Kinetic applications of electron paramagnetic resonance spectroscopy. 38. Rearrangement of β-(acyloxy)alkyl and β-(benzoyloxy)alkyl radicals

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DOIResolve DOI: http://doi.org/10.1021/ja00380a014
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TypeArticle
Journal titleJournal of the American Chemical Society
ISSN0002-7863
Volume104
Issue16
Pages43994403; # of pages: 5
AbstractRate constants for the free-radical rearrangement, RC(O)OCMe2CH2 → RC(O)OCH2CMe2, and for the ring-opening reaction, RĊOCH2CMe2O → RC(O)OCH2ĊMe2, have been measured by kinetic EPR spectroscopy. In hydrocarbon solvents at 75°C with R = methyl and phenyl, the 1,2-acyloxy migrations are slower (k = 5.1 × 102 s-1 and 2.5 × 102 s-1, respectively) than the corresponding 1,3-dioxolan-2-yl ring openings (k = 7.6 × 103 s-1 and 1.0 × 103 s-1, respectively). The formation of a 1,3-dioxolan-2-yl radical as an intermediate in these two rearrangements could not, therefore, be ruled out. However, with R = cyclopropyl, the rearrangement proceeded normally (k ≈ 1.2 × 102 s-1 at 75°C), but the corresponding 1,3-dioxolan-2-yl radical underwent opening of the cyclopropyl ring rather than the dioxolanyl ring. Since this process occurred at a much faster rate (k = 8.7 × 105 s-1 at 75°C) than the rearrangement, the dioxolanyl radical cannot, in this case at least, be an intermediate in this acyloxy migration. The possible role of charge separation in the transition state for acyloxy migration is considered. © 1982 American Chemical Society.
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LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21276770
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Record identifier8b1c3293-82fe-4819-a25e-0e85e0060b6d
Record created2015-10-13
Record modified2016-05-09
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