Kinetic applications of electron paramagnetic resonance spectroscopy. 29. Free radical chemistry of aliphatic selenium compounds

Download
  1. Get@NRC: Kinetic applications of electron paramagnetic resonance spectroscopy. 29. Free radical chemistry of aliphatic selenium compounds (Opens in a new window)
DOIResolve DOI: http://doi.org/10.1021/ja00449a012
AuthorSearch for: ; Search for:
TypeArticle
Journal titleJournal of the American Chemical Society
ISSN0002-7863
Volume99
Issue7
Pages20792084; # of pages: 6
AbstractThe reactions of a variety of aliphatic selenium compounds with free radicals have been studied by EPR spectroscopy. The methylselenyl radical, CH3Se•, could not be directly observed by EPR, probably because of extreme line broadening by spin-orbit coupling. Sterically hindered β-selenoalkyls, RnMSeĊ(CMe)2, generated by addition of RnM• radicals to di-tert-butyl selenoketone, are readily observed by EPR, but unhindered alkylselenoalkyls, such as CH3SeĊH2, could not be detected directly. This difference is attributed to conformational factors. The hindered radicals adopt a conformation in which the unpaired electron interacts only weakly with the selenium nucleus because the selenium's lone pair lies in the Cα 2pz nodal plane. The unhindered radicals adopt a conformation in which the lone pair is eclipsed by the Cα 2pz orbital and the resultant strong interaction with the selenium nucleus leads to line broadening both by a spin-rotation mechanism and by the spin-orbit mechanism. The kinetics of decay of some RnMSeĊ(CMe3)2 radicals are reported. At low temperatures these radicals exist in equilibrium with a diamagnetic dimer. The (CH3)3COSeĊ(CMe3)2 radical decays by a γ scission of the C-O bond. Dialkyl selenides readily undergo bimolecular homolytic substitution at selenium when attacked by reactive carbon-centered radicals such as C6H5•. Relative and absolute rate constants for some of these reactions have been determined. Some γ- and δ-selenoalkyls have also been identified.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21276603
Export citationExport as RIS
Report a correctionReport a correction
Record identifier752fe8ea-9e34-46ee-be2f-10f0e4298293
Record created2015-10-13
Record modified2016-05-09
Bookmark and share
  • Share this page with Facebook (Opens in a new window)
  • Share this page with Twitter (Opens in a new window)
  • Share this page with Google+ (Opens in a new window)
  • Share this page with Delicious (Opens in a new window)