258 DERIVATIVES OF DIPHENOOUINONE. 



of its quinhydrone eventually results. It is considerably more 

 soluble in organic solvents than dicresoquinone. 



0.2218 used ii.ggcc-^Ag (see Proc. 1906, 262 and 1907 

 No. 330) - > Br =: 43.25% 



0.0838 used 2.62CC ~ SnCL2 by difference against a blank, 

 both done in presence of alcoliol — H = 0.55% 



^14 ^10 ^1 ^^'i requires Br = 43.2, H = 0.54% 



The reduction-product is pure dibromodicresol, ///./>. 184°, 

 and an almost quantitative yield can be obtained, as it is prac- 

 tically insoluble in cold water. 



ATagatti's method — addition of a few drops of yellow nitric 

 acid to the acetic acid solution of dibromodicresol — was also tried ; 

 the product was similar in appearance, but the bromine analyses 

 w^ere all low. It has also been obtained by two aqueous methods : 

 (a) dibromodicresol is converted into a gelatinous form by 

 solution in soda and addition of mineral acid ; on boiling this with 

 excess of ferric salt and then adding a little CrOa, the substance 

 changes through the olive quinhydrone into the microcrystalline 

 quinone : it is boiled to complete the crystallisation, and after 

 collecting washed with 50% alcohol to dissociate any trace of 

 quinhydrone. Found in this specimen, a brick-red crystalline 

 powder, 44.01% Br: (b) the jelly above described is boiled with 

 acid and a mixture of (KBrO -f- 5KBr) in solution gradually 

 run in. Found 4^.98% Jh". The yields in both cases are about 

 95%- 



All the specimens give with concentrated sulphuric acid a 

 scarlet coloration, fuchsine-red when only traces are taken. The 

 spectrum of this is indefinite, being a broad absorption-band 

 over the whole of the green, deepest between b and F. 



What appears to be the ^r(7//.y-variety of this compound is 

 obtained by boiling it with acetone and then diluting with 

 alcohol and water to turbidity. The crystals are tiny salmon- 

 coloured lozenges showing a slightly oblique extinction and 

 melting with decomposition at 185°. 



On boiling dibromodicresoquinone with bisulphite the quin- 

 hydrone is obtained in a few minutes, but about ten hours are 

 necessary to reduce this to dibromodicresol. The aqueous solu- 

 tion then contained some ionic bromine, showing that, as in the 

 case of Alagatti's " tetrabromodiphenoquinone "* some of the 

 bromine is loosely held in the strained benzene rings. 



F. Tctvabvomo-dicrcsoquinhydronc (dibromodicresoquinone 

 -\- dibromodicresol) is best obtained by adding an acetic acid 

 solution of chromium trioxide drop by drop to solution of 

 dibromodicresol in acetic acid at 50°, avoiding excess of oxidant. 



*Proc., 1906, 110. 



