Copper(II) hydroxide

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Copper(II) hydroxide
Copper(II) hydroxide
Cupric hydroxide.JPG
Identifiers
CAS number 20427-59-2 YesY
PubChem 164826
ChemSpider 144498 YesY
KEGG C18712 YesY
Jmol-3D images Image 1
Properties
Molecular formula Cu(OH)2
Molar mass 97.561 g/mol
Appearance Blue or blue-green solid
Density 3.368 g/cm3, solid
Melting point 80 °C (176 °F; 353 K) (decomposes into CuO)
Solubility in water negligible
Solubility product, Ksp 2.20 x 10-20[1]
Solubility insoluble in ethanol;
soluble in NH4OH, KCN
Thermochemistry
Std molar
entropy
So298
108 J·mol−1·K−1
Std enthalpy of
formation
ΔfHo298
−450 kJ·mol−1
Hazards
MSDS http://www.sciencelab.com/xMSDS-Cupric_Hydroxide-9923594
EU Index Not listed
Main hazards Skin, Eye, & Respiratory Irritant
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
LD50 1000 mg/kg (oral, rat)
Related compounds
Other anions Copper(II) oxide
Copper(II) carbonate
Copper(II) sulfate
Copper(II) chloride
Other cations Nickel(II) hydroxide
Zinc hydroxide
Iron(II) hydroxide
Cobalt hydroxide
Related compounds Copper(I) oxide
Copper(I) chloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Copper(II) hydroxide is the hydroxide of the metal copper with the chemical formula of Cu(OH)2. Copper hydroxide is a pale blue, gelatinous solid. Some forms of copper(II) hydroxide are sold as "stabilized" copper hydroxide, quite likely a mixture of copper(II) carbonate and hydroxide. These are often greener in colour. Copper hydroxide acts as a weak base in aqueous solution.

History[edit]

Copper(II) hydroxide has been known since copper smelting began around 5000 BC although the alchemists were probably the first to manufacture it.[2] This was easily done by mixing solutions of lye (sodium or potassium hydroxide) and blue vitriol (copper(II) sulfate), both chemicals which were known in antiquity.

It was produced on an industrial scale during the 17th and 18th centuries for use in pigments such as blue verditer and Bremen green.[3] These pigments were used in ceramics and painting.[4]

Natural occurrence[edit]

Copper(II) hydroxide occurs naturally as a component of several copper minerals, notably azurite, malachite, antlerite, and brochantite. Azurite (2CuCO3·Cu(OH)2) and malachite (CuCO3·Cu(OH)2) are carbonates while antlerite (CuSO4·2Cu(OH)2) and brochantite (CuSO4·3Cu(OH)2) are sulfates. Copper(II) hydroxide is rarely found as an uncombined mineral because it slowly reacts with carbon dioxide from the atmosphere to form a basic copper(II) carbonate. The mineral of the formula Cu(OH)2 is called spertiniite.

Synthesis[edit]

Copper(II) hydroxide can be produced by adding a small amount of sodium hydroxide to a dilute solution of copper(II) sulfate (CuSO4 · 5H2O). The precipitate produced in this manner, however, often contains water molecules and an appreciable amount of sodium hydroxide impurity. A purer product can be attained if ammonium chloride is added to the solution beforehand. Nevertheless, it is impossible to obtain a pure product; processes for eliminating impurities lead to the destruction of the hydroxide, giving rise to the more stable oxide, CuO.[5] Alternatively, copper hydroxide is readily made by electrolysis of water (containing a little electrolyte such as sodium sulfate). A copper anode is used, often made from scrap copper.

"Copper in moist air slowly acquires a dull green coating. The green material is a 1:1 mole mixture of Cu(OH)2 and CuCO3."[6]

2 Cu (s) + H2O (g) + CO2 (g) + O2 (g) → Cu(OH)2 (s) + CuCO3 (s)

This is the patina that forms on bronze and other copper alloy statues such as the Statue of Liberty.

Reactions[edit]

Moist samples of copper(II) hydroxide slowly turn black due to the formation of copper(II) oxide.[7] When it is dry, however, copper(II) hydroxide does not decompose unless it is heated to 185 °C.[8]

Copper(II) hydroxide reacts with a solution of ammonia to form a deep blue solution Cupramine a chelated form - consisting of the [Cu(NH3)4]2+ complex ion. Copper(II) hydroxide in ammonia solution, known as Schweizer's reagent, possesses the interesting ability to dissolve cellulose. This property led to it being used in the production of rayon, a cellulose fiber. It is also used widely in the aquarium industry for its ability to destroy external parasites in fish, including flukes, marine ich, brook and marine velvet, without killing the fish. Although other water soluble copper compounds can be effective in this role, they generally result in high fish mortality. Cupramine is also widely used in organic chemical synthesis, discussed below.

