Kinetic solvent effects on hydrogen abstraction from phenol by the cumyloxyl radical. Toward an understanding of the role of protic solvents

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DOIResolve DOI: http://doi.org/10.1021/jo201454c
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TypeArticle
Journal titleThe Journal of Organic Chemistry
ISSN0022-3263
1520-6904
Volume77
Issue3
Pages12671272; # of pages: 6
AbstractA time-resolved kinetic study of the hydrogen atom abstraction reactions from phenol by the cumyloxyl radical (CumO•) was carried out in different solvents. The hydrogen atom abstraction rate constant (kH) was observed to decrease by almost 3 orders of magnitude on going from isooctane to MeOH. In TFE, MeCN/H2O 2:1, and MeOH, the measured kH values were lower than expected on the basis of the Snelgrove–Ingold (SI) equation that correlates log kH to the solvent hydrogen bond acceptor (HBA) ability parameter β2H. As these solvents also act as hydrogen bond donors (HBDs), we explored the notion that a more thorough description of solvent effects could be provided by including a solvent HBD ability term, α2H, into the SI equation via β2H(1 + α2H). The inclusion of such a term greatly improves the fitting for TFE, MeCN/H2O 2:1, and MeOH but at the expense of that for tertiary alkanols. This finding suggests that, for the reaction of CumO• with phenol, the HBA and HBD abilities of both the solvent and the substrate could be responsible for the observed KSEs. but this requires that primary and tertiary alkanols exhibit different solvation behaviors. Possible explanations for this different behavior are explored.
Publication date
LanguageEnglish
AffiliationNational Institute for Nanotechnology; National Research Council Canada
Peer reviewedYes
NPARC number21269037
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Record identifier1c2ac6b8-6f0f-42b8-8a98-f6610607556f
Record created2013-12-02
Record modified2016-05-09
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