Copper(II) nitrate describes any member of the family of
inorganic compounds with the formula
Cu(
NO3)
2(H
2O)
x. The hydrates are blue
solid
Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ...
s.
Anhydrous copper nitrate forms blue-green crystals and
sublimes in a vacuum at 150-200 °C. Common hydrates are the hemipentahydrate and trihydrate.
Synthesis and reactions
Hydrated copper(II) nitrate
Hydrated copper nitrate is prepared by treating copper metal or its oxide with
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
:
[
:Cu + 4HNO3 → Cu(NO3)2. + 2H2O + 2NO2
The same salts can be prepared treating copper metal with an aqueous solution of ]silver nitrate
Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar causti ...
. That reaction illustrates the ability of copper metal to reduce silver ions.
In aqueous solution, the hydrates exist as the aqua complex u(H2O)6sup>2+. Such complexes are highly labile owing to the d9 electronic configuration of copper(II).
Attempted dehydration of any of the hydrated copper(II) nitrates by heating affords the oxides, not Cu(NO3)2. At 80 °C, the hydrates convert to "basic copper nitrate" (Cu2(NO3)(OH)3), which converts to CuO at 180 °C.[ Exploiting this reactivity, copper nitrate can be used to generate ]nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
by heating it until decomposition and passing the fumes directly into water. This method is similar to the last step in the Ostwald process The Ostwald process is a chemical process used for making nitric acid (HNO3). Wilhelm Ostwald developed the process, and he patented it in 1902. The Ostwald process is a mainstay of the modern chemical industry, and it provides the main raw materi ...
. The equations are as follows:
:2 Cu(NO3)2 → 2 CuO + 4 NO2 + O2
:3NO2 + H2O → 2HNO3 + NO
Treatment of copper(II) nitrate solutions with triphenylphosphine
Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to P Ph3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists ...
, triphenylarsine
Triphenylarsine is the chemical compound with the formula As(C6H5)3. This organoarsenic compound, often abbreviated As Ph3, is a colorless crystalline solid that is used as a ligand and a reagent in coordination chemistry and organic synthesis. T ...
, and triphenylstibine
Triphenylstibine is the chemical compound with the formula Sb(C6H5)3. Abbreviated SbPh3, this colourless solid is often considered the prototypical organoantimony compound. It is used as a ligand in coordination chemistry and as a reagent in o ...
gives the corresponding copper(I) complexes u(E(C6H5)3)3O3 (E = P, As, Sb). The group V ligand is oxidized to the oxide.
Anhydrous copper(II) nitrate
Two polymorphs of anhydrous Cu(NO3)2 are known. The so-called β-form is a covalent molecular complex, as evidenced by its tendency to sublime. It is one of the few anhydrous transition metal nitrates. It cannot be prepared by reactions containing or producing water. Instead, anhydrous Cu(NO3)2 forms when copper metal is treated with dinitrogen tetroxide:
:Cu + 2 N2O4 → Cu(NO3)2 + 2 NO
The α-form of anhydrous copper(II) nitrate is a coordination polymer.
Structure
Anhydrous copper(II) nitrate
: left, Structure of anhydrous copper(II) nitrate.
Anhydrous copper(II) nitrate has been crystallized in two solvate
Solvation (or dissolution) describes the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the ...
-free polymorphs.
Hydrated copper(II) nitrate
Five hydrates
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...
have been reported: the monohydrate (Cu(NO3)2·H2O),[ the sesquihydrate (Cu(NO3)2·1.5H2O), the hemipentahydrate (Cu(NO3)2·2.5H2O), a trihydrate (Cu(NO3)2·3H2O), and a hexahydrate ( u(H2O)6NO3)2). The hexahydrate is interesting because the Cu-O distances are all equal, not revealing the usual effect of Jahn-Teller distortion that is otherwise characteristic of octahedral Cu(II) complexes. This non-effect is attributed to the strong ]hydrogen bonding
In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a l ...
that limits the elasticity of the Cu-O bonds.
Applications
Copper(II) nitrate finds a variety of applications, the main one being its conversion to 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 ...
, which is used as catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
for a variety of processes in organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, ...
. Its solutions are used in textiles and polishing agents for other metals. Copper nitrates are found in some pyrotechnic
Pyrotechnics is the science and craft of creating such things as fireworks, safety matches, oxygen candles, explosive bolts and other fasteners, parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demolition. ...
s.[H.Wayne Richardson "Copper Compounds" Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. .] It is often used in school laboratories to demonstrate chemical voltaic cell
A galvanic cell or voltaic cell, named after the scientists Luigi Galvani and Alessandro Volta, respectively, is an electrochemical cell in which an electric current is generated from spontaneous Oxidation-Reduction reactions. A common apparatus g ...
reactions. It is a component in some ceramic glazes and metal patinas.
Organic synthesis
Copper nitrate, in combination with acetic anhydride, is an effective reagent for nitration of aromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
compounds, known as the Menke nitration
The Menke nitration is the nitration of electron rich aromatic compounds with cupric nitrate and acetic anhydride. The reaction introduces the nitro group
In organic chemistry, nitro compounds are organic compounds that contain one or more n ...
.
Hydrated copper nitrate adsorbed onto clay affords a reagent called "Claycop". The resulting blue-colored clay is used as a slurry, for example for the oxidation of thiol
In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl gro ...
s to disulfide
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...
s. Claycop is also used to convert dithioacetals to carbonyls. A related reagent based on montmorillonite
Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystals, known as clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite gro ...
has proven useful for the nitration
In organic chemistry, nitration is a general class of chemical processes for the introduction of a nitro group into an organic compound. The term also is applied incorrectly to the different process of forming nitrate esters between alcohols an ...
of aromatic compounds.
Naturally occurring copper nitrates
No mineral of the ideal Cu(NO3)2 formula, or the hydrate, are known. Likasite, Cu3(NO3)(OH)5.2H2O and buttgenbachite, Cu19(NO3)2(OH)32Cl4·2H2O are related minerals.[
Natural basic copper nitrates include the rare minerals ]gerhardtite
Copper(II) nitrate describes any member of the family of inorganic compounds with the formula Cu( NO3)2(H2O)x. The hydrates are blue solids. Anhydrous copper nitrate forms blue-green crystals and sublimes in a vacuum at 150-200 °C. Common hy ...
and rouaite, both being polymorphs of Cu2(NO3)(OH)3 substance.[
]
References
External links
National Pollutant Inventory – Copper and compounds fact sheet
{{nitrates
Copper(II) compounds
Nitrates
Pyrotechnic oxidizers
Pyrotechnic colorants
Oxidizing agents
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