Besides, when the concentration of ammonia solutions is very high, divalent copper ions in presence of dioxygen, catalyze ammonia oxidation, giving rise to copper ammine nitrites: Cu (NO2)2( NH3)n;[9][10]

Since copper(II) hydroxide is mildly amphoteric, it dissolves slightly in concentrated alkali, forming [Cu(OH)4]2-.[11]

Reagent for organic chemistry[edit]

Copper(II) hydroxide has a rather specialized role in organic synthesis. Often, when it is utilized for this purpose, it is prepared in situ by mixing a soluble copper(II) salt and potassium hydroxide.

It is sometimes used in the synthesis of aryl amines. For example, copper(II) hydroxide catalyzes the reaction of ethylenediamine with 1-bromoanthraquinone or 1-amino-4-bromoanthraquinone to form 1-((2-aminoethyl)amino)anthraquinone or 1-amino-4-((2-aminoethyl)amino)anthraquinone, respectively:[12]

UllmannCu(OH)2.PNG

Copper(II) hydroxide also converts acid hydrazides to carboxylic acids at room temperature. This is especially useful in synthesizing carboxylic acids with other fragile functional groups. The published yields are generally excellent as is the case with the production of benzoic acid and octanoic acid:[13]

Cu(OH)2 CarboxylicAcidCatalyst.PNG

Uses[edit]

Copper(II) hydroxide has been used as an alternative to the Bordeaux mixture, a fungicide and nematicide.[14] Such products include Dupont's Kocide 3000. Copper(II) hydroxide is also occasionally used as ceramic colorant.

Copper(II) hydroxide has been combined with latex paint, making a product designed to control root growth in potted plants. Secondary and lateral roots thrive and expand, resulting in a dense and healthy root system. It was sold under the name Spin Out, which was first introduced by Griffin L.L.C. The rights are now owned by SePRO Corp.[15] It is now sold as Microkote either in a solution you apply yourself, or as treated pots.

References[edit]

  1. Roscoe, H. E., & Schorlemmer, C. (1879). A Treatise on Chemistry 2nd Ed, Vol 2, Part 2. MacMillan & Co. (p 498).
  2. Paquette, Leo A. (1995). Encyclopedia of Reagents for Organic Synthesis, 8 Volume Set. Wiley. ISBN 0-471-93623-5.

Footnotes[edit]

  1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  2. ^ Richard Cowen, Essays on Geology, History, and People, Chapter 3: "Fire and Metals: Copper".
  3. ^ Tony Johansen, Historic Artist's Pigments. PaintMaking.com. 2006.
  4. ^ Blue verditer. Natural Pigments. 2007.
  5. ^ Y. Cudennec, A. Lecerf (2003). "The transformation of Cu(OH)2 into CuO, revisited". Solid State Sciences 5: 1471–1474. doi:10.1016/j.solidstatesciences.2003.09.009. 
  6. ^ Masterson, W. L., & Hurley, C. N. (2004). Chemistry: Principles and Reactions, 5th Ed. Thomson Learning, Inc. (p 331)"
  7. ^ Watts, Henry (1872). A Dictionary of Chemistry and the Allied Branches of Other Sciences, Vol 2. Longmans, Green, and Co. (p 69).
  8. ^ Copper (II) hydroxide. Ceramic Materials Database. 2003.
  9. ^ Y. Cudennec, et al. (1995). "Etude cinétique de l'oxydation de l'ammoniac en présence d'ions cuivriques". Comptes Rendus Académie Sciences Paris, série II,Méca; phys. chim. astron. 320(6): 309–316. 
  10. ^ Y. Cudennec, et al. (1993). "Synthesis and study of Cu(NO2)2(NH3)4 and Cu(NO2)2(NH3)2". European journal of solid state and inorganic chemistry. 30(1-2): 77–85. 
  11. ^ Pauling, Linus (1970). General Chemistry. Dover Publications, Inc. (p 702).
  12. ^ Tsuda, T., Copper(II) Hydroxide. In Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, Ltd: 2001.
  13. ^ Tsuda, T., Copper(II) Hydroxide. In Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, Ltd: 2001.
  14. ^ Bordeaux Mixture. UC IPM online. 2007.
  15. ^ "SePRO Corporation".

External links[edit]