Methanetetracarboxylate

Methanetetracarboxylate is the tetraanion with formula C(CO₂)4−4. It has four carboxylate groups attached to a central carbon atom; so it has the same carbon backbone as neopentane. It is an oxocarbon anion, that is, consists only of carbon and oxygen.

Methanetetracarboxylate

Dots that are highlighted in blue carry a partial negative charge. Red dots are oxygen atoms, black dots are carbon atoms.
Names
Preferred IUPAC name Methanetetracarboxylate[PubChem 1]
Identifiers
CAS Number	acid: 193197-67-0
3D model (JSmol)	[PubChem 2]: Interactive image Interactive image acid: Interactive image
PubChem CID	57459306 [PubChem 3][PubChem 4] acid: 19035093
InChI [PubChem 5]: InChI=1S/C5H4O8/c6-1(7)5(2(8)9,3(10)11)4(12)13/h(H,6,7)(H,8,9)(H,10,11)(H,12,13)/p-4 Key: NKVMCSDLYHGDMD-UHFFFAOYSA-J[PubChem 6] acid: InChI=1S/C5H4O8/c6-1(7)5(2(8)9,3(10)11)4(12)13/h(H,6,7)(H,8,9)(H,10,11)(H,12,13) Key: NKVMCSDLYHGDMD-UHFFFAOYSA-N
SMILES [PubChem 7]: C(=O)(C(C(=O)[O-])(C(=O)[O-])C(=O)[O-])[O-] O=C([O-])C(C([O-])=O)(C([O-])=O)C([O-])=O acid: C(=O)(C(C(=O)O)(C(=O)O)C(=O)O)O
Properties
Chemical formula	C(CO−2)4
Molar mass	188.047 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The term is also used for any salt with that anion; or for any ester with the C(−C(=O)−O−)₄ moiety.^[1]

The salts and esters are relatively uncommon, and their uses appear to be limited to chemical research. Sodium methanetetracarboxylate Na₄C(CO₂)₄ can be obtained by oxidation of pentaerythritol C(CH₂OH)₄ with oxygen in sodium hydroxide solution at pH 10 and about 60 °C, in the presence of palladium as a catalyst.^[2]

The anion can be seen as the result of removing four protons from methanetetracarboxylic acid, a hypothetical organic compound with formula H₄C₅O₈ or C(COOH)₄. This acid has not been synthesised (as of 2009), and is believed to be unstable, but its ethyl ester, tetraethyl methanetetracarboxylate, C(COOCH₂CH₃)₄, is a specialty chemical and has been used in organic synthesis.^[3]