Production and decomposition of highly excited 2‐butyl radicals by the addition of hot hydrogen atoms to but‐2‐ene. Cross section for the addition reaction

Abstract

AbstractHighly excited 2‐butyl radicals have been generated by addition of hot hydrogen atoms to but‐2‐ene. Atoms of initial energy 130 kJ mol−1 and 161 kJ mol−1 were produced by photolysis of H2S. Rates of decomposition of the highly excited 2‐butyl radicals were monitored by analysis of stabilization and decomposition products, and the extent of energy‐loss of the hydrogen atoms in nonreactive collisions assessed by measuring the effect of added xenon on product yields. A model involving the cross‐section for the addition reaction, energy transfer in nonreactive collisions between hydrogen atoms and but‐2‐ene, RRKM rate constants for decomposition of excited 2‐butyl radicals, and collisional energy transfer from the radicals, has been used to calculate product yields for comparison with experimental values. It is concluded that the cross‐section for addition of hydrogen atoms of energy about 130 kJ mol−1 to but‐2‐ene is 0.055 ± 0.028 nm2. This value is compatible with the A factor for the thermal addition reaction.