Copper(II) hydroxide

Copper(II) hydroxide
IUPAC name Copper(II) hydroxide
Other names Cupric hydroxide
Identifiers
CAS number	20427-59-2 Y
PubChem	164826
ChemSpider	144498 Y
KEGG	C18712 Y
Jmol-3D images	Image 1
SMILES [Cu+2].[OH-].[OH-]
InChI InChI=1S/Cu.2H2O/h;2*1H2/q+2;;/p-2 Y Key: JJLJMEJHUUYSSY-UHFFFAOYSA-L Y InChI=1/Cu.2H2O/h;2*1H2/q+2;;/p-2 Key: JJLJMEJHUUYSSY-NUQVWONBAH
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 (decomp into CuO)
Solubility in water	negligible
Solubility product, Ksp	2.20 x 10-20[1]
Solubility	insoluble in ethanol; soluble in NH4OH, KCN
Hazards
MSDS	http://www.sciencelab.com/xMSDS-Cupric_Hydroxide-9923594
EU Index	Not listed
Main hazards	Skin, Eye, & Respiratory Irritant
NFPA 704	0 2 0
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
Y hydroxide (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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 color.

History

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

Copper(II) hydroxide is found in several different copper minerals, most 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

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 bicarbonate). 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

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 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.

Since copper(II) hydroxide is mildly amphoteric, it dissolves slightly in concentrated alkali, forming [Cu(OH)₄]^2-.^[9]

Reagent for organic chemistry

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:^{[citation needed]}

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:^{[citation needed]}

Uses

Copper(II) hydroxide has been used as an alternative to the Bordeaux mixture, a fungicide and nematicide.^[10] 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.^[11] It is now sold as Microkote either in a solution you apply yourself, or as treated pots.

References

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

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. ^ Pauling, Linus (1970). General Chemistry. Dover Publications, Inc. (p 702).
10. ^ Bordeaux Mixture. UC IPM online. 2007.
11. ^ "SePRO Corporation".

External links

• National Pollutant Inventory - Copper and compounds fact sheet
• Safety Data