Copper(II) acetate

Copper(II) acetate

Small crystals of copper(II) acetate

Copper(II) acetate crystals on copper wire
Names
IUPAC name
Tetra-μ2-acetatodiaquadicopper(II)
Other names
Copper(II) ethanoate
Cupric acetate
Copper Acetate
Verdigris
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.005.049
UNII
Properties
Cu(CH3COO)2
Molar mass 181.63 g/mol (anhydrous)
199.65 g/mol (hydrate)
Appearance Dark green crystalline solid
Odor odorless (hydrate)
Density 1.882 g/cm3 (hydrate)
Melting point Undetermined [1]
Boiling point 240 °C (464 °F; 513 K)
hydrate:
7.2 g/100 mL (cold water)
20 g/100 mL (hot water)
Solubility Soluble in alcohol
Slightly soluble in ether and glycerol
1.545 (hydrate)
Structure
Monoclinic
Hazards
Safety data sheet Baker MSDS
R-phrases (outdated) 22-36/37/38-50/53
S-phrases (outdated) 26-60-61
NFPA 704
Flammability code 0: Will not burn. E.g., waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
0
2
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
710mg/kg oral rat [2]
US health exposure limits (NIOSH):
PEL (Permissible)
 TWA 1 mg/m3 (as Cu)[3]
REL (Recommended)
 TWA 1 mg/m3 (as Cu)[3]
IDLH (Immediate danger)
 TWA 100 mg/m3 (as Cu)[3]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Copper(II) acetate, also referred to as cupric acetate, is the chemical compound with the formula Cu(OAc)2 where AcO− is acetate (CH
3CO−
2). The hydrated derivative, which contains one molecule of water for each Cu atom, is available commercially. Anhydrous Cu(OAc)2 is a dark green crystalline solid, whereas Cu2(OAc)4(H2O)2 is more bluish-green. Since ancient times, copper acetates of some form have been used as fungicides and green pigments. Today, copper acetates are used as reagents for the synthesis of various inorganic and organic compounds.[4] Copper acetate, like all copper compounds, emits a blue-green glow in a flame. The mineral hoganite is a naturally occurring form of copper(II) acetate.

Structure

The dinuclear structure of dimeric copper(II) acetate hydrate

Copper acetate hydrate adopts the paddle wheel structure seen also for related Rh(II) and Cr(II) tetraacetates.[5][6] One oxygen atom on each acetate is bound to one copper at 1.97 Å (197 pm). Completing the coordination sphere are two water ligands, with Cu–O distances of 2.20 Å (220 pm). The two five-coordinate copper atoms are separated by only 2.62 Å (262 pm), which is close to the Cu–Cu separation in metallic copper.[7] The two copper centers interact resulting in a diminishing of the magnetic moment such that near 90 K, Cu2(OAc)4(H2O)2 is essentially diamagnetic due to cancellation of the two opposing spins. Cu2(OAc)4(H2O)2 was a critical step in the development of modern theories for antiferromagnetic coupling.[8]

Synthesis

Copper(II) acetate is prepared industrially by heating copper(II) hydroxide or copper(II) carbonate with acetic acid.[4]

Heating a mixture of anhydrous copper(II) acetate and copper metal affords copper(I) acetate:[9][10]

Cu + Cu(OAc)2 → 2 CuOAc

Unlike the copper(II) derivative, copper(I) acetate is colourless and diamagnetic.

"Basic copper acetate" is prepared by neutralizing an aqueous solution of copper(II) acetate. The basic acetate is poorly soluble. This material is a component of verdigris, the blue-green substance that forms on copper during long exposures to atmosphere.

Uses in chemical synthesis

Copper(II) acetate has found some use as an oxidizing agent in organic syntheses. In the Eglinton reaction Cu2(OAc)4 is used to couple terminal alkynes to give a 1,3-diyne:[11][12]

Cu2(OAc)4 + 2 RC≡CH → 2 CuOAc + RC≡C−C≡CR + 2 HOAc

The reaction proceeds via the intermediacy of copper(I) acetylides, which are then oxidized by the copper(II) acetate, releasing the acetylide radical. A related reaction involving copper acetylides is the synthesis of ynamines, terminal alkynes with amine groups using Cu2(OAc)4.[13] It has been used for hydroamination of acrylonitrile.[14]

It is also an oxidising agent in Barfoed's test.

It combines with arsenic trioxide to form copper acetoarsenite, a powerful insecticide and fungicide called Paris Green or Schweinfurt Green.

References

  1. ↑ Trimble, R. F. "Copper(II) acetate monohydrate - An erroneous melting point". Journal of Chemical Education. 53: 397. doi:10.1021/ed053p397.
  2. ↑ "Archived copy" (PDF). Archived from the original (PDF) on 2011-09-28. Retrieved 2011-06-14.
  3. 1 2 3 "NIOSH Pocket Guide to Chemical Hazards #0150". National Institute for Occupational Safety and Health (NIOSH).
  4. 1 2 Richardson, H. Wayne, "Copper Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH
  5. ↑ Van Niekerk, J. N.; Schoening, F. R. L. (1953). "X-Ray Evidence for Metal-to-Metal Bonds in Cupric and Chromous Acetate". Nature. 171 (4340): 36–37. doi:10.1038/171036a0.
  6. ↑ Wells, A. F. (1984). Structural Inorganic Chemistry. Oxford: Clarendon Press.
  7. ↑ Catterick, J.; Thornton, P. (1977). "Structures and physical properties of polynuclear carboxylates". Adv. Inorg. Chem. Radiochem. 20: 291–362. doi:10.1016/s0065-2792(08)60041-2.
  8. ↑ Carlin, R. L. (1986). Magnetochemistry. Berlin: Springer.
  9. ↑ Kirchner, S. J.; Fernando, Q. (1980). "Copper(I) Acetate". Inorg. Synth. 20: 53–55. doi:10.1002/9780470132517.ch16.
  10. ↑ Parish, E. J.; Kizito, S. A. (2001). "Copper(I) Acetate". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.rc193.
  11. ↑ Stöckel, K.; Sondheimer, F. "[18]Annulene". Organic Syntheses. 54: 1. doi:10.15227/orgsyn.054.0001. ; Collective Volume, 6, p. 68
  12. ↑ Campbell, I. D.; Eglinton, G. "Diphenyldiacetylene". Organic Syntheses. 45: 39. doi:10.15227/orgsyn.045.0039. ; Collective Volume, 5, p. 517
  13. ↑ Vogel, P.; Srogl, J. (2005). "Copper(II) Acetate". EROS Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.rc194.pub2. ISBN 978-0-470-84289-8. .
  14. ↑ Heininger, S. A. "3-(o-Chloroanilino)propionitrile". Organic Syntheses. 38: 14. doi:10.15227/orgsyn.038.0014. ; Collective Volume, 4, p. 146
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