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cyanide(sī`ənīd'), chemical compound containing the cyano groupcyano group
, in chemistry, functional group that consists of a carbon atom joined to a nitrogen atom by a triple bond; it can be joined to an atom or another group by a single bond to the carbon atom. When a cyano group is joined to hydrogen, it forms hydrogen cyanide.
..... Click the link for more information. , -CN. Cyanides are salts or esters of hydrogen cyanidehydrogen cyanide,
HCN, colorless, volatile, and extremely poisonous chemical compound whose vapors have a bitter almond odor. It melts at −14°C; and boils at 26°C;. It is miscible in all proportions with water or ethanol and is soluble in ether.
..... Click the link for more information. (hydrocyanic acid, HCN) formed by replacing the hydrogen with a metal (e.g., sodium or potassium) or a radical (e.g., ammonium or ethyl). The most common and widely used cyanides are those of sodium and potassium; they are often referred to simply as "cyanide." Both are white, crystalline, chemically active compounds. They are used as insecticides, in making pigments, in metallurgy (e.g., electroplating and case hardening), and in refining gold and silver by the cyanide processcyanide process
method for extracting gold from its ore. The ore is first finely ground and may be concentrated by flotation; if it contains certain impurities, it may be roasted.
..... Click the link for more information. . Organic cyanides are called nitriles. The ethyl ester of hydrogen cyanide (CH3CH2CN) is called variously ethyl cyanide, propionitrile, propane nitrile, nitrilopropane, and cyanoethane; propane nitrile is the approved name in the nomenclature system for organic chemistry adopted by the International Union of Pure and Applied Chemistry (IUPAC). Most cyanides are deadly poisons that cause respiratory failure. Symptoms of cyanide poisoning include an odor of bitter almond on the breath, dizziness, convulsions, collapse, and, often, froth on the mouth. In case of cyanide poisoning a doctor should be summoned immediately. If the poison was swallowed, vomiting should be induced. Artificial respiration should be used if needed.
a salt of hydrocyanic acid. The cyanide salts of the alkali metals MCN and the alkaline-earth metals M(CN)2, where M is a metal, are thermally stable but are hydrolyzed in aqueous solutions. The cyanides of the heavy metals are thermally unstable and, with the exception of Hg(CN)2, are insoluble in water.
The oxidation of cyanides leads to the formation of cyanates; for example, 2KCN + O2 → 2KOCN. Many metals upon the action of an excess of potassium cyanide or sodium cyanide yield complexes. This proves useful in the extraction of gold and silver from ores (cyanidation, cyanide process):
4NaCN + 2Au + ½O2 + H2O → 2Na[ Au(CN)2] + 2NaOH
Gold and silver are separated from solution by electrodeposition or by the action of metallic zinc. Solutions of the cyanide complexes of gold, silver, zinc, and other metals are used in electroplating technology for the production of coatings. Cyanides are also used in organic synthesis, for example, in the production of nitriles, and as catalysts (in benzoin condensation).
Cyanides are extremely toxic. (For information on the effect of cyanides on the organism and on safety measures when handling them, seeHYDROCYANIC ACID.)
REFERENCESBobkov, S. S., and S. K. Smirnov. Sinil’naia kislota. Moscow, 1970.
Zil’berman, E. N. Reaktsii nitrilov. Moscow, 1972.
Tomilov, A. P., and S. K. Smirnov. Adipodinitril i geksamet ilendiamin. Moscow, 1974.
Williams, H. E. Cyanogen Compounds, 2nd ed. London, 1948.
Migrdichian, V. The Chemistry of Organic Cyanogen Compounds. New York, 1947.
Methoden der Organischen Chemie (Houben-Weyl), 4th ed., vol. 8. Stuttgart, 1952.
S. K. SMIRNOV