Cuprous cyanide solution

Cuprous cyanide solution. The most satisfactory method is to dissolve the cuprous cyanide (1 mol) in a solution of technical sodium cyanide (2 5-2-6 mols in 600 ml. of water). If it is desired to avoid the preparation of solid cuprous cyanide, the following procedure may be adopted. Cuprous chloride, prepared from 125 g. of copper sulphate crystals as described under 1 above, is suspended in 200 ml. of water contained in a 1-litre round-bottomed flask, which is fitted with a mechanical stirrer. A solution of 65 g. of technical sodium cyanide (96-98 per cent.) in 100 ml. of water is added and the mixture is stirred. The cuprous chloride passes into solution with considerable evolution of heat. As the cuprous cyanide is usually emplo3 ed in some modification of the diazo reaction, it is usual to cool the resulting solution in ice. 

Benzonitrile (phenyl cyanide). Prepare a cuprous cyanide solution in a 500 ml. round-bottomed flask as above, but use the following quantities 65 g. of crystallised copper sulphate in 205 ml. of water, 18 g. of sodium bisulphite in 52 ml. of water, and 18 g. of potassium cyanide in... 

While the cuprous cyanide solution is warmed gently (to 60°-70°) on the water bath, a solution of p-tolyldiazonium chloride is prepared as follows Heat 20 g. of p-toluidine with a mixture of 50 g. of concentrated hydrochloric acid and 150 c.c. of water until dissolution is complete. Immerse the solution in ice-water and stir vigorously with a glass rod so that the toluidine hydrochloride separates as far as possible in a microcrystalline form. Then cool the mixture in ice and diazotise with a solution of 16 g. of sodium nitrite in 80 c.c. of water, added until the nitrous acid test with potassium iodide-starch paper persists. The diazonium chloride solution so obtained is poured during the course of about ten minutes into the warm cuprous cyanide solution, which is meanwhile shaken frequently. After the diazo-solution has been added the reaction mixture is heated under an air condenser on the water bath fox a further quarter of an hour, and then the toluic nitrile is separated by distillation with steam (fume chamber, HCN ). The nitrile (which passes over as a yellowish oil) is extracted from the distillate with ether, the p-cresol produced as a by-product is removed by shaking the ethereal extract twice with 2 A-sodium hydroxide solution, the ether is evaporated,... 

If several runs are to be made it may be more convenient to prepare a large quantity of cuprous cyanide solution, since this appears to be stable for several days. 

B. Preparation of o-tolunitrile While the cuprous cyanide solution is cooling, 428 g. of o-toluidine is mixed in a 20-I. crock with 1 1. of commercial 28 per cent hydrochloric acid (sp. gr. x.14) and enough cracked ice, about 4 kg., to bring the temperature of the mixture to o°. A solution of 280 g. of sodium nitrite in 800 cc. of water is added, with stirring, to the resulting suspension of o-toluidine hydrochloride, the temperature being kept at o 50 by the addition of cracked ice. The addition of the nitrite occupies about fifteen minutes at the end of the operation, the mixture must show a distinct and permanent reaction for free nitrous acid on testing with starch iodide paper (Note 3). The final volume of the solution is 5-0 1. The mixture is now... 

The replacement of aromatic amino groups by cyanide is easily accomplished by the action of cuprous cyanide on the diazonium compound (Sandmeyer). The procedure is illustrated by the preparation of o- and tolunitriles each is obtained in 64% to 70% yield. Several features are noteworthy. The diazonium solution is neutralized with sodium carbonate before treatment with cuprous cyanide solution so that the liberation of hydrogen cyanide is avoided. Also, vigorous stirring in the presence of an inert solvent is required during the addition of the cold neutralized diazonium solution to the cold cuprous cyanide solution so that the decomposition proceeds without violence. Methods for the preparation of cuprous cyanide have been described. ... 

A solution of cuprous chloride is prepared from 160 g. of copper sulfate in accordance with directions given in Org. Syntheses Coll. Vol. 1, 170 (1941). This solution is added to a solution of 80 g. of sodium cyanide in 125 ml. of water, and 60 g..of anhydrous sodium carbonate is added to the resulting mixture. p -Aminobenzoic acid (40 g., 0.29 mole), dissolved in a mixture of 70 g. of concentrated hydrochloric acid, 100 ml. of water, and 300 g. of ice, is diazotized by the addition at 0-5° of 20 g. (0.29 mole) of sodium nitrite in 50 ml. of water. The sodium and cuprous cyanide solution prepared above is heated to 50-60°, and the diazonium salt solution is added to it with stirring during the course of 10-15 minutes. The mixture is held... 

While the cuprous cyanide solution is further gently heated up to about 60-70° on the water-bath, the diazotoluenechloride solu-... 

---