Cuprous acetylide

Simple cuprous acetylide was first prepared by Quetem in 1858. The preparation was based on introduction of the gases (contained acetylene) produced by passing electric sparks through liquid alcohol into a solution of cuprous chloride in aqueous ammonia [7, 8]. 

Cuprous acetylide is a red to brown-red amorphous substance. Its specific color is determined by the conditions of preparation. The substance prepared by the normal precipitation of cuprous salts by acetylene forms as a monohydrate [43]. It is interesting to note in older literature that the molecular formula of cuprous acetylide monohydrate is often written in a rather unusual form, for example C2H2CU2O [44]. The water of crystallization is firmly bonded and may not be removed even at 140 °C above phosphorous oxide [43]. Older literature contains procedures for preparation of the anhydrous salt by drying the monohydrate above sulfuric acid [7]. 

Cuprous acetylide is not soluble in water, but quite well soluble in bases [2]. In an oxygen environment it undergoes slow decomposition, according to Klement and Koddermann-Gros [43]  

Cuprous acetylide darkens when it is stored in the open. The change of color is accompanied by a significant increase in its sensitivity to mechanical stimuli. It is believed that both these phenomena are caused by oxidation of cuprous acetylide to cupric acetylide by oxygen in the atmosphere [45]. 

Potassium cyanide decomposes cuprous acetylide and an equivalent amount of acetylene is produced [46]  

Structure and reactivity Cu C C Cu, copper salt of weakly acidic acetylene, strong nucleophile 

Cuprous acetylide is used as a diagnostic test to identify the =CH unit to purify acetylene in the preparation of pure copper powder and as a catalyst in the mannfacture of 2-propyn-l-ol and acrylonitrile. 

Red amorphous powder explodes on heating insoluble in water, soluble in acid. 

There are no toxicity data in the published literature on cuprous acetylide. As with many copper salts, inhalation of its dust can cause irritation of the respiratory tract and ulceration of nasal septum. 

Cuprous acetylide in the dry state is highly sensitive to shock, causing explosion on impact. It explodes in contact with acetylene after being warmed in air or oxygen for several hours (Mellor 1946). It forms a highly explosive mixture containing silver acetylide when mixed with silver nitrate. It ignites spontaneously with chlorine, bromine, and 

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Metallic Derivatives, (a) Cuprous Acetylide. CujCg. Prepare an ammoniacal solution of cuprous chloride by first adding dilute ammonia to 2-3 ml. of dilute copper sulphate solution until the initial precipitate just redissolves and a clear deep-blue solution is obtained now add an aqueous solution of hydroxylamine hydrochloride drop by drop with shaking until the solution becomes first green and then completely colourless, the cupric salt being thus reduced to the cuprous derivative. 

Now add this solution to ajar of acetylene as before and shake vigorously. A chocolate-red precipitate of cuprous acetylide is at once formed. 

The only reaction which calls for comment here is the formation of red cuprous acetylide with an ammoniacal solution of cuprous chloride ... 

Cuprophan Cuprophan fibers Cuproproteinate Cuprossil Cuprous acetylides... 

Organometallic complexes of copper, nickel, and palladium have been used in indole syntheses from arenes. Most of the reactions proceed under relatively mild conditions and in some cases give rise to formation of the less common 2-substituted compounds.68 Good yields of such 2-substituted derivatives are formed in reactions of o-iodoarylamines with cuprous acetylides in dimethylformamide (Scheme 41 ).69 The efficiency of this type of... 

The heavy metal salts of acetylene have the properties of primary explosives, but only cuprous acetylide was found to be satisfactory for practical use. 

Cuprous acetylide was prepared by Berthelot [102] as early as 1866 by the action of acetylene on an ammonia solution of cuprous chloride. Cuprous acetylide takes the form of a russet or reddish-brown powder, insoluble in water and in the majority of organic solvents. 

Much research was necessary in order to establish the chemical composition of cuprous acetylide. Blochmann [103] and Scheiber and Reckleben [104] showed that the freshly precipitated and dried product has the approximate composition Cu2C2 H20. According to Keiser [105] drying this salt over sulphuric acid or calcium chloride (Scheiber and Reckleben [104]) gives an anhydrous product. 

Kiispert [106] drew attention to the fact that cuprous acetylide may form a colloidal solution. The colloidal state is favoured by the use of diluted ammonia solutions of cuprous salts. 

The substance is stable at ordinary temperatures and up to 100°C. Like cupric acetylide it decomposes on being heated in hydrochloric acid (Berthelot [102], Sabaneyev [107]). A solution of potassium cyanide also causes decomposition with the loss of acetylene. Makowka [108] showed that aldehyde-like compounds are formed from cuprous acetylide on reaction with a 30% solution of hydrogen peroxide. 

Cuprous acetylide explodes in air at 120-123°C, but in an acetylene atmosphere, under a pressure of 5 atm it decomposes without explosion at 250°C. According to Morgan [109] it is very easily exploded by an electric spark. 

