Density functional investigations of carboxyl free radicals: Formyloxyl, acetyloxyl, and benzoyloxyl radicals

摘要: The structure of the lowest electronic states HCOO· in C2v and Cs symmetries were optimized employing density functional theory (DFT) methods with extended basis sets including up to f- (on C O) d- H) polarization functions. Generalized gradient functionals (BLYP) adiabatically connected (B3LYP B3PW91) employed for studying HCOO·, as well isomer HOCO· (trans), dissociation limit H·+CO2, transition state decomposition. At best DFT levels employed, ground is 2A1 (in C2v) equal CO bond lengths, while low-lying 2B2 only about 4 kJ/mol above (without inclusion zero-point energies). broken-symmetry 2A′ (with unequal i.e., symmetry) predicted be 13 a isomerization (2A1)HOCO· (2A′), trans-HOCO· 55 more stable. These facts agree closely most recent CASPT2/ANO calculations on this system. Therefore, it concluded that some models can used safely study larger radicals same type (despite several drawbacks discussed at length study). B3PW91, using sets, subsequently applied possible reaction mechanisms acetyloxyl radical, which exhibits much complicated path than formyloxyl, due presence methyl group. optimum structures isomers coplanar or perpendicular CH bonds obtained CH3COO· two saddle points identified decomposition into CH3· CO2. On other side, CH3OCO· CH2COOH· also located, former CH3O·+CO investigated. Finally, benzoyloxyl radical (C6H5COO·) its products investigated along lines. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 253–267,