Copper (II) chloride

Crystal structure
__ Cu 2+      __ Cl -
Crystal system	monoclinic (CuCl 2 , anhydrous)
Space group	C 2 / m (No. 12)
Lattice parameters	a = 690 pm b = 330 pm; β = 122.20 ° c = 682 pm
Coordination numbers	Cu [6], Cl [3]
General
Surname	Copper (II) chloride
other names	Copper chloride Copper (II) chloride dihydrate (CuCl 2 2 H 2 O)
Ratio formula	CuCl 2 CuCl 2 2 H 2 O (dihydrate)
Brief description	yellow-brown powder blue powder (dihydrate)
External identifiers / databases
CAS number 7447-39-4 10125-13-0 (dihydrate) EC number 231-210-2 ECHA InfoCard 100.028.373 PubChem 24014 ChemSpider 22447 DrugBank DB09131 Wikidata Q421781
properties
Molar mass	134.45 g mol −1 170.48 g mol −1 (dihydrate)
Physical state	firmly
density	3.39 g cm −3
Melting point	630 ° C (anhydrous)
solubility	620 g l −1 (20 ° C) in water
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 302 + 312-315-318-410 P: 273-280-305 + 351 + 338
MAK	0.01 mg m −3
Toxicological data	584 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Copper (II) chloride is a chemical compound and a copper salt of hydrochloric acid with the formula CuCl ₂ . Anhydrous copper (II) chloride is a brown powder which is very hygroscopic . The incorporation of water molecules into its crystal structure creates the copper (II) chloride dihydrate , a blue-green solid with the formula CuCl ₂  · 2 H ₂ O. The anhydrous copper chloride melts in moist air to a brown paste, while the dihydrate is stable in air. The water of crystallization is expelled from the dihydrate by heating to over 100 ° C and the brown, anhydrous form remains.

There is also basic copper (II) chloride ( copper (II) oxychloride , Cu ₂ Cl (OH) ₃ ), which is insoluble in water and is referred to as a tetrahydrate as Braunschweig green .

In a burner flame , all compounds show a blue-green flame color , caused by the Cu ²⁺ ions.

Occurrence

Copper (II) chloride occurs naturally as the mineral tolbachite , the dihydrate is also known as the mineral eriochalcite . Both compounds are often associated with the copper ore atacamite .

Extraction and presentation

In the laboratory, copper (II) chloride can be produced from copper (II) oxide and hydrochloric acid or by dehydrating the dihydrate with thionyl chloride :

${\displaystyle \mathrm {CuO+2\ HCl\longrightarrow CuCl_{2}+\ H_{2}O} }$

${\displaystyle {\ce {CuCl2 * 2 H2O + 2 SOCl2 -> CuCl2 + 2 SO2 + 4 HCl}}}$

Technically, it is by chlorination of copper sheet obtained.

${\displaystyle \mathrm {Cu+Cl_{2}\longrightarrow CuCl_{2}} }$

Copper (II) chloride can also be produced by simple electrolysis of sodium chloride with copper electrodes. The resulting elemental chlorine oxidizes the copper electrodes. When the solution evaporates, copper (II) chloride dihydrate is formed.

properties

Copper (II) chloride (CuCl ₂ )

Copper (II) chloride dihydrate CuCl ₂ · 2 H ₂ O

Anhydrous copper (II) chloride occurs in the form of a brown to yellow powder; the dihydrate is turquoise. Both produce a green flame color due to the copper ions (Cu ²⁺ ) they contain .

The anhydrous copper (II) chloride crystallizes in the monoclinic crystal system with the space group C 2 / m (space group no. 12) in a distorted CdI ₂ - structure . The distortion of the structure is caused by the Jahn-Teller effect , which is caused by the valence electron configuration (d ⁹ ) of the Cu ²⁺ ions. The anhydrous copper (II) chloride was the first compound in which a coordination polyhedron in the form of a (distorted) octahedron of six chloride anions around a Cu ²⁺ ion could be detected.

The copper (II) chloride dihydrate, on the other hand, crystallizes in the orthorhombic crystal system in the space group Pbmn (No. 53, position 3) . The Cu ²⁺ ions are surrounded by four Cl ^- ions in a square-planar manner, the two remaining corners of the distorted octahedron are occupied by the water molecules.

use

Copper chloride is used as a catalyst in organic syntheses, e.g. B. used in the production of the textile dye aniline black and oxychlorination . It is also used in pyrotechnics to produce green flames, in copper etching (in a mixture with hydrochloric acid), in photography for bleaching negatives , as a basic copper chloride in fruit growing and viticulture against fungal diseases and for removing soot from oil stoves.

proof

Copper (II) chloride is detected with ammonia water. Blue copper (II) hydroxide precipitates out, which dissolves again as tetraammine copper upon further addition.

Individual evidence

1. ^ ^{A b} P. C. Burns, FC Hawthorne: Tolbachite, CuCl ₂ , the first example of Cu ²⁺ octahedrally coordinated by Cl ^- . In: American Mineralogist. No. 78, 1993, pp. 187-189.
2. ↑ ^{a b c d e f g h} Entry on copper (II) chloride in the GESTIS substance database of the IFA , accessed on April 1, 2016(JavaScript required) .
3. ↑ Data sheet copper (II) chloride (PDF) from Merck , accessed on January 19, 2011.
4. ^ Römpp: Basislexikon Chemie, Georg Thieme Verlag Stuttgart 1998, ISBN 3-13-115711-9
5. ^ Alfred R. Pray: Anhydrous metal chlorides . In: Therald Moeller (Ed.): Inorganic Syntheses . tape 5 . McGraw-Hill, Inc., 1957, pp. 153-156 (English).
6. ^ S. Brownstein, NF Han, EJ Gabe, Y. le Page: A redetermination of the crystal structure of cupric chloride dihydrate. In: Journal of Crystallography. No. 189, 1989, pp. 13-15.