“…We have therefore used the rearrangement rate of substituted methylenecyclopropanes 16 as a quantitative measure of the ability of substituents to stabilize the biradical 17. [17][18][19][20][21][22][23][24][25][26] This Account will summarize these radical-stabilizing effects that we have discovered and will discuss some of the most effective radical stabilizers, which we have termed "super radical stabilizers". 24…”
Section: Introductionmentioning
confidence: 99%
“…These substituent effects give a quantitative measure of radical-stabilizing abilities of various groups on carbon-centered free radicals. We have therefore used the rearrangement rate of substituted methylenecyclopropanes 16 as a quantitative measure of the ability of substituents to stabilize the biradical 17 . − This Account will summarize these radical-stabilizing effects that we have discovered and will discuss some of the most effective radical stabilizers, which we have termed “super radical stabilizers” 1 Evolving 1 H NMR spectra during rearrangement of 16 (Ar = p -F-C 6 H 4 ) at 80 °C in C 6 D 6 .…”
A comprehensive series of substituted 1,1-dimethyl-2-methylenecyclopropanes have been thermally rearranged. These rearrangements proceed via singlet biradical intermediates that can be stabilized by substituents. Rates are greatly enhanced by certain groups that are termed super radical stabilizers. Substituents included 4-pyridyl N-oxide, 2-(1,6-methano[10]annulenyl), and a number of anion-substituted phenyl groups. Simple valence bond theory, as well as more sophisticated computational studies, gives insights into modes of radical stabilization.
“…We have therefore used the rearrangement rate of substituted methylenecyclopropanes 16 as a quantitative measure of the ability of substituents to stabilize the biradical 17. [17][18][19][20][21][22][23][24][25][26] This Account will summarize these radical-stabilizing effects that we have discovered and will discuss some of the most effective radical stabilizers, which we have termed "super radical stabilizers". 24…”
Section: Introductionmentioning
confidence: 99%
“…These substituent effects give a quantitative measure of radical-stabilizing abilities of various groups on carbon-centered free radicals. We have therefore used the rearrangement rate of substituted methylenecyclopropanes 16 as a quantitative measure of the ability of substituents to stabilize the biradical 17 . − This Account will summarize these radical-stabilizing effects that we have discovered and will discuss some of the most effective radical stabilizers, which we have termed “super radical stabilizers” 1 Evolving 1 H NMR spectra during rearrangement of 16 (Ar = p -F-C 6 H 4 ) at 80 °C in C 6 D 6 .…”
A comprehensive series of substituted 1,1-dimethyl-2-methylenecyclopropanes have been thermally rearranged. These rearrangements proceed via singlet biradical intermediates that can be stabilized by substituents. Rates are greatly enhanced by certain groups that are termed super radical stabilizers. Substituents included 4-pyridyl N-oxide, 2-(1,6-methano[10]annulenyl), and a number of anion-substituted phenyl groups. Simple valence bond theory, as well as more sophisticated computational studies, gives insights into modes of radical stabilization.
“…56789and others5-9 have been interested in the quantitative ability of various groups to stabilize (or destabilize) free radicals in the absence of polar effects, in this regard, we have studied the thermal methylenecyclopropane rearrangement of 4 to 5 as a probe for stabilizing effects of various groups on a benzylic radical center. [2][3][4] This rear- PMO…”
“…The captodative effect of radical stabilisation and the influence of the substituents attached to the reaction centre containing an unpaired electron were analysed from the additivity standpoint. 166 The comparison of the calculated E RS values with the known scales demonstrated a relatively good quantitative agreement with the I AO parameters for 3-and 9-substituted fluorenes and 4-substituted phenylacetonitriles, 148 with the relative constant of the thermal rearrangement of 3-aryl-2,2-dimethylmethylenecyclopropanes 57,82,83 and a-spin density in 4-substituted benzyl radicals. 114 Within the framework of this approach, it was found that the radical-stabilisation effect markedly increases on passing from F-to O-and N-containing substituents.…”
Section: Calculation Of the Energies Of Stabilisation Of Radical Centresmentioning
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
