Methylphosphonyl dichloride

Methylphosphonyl dichloride (DC) or dichloro is an organophosphorus compound. It has commercial application in oligonucleotide synthesis,^[1] but is most notable as being a precursor to several chemical weapons agents. It is a white crystalline solid that melts slightly above room temperature.^[2]

Methylphosphonyl dichloride

Names
Preferred IUPAC name Methylphosphonic dichloride
Other names Methanephosphonic dichloride Methanephosphonic acid dichloride Methylphosphonyl dichloride Dichloro
Identifiers
CAS Number	676-97-1
3D model (JSmol)	Interactive image
ChemSpider	12150
ECHA InfoCard	100.010.578
EC Number	211-634-4
PubChem CID	12671
UN number	9206
CompTox Dashboard (EPA)	DTXSID6060979
InChI InChI=1S/CH3Cl2OP/c1-5(2,3)4/h1H3 Key: SCLFRABIDYGTAZ-UHFFFAOYSA-N InChI=1/CH3Cl2OP/c1-5(2,3)4/h1H3 Key: SCLFRABIDYGTAZ-UHFFFAOYAS
SMILES CP(=O)(Cl)Cl
Properties
Chemical formula	CH3Cl2OP
Molar mass	132.91 g·mol−1
Appearance	White crystalline solid
Density	1.468 g/mL at 20 °C
Melting point	28 to 34 °C (82 to 93 °F; 301 to 307 K)
Boiling point	163 °C (325 °F; 436 K)
Solubility in water	Reacts with water
Solubility	Ether, THF
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Very toxic, reacts with water
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H330
Precautionary statements	P260, P264, P271, P280, P284, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P320, P321, P363, P403+P233, P405, P501
Flash point	>110 °C
Lethal dose or concentration (LD, LC):
LD50 (median dose)	26 ppm/4h by inhalation (rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis and reactions

Methylphosphonyl dichloride is produced by oxidation of methyldichlorophosphine, with sulfuryl chloride:^[3]

CH₃PCl₂ + SO₂Cl₂ → CH₃P(O)Cl₂ + SOCl₂

It can also be produced from a range of methylphosphonates (e.g. dimethyl methylphosphonate) via chlorination with thionyl chloride. Various amines catalyse this process.^[4] With hydrogen fluoride or sodium fluoride, it can be used to produce methylphosphonyl difluoride. With alcohols, it converts to the dialkoxide:^[5]

CH₃P(O)Cl₂ + 2 HOR → CH₃P(O)(OR)₂ +  HCl

Safety

Methylphosphonyl dichloride is very toxic and reacts vigorously with water to release hydrochloric acid. It is also listed under Schedule 2 of the Chemical Weapons Convention as it is used in the production of organophosphorus nerve agents such as sarin and soman.