Methylphosphonic acid dichloride

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Methylphosphonic acid dichloride
Methyl phosphonic dichloride.svg
CAS number 676-97-1
PubChem 12671
ChemSpider 12150
EC number 211-634-4
Jmol-3D images Image 1
Molecular formula CH3Cl2OP
Molar mass 132.91 g mol−1
Appearance White crystalline solid
Density 1.468 g/mL at 20 °C
Melting point 28-34°C
Boiling point 163°C
R-phrases R14, R23/24/25, R26, R34
Main hazards Very Toxic
Flash point >110°C
LD50 26 ppm/4h by inhalation (rat)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Methyl phosphonic dichloride is an organophosphorus compound. It has a number of potential uses but is most notable as being a precursor to several chemical weapons agents. It is a white crystalline solid, with a low melting point. It hydrolyzes readily and must be handled with care as it is exceedingly toxic.

Synthesis and reactions[edit]

Methyl phosphonic dichloride is produced by oxidation of methyldichlorophosphine, e.g. with sulfuryl chloride:[1]

MePCl2 + SO2Cl2 → MeP(O)Cl2 + SOCl2

It can also be produced from a range of methyl-phosphonates (e.g. dimethyl methylphosphonate) via chlorination with thionyl chloride. Various amines can be used to catalyse this process.[2] It reacts with hydrogen fluoride or sodium fluoride to produce methylphosphonyl difluoride, which is used in the production of sarin and soman nerve agents.


  1. ^ Svara, J.; Weferling, N.; Hofmann, T. "Phosphorus Compounds, Organic," In 'Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2008. doi:10.1002/14356007.a19_545.pub2.
  2. ^ Maier, Ludwig (1990). "ORGANIC PHOSPHORUS COMPOUNDS 90.l A CONVENIENT, ONE-STEP SYNTHESIS OF ALKYL- AND ARYLPHOSPHONYL DICHLORIDES". Phosphorus, Sulfur, and Silicon and the Related Elements 47 (3-4): 465–470. doi:10.1080/10426509008038002.