Copper(II) nitrate describes any member of the family of

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

s with the formula Cu( NO₃)₂(H₂O)_x. The hydrates are

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

blue

solid Solid is a state of matter where molecules are closely packed and can not slide past each other. Solids resist compression, expansion, or external forces that would alter its shape, with the degree to which they are resisted dependent upon the ...

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 an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

: : The same salts can be prepared treating copper metal with an

aqueous solution An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, also known as sodium chloride (NaCl), in water ...

of silver nitrate. That reaction illustrates the ability of copper metal to reduce silver ions. In aqueous solution, the hydrates exist as the aqua complex . Such complexes are highly labile and subject to rapid ligand exchange due to the d⁹ electronic configuration of copper(II). Attempted dehydration of any of the hydrated copper(II) nitrates by heating affords the oxides, not . At 80 °C the hydrates convert to "basic copper nitrate", , which converts to at 180 °C. Exploiting this reactivity, copper nitrate can be used to generate

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 equations are as follows: : : Treatment of copper(II) nitrate solutions with triphenylphosphine, triphenylarsine, and triphenylstibine gives the corresponding copper(I) complexes (E = P, As, Sb; Ph = ). The group V ligand is oxidized to the oxide.

Anhydrous copper(II) nitrate

Anhydrous is one of the few anhydrous transition metal nitrates. It cannot be prepared by reactions containing or producing water. Instead, anhydrous forms when copper metal is treated with

dinitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

: :

Structure

Anhydrous copper(II) nitrate

Two polymorphs of anhydrous copper(II) nitrate, α and β, are known. Both polymorphs are three-dimensional coordination polymer networks with infinite chains of copper(II) centers and nitrate groups. The α form has only one Cu environment, with +1coordination, but the β form has two different copper centers, one with +1and one that is square planar. The nitromethane solvate also features " +1coordination", with four short Cu-O bonds of approximately 200 pm and one longer bond at 240 pm. Heating solid anhydrous copper(II) nitrate under a vacuum to 150-200 °C leads to sublimation and " cracking" to give a vapour of monomeric copper(II) nitrate molecules. In the vapour phase, the molecule features two bidentate nitrate ligands.

Hydrated copper(II) nitrate

Five hydrates have been reported: the monohydrate (), the sesquihydrate (), the hemipentahydrate (), a trihydrate (), and a hexahydrate (. The crystal structure of the hexahydrate appeared to show six almost equal Cu–O distances, not revealing the usual effect of a Jahn-Teller distortion that is otherwise characteristic of octahedral Cu(II) complexes. This non-effect was attributed to the strong

hydrogen bonding In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...

that limits the elasticity of the Cu-O bonds but it is probably due to nickel being misidentified as copper in the refinement.

Applications

Copper(II) nitrate finds a variety of applications, the main one being its conversion to copper(II) oxide, which is used as

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

for a variety of processes in

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...

. 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 fireworks, but also includes safety matches, oxygen candles, explosive bolts (and other fasteners), parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demol ...

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 reactions. It is a component in some ceramic glazes and metal patinas.

Organic synthesis

Copper nitrate, in combination with

acetic anhydride Acetic anhydride, or ethanoic anhydride, is the chemical compound with the chemical formula, formula . Commonly abbreviated , it is one the simplest organic acid anhydride, anhydrides of a carboxylic acid and is widely used in the production of c ...

, is an effective reagent for nitration of

aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...

compounds, known as the Menke nitration. 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 thiols to

disulfide In chemistry, a disulfide (or disulphide in British English) is a compound containing a functional group or the anion. The linkage is also called an SS-bond or sometimes a disulfide bridge and usually derived from two thiol groups. In inorg ...

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 grou ...

has proven useful for the nitration of aromatic compounds.

Electrowinning

Copper(II) nitrate may also be used for copper electrowinning on small scale with a ammonia (NH₃) as a byproduct.

Naturally occurring copper nitrates

No mineral of the ideal formula, or the hydrates, are known. Likasite, and buttgenbachite, are related minerals. Natural basic copper nitrates include the rare minerals gerhardtite and rouaite, both being polymorphs of . A much more complex, basic, hydrated and chloride-bearing natural salt is buttgenbachite.

References

External links

National Pollutant Inventory – Copper and compounds fact sheet
{{nitrates Copper(II) compounds Nitrates Pyrotechnic oxidizers Pyrotechnic colorants Oxidizing agents