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LX. Contributions to the Theory of the Constitution of the 

 Diazoamido- Compounds. By Eaphael Meldola, F.R.S., 

 F.I. C, F. C.S., Professor of Chemistry in the City and Guilds 

 of London Institute, Finsbury Technical College*. 



IN a series of investigations upon the diazoamido-compounds 

 which have been carried out by me in conjunction with 

 Mr. F. W. Streatfeildf, certain facts have been brought to 

 light which are quite inexplicable by any of the formulae at 

 present in use ; and it has therefore become necessary to 

 reconsider the whole question of the chemical constitution of 

 these interesting derivatives, which have taxed to the utmost 

 the ingenuity of all those chemists who have concerned them- 

 selves with their investigation. 



The formula which up to the present time has been generally 

 adopted is due to KekuleJ, and is thus expressed in general 

 terms : — 



X.N 2 .NH.Y, 



X and Y being similar or dissimilar radicals. The chief 

 objection to this formula has hitherto been its asymmetrical 

 character, which renders it incapable of explaining the remark- 

 able observation of Griess§, which is now confirmed from 

 many sides, viz. that the mixed diazoamido-compounds, in 

 which X and Y are dissimilar, are always identical whichever 

 radical is first diazotized. This difficulty has been to some 

 extent met by the suggestion of Victor Meyer || ; and in a 

 former paper by Mr. Streatfeild and myself if it was shown 

 that the results of our investigations, as far as these had been 

 carried, could be explained by means of this hypothesis of the 

 formation of intermediate additive compounds with a consi- 

 derable show of reason. 



The extension of our work has, however, forced me to the 

 conclusion that Kekule's formula does not adequately express 

 all the known facts concerning the diazoamido-compounds ; 

 and if this formula is, as I believe it must be, abandoned, the 

 supplementary hypothesis is also rendered unnecessary. 



The evidence which has led to the present theoretical 



* Communicated by the Author. 



t Journ. Ohem. Soc., Trans. 1886, p. 624; and 1887, p. 102. 

 \ Lehrbuch d. org. Chem. vol. ii. pp. 689, 715, and 741 ; Zeit.f. Chem. 

 1866, pp. 308, 689, and 700. 



§ Ber. deut. chem. Gesell. vii. (1874), p. 1619. 



|| Ibid. xiv. (1881), p. 2447, note. 



% Journ. Chem. Soc, Trans. 1887, p. 116. 



