The isotope exchange reaction of fast hydrogen atoms with deuterated alkynes and alkenes

The exchange reaction H(1 eV) + RD→RH + D, where RD was deuterated acetylene, methylacetylene, ethylene, and propylene was studied by laser induced fluorescence detection of the hydrogen and deuterium atoms. The reaction cross sections were 1.69 ± 0.22, 0.50±0.15, 1.85±0.20, and 1.10±0.14 Ų, respectively. The fraction of the incident relative kinetic energy released as translation was 0.42, 0.34, 0.40, and 0.34. That the addition of a methyl group only slightly reduces the energy released as translation is regarded as proof that the reaction at this energy does not involve a long lived intermediate complex, but is a direct localized displacement. Further confirmation comes from the observation that the velocity of the D atom product of H + C₂D₂ is correlated with the velocity of the H atom reactant.