The Criegee intermediate-formic acid reaction explored by rotational spectroscopy

Abstract

The atmospheric reaction of the simplest Criegee intermediate, CH₂OO, 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 (HOOCH₂OCHO), for which two different conformations, formed through independent insertion mechanisms, were observed in the discharged plasma of a CH₂I₂/O₂/formic acid gas mixture. The conformational identifications are supported by the observation of ¹³C 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.