196 REPORT— 1902. 



with Fischer's yellow diazo-sulphonate CgHj.No.SOjKt asserted that these 

 isomerides belonged to the syn- and c«i<vdiazo-series respectively, • but 

 Bamberger objected to this classification and showed that the red salt has 

 the properties of a sulphite 0,,H,=,N2.0.S0.2K. '-^ 



The former investigator has, however, succeeded in isolating a series 

 of isomeric diazo-cyanides.'' ;;-Chlorobenzenediazonltitli chloi'ide, when 

 treated with cold potassium cyanide solution, yields a labile salt which 

 readily evolves nitrogen, forms ^>chlorobenzonitrile on treatment with 

 copper powder, and passes into a stable isomeride. The latter, which is 

 not affected by copper powder and may even be distilled in steam, is 

 undoubtedly the o»ii-diazo-cyanide, whilst the labile derivative belongs 

 to the syn-diazo-series. Both isomerides have a yellow colour, and this 

 fact tends to exclude the view that the labile derivative is a diazonium 

 cyanide, for the diazonium radicle gives colourless salts with colourless 

 acids. 



The syn-diazo-cyanides are more stable when the aromatic nucleus 

 attached to the diazo-group contains substituent radicles. 



When a diazonium chloride is treated with a suspension of silver 

 cyanide the coloui-less solution obtained, after filtering off the insoluble 

 yellow s7/?t-diazo-cyanide, contains a soluble double cyanide which is 

 considered by Hantzsch and Danziger ^ to be a diazonium derivative. The 

 double cyanide derived from ^'-cumenediazonium chloride has been iso- 

 lated and its properties are best expressed by the formula 



C6H2(CH3)3.KCN, AgCN. 

 N 



The «?i<i-diazo-cyanide does not yield this double salt. 



The formation of this double diazonium cyanide suggests that the 

 sparingly soluble si/H-diazo-cyanide may exist in solution in a state of 

 equilibrium with the isomeric diazonium salt, and further confirmation of 

 this hypothesis has recently been obtained "' by a study of the cyanides 

 obtained from p-methoxybenzenediazonium bromide and chloride. These 

 salts by double decomposition with potassium cyanide in alcoholic solution 

 yi the syn-diazo-cyanide 



MeO.C^H,.N 



II 

 CN.N 



an orange- I'ed insoluble substance (melting-^Doint 51°) which couples with 

 /3-naphtho], and slowly changes into the non-coupling anti-salt 



MeO.CgH^.ISr 



II 

 N.CN 



a brownish-red compound melting at 121°. 



The existence of a third isomeric cyanide is indicated by evaporating 

 at the ordinary temperature in the presence of excess of hydrogen cyanide 

 an aqueous solution of ^;-methoxybenzenediazonium hydroxide. The 

 colourless, crystalline substance obtained has the composition 



MeOCoH jNoCN, HCN, 2H2O, 



' Ber., 1894, 27, 1726. - Ber., 1894, 27, 2930. = Ber., 1895, 28, 666. 

 ' Ber., 18 30, 2529. ' Ber., 1900, 33, 2101 ; 1901, 34, 4166. 



