Dimethylphosphine oxide is an organophosphorus compound 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. A related compound is diphenylphosphine oxide. Both are sometimes called secondary phosphine oxides.
Preparation
The compound arises by the hydrolysis of chlorodimethylphosphine:1
Me2PCl + H2O → Me2P(O)H + HClMethanol, but not ethanol, can also be used in place of water, the co-product being methyl chloride.
Since chlorodimethylphosphine is dangerous to handle, alternative routes to dimethylphosphine oxide have been developed. A popular method starts with diethylphosphite, according to the following idealized equations:2
(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)CH2OHMany aldehydes effect a similar reaction.
References
Kleiner, H. J. (1974). "Herstellung und Umsetzungen von Dimethylphosphinoxid (Preparation and Reactions of Dimethylphosphine Oxide)". Justus Liebigs Ann. Chem.: 751–764. doi:10.1002/jlac.197419740507. /wiki/Doi_(identifier) ↩
Hays, H. R. (1968). "Reaction of diethyl phosphonate with methyl and ethyl Grignard reagents". J. Org. Chem. 33: 3690–3694. doi:10.1021/jo01274a003. /wiki/Doi_(identifier) ↩