Copper(I) iodide is the

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

with the formula CuI. It is also known as cuprous iodide. It is useful in a variety of applications ranging from

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

cloud seeding Cloud seeding is a type of weather modification that aims to change the amount or type of precipitation that falls from clouds by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical p ...

. Copper(I) iodide is white, but samples often appear tan or even, when found in nature as rare mineral

marshite Marshite (CuI) is a naturally occurring isometric halide mineral with occasional silver (Ag) substitution for copper (Cu).Prior, G.T. (1902“The identity of kilbrickenite with geocronite: And analyses of miersite, marshite, and copper-pyrites� ...

, reddish brown, but such color is due to the presence of impurities. It is common for samples of iodide-containing compounds to become discolored due to the facile aerobic oxidation of the iodide anion to molecular iodine.

Structure

Copper(I)

iodide An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine defic ...

, like most binary (containing only two elements) metal halides, is an

inorganic polymer An inorganic polymer is a polymer with a skeletal structure that does not include carbon atoms in the backbone. Polymers containing inorganic and organic components are sometimes called hybrid polymers, and most so-called inorganic polymers are ...

. It has a rich

phase diagram A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions (pressure, temperature, volume, etc.) at which thermodynamically distinct phases (such as solid, liquid or gaseous ...

, meaning that it exists in several crystalline forms. It adopts a zinc blende structure below 390 °C (γ-CuI), a

wurtzite Wurtzite is a zinc and iron sulfide mineral with the chemical formula , a less frequently encountered Polymorphism (materials science), structural polymorph form of sphalerite. The iron content is variable up to eight percent.Palache, Charles, Har ...

structure between 390 and 440 °C (β-CuI), and a

rock salt Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pi ...

structure above 440 °C (α-CuI). The ions are tetrahedrally coordinated when in the

zinc blende Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Va ...

or the

structure, with a Cu-I distance of 2.338 Å.

Copper(I) bromide Copper(I) bromide is the chemical compound with the formula CuBr. This diamagnetic solid adopts a polymeric structure akin to that for zinc sulfide. The compound is widely used in the synthesis of organic compounds and as a lasing medium in ...

and

copper(I) chloride Copper(I) chloride, commonly called cuprous chloride, is the lower chloride of copper, with the formula CuCl. The substance is a white solid sparingly soluble in water, but very soluble in concentrated hydrochloric acid. Impure samples appear gre ...

also transform from the zinc blende structure to the wurtzite structure at 405 and 435 °C, respectively. Therefore, the longer the copper – halide bond length, the lower the temperature needs to be to change the structure from the zinc blende structure to the wurtzite structure. The interatomic distances in copper(I) bromide and copper(I) chloride are 2.173 and 2.051 Å, respectively. Consistent with its covalency, CuI is a p-type semiconductor.

Preparation

Copper(I) iodide can be prepared by heating iodine and copper in concentrated

hydriodic acid Hydroiodic acid (or hydriodic acid) is an aqueous solution of hydrogen iodide (HI). It is a strong acid, one that is ionized completely in an aqueous solution. It is colorless. Concentrated solutions are usually 48% to 57% HI. Reactions Hy ...

. In the laboratory however, copper(I) iodide is prepared by simply mixing an aqueous solution of

potassium iodide Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are u ...

and a soluble copper(II) salt such

copper sulfate Copper sulfate may refer to: * Copper(II) sulfate, CuSO4, a common compound used as a fungicide and herbicide * Copper(I) sulfate Copper(I) sulfate, also known as cuprous sulfate, is an inorganic compound with the chemical formula Cu2 SO4. It ...

. :Cu²⁺ + 2I⁻ → CuI + 0.5I₂

Reactions

Cuprous iodide, which degrades on standing, can be purified by dissolution into concentrated solution of

followed by dilution. :CuI + I⁻ CuI₂⁻ Copper(I) iodide reacts with mercury vapors to form copper tetraiodomercurate: :4CuI + Hg → Cu₂HgI₄ + 2Cu This reaction can be used for the detection of

mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

since the white (CuI) to brown (Cu₂HgI₄) color change is dramatic. Copper(I) iodide is used in the synthesis of Cu(I) clusters. which is polymetal complex compounds. Copper(I) iodide dissolves in

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...

, yielding a diverse complexes. Upon crystallization, molecular or polymeric compounds can be isolated. Dissolution is also observed when a solution of the appropriate complexing agent in

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...

chloroform Chloroform, or trichloromethane, is an organic compound with chemical formula, formula Carbon, CHydrogen, HChlorine, Cl3 and a common organic solvent. It is a colorless, strong-smelling, dense liquid produced on a large scale as a precursor to ...

is used. For example,

thiourea Thiourea () is an organosulfur compound with the formula and the structure . It is structurally similar to urea (), except that the oxygen atom is replaced by a sulfur atom (as implied by the ''thio-'' prefix); however, the properties of urea a ...

and its derivatives can be used. Solids that crystallize out of those solutions are composed of hybrid inorganic chains.

Uses

CuI is used as a reagent in

. In combination with 1,2- or 1,3 diamine ligands, CuI catalyzes the conversion of aryl-, heteroaryl-, and vinyl-bromides into the corresponding iodides. NaI is the typical iodide source and dioxane is a typical solvent (see

aromatic Finkelstein reaction The Finkelstein reaction named after the German chemist Hans Finkelstein, is an SN2 reaction (Substitution Nucleophilic Bimolecular reaction) that involves the exchange of one halogen atom for another. It is an equilibrium reaction, but the rea ...

). Aryl halides are used to form carbon–carbon and carbon–heteroatom bonds in process such as the Heck, Stille,

Suzuki is a Japan, Japanese multinational corporation headquartered in Minami-ku, Hamamatsu, Japan. Suzuki manufactures automobiles, motorcycles, All-terrain vehicle, all-terrain vehicles (ATVs), outboard motor, outboard marine engines, wheelchairs ...

, Sonogashira and

Ullmann Ullmann is a German surname also associated with Jewish Europeans. It means "man from Ulm". Notable people with the surname include: * Alexander de Erény Ullmann (1850–1897), Hungarian deputy and political economist * Andrew Ullmann (born 1963) ...

type coupling reactions. Aryl iodides, however, are more reactive than the corresponding aryl bromides or aryl chlorides. 2-Bromo-1-octen-3-ol and 1-nonyne are coupled when combined with dichlorobis(triphenylphosphine)palladium(II), CuI, and

diethylamine Diethylamine is an organic compound with the formula (CH3CH2)2NH. It is a secondary amine. It is a flammable, weakly alkaline liquid that is miscible with most solvents. It is a colorless liquid, but commercial samples often appear brown due to im ...

to form 7-methylene-8-hexadecyn-6-ol. CuI is used in

, altering the amount or type of precipitation of a cloud, or their structure by dispersing substances into the atmosphere which increase water's ability to form droplets or crystals. CuI provides a sphere for moisture in the cloud to condense around, causing precipitation to increase and cloud density to decrease. The structural properties of CuI allow CuI to stabilize heat in

nylon Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic. Nylon is a silk-like thermoplastic, generally made from petro ...

in commercial and residential carpet industries, automotive engine accessories, and other markets where durability and weight are a factor. CuI is used as a source of dietary iodine in table salt and animal feed.

References

External links