758 



low ooncentration, siicli as used in tlie above experiment, may act 

 as an oxidiser, it is likely to attack this t>-riitrodimethyIaniline in 

 the still unoccupied pa^-a-positions and cause the formation of 

 (>.r/-dinitrotetramethylbenzidine, which is more readily capable of 

 further nitration, particularly in the presence of nitrous acid. As is 

 well-known, the nitro-group, in this prolonged nitration, exerts an 

 inllueuce of such a kind that the newly entered nitro-groups arrange 

 themselves meta in regard to the previous ones. 



It may also be possible that the dimethylamine itself is oxidised 

 directly to a benzidine derivative of which it may be assumed (in 

 analogy with different other benzene derivatives in which the para- 

 position in regard to the amino,group has been occupied) that the 

 nitration will take place in a corresponding manner. Hence, I have 

 tried in the first place to prepare the 3. 3'. 5. 5' tetranitrotetramethyl- 

 benzidine synthetically. 



After several vain efforts, to which ! will not now refer, I have 

 taken the following course. 



I started from p.-diphenoldiethylether, which I prepared according 

 to Htrsch's directions^) and then treated with fuming nitric acid. 

 The dark coloured solution, on heating soon became pale yellow 

 and on cooling the tetranitrodiphenoldiethylcther crystallises in long, 

 transparent colourless needles melting at 25(>° — 257°. 



Analysis: found 45.6 »/„ C. 3.5 "/„H 13.5 %N. 



calculated for C,,H,,N,0,„ 45.5 „ 3.3 „ 13.3 „ 



Of the tetranitrodiphenolether, 1 placed 2 grams in a tube of 

 resistance glass and added a solution of 1 gram of dimethylamine 

 in 25 cc. of alcohol. The sealed tube was first placed in a boiling 

 water-bath, which caused the contents to slowly turn an orange-red. 

 I further also heated for some hours at 120° when it appeared that 

 a red crystalline mass had deposited. This product was collected 

 and washed with warm alcohol and warm water, when it appeared 

 that the compound dissolved in the latter. On addition of strong 

 hydrochloric acid to the red coloured solution, a yellow coloured com- 

 pound was precipitated which could be recrystallised from acetic 

 acid, and melted at 223°. It struck me as not being improbable 

 that this product was tetranitrodiphenol and indeed it caused no 

 lowering of the melting point when mixed with this substance. 



As to its structure, the opinions remained, however, divided. Bj- 

 boiling it with strong nitric acid I succeeded, as did ScHjnoT and 

 ScHULTZ '), in converting it into picric acid, so that the position of the 



1) Ber d. D. Chem Ges. 22, 335 (1889). 



2) Ann. d. Chemie 207, 334 (1^81). 



