Copper cuprous bromide

Copper cuprous bromide Bromallenes from 2-acetylenealeohols... 

Cuprous bromide. The solid salt may be prepared by dissolving 150 g. of copper sulphate crystals and 87 5 g. of sodium bromide dihydrate in 500 ml. of warm water, and then adding 38 g. of powdered sodium sulphite over a period of 5-10 minutes to the stirred solution. If the blue colour is not completely discharged, a little more sodium sulphite should be added. The mixture is then cooled, the precipitate is collected in a Buchner funnel, washed twice with water containing a little dissolved sulphurous acid, pressed with a glass stopper to remove most of the liquid, and then dried in an evaporating dish or in an air oven at 100 120°. The yield is about 80 g. 

A solution of cuprous bromide may be prepared either by dissolving the solid in hot constant boiling point hydrobromic acid or by refluxing a mixture of 63 g. of crystallised copper sulphate, 20 g. of copper turnings, 154 g. of sodium bromide dihydrate, 30 g. (16-3 ml.) of concentrated sulphuric acid and 1 litre of water for 3-4 hours. If the colour of the solution has not become yellowish after this period of heating, a few grams of sodium sulphite should be added to complete the reduction. 

Method 2. Prepare 40 g." of cuprous bromide according to Section 11,50,2 (about 75 g. of crystaUised copper sulphate are required) and dissolve it in 40 ml. of constant boihng point hydrobromic acid (48% HBr) contained in a 2 - 5 Utre rovmd-bottomed flask. 

Kupfer-bromid, n. copper bromide, specif, cupric bromide, copper(II) bromide, -bro-mtir, n. cuprous bromide, copper(I) bromide, -chlorid, n. copper chloride, specif, cupric chloride, copper(II) chloride, -chloriir, n. cuprous chloride, copper(I) chloride, -cyamd, Ti. copper cyanide, specif, cupric cyanide, copper(II) cyanide, -cyaniir, n. cuprous cyanide, copper(I) cyanide, -dom, m. slag from liquated copper, -draht, m. copper wire, -drahtnetz, n. copper gauze, -drehspane,... 

It is noteworthy that metallic copper or cuprous bromide used under nitrogen atmosphere shows only a very short induction time. This last result points out the inhibitor role of the oxygen of the air atmosphere and most likely the important role taken either by reduced species or by radical intermediates in the catalytic cycle. 

Method 1. Prepare a solution of cuprous bromide by refluxing 31-5 g. of crystallised copper sulphate, 10 g. of clean copper turnings, 77 g. of crystallised sodium bromide, 15 g. (8-2 ml.) of concentrated sulphuric acid and 500 ml. of water contained in a 2 5 litre round-bottomed flask over a flame for 3-4 hoims until the solution acquires a yellowish colour if the blue coloim is not discharged, add a few grams of sodium bisulphite to complete the reduction. 

The submitter used commercial cuprous bromide. The checkers prepared cuprous bromide by dissolving 600 g. (2.4 moles) of commercial copper sulfate crystals and 350 g. (3.4 moles) of sodium bromide in 2 1. of warm water the solution was stirred while 151 g. (1.2 moles) of solid sodium sulfite was added over a period of 10 minutes. Occasionally a little more sodium sulfite was required to discharge the blue color. The mixture was cooled, and the solid collected on an 8-in. Buchner funnel, washed once with water, pressed nearly dry, and then dried in... 

Triphenylstannane reduced the double bond in dehydro-)J-ionone in 84% yield [872], Complex copper hydrides prepared in situ from lithium aluminum hydride and cuprous iodide in tetrahydrofuran at 0° [873], or from lithium trimethoxyaluminum hydride or sodium bis(methoxy-ethoxy)aluminum hydride and cuprous bromide [874] in tetrahydrofuran at 0° reduced the a,p double bonds selectively in yields from 40 to 100%. Similar selectivity was found with a complex sodium bis(iron tetracarbonyl)hydride NaHFe2(CO)g [875]. 

