Is carbonic acid an organic acid

On the trail of carbon dioxide

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12/27/10 Gaseous carbon dioxide is stable down to -30 ° C

Carbonic acid: isolated in gaseous form for the first time and examined spectroscopically

Fig. 1: Oleic acid molecules were captured from the gas phase in a solid noble gas matrix at <10 K and examined by IR spectroscopy. Also the 2Dog 13C isotopologues were measured and the existence of a 1:10: 1 mixture of two monomer conformations and the ring-shaped dimer (H.2CO3)2 be inferred. This data is valuable for tracking down gaseous carbonic acid in space.
Source: applied Chemistry

So far it has stubbornly resisted all detection attempts: according to current textbook opinions, gaseous carbonic acid should not even exist because it breaks down directly into water and carbon dioxide - and can therefore only be detected as a trace component. A team led by Hinrich Grothe from the Vienna University of Technology and Thomas Loerting from the University of Innsbruck has finally provided evidence to the contrary. As the Austrian scientists report in the journal Angewandte Chemie, they were able to isolate gaseous carbon dioxide and collect spectroscopic data.

Anyone who orders carbonated mineral water is actually referring to a drink that contains carbon dioxide. Until not so long ago it was even believed that carbonic acid (H.2CO3) as a stable molecule does not exist at all. We now know that a carbonated drink does contain carbonic acid - but only in very, very low concentrations. So far, the molecule has evaded most attempts at isolation and direct detection. As a solid, however, it has already been produced by a few scientists. It is also assumed that solid carbonic acid occurs in cirrus clouds in the earth's atmosphere and in space.

The Austrian scientists have now been able to show that there is also gaseous carbon dioxide and that it is stable at temperatures down to –30 ° C. For the experiments, solid carbonic acid was generated by acid-base reactions at very low temperatures and then heated to -30 ° C. The evaporating molecules were trapped in a matrix made of the noble gas argon and cooled down again significantly. This creates a kind of frozen “image” of the gaseous carbon dioxide, which the researchers were able to examine using infrared spectroscopy.

The spectra showed that gaseous carbonic acid occurs in three different forms. The scientists found two monomers that differ in their conformation, i.e. the spatial arrangement of their individual atoms, and a dimer made up of two molecules linked by hydrogen bonds.

The detailed spectroscopic data obtained are of great interest for astronomy, because they could facilitate the detection of gaseous carbonic acid in space, where it is suspected, for example, in the tail of comets or on Mars.


Spectroscopic observation of matrix-isolated carbonic acid, deposited from the gas phase
J. Bernard, et al., Angew. Chem.2010. DOI: 10.1002 / anie.201004729

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