Dihydroxymethylidene

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| ImageFile1 = Dihydroxycarbene.png

| ImageFile1_Ref = {{Chemboximage|correct|??}}

| ImageName1 = Structural formula of dihydroxymethylidene

| ImageFile2 = Dihydroxymethylidene-3D-balls.png

| ImageFile2_Ref = {{Chemboximage|correct|??}}

| ImageName2 = Ball and stick model of dihydroxymethylidene

| ImageCaption2 = Ball and stick model of dihydroxymethylidene{{legend|rgb(64, 64, 64)|Carbon, C}}{{legend|white|Hydrogen, H}}{{legend|red|Oxygen, O}}

| IUPACName = {{ubl|Carbon(II) hydroxide|Carbon dihydroxide|Carbonous hydroxide}}

| PIN = Dihydroxymethylidene

| OtherNames = {{ubl|Carbonic(II) acid|Carbonous acid|Dihydroxycarbene|Dihydroxymethylene|Dihydroxycarbon(2•)}}

|Section1={{Chembox Identifiers

| CASNo = 71946-83-3

| CASNo_Ref = {{cascite|correct|??}}

| PubChem = 191992

| ChemSpiderID = 11646598

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| MeSHName = Dihydroxycarbene

| SMILES = O[C]O

| StdInChI = 1S/CH2O2/c2-1-3/h2-3H

| StdInChI_Ref = {{Stdinchicite|correct|chemspider}}

| StdInChIKey = VZOMUUKAVRPMBY-UHFFFAOYSA-N

| StdInChIKey_Ref = {{Stdinchicite|correct|chemspider}}}}

|Section2={{Chembox Properties

| Formula = {{Chem2|C(OH)2}}

| C=1|O=2|H=2

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|Section3={{Chembox Related

| OtherCompounds = {{ubl|Tin(II) hydroxide|Lead(II) hydroxide|Formic acid|Orthocarbonic acid}}

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Dihydroxymethylidene or carbonous acid is a chemical compound with formula {{Chem2|C(OH)2}}. It is an unstable tautomer of formic acid. There is no evidence that this compound exists in solution, but the molecule has been detected in the gas phase.{{cite journal | doi = 10.1002/anie.200802105| title = Spectroscopic Identification of Dihydroxycarbene| year = 2008| last1 = Schreiner| first1 = Peter R.| last2 = Reisenauer| first2 = Hans Peter| journal = Angewandte Chemie International Edition| volume = 47| issue = 37| pages = 7071–7074| pmid = 18666191}} Many related carbenes are known, although they are often transient.M. Jones, Jr., R. A. Moss, in "Reactive Intermediate Chemistry", Edited by R. A. Moss, M. S. Platz, M. Jones, Jr., Wiley-Interscience, Hoboken, 2004.