METAL CYANIDES

The most common salt of trade and utility is K CN. A convenient and safe method of preparation on a scale of 1-10 mmol is reduction of barium [ CJcarbonate with potassium azide at elevated temperatures the procedure is highly reproducible and gives radiochemical yields in the range of 90-98% . In this procedure an intimate mixture of barium [ C]-carbonate, potassium azide and carefully dried sea sand is heated at temperatures slowly increasing from 450 to 700 °C. The resulting crude product is acidified with 85% phosphoric acid, and H CN released is expelled with helium into a methanolic solution of potassium methoxide, from which the K CN is isolated in solid form by evaporation of the solvent. (Caution HCN is volatile and extremely toxic.) Sodium [ C]cyanide can be prepared the same way, except using methanolic sodium methoxide. Potassium [ C]-cyanide is indefinitely stable as a dry solid at ambient temperature the sodium salt is somewhat less so. 

Preparation of Compounds Labeled with Tritium and Carbon-14 Rolf Vc es, J. Richard Heys and Thomas Moenius 2009 John Wiley Sons, Ltd. ISBN 978-0-470-51607-2 

Larger quantities of alkali metal [ C]cyanides are produced in a four-step sequence by reduction of with hydrogen at 350 °C over a nickel catalyst to form [ C]methane. This intermediate reacts with ammonia at 1150°C over a platinum catalyst, and the resulting mixture of and NBU CN is trapped in an aqueous alkali hydroxide 

Two other frequently used metal salts are Cu CN and Zn( CN)2. The former is readily accessible in crystalline form in 80-90% yield by treatment of a weakly basic aqueous solution of sodium or potassium cyanide with excess CUSO4 5H2O in the presence of sodium hydrogensulfite at 20-60°C in radiochemical yields of 80-90%. The latter is conveniently obtained as a white precipitate in 90% yield upon treatment of an aqueous solution of with ZnCl2.  

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Magnesium Air, beryllium fluoride, ethylene oxide, halogens, halocarbons, HI, metal cyanides, metal oxides, metal oxosalts, methanol, oxidants, peroxides, sulfur, tellurium... 

Miscellaneous Reactions. Sodium bisulfite adds to acetaldehyde to form a white crystalline addition compound, insoluble in ethyl alcohol and ether. This bisulfite addition compound is frequendy used to isolate and purify acetaldehyde, which may be regenerated with dilute acid. Hydrocyanic acid adds to acetaldehyde in the presence of an alkaU catalyst to form cyanohydrin the cyanohydrin may also be prepared from sodium cyanide and the bisulfite addition compound. Acrylonittile [107-13-1] (qv) can be made from acetaldehyde and hydrocyanic acid by heating the cyanohydrin that is formed to 600—700°C (77). Alanine [302-72-7] can be prepared by the reaction of an ammonium salt and an alkaU metal cyanide with acetaldehyde this is a general method for the preparation of a-amino acids called the Strecker amino acids synthesis. Grignard reagents add readily to acetaldehyde, the final product being a secondary alcohol. Thioacetaldehyde [2765-04-0] is formed by reaction of acetaldehyde with hydrogen sulfide thioacetaldehyde polymerizes readily to the trimer. 

With secondary alkanolamines, aldehydes in the presence of K CO yield di-tertiary amines, which, on distillation, break down into a,P unsaturated amines and secondary amines. With a mono- or dialkanolamine, an alkaU metal cyanide, and an aldehyde or ketone, aminoacetonitriles are formed. 

Nitriles. Nitriles can be prepared by a number of methods, including ( /) the reaction of alkyl haHdes with alkaH metal cyanides, (2) addition of hydrogen cyanide to a carbon—carbon, carbon—oxygen, or carbon—nitrogen multiple bond, (2) reaction of hydrogen cyanide with a carboxyHc acid over a dehydration catalyst, and (4) ammoxidation of hydrocarbons containing an activated methyl group. For reviews on the preparation of nitriles see references 14 and 15. 

