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Copper(II) acetate

Chemical compound From Wikipedia, the free encyclopedia

Copper(II) acetate

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, Cu2(OAc)4(H2O)2, which contains one molecule of water for each copper atom, is available commercially. Anhydrous copper(II) acetate 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.[5] Copper acetate, like all copper compounds, emits a blue-green glow in a flame.

Quick Facts Names, Identifiers ...
Copper(II) acetate
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Small crystals of copper(II) acetate
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Copper(II) acetate hydrate
Copper(II) acetate monohydrate
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
EC Number
  • 205-553-3
UNII
UN number 3077
  • InChI=1S/2C2H4O2.Cu/c2*1-2(3)4;/h2*1H3,(H,3,4);/q;;+2/p-2 Y
    Key: OPQARKPSCNTWTJ-UHFFFAOYSA-L Y
  • InChI=1/2C2H4O2.Cu/c2*1-2(3)4;/h2*1H3,(H,3,4);/q;;+2/p-2
    Key: OPQARKPSCNTWTJ-NUQVWONBAO
  • [O+]1C(C)O[Cu-3]23([OH2+])[O+]C(C)O[Cu-3]1([OH2+])(OC(C)[O+]2)OC(C)[O+]3
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 115 °C (anhydrous) [1]

Undetermined (hydrate)[2]

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
GHS labelling:
GHS05: CorrosiveGHS06: ToxicGHS07: Exclamation markGHS09: Environmental hazard
Danger
H301, H302, H311, H314, H410, H411, H412
P260, P264, P270, P273, P280, P301+P310, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P322, P330, P361, P363, P391, P405, P501
NFPA 704 (fire diamond)
ThumbHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
710 mg/kg oral rat[3]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 1 mg/m3 (as Cu)[4]
REL (Recommended)
 TWA 1 mg/m3 (as Cu)[4]
IDLH (Immediate danger)
 TWA 100 mg/m3 (as Cu)[4]
Safety data sheet (SDS) Baker MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
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Structure

Copper acetate hydrate adopts the paddle wheel structure seen also for related Rh(II) and Cr(II) tetraacetates.[6][7] One oxygen atom on each acetate is bound to one copper atom 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 copper atoms are separated by only 2.62 Å (262 pm), which is close to the Cu–Cu separation in metallic copper.[8][9][10][11] The two copper centers interact resulting in a diminishing of the magnetic moment such that at temperatures below 90 K, Cu2(OAc)4(H2O)2 is essentially diamagnetic. Cu2(OAc)4(H2O)2 was a critical step in the development of modern theories for antiferromagnetic exchange coupling, which ascribe its low-temperature diamagnetic behavior to cancellation of the two opposing spins on the adjacent copper atoms.[12]

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    Copper(II) acetate monohydrate

Synthesis

Copper(II) acetate is prepared industrially by heating copper(II) hydroxide or basic copper(II) carbonate with acetic acid.[5]

Uses in chemical synthesis

Summarize
Perspective

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:[13][14]

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.[15] It has been used for hydroamination of acrylonitrile.[16]

In chemical analysis, it serves as an oxidizing agent in both the Barfoed's test for presence of monosaccharides and as a precursor to a copper-fatty acid complex in the colorimetric copper soap assay to test for free fatty acids[17].

It reacts with arsenic trioxide to form copper acetoarsenite, a powerful insecticide and fungicide called Paris green.

Heating a mixture of anhydrous copper(II) acetate and copper metal affords copper(I) acetate:[18][19]

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.


Other uses

A mixture of copper acetate and ammonium chloride is used to chemically color copper with a bronze patina.[20]

Mineralogy

The mineral hoganite is a naturally occurring form of copper(II) acetate.[21][22] A related mineral, also containing calcium, is paceite.[22] Both are very rare.[23][24]

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    Copper(II) acetate, crystalline
  • Thumb
    Copper(II) acetate, milled

References

External links

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