Copper(I) chloride, commonly called cuprous chloride, is the lower
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride sa ...
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 formula CuCl. The substance is a white solid sparingly soluble in water, but very soluble in concentrated
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
. Impure samples appear green due to the presence of
copper(II) chloride
Copper(II) chloride is the chemical compound with the chemical formula CuCl2. The anhydrous form is yellowish brown but slowly absorbs moisture to form a blue-green dihydrate.
Both the anhydrous and the dihydrate forms occur naturally as the ver ...
(CuCl
2).
History
Copper(I) chloride was first prepared by
Robert Boyle
Robert Boyle (; 25 January 1627 – 31 December 1691) was an Anglo-Irish natural philosopher, chemist, physicist, alchemist and inventor. Boyle is largely regarded today as the first modern chemist, and therefore one of the founders of ...
in the mid-seventeenth century
from
mercury(II) chloride
Mercury(II) chloride (or mercury bichloride, mercury dichloride), historically also known as sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2. It is white crystalline solid and is ...
("Venetian sublimate") and copper metal:
:HgCl
2 + 2 Cu → 2 CuCl + Hg
In 1799,
J.L. Proust characterized the two different chlorides of copper. He prepared CuCl by heating CuCl
2 at red heat in the absence of air, causing it to lose half of its combined chlorine followed by removing residual CuCl
2 by washing with water.
An acidic solution of CuCl was formerly used for analysis of carbon monoxide content in gases, for example in Hempel's gas apparatus.
This application was significant
during the nineteenth and early twentieth centuries when
coal gas was widely used for heating and lighting.
Synthesis
Copper(I) chloride is produced industrially by the direct combination of copper metal and chlorine at 450–900 °C:
:
2 Cu + Cl2 -> 2 CuCl
Copper(I) chloride can also be prepared by
reducing copper(II) chloride with
sulfur dioxide, or with ascorbic acid (
vitamin C
Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) ...
) that acts as a
reducing sugar
A reducing sugar is any sugar that is capable of acting as a reducing agent. In an alkaline solution, a reducing sugar forms some aldehyde or ketone, which allows it to act as a reducing agent, for example in Benedict's reagent. In such a reacti ...
:
:
2 CuCl2 + SO2 + 2 H2O -> 2 CuCl + H2SO4 + 2 HCl
:
2 CuCl2 + C6H8O6 -> 2CuCl + 2HCl + C6H6O6
Many other reducing agents can be used.
Image:Copper(I)chloride crystal 01.jpg, White copper(I) chloride crystals on copper wire
File:Copper(I) chloride.jpg, Copper(I) chloride partially oxidized in air
Properties
Copper(I) chloride has the cubic
zincblende
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 ...
crystal structure at ambient conditions. Upon heating to 408 °C the structure changes to hexagonal. Several other crystalline forms of CuCl appear at high pressures (several GPa).
[
Copper(I) chloride is a Lewis acid, which is classified as soft according to the Hard-Soft Acid-Base concept. Thus, it forms a series of complexes with soft Lewis bases such as ]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 ...
:
: CuCl + 1 P(C6H5)3 → 1/4 4
: CuCl + 2 P(C6H5)3 → CuCl 6H5)3)">(C6H5)3)sub>2
: CuCl + 3 P(C6H5)3 → CuCl 6H5)3)">(C6H5)3)sub>3
Although CuCl is insoluble in water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
, it dissolves in aqueous solutions containing suitable donor molecules. It forms complexes with halide ions, for example forming H3O+ CuCl2− in concentrated hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
. Chloride is displaced by CN− and S2O32−.
Solutions of CuCl in HCl or NH3 absorb carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
to form colourless complexes such as the chloride-bridged dimer uCl(CO)sub>2. The same hydrochloric acid solutions also react with acetylene gas to form 2H2)">uCl(C2H2) 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 ...
cal solutions of CuCl react with acetylenes to form the explosive copper(I) acetylide
Copper(I) acetylide, or cuprous acetylide, is a chemical compound with the formula Cu2 C2. Although never characterized by X-ray crystallography, the material has been claimed at least since 1856. One form is claimed to be a monohydrate with for ...
, Cu2C2. Alkene complexes o can be prepared by reduction of CuCl2 by sulfur dioxide in the presence of the alkene in alcohol solution. Complexes with diene
In organic chemistry a diene ( ) (diolefin ( ) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alk''ene'' units, with the standard prefix ''di'' of systematic nomenclature. ...
s such as 1,5-cyclooctadiene are particularly stable:[Nicholls, D. (1973) ''Complexes and First-Row Transition Elements'', Macmillan Press, London.]
