 | |
| Names | |
|---|---|
| IUPAC name Dicuprous acetylide | |
Other names
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| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| Properties | |
| Cu2C2 | |
| Molar mass | 151.114 g·mol−1 |
| Appearance | red-brown powder |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | explosive |
| NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 1 mg/m3 (as Cu)[1] |
REL (Recommended) | TWA 1 mg/m3 (as Cu)[1] |
IDLH (Immediate danger) | TWA 100 mg/m3 (as Cu)[1] |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Copper(I) acetylide,copper carbide orcuprous acetylide, is claimed to be achemical compound with the formulaCu2C2. It is proposed to consists ofCu+cations andacetylideanions−C≡C−, with thetriple bond between the twocarbon atoms. Although never characterized byX-ray crystallography, the material has been claimed at least since 1856.[2] One form is claimed to be amonohydrate with formulaCu2C2·H2O. It is a reddish-brownexplosive powder.
Materials purported to be copper acetylide can be prepared by treatingacetylene with a solution ofcopper(I) chloride andammonia:
This reaction produces a reddish solidprecipitate.
When dry, "copper acetylide" is a heat and shock sensitiveprimary explosive, more sensitive thansilver acetylide.[3]
In acetylene manufacturing plants, copper acetylide is thought to form inside pipes made ofcopper or an alloy with high copper content, which may result in violent explosion.[4] This led to abandonment of copper as a construction material in such facilities.[5] Coppercatalysts used in thechemical industry can also possess a degree of risk under certain conditions.[6]
"Copper(I) acetylide" is claimed to be a precursor topolyynes. Treatment ofCu2C2·H2O withammonia in air leaves a black solid residue, claimed to becarbyne, an elusiveallotrope of carbon:[7]
This interpretation has been disputed.[8]
Freshly prepared "copper(I) acetylide" reacts withhydrochloric acid to form acetylene and copper(I) chloride.[citation needed] Samples that have been aged with exposure to air or to copper(II) ions liberate also higherpolyynesH(−C≡C−)nH, withn from 2 to 6, when decomposed byhydrochloric acid. A "carbonaceous" residue of this decomposition also has the spectral signature of(−C≡C−)n chains. It has been conjectured that oxidation causes polymerization of theacetylide anionsC2−2 in the solid intocarbyne-type anions.−C(≡C−C≡)nC− orcumulene-type anions2−C(=C=C=)nC2−.[2]
Thermal decomposition of "copper(I) acetylide" in vacuum is not explosive and leaves copper as a fine powder at the bottom of the flask, while depositing a fluffy very fine carbon powder on the walls. On the basis of spectral data, this powder was claimed to becarbyne(−C≡C−)n rather thangraphite as expected.[2]
Though not practically useful as an explosive due to high sensitivity, it is interesting as a curiosity because it is one of the very few explosives that do not liberate any gaseous products upon detonation.
The formation of copper(I) acetylide when a gas is passed through a solution ofcopper(I) chloride is used as a test for the presence ofacetylene.
Reactions betweenCu+ andalkynes occur only if a terminalhydrogen is present (as it is slightlyacidic in nature). Thus, this reaction is used for identification of terminal alkynes.
Although Cu2C2 remains weakly characterized, complexes with aCu−C≡C−Cu linkage are known.[9]
