Yazar "Osmanoglu, Y. E." seçeneğine göre listele

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  • [ X ]
    Öğe
    Electron paramagnetic resonance of ?-irradiated glycyl-L-glutamine monohydrate, iminodiacetic acid and methyliminodiacetic acid
    (Taylor & Francis Ltd, 2008) Aydin, M.; Osmanoglu, Y. E.; Baskan, M. H.
    The electron paramagnetic resonances of gamma-irradiated powders of glycyl- L- glutamine monohydrate, iminodiacetic acid and methyliminodiacetic acid were investigated at room temperature. The observed species in glycyl- L- glutamine monohydrate powders were attributed to the CH2<(C)over dot>NHCOOH radical; and those in iminodiacetic acid and methyliminodiacetic acid powders to the HN<(C)over dot>HCH2(COOH)(2) and H3CN<(C)over dot>HCH2(COOH)(2) radicals respectively. The spectra were computer simulated and the g values of the radicals and the hyperfine structure constants of the unpaired electron with nearby protons and N-14 nucleus were determined. The results were found to be in good agreement with the existing literature data.
  • [ X ]
    Öğe
    Spectral analysis and quantum chemical studies of chair and twist-boat conformers of cycloheximide in gas and solution phases
    (Elsevier, 2018) Tokatli, A.; Ucun, F.; Sutcu, K.; Osmanoglu, Y. E.; Osmanoglu, S.
    In this study the conformational behavior of cycloheximide in the gas and solution (CHCl3) phases has theoretically been investigated by spectroscopic and quantum chemical properties using density functional theory (wB97X-D) method with 6-31++G(d,p) basis set, for the first time. The calculated IR results reveal that in the ground state the molecule exits as a mixture of the chair and twist-boat conformers in the gas phase, while the calculated NMR results reveal that it only exits as the chair conformer in the solution phase. In order to obtain the contributions coming from intramolecular interactions to the stability of the conformers in the gas and solution phases, the quantum theory of atoms in molecules (QTAIM), noncovalent interactions (NCI) method, and natural bond orbital analysis (NBO) have been employed. The QTAIM and NCI methods indicated that by intramolecular interactions with bond critical point (BCP) the twist-boat conformer is more stabilized than the chair conformer, while by steric interactions it is more destabilized. Considering that these interactions balance each other, the stabilities of the conformers are understood to be dictated by the van der Waals interactions. The NBO analyses show that the hyperconjugative and steric effects play an important role in the stabilization in the gas and solution phases. Furthermore, to get a better understanding of the chemical behavior of this important antibiotic drug we have evaluated and, commented the global and local reactivity descriptors of the both conformers. Finally, the EPR analysis of gamma-irradiated cycloheximide has been done. The comparison of the experimental and calculated data have showed the inducement of a radical structure of (CH2)(2)CCH2 in the molecule. The experimental EPR spectrum has also confirmed that the molecule simultaneously exists in the chair and twist-boat conformers in the solid phase. (C) 2017 Elsevier B.V. All rights reserved.