Homolytic Bond Dissociation Enthalpies of the C−H Bonds Adjacent to Radical Centers
摘要:
Homolytic bond dissociation enthalpies (BDEs) at 0 and 298 K of the C-H bonds adjacent to various radical centers have been obtained from ab initio CBS-4 (complete basis set) model calculations and experimental data available in the literature. The BDEs of the C-H bonds adjacent to the radical centers derived from 11 saturated hydrocarbons were found to be 33.5 +/- 3 kcal/mol at 298 K. The BDEs of the C-H bonds adjacent to nine allylic and benzylic radical centers were found to be 48 +/- 3 kcal/mol at 298 K, but the benzylic C-H BDE of the PhCH2CH2. radical was found to be only 29.7 and 30.5 kcal/mol at 0 and 298 K, respectively. The BDEs of the vinylic C-H bonds adjacent to four vinylic radical centers were found to be 35.5 +/- 3.5 kcal/mol at 298 K. The BDEs of the vinylic C-H bonds adjacent to three allylic radical centers were found to be 56.5 +/- 3 kcal/mol at 298 K. These results suggest that the radical centers weaken the adjacent C-H bond strengths by about 50-70 kcal/mol. The calculated BDEs agree within +/-2 kcal/mol with most of the available experimental results. Isomerization enthalpies of butenes and pentenes have been obtained. Substituent effects on BDEs have also been examined.
Experimental study and kinetic modeling of propene oxidation in a jet stirred flow reactor
作者:P. Dagaut、M. Cathonnet、J. C. Boettner
DOI:10.1021/j100314a019
日期:1988.2
Homolytic Bond Dissociation Enthalpies of the C−H Bonds Adjacent to Radical Centers
作者:Xian-Man Zhang
DOI:10.1021/jo971768d
日期:1998.3.1
Homolytic bond dissociation enthalpies (BDEs) at 0 and 298 K of the C-H bonds adjacent to various radical centers have been obtained from ab initio CBS-4 (complete basis set) model calculations and experimental data available in the literature. The BDEs of the C-H bonds adjacent to the radical centers derived from 11 saturated hydrocarbons were found to be 33.5 +/- 3 kcal/mol at 298 K. The BDEs of the C-H bonds adjacent to nine allylic and benzylic radical centers were found to be 48 +/- 3 kcal/mol at 298 K, but the benzylic C-H BDE of the PhCH2CH2. radical was found to be only 29.7 and 30.5 kcal/mol at 0 and 298 K, respectively. The BDEs of the vinylic C-H bonds adjacent to four vinylic radical centers were found to be 35.5 +/- 3.5 kcal/mol at 298 K. The BDEs of the vinylic C-H bonds adjacent to three allylic radical centers were found to be 56.5 +/- 3 kcal/mol at 298 K. These results suggest that the radical centers weaken the adjacent C-H bond strengths by about 50-70 kcal/mol. The calculated BDEs agree within +/-2 kcal/mol with most of the available experimental results. Isomerization enthalpies of butenes and pentenes have been obtained. Substituent effects on BDEs have also been examined.