Cyanide ion, oxidation

After many years of development, the U.S. Department of Defense-funded project WP-1460 [67] was made a significant progress. In 2007, Idaho National Laboratory completed a continuous process of electrochemical synthesis of the key intermediate 2,2-nitroethyl potassium (KDNE) of DNPOH in the laboratory [68] from nitroethane. It was believed that the electrochemical process to produce DNPOH could reduce more than 92 % of the waste, carbide or nickel alloy rods was used as electrodes instead of silver rods according to the U.S. patent [69]. With different voltages, anode oxidizes inactive chemical intermediates (such as ferro-cyanide ion) into active intermediates or oxidant (such as iron cyanide ion). Oxidants and nitro compounds react with nitrite ions to form a gem-dinitro product. Anode can oxidize ferrous cyanide continuously to produce lively iron cyanide ions, thus to provide enough iron cyanide ions for reaction. The scheme of synthesis is shown in Fig. 4.6. 

Silver has little tendency to formally lose more than one electron its chemistry is therefore almost entirely restricted to the + 1 oxidation state. Silver itself is resistant to chemical attack, though aqueous cyanide ion slowly attacks it, as does sulphur or a sulphide (to give black Ag S). hence the tarnishing of silver by the atmosphere or other sulphur-containing materials. It dissolves in concentrated nitric acid to give a solution of silver(I) nitrate. AgNOj. 

Probably the most extensively applied masking agent is cyanide ion. In alkaline solution, cyanide forms strong cyano complexes with the following ions and masks their action toward EDTA Ag, Cd, Co(ll), Cu(ll), Fe(ll), Hg(ll), Ni, Pd(ll), Pt(ll), Tl(lll), and Zn. The alkaline earths, Mn(ll), Pb, and the rare earths are virtually unaffected hence, these latter ions may be titrated with EDTA with the former ions masked by cyanide. Iron(lll) is also masked by cyanide. However, as the hexacy-anoferrate(lll) ion oxidizes many indicators, ascorbic acid is added to form hexacyanoferrate(ll) ion. Moreover, since the addition of cyanide to an acidic solution results in the formation of deadly... 

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). 

Indeed the cobalt(III) ion is sufficientiy unstable in water to result in release of oxygen and formation of cobalt(II) ion. Under alkaline conditions the oxidation is much more facile and in the presence of complexing agents, eg, ammonia or cyanide, the oxidation may occur with ease or even spontaneously. 

Other ions, eg, ferrate, chloride, and formate, are determined by first removing the cyanide ion at ca pH 3.5 (methyl orange end point). Iron is titrated, using thioglycolic acid, and the optical density of the resulting pink solution is measured at 538 nm. Formate is oxidized by titration with mercuric chloride. The mercurous chloride produced is determined gravimetricaHy. Chloride ion is determined by a titration with 0.1 Ai silver nitrate. The end point is determined electrometricaHy. 

A very useful procedure for introducing a cyano group into a pyridazine ring is the Reissert-type reaction of the A/-oxide with cyanide ion in the presence of an acyl halide or dimethyl sulfate. The cyano group is introduced into the a-position with respect to the A-oxide function of the starting compound. The yields are, however, generally poor. In this way, 6-cyanopyridazines (111) can be obtained from the corresponding pyridazine 1-oxides (Scheme 33). 

Anodic oxidation of 1-methylpyrazole in the presence of cyanide ions yielded 33% (344) and 6% (345) no 3-cyano derivative was formed (78RTC35). 

As a group, the cyanides are among the most toxic and fast-acting poisons. (This is due to the cyanide ion which interferes with cellular oxidation.)... 

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. 

Formal oxidation of pyrrolidine to the succinimide stage affords a series of compounds used as anticonvulsant agents for treatment of seizures in petit mal epilepsy. Knoevnagel condensation of benzaldehyde with ethyl cyanoacetate affords the unsaturated ester, 9. Conjugate addition of cyanide ion leads to the di-nitrile ester (10). Hydrolysis in mineral acid affords the succinic acid (11), presumably by decarboxylation of the intermediate tricarboxyllie acid. Lactamization with methylamine gives phensuximide (12). ... 

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. 

These major routes to quinoxalmecarbonitriles have been covered already by primary synthesis (Chapter 1), by cyanalysis of halogenoquinoxalines (Section 3.2.5), by deoxidative cyanation of quinoxaline N-oxides (Section 4.6.2.2), by cyanolysis of nitroquinoxalines (Section 6.1.2.2), from primary quinoxalina-mines by a Sandmeyer-type reaction (Section 6.3.2.3), from quaternary ammonio-quinoxalines with cyanide ion (Section 6.3.2.4), and by dehydration of quinoxalinecarboxamides (Section 7.4.2). Those remaining preparative routes that have been used recently are illustrated in the following examples. 

These are thermodynamically relatively weak oxidants (Table 18) and their action is relatively restricted, for example, to inorganic ions of moderate reducing power such as iodide, to polyfunctional organic compounds such as hydroxy-acids, and, in the cases of Ag(I) and Cu(II), to CO and H2. Fe(III) is particularly affected by hydrolysis and all these oxidants form complexes with suitable ligands. Cyanide ion and 1,10-phenanthroline form strong complexes with Fe(III) which greatly affect its behaviour. Tris-l,10-phenanthrolineiron(III) (ferriin) displays... 

The displacement of CN by RS in surprising since C-labelled cyanide ion does not exchange with unlabelled ferricyanide . Wiberg et have shown that no exchange occurs under the conditions of the oxidation and that the effect of added cyanide is to be attributed to nucleophilic addition of cyanide to the thiol, viz. 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

Several alternative procedures have been developed in which other reagents replace carbon monoxide as the migration terminus.11 The most generally applicable of these methods involves the use of cyanide ion and trifluoroacetic anhydride (TFAA). In this reaction the borane initially forms an adduct with cyanide ion. The migration is induced by N-acylation of the cyano group by TFAA. Oxidation and hydrolysis then give a ketone. 

The reaction of aldehydes with MnOz in the presence of cyanide ion in an alcoholic solvent is a convenient method of converting aldehydes directly to esters.214 This reaction involves the cyanohydrin as an intermediate. The initial oxidation product is an acyl cyanide, which is solvolyzed under these reaction conditions. 

The mineral, sphalerite, on account of its resistance to oxidation, contributes very little of Zn2+ through dissolution. In this case, zinc sulfate is added and the reaction, which is shown in the parenthesis, is pressed into proceeding from right to left (i.e., PhS + Zn2+ —> ZnS +Pb2+). This is equivalent to saying deactivation of sphalerite. Besides Pb2+, Cu2+ is also known to give rise to activation. In this case, cyanide ions are introduced into the system. The stability of Cu(CN)2, relative to Zn(CN)2- results in ratios of dissolved Cu to Zn such that activation cannot occur. 

---