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Line 41: }}   '''Dihydroxymethylidene''' is a ] with ] C(OH)<sub>2</sub> or HO-C-OH. There is no evidence that this compound exists in solution, but the molecule has been detected in the gas phase.<ref> Schreiner, Peter R.; Reisenauer, Hans Peter "Spectroscopic identification of dihydroxycarbene" Angewandte Chemie, International Edition (2008, volume 47, 7071-7074. {{citation neededDOI|date=January 201310.1002/anie.200802105}} </ref> Many related carbenes are known, although they are often transient.<ref>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.</ref>   == Production and properties== Dihydroxymethylidene is a ], formally a ] (double ]) of the ] ''':'''{{chem|CH|2}}, and its formula can be written ''':'''{{chem|C(OH)|2}} to indicate the two unshared ]s. It is an ] of ] (H-(C=O)-OH). Alternatively,Dihydroxymethylidene dihydroxymethylideneis canproduced bein producedthe gas phase viaby high vacuum ] of oxalic acid.:▼   :C<sub>2</sub>O<sub>4</sub>H<sub>2</sub> → C(OH)<sub>2</sub> + CO<sub>2</sub> The molecule can also be viewed as an ] of ], which would formerly be called '''carbonous acid'''. In theory, removal of its ] would result in two anions, ] (HO-C''':'''-{{chem|O|-}}, isomeric to ]) and ] (''':'''C({{chem|O|-}})2). Salts of the latter have been obtained in small amounts, at low temperatures.<ref name=kafa1>Zakya H. Kafafi, Robert H. Hauge, W. Edward Billups, and John L. Margrave (1983) ''''. Journal of the American Chemical Society, volume 183, pages 3886--3893. {{doi|10.1021/ja00350a025}}</ref> The species is a bent molecule with a O-C-O angle of 105.6° for the C<sub>2v</sub> all trans rotamer. Although stable at 10 K, at higher temperatures it ]izes to formic acid.   == Discovery and production == Dihydroxymethylidene is produced in the gas phase by neutralization of the ] radical cation which is formed by dissociative ] of ]. Reionization shows that dihydroxymethylidene can survive intact, and thus exists as a stable species with appreciable barriers for dissociation or rearrangement to formic acid.   During the production of dihydroxymethylidene, a small fraction of the ] decomposes to water and ]. Comparison of experimental results with ab initio theory shows that the dissociating molecules are generated in the electronically excited ], while the large amount of surviving carbene molecules is formed in the ].   ▲Alternatively, dihydroxymethylidene can be produced via high vacuum ] of oxalic acid.   == Properties and reactions == In high concentrations, dihydroxymethylidene has a tendency to, through a series of steps, convert to ]. These steps are as follows:   :2 dihydroxymethylidene → ethene-1,1,2,2-tetrol → glyoxylic acid   Despite its older name, it is unlikely that this substance reacts as an acid in the conventional sense.   ==Carbonite==

Revision as of 13:21, 18 March 2014

Dihydroxymethylidene
Structural formula of dihydroxymethylidene
Structural formula of dihydroxymethylidene
Ball and stick model of dihydroxymethylidene
Ball and stick model of dihydroxymethylidene
Names
IUPAC name Dihydroxymethylidene
Systematic IUPAC name Dihydroxymethylidene (substitutive)
Dihydroxidocarbon(2•) (additive)
Other names Carbonic(II) acid

Carbonous acid
Dihydroxycarbene

Dihydroxymethylene
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
MeSH Dihydroxycarbene
PubChem CID
CompTox Dashboard (EPA)
InChI
  • InChI=1S/CH2O2/c2-1-3/h2-3HKey: VZOMUUKAVRPMBY-UHFFFAOYSA-N
SMILES
  • OO
Properties
Chemical formula CH2O2
Molar mass 46.025 g·mol
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references
Chemical compound

Dihydroxymethylidene is a chemical compound with formula C(OH)2. There is no evidence that this compound exists in solution, but the molecule has been detected in the gas phase. Many related carbenes are known, although they are often transient.

Production and properties

Dihydroxymethylidene is produced in the gas phase by high vacuum flash pyrolysis of oxalic acid:

C2O4H2 → C(OH)2 + CO2

The species is a bent molecule with a O-C-O angle of 105.6° for the C2v all trans rotamer. Although stable at 10 K, at higher temperatures it isomerizes to formic acid.

Carbonite

The conjugate base of dihydroxycarbene is the chemical formula . Alkali metal salts, e.g., Li
2CO
2, K
2CO
2, and Cs
2CO
2, have been observed at 15K.

At lower metal concentrations, salts of the monovalent anions CO
2 were favored over CO
2. Carbonite was not detected when sodium was used as the metal. The alkali metal carbonites obtained in the cryogenic experiments decomposed to the corresponding carbonate (with release of carbon monoxide) or oxalate. The carbonite ion is promptly converted to carbonate in the presence of oxygen.

The presence of carbonite ions has been proposed to be relevant to the absorption of carbon monoxide on calcium oxide and magnesium oxide and on ceria. In the former, it has been suggested that the carbon atom attaches coordinatively to an oxygen atom from the substrate through its free bonds. In these contexts, it appears that the carbonite ion reacts with excess carbon monoxide to form an anion with the ketene structure, O=C=CO
2.

Infrared spectroscopy data confirm earlier theoretical studies that the carbonite anion has a bent structure, with the O-C-O angle varying between 120 and 130 degrees depending on the context. The metal atoms interact with both oxygen atoms. However two geometrical arrangements for the lithium and cesium salts were detected, only one of them being symmetrical on the two oxygen atoms.

References

  1. Schreiner, Peter R.; Reisenauer, Hans Peter "Spectroscopic identification of dihydroxycarbene" Angewandte Chemie, International Edition (2008, volume 47, 7071-7074. doi:10.1002/anie.200802105
  2. 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.
  3. ^ Zakya H. Kafafi, Robert H. Hauge, W. Edward Billups, and John L. Margrave (1983) Carbon dioxide activation by lithium metal. 1. Infrared spectra of Li
    CO
    2 , Li
    C
    2O
    4 , and Li
    2CO
    2 in inert-gas matrices    . Journal of the American Chemical Society, volume 183, pages 3886--3893. doi:10.1021/ja00350a025
  4. ^ Zakya H. Kafafi, Robert H. Hauge, W. Edward Billups, and John L. Margrave (1984), Carbon dioxide activation by alkali metals. 2. Infrared spectra of M
    CO
    2 and M
    2CO
    2 in argon and nitrogen matrices    . Inorganic Chemistry, volume 23, pages 177-183. doi:10.1021/ic00170a013.
  5. ^ M. A. Babaeva and A. A. Tsyganenko (1987), Infrared spectroscopic evidence for the formation of carbonite CO
    2 ions in CO interaction with basic oxide surfaces     Reaction Kinetics and Catalysis Letters, volume 34, issue 1, pages 9--14. doi:10.1007/BF02069193
  6. ^ Binet, Claude (1994). "FTIR study of carbon monoxide adsorption on ceria: CO2 carbonite dianion adsorbed species". Journal of the Chemical Society, Faraday Transactions. 90: 1023–1028. doi:10.1039/FT9949001023. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
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