Copper(II) hydroxide
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Copper(II) hydroxide is the
hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...
of
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
with the
chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbol ...
of Cu(OH)2. It is a pale greenish blue or bluish green solid. Some forms of copper(II) hydroxide are sold as "stabilized" copper(II) hydroxide, although they likely consist of a mixture of
copper(II) carbonate Copper(II) carbonate or cupric carbonate is a chemical compound with formula . At ambient temperatures, it is an ionic solid (a salt) consisting of copper(II) cations and carbonate anions . This compound is rarely encountered because it is di ...
and hydroxide. Cupric hydroxide is a strong base, although its low solubility in water makes this hard to observe directly.


Occurrence

Copper(II) hydroxide has been known since
copper smelting Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a ch ...
began around 5000 BC although the
alchemists Alchemy (from Arabic: ''al-kīmiyā''; from Ancient Greek: χυμεία, ''khumeía'') is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practiced in China, India, the Muslim world, ...
were probably the first to manufacture it by mixing solutions of
lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali which is highly soluble in water producing caustic basic solutions. "Lye" most commonly refers to sodium hydroxide (NaOH), but historically has been u ...
(sodium or potassium hydroxide) and
blue vitriol Copper(II) sulfate, also known as copper sulphate, is an inorganic compound with the chemical formula . It forms hydrates , where ''n'' can range from 1 to 7. The pentahydrate (''n'' = 5), a bright blue crystal, is the most commonly encountered h ...
(copper(II) sulfate). Sources of both compounds were available in antiquity. It was produced on an industrial scale during the 17th and 18th centuries for use in
pigments A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compoun ...
such as
blue verditer Basic copper carbonate is a chemical compound, more properly called copper(II) carbonate hydroxide. It is an ionic compound (a salt) consisting of the ions copper(II) , carbonate , and hydroxide . The name most commonly refers to the compound w ...
and Bremen green. These pigments were used in
ceramics A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
and
painting Painting is the practice of applying paint, pigment, color or other medium to a solid surface (called the "matrix" or "support"). The medium is commonly applied to the base with a brush, but other implements, such as knives, sponges, and ai ...
.


Mineral

The mineral of the formula Cu(OH)2 is called
spertiniite Spertiniite is a rare copper hydroxide mineral. Chemically it is copper(II) hydroxide with formula Cu(OH)2. It occurs as blue to blue green tabular orthorhombic crystal aggregates in a secondary alkaline environment altering chalcocite. Associa ...
. Copper(II) hydroxide is rarely found as an uncombined
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
because it slowly reacts with
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
from the atmosphere to form a
basic copper(II) carbonate Basic copper carbonate is a chemical compound, more properly called copper(II) carbonate hydroxide. It is an ionic compound (a salt) consisting of the ions copper(II) , carbonate , and hydroxide . The name most commonly refers to the compound w ...
. Thus copper slowly acquires a dull green coating in moist air by the reaction: :2 Cu(OH)2 + CO2 → Cu2CO3(OH)2 + H2O The green material is in principle a 1:1 mole mixture of Cu(OH)2 and CuCO3. This patina forms on bronze and other copper
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...
statues such as the Statue of Liberty.


Production

Copper(II) hydroxide can be produced by adding sodium hydroxide to a solution of a soluble copper(II) salt, such as
copper(II) sulfate Copper(II) sulfate, also known as copper sulphate, is an inorganic compound with the chemical formula . It forms hydrates , where ''n'' can range from 1 to 7. The pentahydrate (''n'' = 5), a bright blue crystal, is the most commonly encountered h ...
(CuSO4·5H2O):O. Glemser and H. Sauer "Copper(II) Hydroxide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 2. p. 1013. :2NaOH + CuSO4·5H2O → Cu(OH)2 + 6H2O + Na2SO4 The precipitate produced in this manner, however, often contains water and an appreciable amount of sodium-containing impurities. Furthermore, this form of copper hydroxide tends to convert to black
copper(II) oxide Copper(II) oxide or cupric oxide is an inorganic compound with the formula CuO. A black solid, it is one of the two stable oxides of copper, the other being Cu2O or copper(I) oxide (cuprous oxide). As a mineral, it is known as tenorite. It is ...
: : A purer product can be attained if ammonium chloride is added to the solution beforehand to generate ammonia in situ. Alternatively it can be produced in a two-step procedure from copper(II) sulfate via "basic copper sulfate:" : : Alternatively, copper hydroxide is readily made by
electrolysis of water Electrolysis of water, also known as electrochemical water splitting, is the process of using electricity to decompose water into oxygen and hydrogen gas by electrolysis. Hydrogen gas released in this way can be used as hydrogen fuel, or remi ...
(containing a little electrolyte such as sodium sulfate or
magnesium sulfate Magnesium sulfate or magnesium sulphate (in English-speaking countries other than the US) is a chemical compound, a salt with the formula , consisting of magnesium cations (20.19% by mass) and sulfate anions . It is a white crystalline solid, ...
) with a copper
anode An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic ...
: :Cu + 2OH → Cu(OH)2 + 2e


Structure

The structure of Cu(OH)2 has been determined by
X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...
The copper center is square pyramidal. Four Cu-O distances in the plane range are 1.96 Å, and the axial Cu-O distance is 2.36 Å. The hydroxide ligands in the plane are either doubly bridging or triply bridging.