Dissolution of Silver. Silver is dissolved by oxidising acids and alkaU metal cyanide solutions in the presence of oxygen. The latter method is the principal technique for dissolving silver from ore. Silver has extensive solubiUty in mercury (qv) and low melting metals such as sodium, potassium, and their mixtures. Cyanide solutions of silver are used for electroplating and electroforming. The silver is deposited at the cathode either as pure crystals or as layers on a mandrel. 

ALkah metal cyanides catalyze the condensation of benzaldehyde to form benzoin. 

Basic copper carbonate is essentially iasoluble ia water, but dissolves ia aqueous ammonia or alkaU metal cyanide solutions. It dissolves readily ia mineral acids and warm acetic acid to form the corresponding salt solution. 

AH of these alkaH metal cyanides may be prepared by passing hydrogen cyanide into an aqueous solution of the hydroxide or by precipitating a... 

Cmde calcium cyanide [592-01-8] about 48 to 50 eq % sodium cyanide, is the only commercially important alkaline-earth metal cyanide, and output toimage has been greatiy reduced. This product, commonly called black cyanide, is marketed in flake form as a powder or as cast blocks under the trademarks Aero and Cyanogas of the American Cyanamid Co. 

The alkali metal cyanides MCN are produced by direct neutralization of HCN they crystallize... 

Cyan-hllrtung, /. Metal.) cyanide hardening, cyaniding. -hydrin, n. cyanohydrin. 

Toxic constituents such as heavy metals, cyanides, etc. ... 

The complex cyanides of transition metals, especially the iron group, are very stable in aqueous solution. Their high co-ordination numbers mean the metal core of the complex is effectively shielded, and the metal-cyanide bonds, which share electrons with unfilled inner orbitals of the metal, may have a much more covalent character. Single electron transfer to the ferri-cyanide ion as a whole is easy (reducing it to ferrocyanide, with no alteration of co-ordination), but further reduction does not occur. 

Interpretation of potential constants application to study of bonding forces in metal cyanide complexes and metal carbonyls, L. H. Jones and B. I. Swanson, Acc. Chem. Res., 1976,9,128-134 (27). 

Polynuclear transition metal cyanides such as the well-known Prussian blue and its analogues with osmium and ruthenium have been intensely studied Prussian blue films on electrodes are formed as microcrystalline materials by the electrochemical reduction of FeFe(CN)g in aqueous solutionThey show two reversible redox reactions, and due to the intense color of the single oxidation states, they appear to be candidates for electrochromic displays Ion exchange properties in the reduced state are limited to certain ions having similar ionic radii. Thus, the reversible... 

Another elegant synthesis route to borinato ligands and sandwich complexes uses cyanide degradation of otherwise prepared borinato complexes ( 6.5.3.3). The reactions proceed quantitatively to yield borinato ligands and insoluble metal cyanides ... 

Ludi A, Gudel HU (1973) Structural Chemistry of Polynuclear Transition Metal Cyanides. 14 1-21... 

Heterocyclic N-oxides such as pyridine, quinoline, or isoquinoline N-oxides can be converted into a mixture of 2- and some 4-cyanopyridines, 2- or 4-cyanoquino-lines, or 1-cyanoisoquinolines, in 40-70% yield, in a Reissert-Henze reaction, by activation of the N-oxide function by O-acylation [1] or O-alkylation [2, 3] followed by treatment with aqueous alkali metal cyanide in H2O or dioxane. 

In this work, the waste brewery yeast and Aspergillus niger were used for the adsorption of lead, copper and cadmium, and their cyanide complexes. Biosorption equilibrium was studied in a batch reactor with respect to pH, initial concentration of heavy metal and metal-cyanide complex. Biosorption equilibrium over the temperature range of 288K - 308K was investigated and the biosorption heat was evaluated. 

The biosorption capacity of Aspergillus niger was much greater than that of brewery yeast, and the biosorption capacity of metal-cyanide anion complexes was significantly lower than that of metal ion only. 

The biosorption reactions of heavy metals and metal-cyanide complexes were endothermic, and the heats of adsorption were in the range of 3.3-5.3 kcal-mol", which imply that both physical and chemical adsorptions are involved. 

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