Cuprous cyanide
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| Names | |
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IUPAC name
Copper(I) cyanide
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| Other names
Cuprous cyanide, copper cyanide, cupricin
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| Identifiers | |
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3D model (Jmol)
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| ChemSpider | |
| ECHA InfoCard | 100.008.076 |
| EC Number | 208-883-6 |
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PubChem CID
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| RTECS number | GL7150000 |
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| Properties | |
| CuCN | |
| Molar mass | 89.563 g/mol |
| Appearance | off-white / pale yellow powder |
| Density | 2.92 g/cm3 |
| Melting point | 474 °C (885 °F; 747 K) |
| negligible | |
| Solubility | insoluble in ethanol, cold dilute acids; soluble in NH4OH, KCN |
| -24.0·10−6 cm3/mol | |
| Structure | |
| monoclinic | |
| Hazards | |
| Safety data sheet | Oxford MSDS |
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EU classification (DSD) (outdated)
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Very toxic (T+) Dangerous for the environment (N) |
| R-phrases (outdated) | R26/27/28, R32, R50/53 |
| S-phrases (outdated) | (S1/2), S7, S28, S29, S45, S60, S61 |
| NFPA 704 | |
| Flash point | Non-flammable |
| US health exposure limits (NIOSH): | |
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PEL (Permissible)
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TWA 1 mg/m3 (as Cu) |
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REL (Recommended)
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TWA 1 mg/m3 (as Cu) |
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IDLH (Immediate danger)
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TWA 100 mg/m3 (as Cu) |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |
Copper(I) cyanide is an inorganic compound with the formula CuCN. This off-white solid occurs in two polymorphs; impure samples can be green due to the presence of Cu(II) impurities. The compound is useful as a catalyst, in electroplating copper, and as a reagent in the preparation of nitriles.
Copper cyanide is a coordination polymer. It exists in two polymorphs both of which contain -[Cu-CN]- chains made from linear copper(I) centres linked by cyanide bridges. In the high-temperature polymorph, HT-CuCN, which is isostructural with AgCN, the linear chains pack on a hexagonal lattice and adjacent chains are off set by +/- 1/3 c, Figure 1. In the low-temperature polymorph, LT-CuCN, the chains deviate from linearity and pack into rippled layers which pack in an AB fashion with chains in adjacent layers rotated by 49 °, Figure 2.
Figure 1: The structure of HT-CuCN showing the chains running along the c axis. Key: copper = orange and cyan = head-to-tail disordered cyanide groups.
Figure 2: The structure of LT-CuCN showing sheets of chains stacking in an ABAB fashion. Key copper = orange and cyan = head-to-tail disordered cyanide groups.
LT-CuCN can be converted to HT-CuCN by heating to 563 K in an inert atmosphere. In both polymorphs the copper to carbon and copper to nitrogen bond lengths are ~1.85 Å and bridging cyanide groups show head-to-tail disorder.
Cuprous cyanide is commercially available and is supplied as the low-temperature polymorph. It can be prepared by the reduction of copper(II) sulfate with sodium bisulfite at 60 °C, followed by the addition of sodium cyanide to precipitate pure LT-CuCN as a pale yellow powder.
On addition of sodium bisulfite the copper sulfate solution turns from blue to green, at which point the sodium cyanide is added. The reaction is performed under mildly acidic conditions. Copper cyanide has historically been prepared by treating copper(II) sulfate with sodium cyanide, in this redox reaction, copper(I) cyanide forms together with cyanogen:
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