Yazar "Sirit, Abdulkadir" seçeneğine göre listele

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    Application of L-Proline Derivatives as Chiral Shift Reagents for Enantiomeric Recognition of Carboxylic Acids
    (WILEY, 2011) Naziroglu, Hayriye Nevin; Durmaz, Mustafa; Bozkurt, Selahattin; Sirit, Abdulkadir
    Four proline-derived chiral receptors 5-8 were readily synthesized starting from L-proline. The enantiomeric recognition ability of chiral receptors was examined with a series of carboxylic acids by H-1 NMR spectroscopy. The molar ratio and the association constants of the chiral compounds with each of the enantiomers of guest molecules were determined by using Job plots and a nonlinear least-squares fitting method, respectively. The Job plots indicate that the hosts form 1:1 instantaneous complexes with all guests. The receptors exhibited different chiral recognition abilities toward the enantiomers of racemic guests. Among the chiral receptors used in this study, prolinamide 6 was found to be the best chiral shift reagent and is effective for the determination of the enantiomeric excess of chiral carboxylic acids. Chirality 23:463-471, 2011. (C) 2011 Wiley-Liss, Inc.
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    Chiral mono and diamide derivatives of calix[4]arene for enantiomeric recognition of chiral amines
    (WILEY-BLACKWELL, 2008) Kocabaş, Erdal; Durmaz, Mustafa; Alpaydın, Sabri; Sirit, Abdulkadir; Yılmaz, Mustafa
    Novel chiral mono and diamide derivatives of calix[4]arene have been prepared from the aminolysis reaction of 5,11,17,23-tetra-tert-butyl-25,27-dietboxycarbonyl-methoxy-26,28-dihydroxycalix[4]arene 1 and 25,27-diethoxycarbonyl-methoxy-26,28-dihydroxycalix[4]arene 2 with chiral (S)-(-)-1-phenylethylamine (PEA) and (1S,2S)-(+)-2-amino-1-(4-nitrophenyl)-1,3-propanediol, respectively. Spectrophotometric titrations have been performed in CHCl3 at 20-30 degrees C in order to obtain the binding constants (K) and the thermodynamic quantities (Delta H and Delta S) for the stoichiometric 1:1 inclusion complexation of various chiral amines with these new host compounds. Preliminary experiments were undertaken to confirm the complexation properties of receptors 9 and 13 with PEA by H-1 NMR in CDCl3 at room temperature. The molecular recognition abilities and enantioselectivities for guests (R and S)-(x-PEA and (R and S)-cyclohexylethylamine (CHEA) are discussed from a thermodynamic point of view.
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    Enantiomeric recognition of amino acid derivatives by chiral Schiff bases of calix[4]arene
    (PERGAMON-ELSEVIER SCIENCE LTD, 2007) Durmaz, Mustafa; Alpaydın, Sabri; Sirit, Abdulkadir; Yılmaz, Mustafa
    Novel calix[4]arene Schiff bases bearing chiral substituents both on the upper and the lower rims have been developed. These chiral receptors exhibit good chiral recognition ability towards alpha-amino acid ester hydrochlorides (up to K-D/K-L = 4.36, Delta Delta G(O) = - 3.65 kJ mol(-1)) in CHCl3. The molecular recognition abilities and enantioselectivities for guests are also discussed from a thermodynamic point of view. (c) 2007 Elsevier Ltd. All rights reserved.
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    Kinetic study on removal of toxic metal Cr(VI) through a bulk liquid membrane containing p-tert-butylcalix[4]arene derivative
    (ELSEVIER, 2011) Alpaydın, Sabri; Saf, Ahmet O.; Bozkurt, Selahattin; Sirit, Abdulkadir
    The transport of Cr(VI) from aqueous solutions through bulk liquid membrane was studied using p-tert-butylcalixpliarene 3-diethylaminopropyl diamide derivative as a carrier. The aqueous solution of potassium dichromate was used as the model contaminant. The kinetic parameters (k(1), k(2), t(max), R-m(max), J(d)(max) and J(a)(max)) for the forward and the back extraction were calculated by means of Cr(VI) concentrations of the donor and the acceptor phase. The results showed that it was possible to transport 96.65% of Cr(VI) from the acidic donor solutions to the acceptor solutions at the optimum operating conditions after 10 h contact time. The highest transport efficiency was observed at pH 2 in the donor phase and at pH 5 in the acceptor phase. It was shown that the transport of Cr(VI) stem from pH difference between the donor and the acceptor phases. The activation energy values were calculated as 5.77 and 7.99 kJmol(-1) for the forward and the back extraction, respectively. It was indicated that the process was diffusionally controlled by dichromate anions. The experimental results demonstrated that p-tert-butylcalix[4]arene derivative was an effective carrier for the transport of Cr(VI). (C) 2011 Elsevier B.V. All rights reserved.
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    Transport kinetics of chromium(VI) ions through a bulk liquid membrane containing p-tert-butyl calix[4]arene 3-morpholino propyl diamide derivative
    (ELSEVIER SCIENCE BV, 2006) Saf, Ahmet O.; Alpaydın, Sabri; Sirit, Abdulkadir
    The transport of chromate ions (Cr2O72-) from an aqueous solution into an aqueous receiving solution through a bulk liquid membrane containing p-tert-butyl calix[4]arene 3-morpholino propyl diamide as a carrier was examined. The influence of pH on donor and acceptor phase, effect of chromate and carrier concentration, type of solvent, stirring speed and temperature were investigated. The kinetic parameters (k(1), k(2), t(max) R-m(max), J(d)(max), J(a)(max)) were calculated for the interface reactions assuming two consecutive, irreversible first order reactions. The activation energy values are 24.83 kJ mol(-1) for extraction and 5.14kJ mol(-1) for reextraction. These values indicate that the process is diffusionally controlled by chromate ions. The experiments demonstrated that calix[4]arene diamide derivative is a good carrier for Cr(VI) transport through liquid membranes in this study. (c) 2006 Elsevier B.V. All rights reserved.