308 PROCEEDINGS OF THE AMERICAN ACADEMY 



third atoms of bromine are similarly placed (ortho to one, para to the 

 other uitro group), but the second (that replaced by hydrogen) is pe- 

 culiar in being ortho to both nitro groups. It is evident, then, that in 

 these reactions both similarly j^laced bromine atoms are not replaced by 

 the malonic ester radical ; but it is also to be observed that the bromine 

 which is replaced by hydrogen has in every case stood in the ortho 

 position to two nitro groups, and this suggested to me that perhaps an 

 atom of bromine in this position might be especially susceptible to the 

 action of free malonic ester. To test this hypothesis I mixed some 

 tribromdinitrobenzol dissolved in benzol with malonic ester, and, after 

 the mixture had stood for some time in the cold, warmed it for about 

 an hour on the water bath, but even after this treatment no action * 

 had taken place, as the tribromdinitrobenzol melted unaltered at 192°. 

 This result was confirmed by a similar experiment with acetacetic 

 ester, which stood with tribromdinitrobenzol for six months without 

 any action. It is evident, therefore, that this atom of bromine is not 

 attached in an especially loose way to the molecule, and that its re- 

 placement by hydrogen does not depend only on its position with 

 reference to the nitro groups, but is due also to the presence of the 

 malonic ester radical. 



On the Relative Ease with which the Reactions take Place. 



This subject will I hope prove susceptible of quantitative treatment, 

 and I propose next year to try some experiments of this sort ; I shall 

 therefore at present confine myself to two qualitative observations, 

 which were so marked that a quantitative confirmation of them seems 

 unnecessary. 



The tribromtrinitrobenzol is distinctly more reactive than the tri- 

 bromdinitro- or tetrabromdinitrobenzol, as it acts on alcoholic ammonia 

 in the cold, whereas the other two must be heated to 100° in sealed 

 vessels to bring about this reaction. 



The sodium acetacetic ester acts much less energetically than sodium 

 malonic ester upon tribromdinitrobenzol, since the red color of the 

 product appears instantaneously with the malonic ester, but only after 

 some time with acetacetic ester, and the yield of the acetacetic com- 

 pound is much smaller than that of the malonic derivative, if the 

 reactions are carried on under the same conditions. 



* The addition of a little aqueous sodic hydrate was enough to cause action 

 at once, as shown by the appearance of the red color of the sodium salt. 



