Reaction XLIX.— a Action of Cuprous Potassium Cyanide on Aromatic Diazonium Compounds Sandmeyer

Reaction XLIX. (a) Action of Cuprous Potassium Cyanide on Aromatic Diazonium Compounds. (Sandmeyer). (B., 17, 1633, 2650 18, 1492, 1496.)—If a diazonium salt is added to a hot solution of cuprous-potassium cyanide, and the whole boiled on a water hath, nitrogen is evolved, and the corresponding nitrile formed. (C. r., 183, 421.) 

As usual in Sandmeyer reactions, the product, if volatile, is separated by distillation in steam if non-volatile, extraction or filtration is used. The manner in which the cuprous salt reacts is not exactly known it certainly unites at first with the diazonium compound to form a double salt (c/. Reaction CLXVI.). The method is widely applicable, and as the yields are usually good, it is a standard method for the preparation of aromatic nitriles. 

The details of this preparation are practically the same as those given for p-tolu-nitrile (Preparation 82). A cuprous-potassium cyanide solution, prepared as therein described, is warmed to about 70°, and added in small portions to a solution of benzene-diazonium chloride prepared from 18-6 gms. (1 mol.) of aniline as described in Preparation 379. When the addition is complete, the liquid is warmed on a water bath for 15 minutes and distilled in steam the distillate is extracted with ether. The ethereal solution is washed repeatedly with dilute caustic soda and with dilute sulphuric acid, dried over anhydrous potassium carbonate, filtered, and the oil which remains on driving off the ether fractionated. Owing to the evolution of cyanogen and hydrocyanic acid, this preparation must be carried out in a good fume cupboard. 

—65% theoretical (13 gms.). Colourless oil odour resembling that of benzaldehyde or nitrobenzene insoluble in water soluble in ether B.P. 191°. (B-, 17, 2653. See also 0. S., IV., 69.) 

50 gms. (1 mol.) of copper sulphate crystals are dissolved in 200 c.es. of water, and 56 gms. (excess) of 96% potassium cyanide added to the warm solution. As cyanogen is evolved, the operation must be carried out in a good fume cupboard, and the fumes must on no account be inhaled, 20 gms. (1 mol.) of p-toluidine are then diazotised as in Preparation 397, and the diazo solution gradually added in a J hour, from a dropping funnel to the cuprous-potassium cyanide solution at 90°, the mixture being kept well shaken. The product is heated on a water bath for a ]- hour, and 

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