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 che ...

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 ...

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 microphysica ...

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

, 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 gaseou ...

, 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 structural polymorph form of sphalerite. The iron content is variable up to eight percent.Palache, Charles, Harry Berman & Clifford Frondel (1 ...

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- ...

or the

structure, with a Cu-I distance of 2.338 Å. Copper(I) bromide and copper(I) chloride 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. 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 ...

and a soluble copper(II) salt such

copper sulfate Copper sulfate may refer to: * 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 brig ...

. :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 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 class ...

, 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 miscible ...

chloroform Chloroform, or trichloromethane, is an organic compound with formula C H Cl3 and a common organic solvent. It is a colorless, strong-smelling, dense liquid produced on a large scale as a precursor to PTFE. It is also a precursor to various ...

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 ur ...

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

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, Sonogashira and Ullmann 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 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 petr ...

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