206 REPORT — 1902. 



The stereochemical theory may be briefly outlined as follows 



R.N.C1 



(NaOH) 



II 



- E.NOH I ^ R.KOH 

 HON.H U N 



(NaOH) 



4. 

 R.N 



steric change 



:> R.NH.NO 



NaO.N 

 labile siyw-diazo-oxide. 



N.ONa 

 stable «7i!'i-diazo-oxide. 



The substances indicated in square brackets are hypothetical inter- 

 mediate compounds, the existence of which is assumed in order to explain 

 the tautomeric changes. 



In our present state of knowledge a choice still remains between a 

 theory of diazo-compounds which, although not assuming any spatial 

 relationships, nevertheless offers an explanation of the isomerism of these 

 substances which is applicable to this series of nitrogen-derivatives alone, 

 and a stereochemical hypothesis which correlates the diazo-derivatives 

 with other nitrogen compounds of a similar type and affords a general 

 interpretation of a considerable group of experimental facts. 



The assumption of syn- and tiM^i-isomerism explains the production 

 of the two series of coloured cyanides and sulphonates from the colourless 

 diazonium salts. Moreover, the stereochemical hypothesis renders it 

 possible to connect the relationship between the diazonium and syn-d\&zo- 

 laydroxides with the general theory of quaternary ammonium compounds. 

 In a similar manner the behaviour of the primary aromatic nitrosamines 

 and the «n^i-diazo-oxides may be correlated with the general theory of 

 pseudo-acids and their salts. 



It may be urged against the stereO-chemical theory of diazo-compounds 

 that the 67/?i-cliazo series is still very defective, being confined to three 

 classes of substances, the metallic diazo-oxides, the diazo-cyanides, and 

 diazo-sulphonates, and it is still possible that the isomeric cyanides and 

 sulphonates may be shown to be structurally different. On the other 

 hand the view that the sy?t-diazo-compounds have a diazonium configura- 

 tion leads to conclusions which are not in accordance with experimental 

 facts. This is particularly the case with the metallic diazo-oxides, for it 

 becomes necessary to assume that the strongly basic diazonium hydroxides 

 also react as acids. This hypothesis is in the highest degree improbable, 

 there being no other exq,mple of a quaternary ammonium hydroxide 

 possessing this dual nature. 



