The reaction of hydroxyl and methylperoxy radicals is not a major source of atmospheric methanol
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Updated: Feb 3, 2026

Monitoring Equilibrium Changes in RNA Structure by 'Peroxidative' and 'Oxidative' Hydroxyl Radical Footprinting
Published on: October 17, 2011
Rebecca L Caravan1, M Anwar H Khan2, Judit Zádor3
1Combustion Research Facility, Mailstop 9055, Sandia National Laboratories, Livermore, CA, 94551, USA. rcarava@sandia.gov.
Abstract:
Methanol is a benchmark for understanding tropospheric oxidation, but is underpredicted by up to 100% in atmospheric models. Recent work has suggested this discrepancy can be reconciled by the rapid reaction of hydroxyl and methylperoxy radicals with a methanol branching fraction of 30%. However, for fractions below 15%, methanol underprediction is exacerbated. Theoretical investigations of this reaction are challenging because of intersystem crossing between singlet and triplet surfaces - ∼45% of reaction products are obtained via intersystem crossing of a pre-product complex - which demands experimental determinations of product branching. Here we report direct measurements of methanol from this reaction. A branching fraction below 15% is established, consequently highlighting a large gap in the understanding of global methanol sources. These results support the recent high-level theoretical work and substantially reduce its uncertainties.
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