Concentrated Hydrochloric Acid Chloride, Cupric

Tetrafluoropyrazine has been converted to 2,3,5-trifluoro-6-hydrazinopyrazine and thence to 2-chloro- and 2-bromo-3,5,6-trifluoropyTazine by reaction with ferric chloride in concentrated hydrochloric acid and cupric bromide in aqueous... 

Anhydrous cupric sulphate is white but forms a blue hydrate and a blue aqueous solution. The solution turns yellow when treated with concentrated hydrochloric acid, dark blue with ammonia, and gives a white precipitate and brown solution when treated with potassium iodide. A yellow-brown aqueous solution of ferric chloride becomes paler on acidification with sulphuric or nitric... 

Alternative Method.—Cupric chloride would serve better than a mixture of salt and copper sulfate, but it is much more expensive. A still simpler way is to start with copper. Place a suitable quantity in a flask and add concentrated hydrochloric acid in the ratio given in the last exercise. Heat nearly to boiling and add concentrated nitric acid drop by drop through a separatory funnel. When most of the copper has dissolved, stop adding nitric acid, heat vigorously for a time, and pour into cold water containing sodium sulfite. Proceed as in the first method. The aqua regia converts some of the copper into cupric chloride, and this is reduced to the cuprous salt by the excess of copper. 

As in the case of ferric chloride, cupric chloride is only incompletely reduced by sulphur dioxide in concentrated hydrochloric acid solution, but in aqueous solution this forms an excellent method for the preparation of cuprous chloride ... 

It has also been shown that in the presence of concentrated hydrochloric acid sulphur can reduce a hot solution of cupric chloride in accordance with the equation ... 

C 2-Bromo-4-methylbenzaldehyde A 3-1. three-necked flask is equipped with an efficient stirrer, a dropping funnel (Note 2), and a thermometer. The aqueous 10% formaldoxime prepared in step A is placed in the flask, and to it are added 6 5 g (0.026 mole) of hydrated cupric sulfate, 1.0 g. (0 0079 mole) of sodium sulfite, and a solution of 160 g of hydrated sodium acetate in 180 ml. of water The solution is maintained at 10-15° by means of a cold-water bath and stirred vigorously. The neutral diazonium salt solution prepared in step B is slowly introduced below the surface of the formaldoxime solution (Notes 3 and 4). After the addition of the diazonium salt solution is complete, the stirring is continued for an additional hour and then the mixture is treated with 230 ml. of concentrated hydrochloric acid. The stirrer and the dropping funnel are replaced by stoppers, and the mixture is gently heated under reflux for 2 hours The flask is set up for steam distillation, and the reaction product is steam-distilled. The distillate is saturated with sodium chloride, extracted with three 150-ml portions of ether, and the ethereal extracts are washed successively with three 20-ml portions of a saturated sodium chloride solution, three 20-ml. portions of an aqueous 10% sodium bicarbonate solution, and again with three 20-ml portions of a saturated sodium chloride solution. 

In this section, consideration will be given to the actual processes of acetal- or ketal-formation and not to the more indirect methods by which acetals and ketals of the polyhydric alcohols may be synthesized from compounds (e.g. derivatives of the monosaccharides) containing preformed alkylidene or arylidene groupings. The condensation of a carbonyl compound with a glycol is facilitated by acidic catalysts, and, since the reaction is reversible, by dehydration. The catalysts most frequently employed are concentrated sulfuric, hydrochloric and hydro-bromic acids, gaseous hydrogen chloride, zinc chloride and cupric sulfate others are phosphorus pentoxide, sulfosalicylic acid, and anhydrous sodium sulfate. The formation of benzylidene compounds is promoted less efficiently by phosphorus pentoxide than by either concentrated sulfuric acid or concentrated hydrochloric acid 1" the reaction is assisted by chloro- and nitro-substituents on the aromatic nucleus, but hindered by methyl- and methoxy-groups.18... 

Refining by other Methods.—Various other methods are available for the purification of copper. An example is the ready reduction of cuprous chloride by soft iron, a substance without action on cupric chloride. Aluminium slowly reduces a warm solution of cupric sulphate. Vigoroux 4 recommends a method depending on the action of aluminium on a solution of copper in concentrated hydrochloric acid. 

In presence of concentrated hydrochloric acid sulphur dioxide oxidizes cuprous chloride to cupric chloride, with deposition of sulphur ... 

In alkaline solution oxidation of ferrous iron is fairly rapid,8 but certain acids retard the reaction. Ferrous sulphate, for example, in the presence of free sulphuric acid, is very stable in air. Concentrated hydrochloric acid assists the oxidation, as also do traces of certain substances, such as platinic and cupric chlorides, palladium nitrate, etc.9... 

Diphenylyl-o-arsinic acid.— This is isolated by coupling sodium arsenite with diazotised o-aminodiphenyl in alkaline solution at 50° to 00° C. in the presence of a cupric salt. Yield, about 60 per cent. It crystallises from boiling water in bristle-like needles, M.pt. 206° C. When reduced in warm concentrated hydrochloric acid by sulphur dioxide in the presence of an iodide, it yields diphenylyl-o-dichloroarsine, a heavy oil, soluble in chloroform, insoluble in water. The chloride, with alcoholic potash, yields the oxide, an amorphous substance with no definite melting-point. 

Most likely the earliest solution work reported was a study of linewidth measurements of the Cu resonance signal in concentrated hydrochloric acid solution containing cuprous and cupric chloride. These studies afforded reasonable calculations for the bimolecular rate constant for the equilibrium electron-exchange process (Eq. 1) ... 

Cuprous chloride can be prepared by the reduction of cupric chloride by copper in the presence of concentrated hydrochloric acid. The soluble compound, HoCuCla, at first formed under these conditions, decomposes upon dilution, with the precipitation of the simple chloride. 

Materials Fehling s solution, solutions of glucose, of cupric chloride, of cupric sulphate, of potassium iodide, concentrated hydrochloric acid, copper filings, starch. 

The formation of sulphuric acid in this reaction has not been detected, although in presence of concentrated, but not of dilute, hydrochloric acid sulphur can reduce cupric chloride in accordance with the equation7... 

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