Carbonic Acid Aloft

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Science  28 Jan 2011:
Vol. 331, Issue 6016, pp. 379
DOI: 10.1126/science.331.6016.379-a

The chemistry of carbon dioxide in water plays a remarkably diverse series of roles in our daily lives—modulating acidity in blood and ocean water, lending soda its sparkle and bread its fluff. It's all the more remarkable, then, that the adduct of the two molecules, carbonic acid, spent centuries eluding characterization. Its deprotonated conjugate bicarbonate (HCO3) is reactive but easily isolable; in contrast, it was only recently established that the HOC(O)OH molecule persists for any length of time in solution before breaking apart. Bernard et al. have now shown that carbonic acid is also at least kinetically stable in the gas phase as well. By subliming the solid acid and then capturing it in a frozen argon matrix, the authors were able to detect the vibrational signatures of two conformational isomers (with a W-shaped one predominating) as well as a hydrogen-bonded dimer. The findings raise the prospect of finding the molecule in comet tails or other planetary atmospheres.

Angew. Chem. Int. Ed. 10.1002/anie.201004729 (2010).

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