Copper(I) chloride

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Copper(I) chloride
Copper(I) chloride purified.jpg
IUPAC name
Copper(I) chloride
Other names
Cuprous chloride
3D model (JSmol)
ECHA InfoCard 100.028.948 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-842-9
PubChem CID
RTECS number
  • GL6990000
  • InChI=1S/ClH.Cu/h1H;/q;+1/p-1 Yes check.svgY
  • InChI=1/ClH.Cu/h1H;/q;+1/p-1
  • Cl[Cu]
Molar mass 98.999 g/mol [1]
Appearancewhite powder, slightly green from oxidized impurities
Density 4.14 g/cm3 [1]
Melting point 423 °C (793 °F; 696 K) [1]
Boiling point 1,490 °C (2,710 °F; 1,760 K) (decomposes) [1]
0.047 g/L (20 °C) [1]
Solubility insoluble in ethanol,
acetone; [1] soluble in concentrated HCl, NH4OH
Band gap 3.25 eV (300 K, direct) [2]
-40.0·10−6 cm3/mol [3]
1.930 [4]
Zincblende, cF20
F43m, No. 216 [5]
a = 0.54202 nm
0.1592 nm3
GHS labelling:
GHS-pictogram-exclam.svg GHS-pictogram-pollu.svg
H302, H410
P264, P270, P273, P301+P312, P330, P391, P501
NFPA 704 (fire diamond)
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
140 mg/kg
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 1 mg/m3 (as Cu) [6]
REL (Recommended)
TWA 1 mg/m3 (as Cu) [6]
IDLH (Immediate danger)
TWA 100 mg/m3 (as Cu) [6]
Safety data sheet (SDS) JT Baker
Related compounds
Other anions
Copper(I) fluoride
Copper(I) bromide
Copper(I) iodide
Other cations
Silver(I) chloride
Gold(I) chloride
Related compounds
Copper(II) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)
A white precipitate of Copper(I) Chloride suspended in a solution of Ascorbic Acid in a 2 dram vial. Copper(I) Chloride Precipitate.jpg
A white precipitate of Copper(I) Chloride suspended in a solution of Ascorbic Acid in a 2 dram vial.
IR absorption spectrum of copper(I) chloride IR Spectrum of Copper(I) chloride.png
IR absorption spectrum of 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 green due to the presence of copper(II) chloride (CuCl2). [7]



Copper(I) chloride was first prepared by Robert Boyle in the mid-seventeenth century [8] from mercury(II) chloride ("Venetian sublimate") and copper metal:

HgCl2 + 2 Cu → 2 CuCl + Hg

In 1799, J.L. Proust characterized the two different chlorides of copper. He prepared CuCl by heating CuCl2 at red heat in the absence of air, causing it to lose half of its combined chlorine followed by removing residual CuCl2 by washing with water. [9]

An acidic solution of CuCl was formerly used for analysis of carbon monoxide content in gases, for example in Hempel's gas apparatus[ clarification needed ]. [10] This application was significant [11] during the nineteenth and early twentieth centuries when coal gas was widely used for heating and lighting.


Copper(I) chloride is produced industrially by the direct combination of copper metal and chlorine at 450–900 °C: [12] [13]

Copper(I) chloride can also be prepared by reducing copper(II) chloride with sulfur dioxide, or with ascorbic acid (vitamin C) that acts as a reducing sugar:

Many other reducing agents can be used. [14]


Copper(I) chloride has the cubic zincblende 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). [5]

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:

CuCl + 1 P(C6H5)3 → 1/4 {CuCl[P(C6H5)3]}4
CuCl + 2 P(C6H5)3 → CuCl[P(C6H5)3)]2
CuCl + 3 P(C6H5)3 → CuCl[P(C6H5)3)]3

Although CuCl is insoluble in water, it dissolves in aqueous solutions containing suitable donor molecules. It forms complexes with halide ions, for example forming H3O+ CuCl2 in concentrated hydrochloric acid. Chloride is displaced by CN and S2O32−.

Solutions of CuCl in HCl or NH3 absorb carbon monoxide to form colourless complexes such as the chloride-bridged dimer [CuCl(CO)]2. The same hydrochloric acid solutions also react with acetylene gas to form [CuCl(C2H2)]. Ammoniacal solutions of CuCl react with acetylenes to form the explosive copper(I) acetylide, 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 dienes such as 1,5-cyclooctadiene are particularly stable: [15]

CuCl COD dimer - 2.png

In absence of other ligands, its aqueous solutions are unstable with respect to disproportionation: [16]

2 CuCl → Cu + CuCl2

In part for this reason samples in air assume a green coloration.


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 in the presence of aluminium chloride is exploited in the COPureSM process.

In organic synthesis

CuCl is used with carbon monoxide, aluminium chloride, and hydrogen chloride in the Gatterman-Koch reaction to form benzaldehydes.

In the Sandmeyer reaction. [17] [18] Treatment of an arenediazonium salt with CuCl leads to an aryl chloride, for example:

CuCl Sandmeyer.png

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 [19] led to the development of organocuprate reagents that are widely used today in organic synthesis: [20]

CuCl Kharasch reaction.png

This finding led to the development of organocopper chemistry. For example, CuCl reacts with methyllithium (CH3Li) to form "Gilman reagents" 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: [21]

CuCl sorbate ester alkylation.png

Here, Bu indicates an n-butyl 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 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, copper chlorides, like all copper compounds, emit green-blue.

