Polar transition states in reactions of aromatic hydrocarbons with hydroxyl radicals
- 22 Downloads
The mechanism of formation of radical adducts in the radical hydroxylation of aromatic hydrocarbons has been investigated. The analysis of correlations between the logarithms of the rate constants of the radical hydroxylation of substituted benzenes, naphthalenes, and condensed hydrocarbons in aqueous solutions and the σ+ constants of the substituents, the ionization potentials, the localization energies of the arenes, and also the quantum-chemical calculations of the surfaces of potential energies of the hydroxylation of benzene and naphthalene leads to the conclusion that an ion pair in the excited state, formed by the cation radical of the hydrocarbon and the hydroxyl anion, can serve as the model for the transition states of the above-mentioned reactions. A decrease in the ionization potential of the arene leads to an increase in the coulombic interaction in this pair, to its stabilization, and to an increase in the reaction rate.
KeywordsBenzene Hydrocarbon Adduct Excited State Transition State
Unable to display preview. Download preview PDF.
- 1.D. Nonhubel and J. Walton, Free Radical Chemistry [Russian translation], Mir, Moscow (1977).Google Scholar
- 2.A. K. Pikaev, Pulse Radiolysis of Water and Aqueous Solutions [in Russian], Nauka, Moscow (1965).Google Scholar
- 3.C. Walling and R. A. Johnson, “Fenton's reagent. 5. Hydroxylation and side-chain cleavage of aromatics,” J. Am. Chem. Soc., 97, No. 2, 363 (1975).Google Scholar
- 4.A. K. Pikaev and S. A. Kabakchi, Reactivity of Primary Products of the Radiolysis of Water [in Russian], Énergoizdat, Moscow (1982).Google Scholar
- 5.N. A. Vysotskaya and L. N. Bortun, “The mechanism of radiation-induced homolytic substitution of condensed aromatic hydrocarbons in aqueous solutions,” Radiat. Phys. Chem., 23, No. 6, 731 (1984).Google Scholar
- 6.K. Johnson, The Hammett Equation [Russian translation], Mir, Moscow (1977).Google Scholar
- 7.O. Yu. Okhlobystin, Electron Transfer in Organic Reactions [in Russian], Izd. Rostov. Univ, Rostov-on-Don (1974).Google Scholar
- 8.V. V. Lobanov, N. A. Vysotskaya, E. A. Rabovskaya, and V. I. Bogillo, “Investigation of radical hydroxylation of aromatic hydrocarbons by the MChPDP/3 method,” Teor. Éksp. Khim., 22, No. 1, 20 (1986).Google Scholar
- 9.S. Fukuzumi and J. K. Kochi, “Transition state barriers for electrophilic reactions,” J. Am. Chem. Soc., 104, No. 26, 7599 (1982).Google Scholar