OF ARTS AND SCIENCES. 307 



The formation of brommalonic ester in III., the only point in these 

 reactions about which there was any doubt, was proved by the isola- 

 tion of acetylentetracarbonic ester* or of tartronic acid J from the 

 oily secondary product, as these substances could hardly have been 

 formed otherwise than by the following reactions, — 



CHBr(COOC 2 IL), + CHNa(COOC 2 H 5 ) 2 = 



CHCfI((JOOC 2 lL) 4 + NaBr. 

 CHBr(UOOG,H 5 ) 2 + NaOM = CHOII(COOC 2 H.) 2 + NaBr. 



Reactions I.— III. are given because they show more clearly what 

 has taken place, but the discussion which follows does not depend 

 on them alone, since the analyses of the products are sufficient to 

 prove that in all the cases studied the action has consisted in the re- 

 placement of one atom of bromine by the malonic ester radical, and 

 of the second by hydrogen, while the third (and fourth) has remained 

 unaltered.! This difference in the behavior of the three atoms of 

 bromine is certainly very curious, and, so far as I can find, no case 

 analogous to it has been described as yet. The strangeness of the 

 replacement of bromine by hydrogen becomes especially evident when 

 it is remembered that in every case there was a large excess of sodium 

 malonic ester present, and that this second atom of bromine has there- 

 fore combined with the carbon of malonic ester (see Reaction III.) in 

 preference to the sodium of sodium malonic ester, so that the tendency 

 to introduce hydrogen rather than the malonic ester radical has been 

 strong enough in this case to overcome the attraction of the bromine 

 for the sodium, and to cause it to combine with carbon instead. 



I have not succeeded in finding any explanation of these curious 

 observations which satisfies me, but hope to be led to one by further 

 experiment. It can be stated at present, however, that the difference 

 of behavior in the three bromine atoms is not due to differences in 

 their position on the benzol ring. This is shown easily in the case of 

 the tribromtrinitrobenzol, as here the three atoms of bromine occupy 

 exactly similar positions, each being ortho to two nitro groups and 

 para to the third. In the tribromdinitrobenzol.§ also, the first ami 



* These Proceedings, xxiv. "2G5. t Ibid., xxiv. 238. 



J Ih the trinitro compound the third atom of bromine is replaced by the ma- 

 lonic ester radical to a limited extent even in the cold, but it is acted on much 

 less easily than the first. 



§ In the tetrabromdinitrobenzol the fourth atom of bromine seems to have 

 no influence on the reaction, and therefore all I say about the tribromdinitro- 

 benzol also applies to this substance. 



