Relative reactivities of substituted phenyl radicals in elementary reactions

Migita, Toshihiko; Takayama, Kiyoshige; Abe, Yoichi; Kosugi, Masanori

doi:10.1039/p29790001137

Cited by 29 publications

(29 citation statements)

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“…For example, thiomethyl abstraction has been observed to occur three times faster for para -nitrodehydrobenzene than dehydrobenzene in solution. 146 …”

Section: Properties and Reactivitymentioning

confidence: 99%

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

et al. 2013

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“…For example, thiomethyl abstraction has been observed to occur three times faster for para -nitrodehydrobenzene than dehydrobenzene in solution. 146 …”

Section: Properties and Reactivitymentioning

confidence: 99%

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

et al. 2013

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“…Previous studies have shown that substituents can influence the reactivities of aryl radicals in solution 18,19,20. For example, a solution study of hydrogen-atom abstraction by several different aryl radicals from nineteen different hydrogen-atom donors, including various hydrocarbons, acetone, methyl acetate, thiophenol, cyclohexane, and toluene, showed the reactivity ordering: p -tolyl radical < phenyl radical < p -bromophenyl radical < p -nitrophenyl radical 18.…”

Section: Introductionmentioning

confidence: 99%

Correlation of Hydrogen-Atom Abstraction Reaction Efficiencies for Aryl Radicals with their Vertical Electron Affinities and the Vertical Ionization Energies of the Hydrogen-Atom Donors

2008

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The factors that control the reactivities of aryl radicals toward hydrogen-atom donors were studied by using a dual-cell Fourier-transform ion cyclotron resonance mass spectrometer (FT – ICR). Hydrogen-atom abstraction reaction efficiencies for two substrates, cyclohexane and isopropanol, were measured for twenty-three structurally different, positively-charged aryl radicals, which included dehydrobenzenes, dehydronaphthalenes, dehydropyridines, and dehydro(iso)quinolines. A logarithmic correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) vertical electron affinities (EA) of the aryl radicals. Transition state energies calculated for three of the aryl radicals with isopropanol were found to correlate linearly with their (calculated) EAs. No correlation was found between the hydrogen-atom abstraction reaction efficiencies and the (calculated) enthalpy changes for the reactions. Measurement of the reaction efficiencies for the reactions of several different hydrogen-atom donors with a few selected aryl radicals revealed a logarithmic correlation between the hydrogen-atom abstraction reaction efficiencies and the vertical ionization energies (IE) of the hydrogen-atom donors, but not the lowest homolytic X – H (X = heavy atom) bond dissociation energies of the hydrogen-atom donors. Examination of the hydrogen-atom abstraction reactions of twenty-nine different aryl radicals and eighteen different hydrogen-atom donors showed that the reaction efficiency increases (logarithmically) as the difference between the IE of the hydrogen-atom donor and the EA of the aryl radical decreases. This dependence is likely to result from the increasing polarization, and concomitant stabilization, of the transition state as the energy difference between the neutral and ionic reactants decreases. Thus, the hydrogen-atom abstraction reaction efficiency for an aryl radical can be “tuned” by structural changes that influence either the vertical EA of the aryl radical or the vertical IE of the hydrogen atom donor.

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“…Aromatic carbon-centered σ-type mono- and biradicals have been studied extensively both in solution [3–5] and in the gas phase [6–8] because of their roles in nonhydrolytic DNA cleavage. In our laboratory, the reactivity of aromatic mono-, bi-, and triradicals (particularly phenyl radicals) has been studied in the gas phase by using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR) [9–12].…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Reactivity of the Three Distonic Isomers of the Pyridine Radical Cation Toward Tetrahydrofuran in Solution and in the Gas Phase

Widjaja

Jin

Nash

et al. 2013

J. Am. Soc. Mass Spectrom.

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The reactivity of the three distonic isomers of the pyridine radical cation toward tetrahydrofuran is compared in solution and in the gas phase. In solution, the distonic ions were generated by UV photolysis at 300 nm from iodo-precursors in acidic 50:50 tetrahydrofuran/water solutions. In the gas phase, the ions were generated by collisionally activated dissociation (CAD) of protonated iodo-precursors in an FT-ICR mass spectrometer, as described in the literature. The same major reaction, hydrogen atom abstraction, was observed in solution and in the gas phase. Attempts to cleave the iodine atom from the 2-iodopyridinium cation in the gas phase and in solution yielded the 2-pyridyl cation in addition to the desired 2-dehydropyridinium cation. In the gas phase, this ion was ejected prior to the examination of the desired ion’s chemical properties. This was not possible in solution. This study suggests that solvation effects are not significant for radical reactions of charged radicals. On the other hand, the even-electron ion studied, the 2-pyridyl cation, shows substantial solvation effects. For example, in solution, the 2-pyridyl cation forms a stable adduct with tetrahydrofuran, whereas in the gas phase, only addition/elimination reactions were observed.

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Relative reactivities of substituted phenyl radicals in elementary reactions

Cited by 29 publications

References 0 publications

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

Correlation of Hydrogen-Atom Abstraction Reaction Efficiencies for Aryl Radicals with their Vertical Electron Affinities and the Vertical Ionization Energies of the Hydrogen-Atom Donors

Comparison of the Reactivity of the Three Distonic Isomers of the Pyridine Radical Cation Toward Tetrahydrofuran in Solution and in the Gas Phase

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