title: Atmospheric Vinyl Alcohol to Acetaldehyde Tautomerization Revisited.
abstract: The atmospheric oxidation of vinyl alcohol (VA) produced by photoisomerization of acetaldehyde (AA) is thought to be a source of formic acid (FA). Nevertheless, a recent theoretical study predicted a high rate coefficient k1(298 K) of ≈10(-14) cm(3) molecule(-1) s(-1) for the FA-catalyzed tautomerization reaction 1 of VA back into AA, which suggests that FA buffers its own production from VA. However, the unusually high frequency factor implied by that study prompted us to reinvestigate reaction 1 . On the basis of a high-level ab initio potential energy profile, we first established that transition state theory is applicable, and derived a k1(298 K) of only ≈2 × 10(-20) cm(3) molecule(-1) s(-1), concluding that the reaction is negligible. Instead, we propose and rationalize another important VA sink: its uptake by aqueous aerosol and cloud droplets followed by fast liquid-phase tautomerization to AA; global modeling puts the average lifetime by this sink at a few hours, similar to oxidation by OH.
authors.affiliation: Department of Chemistry, University of Leuven , B-3001 Heverlee, Belgium.
authors.forename: Jozef
authors.initials: J
authors.lastname: Peeters
authors.affiliation: Department of Chemistry, University of Leuven , B-3001 Heverlee, Belgium.
authors.forename: Vinh Son
authors.initials: VS
authors.lastname: Nguyen
authors.affiliation: Belgian Institute for Space Aeronomy , Avenue Circulaire 3, B-1180 Brussels, Belgium.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Müller
keywords: ab initio calculations; acetaldehyde photoisomerization; formic acid sources; prereaction complexes; transition state theory; uptake by aerosols; vinyl alcohol sinks