KINETIC ISOTOPE EFFECTS FOR HYDROGEN ABSTRACTION FROM VARIOUS SATURATED HYDROCARBONS BY DEUTERIUM ATOMS IN THE GAS PHASE.

Article abstract of DOI:10.1002/bbpc.19860900412

Using deuterium atoms produced in the radiolysis of heavy water vapor, the kinetic isotope effects k//H/k//D were determined by the isotope competitive method for the authors' abstraction reaction. The alkanes RH investigated include isobutane, 2,3,4-trimethylpentane, neopentane, cyclopentane, cyclohexane, cycloheptane, and n-heptane. The results are represented in terms of the Arrhenius-type expression k//H/k//D equals A//H/A//D exp((E//D minus E//H) (kJ mol** minus **1)/RT), over the temperature range 363-473 K. The pre-exponential factor ratios A//H/A//D vary from 0. 36 for neopentane to 0. 70 for 2,3,4-trimethylpentane, the E//D minus E//H values from 6. 4 for 2,3,4-trimethylpentane to 10. 4 kJ mol** minus **1 for neopentane. The variation in the E//D minus E//H values was correlated with the bond strength of the C-H bond being broken.