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.

References

1. Aldrich Handbook & Catalog of Fine Chemicals. Milwaukee, WI: Aldrich Chemical Company.   1994. p. 871. As cited in HSDB.
2. "SAFETY DATA SHEET Methylphosphonic dichloride". SAFETY DATA SHEET Methylphosphonic dichloride. MilliporeSigma. June 26, 2020. Retrieved April 27, 2022.
3. 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.
4. 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.
5. Carl Patois, Philippe Savignac, Elie About-Jaudet, Noël Collignon (1996). "Bis(Trifluoroethyl) (carboethoxymethyl)phosphonate". Organic Syntheses. 73: 152. doi:10.15227/orgsyn.073.0152.{{cite journal}}: CS1 maint: multiple names: authors list (link)