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).

Copper(I) chloride

Names
IUPAC name Copper(I) chloride
Other names Cuprous chloride
Identifiers
CAS Number	7758-89-6 Y
3D model (JSmol)	Interactive image
Beilstein Reference	8127933
ChEBI	CHEBI:53472 Y
ChemSpider	56403 Y
DrugBank	DB15535
ECHA InfoCard	100.028.948
EC Number	231-842-9
Gmelin Reference	13676
PubChem CID	62652
RTECS number	GL6990000
UNII	C955P95064 Y
CompTox Dashboard (EPA)	DTXSID5035242
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
SMILES Cl[Cu]
Properties
Chemical formula	CuCl
Molar mass	98.999 g/mol[1]
Appearance	white 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]
Solubility in water	0.047 g/L (20 °C)[1]
Solubility product (Ksp)	1.72×10−7
Solubility	insoluble in ethanol, acetone;[1] soluble in concentrated HCl, NH4OH
Band gap	3.25 eV (300 K, direct)[2]
Magnetic susceptibility (χ)	-40.0·10−6 cm3/mol[3]
Refractive index (nD)	1.930[4]
Structure
Crystal structure	Zincblende, cF20
Space group	F43m, No. 216[5]
Lattice constant	a = 0.54202 nm
Lattice volume (V)	0.1592 nm3
Formula units (Z)	4
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H410
Precautionary statements	P264, P270, P273, P301+P312, P330, P391, P501
NFPA 704 (fire diamond)	3 0 0
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)	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). Y verify (what is YN ?) Infobox references

IR absorption spectrum of copper(I) chloride

History

Copper(I) chloride was first prepared by Robert Boyle and designated rosin of copper in the mid-seventeenth century from mercury(II) chloride ("Venetian sublimate") and copper metal:^[7]

HgCl₂ + 2 Cu → 2 CuCl + Hg

In 1799, Joseph Proust first differentiated two different chlorides of copper. He prepared CuCl (which he called white muriate of copper) 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.^[8]

An acidic solution of CuCl was formerly used to analyze carbon monoxide content in gases, for example in Hempel's gas apparatus where the CuCl absorbs the carbon monoxide.^[9] This application was significant during the nineteenth and early twentieth centuries when coal gas was widely used for heating and lighting.^[10]

Synthesis

Copper(I) chloride is produced industrially by the direct combination of copper metal and chlorine at 450–900 °C:^[11][12]

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) that acts as a reducing sugar:^[13][14]

2 CuCl₂ + SO₂ + 2 H₂O → 2 CuCl + H₂SO₄ + 2 HCl

2 CuCl₂ + C₆H₈O₆ → 2CuCl + 2HCl + C₆H₆O₆

Many other reducing agents can be used.^[12]

• 
  White copper(I) chloride crystals on copper wire
• 
  Copper(I) chloride partially oxidized in air

Properties

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. It 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

CuCl also forms complexes with halides. For example H₃O⁺ CuCl₂⁻ forms in concentrated hydrochloric acid.^[15] Chloride is displaced by CN⁻ and S₂O₃²⁻.^[12]

Solutions of CuCl in HCl 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 of CuCl 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:^[16]

Upon contact with water, copper(I) chloride slowly undergoes disproportionation:^[17]

2 CuCl → Cu + CuCl₂

In part for this reason, samples in air assume a green coloration.^[18]

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:^[12]

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 COPure^SM process.^[19]

In organic synthesis

CuCl is used as a co-catalyst with carbon monoxide, aluminium chloride, and hydrogen chloride in the Gatterman-Koch reaction to form benzaldehydes.^[20]

In the Sandmeyer reaction, the treatment of an arenediazonium salt with CuCl leads to an aryl chloride. For example:^[21][22]

The reaction has wide scope and usually gives good yields.^[22]

Early investigators observed that copper(I) halides catalyse 1,4-addition of Grignard reagents to alpha,beta-unsaturated ketones^[23] led to the development of organocuprate reagents that are widely used today in organic synthesis:^[24]

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 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:^[25]

Cuprous chloride also catalyzes the dimerization of acetylene to vinylacetylene, once used as a precursor to various polymers such a neoprene.^[26]

Niche uses

CuCl is used as a catalyst in atom transfer radical polymerization (ATRP). It is also used in pyrotechnics as a blue/green coloring agent. In a flame test, copper chlorides, like all copper compounds, emit green-blue.^[27]

Natural occurrence

Natural form of CuCl is the rare mineral nantokite.^[28][29]

