186 REPORT— 1902. 



subsequently removing the hydrazino-radicle NH.NH2 by boiling with 

 cupric sulphate solution. 



Sodium stannite has been recommended as an agent for reducing 

 the diazonium salt to the hydrocarbon ' : CgH5N2Cl + NaOH + NaoSn02 

 =OgH6 + N, + Na2Sn03 + NaCl. 



Mai has recently found that p-toluenediazonium chloride, when added 

 to a strong solution of hypophosphorous acid gives rise to toluene, the 

 yield being 67 per cent. Benzenediazonium chloride yields a mixture of 

 benzene (two parts) and diphenyl (1 part), whilst diazotised benzidine and 

 a-naphthylamine furnish diphenyl and naphthalene respectively.^ 



6. Substitution of NH^ hy OH. — The replacement of NH2 by OH, 

 although an extremely important synthetical operation, can hardly be 

 included amongst the modern developments of the application of diazonium 

 salts, inasmuch as the process still employed, which consists in boiling the 

 aqueous solution of the diazonium salt, is a legacy derived from Griess's 

 pioneering researches. 



The manufacture of the 1 : 4- and 1 :8- a-naphtholsulphonic acids 

 from the corresponding amino-compounds 



S03H.C,oH6NH2 -> CioH / | --> C,oHo(OH)S03H + N2, 



\S03 



and the production of 1 : 8-dihydroxynaphthalene 3 : 6-disulphonic acid 

 (chromotrope acid), may be cited as examples of the application of this 

 process. 



7. 2IiscelIaneous Substitutions. — There are several other modes of 

 reaction which, although of less importance from the synthetical point of 

 view, are nevertheless of interest as indicating the extremely reactive 

 character of the diazonium salts. 



(i) The amino groups in certain azo-dei-ivatives of /3-naphthylamine are 

 replaced by the acetoxy-radicle when these substance.? are diazotised in 

 warm glacial acetic acid,^ and Orndorff' ^ showed that this reaction may be 

 generally employed in the production of aromatic acetates. 



(ii) A remarkable example of intramolecular change was noticed by 

 Hantzsch in studying the chloro- and bromo-diazonium thiocyanates.* 

 These salts, when dissolved in alcohol containing a trace of hydrochloric 

 acid, become converted into the isomeric thiocyanobenzenediazonium 

 chlorides and bromides, 



ClCoH,.N2.CNS -» CNS.CoH,.N2.Cl 



This change takes place only when the halogen atom is situated in 

 an ortho- or para-position with respect to the diazonium group ; transfer- 

 mation does not occur in the case of m-cbloro benzenediazonium thio- 

 cyanate. 



The extent to which this rearrangement is possible is best indicated 

 by the limiting case, 2:4: 6-tribromobenzenediazonium sulphate in the 

 presence of excess of potassium thiocyanate actually giving rise to 2 : 4 : 6- 

 trithiocyanobenzenediazonium thiocyanate (CNS)3C6H2N2-CNS. 



' Friedliinder, Ber., 1889, 22, 587. ^ her., 1902,35, 162. 



» Meldola and East, Tran&., 1888, 53, 460. ■■ Amer. Cliem. Jmirn., 1888, 10, 368, 

 ' Ber., 1896, 29, 947 ; 1898, 31, 1253. 



