Cyanogen bromide solution preparation

Dissolve a quantity of the material, containing about 1 mg of nicotinamide, in 10 ml of water, add 2 5 ml of concentrated hydrochloric acid and heat on a water-bath under a reflux condenser for one hour. Cool, adjust the pH of the liquid to 6 5 with 7 5N sodium hydroxide, using bromothymol blue solution as external indicator, add 25 ml of solution of standard pH 6 2 and dilute to 100 ml with water. Transfer 5 ml of this solution to each of two 25-ml flasks and heat at 80° in the dark for ten minutes. Cool, add to one flask 2 ml of cyanogen bromide solution (prepared by just decolorising freshly prepared saturated brornine water by the gradual addition of 10 per cent potassium cyanide solution the... 

A neutral solution of 28 grams of 8-amino-5-acetamido-4-hydroxyphenyl-arsinic acid (p. 309) in dilute aqueous sodium hydroxide is diluted to ISO c.c. and rapidly added to an aqueous suspension of cyanogen bromide (freshly prepared from 18 grams of bromine) and the whole well stirred. After standing for about an hour the product is acidified with acetic acid, the brown precipitate treated in alkaline solution with charcoal, and reprecipitated. "White, prismatic needles result (20 grams yield), readily soluble in alkalis and dilute mineral acids. 

Dimethyl-6-methylamino-5-quinoxalinamine (175) (prepared freshly as an ethanolic solution by catalytic hydrogenation of the corresponding nitro compound) and cyanogen bromide gave 3,4,8-trimethyl-3//-imidazo-[4,5-/]quinoxalin-2-amine (176) (20°C, 3.5 h 75%) the analogous... 

A convenient and quick way to prepare 1-bromoalkynes consists of adding an ethereal solution of cyanogen bromide to a strongly cooled solution of a metallated (Li or MgX) [119] acetylene in an organic solvent (EtjO or THF). The method seems very general and excellent yields can be obtained provided that the ethereal solution of BrC N (which is prepared from an aqueous solution) is dried well. The advantage of this method over the introduction with elemental bromine is that CC double bonds in the acetylenic compounds do not react... 

Cyanogen bromide has been prepared from an aqueous solution of potassium cyanide and bromine at o 3,1 and by the action of bromine on moist mercuric cyanide.2... 

A versatile route to 2-aminooxadiazoles (92), which generally proceeds in higher yield than oxidation of thiosemicarbazides (82), is the cyclization in aqueous or alcoholic solution of l-acyl-2-cyanohydrazines (91) prepared from acylhydrazines and cyanogen bromide (Scheme 16). Alternatively, hydrazines (91) are obtained by acylation of cyanohydrazines (66EGP52668). 

Caution Prepare this solution in a hood, as cyanogen bromide volatilizes at room temperature, and the vapor is highly irritating and poisonous. 

Acetylation of thioxopurines with cyanogen bromides similarly produces thio-cyanatopurines. Thus 2-, 6- and 8-thiocyanatopurines may be prepared from the corresponding thioxopurines in sodium hydroxide solution at 0 °C with cyanogen bromide (67CPB909). 

The manufacture of cyanogen bromide is carried out in large metal vessels in which a solution of the three salts is first prepared. 30% sulphuric acid at a temperature of 30°C. is then slowly run in. At the end of the reaction the product is separated by distillation. Yield 75%. ... 

This compound may be prepared either by the action of cyanogen bromide on an alcoholic solution of benzyl cyanide in presence of sodium ethylate, according to the equation ... 

In carrying out this determination, a weighed quantity of cyanogen bromide is treated with an excess of hydriodic acid solution, which is prepared by dissolving 10 gm. potassium iodide in 100 ml. of a 5% solution of acetic acid. The iodine liberated is titrated with a decinormal solution of sodium thiosulphate. 

Tribromo-l,3,5-triazine (cyanuric bromide) has no industrial importance. It is prepared in 60% yield by the addition of aluminum tribromide to a solution of cyanogen bromide in nitromethane at 40 - 60"C.220 Cyanuric iodide, which cannot be prepared by the trimeriza-tion of cyanogen iodide, can be obtained by the halogen-exchange reaction of cyanuric chloride and hydrogen iodide (cf. Section 2.3.1.5.5.l.l.l.)221... 

The preparation of cyanogen azide from cyanogen bromide and sodium azide in anhydrous medium has recently been described.339 In aqueous solution, further involvement of a second azide ion leads to the sodium salt of 5-azidotetrazole.339 The influence of solvent on these reactions... 

Small quantities of nikethamide may be determined by the cyanogen bromide method for nicotinic acid using standards prepared by diluting a 0-1 per cent aqueous solution of nikethamide. 

Before the development of the cyanamide process for the fixation of nitrogen, cyanamide was prepared by the interaction of cyanogen chloride er bromide (from the action of the halogen on potassium cyanide) with ammonia in water or ether solution. 

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