Dimethyl methylphosphonate
Dimethyl methylphosphonate (DMMP) is an organophosphorus compound with the molecular formula C₃H₉O₃P and CAS Registry Number 756-79-6.[1] It appears as a colorless liquid at room temperature, with a density of approximately 1.145 g/mL and a flash point around 43°C, rendering it flammable under certain conditions.[2] Commercially, DMMP serves primarily as a flame retardant additive in formulations such as resins, latexes, coatings, and unsaturated polyesters, where its phosphorus content contributes to suppressing combustion by promoting char formation and radical scavenging in the gas phase.[3][4] In military and research applications, it functions as a non-toxic simulant for G-series nerve agents like sarin due to structural similarities, enabling safe testing of detection, decontamination, and protective equipment without the hazards of actual agents.[5] Additionally, studies have explored its incorporation into lithium-ion battery electrolytes to enhance fire safety by reducing flammability.[6] While generally considered of low acute toxicity compared to nerve agents, DMMP exhibits potential health effects including irritation and, in chronic exposure scenarios, organ toxicity as evidenced by National Toxicology Program studies in rodents.[7] Its environmental persistence and role in phosphorus-containing waste streams warrant consideration in disposal and regulatory contexts.[3]Properties
Physical properties
Dimethyl methylphosphonate (DMMP) is a colorless liquid at room temperature and standard pressure.[8] It has a melting point of −50 °C and a boiling point of 181 °C at 760 mmHg.[8] [9] The density is 1.16 g/cm³ at 20 °C or 1.145 g/mL at 25 °C.[8] [9] The refractive index is 1.41.[10] DMMP exhibits high solubility in water, exceeding 1000 g/L, rendering it miscible, and it is compatible with many organic solvents including alcohols.[11] [2] Its vapor pressure is less than 0.1 mmHg at 20 °C, indicating low volatility and limited tendency to evaporate under ambient conditions.[9] [4]| Property | Value | Conditions |
|---|---|---|
| Melting point | −50 °C | Standard pressure |
| Boiling point | 181 °C | 760 mmHg |
| Density | 1.16 g/cm³ | 20 °C |
| Vapor pressure | <0.1 mmHg | 20 °C |
Chemical properties
Dimethyl methylphosphonate (DMMP) has the molecular formula C₃H₉O₃P and structural formula CH₃P(O)(OCH₃)₂, featuring a central phosphorus(V) atom in tetrahedral geometry bonded to a methyl group (P-CH₃), a double-bonded oxygen (P=O), and two methoxy groups (P-OCH₃).[1][4]
As a dialkyl alkylphosphonate ester, DMMP displays reactivity characteristic of P-O-C linkages, undergoing hydrolysis under acidic or basic conditions to yield monomethyl methylphosphonate and methanol initially, with further hydrolysis producing methylphosphonic acid.[12] This ester functionality also enables participation in nucleophilic substitution reactions at phosphorus, such as transesterification or aminolysis, though slower than in phosphites due to the electron-withdrawing P=O group.
Spectroscopic characterization includes a characteristic ³¹P NMR chemical shift around 34 ppm in solution, serving as an intracellular-extracellular volume probe in biological systems owing to transmembrane shift differences.[13] Infrared spectra exhibit prominent bands for the P=O stretch near 1250 cm⁻¹ and P-O-C stretches between 1000 and 1100 cm⁻¹, aiding identification in vapor or adsorbed phases.[14]