A crossed beam and ab initio investigation of the reaction of boron monoxide (11BO; X2Σ+) with acetylene (C2H2; X1Σ +g)

Abstract

The reaction dynamics of boron monoxide (BO; X²Σ⁺) with acetylene (C₂H₂; X¹Σ⁺_g) were investigated under single collision conditions at a collision energy of 13 kJ mol⁻¹ employing the crossed molecular beam technique; electronic structure RRKM calculations were conducted to complement the experimental data. The reaction was found to have no entrance barrier and proceeded via indirect scattering dynamics initiated by an addition of the boron monoxide radical with its boron atom to the carbon–carbon triple bond forming the O¹¹BHCCH intermediate. The latter decomposed viahydrogen atom emission to form the linear O¹¹BCCH product through a tight exit transition state. The experimentally observed sideways scattering suggests that the hydrogen atom leaves perpendicularly to the rotational plane of the decomposing complex and almost parallel to the total angular momentum vector. RRKM calculations indicate that a minor micro channel could involve a hydrogen migration in the initial collision to form an O¹¹BCCH₂ intermediate, which in turn can also emit atomic hydrogen. The overall reaction to form O¹¹BCCH plus atomic hydrogen from the separated reactants was determined to be exoergic by 62 ± 8 kJ mol⁻¹. The reaction dynamics were also compared with the isoelectronic reaction of the cyano radical (CN; X²Σ⁺) with acetylene (C₂H₂; X¹Σ⁺_g) studied earlier.