The Criegee intermediate-formic acid reaction explored by rotational spectroscopy

The atmospheric reaction of the simplest Criegee intermediate, CH 2 OO, with formic acid has been investigated in the gas phase by pulsed Fourier-transform microwave spectroscopy. The dominant nascent product from this reaction was identified as hydroperoxymethyl formate (HOOCH 2 OCHO), for which two different conformations, formed through independent insertion mechanisms, were observed in the discharged plasma of a CH 2 I 2 /O 2 /formic acid gas mixture. The conformational identifications are supported by the observation of 13 C species in natural abundance together with the chemically mono substituted deuterium isotopologues. These isotopic observations further suggest that hydroperoxymethyl formate slightly decomposes, producing formic anhydride (OHCOCHO) in a dehydration reaction. Products resulting from the reaction between the Criegee intermediate, CH 2 OO, and formic acid are characterized by rotational spectroscopy.