Dimethylphosphine oxide

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:
 * Me2PCl +  H2O  →   Me2P(O)H  +  HCl

Methanol, 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:
 * (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.