Since sodium borohydride usually does not reduce the nitrile function it may be used for selective reductions of conjugated double bonds in oc,/l-un-saturated nitriles in fair to good yields [7069,1070]. In addition some special reagents were found effective for reducing carbon-carbon double bonds preferentially copper hydride prepared from cuprous bromide and sodium bis(2-methoxyethoxy)aluminum hydride [7766], magnesium in methanol [7767], zinc and zinc chloride in ethanol or isopropyl alcohol [7765], and triethylam-monium formate in dimethyl formamide [317]. Lithium aluminum hydride reduced 1-cyanocyclohexene at —15° to cyclohexanecarboxaldehyde and under normal conditions to aminomethylcyclohexane, both in 60% yields [777]. 

Cuprous bromide/dimethyl sulfide Copper, bromo[th1obis[methane]]- (9) (54678-23-8)... 

Method 3-4 is an improvement over the method of making bromopropadiene by shaking 3-bromopropyne for 6 days with cuprous bromide, concentrated hydrochloric acid, ammonium bromide, and copper bronze to afford a 28 % yield of bromopropadiene. 

These zinc reagents also exhibit excellent thermal stability but still react with strong electrophiles [275-277]. With less reactive electrophiles, addition of catalytic cuprous bromide can improve the reaction with dialkoxyphosphiny-difluoromethyl zinc reagents [278, 279]. Presumably, this reaction involves a dialkoxyphosphinydifluoromethyl copper reagent intermediate (Scheme 95). 

Cuprous Bromide.—100 gms. of crystallised copper sulphate, 288 gms. potassium bromide, 640 c.cs. of water, 160 gms. of copper turnings, and 88 gms. of cone, sulphuric acid are boiled until the whole is decolorised. The solution is decanted from unchanged copper. 

O-, m-, and p-Tolyt Copper. CH3.C6Hs.Cu, C7H7Cu mw 154.69 the o- and p-isomers are pale beige microcryst powds, while the p-isomer is a yel microcryst powd mp, all isomers expld strongly on exposure to 02 at 0°, and expld weakly on heating above 100° in a vac. Sol in most org solvents. Prepn is by dropwise addn of an ethereal soln of o-, m-, or p-tolyllithium to an ethereal soln of cuprous bromide at 0°. Yields o- is 50%, m- is 60—70%, and p- is 90%... 

A 5-I. round-bottom flask containing the hydrobromic acid-cuprous bromide solution, is arranged for steam distillation. After the copper solution is heated to boiling, the diazonium solution is gradually added from a separatory funnel and a vigorous current of steam is passed through the reaction mixture at the same time. This procedure requires about two hours. 

A more milder procedure is, where sodium methoxyalkenyldialkylborates obtained by the simple treatment of alkenyldialkylboranes with sodium methoxide, react readily with cuprous bromide-methylsulfide at 0 °C to afford symmetrical conjugated dienes (Eq. 87) 144). Although the intermediacy of a copper(I) borate complex formed... 

Replacement of the Diazonium Group by Chloride, Bromide, and Cyanide The Sandmeyer Reaction Copper salts (cuprous salts) have a special affinity for diazonium salts. Cuprous chloride, cuprous bromide, and cuprous cyanide react with arenediazonium salts to give aryl chlorides, aryl bromides, and aryl cyanides. The use of cuprous salts to replace arenediazonium groups is called the Sandmeyer reaction. The Sandmeyer reaction (using cuprous cyanide) is also an excellent method for attaching another carbon substituent to an aromatic ring. 

Cuprous bromide is insoluble in water. Its solutions in hydrochloric acid, hydrobromic add, and ammonium hydroxide readily absorb carbon monoxide. The maximum absorption for the ammoni-acal solution corresponds with one molecule of carbon monoxide to each atom of copper.15 When prepared in absence of air, the solution in ammonium hydroxide is colourless, but on contact with oxygen it develops a blue colour. The liquid obtained by dissolving cuprous bromide in an aqueous solution of sodium chloride or of sodium thiosulphate does not absorb carbon monoxide. 

Cuprous iodide, Cul.—The preparation of cuprous iodide can be effected by methods analogous to those adopted for cuprous bromide. Among them are the interaction of finely divided copper and either iodine 3 or concentrated hydriodic acid 4 under the influence of heat. 

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