Homolytic bond dissociation enthalpies of the C-H bonds adjacent to radical centers

An investigation of the bond dissociation enthalpies (BDEs) of the C-H bonds adjacent to various radical centers derived from 11 saturated hydrocarbons revealed that these were 33.5 +/- 3 kcal/mol at 298 K. While the BDEs of the C-H bonds beside nine allylic and benzylic radical centers were found to be 48 +/- 3 kcal/mol at 298 K, those adjacent to the benzylic PhCH2CH2* radical was only 29.7 and 30.5 kcal/mol at 0 and 298 K, respectively. Those of vinylic C-H bonds near four vinylic and three allylic radical centers were found to be 35.5 +/- 3.5 kcal/mol and 56.5 +/- 3 kcal/mol both at 298 K, respectively.