Natural occurrence

Natural form of CuCl is the rare mineral nantokite. [22] [23]

Related Research Articles

<span class="mw-page-title-main">Iron(III) chloride</span> Inorganic compound

Iron(III) chloride is the inorganic compound with the formula FeCl3. Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The color depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red.

<span class="mw-page-title-main">Gilman reagent</span>

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 replace the halide group with an R group (the Corey–House reaction). Such displacement reactions allow for the synthesis of complex products from simple building blocks.

In organic chemistry, an acyl chloride is an organic compound with the functional group −C(=O)Cl. Their formula is usually written R−COCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl. Acyl chlorides are the most important subset of acyl halides.

In organic chemistry, an aryl halide is an aromatic compound in which one or more hydrogen atoms, directly bonded to an aromatic ring are replaced by a halide. The haloarene are different from haloalkanes because they exhibit many differences in methods of preparation and properties. The most important members are the aryl chlorides, but the class of compounds is so broad that there are many derivatives and applications.

<span class="mw-page-title-main">Acyl halide</span> Oxoacid compound with an –OH group replaced by a halogen

In organic chemistry, an acyl halide is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group.

<span class="mw-page-title-main">Zinc chloride</span> Chemical compound

Zinc chloride is the name of inorganic chemical compounds with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. This salt is hygroscopic and even deliquescent. Zinc chloride finds wide application in textile processing, metallurgical fluxes, and chemical synthesis. No mineral with this chemical composition is known aside from the very rare mineral simonkolleite, Zn5(OH)8Cl2·H2O.

<span class="mw-page-title-main">Hydrogen bromide</span> Chemical compound

Hydrogen bromide is the inorganic compound with the formula HBr. It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room temperature. Aqueous solutions that are 47.6% HBr by mass form a constant-boiling azeotrope mixture that boils at 124.3 °C. Boiling less concentrated solutions releases H2O until the constant-boiling mixture composition is reached.

<span class="mw-page-title-main">Lead(II) chloride</span> Chemical compound

Lead(II) chloride (PbCl2) is an inorganic compound which is a white solid under ambient conditions. It is poorly soluble in water. Lead(II) chloride is one of the most important lead-based reagents. It also occurs naturally in the form of the mineral cotunnite.

<span class="mw-page-title-main">Aluminium chloride</span> Chemical compound

Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula AlCl3. It forms hexahydrate with the formula [Al(H2O)6]Cl3, containing six water molecules of hydration. Both are colourless crystals, but samples are often contaminated with iron(III) chloride, giving a yellow color.

<span class="mw-page-title-main">Copper(II) chloride</span> Chemical compound

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.

<span class="mw-page-title-main">Iron(II) chloride</span> Chemical compound

Iron(II) chloride, also known as ferrous chloride, is the chemical compound of formula FeCl2. It is a paramagnetic solid with a high melting point. The compound is white, but typical samples are often off-white. FeCl2 crystallizes from water as the greenish tetrahydrate, which is the form that is most commonly encountered in commerce and the laboratory. There is also a dihydrate. The compound is highly soluble in water, giving pale green solutions.

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 provides a method through which one can perform unique transformations on benzene, such as halogenation, cyanation, trifluoromethylation, and hydroxylation.

The Corey–House synthesis is an organic reaction that involves the reaction of a lithium diorganylcuprate with an organic pseudohalide to form a new alkane, as well as an ill-defined organocopper species and lithium halide as byproducts.

<span class="mw-page-title-main">Diazonium compound</span> Diazonium salts of formula R-N≡N+

Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group [R−N+≡N]X where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide.

<span class="mw-page-title-main">Copper(I) cyanide</span> Chemical compound

Copper(I) cyanide is an inorganic compound with the formula CuCN. This off-white solid occurs in two polymorphs; impure samples can be green due to the presence of Cu(II) impurities. The compound is useful as a catalyst, in electroplating copper, and as a reagent in the preparation of nitriles.

Boron trichloride is the inorganic compound with the formula BCl3. This colorless gas is a reagent in organic synthesis. It is highly reactive toward water.

<span class="mw-page-title-main">Grignard reagent</span> Organometallic compounds used in organic synthesis

A Grignard reagent or Grignard compound is a chemical compound with the general formula R−Mg−X, where X is a halogen and R is an organic group, normally an alkyl or aryl. Two typical examples are methylmagnesium chloride Cl−Mg−CH3 and phenylmagnesium bromide (C6H5)−Mg−Br. They are a subclass of the organomagnesium compounds.

<span class="mw-page-title-main">Organocopper compound</span> Compound with carbon to copper bonds

Organocopper compounds is the chemistry of organometallic compounds containing a carbon to copper chemical bond. Organocopper chemistry is the study of organocopper compounds describing their physical properties, synthesis and reactions. They are reagents in organic chemistry.

Reactions of organocopper reagents involve species containing copper-carbon bonds acting as nucleophiles in the presence of organic electrophiles. Organocopper reagents are now commonly used in organic synthesis as mild, selective nucleophiles for substitution and conjugate addition reactions.

In organic chemistry, thiocarboxylic acids are organosulfur compounds related to carboxylic acids by replacement of one of the oxygen atoms with a sulfur atom. Two tautomers are possible: a thione form and a thiol form. These are sometimes also referred to as "carbothioic O-acid" and "carbothioic S-acid" respectively. Of these the thiol form is most common.


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