부산대학교 도서관

Density functional theory was used to calculate the intrinsic reaction coordinate of hydrogen atom abstraction from a number of organic molecules of different classes by CF radical. These reactions involve the formation of stable pre- and post-reactive complexes with binding energies comparable to the activation barriers and reaction energies. An analysis of the results obtained using the dimensionless reaction coordinate showed that the generalized Polanyi-Semenov relationship E = A + 0.5Δ H + Δ H/(2 W) is fulfilled. For primary and secondary C-H bonds of esters and ketones, it reproduces the calculated activation energies with an error of at most 1 kcal mol provided A = 8.5 kcal mol and W = 43 kcal mol. The accuracy of the generalized Polanyi-Semenov relationship decreases when the enthalpy difference between the pre- and post-reactive complexes is used as the Δ H value because, as a rule, the structures of these complexes are not directly related to the structure of the transition state. [ABSTRACT FROM AUTHOR]