Methylphosphinic acid is a monobasic acid, the simplest of the phosphinic acids. A central phosphorus atom is connected to a hydroxy group, a hydrogen atom, a methyl group and an oxygen. Derivatives of methylphosphinic acid can have the phosphorus connected hydrogen atom replaced by other organic groups. In early days what is now called methylphosphonic acid was also called methylphosphinic acid.
Methylphosphinic acid can be produced by the hydrolysis of dimethyl methylphosphonate, which is conveniently obtained from trimethylphosphite.
Hydrolysis of methyldichlorophosphine yields methylphosphinic acid,
Methylphosphinic acid is a common byproduct of the hydrolysis of various CH<sub>3</sub>P-containing esters and amides, as occur in pesticides for example.
Rat oral value for methylphosphinic acid is 940 mg/kg.