OF ARTS AND SCIENCES. 311 



the hydrogen affected is attached to the side chain, and therefore more 

 removed from the influence of the acid radicals than in most of the 

 similar cases previously described, in which the element influenced was 

 attached to the benzol ring. These observations recall some made by 

 me several years ago, when 1 showed * that the ring bromine in the 

 three brombenzylbromides had a marked influence in diminishing the 

 ease with which the side-chain bromine was removed, varying with its 

 position on the benzol ring, the para bromine having less influence 

 than the meta, the meta than the ortho. 



(d.) The nature of the side-chain also has a marked influence on 

 the acidity ; thus the substituted acetacetic ester I. is much more acid 

 than the corresponding malouic ester III., a result in harmony with 

 Claisen and Ehrhardt's f classification of the radicals according to their 

 acid-producing power, since they give the following list beginning with 

 that which has the least influence, "phenyl, carboxyl, benzoyl, acetyl, 

 formyl." An approximate measure of the relative acid-producing 

 power of carboxyl and acetyl is given by the comparison of III. and 

 IV., which possess nearly the same degree of acidity, and therefore it 

 follows that one acetyl has nearly, although not quite, the same effect 

 as two carboxyls. 



(e.) The comparison of a dimalonic with the corresponding mono- 

 malonic compound in this respect is of interest. Unfortunately I had 

 none of the trinitrophenylendimalonic ester when the comparison de- 

 scribed above was made, so that this substance does not appear in the 

 table; but by comparing the observations made on it when its prop- 

 erties were studied with those on the bromtrinitrophenylmalonic ester, 

 I have found that the dimalonic compound is much less acid than the 

 brommonomalonic ester, since acid sodic carbonate in aqueous solution 

 has no action upon it, and even aqueous sodic carbonate gives only a 

 very faint red color.J This weaker acidity can be accounted for by 

 the hypothesis, that the influence of the three nitro groups being di- 

 vided between two malonic ester radicals, each will have the acidifying 

 influence of only one and a half nitro groups, instead of the three, 

 which act on the acid hydrogen in the monomalonic compound. 



The stability of the salts of all these compounds is remarkable, the 



* Those Proceedings, xvi. 241. 



t Ber. d. ch. G. 1889, p. 1019. 



i I should he inclined to place the trinitrophenylendimalonic ester between 

 III. and V., although from the absence of comparative work ita exact place cun- 

 not be determined with certainty ; this, however, is of little importance, as the 

 comparison of it with II. is the only one of especial interest. 



