| Copper(ii) Chloride |
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Information AboutCopper(ii) Chloride |
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Copper(II) chloride is the higher Chloride of Copper , with the formula CuCl2. It occurs naturally as the mineral Eriochalcite . It is a yellow-brown solid which slowly absorbs moisture to form a blue-green di Hydrate . It is ionic and highly Soluble in water. Chemically it behaves as a weak Lewis Acid , and under certain conditions it can act as a mild Oxidising Agent . It has a crystal structure consisting of polymeric chains of flat CuCl4 units with opposite edges shared. It decomposes to CuCl and Cl2 at 1000 °C. CHEMICAL PROPERTIES Copper(II) chloride is an ionic compound which dissociates in aqueous solution, but coordination of chloride to Cu2+ does partially occur. This means that concentrated solutions of CuCl2 are green- a combination of the blue colour of {Link without Title} 2+ with the yellow or red colour of the halide complexes. CuCl2 also behaves as a mild Lewis Acid , for example in its reaction with HCl (or other Chloride sources) to form the complex ions CuCl3- and CuCl42-. Some of these complexes can be isolated as crystals from aqueous solution, and they form a wide variety structural types (Fig. 1). Copper(II) chloride also forms a rich variety of other Coordination Complexes with Ligand s such as Pyridine or Triphenylphosphine Oxide : :CuCl2 + 2 C5H5N → {Link without Title} (tetragonal) :CuCl2 + 2 (C6H5)3P=O → {Link without Title} (tetrahedral) However certain other ligands such as Phosphine s (e.g., Triphenylphosphine ) and even some tertiary Amines cause Reduction to copper(I) complexes. Reduction to Copper(I) Chloride can be effected simply by heating CuCl2 at high temperatures (about 1000 °C): :2 CuCl2( S ) → 2 CuCl ( S ) + Cl2 ( G ) However, it is generally more convenient to work in aqueous solution, and to use a reducing agent such as Sulfur Dioxide to make CuCl: :2 CuCl2( Aq ) + SO2 → 2 CuCl ( S ) + 2 HCl ( Aq ) + H2SO4 ( Aq ) CuCl2 can simply react as a source of Cu2+ in precipitation reactions for making insoluble copper(II) salts, for example copper(II) hydroxide, which can then decompose above 30 ° C to give Copper(II) Oxide : :CuCl2( Aq ) + 2 NaOH ( Aq ) → Cu(OH)2( S ) + 2 NaCl ( Aq ) Then Cu(OH)2( S ) → CuO ( S ) + 2 H2O ( L ) PREPARATION Copper(II) chloride is prepared by the action of Hydrochloric Acid on Copper(II) Oxide , copper(II) hydroxide or Copper(II) Carbonate , for example: : CuO ( S ) + 2 HCl ( Aq ) → CuCl2( Aq ) + H2O ( L ) Anhydrous CuCl2 may be prepared directly by union of the elements, Copper and Chlorine . CuCl2 may be purified by crystallisation from hot dilute Hydrochloric Acid , by cooling in a CaCl2 -ice bath {Link without Title} . CuCl2 is also produced when a penny is put in a quantity of household chlorine Bleach . Copper(II) chloride can be made through the electrolysis of brine, using copper wire for the anode and cathode. USES A major industrial application for copper(II) chloride is as a co-catalyst (along with Palladium(II) Chloride ) in the Wacker Process . In this process, Ethene (ethylene) is converted to Ethanal (acetaldehyde) using water and air. In the process PdCl2 is Reduced to Pd , and the CuCl2 serves to re-oxidise this back to PdCl2. Air can then oxidise the resultant CuCl back to CuCl2, completing the cycle. (1) C2H4 ( G ) + PdCl2 ( Aq ) + H2O ( L ) → CH3CHO (aq) + Pd ( S ) + 2 HCl (aq) (2) Pd (s) + 2 CuCl2(aq) → 2 CuCl (s) + PdCl2 (aq) (3) 2 CuCl (s) + 2 HCl (aq) + 1/2 O2 (g) → 2 CuCl2(aq) + H2O (l) Overall process: C2H4 (g) + 1/2 O2 (g) → CH3CHO (aq) Copper(II) chloride has a variety of applications in Organic Synthesis [7]. It can effect Chlorination of Aromatic Hydrocarbons - this is often performed in the presence of Aluminium Oxide . It is able to chlorinate the alpha position of Carbonyl compounds[8]: This reaction is performed in a polar solvent such as DMF , often in the presence of Lithium Chloride , which speeds up the reaction rate. CuCl2, in the presence of Oxygen , can also oxidise Phenols . The major product can be directed to give either a Quinone or a coupled product from oxidative dimerisation. The latter process provides a high-yield synthesis of 1,1-binaphthol (also called BINOL) and its derivatives, these can even be made as a single Enantiomer in high Enantiomeric Excess {Link without Title} : Such compounds are valuable intermediates in the synthesis of BINAP and its derivatives, popular as Chiral Ligand s for asymmetric Hydrogenation catalysts. CuCl2 also catalyses the Free Radical addition of Sulfonyl Chlorides to Alkene s; the alpha-chlorosulfone may then undergo Elimination with base to give a vinyl Sulfone product. Copper(II) chloride is also used in Pyrotechnics as a green colouring agent. PRECAUTIONS Copper salts are toxic, and can be fatal. Wear gloves and goggles, avoid ingestion or inhalation. SUPPLIERS/MANUFACTURERS REFERENCES # # ''Handbook of Chemistry and Physics'', 71st edition, CRC Press, Ann Arbor, Michigan, 1990. # ''The Merck Index'', 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960. # D. Nicholls, ''Complexes and First-Row Transition Elements'', Macmillan Press, London, 1973. # A. F. Wells, '''Structural Inorganic Chemistry'', 5th ed., Oxford University Press, Oxford, UK, 1984. # J. March, ''Advanced Organic Chemistry'', 4th ed., p. 723, Wiley, New York, 1992. # S. H. Bertz, E. H. Fairchild, 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. # C. E. Castro, E. J. Gaughan, D. C. Owsley, ''Journal of Organic Chemistry'', 30, 587 (1965). # J. Brussee, J. L. G. Groenendijk, J. M. Koppele, A. C. A. Jansen, ''Tetrahedron'', 41, 3313 (1985). # ''Fieser & Fieser Reagents for Organic Synthesis'' Volume 5, p158, Wiley, New York, 1975. EXTERNAL LINKS |
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