Stability of PhCH2CH2ĊHX (X = H, CF3, Me, CO2Me) Radicals

Gasanov, R. G.; Vasilieva, T. T.; Gapusenko, S. I.; Borisov, Yurii A.

doi:10.1070/mc1991v001n03abeh000068

Cited by 4 publications

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“…In this case, the experimental value is much higher than for the other reactions of this type and may require re-examination. In addition to the data in Table 3, it is noteworthy that the fragmentation rate coefficient for 1a in toluene solution is estimated as 1 Â 10 -2 s -1 at 298 K, compared with the literature value of Gasanov et al of 4 Â 10 4 s -1 at 295 K. 3 This large discrepancy greatly exceeds the estimated uncertainty in the theoretical procedures, which have recently been shown to reproduce related beta-scission reactions to within chemical accuracy, 31 and it is possible that additional reaction channels may be contributing to an overestimation of the fragmentation rate in this experimental system. Evans-Polanyi-Semenov type plots of addition, β-fragmentation and cyclization reactions in this study are shown in Figure 2.…”

Section: Articlesupporting

confidence: 57%

“…Gasanov et al, in an EPR-based study, measured the rate of β-fragmentation of 3-phenylpropyl systems to their constituent benzyl and alkene fragments. 3 The measured rate coefficients for fragmentation, k β at 298 K were 10 2 -10 4 s -1 (depending on substitution), which under some circumstances may be sufficiently fast to compete with addition rates, even in bulk monomer concentrations (ca. 10 mol L -1 ), where k add ranges from 10 1 to 10 5 M -1 s -1 (measured by laser flash photolysis, and dependent on substitution of the benzyl radical and olefin).…”

Section: ' Introductionmentioning

confidence: 99%

“…The fate of substituted 3-phenylpropyl radicals (and heteroanalogues) in the absence of viable monomers, or in dilute solutions of same has been less extensively investigated. Gasanov et al, in an EPR-based study, measured the rate of β-fragmentation of 3-phenylpropyl systems to their constituent benzyl and alkene fragments . The measured rate coefficients for fragmentation, k β at 298 K were 10 2 −10 4 s −1 (depending on substitution), which under some circumstances may be sufficiently fast to compete with addition rates, even in bulk monomer concentrations (ca.…”

Section: Introductionmentioning

confidence: 99%

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Computational Study of the Chemistry of 3-Phenylpropyl Radicals

et al. 2011

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Density functional theory (DFT) and G3-type (G3(MP2)-RAD) composite calculations were performed on a series of substituted 3-phenylpropyl radicals, to determine the relative importance of fragmentation and cyclization reactions in the chemistry of such species. Our studies indicate that cyclization is generally the more important of these reactions, with exceptions where fragmentation yields highly stabilized benzylic species. The energetic barriers for the cyclization reactions (enthalpies of activation) were found to be determined largely by the stability of the reactant radical and to a lesser but significant extent, by steric factors. Polarity effects in the transition state (modeled by SOMO-LUMO gaps of the products) appear to be less important. The data obtained indicated that the addition of benzyl radical to alkenes may be considered to be irreversible, but calculations for α-substituted styrenic systems indicate that reversibility of addition may become a factor in dilute polymerizing solutions for select systems.

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Section: Articlesupporting

confidence: 57%

Section: ' Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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