ISOMORPHOUS SULPHONIC DERIVATIVES OF BENZENE. 18l 



Progress has been made in extending the investigation to the com' 

 parison of the effect produced by homologous hydrocarbon radicles, and 

 also in contrasting corresponding sulphur and oxygen compounds. 



Our Present Knowledije of Aromatic Diazo-compouncU. 

 Bij Gilbert Thomas ^Morgan, D.Sc, F.I.C. 



[Ordered by tlie General Committee to be printed in extenso.} 



The aromatic diazo-compounds, which were originally discovered by the 

 classical investigations of Griess/ have proved to be substances of the 

 utmost value in the development of synthetical chemistry, both from the 

 scientific and the industrial standpoints. The starting-point of these far- 

 reaching researches was a comparative study of asparagine and picramic 

 acid. These substances, which in 1858 were assumed to be compounds 

 of a similar type, behaved quite differently towards nitrous acid, asparagine 

 losing the whole of its nitrogen, whilst picramic acid exchanged three of 

 its hydrogen atoms for one of nitrogen, giving rise to the earliest 

 known diazo-corapound — namely, dinitrophenoldiazo-oxide. 



It is interesting to notice at this stage that, although the elimination 

 of aminic nitrogen by the action of nitrous acid is characteristic not 

 only of asparagine but also of the majority of aliphatic amino-compounds, 

 yet the preparation of aliphatic diazo-derivatives has been accomplished, 

 and the new field opened up by the discovery of ethyl-diazo-acetate - has 

 yielded a rich harvest culminating in the isolation of hydrazine, hydrazoic 

 acid, and diazo-methane. These important contributions to the chemistry 

 of nitrogen will not, however, be further discussed in this report, which is 

 restricted to a consideration of the aromatic diazo-compounds, a class of 

 substances derived from the hydrocarbons of coal tar. 



The action of nitrous acid on picramic acid is now interpreted in the 

 following manner, 



OH HO ! ,0 



NiH, OiN ^^^ 



2 



the product being regarded either as the internal salt or the cso-anliydride 

 of dinitrophenoldiazo-hydroxide (N02)2CcH.>(OH)N20H. ^ 



Griess next extended the investigation to aniline, with the result thak 

 diazoaminobenzene was produced. 



CgH^NH i H HO i 



...iZIIIiri = CoH6NH.N,CoH5 + 2H,0, 



» A/iTialen, 1858, 106, 123 ; 1860, 163, 201 ; lS6fi, 137, 39. 

 » Curtius, Ber., 1888, 16, 2230. 

 • H'.Titz.sch. Ber., 1890, 29, 1526, 



