Methyldichloroarsine

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Methyldichloroarsine
Structural formula
Space-filling model
Names
Preferred IUPAC name
Methylarsonous dichloride
Identifiers
3D model (
JSmol
)
Abbreviations MD

MDA
MDCA

ChemSpider
MeSH Methyldichloroarsine
  • InChI=1S/CH3AsCl2/c1-2(3)4/h1H3 checkY
    Key: VXRMBBLRHSRVDK-UHFFFAOYSA-N checkY
  • InChI=1S/CH3AsCl2/c1-2(3)4/h1H3
    Key: VXRMBBLRHSRVDK-UHFFFAOYSA-N
  • InChI=1/CH3AsCl2/c1-2(3)4/h1H3
    Key: VXRMBBLRHSRVDK-UHFFFAOYAY
  • Cl[As](Cl)C
Properties
CH3AsCl2
Molar mass 160.86 g·mol−1
Appearance Colorless liquid
Density 1.836 g/cm3
Melting point −55 °C (−67 °F; 218 K)
Boiling point 133 °C (271 °F; 406 K)
reacts
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Highly toxic, Irritant
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Methyldichloroarsine, sometimes abbreviated "MD" and also known as methyl Dick,

vesicant that has been used in chemical warfare.[2]

History

German chemists weaponized methyldichloroarsine during

World War I, between 1917 and 1918. It was the first organoarsenic compound to be weaponized.[2]

Structure, synthesis, reactivity

Focusing on the arsenic center, the molecule geometry is trigonal pyramidal with the Cl-As-Cl and C-As-Cl angles approaching 90° (see image). Virtually all related arsenic(III) compounds adopt similar structures.

Methyldichloroarsine is produced by the reaction of methylmagnesium chloride and arsenic trichloride:[3]

AsCl3 + CH3MgCl → CH3AsCl2 + MgCl2

Typically such syntheses are conducted in ether or

THF solutions and typically the product is isolated by distillation. Use of larger amounts of the magnesium reagent affords greater amounts of dimethylchloroarsine ((CH3)2AsCl) and trimethylarsine
((CH3)3As).

In World War I, the German manufacturing method consisted of a three-step reaction beginning with methylation of sodium arsenite:

2 Na3AsO3 + (CH3O)2SO2 → 2 CH3AsO(ONa)2 + Na2SO4,

followed by reduction of the disodium monomethylarsonate with sulfur dioxide:

CH3AsO(ONa)2 + SO2 → CH3AsO + Na2SO4,

subsequently reacting the monomethylarsine oxide thus formed with hydrogen chloride to yield methyldichloroarsine:[4]

CH3AsO + 2 HCl → CH3AsCl2 + H2O

The As-Cl bonds in MD are susceptible toward

nucleophilic attack
. Reduction of MD with sodium metal affords the polymer [CH3As]n.

Use as a weapon

Symptoms of poisoning

Although some of its symptoms resemble those from

coughing, and shortness of breath with damage to the respiratory system can be delayed for about three to five days; hemolysis can also occur.[2]

MD is not persistent, meaning that it will dissipate after a short time.

LCt/50 for MD is about 3,000 mg/(min * m3).[5]

Protection

Besides avoiding situations in which it might be used, an

caustic soda.[5]

See also

References

  1. PMID 18015982
    .
  2. ^ a b c Fitzgerald GM, Vollmer T (2006-06-19). "CBRNE - Vesicants, Organic Arsenicals: L, ED, MD, PD, HL". WebMD. Retrieved 2008-12-23.
  3. ^
    ISBN 9781411694323
    .
  4. ^ Lohs KH (1974). Synthetische Gifte (in German) (4th ed.). Berlin (East), GDR: Militärverlag der Deutschen Demokratischen Republik.
  5. ^
    ISBN 9781420052664
    .
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