Kinetics and Product Yields of the OH Initiated Oxidation of Hydroxymethyl Hydroperoxide
Hydroxymethyl hydroperoxide (HMHP), formed in the reaction of the C1 Criegee intermediate with water, is among the most abundant organic peroxides in the atmosphere. Although reaction with OH is thought to represent one of the most important atmospheric removal processes for HMHP, this reaction has been largely unstudied in the laboratory. Here, we present measurements of the kinetics and products formed in the reaction of HMHP with OH. HMHP was oxidized by OH in an environmental chamber; the decay of the hydroperoxide and the formation of formic acid and formaldehyde were monitored over time using CF_3O– chemical ionization mass spectrometry (CIMS) and laser-induced fluorescence (LIF). The loss of HMHP by reaction with OH is measured relative to the loss of 1,2-butanediol [k_(1,2-butanediol+OH) = (27.0 ± 5.6) × 10^(–12) cm^3 molecule^(–1)s^(–1)]. We find that HMHP reacts with OH at 295 K with a rate coefficient of (7.1 ± 1.5) × 10^(–12) cm^3molecule^(–1)s^(–1), with the formic acid to formaldehyde yield in a ratio of 0.88 ± 0.21 and independent of NO concentration (3 × 10^(10) – 1.5 × 10^(13) molecules cm^(–3)). We suggest that, exclusively, abstraction of the methyl hydrogen of HMHP results in formic acid, while abstraction of the hydroperoxy hydrogen results in formaldehyde. We further evaluate the relative importance of HMHP sinks and use global simulations from GEOS-Chem to estimate that HMHP oxidation by OH contributes 1.7 Tg yr^(–1) (1–3%) of global annual formic acid production.
© 2018 American Chemical Society. Received: May 14, 2018; Revised: July 2, 2018; Published: July 11, 2018. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144469; in addition, we acknowledge support from the NSF (Grant Nos. 1240604, 1628530, and 1628491) and NASA (Grants NNX12AC06G and NNX14AP46G). We acknowledge the Center for Exploitation of Solar Energy, University of Copenhagen, and the Danish Center for Scientific Computing for funding. We thank Daniel Jacob and the Atmospheric Chemistry Modeling Group at Harvard University for their work on the GEOS-Chem model. In addition, SEAC4RS data from the Lidar Applications Group at the NASA Langley Research Center and from the Meteorological Measurement System (MMS) instrument operated by Paul Bui's group from the NASA Ames Research Center aided in the analysis presented here. The authors declare no competing financial interest.
Supplemental Material - jp8b04577_si_001.pdf