What it is
Orthocarbonic acid, C(OH)4, is a carbon atom bonded to four hydroxyl groups, a structure so prone to falling apart that it eluded chemists for over a century even though its substituted cousins, the orthocarbonates, are stable. The team made it by bombarding frozen water and carbon dioxide ices with high-energy electrons, mimicking the galactic cosmic rays that penetrate dense interstellar clouds, at 5 to 10 kelvin and pressures below 10 to the minus 10 torr. Tunable synchrotron vacuum-ultraviolet light and photoionization mass spectrometry pinned down the molecule and caught its reaction intermediates, carbonic acid and methanetriol, forming alongside it.
Why it matters
Completing the ortho-acid series closes a long-standing gap in fundamental chemistry: a molecule with four hydroxyls on one carbon was widely assumed too unstable to ever isolate. The same conditions that produced it in the lab, 5 to 10 kelvin and near-perfect vacuum, exist inside dense molecular clouds, so the result argues that if carbonic acid is abundant in space, methanetetrol may be waiting there to be detected. It shows interstellar ices host a richer and more counterintuitive chemistry than models assumed.
Underlined numbers link to their source. Every metric and quoted figure is listed under Sources and data below.
Filed underastrochemistry, interstellar ice, molecular synthesis, photoionization, orthocarbonic acid