N-oxyl radicals of various structures were generated by oxidation of corresponding N-hydroxy compounds with iodobenzene diacetate, [bis(trifluoroacetoxy)]iodobenzene, and ammonium cerium(IV) nitrate in acetonitrile. The decay rate of N-oxyl radicals follows first-order kinetics and depends on the structure of N-oxyl radicals, reaction conditions, and the nature of the solvent and oxidant. The values of the self-decay constants change within 1.4 × 10 −4 s −1 for the 3,4,5,6-tetraphenylphthalimide-N-oxyl radical to 1.4 × 10 −2 s −1 for the 1-benzotriazole-N-oxyl radical. It was shown that the rate constants of the phthalimide-N-oxyl radicalsʼ self-decay with different electron-withdrawing or -donor substituents in the benzene ring are higher than that of the unsubstituted phthalimide-N-oxyl radical in most cases. The solvent effect on the process of phthalimide-N-oxyl radical self-decomposition was investigated. The dependence of the rate constants on the Gutmann donor numbers was shown.

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The acenaphthene oxidation with molecular oxygen in the presence of Nhydroxyphthalimide (NHPI) has been investigated. It is shown that the main oxidation product is acenaphthene hydroperoxide. The phthalimide-N-oxyl (PINO) radical has been generated in situ from its hydroxyimide parent, NHPI, by oxidation with iodobenzenediacetate. The rate constant of H-abstraction (k H ) from acenaphthene by PINO has been determined spectroscopically in acetonitrile. The kinetic isotope effect and the activation parameters have also been measured. On the basis of the results of our studies and available published literature data, a plausible mechanism for the oxidation process of acenaphthene with dioxygen catalyzed by NHPI was discussed. C 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: [515][516][517][518][519][520][521][522][523][524] 2013 Polycyclic aromatic hydrocarbons with secondary C-H bonds, for example, acenaphthenes (AcNph) are oxidized by using dioxygen to their corresponding oxygenated derivatives, naphthalic acid and naphthalic anhydride, which are used as intermediates for the synthesis of the important raw materials (such as esters, amides, and imides) for the manufacture of dyes, pharmaceuticals, pesticides, plastics, fibers, curing agents, plasticizers, pigments, fluorescent whiteners, and many other items [9]. Polynuclear hydrocarbons were oxidized during catalysis of NHPI [10], [11], but no literature report has been published on the efficient oxidation of acenaphthene except [10], where authors used the NHPI/anthraquinone system. In this paper, we have reported the kinetic study of the acenaphthene oxidation by molecular oxygen in the presence of NHPI, to better understand the mechanism of the NHPI-catalyzed aerobic oxidation of alkylbenzenes. We have described

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A model for predicting the rate constants of hydrogen atom transfer (HAT) from the α–C–H bond of p-substituted benzyl alcohols to N-oxyl radicals was proposed. To quantify the factors governing the reactivity of both N-oxyl radicals and benzyl alcohols, multivariate regression analysis was performed using various combinations of reactivity parameters. The analysis was based on a 2D array of 35 HAT reactions, the rate constants of which span 4 orders of magnitude. The proposed polyparameter equation approximates the experimental rate constants of reactions with high accuracy using three independent parameters: Brown and Okamoto’s substituent constants σ+ in alcohol molecules and the spin population on O and N atoms in the N–O• fragment of N-oxyl radicals [calculated by DFT/B3LYP/6-31G­(d,p)]. The rate constants of HAT reactions from p-substituted benzyl alcohols to a series of aryl-substituted phthalimide-N-oxyl radicals containing either electron-withdrawing or electron-donating substituents (4-Cl, 4-HOOC, 4-CH3O), quinolinimide-N-oxyl, benzotriazole-N-oxyl, and violuric acid radicals were experimentally determined at 30 °C in acetonitrile.