Dimethyl hydrogen phosphite (DMHP), also known as Dimethylphosphite, 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 (CH3O)2P(O)H. It is a reagent for generating other organophosphorus compounds, exploiting the high reactivity of the P-H bond. The molecule is
tetrahedral
In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the o ...
. It is a colorless liquid. The compounds can be prepared by methanolysis of
phosphorus trichloride
Phosphorus trichloride is an inorganic compound with the chemical formula PCl3. A colorless liquid when pure, it is an important industrial chemical, being used for the manufacture of phosphites and other organophosphorus compounds. It is toxic a ...
or by heating
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 ...
in methanol.
Due to the presence of hydrogen, a "soft" ligand, the compound resonates. DMHP exists in chemical equilibrium, in two structures. One of the structures has a lone electron cloud, which is nucleophilically attacking the remaining tetrahedral structure. Due to the structural equilibrium tending towards the
phosphonate
In organic chemistry, phosphonates or phosphonic acids are organophosphorus compounds containing groups (where R = alkyl, aryl, or just hydrogen). Phosphonic acids, typically handled as salts, are generally nonvolatile solids that are poorly ...
, this reaction is slow, needing a chemical or electromagnetic catalyst (heat).
This tautomeric nature of DMHP made it desirable as a precursor to the G-series compounds, and it was the most successful among all other phosphonate precursors. The now obsolete process, which used it as a precursor, was called the DMHP process, investigated by
Otto Ambros
Otto Ambros (19 May 1901 – 23 July 1990) was a German chemist and Nazi war criminal. He is known for his wartime work on synthetic rubber (polybutadiene, or "Buna rubber") and nerve agents (sarin and tabun). After the war he was tried at Nure ...
' team and implemented to scale
sarin
Sarin (NATO designation GB G-series, "B"">Nerve_agent#G-series.html" ;"title="hort for Nerve agent#G-series">G-series, "B" is an extremely toxic synthetic organophosphorus compound.Organophosphites