Evaluation of the rate coefficients and arrhenius parameters of hydrogen atom transfer reactions. II. Application of the method

Abstract

The bond-strength-bond-length (BSBL) method was used to estimate Arrhenius parameters and rate coefficients for various hydrogen atom transfer reactions of the type A + BC -AB + C. In most cases predicted activation energies agreed within 1.2 kcal/mol with the experimental values (average error = 1.12 and standard deviation = 1.42), and the calculated log A agreed within 0.55 log units with the literature data (average error = 0.47 and standard deviation = 0.57). Predicted activated complex properties were shown to agree very well with potential energy surface properties obtained from ab initio quantum mechanical calculations. Detailed comparison of the BSBL results and the results of bond-energy-bond-order (BEB0)-type calculations are presented.

Reactions and Kinetics of Unsaturated C2 Hydrocarbon Radicals

“…In a rather complex system consisting of the photolysis of C 2 H 3 I as the radical source, the fractional decrease in formation of C 2 H 4 product in the presence of added O 2 , HCl, and C 2 H 6 could be predicted if k 20 were known . A value of k 20 = (1.0 ± 0.4) × 10 -11 cm 3 molecule -1 s -1 was obtained, which is in excellent agreement with the earlier value …”

DNA Damage Induced via 5,6-Dihydrothymid-5-yl in Single-Stranded Oligonucleotides

“…The observed KIE is also smaller than one might expect if an alkoxyl radical was the species responsible for hydrogen atom abstraction . The selectivity of the process implied by the absence of a KIE upon deuteration at C4‘ and C2‘ is more consistent with the involvement of a peroxyl radical than a more reactive alkoxyl radical. , Finally, while the magnitude of the observed KIE could be considered low for hydrogen atom abstraction by a peroxyl radical, one must realize that the observed KIE in this experiment is a weighted average of the true KIE for the process, multiplied by the fraction of total product (strand break) measured that is attributable to this pathway 30e. Alternate reactive species and/or pathways would result in a reduction of the observed KIE for a process involving 35 .…”

Estimating the Activation Energy for Hydrogen Abstraction Reactions by a Combination of Semiempirical Calculation and Family Correlation

“…Thus, the experimentally determined the E a values available in the literature are limited. Consequently, many methods have been developed to estimate the E a values for hydrogen abstraction reactions on the basis of empirical, − semiempirical, − or theoretical − studies. Recently, the methods used in these studies have been reviewed by Marston et al and Denisov…”