methanetetracarboxylate
{{Expert needed|Chemicals|date=April 2025}}
{{Short description|Ion}}
{{Chembox
| ImageFile = Methanetetracarboxylate.png
| ImageFile1 = chemfm methanetetracarboxylate 4neg.svg
| ImageSize1 = 117px
| ImageCaption1 = Dots that are highlighted in blue carry a partial negative charge. Red dots are oxygen atoms, black dots are carbon atoms.
| PIN = Methanetetracarboxylate{{cite web |title=NKVMCSDLYHGDMD-UHFFFAOYSA-J |url=https://pubchem.ncbi.nlm.nih.gov/compound/57459306#section=IUPAC-Name |website=pubchem.ncbi.nlm.nih.gov |accessdate=14 March 2019 |language=en |quote=IUPAC Name methanetetracarboxylate}}
| Section1 = {{Chembox Identifiers
| PubChem = 57459306
| PubChem_Comment = {{cite web |title=NKVMCSDLYHGDMD-UHFFFAOYSA-J |url=https://pubchem.ncbi.nlm.nih.gov/compound/57459306#section=Top |website=pubchem.ncbi.nlm.nih.gov |accessdate=14 March 2019 |language=en |quote=PubChem CID: 57459306}}{{cite web |title=SID 137126464 - PubChem |url=https://pubchem.ncbi.nlm.nih.gov/substance/137126464 |website=pubchem.ncbi.nlm.nih.gov |accessdate=14 March 2019 |language=en |quote=PubChem CID: 57459306}}
| PubChem1_Comment = {{cite web |title=NKVMCSDLYHGDMD-UHFFFAOYSA-J |url=https://pubchem.ncbi.nlm.nih.gov/compound/57459306#section=Substances-by-Category |website=pubchem.ncbi.nlm.nih.gov |accessdate=14 March 2019 |language=en |format=table |quote=Source External ID PubChem SID chemicalize.org by ChemAxon 280211 137126464}}{{cite web |title=SID 137126464 - PubChem |url=https://pubchem.ncbi.nlm.nih.gov/substance/137126464#section=Top |website=pubchem.ncbi.nlm.nih.gov |accessdate=14 March 2019 |language=en |quote=PubChem SID: 137126464}}
| index2_label = acid
| CASNo2 = 193197-67-0
| PubChem2 = 19035093
| SMILES = C(=O)(C(C(=O)[O-])(C(=O)[O-])C(=O)[O-])[O-]
| SMILES1 = O=C([O-])C(C([O-])=O)(C([O-])=O)C([O-])=O
| 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
| InChIKey = NKVMCSDLYHGDMD-UHFFFAOYSA-J{{cite web |title=NKVMCSDLYHGDMD-UHFFFAOYSA-J |url=https://pubchem.ncbi.nlm.nih.gov/compound/57459306#section=InChI-Key |website=pubchem.ncbi.nlm.nih.gov |accessdate=14 March 2019 |language=en |quote=InChI Key NKVMCSDLYHGDMD-UHFFFAOYSA-J}}
| InChI2=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)
| InChIKey2 = NKVMCSDLYHGDMD-UHFFFAOYSA-N
| SMILES2 = C(=O)(C(C(=O)O)(C(=O)O)C(=O)O)O
}}
| Section2 = {{Chembox Properties
| Formula = {{chem2|C(CO2−)4}}
| C=5|O=8
}}
}}
Methanetetracarboxylate is the tetraanion with formula {{chem2|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.
The term is also used for any salt with that anion; or for any ester with the {{chem2|C(\sC(\dO)\sO\s)4}} moiety.{{cite journal|journal = Recueil des Travaux Chimiques des Pays-Bas|title = Les Éthers de L'acide Méthanetétracarboxylique|trans-title = The Esters of Methanetetracarboxylic Acid|first1 = H. J.|last1 = Backer|first2 = J.|last2 = Lolkema|year = 1939|doi =10.1002/recl.19390580106|volume = 58|pages = 23–33|language = fr}}
The salts and esters are relatively uncommon, and their uses appear to be limited to chemical research. Sodium methanetetracarboxylate {{chem2|Na4C(CO2)4}} can be obtained by oxidation of pentaerythritol {{chem2|C(CH2OH)4}} with oxygen in sodium hydroxide solution at pH 10 and about 60 °C, in the presence of palladium as a catalyst.{{cite patent|country = WO|number = 2012026212A1|invent1 = 稲山俊宏 (Toshihiro INAYAMA)|invent2 = 聡日吉 (Satoshi HIYOSHI)|invent3 = 信仁雨宮 (Nobuhito AMEMIYA)|invent4 = 茂久岸本 (Shigehisa KISHIMOTO)|title = Tetraester of pentaerythritol|status = patent|pubdate = 2012-03-01|pridate = 2010-08-24|fdate = 2011-06-30|assign1 = Kyowa Hakko Kirin}}
The anion can be seen as the result of removing four protons from methanetetracarboxylic acid, a hypothetical organic compound with formula {{chem2|H4C5O8}} or {{chem2|C(COOH)4}}. This acid has not been synthesised (as of 2009), and is believed to be unstable, but its ethyl ester, tetraethyl methanetetracarboxylate, {{chem2|C(COOCH2CH3)4}}, is a specialty chemical and has been used in organic synthesis.{{cite journal|first1 = Armin|last1 = de Meijere|first2 = Rafael R.|last2 = Kostikov|first3 = Andrei I.|last3 = Savchenko|first4 = Sergei I.|last4 = Kozhushkov|title = Diethyl Cyclopropylidenemalonate: Facile Preparation, Generation in situ, and Various Transformations|journal = European Journal of Organic Chemistry|year = 2004|volume = 2004|issue = 19|pages = 3992–4002|doi = 10.1002/ejoc.200400374}}