Apart from cuprous acetylide, with the formula Cu2C2, there are complex cuprous salts prepared by the action of acetylene on certain cuprous salts in a neutral or slightly acidic medium e.g. Bhaduri [110] obtained a cuprous acetylide containing a thiosulphate group by the action of acetylene on cuprous thiosulphate, and in the presence of potassium iodide Scheiber and Reckleben [104] precipitated an acetylide containing iodine. 

Care should be taken that cuprous acetylide is not contaminated with cupric acetylide which may occur if the cuprous chloride used for the reaction contains cupric salt. This is of importance since cupric acetylide is unstable and explodes on heating even between 50 and 70°C. It is also more sensitive to impact and friction than cuprous acetylide. The pure cupric acetylide is black or brown. 

Many authors recommend the precipitation of cuprous acetylide in the presence of reducing substances such as hydroxylamine (Ilosvay [111]), S02 (Rupe[112]), hydrazine sulphate (Cattelain [113]), so as to avoid contamination with cupric acetylide. 

The precipitation of cuprous acetylide was introduced into analytical chemistry for the quantitative determination of copper. Since cupric acetylide was dangerous to handle, Makowka [108] worked out a method in which cupric salts are previously reduced, e.g. with hydroxylamine, to cuprous salts, when the acetylide is precipitated. Cuprous salts in a solution of hydroxylamine are employed as reagents for acetylene (e. g. Pietsch and Kotowski [114]). 

Cuprous acetylide is used as the chief component of match heads in electric fuses, being particularly susceptible to ignition by sparks or a glowing wire to give a sharp, hot flame. 

Silver acetylide, Ag2C2, is a white powder formed when acetylene is passed through an ammoniacal solution of silver chloride. It has even stronger explosive properties than cuprous acetylide due to its exceptionally large negative heat of formation —87.15 kcal/mole). Its ignition temperature is 200°C. It is of... 

C6HBC C.C C.C C.C C.C6H5 mw 250.28, yel ndls, mp li5—16°(browning), stable at RT for 13 months in the dark when placed on a hot metallic place it. decompd explosively with much soot. It shows no color reaction with sulfuric acid is more sol than tolan Sc (C6H.5C C)3 in polar solvs such as MeOH, ale Sc acetone. It was prepd by oxidative coupling of cuprous acetylide, C6HB.C C.C C.Cu, with CuCl2 (Refs)... 

The discovery of acetylene in 1836(or 1837) is attributed to Edmond Davy, but it was not until I860 that Berthelot definitely identified and named it(Ref 9, p 101 Ref 16, p 469). The compd obtained by Berthelot from cuprous acetylide was not pure because it contained some vinyl chloride. Acetylene was not produced commercially until Ca carbide was produced in the lab in 1899 by Morehead Willson, by heating a mixt of lime and coke in an electric furnace. They expected to prepare metallic calcium... 

Only one of the acetylides(cuprous acetylide) has found application in industry as an ingredient of electric detonators. Some acetylides, as for instance, that of silver, arc probably suitable for use in primers and detonators. They also may be incorporated in LA-based compositions for expl rivets in order to reduce their ignition point(Ref 6) According to Sax(Ref 6) the toxicity of acetylides is unknown, but their expln hazards are considered to be the same as those of fulminates and azides. The acetylides must be handled with extreme care and In storage they must be kept cool and wet. Metal powders, such as finely divided Cu or Ag, should be excluded. Shipping regulations are the same as for other primary and initiating explosives Refs l)Beil 1,238-40,(104 6),[217-20] ... 

Morita (Ref 11) prepd cuprous acetylide from a 5% soln of CuCl, and claimed that its ignition temp was 260 70°. This temp was lowered to 100° after the acetylide was oxidized by air. At the same time the color changed to black and the compd became very sensitive to impact. On further oxidn the ign temp rose to 200° It is presumed that oxidn transformed cuprous acetylide into the cupric compd. Schlubach Wolf (Ref 9b) in attempting to prep CuC- CH by creating a satd soln of CaH, in w at 0° with an aq soln of CuSO, + NH4OH + NO. NH2. HC1 obtained instead the CuaCj... 

Cuprous acetylide forms,whenever acetylene gas comes in contact with copper, its alloys or some of its salts. As the illuminating gas, made by distn of coal usually contains some acetylene, it should not be conducted through pipes contg Cu. If such pipes are used, great care and caution should be observed in cleaning the pipes inside (Ref 2)... 

Cuprous acetylide is the only acetylide which found application in the expl industry. 

Cuprous acetylide has been used also for prepn of industrial catalysts (See Cuprous Acetylide Catalyst, which follows) Refs l)Beil 1,240( 104),[2171 l910l... 

Cuprous Acetylide-Chloride, CjCuj+CuCl+HjO, dk violet pdr, deflagrates very weakly on heating in an open flame. Was prepd by passing acetylene through CuCl in 0.2N HCl Refs I)Beil 1,(104) 2)W.Manchot J.C. 

Note Some other cuprous acetylide-chloride comp ds (none of them seem to be expl) were described in Beil IJ910I and in the following Scandinavian papers ... 

Phenols or other hydroxylated (or potential hydroxylated) compounds Cuprous acetylide (R2) Benzofurans (222) Yield (7.) Refer- ences... 

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