Arsenic trichloride
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Other names
Arsenic(III) chloride, Arsenous trichloride, Arsine trichloride, Butter of arsenic, de Valagin's solution, Trichloroarsine
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Identifiers | |
3D model (
JSmol ) |
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ChemSpider | |
ECHA InfoCard
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100.029.144 |
EC Number |
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PubChem CID
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RTECS number
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UNII | |
UN number | 1560 |
CompTox Dashboard (EPA)
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Properties | |
AsCl3 | |
Molar mass | 181.28 g/mol |
Appearance | colourless oily liquid |
Density | 2.163 g/cm3, liquid |
Melting point | −13 °C (9 °F; 260 K) |
Boiling point | 181 °C (358 °F; 454 K) |
Hydrolyzes | |
Solubility | soluble in alcohol, ether, HCl, HBr, chloroform, CCl4[1] |
-79.9·10−6 cm3/mol | |
Refractive index (nD)
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1.6006 |
Viscosity | 9.77 x 10−6 Pa s |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards
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Very toxic, carcinogen, corrosive, decomposes on contact with water releasing HCl |
GHS labelling: | |
Danger | |
H301, H310, H314, H331, H350, H410 | |
P201, P202, P260, P261, P262, P264, P270, P271, P273, P280, P281, P301+P310, P301+P330+P331, P302+P350, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P311, P321, P322, P330, P361, P363, P391, P403+P233, P405, P501 | |
NFPA 704 (fire diamond) | |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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48 mg/kg |
LCLo (lowest published)
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100 mg/m3 (cat, 1 hr) 200 mg/m3 (cat, 20 min) 338 ppm (rat, 10 min)[3] |
NIOSH (US health exposure limits): | |
PEL (Permissible)
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[1910.1018] TWA 0.010 mg/m3[2] |
REL (Recommended)
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Ca C 0.002 mg/m3 [15-minute][2] |
IDLH (Immediate danger) |
Ca [5 mg/m3 (as As)][2] |
Related compounds | |
Other anions
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Arsenic trioxide, Arsenic trifluoride |
Other cations
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Antimony trichloride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Arsenic trichloride is an
Structure
AsCl3 is a pyramidal molecule with C3v symmetry. The As-Cl bond is 2.161 Å and the angle Cl-As-Cl is 98° 25'±30.[5][6] AsCl3 has four normal modes of vibration: ν1(A1) 416, ν2(A1) 192, ν3 393, and ν4(E) 152 cm−1.[7]
Synthesis
This colourless liquid is prepared by treatment of arsenic(III) oxide with hydrogen chloride followed by distillation:
- As2O3 + 6 HCl → 2 AsCl3 + 3 H2O
It can also be prepared by chlorination of arsenic at 80–85 °C, but this method requires elemental arsenic.[4]
- 2 As + 3 Cl2 → 2 AsCl3
Arsenic trichloride can be prepared by the reaction of arsenic oxide and sulfur monochloride. This method requires simple apparatus and proceeds efficiently:[8]
- 2 As2O3 + 6 S2Cl2 → 4 AsCl3 + 3 SO2 + 9 S
A convenient laboratory method is refluxing arsenic(III) oxide with thionyl chloride:[9]
- 2 As2O3 + 3 SOCl2 → 2 AsCl3 + 3 SO2
Arsenic trichloride can also be prepared by the reaction of hydrochloric acid and arsenic(III) sulfide.
- As2S3 + 6 HCl → 2 AsCl3 + 3 H2S
Reactions
Hydrolysis gives arsenous acid and hydrochloric acid:
- AsCl3 + 3 H2O → As(OH)3 + 3 HCl
Although AsCl3 is less moisture sensitive than PCl3, it still fumes in moist air.[10]
AsCl3 undergoes redistribution upon treatment with As2O3 to give the inorganic polymer AsOCl. With chloride sources, AsCl3, forms salts containing the anion [AsCl4]−. Reaction with potassium bromide and potassium iodide give arsenic tribromide and arsenic triiodide, respectively.
AsCl3 is useful in organoarsenic chemistry, for example triphenylarsine is derived from AsCl3:[11]
- AsCl3 + 6 Na + C6H5Cl → As(C6H5)3 + 6 NaCl
The chemical weapons called Lewisites are prepared by the addition of arsenic trichloride to acetylene:
- AsCl3 + C2H2 → ClCH=CHAsCl2
Safety
Inorganic arsenic compounds are highly toxic,[4] and AsCl3 especially so because of its volatility and solubility (in water).
It is classified as an
References
- ISBN 978-1138561632.
- ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0038". National Institute for Occupational Safety and Health (NIOSH).
- ^ "Arsenic (inorganic compounds, as As)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
- ^
- ^ P. Kisliuk; C. H. Townes. "The Microwave Spectra and Molecular Structure of Phosphorus and Arsenic Trichloride". J. Chem. Phys. 1950, 18.
- ^ Klapoetke, Thomas M. "The vibrational spectrum of arsenic trichloride" Main Group Metal Chemistry 1997, volume 20, pp. 81–83.
- .
- ISBN 0-12-352651-5.
- ^ Shriner, R. L.; Wolf, C. N. (1963). "Tetraphenylarsonium Chloride Hydrochloride". Organic Syntheses; Collected Volumes, vol. 4, p. 910.. Describes the preparation of As(C6H5)3.
- ^ 40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities (PDF) (Report) (July 1, 2008 ed.). Government Printing Office. Archived from the original (PDF) on February 25, 2012. Retrieved October 29, 2011.