184 KEPORT— 1902. 



acid radicle becomes directly attached to the aromatic nucleus ; (iii) the 

 formation of azo-compounds, which is accompanied by the oxidation of 

 the cuprous salt to the cupric condition. 



The concurrent effect of the first two reactions was demonstrated by 

 subjecting dry ;)-bromobenzenecliazonium bromide to the action of cuprous 

 chloride dissolved in methyl sulphide. The product consisted chiefly of 

 ^j-bromochloi"obenzene mixed witli a little ^;-dibromobenzene. 



(i) 2BrC„H,N.,Br + Cu,Clo = CuoBr, + 2N., + 2C,;H,ClBr. 

 (li) BrCoH,NoBr = N.H- CoH^Br,. 



Cuprous bromide and ^j-bromobenzenediazonium chloride yielded 

 ^j-dibromobenzene containing a little ;;-bromochlorobenzene. In both 

 cases the first reaction predominates, and it may, under certain conditions, 

 prevail to the almost complete exclusion of the second. Cuprous iodide, 

 for example, gave rise to iodo-derivatives only, with various diazonium 

 chlorides and bromides, and on the other hand the interaction of cuprous 

 chloride and benzenediazonium iodide furnished chlorobenzene unaccom- 

 panied by iodobenzene. 



2. Replacement of NH.^ hijNO.i. — The introduction of nitroxyl through 

 the agency of the diazonium salt was first indicated by Sandmeyer, and 

 further exemplified by Hantzsch (Joe. cit.) in the following experiments : — 



(i) The crystalline double salt Hg(N0._,)2, 2C,;H.-,]Sr.,.N0:, (melting-point 

 76°), obtained by mixing solutions of benzenediazonium nitrate and potas- 

 sium mercuric nitrite, decomposes on boiling with water yielding phenol and 

 nitrophenol, but when treated with copper powder it furnishes a quanti- 

 tative yield of nitrobenzene, (ii) The diazonium sulphates, when mixed 

 with a freshly prepared suspension of cupro-cupric sulphate and treated 

 with excess of an alkali nitrite, give I'ise to the corresponding nitro- 

 derivatives ; 2 : 4 : G-tribromobenzenediazonium sulphate, for example, 

 gives a 65 per cent, yield of l-nitro-2 : 4 : 6-tribroniobenzene. 



/>nitronaphthalene, a substance prepared with considerable difficulty 

 by other processes, is produced from /5-naphthylamine to the extent of 

 25 per cent, by this method, whereas Sandmeyer, who employed cuprous 

 oxide and the diazonium nitrite, obtained only 7 per cent.' 



3. Formation of Conjugated Systems R.E or K.N : N.R. — The third 

 reaction signalised by Hantzsch may be rendered more apparent by 

 reversing the usual order of mixing and adding the cuprous chloride 

 dissolved in hydrochloric acid to the cold solution of the diazonium salt. 

 Under these conditions, aniline, o-chloroaniline and the o- and ;j-toluidines 

 give rise to appreciable quantities of azo-compounds. The nitrated 

 amines, however, behave very differently, yielding diphenyl-derivatives, 

 this result l>eing obtained with tl)e three nitranilines, o-nitro-^J-chloro- 

 aniline and o-nitroaniline-^-sulphonic acid. 



2N0 AH4N2CI + CU2CI2 = NOaCeHj.CoH^NO, + Nj + 2CuClo. = 



This type of condensation is also brought about by the use of cuprous 

 oxide in ammoniacal or hydroxylamine solution.^ 



4. Introduction of the Sulplionic Radicle SO^H. — The replacement 

 of NH2 by SH was first accomplished by Leuckart,'' who treated the 



' Ber., 1887, 20, 1497. 



"^ Ullmann and Forgan, Ber., 1901, 34, 3802; Niementowski, Hid., .^5325. 



3 Annalen, 1902, 320, 122. * Juurn. 2>raM. Chcm. [2], 41, 218. 



