Bond dissociation energies and radical stabilization energies associated with substituted methyl radicals

Henry, D, Parkinson, C, Mayer, P and Radom, L 2001, 'Bond dissociation energies and radical stabilization energies associated with substituted methyl radicals', Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory, vol. 105, no. 27, pp. 6750-6756.


Document type: Journal Article
Collection: Journal Articles

Title Bond dissociation energies and radical stabilization energies associated with substituted methyl radicals
Author(s) Henry, D
Parkinson, C
Mayer, P
Radom, L
Year 2001
Journal name Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
Volume number 105
Issue number 27
Start page 6750
End page 6756
Total pages 6
Publisher American Chemical Society
Abstract Bond dissociation energies (BDEs) and radical stabilization energies (RSEs) associated with a series of 22 monosubstituted methyl radicals (•CH2X) have been determined at a variety of levels including, CBS-RAD, G3(MP2)-RAD, RMP2, UB3-LYP and RB3-LYP. In addition, W1‘ values were obtained for a subset of 13 of the radicals. The W1‘ BDEs and RSEs are generally close to experimental values and lead to the suggestion that a small number of the experimental estimates warrant reexamination. Of the other methods, CBS-RAD and G3(MP2)-RAD produce good BDEs. A cancellation of errors leads to reasonable RSEs being produced from all the methods examined. CBS-RAD, W1‘ and G3(MP2)-RAD perform best, while UB3-LYP performs worst. The substituents (X) examined include lone-pair-donors (X = NH2, OH, OCH3, F, PH2, SH, Cl, Br and OCOCH3), π-acceptors (X = BH2, CHCH2, CCH, C6H5, CHO, COOH, COOCH3, CN and NO2) and hyperconjugating groups (CH3, CH2CH3, CF3 and CF2CF3). All substituents other than CF3 and CF2CF3 result in radical stabilization, with the vinyl (CHCH2), ethynyl (CCH) and phenyl (C6H5) groups predicted to give the largest stabilizations of the π-acceptor substituents examined and the NH2 group calculated to provide the greatest stabilization of the lone-pair-donor groups. The substituents investigated in this work stabilize methyl radical centers in three general ways that delocalize the odd electron: π-acceptor groups (unsaturated substituents) delocalize the unpaired electron into the π-system of the substituent, lone-pair-donor groups (heteroatomic substituents) bring about stabilization through a three-electron interaction between a lone pair on the substituent and the unpaired electron at the radical center, while alkyl groups stabilize radicals via a hyperconjugative mechanism. Polyfluoroalkyl substituents are predicted to slightly destabilize a methyl radical center by inductively withdrawing electron density from the electron-deficient radical center.
DOI - identifier 10.1021/jp010442c
Copyright notice © Copyright 2008 Elsevier B.V., All rights reserved.
ISSN 1089-5639
Versions
Version Filter Type
Citation counts: Scopus Citation Count Cited 217 times in Scopus Article | Citations
Altmetric details:
Access Statistics: 220 Abstract Views  -  Detailed Statistics
Created: Mon, 09 Aug 2010, 09:02:12 EST by Catalyst Administrator
© 2014 RMIT Research Repository • Powered by Fez SoftwareContact us