Reduction of cyanides

Cyanide reduction with hydrogen peroxide is effective in reducing cyanide. It has been applied on a less frequent basis within this industry, due to the fact that there are high operating costs associated with hydrogen peroxide generation. The reduction of cyanide with peroxide occurs in two steps and yields C02 and ammonia ... 

Amines of type (39) can be made by reduction of cyanides (40) and these in turn by the Michael reaction. Base catalysis is required in this synthesis as RO is a better nucleophile than ROH. 

In metallurgical processing in the purification of certain elements from their ores, for the recovery of certain elements from mixtures of other materials, and increasingly in the reduction of cyanides in leachate from gold mining. 

Reduction of cyanide to aminocarbyne and pathway for isomerisation of methyleneamide to aminocarbyne.. e,. H ... 

The opposite result was obtained in analyzing reduction of cyanide complexes [6]. In those cases, one net reaction involving Cd(CN) was used. However, the EAC formulas, obtained for cyanide solutions of different concentrations, were also different Cd(CN)2 at smaller and Cd(CN) at larger cyanide concentrations. A similar situation arose in studying silver electrodeposition from cyanide solutions [7]. One of the main reasons limiting the application of these methods to the reduction of labile complexes is that components of such systems cannot be... 

As two toxics are concerned, two extractant-trapping agent couples have been identified and their performances optimized (Figure 8.16). A continuous RDE process has been successfully tested on a laboratory-scale mixer-settler battery, allowing the reduction of cyanide concentration by one order of magnitude. 

FIGURE 14.55 Reduction of cyanides using lithium aluminum hydride. 

Dichloroacetic acid is produced in the laboratory by the reaction of chloral hydrate [302-17-0] with sodium cyanide (31). It has been manufactured by the chlorination of acetic and chloroacetic acids (32), reduction of trichloroacetic acid (33), hydrolysis of pentachloroethane [76-01-7] (34), and hydrolysis of dichloroacetyl chloride. Due to similar boiling points, the separation of dichloroacetic acid from chloroacetic acid is not practical by conventional distillation. However, this separation has been accompHshed by the addition of a eotropeforming hydrocarbons such as bromoben2ene (35) or by distillation of the methyl or ethyl ester. 

Cyanide Wastes. Ozone is employed as a selective oxidant in laboratory-scale synthesis (7) and in commercial-scale production of specialty organic chemicals and intermediates such as fragrances, perfumes (qv), flavors, antibiotics (qv), hormones (qv), and vitamins (qv). In Japan, several metric tons per day (t/d) of piperonal [120-57-0] (3,4-methylenedioxybenzaldehyde) is manufactured in 87% yield via ozonolysis and reduction of isosafrole [93-16-3], Piperonal (or heHotropine [120-57-0]) has a pleasant odor and is used in perfumery. Oleic acid [112-80-1/, CH3(CH2 )7CH—CH(CH2 ). C02H, from tall oil (qv) is ozonated on a t/d scale to produce pelargonic, GgH2yG02H, and azelaic, H02G(GH2)yG02H, acids. Oleic acid also is ozonated in Japan... 

Dehalogenation of monochlorotoluenes can be readily effected with hydrogen and noble metal catalysts (34). Conversion of -chlorotoluene to Ncyanotoluene is accompHshed by reaction with tetraethyl ammonium cyanide and zero-valent Group (VIII) metal complexes, such as those of nickel or palladium (35). The reaction proceeds by initial oxidative addition of the aryl haHde to the zerovalent metal complex, followed by attack of cyanide ion on the metal and reductive elimination of the aryl cyanide. Methylstyrene is prepared from -chlorotoluene by a vinylation reaction using ethylene as the reagent and a catalyst derived from zinc, a triarylphosphine, and a nickel salt (36). 

Electroplating. Aluminum can be electroplated by the electrolytic reduction of cryoHte, which is trisodium aluminum hexafluoride [13775-53-6] Na AlE, containing alumina. Brass (see COPPERALLOYS) can be electroplated from aqueous cyanide solutions which contain cyano complexes of zinc(II) and copper(I). The soft CN stabilizes the copper as copper(I) and the two cyano complexes have comparable potentials. Without CN the potentials of aqueous zinc(II) and copper(I), as weU as those of zinc(II) and copper(II), are over one volt apart thus only the copper plates out. Careful control of concentration and pH also enables brass to be deposited from solutions of citrate and tartrate. The noble metals are often plated from solutions in which coordination compounds help provide fine, even deposits (see Electroplating). 

