Abstraction of Hydrogen Atoms by Energetic Recoil Tritium Atoms: Correlation with C–H Bond-Dissociation Energies in Hydrocarbons

Abstract

The yields of HT from ``hot'' abstraction reactions by energetic tritium atoms reacting with various substances RH have been measured in a large excess of C2D4. The energetic tritium atom fluxes are reasonably similar in such systems and permit comparison of absolute HT yields from different R—H bond types. A more accurate comparison is possible when the HT yields are normalized to the yields of either the hot abstraction or substitution reactions with C2D4. The hot HT yields so measured from hydrocarbons show an excellent correlation with the bond-dissociation energies of the C–H bonds involved, with higher yields from weaker bonds. The abstraction of H from CD3CH2CD3 was favored by approximately 1.4, per bond, over H from CH3CD2CH3. No significant differences were observed in the DT/C2D3T ratios from reaction with C2D4 in the various mixtures with different substances. A preference of 1.27±0.02 was observed for the abstraction of H from C2H4 vs D from C2D4. No isotopic molecule difference was observed between the energetic addition reaction of tritium atoms to the olefinic position in C2H4 vs C2D4.