Hydrogen cyanide, extraction

The following technique is described in U.S. Patent 2,541,104. A solution of 2.0 g of 3(a )-hydroxy-21-acetoxy-11,20-diketo-pregnane, which can be prepared as described in Helv. Chim. Acta 27, 1287 (1944), is treated in a mixture of 25 cc of alcohol and 6.4 cc of acetic acid at 0°C with 6.0 g of potassium cyanide. The solution is allowed to warm to room temperature and after 3 hours is diluted with water. The addition of a large volume of water to the alcohol-hydrogen cyanide mixture precipitates a gum which is extracted with chloroform or ethyl acetate. The extract is washed with water, and evaporated to small volume under reduced pressure. The crystalline precipitate (1.3 g) consists of 3(a ),20-dihvdroxy-20-cvano-21-acetoxy-11-keto-pregnane dec. 175° to 185°C. 

Acetonitrile and hydrogen cyanide are hy-products that may he recovered for sale. Acetonitrile (CH3CN) is a high polarity aprotic solvent used in DNA synthesizers, high performance liquid chromatography (HPLC), and electrochemistry. It is an important solvent for extracting butadiene from C4 streams. Table 8-1 shows the specifications of acrylonitrile, HCN, and acetonitrile. ... 

Analytical procedures sensitive to 2 ppm for styrene and 0.05 ppm or less for other items were used for examining the extracts. Even under these exaggerated exposure conditions no detectable levels of the monomers, of the polymer, or of other potential residuals were observed. The materials are truly non-food-additive by the FDA definitions. Hydrogen cyanide was included in the list of substances for analysis since it can be present at low levels in commercial acrylonitrile monomer, and it has been reported as a thermal decomposition product of acrylonitrile polymers. As shown here, it is not detectable in extracts by tests sensitive to... 

These results, considered in relation to the direct addition tests of monomer and hydrogen cyanide in the previous table, demonstrate that there is no reason to expect styrene monomer extraction into soft drinks, even at levels well below those we can measure analytically. They also reinforce our hydrogen cyanide data. Further, they indicate that these beverages are not more extractive of Lopac containers than the normal simulating solvents. The tests confirm the chemical safety of the containers as beverage packages. 

Agrawal V, Cherian L, Gupta VK. 1991. Extraction spectrophotometric method for the determination of hydrogen cyanide in environmental samples using 4-aminosalicylic acid. Intern J Environ Anal Chem 45 235-244. 

Potassium cyanide (KCN) is a white crystalline substance with a slight odor of bitter almonds. It is produced when hydrogen cyanide is absorbed in potassium hydroxide. It is used to extract gold and silver from their ores, in electroplating computer boards, and as an insecticide. Potassium cyanide is very toxic to the skin or when ingested or inhaled, and it is used as a source of cyanide (CN) gas in gas chambers. 

Cadmium may be measured by various instrumental analysis (see cadmium). Cyanide may be extracted by distilling an acidified solution of cadmium cyanide and then purging the liberated hydrogen cyanide with air, passing it into a scrubbing solution of caustic soda. Cyanide in the scrubbing solution is... 

Dissolve 20 g (0.13 mol) of the cyano ester in 100 ml of rectified spirit and add a solution of 19.2g (0.295 mol) of pure potassium cyanide (CAUTION) in 40 ml of water. Allow to stand for 48 hours, then distil off the alcohol on a water bath. Add a large excess of concentrated hydrochloric acid and heat under reflux for 3 hours. (CAUTION hydrogen cyanide evolved.) Dilute with water, saturate the solution with ammonium sulphate and extract with four 75 ml portions of ether. Dry the combined ethereal extracts with anhydrous sodium sulphate, and distil off the ether. Recrystallise the residual acid from excess concentrated hydrochloric acid, and dry in the air. The yield of pure 2,2-dimethylsuccinic acid, m.p. 141-142 °C, is 12 g (63%). The p.m.r. spectrum is recorded in trifluoracetic acid and reveals signals at S 1.48 (s, 6H, Me2) and 2.92 (s, 2H, CH2) the hydroxyl proton is not observed. 

