Thiocyanation with copper thiocyanate

The coupling of aryl halides with copper is called the Ullmann reaction.m The reaction is of broad scope and has been used to prepare many symmetrical and unsymmetrical biaryls.187 When a mixture of two different aryl halides is used, there are three possible products, but often only one is obtained. For example, picryl chloride and iodobenzene gave only 2,4,6-trinitrobiphenyl.188 The best leaving group is iodo, and the reaction is most often done on aryl iodides, but bromides, chlorides, and even thiocyanates have been used. 

Iron. Excess iron in wines causes cloudiness, interferes with the color, and can impair flavor. The mechanism of ferric phosphate precipitation has been intensively studied, and numerous colorimetric methods have been developed. For routine purposes the color developed with thiocyanate is adequate (6,9), but many enologists prefer the orthophenanthro-line procedures (3, 4, 6, 22). Meredith et al. (Ill) obtained essentially the same results for iron using 2,4,6-tripyridyl-s-triazine (TPTZ) to develop the color. Atomic absorption spectrophotometry can be used but, as with copper, corrections for reducing sugar and ethanol are necessary (51). 

If thiocyanate is not added, the thiosulfate should be standardized with copper metal under the same conditions as for the determination of copper. ... 

With other halides, the reaction is conveniently performed by treatment of the alkylthdlium compound with the appropriate copper(I) halide. The product yield is increased by the addition of potassium halide.jhe thallium moiety can also be replaced by other groups, similarly to the arylthallium compounds. The cyano group is introduced by reaction with copper(I) cyanide.lSi the thiocyano group by reaction with potassium and/or copper thiocyanate>5i.i52 and the selenocyano group by treatment with potassium selenocyanate. 

Bipyridyl and phenanthroline give polymeric 1 1 complexes with copper(II) chloride (597). The existence of the dimeric ion [(bipy)Cu(0H)20u(bipy)] + in solution has been established (177, 566) and it has been isolated as the lilac perchlorate (498). The species (bipy)Cu + has surprisingly large affinity for ligands other than OH (370). The di-p.-hydroxo cation considered above has now been prepared with a variety of counter ions the corresponding phenanthroline salts are also known. There is no evidence of antiferromagnetic interaction between the copper(II) ions even at 80°K (321). When the counter ion is iodide or thiocyanate there is evidence for metal ion-counter ion interaction. 

Barium thiocyanate was first prepared by Berzelius, who roasted barium hexacyanoferrate(II) with sulfur. It has also been obtained by reaction of barium carbonate with a solution of thiocyanic acid, by conversion of ammonium thiocyanate through the copper (I) thiocyanate by consecutive reactions with copper(I) chloride and barium hydroxide, by treatment of Prussian blue with barium sulfide, and by reaction of barium sulfide, sulfur, and cyanamide. The procedure described below makes possible the preparation of barium thiocyanate in any desired quantity from barium hydroxide and ammonium thiocyanate as starting materials. The 3-hydrate, " which is obtained first, is dehydrated readily to yield anhydrous barium thiocyanate. 

The sulphur-containing substrates thiocyanate and thiourea undergo oxidation by 2,9-dimethyl-l,10-phenanthroline (dmp) complexes of copper(n). As with beds, this ligand forms thermodynamically stable and brightly coloured bis-complexes with copper(i), which is otherwise unstable in aqueous perchlorate media. Under the conditions used, the oxidant is mainly in the form [Cu(dmp)2] . Oxidation of thiocyanate obeys a rate law... 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenyiarsonium chloride in an organic solvent. Titanium(IV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenyiarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates deterrnined spectrophotometricaHy. Cobalt, palladium, tungsten, niobium, and molybdenum have been deterrnined in a similar manner. In addition to their use for the deterrnination of metals, anions such as perchlorate and perrhenate have been deterrnined as arsonium salts. Tetraphenyiarsonium permanganate is the only known insoluble salt of this anion. 

Determination. The most accurate (68) method for the deterrnination of copper in its compounds is by electrogravimetry from a sulfuric and nitric acid solution (45). Pure copper compounds can be readily titrated using ethylene diamine tetracetic acid (EDTA) to a SNAZOXS or Murexide endpoint. lodometric titration using sodium thiosulfate to a starch—iodide endpoint is one of the most common methods used industrially. This latter titration is quicker than electrolysis, almost as accurate, and much more tolerant of impurities than is the titration with EDTA. Gravimetry as the thiocyanate has also been used (68). 

The importance of solvent effects in the preparation of perfluoroalkyzinc reagents is further illustrated in the reaction of perfluoroalkyl iodides with zinc-copper couple. In DMSO, DMF, and HMPA, the main products are the fluo-roolefins The formation of the fluoroolefin is facilitated when the reaction is carried out in the presence of potassium thiocyanate [30] (equation 21)... 

