34386-95-3Relevant academic research and scientific papers
Spectral properties and absolute rate constants for β-scission of ring-substituted cumyloxyl radicals. A laser flash photolysis study
Baciocchi, Enrico,Bietti, Massimo,Salamone, Michela,Steenken, Steen
, p. 2266 - 2270 (2007/10/03)
A laser flash photolysis study of the spectral properties and β-scission reactions of a series of ring-substituted cumyloxyl radicals has been carried out. All cumyloxyl radicals display a broad absorption band in the visible region of the spectrum, which decays on the microsecond time scale, leading to a strong increase in absorption in the UV region of the spectrum, which is attributed to the corresponding acetophenone formed after β-scission of the cumyloxyl radicals. The position of the visible absorption band is red-shifted by the presence of electron-donating ring substituents, while a blue-shift is observed in the presence of electron-withdrawing ring substituents, suggesting that + R ring substituents promote charge separation in the excited cumyloxyl radical through stabilization of the partial positive charge on the aromatic ring of an incipient radical zwitterion. Along this line, an excellent Hammett-type correlation between the experimentally measured energies at the visible absorption maxima of the cumyloxyl radicals and σ+ substituent constants is obtained. A red-shift is also observed on going from MeCN to MeCN/H2O for all cumyloxyl radicals, pointing toward a specific effect of water. The ring substitution does not influence to a significant extent the rate constants for β-scission of the cumyloxyl radicals, which varies between 7.1 × 105 and 1.1 × 106 s-1, a result that suggests that cumyloxyl radical β-scission is not governed by the stability of the resulting acetophenone. Finally, κβ increases on going from MeCN to the more polar MeCN/H2O 1:1 for all cumyloxyl radicals, an observation that reflects the increased stabilization of the transition state for β-scission through increased solvation of the incipient acetophenone product.
Steric and Electronic Substituent Effects in Tertiary Alkyl Peroxide Decompositions
Hendrickson, William H.,Nguyen, Chi C.,Nguyen, Jackie T.,Simons, Kim T.
, p. 7217 - 7220 (2007/10/02)
Rate constants for the homolysis of aryl- substituted α-cumyl tert-butyl peroxides (X-PhCMe2OOCMe3) produce a Hammett plot with a ρ value of -0.22 +/- .04.Both steric and electronic parameters influence the decomposition rate constants of tertiary alkyl peroxides with bulky substituents: log krel = (-0.40 +/- .08)Σ?* - (0.43 +/- .02)ΣEsc.
HALOGEN-CONTAINING ALKYL AROMATIC PEROXIDES
Vilenskaya, M. R.,Petrovskaya, G. A.,Pokhmurskaya, M. V.
, p. 841 - 843 (2007/10/02)
New halogen-containing peroxides were obtained by alkylation of saturated, acetylenic, and vinylacetylenic hydroperoxides with p-halogen-containing alkyl aromatic alcohols in an acetic acid medium in the presence of catalytic amounts of perchloric acid.
