OP ARTS AND SCIENCES. 159 



is more reactive than the bivalent carbon atom present in the 

 isonitriles, RrN=C=, which must be due to the more positive condi- 

 tion of the molecule ; if, however, the copper salt, 



CH 3 -COcu * 



II 

 C0 2 ECH 



be taken, we have a substance whose reactivity is about the same 

 as that of the isonitriles. 



The objection of v. Pechmann,f that silver acetonedicarboxylic 



ether, 



COoR-CHo-COAg 

 II 

 COoRCH 



reacts with alkyliodides, forming the same product as the sodium 

 salt, is without weight, since it has already been proved t that 

 copper, lead, and mercuric acetacetic ether react with alkyliodides 

 and acid haloids, forming addition products, i. e. the metal is not 

 directly replaced. It is therefore to be expected that a silver salt 

 will show a similar behavior. 



That in the case of silver salts the metal is not always directly 

 replaced is evident from the behavior of silver cyanide, Ag]ST=0, 

 towards benzoyl- and acetylchloride (vide p. 157, and cf. J. pr. 

 Chem. [2.], 42, 177). 



Furthermore, the fact that acetonedicarboxylic ether forms a di- 

 potassium salt § cannot be considered as evidence against its hydrox- 

 ylated nature, since this salt can very well possess the constitution, 



J^>C=CH-COK 



HCC0 2 R 



V. Pechmann || has just proved, exactly as Claisen % had already 

 done in the case of ketoaldehydes, 



Pv 



R-COOCH 

 OH 



* Means half an atom of copper Cu". 

 t Ber. d. chem. Ges., XXIV. 4097. 

 t Ann. Chem. (Liebig), CCLXVI. 59 and 121. 

 § Ber. d. chem. Ges., XXIV. 4096. 

 || Ibid., XXV. 1040. 

 IT Sitzungsber. der bayer. Akad. d. Wiss., XX. 463. 



