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Mazzonna M, Bietti M, DiLabio GA, et al. Importance of π-stacking interactions in the hydrogen atom transfer reactions from activated phenols to short-lived N-oxyl radicals. J Org Chem. 2014;79(11):5209-18doi: 10.1021/jo500789v.
Mazzonna, M., Bietti, M., DiLabio, G. A., Lanzalunga, O., & Salamone, M. (2014). Importance of π-stacking interactions in the hydrogen atom transfer reactions from activated phenols to short-lived N-oxyl radicals. The Journal of organic chemistry, 79(11), 5209-18. https://doi.org/10.1021/jo500789v
Mazzonna, Marco, et al. "Importance of π-stacking interactions in the hydrogen atom transfer reactions from activated phenols to short-lived N-oxyl radicals." The Journal of organic chemistry vol. 79,11 (2014): 5209-18. doi: https://doi.org/10.1021/jo500789v
Mazzonna M, Bietti M, DiLabio GA, Lanzalunga O, Salamone M. Importance of π-stacking interactions in the hydrogen atom transfer reactions from activated phenols to short-lived N-oxyl radicals. J Org Chem. 2014 Jun 06;79(11):5209-18. doi: 10.1021/jo500789v. Epub 2014 May 09. PMID: 24784172.
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J Org Chem. 2014 Jun 06;79(11):5209-18. doi: 10.1021/jo500789v. Epub 2014 May 09.

Importance of π-stacking interactions in the hydrogen atom transfer reactions from activated phenols to short-lived N-oxyl radicals.

The Journal of organic chemistry

Marco Mazzonna, Massimo Bietti, Gino A DiLabio, Osvaldo Lanzalunga, Michela Salamone

Affiliations

  1. Dipartimento di Chimica and Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma , P.le A. Moro, 5, I-00185 Rome, Italy.

PMID: 24784172 DOI: 10.1021/jo500789v

Abstract

A kinetic study of the hydrogen atom transfer from activated phenols (2,6-dimethyl- and 2,6-di-tert-butyl-4-substituted phenols, 2,2,5,7,8-pentamethylchroman-6-ol, caffeic acid, and (+)-cathechin) to a series of N-oxyl radical (4-substituted phthalimide-N-oxyl radicals (4-X-PINO), 6-substituted benzotriazole-N-oxyl radicals (6-Y-BTNO), 3-quinazolin-4-one-N-oxyl radical (QONO), and 3-benzotriazin-4-one-N-oxyl radical (BONO)), was carried out by laser flash photolysis in CH3CN. A significant effect of the N-oxyl radical structure on the hydrogen transfer rate constants (kH) was observed with kH values that monotonically increase with increasing NO-H bond dissociation energy (BDENO-H) of the N-hydroxylamines. The analysis of the kinetic data coupled to the results of theoretical calculations indicates that these reactions proceed by a hydrogen atom transfer (HAT) mechanism where the N-oxyl radical and the phenolic aromatic rings adopt a π-stacked arrangement. Theoretical calculations also showed pronounced structural effects of the N-oxyl radicals on the charge transfer occurring in the π-stacked conformation. Comparison of the kH values measured in this study with those previously reported for hydrogen atom transfer to the cumylperoxyl radical indicates that 6-CH3-BTNO is the best N-oxyl radical to be used as a model for evaluating the radical scavenging ability of phenolic antioxidants.

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