Copper, bronze, activated

Continuous steam distillation, 147, 148 Cooling baths, 61 Cooling curve method, 26 Copper bronze, activated, 193 Copper - chromium oxide catalyst, for aldehyde synthesis, 318, 321 for hydrogenation, 872, 873 hydrogenolysis with, 872J Copper phthalocyanine, 983 Copper powder, 192 Copper sulphate, as desiccant, 40, 41 Cork stoppers, 55 boring of, 56... 

Activated copper bronze. Commercial copper bronze does not always give satisfactory yields in the Ullmann reaction, but uniform results can... 

Place 50 g. of o-chloronitrobenzene and 75 g. of clean dry sand in a 250 ml. flask equipped with a mechanical stirrer. Heat the mixture in an oil or fusible metal bath to 215-225° and add, during 40 minutes, 50 g. of copper bronze or, better, of activated copper bronze (Section 11,50, 4) (1), Maintain the temperature at 215-225° for a further 90 minutes and stir continuously. Pour the hot mixture into a Pyrex beaker containing 125 g. of sand and stir until small lumps are formed if the reaction mixture is allowed to cool in the flask, it will set to a hard mass, which can only be removed by breaking the flask. Break up the small lumps by powdering in a mortar, and boil them for 10 minutes with two 400 ml. 

The experimental conditions for conducting the above reaction in the presence of dimethylformamide as a solvent are as follows. In a 250 ml. three-necked flask, equipped with a reflux condenser and a tantalum wire Hershberg-type stirrer, place 20 g. of o-chloronitrobenzene and 100 ml. of diinethylform-amide (dried over anhydrous calcium sulphate). Heat the solution to reflux and add 20 g. of activated copper bronze in one portion. Heat under reflux for 4 hours, add another 20 g. portion of copper powder, and continue refluxing for a second 4-hour period. Allow to cool, pour the reaction mixture into 2 litres of water, and filter with suction. Extract the solids with three 200 ml. portions of boiling ethanol alternatively, use 300 ml. of ethanol in a Soxhlet apparatus. Isolate the 2 2- dinitrodiphenyl from the alcoholic extracts as described above the 3ueld of product, m.p. 124-125°, is 11 - 5 g. 

For example, consider the bi-metallic alloy known as bronze, which contains tin (30 mol%) and copper (70 mol%). There are two activities in this alloy system, one each for tin and copper. The activity of each metal is obtained as its respective mole fraction x,... 

In a related system, Feringa and co-workers (104) noted the beneficial effect of copper bronze in the allylic oxidation reaction. The addition of 5 mol% of this addend provides the cyclohexenyl ester in higher selectivity and yield than in the absence of the metal, while allowing the reaction to proceed at 0°C. The role of copper bronze is presumably to effect reduction of Cu(II) to the catalytically active... 

Elemental sulfur is sometimes termed active sulfur because of its highly aggressive and corrosive nature toward metal, especially copper, bronze, and brass. Copper sulfide readily forms when in contact with elemental sulfur. 

A vigorous Claisen condensation ensues when a homophthalic ester and methyl formate are treated with sodium ethoxide and the active methylene group is formylated. Cyclization takes place with ease in acidic media to produce a methyl isocoumarin-4-carboxylate (50JCS3375). Hydrolysis under acid conditions is sometimes accompanied by polymerization, but the use of boron trifluoride in acetic acid overcomes this problem. Decarboxylation may be effected in the conventional manner with copper bronze, though it sometimes accompanies the hydrolysis. 

Activated copper bronze is essential for satisfactory yields in the Ullmann reaction, and uniform results can be obtained by the following activation process. One hundred grams of copper bronze are treated with 1 litre of a 2 per cent solution of iodine in acetone for 5-10 minutes. This results in the production of a rather greyish colour due to the formation of copper iodide. The product is filtered off on a Buchner funnel, removed and washed by stirring with 500 ml of 1 1 solution of concentrated hydrochloric acid in acetone. The copper iodide dissolves, and the residual copper bronze is filtered and washed with acetone. It is then dried in a vacuum desiccator. The activated copper bronze should be used immediately after preparation. 

A reaction which is reminiscent of the Wurtz coupling procedure, and which is particularly valuable in the syntheiss of biphenyl and its symmetrically substituted derivatives, is that of Ullmann. It involves heating an aryl halide with copper powder, or better, with activated copper bronze. 

The photostimulated reaction of o-bromoiodobenzene with CH2COPh ions gives mo nosubstitution product 2 in 88% yield, which cyclizes to 2-phenylbenzofuran under catalysis by Cu (activated copper bronze) (Scheme 10.8) [19]. 

C4)4N]Br Copper bronze [(C4)4N][OAc] 130 °C. Coupling of aryliodides and activated bromides activity increases upon recycling due to formation of more active nanoparticles catalysts remains stable for more than 15 runs products extracted with cyclohexane. [84]... 

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