Copper(I) chloride

Chemical compound From Wikipedia, the free encyclopedia

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).

Quick facts Names, Identifiers ...
Copper(I) chloride
Sample of copper(I) chloride
Sample of copper(I) chloride
Unit cell of nantokite
Unit cell of nantokite
Names
IUPAC name
Copper(I) chloride
Other names
Cuprous chloride
Identifiers
3D model (JSmol)
8127933
ChEBI
ChemSpider
DrugBank
ECHA InfoCard 100.028.948 Edit this at Wikidata
EC Number
  • 231-842-9
13676
RTECS number
  • GL6990000
UNII
UN number 2802
  • InChI=1S/ClH.Cu/h1H;/q;+1/p-1 checkY
    Key: OXBLHERUFWYNTN-UHFFFAOYSA-M checkY
  • InChI=1/ClH.Cu/h1H;/q;+1/p-1
    Key: OXBLHERUFWYNTN-REWHXWOFAC
  • Cl[Cu]
Properties[1]
CuCl
Molar mass 99.00 g·mol−1
Appearance white powder, slightly green from oxidized impurities
Density
  • 4.14 g/cm3
  • 3.69 g/cm3 (molten, 423 °C (793 °F))
Melting point 423 °C (793 °F; 696 K)
Boiling point 1,490 °C (2,710 °F; 1,760 K)
0.0047 g/100 mL (20 °C (68 °F))
1.72×10−7
Vapor pressure 10 Pa (0.0015 psi) (459 °C (858 °F))
Band gap 0.56 eV (300 K (27 °C; 80 °F), direct)
−40×10−6 cm3/mol
1.930[2][page needed]
Structure[3]
Cubic, cF20
F43m, No. 216
3m
a = 3.81 Å, b = 3.81 Å, c = 9.16 Å
α = 90°, β = 90°, γ = 120°
115.23 Å3
3
Thermochemistry[1]
48.5 J⋅mol−1·K-1
86.2 J⋅mol−1·K-1
−137.2 kJ⋅mol−1
−119.9 kJ⋅mol−1
Enthalpy of fusion (ΔfH⦵fus)
 7.08 kJ⋅mol−1
Hazards
GHS labelling:[4]
GHS05: CorrosiveGHS07: Exclamation markGHS09: Environmental hazard
Danger
H302+H312, H315, H318, H410
P264, P270, P273, P280, P301+P312+P330, P302+P352+P312, P305+P351+P338+P310, P332+P313, P362, P391, P501
NFPA 704 (fire diamond)
[5]
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
2
0
1
1 mg/m3[5] (TWA)
Lethal dose or concentration (LD, LC):
  • 336 mg/kg (rat, oral)
  • 1224 mg/kg (rat, dermal)[5]
NIOSH (US health exposure limits):[6]
PEL (Permissible)
 TWA 1 mg/m3 (as Cu)
REL (Recommended)
 TWA 1 mg/m3 (as Cu)
IDLH (Immediate danger)
 TWA 100 mg/m3 (as Cu)
Related compounds
Other anions
Other cations
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).
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Occurrence

CuCl occurs as the rare mineral nantokite.[7]

Structure

Copper(I) chloride has the cubic zincblende crystal structure at ambient conditions. Upon heating to 408 °C (766 °F) the structure changes to hexagonal. Several other crystalline forms of CuCl appear at high pressures (several GPa).[8]

Synthesis

Copper(I) chloride is produced industrially by the direct combination of copper metal and chlorine at 450–900 °C (842–1,652 °F):[9][10]

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:[11][12]

2 CuCl2 + SO2 + 2 H2O → 2 CuCl + H2SO4 + 2 HCl
2 CuCl2 + C6H8O6 → 2CuCl + 2HCl + C6H6O6

Many other reducing agents can be used.[10]

Uses

The main use of copper(I) chloride is as a precursor to the fungicide copper oxychloride (Cu2(OH)3Cl). For this purpose aqueous copper(I) chloride is generated by comproportionation and then air-oxidized:[10]

Cu + CuCl2 → 2 CuCl
12 CuCl + 3 O2 + 6 H2O → 4 Cu2(OH)3Cl + 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 process.[13]

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.[14]

In the Sandmeyer reaction, the treatment of an arenediazonium salt with CuCl leads to an aryl chloride. For example:[15][16]

(Example Sandmeyer reaction using CuCl)

The reaction has wide scope and usually gives good yields.[16]

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:[17][18]

(Addition of RMgX to C=C−C=O mediated by CuCl)

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 (CuI) are now more often used for these types of reactions, copper(I) chloride is still recommended in some cases:[19]

(Alkylation of sorbate ester at 4-position mediated by CuCl)

Cuprous chloride also catalyzes the dimerization of acetylene to vinylacetylene, once used as a precursor to various polymers such a neoprene.[20]

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.[21]

Reactions

Upon contact with water, copper(I) chloride slowly undergoes disproportionation:[22]

2 CuCl → Cu + CuCl2

In part for this reason, samples in air assume a green coloration.[23]

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 the hydronium (H3O+) complex H3O+CuCl−2 forms in concentrated hydrochloric acid.[24] Chloride is displaced by cyanide (CN−) and thiosulfate (S2O2−3).[10]

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 copper(II) chloride (CuCl2) by sulfur dioxide in the presence of the alkene in alcohol solution. Complexes with dienes such as 1,5-cyclooctadiene are particularly stable:[25][page needed]

Structure of COD complex of CuCl

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:[26]

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.[27]

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.[28] This application was significant during the nineteenth and early twentieth centuries when coal gas was widely used for heating and lighting.[29]

Gallery

  • White copper(I) chloride crystals on copper wire
    White copper(I) chloride crystals on copper wire
  • Copper(I) chloride partially oxidized in air
    Copper(I) chloride partially oxidized in air
  • IR absorption spectrum of copper(I) chloride
    IR absorption spectrum of copper(I) chloride

References

External links

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