JACKSON AND CALVERT, ^ DERIVATIVES OF BENZOL. 127 



but although we have fouud indications that such a substance is formed, 

 we have not succeeded in isolating it. 



Tlie principles governing the replacement of radicals attached to 

 the benzol ring, which we have brought forward in this introduction, 

 make it possible to explain the strange behavior of tribromtrinitroben- 

 zol with sodic ethj'late. This action consists in the two following 

 reactions, which take place side by side.* 



C6Br3(N02)3 + 3 C2H50Na= C6(OC2H5),(NO.)3+ 3 NaBr. 

 C6Br3(N02)3 + 2 CaHgONa = C.BrgNOoCOaHs)^ + 2 NaNOa- 



In this substance we seem to have two zones of action, one consist- 

 ing of the three symmetrically disposed bromine atoms, the other of 

 the three nitro groups also symmetrically disposed, and the action in 

 each molecule is confined to one of these zones, if it is carried on in 

 the cold. In the first or bromine zone the atoms of bromine are 

 submitted to two loosening influences : (a) that of the three nitro 

 groups in the diortho and para positions to each bromine atom, and 

 (b) that of the trimeta bromine atoms on each other. In the second or 

 nitro zone also we have two loosening influences : (c) that of the three 

 bromine atoms diortho and para to each nitro ji'roup, and (cl) the loosen- 

 ing effect of the three symmetrical nitro groups on each other. Of these 

 loosening influences (a) is by far the strongest, and (b) the weakest ; 

 it seems therefore that the combined effect of (c) and (d), of inter- 

 mediate strength, is about equal to that of (a) and (b) together ; con- 

 sequently each of these zones of action lies about equally open to the 

 attack of the sodic ethylate, and the two reactions take place simul- 

 taneously. When the solvent is alcohol alone, they run to about the 

 same extent. If the repellent action of the three symmetrical nitro 

 groups (d) is removed, that is, if tribromdinitrobenzol is used instead 

 of the trinitro body, the nitro groups should be much less loosened 

 than the bromine atoms, and as a matter of fact there has been ob- 

 served in this case no tendency to remove the nitro groups, the 

 action being confined to the bromine zone, causing the formation of 

 C,Br(OC2H,)2 (N0o)2H, or CgH(OC,rL),(N02)2H. 



The work described in this paper has furnished us with three addi- 

 tional cases, in which atoms of halogens have been replaced by hydro- 



* These Proceedings, XXVII. 283. Tetrabromdinitrobenzol acts in the same 

 way, as just stated, but for the sake of simplicity of expression the explana- 

 tion has been confined to the trinitro body, altliough it applies equally well to 

 the tetrabrom compound. 



