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Issue 4, 1994
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Entropic and enthalpic effects of 4-methoxy substitution in phenoxyl radicals

Abstract

Values of ΔH3=(–12.4 ± 1.6) kJ mol–1, ΔS3=(–18.5 ± 5.6) J K–1 mol–1 for reaction (3)(see text), corresponding to an O–H bond energy of 322.2 kJ mol–1 in 1, and to a 14.5 J K–1 mol–1 entropy loss for the CH3O–Ar (Ar = aromatic) libration in 2 relative to 1, are derived from the temperature dependence of the equilibrium constant K3, determined by EPR spectrometry in benzene–toluene media, between 251 and 304 K. These results allow, for the first time, discrimination between enthalpic and entropic effects on the rates of (O)H-atom abstraction by peroxyl radicals from 4-methoxyphenols and related species.

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Article information


J. Chem. Soc., Perkin Trans. 2, 1994, 785-787
Article type
Paper

Entropic and enthalpic effects of 4-methoxy substitution in phenoxyl radicals

M. E. J. Coronel and A. J. Colussi, J. Chem. Soc., Perkin Trans. 2, 1994, 785
DOI: 10.1039/P29940000785

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