A mixture of 288 g (4 mols) of isobutyraldehyde, 288 g of methanol was cooled to 10°C and 170 g (2 mols) of 36.6% formalin containing 8.5 g (3% based on isobutyraldehyde) of sodium hydroxide was added dropwise over a 55 minute period to produce alpha,alpha-dimethyl-beta-hydroxy-propionaldehyde. The mixture was stirred for an additional 2 hours at 10-15°C and then contacted with acetic acid to neutralize the catalyst. The excess isobutyraldehyde and methanol were stripped off at a kettle temperature of 50°C at 25 mm. To the residual a,a-dimethyl-beta-hydroxypropionaldehyde a mixture of 260 ml of methanol and 2 g (0.75%) sodium cyanide was added and the solution cooled to 10°C before adding 59.4 g (2.2 mols) of hydrogen cyanide dropwise over a 35 minute period to produce a,y-dihydroxy-p,p-dimethylbutyronitrile. The mixture was stirred at 10°C for one hour period and then contacted with acetic acid to neutralize the catalyst before stripping off the excess methanol to a kettle temperature of 45°C at 18 mm. The crude cyanohydrin was then hydrolysed by heating with 4 mols of concentrated hydrochloric acid at 80°C for 2 hours, then diluting with an equal volume of water and heating at 100°C for an additional 8 hours. The aqueous mixture was extracted continuously with ethylene dichloride. The solvent was... 

B. 2-Bromo-3-methylbenzoic acid. Caution This procedure must be carried out in a hood with a good draft, because poisonous hydrogen cyanide gas is evolved. In a 5-1. round-bottomed flask are placed 90 g. of potassium cyanide, 900 ml. of 2-ethoxyethanol (Note 3), 850 ml. of water, and the moist 2-bromo-4-nitrotoluene obtained above. A reflux condenser is attached, and the mixture is boiled for 16 hours (Note 4). To the hot, dark-red solution is then added 1.51. of water, and the mixture is acidified with concentrated hydrochloric acid. (Caution Hydrogen cyanide is evolved.) The acidified mixture is boiled for 15 minutes to expel hydrogen cyanide and then allowed to cool to 35-40°. Five grams of diatomaceous earth is stirred in, and the mixture is filtered through a Buchner funnel precoated with a little diatomaceous earth. The solid is discarded, and the filtrate is extracted three times with 200-ml. portions of chloroform. The chloroform extracts are combined and extracted with three 100-ml. portions of 5% ammonium carbonate solution. The basic extracts are combined, acidified with concentrated hydrochloric acid, and cooled in an ice bath. The oil which first forms soon crystallizes. 

The test may also be conducted with 2 ml of the soda extract. Carbonate, sulphite, and thiosulphate have no influence upon the reaction. Nitrite interferes, presumably owing to the oxidation of the hydrogen cyanide. In the presence of sulphide, the test is complicated by the precipitation of black iron(II) sulphide when sulphate is added to the alkaline solution. It is best to boil the solution containing the suspended iron(II) sulphide, acidify with hydrochloric acid, and boil again to expel most of the dissolved hydrogen sulphide upon adding a drop of iron(III) chloride solution, a blue precipitate is produced if cyanide is present. 

In addition to adenine, guanine was also produced in yields of 1% and 0.5%, respectively, by UV radiation of dilute aqueous solutions of hydrogen cyanide over 7 days at room temperature (B-65MI40901) and a biradical scheme has been proposed for this reaction (Scheme 63) (62PNA(48)1300). When liquid ammonia was heated with liquid hydrogen cyanide at 120 °C in an autoclave over 20 hours, a 10-15% yield of adenine was obtained (66JAP6610114) by extraction of the residual solid with water. 

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