25G DERIVATIVES OF DIPHENOOUIXONE. 



C. Dicresiininoquinonc (3-3' dimcthyldiphcnoqulnone- 

 diiiiiiiic) is obtainable by oxidising tolidine by Willstaetter's 

 method, but the product (very dark red granules with faint blue 

 lustre, m.p. 158-160°) is unsatisfactory. It gives a purple colora- 

 tion with sulphuric acid and is reduced by stannous chloride with 

 great difficulty to tolidine and another (unidentified) substance. 

 The amount of tin used in the reduction is only threequarters of 

 the theoretical. All its properties suggest that it is an azo- 

 dye produced by polymerisation of the original diimine.* The 

 same applies to Willstaetter's diphenoquinonediimine. 



D. Dicrcsiininoqnmhydrone {quinhydromc cornhination of 

 true dicresiininoquinonc and tolidine) is, however, easily obtained 

 as a nitrate. Tolidine is dissolved in a little over the theoretical 

 amount of nitric acid and excess of water at 70° and treated 

 with excess of ferric nitrate solution. The new substance 

 crystiallises out almost at once and is filtered off on cooling, and 

 washed in a thin layer on a Buchner funnel with a minimum 

 of water, as it hydrolyses easily to an amorphous basic nitrate. 

 This remarkable substance forms very deep blue-violet needles, 

 quite opaque even in sunlight unless powdered, with a bronze- 

 coloured metallic lustre. It decomposes at 240° without melting. 

 It dissolves in warm water to a deep blue solution which then 

 deposits the basic nitrate as a greenish-blue scum with copper 

 lustre. In dilute acid it dissolves to a yellowish-brown, becoming 

 deep green on dilution. Stronger acids dissolve it to the pure 

 yellow colour attributable to the diimine itself. All the solutions 

 decompose on boiling and produce a violet azo-dye. Concen- 

 trated sulphuric acid gives a deep orange-yellow, which stands 

 dilution and even boiling : the diimine is evidently stable when 

 combined with excess of acid. Iron and water of crystallisiation 

 were found to be absent. 



N 

 0.1960 used 3.90 cc Jq SnClg : H =0.40%. | Tolidine was the 



j^ reduction- 



0.4410 used 9.05 cc -jQ SnClg : H = 0.41%. ) product. 



0.6940, boiled with caustic soda and worked up with " nitron '' 

 acetate, gave 0.8910 " nitron " nitrate HNO3 = 21.6 %, probably 

 22.5%, allowing for the solubility of " nitron "-nitrate. The 



CH3 Ch3 CH3 ^ CH3 



formula '^.,.X^. /^-nh + no^nm/^\V VH3 noUc^h o^n 



requires H = 0.36%, HXO, = 23.0%. 



The azo-dye resulting from boiling this with water was 

 amorphous and tcto insoluble to investigate : it gives a very fine 

 crimson coloration with sulphuric acid, and its salts are soluble 



* See Willstaetter Zoc. cit. and Moir, Trans. R.S.S.Afr. 1911. 



