Dimethylphosphite

{{Chembox

| ImageFile = Dimethylphosphite.svg

| PIN = Dimethyl phosphonate

| OtherNames = Phosphonic acid, dimethyl ester

|Section1={{Chembox Identifiers

| CASNo = 868-85-9

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = ST4TBO000H

| PubChem = 94853

| ChEMBL = 65359

| ChemSpiderID = 85582

| InChI = 1S/C2H7O3P/c1-4-6(3)5-2/h3H,1-2H3

| InChIKey = DLQDGVZAEYZNTG-UHFFFAOYSA-N

| SMILES = COP(O)OC

}}

|Section2={{Chembox Properties

| C=2|H=7|O=3|P=1

| Appearance = colorless liquid

| Density = 1.20 g/cm³

| BoilingPtC = 72-73

| BoilingPt_notes = 25 Torr

}}

}}

Dimethylphosphite is an organophosphorus compound with the formula (CH₃O)₂P(O)H, known as dimethyl hydrogen phosphite (DMHP). Dimethylphosphite, is a minor tautomer of the phosphorus(V) derivative. It is a reagent for generating other organophosphorus compounds, exploiting the high reactivity of the P-H bond. The molecule is tetrahedral. It is a colorless liquid. The compounds can be prepared by methanolysis of phosphorus trichloride or by heating diethylphosphite in methanol.{{cite journal|title=Alcoholysis of Dialkyl Phosphites Under Microwave Conditions|author1=Balint, Erika |author2=Tajti, Adam |author3=Drahos, Laszlo |author4=Ilia, Gheorge |author5=Keglevich, Gyorgy |journal=Current Organic Chemistry|volume=17|year=2013|issue= 5|pages=555–562|doi= 10.2174/1385272811317050010}}

Although studies have not been reported for this compound, the closely related diethylphosphite exists predominantly as the phosphorus(V) tautomer.{{cite journal |doi=10.1139/v79-039|title=Tautomerization Equilibria for Phosphorous Acid and its Ethyl Esters, Free Energies of Formation of Phosphorous and Phosphonic Acids and their Ethyl Esters, and p Ka Values for Ionization of the P—H Bond in Phosphonic Acid and Phosphonic Esters |year=1979 |last1=Guthrie |first1=J. Peter |journal=Canadian Journal of Chemistry |volume=57 |issue=2 |pages=236–239 |doi-access=free }}