Methyldichlorophosphine

Methyldichlorophosphine (alternatively known as dichloro(methyl)phosphane, SW and methylphosphonous dichloride) is an organophosphorus compound with the chemical formula CH₃PCl₂. It is a colorless, corrosive, flammable, and highly reactive liquid with a pungent odor.

Methyldichlorophosphine

Names
Preferred IUPAC name Methylphosphonous dichloride
Other names Methyl phosphonous dichloride, Dichloromethylphosphine, SW[1]
Identifiers
CAS Number	676-83-5
3D model (JSmol)	Interactive image
ChemSpider	55138
ECHA InfoCard	100.010.575
EC Number	211-631-8
PubChem CID	61194
UN number	2845
CompTox Dashboard (EPA)	DTXSID1060978
InChI InChI=1S/CH3Cl2P/c1-4(2)3/h1H3 Key: CDPKWOKGVUHZFR-UHFFFAOYSA-N
SMILES CP(Cl)Cl
Properties
Chemical formula	CH3Cl2P
Molar mass	116.91 g·mol−1
Appearance	Colorless liquid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

Methyldichlorophosphine is produced by alkylation of phosphorus trichloride with methyl iodide followed by reduction of the resulting phosphonium salt with iron powder:^[2][3]

CH₃I + PCl₃ + AlCl₃ → [CH₃PCl₃]⁺AlCl₃I⁻

[CH₃PCl₃]⁺AlCl₃I⁻ + Fe → CH₃PCl₂ + FeICl + AlCl₃

The compound is an intermediate for the synthesis of other chemicals for instance dimethylphenylphosphine.

Uses

Methyldichlorophosphine belongs to the group of halophosphines, some of which are used as intermediates in the production of plant protection agents, stabilizers for plastics, and catalysts. It is a precursor of the herbicide Glufosinate. It is also used in the production of flameproofing compounds.^[4]

Due to the recycling problem of phosphoryl chloride, SW was adopted in step three of the DMHP process in the preparation of Sarin.^[5] SW was also adopted as a standard precursor to V agents, having been used to prepare QL for unitary and binary VX. SW was the first agent adopted to prepare VX in one pot reaction by aqueous medium.^[6]

Safety

It is also toxic if inhaled, can cause burns upon contact with the skin and eyes, and releases fumes of hydrochloric acid in moist environments.^[7]