Next, we computed reaction energies of a set of substrates studied in prior experimental work (including diastereomers where applicable), supplemented with piperidine. Hydrogen atom transfer (HAT) reaction energy, radical rebound energy, and the fluorinated product release energy were calculated (Figure , Table ). We observe that for almost all the substrates, the HAT energies are comparable (Figure , Table ). For the substrates 1, 2, and 3, which are cyclohexane, cycloheptane, and cyclooctane, the HAT energy becomes slightly more exothermic in moving from the six-membered ring to the eight-membered ring (Figure , Table ). Comparison to rebound energies reveals that HAT energies are ten times less exothermic than rebound energies (Figure , Table ). However, for all substrates, HAT energies are more favorable compared to release energies which are strongly endothermic (Figure , Table ).