Copper(I) chloride

Copper(I) chloride
IUPAC name Copper(I) chloride
Other names Cuprous chloride
Identifiers
CAS number	7758-89-6 Y
PubChem	62652
ChemSpider	56403 Y
EC number	231-842-9
ChEBI	CHEBI:53472 Y
RTECS number	GL6990000
Jmol-3D images	Image 1
SMILES Cl[Cu]
InChI InChI=1S/ClH.Cu/h1H;/q;+1/p-1 Y Key: OXBLHERUFWYNTN-UHFFFAOYSA-M Y InChI=1/ClH.Cu/h1H;/q;+1/p-1 Key: OXBLHERUFWYNTN-REWHXWOFAC
Properties
Molecular formula	CuCl
Molar mass	98.999 g/mol
Appearance	white powder, slightly green from oxidized impurities
Density	4.145 g/cm3
Melting point	426 °C (703 K)
Boiling point	1490 °C (1760 K) (decomp.)
Solubility in water	0.0062 g/100 mL (20 °C)
Solubility product, Ksp	1.72 x 10-7
Solubility	insoluble in ethanol acetone; soluble in concentrated HCl, NH4OH
Refractive index (nD)	1.930[1]
Structure
Crystal structure	Zinc blende structure
Hazards
MSDS	JT Baker
EU Index	029-001-00-4
EU classification	Harmful (Xn) Dangerous for the environment (N)
R-phrases	R22, R50/53
S-phrases	(S2), S22, S60, S61
NFPA 704	0 3 0
Flash point	Non-flammable
LD50	140 mg/kg
Related compounds
Other anions	Copper(I) bromide Copper(I) iodide
Other cations	Copper(II) chloride Silver(I) chloride
Y chloride (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

IR 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.^[2]

History

Copper(I) chloride was first prepared by Robert Boyle in the mid-seventeenth century^[3] 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.^[4]

An acidic solution of CuCl was formerly used for analysis of carbon monoxide content in gases, for example in Hempel's gas apparatus.^[5] This application was significant^[6] during the time that coal gas was widely used for heating and lighting, during the nineteenth and early twentieth centuries.

Chemical properties

• 

  White copper(I) chloride crystals on copper wire

• 

  Copper(I) chloride formed by treating ascorbic acid with copper(II) chloride

• 

  Copper(I) chloride partially oxidized in air

Copper(I) chloride is a Lewis acid, which is classified as soft according to the Hard-Soft Acid-Base concept. Thus, it tends to form stable complexes with soft Lewis bases such as triphenylphosphine:

CuCl + P(C₆H₅)₃ → [CuCl(P(C₆H₅)₃)]₄

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^- with concentrated hydrochloric acid. It is attacked by CN^-, S₂O₃^2-, and NH₃ to give the corresponding complexes.

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. Complexes of CuCl with alkenes 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:^[7]

In absence of other ligands, its aqueous solutions are unstable with respect to disproportionation into Cu and CuCl₂.^[8] In part for this reason samples in air assume a green coloration (see photograph in upper right).

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

6 CuCl + 3/2 O₂ + 3 H₂O → 2 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 COPure^SM process.

In organic synthesis

In the Sandmeyer reaction.^[9] 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^[10] led to the development of organocuprate reagents that are widely used today in organic synthesis:^[11]

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:^[12]

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).

References

1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
2. ^ United States Patent US4582579 "method of preparing cupric ion free cuprous chloride" Section 2, lines 4-41 , via www.freepatentsonline.com
3. ^ Boyle, Robert (1666). Considerations and experiments about the origin of forms and qualities. Oxford. As reported in Mellor. 
4. ^ Proust, J. L. (1799). Ann. Chim. Phys. (1) 32: 26. 
5. ^ Martin, Geoffrey (1917). Industrial and Manufacturing Chemistry (Part 1, Organic ed.). London: Crosby Lockwood. pp. 330–31. 
6. ^ Lewes, Vivian H. (1891). "Journal of the Society of Chemical Industry". Journal of the Society of Chemical Industry 10: 407–413. http://books.google.com/?id=oSEAAAAAMAAJ&pg=PA408&lpg=PA407#v=onepage&q. 
7. ^ Nicholls, D. Complexes and First-Row Transition Elements, Macmillan Press, London, 1973.
8. ^ Greenwood, N.N.; Earnshaw, A. Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
9. ^ (a) Wade, L. G. Organic Chemistry, 5th ed., p. 871, Prentice Hall, Upper Saddle RIver, New Jersey, 2003. (b) March, J. Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.
10. ^ Kharasch, M. S; Tawney, P. O (1941). "Factors Determining the Course and Mechanisms of Grignard Reactions. II. The Effect of Metallic Compounds on the Reaction between Isophorone and Methylmagnesium Bromide". J. Am. Chem. Soc. 63 (9): 2308. doi:10.1021/ja01854a005. 
11. ^ Jasrzebski, J. T. B. H.; van Koten, G. in Modern Organocopper Chemistry, (N. Krause, ed.), p. 1, Wiley-VCH, Weinheim, Germany, 2002.
12. ^ (a) Bertz, S. H.; Fairchild, E. H. in Handbook of Reagents for Organic Synthesis, Volume 1: Reagents, Auxiliaries and Catalysts for C-C Bond Formation, (R. M. Coates, S. E. Denmark, eds.), pp. 220-3, Wiley, New York, 1999. (b) Munch-Petersen, J., et al., Acta Chimica Scand., 15, 277 (1961).

Further reading

1. Mellor, J. W., A Comprehensive Treatise on Inorganic and Theoretical Chemistry, Volume III, pp157-168. Longmans, Green & Co., London, 1967 (new impression).

External links

• National Pollutant Inventory - Copper and compounds fact sheet
• The COPure^SM Process for purifying CO utilizing a copper chloride complex