Absolute rate constants for some reactions of the triethylamine-boryl radical and the borane radical anion

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DOIResolve DOI: http://doi.org/10.1039/b009494n
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TypeArticle
Journal titleJ. Chem. Soc., Perkin Trans. 2
Journal of the Chemical Society, Perkin Transactions 2
Issue4
Pages480486; # of pages: 7
AbstractLaser flash photolysis (LFP) of di-tert-butyl peroxide or dicumyl peroxide at ambient temperatures in the presence of Et3N[rightward arrow]BH3 or BH4- generated the title radicals which were found to have broad, featureless absorptions in the visible region. Rate constants for H-atom abstraction from Et3N[rightward arrow]BH3 by cumyloxyl radicals show a small solvent dependence, e.g. 12[times]107 and 2.2[times]107 dm3 mol-1 s-1 in isooctane and acetonitrile, respectively. Rate constants for halogen atom abstraction by Et3N[rightward arrow]BH2[radical dot] and BH3[radical dot]- from a number of chlorides and bromides were determined by LFP and by competitive kinetics, e.g., for Et3N[rightward arrow]BH2[radical dot]+CCl4/PhCH2Cl/CH3(CH2)2Cl, k=4.4[times]109/1.1[times]107/5.1[times]105 dm3 mol-1 s-1 and for BH3[radical dot]-+CCl4/PhCH2Cl, k=2.0[times]109/3.0[times]107 dm3 mol-1 s-1. Rates of addition of Et3N[rightward arrow]BH2[radical dot] to 1- and 1,1-substituted olefins increase dramatically as the electron affinity of the olefin increases, confirming the nucleophilic character of amine-boryl radicals. A comparison of the present results with literature data for the addition of olefins of four nucleophilic carbon-centered radicals proves that Et3N[rightward arrow]BH2[radical dot] is by far the most nucleophilic radical for which kinetic data are available. A few rate constants for abstraction of hydrogen from electron-deficient carbon by Et3N[rightward arrow]BH2[radical dot] are also reported.
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AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences
Peer reviewedNo
NPARC number12339204
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Record identifierea83ed99-4db3-444b-8a71-075eeebe83cc
Record created2009-09-11
Record modified2016-05-09
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