Cadmium chloride

Cadmium chloride
Ball-and-stick model of cadmium chloride	Cadmium chloride in polyhedron shape
Names
	IUPAC name Cadmium dichloride
	Other names Cadmium(II) chloride
Identifiers
CAS Number	10108-64-2 ; (hemipentahydrate): 7790-78-5 ; (monohydrate): 35658-65-2;
3D model (JSmol)	Interactive image; (hemipentahydrate): Interactive image; (monohydrate): Interactive image;
Beilstein Reference	3902835
ChEBI	CHEBI:35456 ;
ChemSpider	23035 ; (hemipentahydrate): 17339510; (monohydrate): 4447434;
ECHA InfoCard	100.030.256
EC Number	233-296-7; (hemipentahydrate): 813-696-3;
Gmelin Reference	912918
KEGG	C15233;
PubChem CID	24947; (hemipentahydrate): 24978551; (monohydrate): 5284356;
RTECS number	EV0175000;
UNII	J6K4F9V3BA ; (hemipentahydrate): 2R707SXC9H ;
UN number	2570
CompTox Dashboard (EPA)	DTXSID6020226 ; (hemipentahydrate): DTXSID4040183;
	InChI InChI=1S/Cd.2ClH/h;21H/q+2;;/p-2 Key: YKYOUMDCQGMQQO-UHFFFAOYSA-L ; InChI=1/Cd.2ClH/h;21H/q+2;;/p-2 Key: YKYOUMDCQGMQQO-NUQVWONBAG; (hemipentahydrate): InChI=1S/2Cd.4ClH.5H2O/h;;41H;51H2/q2+2;;;;;;;;;/p-4 Key: DZVRGWYMCGLNKJ-UHFFFAOYSA-J; (monohydrate): InChI=1S/Cd.2ClH.H2O/h;21H;1H2/q+2;;;/p-2 Key: OISMQLUZKQIKII-UHFFFAOYSA-L;
	SMILES [Cd+2].[Cl-].[Cl-]; (hemipentahydrate): O.O.O.O.O.[Cl-].[Cl-].[Cl-].[Cl-].[Cd+2].[Cd+2]; (monohydrate): O.[Cl-].[Cl-].[Cd+2];
Properties
Chemical formula	CdCl2
Molar mass	183.31 g·mol−1
Appearance	White solid, hygroscopic
Odor	Odorless
Density	4.047 g/cm3 (anhydrous); 3.26 g/cm3 (monohydrate) ; 3.327 g/cm3 (Hemipentahydrate)
Melting point	568 °C (1,054 °F; 841 K)
Boiling point	964 °C (1,767 °F; 1,237 K)
Solubility in water	Hemipentahydrate:; 79.5 g/100 mL (−10 °C); 90 g/100 mL (0 °C); Monohydrate:; 119.6 g/100 mL (25 °C); 134.3 g/100 mL (40 °C); 134.2 g/100 mL (60 °C); 147 g/100 mL (100 °C)
Solubility	Soluble in alcohol, selenium(IV) oxychloride, benzonitrile; Insoluble in ether, acetone
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)
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)
Solubility in dimethyl sulfoxide	18 g/100 g (25 °C)
Vapor pressure	0.01 kPa (471 °C); 0.1 kPa (541 °C)
Magnetic susceptibility (χ)	−6.87·10−5 cm3/mol
Viscosity	2.31 cP (597 °C); 1.87 cP (687 °C)
Structure
Crystal structure	Rhombohedral, hR9 (anhydrous); Monoclinic (hemipentahydrate)
Space group	R3m, No. 166 (anhydrous)
Point group	3 2/m (anhydrous)
Lattice constant	a = 3.846 Å, c = 17.479 Å (anhydrous) α = 90°, β = 90°, γ = 120°
Thermochemistry
Heat capacity (C)	74.7 J/mol·K
Std molar; entropy (S⦵298)	115.3 J/mol·K
Std enthalpy of; formation (ΔfH⦵298)	−391.5 kJ/mol
Gibbs free energy (ΔfG⦵)	−343.9 kJ/mol
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H330, H340, H350, H360, H372, H410
Precautionary statements	P210, P260, P273, P284, P301+P310, P310
NFPA 704 (fire diamond)	4 0 0
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	94 mg/kg (rats, oral); 60 mg/kg (mouse, oral); 88 mg/kg (rat, oral)
	NIOSH (US health exposure limits):
PEL (Permissible)	[1910.1027] TWA 0.005 mg/m3 (as Cd)
REL (Recommended)	Ca
IDLH (Immediate danger)	Ca [9 mg/m3 (as Cd)]
Safety data sheet (SDS)	External MSDS
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). verify (what is ?) Infobox references

Cadmium chloride is a white crystalline compound of cadmium and chloride, with the formula CdCl₂. This salt is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. The crystal structure of cadmium chloride (described below), is a reference for describing other crystal structures. Also known are CdCl₂•H₂O and the hemipentahydrate CdCl₂•2.5H₂O.^[2]

Structure

Anhydrous

Anhydrous cadmium chloride forms a layered structure consisting of octahedral Cd²⁺ centers linked with chloride ligands. Cadmium iodide, CdI₂, has a similar structure, but the iodide ions are arranged in a HCP lattice, whereas in CdCl₂ the chloride ions are arranged in a CCP lattice.^[8]^[9]

Hydrates

The anhydrous form absorbs moisture from the air to form various hydrates. Three of these hydrates have been examined by X-ray crystallography.

