Dynamics of Cl + propane, butanes revisited: a crossed beam slice imaging study

Abstract

We report velocity–flux contour maps for H–D abstraction in selected Cl + alkane reactions measured by means of crossed beam scattering combined with universal DC slice imaging. The studied hydrocarbons are propane and its two selectively deuterated isotopologues, namely 1,1,1,3,3,3-propane-d₆ and 2,2-propane-d₂, n-butane and isobutane (2-methyl-propane), with detection of the hydrocarbon radical product by 157 nm single photon ionization. Data are obtained at collision energies of 12–13 kcal mol⁻¹ using a high-density atomic chlorine radical source combining Cl₂ photolysis with ablation. All presented scattering distributions involving secondary and tertiary abstractions show distinct differences. Their comparisons allow for revisiting the dynamical picture of these reactions in terms of the nature of the abstraction sites, radical product energy disposal, and H vs. D abstraction. Results are discussed in the light of previous work and ab initio thermochemical calculations, along with proposals to future directions for investigation.