Internal stress of copper deposits may vary between —3.4MN/m (compressive) and -1- l(X)MN/m (tensile). In general, tensile stress is considerably lower in deposits from the sulphate bath than in those from cyanide solutions " , while pyrophosphate copper deposits give intermediate values. In cyanide solutions, tensile stress increases with metal concentration and temperature decreases if the free cyanide concentration is raised. P.r. current significantly lowers tensile stress. With some exceptions, inorganic impurities tend to increase tensile stress . Thiocyanate may produce compressive stress in cyanide baths . 

Copper(II) compounds. Many other metallic ions which are capable of undergoing oxidation by potassium iodate can also be determined. Thus, for example, copper(II) compounds can be analysed by precipitation of copper)I) thiocyanate which is titrated with potassium iodate ... 

Determination of copper as copper(I) thiocyanate Discussion. This is an excellent method, since most thiocyanates of other metals are soluble. Separation may thus be effected from bismuth, cadmium, arsenic, antimony, tin, iron, nickel, cobalt, manganese, and zinc. The addition of 2-3 g of tartaric acid is desirable for the prevention of hydrolysis when bismuth, antimony, or tin is present. Excessive amounts of ammonium salts or of the thiocyanate precipitant should be absent, as should also oxidising agents the solution should only be slightly acidic, since the solubility of the precipitate increases with decreasing pH. Lead, mercury, the precious metals, selenium, and tellurium interfere and contaminate the precipitate. 

The precipitate is curdy (compare silver chloride) and is readily coagulated by boiling. It is washed with dilute ammonium thiocyanate solution a little sulphurous acid or ammonium hydrogensulphite is added to the wash solution to prevent any oxidation of the copper)I) salt. 

The precipitate, collected in a sintered-glass (porosity No. 4) or porcelain filtering crucible, may be weighed more rapidly as follows. Wash the copper(I) thiocyanate five or six times with ethanol, followed by a similar treatment with small volumes of anhydrous diethyl ether, then suck the precipitate dry at the pump for 10 minutes, wipe the outside of the crucible with a clean linen cloth and leave it in a vacuum desiccator for 10 minutes. Weigh as CuSCN. 

Determination as copper (I) thiocyanate, CuSCN. The solution (100 mL) should be neutral or slightly acid (hydrochloric or sulphuric acid), and contain not more than 0.1 g SCN . It is saturated with sulphur dioxide in the cold (or 50 mL of freshly prepared saturated sulphurous acid solution added), and then treated dropwise and with constant stirring with about 60 mL of 0.1M copper sulphate solution. The mixture is again saturated with sulphur dioxide (or 10 mL of... 

Aryl sulfones have been prepared from sulfinic acid salts, aryl iodides and Cul. Unactivated thiocyanation has been accomplished with charcoal supported copper(I) thiocyanate." ... 

Finally, anions that are incompatible with oxidants will give rise to violent reactions with iodates. This goes for cyanides, thiocyanates and sulphides. In the last case, arsenic, antimony, copper and tin sulphides were the main ones cited. 

Figure 10 shows the instrumental setup used to implement the APP-CLS approach. It consists of (a) a CSTR that is a thermostated 10-mL glass reaction vessel accommodated in a commercially available spectrofluorimeter (a Hitachi F2000 model in this case) (b) a four-channel peristaltic pump with three channels used to dispense the reagent solutions and the fourth to keep the volume of the reaction mixture in the CSTR constant the three reagent solutions are as follows (1) 0.15 M hydrogen peroxide (2) 0.15 M sodium thiocyanate, 0.15 M sodium hydroxide, and 1.95 x 10 3 M luminol and (3) 6.0 x 10 4 M copper(II) sulfate ... 

Cul and CuSCN. Both Cul and CuSCN require copper in the monovalent state. This was achieved by complexing Cu2+ ions with thiosulfate, which also reduces Cu2+ to Cu+. Potassium iodide or thiocyanate served as an... 

Rate constants for the replacement of water by azide or thiocyanate from the five coordinate (2tyr 2his, 1H20) copper center in Fusarium galactose oxidase decrease with increasing pH, due to the greater difficulty of displacing OH- (312). 

Intimate mixtures of chlorates, bromates or iodates of barium, cadmium, calcium, magnesium, potassium, sodium or zinc, with finely divided aluminium, arsenic, copper carbon, phosphorus, sulfur hydrides of alkali- and alkaline earth-metals sulfides of antimony, arsenic, copper or tin metal cyanides, thiocyanates or impure manganese dioxide may react violently or explosively, either spontaneously (especially in presence of moisture) or on initiation by heat, friction, impact, sparks or addition of sulfuric acid [1], Mixtures of sodium or potassium chlorate with sulfur or phosphorus are rated as being exceptionally dangerous on frictional initiation. 

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