Yazar "Yildirim, Ayhan" seçeneğine göre listele

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    Evaluation of the corrosion inhibiting efficacy of a newly synthesized nitrone against St37 steel corrosion in acidic medium: Experimental and theoretical approaches
    (Elsevier Science Bv, 2018) Gerengi, Husnu; Solomon, Moses M.; Ozturk, Serkan; Yildirim, Ayhan; Gece, Ender Gökhan; Kaya, Ertugrul
    A novel amphiphilic nitrone, N-phenyl-1-(4-((11-(pyridin-1-ium-1yl) undecanoyl) oxy)phenyl)methanimine oxide bromide (NP-1-4-11-PUOPMOB) has been synthesized from a fatty acid derivative as a starting material. Structural characterization of the new compound has been realized by spectroscopic techniques (FTIR, H-1 NMR, and C-13 NMR). The corrosion inhibition effect of the compound for St37 steel corrosion in 1 M HCl medium has been investigated using experimental (weight loss, electrochemical impedance spectroscopy, potentiodynamic polarization, dynamic electrochemical impedance spectroscopy) and theoretical approaches complemented by surface morphological examination using energy dispersive X-ray spectroscopy, scanning electron microscope, and atomic force spectroscopy. Results from both chemical and electrochemical techniques reveal that the presence of the nitrone in the acid solution impedes St37 steel corrosion. The inhibition efficiency obtained at 125 ppm and 150 ppm concentrations for all methods is found to be over 90%. NP-1-4-11-PUOPMOB behaves as a mixed type corrosion inhibitor according to the potentiodynamic polarization studies. The adsorption of NP-1-4-11-PUOPMOB molecules onto the metal surface follows Langmuir adsorption isotherm and the calculated K-ads (equilibrium constant of the adsorption process) value reflects strong interaction. There is evidence of NP-1-4-11-PUOPMOB adsorption on the metal surface from SEM, EDAX, and AFM studies. Experimental and theoretical results are in good agreement.
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    Flexible Semicrown Ether-Linked Symmetric Cationic Gemini Surfactants: Synthesis and Evaluation as Catalysts for Acceleration of Diastereoselective [3+2] Cycloaddition Reaction in Reversed Phase Micellar Media
    (Wiley, 2019) Ozturk, Serkan; Yildirim, Ayhan; Gece, Ender Gökhan; Turkdemir, Haluk
    Novel cationic gemini surfactants with a hydrophilic oligo-oxyethylene spacer group were synthesized and their physicochemical properties were identified. Computational studies for these compounds were also performed; molecular geometry, frontier molecular orbitals, and quantum chemical parameters were calculated using density functional theory (DFT). After exploration for catalytic activity, it was found that these surfactants can efficaciously accelerate the [3 + 2] cycloaddition reactions in reversed phase micellar media.
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    High diastereoselectivity induced by intermolecular hydrogen bonding in [3+2] cycloaddition reaction: experimental and computational mechanistic approaches
    (Wiley, 2017) Yildirim, Ayhan; Kaya, Yunus
    A diastereoselective [3 + 2] cycloaddition of N-aryl substituted maleimides with N, a-diphenyl nitrone possessing 11-hydroxyundecyloxy as a flexible substituent was performed. Experimental and comprehensive mechanistic density functional theory studies reveals that intermolecular H-bonding and steric repulsive interaction predominate exo-Z and exo-E cycloaddition transition states, respectively. The reaction proceeded smoothly depending on the reactants and gave a good yield of (syn) cis-isoxazolidine or (anti) trans-isoxazolidine as a single diastereomer.
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    Sustainable synthetic approaches using [C(16)Im][Oxa] as a flexible organocatalyst and DFT studies toward 3,4-dihydropyrimidinones and benzoxazines
    (Springer Wien, 2017) Yildirim, Ayhan; Kaya, Yunus
    Easily accessible 1-hexadecyl-1H-imidazol-3-ium oxalate is highly efficient Bronsted type acidic catalyst for the selected multicomponent one-pot reactions. The short reaction times, easy workup procedures, and green metal-free conditions for the reactions make the protocols more advantageous. Further reactions proceeded smoothly in good to excellent yields with high purity. To investigate mechanism of the multicomponent reactions, DFT calculations were performed.