OH(²) + C₂H₄ Reaction: A Combined Crossed Molecular Beam and Theoretical Study

The reaction betweenthe ground-state hydroxyl radical,OH-((2)pi), and ethylene, C2H4,has beeninvestigated under single-collision conditions by the crossed molecularbeam scattering technique with mass-spectrometric detection and time-of-flightanalysis at the collision energy of 50.4 kJ/mol. Electronic structurecalculations of the underlying potential energy surface (PES) andstatistical Rice-Ramsperger-Kassel-Marcus (RRKM)calculations of product branching fractions on the derived PES forthe addition pathway have been performed. The theoretical resultsindicate a temperature-dependent competition between the anti-/syn-CH2CHOH (vinyl alcohol) + H, CH3CHO (acetaldehyde) + H, and H2CO (formaldehyde)+ CH3 product channels. The yield of the H-abstractionchannel could not be quantified with the employed methods. The RRKMresults predict that under our experimental conditions, the anti- and syn-CH2CHOH + H productchannels account for 38% (in similar amounts) of the addition mechanismyield, the H2CO + CH3 channel for similar to 58%,while the CH3CHO + H channel is formed in negligible amount(<4%). The implications for combustion and astrochemical environmentsare discussed.