JACKSON AND COHOE. — METADIBROMDINITROBENZOL DERIVATIVES. 77 



Preparation of Metadibromdinitrobenzol. 



Monobromacetanilid was first made by passing a stream of air laden 

 with the vapor of bromine through five litres of water in which fifty grams 

 of acetanilid were suspended. The end of the reaction was determined 

 by the appearance of a lasting yellow color in the liquid and a distinct 

 change in the appearance of the solid. In all our attempts to convert 

 this product into the dibromacetanilid by the action of liquid bromine on 

 it when suspended in water, we observed the formation of a considerable 

 amount of symmetrical tribromaniline (NH 2 1. Br 3 2. 4. 6.), produced un- 

 doubtedly by the action of bromine on the free base proceeding from the 

 saponification of some of the bromacetanilid by the hydrobromic acid 

 formed in the reaction. The monobromacetanilid was accordingly filtered 

 out, and after being dried, suspended in glacial acetic acid or chloroform, 

 to which a little more than the calculated amount of bromine was then 

 added drop by drop. This method gave an excellent yield of the 

 dibromacetanilid with little trouble. 



The dibromacetanilid was saponified by boiling it with sulphuric acid 

 of specific gravity 1.44 in a flask with a return condenser, until the solu- 

 tion of the solid, which was usually accompanied by a darkening in color, 

 showed that the reaction was complete. The liquid was then allowed to 

 cool, when most of the dibromaniline crystallized out, and what remained 

 in solution was precipitated by the addition of a large quantity of water. 



To remove the amido group, 100 grams of the dibromaniline were 

 dissolved in a mixture of 300 c.c. of alcohol and 120 c.c. of benzol, to 

 which 20 c.c. of sulphuric acid had been added ; the mixture was heated 

 in a flask on the steam bath, and 60 grams (a large excess) of solid sodic 

 nitrite added as fast as the reaction would permit. The contents of the 

 flask, which had taken on a reddish color, were boiled for an hour, and 

 then allowed to stand over night, after which a large quantity of water 

 was added, and the precipitated oily liquid distilled over with steam. A 

 small amount of tribrombenzol is usually present, which appears as a 

 solid in the condenser toward the end of the distillation with steam ; it is 

 well to stop the distillation as soon as this solid appears. The distillate 

 with steam was dried with calcic chloride and distilled, collecting for use 

 the fraction boiling from 210° to 225°. A small additional amount of 

 dibrombenzol was obtained by extracting with ether the aqueous portion 

 of the steam distillate, but the increase of the yield in this way was so 

 small that this extraction was hardly worth while. 



The dibrombenzol was converted into dinitrodibrombenzol by boiling 



