Dimethylphosphine oxide is an

organophosphorus compound Organophosphorus compounds are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective in ...

with the formula (CH₃)₂P(O)H. It is a colorless liquid that soluble in polar organic solvents. It exists as the phosphine oxide, not the hydroxy

tautomer Tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert. The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the relocation of a hydr ...

. A related compound is

diphenylphosphine oxide Diphenylphosphine oxide is an organophosphorus compound with the formula (C6H5)2P(O)H. It is a white solid that soluble in polar organic solvents. Synthesis Diphenylphosphine oxide can be prepared by the reaction of phosphonic esters, such as d ...

. Both are sometimes called secondary phosphine oxides.

Preparation

The compound arises by the hydrolysis of chlorodimethylphosphine: :Me₂PCl + H₂O → Me₂P(O)H + HCl Methanol, but not ethanol, can also be used in place of water, the co-product being

methyl chloride Chloromethane, also called methyl chloride, Refrigerant-40, R-40 or HCC 40, is an organic compound with the chemical formula . One of the haloalkanes, it is a colorless, odorless, flammable gas. Methyl chloride is a crucial reagent in industrial ...

. Since chlorodimethylphosphine is dangerous to handle, alternative routes to dimethylphosphine oxide have been developed. A popular method starts with

diethylphosphite Diethylphosphite is the organophosphorus compound with the formula (C2H5O)2P(O)H. It is a popular reagent for generating other organophosphorus compounds, exploiting the high reactivity of the P-H bond. Diethylphosphite is a colorless liquid. The ...

, according to the following idealized equations:{{cite journal, author=Hays, H. R., title=Reaction of diethyl phosphonate with methyl and ethyl Grignard reagents, journal=J. Org. Chem., year=1968, volume=33, pages=3690-3694, doi=10.1021/jo01274a003 :(C₂H₅O)₂P(O)H + 3 CH₃MgBr → (CH₃)₂P(O)MgBr + 2 MgBr(OC₂H₅) + CH₄ :(CH₃)₂P(O)MgBr + H₂O → (CH₃)₂P(O)H + 2 MgBr(OH)

Reactions

Chlorination gives dimethylphosphoryl chloride. It undergoes hydroxymethylation with formaldehyde. :Me₂P(O)H + CH₂O → Me₂P(O)CH₂OH Many aldehydes effect a similar reaction.

References

Organophosphine oxides