Acetylides cupric acetylide

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. 

The acetylide anion 3 is likely to form an alkynyl-copper complex by reaction with the cupric salt. By electron transfer the copper-II ion is reduced, while the acetylenic ligands dimerize to yield the -acetylene 2 ... 

Thus, all copper salts give an explosive reaction with calcium carbide. This is due to the formation of explosive copper acetylide, which is formed from cupric or cuprous cation and the acetylene formed. 

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. 

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]). 

Copper Acetylide (Kupfer-acetylenid, in Ger) exists in both cuprous, CUjCjjand cupric, CuCj, forms... 

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... 

Brameld et al(Ref 4) investigated the formation of copper acetylides from aq solus of various cupric salts and acetylene. The resulting compds appear to fall into two types a)black amors ppts and b)lustrous, metallic appearing plates... 

The type b) cupric acetylides expl on gentle tapping (sometimes even when touched under soln) with a bright flash and report Co form metallic Cu. This type includes acetylides from Cu borate in strongly alkaline soln and from Cu acetate in acidic and strongly ammoniacal solns Refs l)Beil 1,241 [217] 2)H.G.Soder-... 

Cupric Acetylide. See under ACETYLIDES AND CARBIDES, Vol 1, p A74-R and in this Volume under List of Copper Compounds,pC 516-L... 

The type a) expl sometimes with a report, spades and flashes to form black CuO. It could be fired by a drop of HNO,. The ex-plosibility of this type of acetylide is greater than thatof cuprous acetylide. This type includes most acetylides, formed from the more common cupric salts, such as die chloride, sulfate and nitrate, and those formed from copper org salts made alkaline with alkaliesother than ammonia, or also with ammonia, provided insufficient ammonia is present to retain all the Cu as a complex salt... 

Silver acetylides undergo oxidative condensation in the presence of cupric chloride to give diynes.124 Dimerization is a reaction common to a number of organosilver compounds, including both alkyl- and arylsilver derivatives. 

Cupric acetylide detonates on heating. However, if the symmetry of its surface film is increased by a partial oxidation of CuC2 into CuO, the compound decomposes on heating without detonation (23). 

Cupric carbide or acetylide.—There is some evidence of the direct combination of copper and carbon at high temperatures to form a carbide. The substance is endothermic, and dissociates rapidly in the neighbourhood of 1600° C., but less rapidly at lower temperatures.10 With ammoniacal solutions of cupric salts acetylene yields a flocculent, black precipitate of varying composition, but approximating to the formula CCu2. It explodes at 70° to 80° C.11... 

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