The rate constants for the homolytic alkylation of protonated heteroaromatic bases (quinoline, pyridine, and 4-cyano-, 4-acetyl-, 4-methyl-, and 4-methoxypyridine) by n-butyl and tert-butyl radicals were measured at 57 °C by competition of the aromatic addition with the alkyl radical oxidation by Cu2+ salts (for which the rates are known). With the more activated substrates (quinoline and 4-cyano- and 4-acetylpyridine) the tert-butyl radical is significantly more reactive than the n-butyl radical, clearly showing that polar effects are more important than steric and enthalpic effects in determining the reaction rates. The reversibility of the alkylation by the tert-butyl radical is discussed. © 1980, American Chemical Society. All rights reserved.

Nucleophilic Character of the Alkyl Radicals. 19.la Absolute Rate Constants in the Homolytic Alkylation of Protonated Heteroaromatic Bases by n -Butyl and tert-Butyl Radicals

Citterio, Attilio;Minisci, Francesco;
1980-01-01

Abstract

The rate constants for the homolytic alkylation of protonated heteroaromatic bases (quinoline, pyridine, and 4-cyano-, 4-acetyl-, 4-methyl-, and 4-methoxypyridine) by n-butyl and tert-butyl radicals were measured at 57 °C by competition of the aromatic addition with the alkyl radical oxidation by Cu2+ salts (for which the rates are known). With the more activated substrates (quinoline and 4-cyano- and 4-acetylpyridine) the tert-butyl radical is significantly more reactive than the n-butyl radical, clearly showing that polar effects are more important than steric and enthalpic effects in determining the reaction rates. The reversibility of the alkylation by the tert-butyl radical is discussed. © 1980, American Chemical Society. All rights reserved.
1980
Organic Chemistry, Free Radicals, Alkylation, Heteroaromatic Bases, Absolute Rate Constants.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1047400
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