title: Remote substituent effects on homolytic bond dissociation energies.
abstract: In the study we tried to answer two questions. First, does X-Z homolytic bond dissociation energy (BDE) of Y-C6H4-X-Z obey the Hammett relationship? Second, if it does what factors determine the magnitude and sign of the slope (rho+) of Hammett regression against substituent sigma(p)(+) constants? We collected a large number of X-Z BDEs for over one-thousand Y-C6H4-X-Z systems using the RMP2/6-311++G**//UB3LYP/6-31G* method. We found that remote substituent effects on X-Z BDEs are determined by both the ground effect (i.e. stabilization/destabilization of X-Z by the substituents) and the radical effect (i.e. stabilization/destabilization of X. by the substituents). The ground or radical effect is determined by the electron demand of X-Z or X. in the same way as the deprotonation enthalpy of HOOC-C6H4-X-Z or HOOC-C6H4-X. is affected by X-Z or X. . As a result, rho+ (BDE) for X-Z bond homolysis can be quantitatively predicted by using the change in deprotonation enthalpy from HOOC-C6H4-X-Z to HOOC-C6H4-X. .
authors.affiliation: Department of Chemistry, University of Science and Technology of China, Hefei 230026, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Fu
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Bo-Lin
authors.initials: BL
authors.lastname: Lin
authors.forename: Yi
authors.initials: Y
authors.lastname: Mou
authors.forename: Yu-Hui
authors.initials: YH
authors.lastname: Cheng
authors.forename: Qing-Xiang
authors.initials: QX
authors.lastname: Guo