Orthocarbonic acid (also known as carbon hydroxide or methanetetrol) is a chemical compound with the chemical formulaH4CO4 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 anionorthocarbonateCO4−4, and is therefore considered an oxoacid of carbon.
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 1.41Å.[10]Sr3(CO4)O is an oxide orthocarbonate (tristrontium orthocarbonate oxide), also stable at atmospheric pressure.[11]
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]
↑ Sagatova, Dinara; Shatskiy, Anton; Sagatov, Nursultan; Gavryushkin, Pavel N.; Litasov, Konstantin D. (2020). "Calcium orthocarbonate, Ca2CO4-Pnma: A potential host for subducting carbon in the transition zone and lower mantle". Lithos. 370–371: 105637. Bibcode:2020Litho.37005637S. doi:10.1016/j.lithos.2020.105637. ISSN0024-4937. S2CID224909120.{{cite journal}}: CS1 maint: article number as page number (link)
↑ David T. Vodak, Matthew Braun, Lykourgos Iordanidis, Jacques Plévert, Michael Stevens, Larry Beck, John C. H. Spence, Michael O'Keeffe, Omar M. Yaghi (2002): "One-Step Synthesis and Structure of an Oligo(spiro-orthocarbonate)". Journal of the American Chemical Society, volume 124, issue 18, pages 4942–4943. doi:10.1021/ja017683i
↑ H. Meyer, G. Nagorsen (1979): "Structure and reactivity of the orthocarbonic and orthosilicic acid esters of pyrocatechol". Angewandte Chemie International Edition in English, volume 18, issue 7, pages 551-553. doi:10.1002/anie.197905511
↑ N. Narasimhamurthy, H. Manohar, Ashoka G. Samuelson, Jayaraman Chandrasekhar (1990): "Cumulative anomeric effect: A theoretical and x-ray diffraction study of orthocarbonates". Journal of the American Chemical Society, volume 112, issue 8, pages 2937–2941. doi:10.1021/ja00164a015
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