The cyclizations of two structurally similar 2-oxo-5-hexenyl-type radicals have been investigated by ab initio and density functional (UB3LYP/6-31+G**//UHF/6-31G* and UB3LYP/6-31G*//UB3LYP/6-31G*) calculations. The origin of apparently contradictory reports of 6-endo and 5-exo cyclizations is determined. Kinetic control favors 6-endo cyclization, while thermodynamic control gives 5-exo cyclizat...

Interaction of proline with gold cluster was studied using density functional theory (DFT). Two types of mixed basis sets UB3LYP/6-311++G ∪ LANL2MB and UB3LYP/6-311++G ∪ LANL2DZ were used for optimization of complex structures. Proline interacts with gold cluster either through one anchor bond, N–Au or an anchor bond O–Au associated with a non-conventional O–H. . . Au hydrogen bond. Among these...

Selected synthesized natural and natural-like hydroxylated biphenyls (dimers) and their corresponding monomers (dehydrozingerone, zingerone and ferulic acid) were tested experimentally for their capacity both as radical scavengers and chain-breaking antioxidants in individual and binary mixture with α-tocopherol. Quantum-chemical calculations at the UB3LYP/6-13+G(d,p) level were used to get ful...

Lower chlorinated polychlorinated biphenyls (PCBs) are readily metabolized via hydroxylated metabolites to reactive PCB quinones. Although these PCB metabolites elicit biochemical changes by mechanisms involving cellular target molecules, such as the aryl hydrocarbon receptor, and toxicity by interacting with enzymes like topoisomerases, only few PCB quinones have been synthesized and their con...

Electronic structure calculations at the CASSCF and UB3LYP levels of theory with the aug-cc-pVDZ basis set were used to characterize structures, vibrational frequencies, and energies for stationary points on the ground state triplet and singlet O(2)+C(2)H(4) potential energy surfaces (PESs). Spin-orbit couplings between the PESs were calculated using state averaged CASSCF wave functions. More a...

Dicyanofuroxan is a new and interesting high explosive that can be used instead of some classical explosives. The present density functional treatment considers dicyanofuroxan its ring opened dinitroso isomer. has been based on theory at the level UB3LYP/6-311++G(d,p). Within constraints basis set employed results indicated form electronically more stable thermodynamically favored compared to r...

We have theoretically investigated the effect of doping in oligothiophenes (Tn, n=2-8) with the DFT method at UB3LYP level with 6-31G(d) basis set. Our attention focused on the study of the geometrical and electronic properties in the neutral and doped states. We show that the doping process modify both bond lengths and torsion angles and also electronic properties by enhancing the planarity an...

Phellandrenes are naturally occurring cyclic dienes belonging to monoterpene class and have many medicinal applications. In the present study, some resonance stabilized radicals from α- β-phellandrene also closed shell structures those been investigated within constraints of density functional theory basis set employed. For structure optimizations closed-shell open-shell structures, B3LYP/6-311...

The addition and abstraction reactions of OH radical with benzoate anion are investigated by density functional theory calculations that include solvent effects using UB3LYP, UCAM-B3LYP, UmPW1PW91 and UM06-2X functionals with the 6-311++G(2d,2p) basis set. Geometry optimizations of the reactants, products and transition state species are performed for the possible reaction paths. For the additi...