Orthocarbonic acid
Hypothetical compound with formula C(OH)4
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Orthocarbonic acid (also known as methanetetrol) is a chemical compound with the chemical formula H4CO4 or C(OH)4. Its molecular structure consists of a single carbon atom bonded to four hydroxyl groups. It would be therefore a fourfold alcohol. In theory, it could lose four protons to give the hypothetical oxocarbon anion orthocarbonate CO4−4, and is therefore considered an oxoacid of carbon.
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| Names | |||
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| Preferred IUPAC name
Methanetetrol[1] | |||
| Systematic IUPAC name
Orthocarbonic acid | |||
Other names
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| Identifiers | |||
3D model (JSmol) |
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PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |||
| C(OH)4 | |||
| Molar mass | 80.039 g·mol−1 | ||
| Related compounds | |||
Other cations |
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Related compounds |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Orthocarbonic acid is highly unstable and long held to be a hypothetical chemical compound. Calculations show that it decomposes into carbonic acid and water:[2][3]
- H4CO4 → H2CO3 + H2O
However, orthocarbonic acid was first synthesized in 2025 from the electron-irradiation of a frozen mixture of water and carbon dioxide and identified by mass spectrometry.[4]
Researchers predict that orthocarbonic acid is stable at high pressure; thus, it may form in the interior of the ice giant planets Uranus and Neptune, where water and methane are common.[5]
Orthocarbonate anions
By loss of one through four protons, orthocarbonic acid could yield four anions: H3CO−4 (trihydrogen orthocarbonate), H2CO2−4 (dihydrogen orthocarbonate), HCO3−4 (hydrogen orthocarbonate), and CO4−4 (orthocarbonate).
Numerous salts of fully deprotonated CO4−4, such as Ca2CO4 (calcium orthocarbonate) or Sr2CO4 (strontium orthocarbonate), have been synthesized under high pressure conditions and structurally characterized by X-ray diffraction.[6][7][8][9] Strontium orthocarbonate, Sr2CO4, is stable at atmospheric pressure. Orthocarbonate is tetrahedral in shape, and is isoelectronic to orthonitrate. The C-O distance is 1.41 Å.[10] Sr3(CO4)O is an oxide orthocarbonate (tristrontium orthocarbonate oxide), also stable at atmospheric pressure.[11]
Orthocarbonate esters
The tetravalent moiety CO4 is found in stable organic compounds; they are formally esters of orthocarbonic acid, and therefore are called orthocarbonates. For example, tetraethoxymethane can be prepared by the reaction between chloropicrin and sodium ethoxide in ethanol.[12] Polyorthocarbonates are stable polymers that might have applications in absorbing organic solvents in waste treatment processes,[13] or in dental restorative materials.[14] The explosive trinitroethylorthocarbonate possesses an orthocarbonate core.
A linear polymer which can be described as a (spiro) orthocarbonate ester of pentaerythritol, whose formula could be written as [(−CH2)2C(CH2−)2 (−O)2C(O−)2]n, was synthesized in 2002.[15]
The carbon atom in the spiro ester bis-catechol orthocarbonate was found to have tetrahedral bond geometry, contrasting with the square planar geometry of the silicon atom in the analogous orthosilicate ester.[16]
Orthocarbonates may exist in several conformers, that differ by the relative rotation of the C–O–C bridges. The conformation structures of some esters, such as tetraphenoxymethane, tetrakis(3,5-dimethyl-phenoxy)methane, and tetrakis(4-bromophenoxy)methane have been determined by X-ray diffraction.[17]
See also
- Pentaerythritol, C(CH2OH)4
- Silicic acid, Si(OH)4
- Carbonic acid, H2CO3