Correlation of activation energies of radical–molecule metathesis reactions with enthalpic, polar, and steric parameters

Abstract

It is shown that the activation energies E OF chlorine atom abstraction by cyclohexyl radicals and hydrogen atom abstraction by C1 atoms from polychloroalkanes can be correlated with the bond dissociation energies D and the Taft polar and steric substituent constants u* and E , by the expression:where I ! & and ALI represent the differences between the E and D values of a given substrate and those of a reference compound (CHB substituted substrate) and a, p, and 6 are the corresponding correlation coefficients. The use of this expression allows quantitative evaluation of the relative contribution of the various factors affecting the activation energies of these reactions and estimation of related thermochemical data.

Cl‐atom transfer from CFCl3 to the c‐C6H11 radical. An indirect estimation of the CFCl2Cl bond dissociation energy

“…Furthermore, CCll (X=C1) and CFCh (X=F) have almost equal (T* values, 2.96 and 3.08, respectively. Therefore the difference in Ecl of 1.9 kcal/mol, which is primarily responsible for the markedly reduced re- [12] and [17]. Average values from the present work.…”

“…Using the correlation in eq. (I), Katz and Rajbenbach [12] have shown that for the series of C1transfer reactions of c -CsH11 radicals with chloromethanes and chloroethanes, having the general form CC13X, the activation energy difference AEcl is given by…”

Free‐radical chain dechlorination of chloroethanes in liquid triethylsilane

“…This behavior differs from the behavior observed in the C1-transfer reactions of cyclohexyl radicals [2]. There the A factors are practically constant so that the reactivity trends reflect the effect of structural parameters on the activation energy of the reaction [21]. It is worth noting, however, that despite this difference, the logarithms of the rate constants of the C1-transfer reaction of EtySi and c-C6Hll radicals are linearly dependent.…”

Performance enhancement of single layer organic light-emitting diodes using chlorinated indium tin oxide as the anode

“… 28 The number of Cl radicals liberated from the solvent can be explained by the bond dissociation energies. In chloroform, o -DCB and chlorobenzene molecules, the bond dissociation energies of C–Cl bonds are 318.8 kJ mol −1 , 40 385.8 kJ mol −1 41 and 399.6 kJ mol −1 , 42 respectively. Therefore, the Cl radicals in chloroform were most easily extracted from the solvent under the same UV ozone conditions, while Cl radicals were the most difficult to liberate from chlorobenzene.…”