| Revision as of 17:44, 9 June 2013 editDawnseeker2000 (talk | contribs)Autopatrolled, Extended confirmed users, File movers, New page reviewers, Pending changes reviewers, Rollbackers482,496 editsm Reverted edits by 120.61.23.96 (talk) to last version by Addbot← Previous edit | Revision as of 18:46, 25 February 2014 edit undoSmokefoot (talk | contribs)Autopatrolled, Extended confirmed users, Pending changes reviewers, Rollbackers74,247 edits absorbing carbonite infoNext edit → | ||
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| Despite its older name, it is unlikely that this substance reacts as an acid in the conventional sense. | Despite its older name, it is unlikely that this substance reacts as an acid in the conventional sense. | ||
| ==Carbonite== | |||
| The conjugate base of dihydroxycarbene is the ] <sup>2-</sup>. ] salts, e.g., {{chem|Li|2|CO|2}}, {{chem|K|2|CO|2}}, and {{chem|Cs|2|CO|2}}, have been observed at 15].<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><ref name=kafa2/> | |||
| At lower metal concentrations, salts of the ] anions {{chem|CO|2|-}} were favored over {{chem|CO|2|2-}}. Carbonite was not detected when ] was used as the metal.<ref name=kafa2>Zakya H. Kafafi, Robert H. Hauge, W. Edward Billups, and John L. Margrave (1984), ''''. Inorganic Chemistry, volume 23, pages 177-183. {{doi|10.1021/ic00170a013}}.</ref> The alkali metal carbonites obtained in the cryogenic experiments decomposed to the corresponding ] (with release of ]) or ].<ref name=kafa1/><ref name=kafa2/> The carbonite ion is promptly converted to carbonate in the presence of oxygen.<ref name=baba/><ref name=bine/> | |||
| The presence of carbonite ions has been proposed to be relevant to the absorption of ] on ] and ]<ref name=baba>M. A. Babaeva and A. A. Tsyganenko (1987), '''' Reaction Kinetics and Catalysis Letters, volume 34, issue 1, pages 9--14. {{doi|10.1007/BF02069193}}</ref> and on ].<ref name=bine>{{cite journal|last=Binet|first=Claude|coauthors=Ahmed Badri, Magali Boutonnet-Kizling and Jean-Claude Lavalley|title=FTIR study of carbon monoxide adsorption on ceria: CO<sub>2</sub><sup>2-</sup> carbonite dianion adsorbed species|journal=Journal of the Chemical Society, Faraday Transactions|year=1994|volume=90|pages=1023–1028|doi=10.1039/FT9949001023}}</ref> In the former, it has been suggested that the carbon atom attaches ] to an oxygen atom from the substrate through its free bonds.<ref name=baba/> In these contexts, it appears that the carbonite ion reacts with excess carbon monoxide to form an anion with the ] structure, O=C={{chem|CO|2|2-}}.<ref name=baba/> | |||
| 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.<ref name=kafa1/><ref name=kafa2/> | |||
| == References == | == References == | ||
Revision as of 18:46, 25 February 2014
| |||
| Names | |||
|---|---|---|---|
| IUPAC name Dihydroxymethylidene | |||
| Systematic IUPAC name
Dihydroxymethylidene (substitutive) Dihydroxidocarbon(2•) (additive) | |||
| Other names
Carbonic(II) acid Carbonous acid | |||
| Identifiers | |||
| CAS Number | |||
| 3D model (JSmol) | |||
| ChemSpider | |||
| MeSH | Dihydroxycarbene | ||
| PubChem CID | |||
| CompTox Dashboard (EPA) | |||
InChI
| |||
SMILES
| |||
| 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 | |||
Dihydroxymethylidene is a chemical compound with formula C(OH)2 or HO-C-OH. There is no evidence that this compound exists in solution, but the molecule has been detected in the gas phase.
Dihydroxymethylidene is a carbene, formally a diol (double alcohol) of the methylene radical :CH
2, and its formula can be written :C(OH)
2 to indicate the two unshared valence electrons. It is an isomer of formic acid (H-(C=O)-OH).
The molecule can also be viewed as an oxyacid of carbon, which would formerly be called carbonous acid. In theory, removal of its protons would result in two anions, bicarbonite (HO-C:-O
, isomeric to formate) and carbonite (:C(O
)2). Salts of the latter have been obtained in small amounts, at low temperatures.
Discovery and production
Dihydroxymethylidene is produced in the gas phase by neutralization of the dihydroxymethaniumyl radical cation which is formed by dissociative electron ionization of oxalic acid. 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 methylidene decomposes to water and carbon monoxide. Comparison of experimental results with ab initio theory shows that the dissociating molecules are generated in the electronically excited triplet state, while the large amount of surviving carbene molecules is formed in the singlet ground state.
Alternatively, dihydroxymethylidene can be produced via high vacuum flash pyrolysis of oxalic acid.
Properties and reactions
In high concentrations, dihydroxymethylidene has a tendency to, through a series of steps, convert to glyoxylic acid. 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
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
- ^ 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 Cite error: The named reference "kafa1" was defined multiple times with different content (see the help page). - ^ 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. - ^ 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 - ^ 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.
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