| Abstract | Gronert (J. Org. Chem. 2006, 71, 1209) has challenged the importance of hyperconjugation in determining C-H bond dissociation enthalpies (BDEs) in alkanes. Electron paramaganetic resonance spectra of H₃CCH₂•, (H₃C)₂CH•, and (H₃C)₃C• show significant positive spin on their β-H₃C groups' hydrogens. A 55%/45% partitioning of these spins between hyperconjugation and spin polarization mechanisms linearly correlates with the C-H BDEs in methane, ethane, propane, isobutane and propene. Hyperconjugation is an important factor determining alkane C-H BDEs. |
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