See also

Copper(II) chloride

References

1. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.61. ISBN 1-4398-5511-0.
2. Garro, Núria; Cantarero, Andrés; Cardona, Manuel; Ruf, Tobias; Göbel, Andreas; Lin, Chengtian; Reimann, Klaus; Rübenacke, Stefan; Steube, Markus (1996). "Electron-phonon interaction at the direct gap of the copper halides". Solid State Communications. 98 (1): 27–30. Bibcode:1996SSCom..98...27G. doi:10.1016/0038-1098(96)00020-8.
3. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.132. ISBN 1-4398-5511-0.
4. Patnaik, Pradyot (2002) Handbook of Inorganic Chemicals. McGraw-Hill, ISBN 0-07-049439-8
5. Hull, S.; Keen, D. A. (1994). "High-pressure polymorphism of the copper(I) halides: A neutron-diffraction study to ~10 GPa". Physical Review B. 50 (9): 5868–5885. Bibcode:1994PhRvB..50.5868H. doi:10.1103/PhysRevB.50.5868. PMID 9976955.
6. NIOSH Pocket Guide to Chemical Hazards. "#0150". National Institute for Occupational Safety and Health (NIOSH).
7. Boyle, Robert (1666). Considerations and experiments about the origin of forms and qualities. Oxford. pp. 286–288.
8. Proust, J. L. (1799). "Recherches sur le Cuivre". Annales de chimie. 32: 26–54.
9. Martin, Geoffrey (1922). Industrial and Manufacturing Chemistry (Part 1, Organic ed.). London: Crosby Lockwood. p. 408.
10. Lewes, Vivian H. (1891). "The Analysis of Illuminationg Gases". Journal of the Society of Chemical Industry. 10: 407–413.
11. Richardson, H. W. (2003). "Copper Compounds". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.0315161618090308.a01.pub2. ISBN 0471238961.
12. Zhang, J.; Richardson, H. W. (2016). "Copper Compounds". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–31. doi:10.1002/14356007.a07_567.pub2. ISBN 978-3-527-30673-2.
13. Glemser, O.; Sauer, H. (1963). "Copper(I) Chloride". In Brauer, G. (ed.). Handbook of Preparative Inorganic Chemistry. Vol. 1 (2nd ed.). New York: Academic Press. p. 1005.
14. Tuğba Akbıyık; İnci Sönmezoğlu; Kubilay Güçlü; İzzet Tor; Reşat Apak (2012). "Protection of Ascorbic Acid from Copper(II)−Catalyzed Oxidative Degradation in the Presence of Fruit Acids: Citric, Oxalic, Tartaric, Malic, Malonic, and Fumaric Acids". International Journal of Food Properties. 15 (2): 398–411. doi:10.1080/10942912.2010.487630. S2CID 85408826.
15. J. J. Fritz (1980). "Chloride complexes of copper(I) chloride in aqueous solution". J. Phys. Chem. 84 (18): 2241–2246. doi:10.1021/j100455a006.
16. Nicholls, D. (1973) Complexes and First-Row Transition Elements, Macmillan Press, London.
17. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1185. ISBN 978-0-08-037941-8.
18. Pastor, Antonio C. (1986) U.S. patent 4,582,579 "Method of preparing cupric ion free cuprous chloride" Section 2, lines 4–41.
19. Xiaozhou Ma; Jelco Albertsma; Dieke Gabriels; Rens Horst; Sevgi Polat; Casper Snoeks; Freek Kapteijn; Hüseyin Burak Eral; David A. Vermaas; Bastian Mei; Sissi de Beer; Monique Ann van der Veen (2023). "Carbon monoxide separation: past, present and future". Chemical Society Reviews. 52 (11): 3741–3777. doi:10.1039/D3CS00147D. PMC 10243283. PMID 37083229.
20. Dilke, M. H.; Eley, D. D. (1949). "550. The Gattermann–Koch reaction. Part II. Reaction kinetics". J. Chem. Soc.: 2613–2620. doi:10.1039/JR9490002613. ISSN 0368-1769.
21. Wade, L. G. (2003) Organic Chemistry, 5th ed., Prentice Hall, Upper Saddle River, New Jersey, p. 871. ISBN 013033832X.
22. March, J. (1992) Advanced Organic Chemistry, 4th ed., Wiley, New York. p. 723. ISBN 978-0-470-46259-1
23. 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.
24. Jasrzebski, J. T. B. H.; van Koten, G. (2002) Modern Organocopper Chemistry, N. Krause (ed.). Wiley-VCH, Weinheim, Germany. p. 1. doi:10.1002/3527600086.ch1 ISBN 9783527600083.
25. 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. ISBN 978-0-471-97924-1.
26. Trotuş, Ioan-Teodor; Zimmermann, Tobias; Schüth, Ferdi (2014). "Catalytic Reactions of Acetylene: A Feedstock for the Chemical Industry Revisited". Chemical Reviews. 114 (3): 1761–1782. doi:10.1021/cr400357r. PMID 24228942.
27. Barrow, R F; Caldin, E F (1949-01-01). "Some Spectroscopic Observations on Pyrotechnic Flames". Proceedings of the Physical Society. Section B. 62 (1): 32–39. doi:10.1088/0370-1301/62/1/305. ISSN 0370-1301.
28. "Nantokite".
29. "List of Minerals". 21 March 2011.

External links

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