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Arrhenius parameters for the alkoxy radical decomposition reactions
Author(s) -
Choo Kwang Yul,
Benson Sidney W.
Publication year - 1981
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550130907
Subject(s) - chemistry , arrhenius equation , radical , alkoxy group , decomposition , arrhenius plot , alkyl , reaction rate constant , activation energy , hammett equation , photochemistry , ionization , medicinal chemistry , computational chemistry , organic chemistry , kinetics , ion , physics , quantum mechanics
Arrhenius parameters for the decomposition reactions of various alkoxy radicals are evaluated. The recommended values for tert ‐butoxy radical decomposition reaction are log A (s −1 ) = 14.1, E a = 15.3 kcal/mol.The parameters give reasonably self‐consistent results with related rate constants, product distributions of hydrocarbon oxidation reactions, and the values reported in different laboratories in different environments. A reworking of data by Batt et al. on RO + NO and RO + NO 2 leads to a lowering of his A factors for these reactions by a factor of 5. It also leads to a similar lowering of the A factors for RO decompositions. The intrinsic activation energies E for the addition of alkyl radicals R to the carbonyl group are not only found to be a function of the exothermicity of reaction, but they are also dependent on the nucleophilicity of the alkyl radicals. For each radical R (Me, Et, i ‐Pr) the data can be fit to an Evans–Polanyi plot E = a + b (δ H ), where a uniform slope b = 0.58 can be found for all R. The intercepts a are then found to decrease nearly linearly with the decreasing ionization potential of R, namely, a = 2.1 [IP] – 6.2 (kcal/mol), with the ionization potential given in electron volts.