TETRABROMO-DIPHENO-OUINONE. 



By James Moir, M.A., D.Sc. 



Some of the history of this beautiful and puzzling substance 

 has already been given in a preliminary note written seven years 

 ago.* It forms deep scarlet needles, generally minute, with a 

 blue metallic lustre, and is insoluble in all solvents, although it 

 dissolves sufficiently in the ketonic solvents to colour them orange- 

 red. On heating, it decomposes without melting. Its constitution 

 is analogous to that of coerulignone, but its behaviour differs, 

 inasmuch as part of the bromine, though apparently present in 

 attachment to benzene rings, is remarkably reactive, and thus 

 capable of leaving the rings. Accepting the constitution given by 

 its discoverer, Magatti.f and subsequent workers on dipheno- 

 quinone, its constitution would be — 



Br 



Its general behaviour, however, suggests an ortho-quinonoid 

 linkage and a higher molecular weight, and the author tenta- 

 tively suggests that it may be an oxonium bromide of double mole- 

 cular weight, with part of the bromine displaced so as to be more 

 under the influence of the oxygen than of the ring, thus : — 



OBr 

 BrO 



It is made by oxidising tetrabromo-diphenol with almost any 

 oxidising agent, so long as the solvent is indifferent to oxidation. 

 The author has also discovered that the same substance appears 

 under another name, viz., bromrosochinon, having been obtained 

 by Baeyer by oxidising tetrabromo-phenolphthalein with nitro- 

 sulphuric acid. In the same way, the substance described by 

 Baeyer as bromhydrorosochinon is really ordinary tetrabromo- 

 diphenol. Baeyer probably missed this discovery by assuming a 

 wrong arrangement of the bromines in the substances (see under), 

 and Beilstein repeats this wrong orientation of the substituents in 

 tetrabromo-phenolphthalein. The bromines are, of course, in the 

 3 and 5 positions and OH in 4, in all these compounds. 



* Proc. Chem. Sec, 1906, p. tio. 

 f Bcrichte, 1880, p. 22s. 



