Trimethylarsine

Template:Chembox header | Trimethylarsine
Structural formula of trimethylarsine Ball-and-stick model of arsine
Template:Chembox header | General
Systematic name	Trimethylarsine
Other names	Gosio Gas
Molecular formula	C3H9As
Molar mass	120.02 g/mol
Appearance	Colorless liquid
CAS number	[593-88-4]
Template:Chembox header | Properties
Density and phase	1.124 g/cm³
Solubility in water	Slightly soluble
Other solvents	organic solvents
Melting point	-87.3 °C
Boiling point	51 °C
Template:Chembox header | Structure
geometry	Trigonal pyramidal
Dipole moment	0.86 D
Related compounds	Cacodylic acid Triphenylarsine
Template:Chembox header | Hazards
MSDS	External MSDS
Main hazards	Flammable
NFPA 704
Flash point	100 °C
R/S statement	R: ? S: ? See www.sigmaaldrich.com
RTECS number	CH8800000
Template:Chembox header | Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Template:Chembox header | Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Trimethylarsine is the chemical compound with the formula (CH₃)₃As, commonly abbreviated AsMe₃. This organic derivative of arsine (AsH₃) has been used as a source of arsenic in microelectronics industry. It is known for it's distinct "garlic" like smell. Trimethylarsine had been discovered as early as 1854.

Structure and Preparation

As predicted by VSEPR theory, AsMe₃ is pyramidal with As-C distance of 1.519 Å and C-As-C angles 91.83°

Trimethylarsine can be prepared by treatment of arsenic oxide with trimethylaluminium:

As₂O₃ + 3 AlMe₃ → 2 AsMe₃ + Me-(Al-O)_n

Properties and reactions

Trimethylarsine is pyrophoric due to the exothermic nature of the following reaction, which initiates combustion:

AsMe₃ + 1/2 O₂ → OAsMe₃ (TMAO)

History

Although poisoning events due to a gas produced by certain micobes was observed and the dependence to the arsenic in paint was assumed. It was not until 1893 that the Italian physician Bartolomeo Gosio published his results on the toxic "Gosio gas" which was subsequently shown to be trimethylarsine.. Under wet conditions mold (scopulariopsis brevicaulis was an very active species) produces significant amounts of arsenic via biomethylation of inorganic pigments especially Paris green or Scheele's Green used in indoor wallpapers which is than released into the air. Newer studies show that trimethylearsine has a low toxicity and could therefor not account for the death and the severe health problems observed in the 19th century.

Safety

Like all organoarsenic compounds, it is considered a carcinogen.

References

• Challenger, F.; et al. (1933). "The Formation of Organo-Metalloid Compounds by Microorganisms: Part I. Trimethylarsine and Dimethylethylarsine". J. Chem. Soc., 95-101, 1933.CS1 maint: Explicit use of et al. (link)
• Wells, A.F. (1984). Structural Inorganic Chemistry, fifth edition. Oxford University Press. ISBN-10: 0198553706. [1]
• Andrewes, Paul; et al. (2003). "Dimethylarsine and Trimethylarsine Are Potent Genotoxins In Vitro". Chem. Res. Toxicol., 16 (8), 994 -1003, 2003.CS1 maint: Explicit use of et al. (link)
• Irvin, T.Rick; et al. (1995). "In-vitro Prenatal Toxicity of Trimethylarsine, Trimethylarsine Oxide and Trimethylarsine Sulfide". Applied Organometallic Chemistry. vol. 9.315-321.CS1 maint: Explicit use of et al. (link)
• Sokolovskii, A.E. (2001). "Thermal Decomposition of Trimethylarsine". Kinetics and Catalysis, Vol 42, No. 6, 2001, pp. 743-745.
• Hoshino, Masataka (1991). "A mass spectrometric study of the decomposition of trimethylarsine (TMAs) with triethylgallium (TEGa)". Journal of Crystal Growth 110(1991)704-712.

External links

• Index by Molecular Formula
• Information on Hazardous Chemicals by Class
• "Highly efficient synthesis of trimethylarsine" E E Gavrilenko, L. A. ChekulaePa,* and L E Pisareva
• Microbial Methylation of Metalloids: Arsenic, Antimony, and Bismuth
• Arsenic Curiosa and Humanity