Correlation analysis in the chemistry of free radicals

Abstract

Published data now available on the use of correlation Published data now available on the use of correlation analysis in free-radical chemistry are discussed systematically. The analysis in free-radical chemistry are discussed systematically. The scales of `radical' scales of `radical' s s-constants of substituents proposed previously -constants of substituents proposed previously are analysed. It is shown that none of them is applicable as a are analysed. It is shown that none of them is applicable as a general scale because almost in all cases, it is impossible to general scale because almost in all cases, it is impossible to separate correctly the proper radical and polar contributions to separate correctly the proper radical and polar contributions to the overall effect of substituents. A new approach to the quanti-the overall effect of substituents. A new approach to the quantitative estimation of the relationship between the structure and tative estimation of the relationship between the structure and reactivity of molecules in free-radical processes called reactivity of molecules in free-radical processes called r r 7 72 2 -analysis -analysis is proposed. The bibliography includes 238 references. is proposed. The bibliography includes 238 references.

Philicity of Acetonyl and Benzoyl Radicals: A Comparative Experimental and Computational Study

“…However, these values did not satisfactorily correlate with the reaction rates for acetonyl addition. We therefore focused on several other radical‐specific substituent parameters employed in linear free‐energy relationships . For example, kinetic measurements of model radical reactions have been used by Creary and co‐workers as well as Jiang and Ji to define the parameters σ .…”

Polar, Steric, and Stabilization Effects in Alkoxyamines C−ON Bond Homolysis: A Multiparameter Analysis

“…The main problems arose with the radical stabilization molecular descriptor (σ RS ). In fact, the Hammett constants σ U and σ R (delocalization effect) are not the most suitable to take into account the radical stabilization . A lot of work had already been done in that field but mainly on the benzylic-type compounds .…”

“…However, it gives only a rough estimation of the value of k d and is strongly dependent on the accuracy of the value of BDE(C−H). Indeed, other effects such as steric and polar effects in the ground state can bias the values of BDE (C−H). − Furthermore, we have recently shown that the correlation log k d vs BDE(C−H) for SG1 derivatives is more complicated than expected from the well-known TEMPO derivative case . To overcome these difficulties, we present hereafter an analysis following a multiparameter approach where log k d is parametrized with the molecular descriptors corresponding to the polar inductive/field − (σ U ), steric , (υ), and the stabilization (σ RS ) effects of the leaving alkyl radicals in the TEMPO− and SG1−alkoxyamine series.…”

Sequential Oxidative α-Cyanation/Anti-Markovnikov Hydroalkoxylation of Allylamines

“…According to the methylenology principle, Michael additions of alcohols at intrinsically nucleophilic CC double bonds could be mediated by linking the electron-rich π-system with an electron-accepting group through a radical center. As C-centered radicals are efficiently stabilized by captodative effects, vinyl-substituted α-amino nitriles would be ideal substrates for testing this approach.…”

“…Therefore, Michael-type addition of alcohols to the terminal C-4 may generate intermediates E , in which the negative charge is delocalized and efficiently stabilized by the electron-withdrawing cyano group. Fast proton transfer converts E to radicals F , which benefit from captodative stabilization . Deuteration at C2 in product 3a ′ was not observed (see above).…”