Cadmium chloride

Cadmium chloride is a white crystalline compound of cadmium and chlorine, with the formula CdCl2. It is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. Although it is considered to be ionic, it has considerable covalent character to its bonding. The crystal structure of cadmium chloride (described below), composed of two-dimensional layers of ions, is a reference for describing other crystal structures. Also known are CdCl2•H2O and CdCl2•5H2O.[2]

Cadmium chloride
Names
IUPAC name
Cadmium dichloride
Other names
Cadmium(II) chloride
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.030.256
EC Number
  • 233-296-7
RTECS number
  • EV0175000
UNII
UN number 2570
Properties
CdCl2
Molar mass 183.31 g·mol−1
Appearance White solid, hygroscopic
Odor Odorless
Density 4.047 g/cm3 (anhydrous)[1]
3.327 g/cm3 (Hemipentahydrate)[2]
Melting point 568 °C (1,054 °F; 841 K)
at 760 mmHg[2]
Boiling point 964 °C (1,767 °F; 1,237 K)
at 760 mmHg[2]
Hemipentahydrate:
79.5 g/100 mL (−10 °C)
90 g/100 mL (0 °C)
Monohydrate:
119.6 g/100 mL (25 °C)[2]
134.3 g/100 mL (40 °C)
134.2 g/100 mL (60 °C)
147 g/100 mL (100 °C)[3]
Solubility Soluble in alcohol, selenium(IV) oxychloride, benzonitrile
Insoluble in ether, acetone[1]
Solubility in pyridine 4.6 g/kg (0 °C)
7.9 g/kg (4 °C)
8.1 g/kg (15 °C)
6.7 g/kg (30 °C)
5 g/kg (100 °C)[1]
Solubility in ethanol 1.3 g/100 g (10 °C)
1.48 g/100 g (20 °C)
1.91 g/100 g (40 °C)
2.53 g/100 g (70 °C)[1]
Solubility in dimethyl sulfoxide 18 g/100 g (25 °C)[1]
Vapor pressure 0.01 kPa (471 °C)
0.1 kPa (541 °C)[2]
−6.87·10−5 cm3/mol[2]
Viscosity 2.31 cP (597 °C)
1.87 cP (687 °C)[1]
Structure
Rhombohedral, hR9 (anhydrous)[4]
Monoclinic (hemipentahydrate)[3]
R3m, No. 166 (anhydrous)[4]
3 2/m (anhydrous)[4]
a = 3.846 Å, c = 17.479 Å (anhydrous)[4]
α = 90°, β = 90°, γ = 120°
Thermochemistry
74.7 J/mol·K[2]
115.3 J/mol·K[2]
−391.5 kJ/mol[2]
−343.9 kJ/mol[2]
Hazards
Safety data sheet External MSDS
GHS pictograms [5]
GHS Signal word Danger
H301, H330, H340, H350, H360, H372, H410[5]
P210, P260, P273, P284, P301+310, P310[5]
NFPA 704 (fire diamond)
0
4
0
Lethal dose or concentration (LD, LC):
94 mg/kg (rats, oral)[1]
60 mg/kg (mouse, oral)
88 mg/kg (rat, oral)[6]
NIOSH (US health exposure limits):
PEL (Permissible)
[1910.1027] TWA 0.005 mg/m3 (as Cd)[7]
REL (Recommended)
Ca[7]
IDLH (Immediate danger)
Ca [9 mg/m3 (as Cd)][7]
Related compounds
Other anions
Cadmium fluoride
Cadmium bromide
Cadmium iodide
Other cations
Zinc chloride
Mercury(II) chloride
Calcium chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Structure

Cadmium chloride forms crystals with rhombohedral symmetry. Cadmium iodide, CdI2, has a very similar crystal structure to CdCl2. The individual layers in the two structures are identical, but in CdCl2 the chloride ions are arranged in a CCP lattice, whereas in CdI2 the iodide ions are arranged in an HCP lattice.[8][9]

Chemical properties

Cadmium chloride dissolves well in water and other polar solvents. In water, its high solubility is due in part to formation of complex ions such as [CdCl4]2−. Because of this behavior, CdCl2 is a mild Lewis acid.[8]

CdCl2 + 2 Cl → [CdCl4]2−

With large cations, it is possible to isolate the trigonal bipyramidal [CdCl5]3− ion.

Preparation

Anhydrous cadmium chloride can be prepared by the action of anhydrous chlorine or hydrogen chloride gas on heated cadmium metal.

Cd + 2 HCl → CdCl2 + H2

Hydrochloric acid may be used to make hydrated CdCl2 from the metal, or from cadmium oxide or cadmium carbonate.

Uses

Cadmium chloride is used for the preparation of cadmium sulfide, used as "Cadmium Yellow", a brilliant-yellow stable inorganic pigment.

CdCl
2
+ H
2
S
CdS + 2 HCl

In the laboratory, anhydrous CdCl2 can be used for the preparation of organocadmium compounds of the type R2Cd, where R is an aryl or a primary alkyl. These were once used in the synthesis of ketones from acyl chlorides:[10]

CdCl
2
+ 2 RMgX → R
2
Cd
+ MgCl
2
+ MgX
2
R
2
Cd
+ 2R'COCl → 2R'COR + CdCl
2

Such reagents have largely been supplanted by organocopper compounds, which are much less toxic.

Cadmium chloride is also used for photocopying, dyeing and electroplating.

References

  1. Anatolievich, Kiper Ruslan. "cadmium chloride". chemister.ru. Retrieved 2014-06-25.
  2. Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.
  3. Seidell, Atherton; Linke, William F. (1919). Solubilities of Inorganic and Organic Compounds (2nd ed.). New York: D. Van Nostrand Company. p. 169.
  4. "Cadmium Chloride - CdCl2". chem.uwimona.edu.jm. Mona, Jamaica: The University of the West Indies. Retrieved 2014-06-25.
  5. Sigma-Aldrich Co., Cadmium chloride. Retrieved on 2014-05-23.
  6. "Cadmium compounds (as Cd)". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  7. NIOSH Pocket Guide to Chemical Hazards. "#0087". National Institute for Occupational Safety and Health (NIOSH).
  8. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
  9. A. F. Wells, Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
  10. J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.
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