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Copper(I) chloride

2007 Schools Wikipedia Selection. Related subjects: Chemical compounds

                                Copper(I) chloride
                               Copper(I) chloride
                                     General
          Systematic name                                     Copper(I) chloride
              Other names                                       Cuprous chloride
        Molecular formula                                                   CuCl
               Molar mass                                            98.99 g/mol
               Appearance                                 white powder, slightly
                                                            green from oxidation
               CAS number                                            [7758-89-6]
                                    Properties
        Density and phase                                    4.140 g/cm^3, solid
      Solubility in water                                0.0062 g/100 ml (20 °C)
               in ethanol                                              insoluble
     in hydrochloric acid
         in diethyl ether
       in aqueous ammonia                                                soluble
            Melting point                                         430 °C (703 K)
            Boiling point                                     1490 °C (1760 K),
                                                                      decomposes
                                    Structure
        Crystal structure                               Tetrahedral close packed
                                                        ( Zinc blende structure)
            Dipole moment                                                    ? D
                                     Hazards
                     MSDS                                          External MSDS
             Main hazards                                               Irritant
                 NFPA 704 Image:nfpa_h3.png Image:nfpa_f0.png Image:nfpa_r0.png
              Flash point                                                    n/a
            R/S statement                             R: 22, 50, 53 S: 22, 60/61
             RTECS number                                              GL6990000
                             Supplementary data page
   Structure & properties                                          n, ε[r], etc.
       Thermodynamic data                                        Phase behaviour
                                                              Solid, liquid, gas
            Spectral data                                        UV, IR, NMR, MS
                                Related compounds
             Other anions                                      Copper(I) bromide
                                                                Copper(I) iodide
            Other cations                                    Copper(II) chloride
                                                              Silver(I) chloride
                 Except where noted otherwise, data are given for
                          materials in their standard state (at 25°C, 100 kPa)
                                              Infobox disclaimer and references

   Copper(I) chloride (quite commonly called cuprous chloride), is the
   lower chloride of copper, with the formula CuCl. It occurs naturally as
   the mineral nantokite. It is a white solid which is almost insoluble in
   water, and which tends to oxidise in air to green CuCl[2]. It is a
   Lewis acid which reacts with suitable ligands such as ammonia or
   chloride ion to form complexes, many of which are water-soluble. It is
   even able to form a stable complex with carbon monoxide.

   In aqueous solution, CuCl would be unstable with respect to
   disproportionation into Cu and CuCl[2], but its low solubility allows
   it to be a stable compound^.

Chemical Properties

   Copper(I) chloride is a Lewis acid, 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 + PPh[3] → [CuCl(PPh[3])][4] (Ph = phenyl)

   Although CuCl is insoluble in water, it dissolves in aqueous solutions
   containing suitable donor molecules. It readily forms complexes with
   halide ions, for example forming H[3]O^+ CuCl[2]^- with concentrated
   hydrochloric acid. It also dissolves readily in solutions containing
   CN^-, S[2]O[3]^2- or NH[3]

   Solutions of CuCl in HCl or NH[3] absorb carbon monoxide to form
   colourless complexes such as the crystalline halogen-bridged dimer
   [CuCl(CO)][2]. The same HCl solution can also react with acetylene gas
   to form [CuCl(C[2]H[2])], while an NH[3] solution of CuCl forms an
   explosive acetylide with acetylene. Complexes of CuCl with alkenes can
   be made by reduction of CuCl[2] by sulfur dioxide in the presence of
   the alkene in alcohol solution. Complexes with chelating alkenes such
   as 1,5-cyclooctadiene are particularly stable^:

   Structure of COD complex of CuCl

   CuCl reacts with organometallic compounds such as methyllithium
   (CH[3]Li) to form "Gilman reagents" such as (CH[3])[2]CuLi, which find
   extensive use in organic synthesis. Grignard reagents react similarly.

Preparation

   Copper(I) chloride may be prepared by the reduction of copper(II) salts
   such as CuSO[4] using sulfur dioxide or copper metal. SO[2] may be
   prepared in situ from sodium bisulfite (NaHSO[3]) or sodium
   metabisulfite (Na[2]S[2]O[5]) and acid. The reduction is carried out in
   hydrochloric acid, and the resulting CuCl[2]^- complex is diluted to
   precipitate white CuCl (by driving the equilibrium using Le Chatelier's
   principle).

   (1) NaHSO[3]( aq) + HCl ( aq) → SO[2]( aq) + NaCl + H[2]O( l)

   (2) 2 CuSO[4]( aq) + SO[2]( aq) + 2 H[2]O( l) + 4 HCl( aq) → 2
   HCuCl[2]( aq) + 3 H[2]SO[4]( aq)

   (3) HCuCl[2]( aq) + H[2]O( l) → CuCl( s) + H[3]O^+( aq) + Cl^-( aq)

Uses

   A major chemical use for copper(I) chloride is as a catalyst for a
   variety of organic reactions. Compared to other "soft" Lewis acids, it
   is much more affordable than non-toxic silver(I) chloride and
   palladium(II) chloride, and much less toxic than lead(II) chloride and
   mercury(II) chloride. In addition, it can undergo redox chemistry via
   copper(II) or copper(III) intermediates. This combination of properties
   make copper(I) salts invaluable reagents.

   One such application is in the Sandmeyer reaction^. Treatment of an
   arenediazonium salt with CuCl leads to an aryl chloride, for example:

   (Example Sandmeyer reaction using CuCl)

   The reaction has wide scope, and usually gives good yields.

   The observation 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 ^:

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

   Although other copper(I) compounds such as copper(I) iodide are now
   more often used for this type of reaction, there are cases where
   copper(I) chloride is particularly effective^:

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

   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 closer to the C=O).

   Copper(I) chloride is also an intermediate formed from copper(II)
   chloride in the Wacker process.

Precautions

   Copper salts do have some toxicity and should be handled with care;
   wear gloves and goggles. Avoid bringing CuCl into contact with alkynes.

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