Crystallographic data for the 3 hydrates of cadmium chloride
Compound	CdCl₂·H₂O^[10]	CdCl₂·2.5H₂O^[11]	CdCl₂·4H₂O^[12]
Molar mass (g/mol)	201.33	228.36	255.38
Crystal Structure	Orthorhombic	Monoclinic	Orthorhombic
Space Group	Pnma	P2₁/n	P2₁2₁2₁
Lattice constant a (Å)	9.25	9.21	12.89
Lattice constant b (Å)	3.78	11.88	7.28
Lattice constant c (Å)	11.89	10.08	15.01
β		93.5°
Density (g/cm³)	3.26	2.84	2.41
Comment	Interconnected CdCl₃(H₂O) octahederons		Distorted trans-[CdCl₂(H₂O)₄] octahedrons

Chemical properties

Cadmium chloride dissolves well in water and other polar solvents. It is a mild Lewis acid.^[8]

CdCl₂ + 2 Cl⁻ → [CdCl₄]²⁻

Solutions of equimolar cadmium chloride and potassium chloride give potassium cadmium trichloride.^[13] With large cations, it is possible to isolate the trigonal bipyramidal [CdCl₅]³⁻ ion.

Cadmium metal is soluble in molten cadmium chloride, produced by heating cadmium chloride above 568 °C. Upon cooling, the metal precipitates.^[14]

Preparation

Anhydrous cadmium chloride can be prepared by the reaction of hydrochloric acid and cadmium metal or cadmium oxide.^[14]

Cd + 2 HCl → CdCl₂ + H₂

The anhydrous salt can also be prepared from anhydrous cadmium acetate using hydrogen chloride or acetyl chloride.^[15]

Industrially, it is produced by the reaction of molten cadmium and chlorine gas at 600 °C.^[14]

The monohydrate, hemipentahydrate, and tetrahydrate can be produced by evaporation of the solution of cadmium chloride at 35, 20, and 0 °C respectively. The hemipentahydrate and tetrahydrate release water in air.^[10]^[11]^[12]

Uses

Cadmium chloride is used for the preparation of cadmium sulfide, used as "cadmium yellow", a brilliant-yellow stable inorganic pigment.^[14]

CdCl
₂ + H
₂S → 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:^[16]

CdCl
₂ + 2 RMgX → R
₂Cd + MgCl
₂ + MgX
₂

R
₂Cd + 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.

Like all cadmium compounds, CdCl
₂ is highly toxic and appropriate safety precautions must be taken when handling it.

References

^ ^a ^b ^c ^d ^e ^f ^g Anatolievich, Kiper Ruslan. "cadmium chloride". chemister.ru. Retrieved 2014-06-25.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.
^ ^a ^b Seidell, Atherton; Linke, William F. (1919). Solubilities of Inorganic and Organic Compounds (2nd ed.). New York: D. Van Nostrand Company. p. 169.
^ ^a ^b ^c ^d "Cadmium Chloride - CdCl2". chem.uwimona.edu.jm. Mona, Jamaica: The University of the West Indies. Retrieved 2014-06-25.
^ ^a ^b ^c Sigma-Aldrich Co., Cadmium chloride. Retrieved on 2014-05-23.
^ ^a ^b ^c NIOSH Pocket Guide to Chemical Hazards. "#0087". National Institute for Occupational Safety and Health (NIOSH).
^ "Cadmium compounds (as Cd)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
^ ^a ^b N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
^ A. F. Wells, Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
^ ^a ^b H. Leligny; J. C. Monier (1974). "Structure cristalline de CdCl2.H2O" [Crystal structure of CdCl2.H2O]. Acta Crystallographica B (in French). 30 (2): 305–309. doi:10.1107/S056774087400272X.
^ ^a ^b H. Leligny; J. C. Monier (1975). "Structure de CdCl2.2,5H2O" [Structure of CdCl2.2,5H2O]. Acta Crystallographica B (in French). 31 (3): 728–732. doi:10.1107/S056774087500369X.
^ ^a ^b H. Leligny; J. C. Monier (1979). "Structure de dichlorure de cadmium tétrahydraté" [Structure of cadmium dichloride tetrahydrate]. Acta Crystallographica B (in French). 35 (3): 569–573. doi:10.1107/S0567740879004179.
^ F. Wagenknecht; R. Juza (1963). "Potassium cadmium chloride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. p. 1095.
^ ^a ^b ^c ^d Karl-Heinz Schulte-Schrepping; Magnus Piscator (2000). "Cadmium and Cadmium Compounds". Ullmann's Encyclopedia of Industrial Chemistry (6th ed.). p. 472. doi:10.1002/14356007.a04_499. ISBN 9783527306732.
^ F. Wagenknecht; R. Juza (1963). "Cadmium chloride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. pp. 1093–4.
^ J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.