title: Theoretical study on the isomerization behavior between alpha,beta-unsaturated acyl radicals and alpha-ketenyl radicals.
abstract: [reaction: see text] Ab initio calculations using 6-311G**, cc-pVDZ, aug-cc-pVDZ, and a (valence) double-zeta pseudopotential (DZP) basis set, with (QCISD, CCSD(T)) and without (UHF) the inclusion of electron correlation, and density functional methods (BHandHLYP, B3LYP) predict that alpha,beta-unsaturated acyl radicals and alpha-ketenyl radicals exist as isomers. At the CCSD(T)/cc-pVDZ//BHandHLY/cc-pVDZ level of theory, energy barriers of 15.1 and 17.7-21.7 kJ mol(-)(1) are calculated for the isomerization of s-trans-propenoyl and s-trans-crotonoyl radical to ketenylmethyl and 1-ketenylethyl radical, respectively. Similar results are obtained for the reactions of s-trans isomers involving silyl, germyl, and stannyl groups with energy barriers (DeltaE++) of 12.2-12.4, 13.1-13.9, and 12.9-18.2 kJ mol(-)(1) at the CCSD(T)/DZP//BHandHLYP/DZP calculation, respectively. These results suggest that alpha,beta-unsaturated acyl radicals and alpha-ketenyl radicals are not canonical forms but are isomeric species that can rapidly interconvert.
authors.affiliation: Department of Chemistry, Faculty of Arts and Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan. matsu@ms.cias.osakafu-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsubara
authors.forename: Ilhyong
authors.initials: I
authors.lastname: Ryu
authors.forename: Carl H
authors.initials: CH
authors.lastname: Schiesser