What is the Origin of the Contrathermodynamic Behavior in Methyl Radical Addition to Alkynes versus Alkenes?
High-level ab initio calculations of the barriers, enthalpies, and rate constants have been performed for methyl radical addition to ethyne, propyne, ethene, and propene. We find that addition to alkenes is kinetically favored over addition to alkynes, despite the larger exothermicity of the alkyne addition reactions. The results have been rationalized using the curve-crossing model. To this end, the singlet-triplet gaps and charge-transfer energies in the reactants, and the extent of charge...[Show more]
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|Source:||Journal of Physical Chemistry A|