Reactions

It is stable to about 100 °C. Copper(II) hydroxide reacts with a solution of
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
to form a deep blue solution of tetramminecopper u(NH3)4sup>2+
complex ion A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...
. Copper(II) hydroxide catalyzes the oxidation of ammonia solutions in presence of dioxygen, giving rise to copper ammine nitrites, such as Cu(NO2)2(NH3)n. Copper(II) hydroxide is mildly
amphoteric In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used. One type of amphoteric species are amphipro ...
. It dissolves slightly in concentrated alkali, forming u(OH)4sup>2−.


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 ''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...
by mixing a soluble copper(II) salt and
potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
. It is sometimes used in the synthesis of
aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromaticity, aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar ...
amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen Hydrogen is the chemical element wi ...
s. 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: : Copper(II) hydroxide also converts acid hydrazides to carboxylic acids at room temperature. This conversion is useful in the synthesis of carboxylic acids in the presence of other fragile
functional groups In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest ...
. The yields are generally excellent as is the case with the production of
benzoic acid Benzoic acid is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin, ...
and
octanoic acid Caprylic acid (), also known under the systematic name octanoic acid or C8 Acid, is a saturated fatty acid, medium-chain fatty acid (MCFA). It has the structural formula , and is a colorless oily liquid that is minimally soluble in water with a s ...
: :


Uses

Copper(II) hydroxide in ammonia solution, known as
Schweizer's reagent Schweizer's reagent is the metal ammine complex with the formula u(NH3)4(H2O)2OH)2. This deep-blue compound is used in purifying cellulose. It is prepared by precipitating copper(II) hydroxide from an aqueous solution of copper sulfate using so ...
, possesses the interesting ability to dissolve
cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...
. This property led to it being used in the production of rayon, a
cellulose fiber Cellulose fibers () are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants, or from other plant-based material. In addition to cellulose, the fibers may also contain hemicellulose and ...
. It is also used widely in the aquarium industry for its ability to destroy external parasites in fish, including flukes,
marine ich ''Cryptocaryon irritans'' is a species of ciliates that parasitizes marine fish, causing marine white spot disease or marine ich (pronounced ''ick''). It is one of the most common causes of disease in marine aquaria. Taxonomy ''Cryptocaryon i ...
, Brooklynellosis, 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. Copper(II) hydroxide has been used as an alternative to the
Bordeaux mixture Bordeaux mixture (also called ''Bordo Mix'') is a mixture of copper(II) sulphate (CuSO4) and quicklime ( Ca O) used as a fungicide. It is used in vineyards, fruit-farms and gardens to prevent infestations of downy mildew, powdery mildew and other ...
, a fungicide and
nematicide A nematicide is a type of chemical pesticide used to kill plant-parasitic nematodes. Nematicides have tended to be broad-spectrum toxicants possessing high volatility or other properties promoting migration through the soil. Aldicarb (Temik), a ca ...
. Such products include Kocide 3000, produced by Kocide L.L.C. 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. It is now sold as Microkote either in a solution you apply yourself, or as treated pots.


Other copper(II) hydroxides

Together with other components, copper(II) hydroxides are numerous. Several copper(II)-containing
minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed ...
contain hydroxide. Notable examples include
azurite Azurite is a soft, deep-blue copper mineral produced by weathering of copper ore deposits. During the early 19th century, it was also known as chessylite, after the type locality at Chessy-les-Mines near Lyon, France. The mineral, a basic carb ...
,
malachite Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO3(OH)2. This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fracture ...
,
antlerite Antlerite is a greenish hydrous copper sulfate mineral, with the formula Cu3(SO4)(OH)4. It occurs in tabular, acicular, or fibrous crystals with a vitreous luster. Originally believed to be a rare mineral, antlerite was found to be the primary o ...
, and
brochantite Brochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is Cu4SO4(OH)6. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it was named by Armand Lévy for his fellow Frenchman, geologist ...
. Azurite (2CuCO3·Cu(OH)2) and malachite (CuCO3·Cu(OH)2) are hydroxy-
carbonates A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...
, whereas
antlerite Antlerite is a greenish hydrous copper sulfate mineral, with the formula Cu3(SO4)(OH)4. It occurs in tabular, acicular, or fibrous crystals with a vitreous luster. Originally believed to be a rare mineral, antlerite was found to be the primary o ...
(CuSO4·2Cu(OH)2) and
brochantite Brochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is Cu4SO4(OH)6. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it was named by Armand Lévy for his fellow Frenchman, geologist ...
(CuSO4·3Cu(OH)2) are hydroxy-
sulfates The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many a ...
. Many synthetic copper(II) hydroxide derivatives have been investigated.


References


External links


Material Safety Data Sheet
{{Hydroxides Copper(II) compounds Hydroxides Oxidizing agents Catalysts