( 1^)2 ) 



toluenes, the 1-2-4-6 and the 1-2-3-5 derivatives exhibit an isomorphy 

 bordering on identity. I then endeavoured to explain the similar 

 molecular structure of these two substances bj referring to the 

 analog}' of the {^CH^y^vowY) and ^r-atom in the positions 1 and 2, 

 particularly in a spacial respect. The small differences in crystalline 

 form, melting point etc., are then caused by the difference which of 

 course exists between CH^ and Br. 



We may now inquire how matters will be in both molecules as 

 regards the substitution of the two remaining i/-atoms of the core 

 for instance. It is interesting to notice that as regards the substitution 

 by {NO^) the two //-atoms in each of the two isomers are quite e^wi- 

 vale?it and — what is still more striking — • that this substitution does 

 not perceptibly alter the molecular symmetry of the two molecules, 

 so that the crystal lac/ rajjhical relation of the initial products is pre- 

 served in the substitution derivatives. 



If we nitrate the 1-2-4-6-tribromotoluene with nitric acid of 1,52 

 sp. gr. a dinitro -product is obtained, as shown by Nevile and 



WlNTHER ^). 



Wroblewsky ^) had previously obtained a mono-nitro-derivative 

 which differs in its melting point but little from the dinitro-product. 



But notwithstanding many efforts, I have never succeeded in 

 obtaining a mononitro-compound not even as a bye-product, when 

 using fuming nitric acid. 



The mere formula of 'l-2-3-5-tribromotolue?ie does not at once raise 

 a suspicion that a dinitro-product will be formed in this case. If, 

 however, the analogy of (C'/Zj) in the position 1 and Br in the 

 position 2 is really so great that the difference amounts almost to 

 nothing, we may surmise that the l-l-'^-b-tiibromotoluene will behave 

 on nitration also nearly quite analogously to the other isomer. The 

 experiment shows that in this case also not a trace of any mononitro- 

 derivative is obtained; we obtain exclusively a r/m/^ro-producl, which 

 is in all respects quite analogous with the above named dinitro- 

 derivative. 



After nitration by red fuming nitric acid (sp. gr. 1,516 at 16°) in 

 the cold, separation b}^ adding an excess of water, agitation with 

 benzene and ether and recrystallisation from benzene, in which both 

 isomers are very soluble, the two substances are at once obtained 

 pure in large colorless or pale sherry-colored crystals, whose bromine- 

 amount corresponds with that of the dinitro-derivative. 



1) Nevile and Winther, Journ. Ghem. Soc. Vol. 37. 438; Berl. Ber. 13. 974. 



2) Wroblewsky, Ann. d. Chemie 168. 147. 



