OH( 2 Π) + C 2 H 4 Reaction: A Combined Crossed Molecular Beam and Theoretical Study.

The reaction between the ground-state hydroxyl radical, OH( 2 Π), and ethylene, C 2 H 4 , has been investigated under single-collision conditions by the crossed molecular beam scattering technique with mass-spectrometric detection and time-of-flight analysis at the collision energy of 50.4 kJ/mol. Electronic structure calculations of the underlying potential energy surface (PES) and statistical Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of product branching fractions on the derived PES for the addition pathway have been performed. The theoretical results indicate a temperature-dependent competition between the anti -/ syn -CH 2 CHOH (vinyl alcohol) + H, CH 3 CHO (acetaldehyde) + H, and H 2 CO (formaldehyde) + CH 3 product channels. The yield of the H-abstraction channel could not be quantified with the employed methods. The RRKM results predict that under our experimental conditions, the anti - and syn -CH 2 CHOH + H product channels account for 38% (in similar amounts) of the addition mechanism yield, the H 2 CO + CH 3 channel for ∼58%, while the CH 3 CHO + H channel is formed in negligible amount (<4%). The implications for combustion and astrochemical environments are discussed.