178 



REPORT — 1903. 



(in. p. 190°). Care is necessary, however, as otherwise the action may go 

 further ; a pentabromo-dinaphthyl-diquinone, C2oH_r,Br504, then separates 

 as a yellow crystalline insoluble powder. This compound is formed accord- 

 ing to the equation 2C,oH;jBrj02 = HBr + C.joHr.Bi'jOi- -A. similar case 

 of condensation was mentioned in last year's I'eport. 



Unlike the keto- chlorides, the keto-bromides do not give substituted 

 naphthols when reduced either with stannous chloride and chlorhydric 

 acid or with iodhydric acid (d. I'D) ; the .sole product is 4 ; 6-di- 

 bromo-1 : ;i-dihydroxynaphthalene, 



OH 



OH 



which is also obtained by reducing 4 : G-dibromo-l : 2-naphthaquinone. 

 The corresponding diacetate, C,oH4Br2(C)Ac)o, crystallises in large 

 prisms, melting at 157'^. 



The keto-bromide is probably first transformed into 



The discovery of 4 : 6-dibromo-2-keto naphthalene! -dibromide makes 

 it possible to explain the production of 4 : 6-dibromo-l : 2-naphtha- 

 quinone during the decomposition by heat of the nitro-keto- compound of 

 1 : 6-dibromo-^-naphthol. That the dibromo-quinone could not be formed 

 by a mere bromination of G-monobromo-/j-iiaphthaquinone initially 

 produced is shown by the fact that this bromination cannot be i-ealised in 

 practice. The real explanation is that the bromine initially split off from 

 the nitro-keto- compound brominates the undecomposed remainder of this 

 substance, first displacing NOo * a subsequent decomposition produces the 

 4 : 6-dibromo-quinone. 



O 



NO., Br 



Br, 



O 



+ 



Br 



