction is carried out in the presence of agents, such as oxygen or air, capable of reforming the cations of higher valency. The concentration of the acid may be varied within wide limits; in some cases the acid produced by hydrolysis of the aqueous solutions of the metal salts is sufficient. In examples (1) the condensation product from benzoquinone and 1 : 3-butadiene (2 mols.) is heated with ferric chloride in glacial acetic acid to form anthraquinone, (2) the rearrangement product described in example 29 of the parent Specification is heated with a solution of ferric chloride, ferric sulphate, cupric chloride, or mercuric acetate under pressure to form anthraquinone; other cupric salts such as cupric acetate may also be used, and acids, such as acetic acid, may be added to the solutions, and (3) the condensation product from benzoquinone and isoprene (2 mols.) is heated with ferric chloride solution under pressure; 2 : 7-dimethylanthraquinone is formed.