title: Dimethylphosphine oxide
text: # Dimethylphosphine oxide
  
  Dimethylphosphine oxide is an organophosphorus compound with the formula $(CH_3)_2P(O)H.$ 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:
  
      $Me_2PCl$ + $H_2O$ → $Me_2P(O)H$ + 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:
  
      $(C_2H_5O)_2P(O)H$ + 3 $CH_3MgBr$ → $(CH_3)_2P(O)MgBr$ + 2 $MgBr(OC_2H_5)$ + $CH_4$
      $(CH_3)_2P(O)MgBr$ + $H_2O$ → $(CH_3)_2P(O)H$ + 2 MgBr(OH)
  
  ## Reactions
  
  Chlorination gives dimethylphosphoryl chloride. It undergoes hydroxymethylation with formaldehyde.
  
      $Me_2P(O)H$ + $CH_2O$ → $Me_2P(O)CH_2OH$
  
  Many aldehydes effect a similar reaction.
  
  