In absence of other ligands, its aqueous
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, or sodium chloride (NaCl), in water would be re ...
solutions are unstable with respect to disproportionation
In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. More generally, the term can ...
:
: 2 CuCl → Cu + CuCl2
In part for this reason samples in air assume a green coloration.
Uses
The main use of copper(I) chloride is as a precursor to the fungicide copper oxychloride. For this purpose aqueous copper(I) chloride is generated by comproportionation and then air-oxidized:
: Cu + CuCl2 → 2 CuCl
: 4 CuCl + O2 + 2 H2O → Cu3Cl2(OH)4 + CuCl2
Copper(I) chloride catalyzes a variety of organic reactions, as discussed above. Its affinity for carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
in the presence of aluminium chloride
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...
is exploited in the COPureSM process.
In organic synthesis
CuCl is used with carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
, aluminium chloride
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...
, and hydrogen chloride
The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...
in the Gatterman-Koch reaction to form benzaldehydes.
In the Sandmeyer reaction
The Sandmeyer reaction is a chemical reaction used to synthesize aryl halides from aryl diazonium salts using copper salts as reagents or catalysts.
It is an example of a radical-nucleophilic aromatic substitution. The Sandmeyer reaction provide ...
.[Wade, L. G. (2003) ''Organic Chemistry'', 5th ed., Prentice Hall, Upper Saddle River, New Jersey, p. 871. .] Treatment of an arenediazonium salt with CuCl leads to an aryl chloride, for example:
The reaction has wide scope and usually gives good yields.
Early investigators observed that copper(I) halides catalyse 1,4-addition of Grignard reagents to alpha,beta-unsaturated ketones led to the development of organocuprate reagents that are widely used today in organic synthesis:[Jasrzebski, J. T. B. H.; van Koten, G. (2002) ''Modern Organocopper Chemistry'', N. Krause (ed.). Wiley-VCH, Weinheim, Germany. p. 1. .]
This finding led to the development of organocopper chemistry. For example, CuCl reacts with methyllithium
Methyllithium is the simplest organolithium reagent with the empirical formula CH3Li. This s-block organometallic compound adopts an oligomeric structure both in solution and in the solid state. This highly reactive compound, invariably used in so ...
(CH3Li) to form "Gilman reagent
A Gilman reagent is a lithium and copper ( diorganocopper) reagent compound, R2CuLi, where R is an alkyl or aryl. These reagents are useful because, unlike related Grignard reagents and organolithium reagents, they react with organic halides to ...
s" such as (CH3)2CuLi, which find extensive use in organic synthesis. Grignard reagents form similar organocopper compounds. Although other copper(I) compounds such as copper(I) iodide are now more often used for these types of reactions, copper(I) chloride is still recommended in some cases:[Bertz, S. H.; Fairchild, E. H. (1999) ''Handbook of Reagents for Organic Synthesis, Volume 1: Reagents, Auxiliaries and Catalysts for C-C Bond Formation'', R. M. Coates, S. E. Denmark (eds.). Wiley, New York. pp. 220–3. .]
Here, Bu indicates an n-butyl
In organic chemistry, butyl is a four- carbon alkyl radical or substituent group with general chemical formula , derived from either of the two isomers (''n''-butane and isobutane) of butane.
The isomer ''n''-butane can connect in two ways, gi ...
group. Without CuCl, the Grignard reagent alone gives a mixture of 1,2- and 1,4-addition products (i.e., the butyl adds at the C closer to the C=O).
Copper(I) chloride is also an intermediate formed from copper(II) chloride
Copper(II) chloride is the chemical compound with the chemical formula CuCl2. The anhydrous form is yellowish brown but slowly absorbs moisture to form a blue-green dihydrate.
Both the anhydrous and the dihydrate forms occur naturally as the ver ...
in the Wacker process.
In polymer chemistry
CuCl is used as a catalyst in Atom Transfer Radical Polymerization (ATRP).
Niche uses
Copper(I) chloride is also used in pyrotechnics as a blue/green coloring agent. In a flame test
A flame test is an analytical procedure used in chemistry to detect the presence of certain elements, primarily metal ions, based on each element's characteristic flame emission spectrum (which may be affected by the presence of chloride io ...
, copper chlorides, like all copper compounds, emit green-blue.
Natural occurrence
Natural form of CuCl is the rare mineral nantokite.
References
External links
National Pollutant Inventory – Copper and compounds fact sheet
{{good article
Chlorides
Copper(I) compounds
Metal halides
Coordination complexes
Pyrotechnic colorants
Zincblende crystal structure