516 Prof. R. Meldola on the Theory of the 



If the ethyl-derivatives Nos. 7 and 8 are formulated on 

 Kekule's type they would have the formulae IV. and III. 

 respectively, and thus no other expression is left for the ethyl- 

 derivative No. 4. 



The conditions to be fulfilled by any formula proposed for 

 the diazoamido-compounds are, therefore, (1) that it should 

 be symmetrical so as to represent the identity of mixed diazo- 

 amido-compounds, and (2) that it should be capable of repre- 

 senting more than two isomeric alkyl-derivatives of mixed 

 compounds. These conditions are certainly not met by the 

 formula now in use ; and the objections which apply to this 

 apply also to the alternative formula proposed by Strecker* : — 



X.N.NH.Y 



N 



This formula fails to explain the existence of more than two 

 isomeric alkyl-derivatives of the unsymmetrical (mixed) com- 

 pounds ; and is even less able than Kekule's of representing 

 the identity of mixed compounds, since it is incapable of the 

 rearrangement suggested by Victor Meyer. 



The first symmetrical formula proposed to explain the iden- 

 tity of mixed diazoamido-compounds is due to Griessf, the 

 discoverer of these compounds, who suggested that diazoamido- 

 benzene and its analogues should be written according to the 

 type :— 



C 6 H 4 =N=N=N=C 6 H 4 



H H H 



This formula certainly explains the identity of mixed com- 

 pounds, but is otherwise open to certain objections ; since in 

 the first place it represents diazoamidobenzene as a phenylene 

 derivative, and in the next place it shows the presence of 

 three NH-groups containing three replaceable hydrogen atoms. 

 All our experiments upon the salts and alkyl-derivatives of 

 the dinitrodiazoamido-compounds have shown, however, that 

 only one replaceable H-atom is present^. This formula, 

 moreover, is not capable of explaining the easy resolution of 



* JBer. deut. chem. Gesell. iv. (1871), p. 786 ; Erlenmeyer, ibid. vii. (1874), 

 p. 1110, and xvi. (1883) p. 1457. Also Blomstrand, ibid. viii. (1875), 

 p. 51. 



f Ber. deut. chem. Gesell. x. (1877), p. 528. 



X These compounds give only monalkyl-derivatives ; and the same 

 appears to be the case with diazoamidobenzene, according to Messrs. 

 Friswell and Green (Journ. Chem. Soc, Trans. 1886, p. 748), to whom I 

 communicated the method of alkylization in the course of conversation, 

 and who applied it to this compound successfully. 