High yields of optically active cyanohydrins have been prepared from hydrogen cyanide and carbonyl compounds using an enzyme as catalyst. Reduction of these optically active cyanohydrins with lithium aluminum hydride in ether affords the corresponding substituted, optically active ethanolamine (5) (see Alkanolamines). 

Methylsuccinic acid has been prepared by the pyrolysis of tartaric acid from 1,2-dibromopropane or allyl halides by the action of potassium cyanide followed by hydrolysis by reduction of itaconic, citraconic, and mesaconic acids by hydrolysis of ketovalerolactonecarboxylic acid by decarboxylation of 1,1,2-propane tricarboxylic acid by oxidation of /3-methylcyclo-hexanone by fusion of gamboge with alkali by hydrog. nation and condensation of sodium lactate over nickel oxide from acetoacetic ester by successive alkylation with a methyl halide and a monohaloacetic ester by hydrolysis of oi-methyl-o -oxalosuccinic ester or a-methyl-a -acetosuccinic ester by action of hot, concentrated potassium hydroxide upon methyl-succinaldehyde dioxime from the ammonium salt of a-methyl-butyric acid by oxidation with. hydrogen peroxide from /9-methyllevulinic acid by oxidation with dilute nitric acid or hypobromite from /J-methyladipic acid and from the decomposition products of glyceric acid and pyruvic acid. The method described above is a modification of that of Higginbotham and Lapworth. ... 

The procedure given above for the preparation of methanesulfonyl cyanide essentially is a combination of the sulfite reduction of a sulfonyl... 

This method is an adaptation of that of Dengel. -Methoxy-phenylacetonitrile can also be prepared by the metathetical reaction of anisyl chloride with alkali cyanides in a variety of aqueous solvent mixtures by the nitration of phenylaceto-nitrile, followed by reduction, diazotization, hydrolysis, and methylation 1 by the reduction of ct-benzoxy- -methoxy-phenylacetonitrile (prepared from anisaldehyde, sodium cyanide, and benzoyl chloride) and by the reaction of acetic anhydride with the oxime of -methoxyphenylpyruvic acid. ... 

Contents Introduction and Principles. - The Reaction of Dichlorocarbene With Olefins. - Reactions of Dichlorocarbene With Non-Olefinic Substrates. -Dibromocarbene and Other Carbenes. - Synthesis of Ethers. - Synthesis of Esters. - Reactions of Cyanide Ion. - Reactions of Superoxide Ions. - Reactions of Other Nucleophiles. - Alkylation Reactions. - Oxidation Reactions. - Reduction Techniques. - Preparation and Reactions of Sulfur Containing Substrates. -Ylids. - Altered Reactivity. - Addendum Recent Developments in Phase Transfer Catalysis. 

Enamine salts react with many nucleophilic reagents. The reaction with the cyanide ion is noteworthy. l-Methyl-2-ethyl-2-cyanopyrrolidine (170) is formed on treatment of alkali cyanide with l-methyl-2-ethyl-.d -pyrrolin-ium perchlorate (242). The reduction of the tertiary nitrile (170) with... 

Iodide ions reduce Cu to Cu , and attempts to prepare copper(ll) iodide therefore result in the formation of Cul. (In a quite analogous way attempts to prepare copper(ll) cyanide yield CuCN instead.) In fact it is the electronegative fluorine which fails to form a salt with copper(l), the other 3 halides being white insoluble compounds precipitated from aqueous solutions by the reduction of the Cu halide. By contrast, silver(l) provides (for the only time in this triad) 4 well-characterized halides. All except Agl have the rock-salt structure (p. 242). Increasing covalency from chloride to iodide is reflected in the deepening colour white yellow, as the... 

The starting material was prepared in a yield of 5B% by reduction of the corresponding cyanohydrin. It in turn was prepared from 1-(2-phenylethyl)-4-plperidone and potassium cyanide to give the cyanohydrin which was reduced by lithium aluminum hydride. 

Some disadvantages stem from the same phenomena impeded diffusion reduces the maximum practical rate of plating to well below that possible with aquocation baths. The cyanide ion is not entirely stable both oxidation and reduction products accumulate, including carbonate. Carbonate is also formed in the alkaline cyanide baths (all cyanide baths are alkaline except some based on aurocyanides) by absorption of COj from the air, and it is necessary either to replace or purify baths periodically. Much has been made of the toxicity of cyanides, but the other process solutions used in plating are generally extremely toxic and corrosive or caustic, and it is necessary to treat them all with respect. 

The reduction of carbonyl compounds by reaction with hydride reagents (H -) and the Grignard addition by reaction with organomagnesium halides (R - +MgBr) are examples of nucleophilic carbonyl addition reactions. What analogous product do you think might result from reaction of cyanide ion with a ketone ... 

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