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    Determination of EPR Parameters of Gamma-Irradiated Powder Limettin Sample by Experimental and Theoretical Studies
    (Amer Inst Physics, 2018) Karakas Sarikaya, Ebru; Erdogdu, Yusuf; Dereli, Omer
    Limettiit. also known as c traptene, is a dimethoxycoumar n (DMC),(CIIH,004), easily obtained from the sediment which is deposited from the expressed oil of limes'. In this study, the Limettin sample was irradiated for about 100 kGy total dose at room temperature by a 'Co-7 ray source. As a result of this irradiation, a stable radical has been obtained. In order to determine the produced radical experimentally, the spectra were taken at 0.1-20 mW microwave power and 123-393 K spectrometer temperature intervals. And experimental g values and hfccs of radical were determined. So we have modeled eight possible radical forms from two different stable conformations with approximately the same conformation energies. g values and hfccs of the model radicals were calculated with DFT/B3LYP using the TZVP basis set. As a result we compared the experimental and theoretically calculated values. Thus, we deduced that (:1-12(C902H4)0CH3, alkyl radicals (carbon centered) which are produced by abstraction of a single hydrogen atom were formed 41 the irradiated sample.
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    Investigation of Molecular and Radical Structures of Ethylene Glycol
    (Amer Inst Physics, 2018) Dereli, Omer; Karakas Sarikaya, Ebru; Erdogdu, Yusuf
    In this study, the conformational variety of ethylene glycol molecule was theoretically searched via energy minimization calculations carried out by using the Merck Molecular Force Field (MMFF) and eight stable conformers were determined for the free molecule. For each of the found conformers, a geometry optimization calculation was performed by using the DFT/B3LYP method and 6-311++G(d, p) basis set. From these calculations some structural data of the conformers, such as optimized geometry, relative energy and dipol moment, were obtained and then they were used in evaluation of the stabilities of the investigated conformers. In the next step of the study, theoretically possible forteen radicals were derived from the most stable conformer of free ethylene glycol and geometry optimization was also performed for each of them. Afterwards, the Electron Paramagnetic Resonance (EPR) parameters of these radicals were calculated using DFT/B3LYP method and TZVP basis set and then the obtained values were compared to the corresponding experimental data reported in the literature. The results have demonstrated that the experimentally observed EPR parameters match the theoretical EPR values obtained for the model radical called here Rad 5 (COHCH2OH). The model Rad 5 is an anion radical formed by abstraction of an hydrogen atom from the neutral free molecule.
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    Molecule and Radical Structures of Isobutyronitrile
    (Gazi Univ, 2017) Dereli, Omer; Erdogdu, Yusuf; Ates, Levent; Karakas Sarikaya, Ebru; Ozturan, F. Pinar
    Molecule and radical structures of Isobutyronitrile were studied by DFT computations. Results of conformational analysis performed by combination of molecular mechanic and B3LYP/6-311++G(d, p) methods showed that isobutyronitrile inelastic molecule which has only one conformer. Using this structure, radical structure was investigated. Possible radicals were modelled and the experimental Electron Paramagnetic Resonance parameters were calculated. The calculated parameters obtained from B3LYP/TZVP computations were compared with the experimental counterparts which were taken from literature. Determined Molecule and Radical structures were given in this study.
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    Theoretical Calculations of Electron Paramagnetic Resonance parameters of Liquid Phase Orotic Acid Radical
    (Amer Inst Physics, 2017) Karakas Sarikaya, Ebru; Dereli, Omer
    To obtain liquid phase molecular structure, conformational analysis of Orotic acid was performed and six conformers were determined. For these conformations, eight possible radicals were modelled by using Density Functional Theory computations with respect to molecular structure. Electron Paramagnetic Resonance parameters of these model radicals were calculated and then they were compared with the experimental ones. Geometry optimizations of the molecule and modeled radicals were performed using Becke's three-parameter hybrid-exchange functional combined with the Lee-Yang-Parr correlation functional of Density Functional Theory and 6-311++G(d,p) basis sets in p-dioxane solution. Because Orotic acid can be mutagenic in mammalian somatic cells and it is also mutagenic for bacteria and yeast; it has been studied.
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    Theoretical Calculations of EPR Parameters of Gas Phase Hydracrylonitrile Radical
    (Amer Inst Physics, 2017) Karakas Sarikaya, Ebru; Dereli, Omer
    As a result of detailed conformational search of the hydracrylonitrile, four different conformers of molecule have been obtained. For these conformations, eleven possible radicals were modelled by using density functional theory (DFT) computations vial respect to molecular structure. Electron Paramagnetic Resonance parameters of these model radicals were calculated and then they were compared with the experimental ones. Geometry optimizations of the molecule and modeled radicals were calculated by B3LYP method using 6-311++G(d,p) basis sets in gas phase.