Hydrocarbons with Seven Linearly Annellated Rings

Abstract

A fusion of anthraquinone-2,3-dicarboxylic anhydride with leucoquinizarin and 5–10% of aluminium chloride gives 5,7,16,18-tetrahydroxyheptacene-6.17,9.14-diquinone (I). It cannot be reduced by a zinc-dust distillation. However, reduction was achieved via the chloro compound (II) which was obtained with phosphorus pentachioride. A reduction product was prepared from it using an alkaline solution of sodium dithionite. This derivative of the diquinone (III) was further reduced with hydriodic acid and red phosphorus at 200° and yielded the hexahydroheptacene (IV). Its structure was established by its absorption spectrum which showed it to be a benzene derivative.¹ Boiling nitrobenzene dehydrogenated it to 5,18-dihydropentacene (V). This is blue-violet and has the absorption spectrum of a pentacene derivative. Like pentacene it reacts rapidly with maleic anhydride and is photo-oxidizable in solution. Sublimation in vacuo isomerizes the dihydro compound (V) to (VI). The latter has the absorption spectrum of a tetracene derivative. The same hydrocarbon is produced when the hexahydro compound (IV) is dehydrogenated by sublimation over copper.²