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

Coronel, Marta E. J. and Colussi, Agustin J. (1994) Entropic and enthalpic effects of 4-methoxy substitution in phenoxyl radicals. Journal of the Chemical Society. Perkin Transactions 2, 1994 (4). pp. 785-787. ISSN 0300-9580.

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Values of ΔH_3=(–12.4 ± 1.6) kJ mol^(–1), ΔS_3=(–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 CH_3O–Ar (Ar = aromatic) libration in 2 relative to 1, are derived from the temperature dependence of the equilibrium constant K_3, 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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Colussi, Agustin J.0000-0002-3400-4101
Additional Information:© 1994 Royal Society of Chemistry. Paper 3/06906K. Received 19th November 1993; Accepted 10th December 1993.
Issue or Number:4
Record Number:CaltechAUTHORS:20150623-154805203
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58511
Deposited By: George Porter
Deposited On:25 Jun 2015 22:47
Last Modified:03 Oct 2019 08:36

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