Chemistry / Kimya

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  • Article
    Citation - WoS: 18
    Citation - Scopus: 22
    Prediction of Lignin and Extractive Content of Pinus Nigra Arnold. Var. Pallasiana Tree Using Near Infrared Spectroscopy and Multivariate Calibration
    (Taylor and Francis Ltd., 2009) Üner, Birol; Karaman, İbrahim; Tanrıverdi, H.; Özdemir, Durmuş
    Determination of quality parameters such as lignin and extractive content of wood samples by wet chemistry analyses takes a long time. Near infrared (NIR) spectroscopy coupled with multivariate calibration offers a fast and nondestructive alternative to obtain reliable results. However, due to the complexity of the spectra obtained from NIR, some wavelength selection is generally required to improve the predictive ability of multivariate calibration methods. Pinus nigra Arnold. Var. pallasiana is the second most growing pine species in Turkey. Even though its rotation period is very high, around 120 years, the forest products industry has widely accepted the use of Pinus nigra because of its ability to grow on a wide range of sites and its suitability to produce desirable products. In this study, 51 samples of Pinus nigra trees were collected and their lignin and extractive content were determined with standard reference (TAPPI) methods. Then, the same samples were scanned with near infrared spectrometer between 1000 and 2500 nm in diffuse reflectance mode. Multivariate calibration models were built with genetic inverse least squares method for both lignin and extractive content using the concentration information obtained from wet standard reference method. Overall, standard error of calibration (SEC) and standard error of prediction (SEP) were ranged between 0.35% (w/w) and 2.4% (w/w).
  • Article
    Reactions of the Solvent-Stabilized Compound [moocl2(thf)2] With Aromatic Nitrogen Donor Ligands: Spectroscopic Characterization and Semiempirical Am1* Calculations
    (TUBITAK, 2009) Kılıçkaya, Gülşah; Doğan, Başak; Acar, Nursel; Sözüer, Hikmet Işıl
    Reaction of the solvent-stabilized dioxo-molybdenum(VI) compound [MoO2 Cl2 (THF)2]withP Ph3 yielded the oxomolybdenum(IV) species [MoOCl2 (THF)2](1) by the removal of one oxygen atom as PPh3 O. The complexes [MoOCl2 (=NC6 H4 CN)] 2,[MoOCl2 (CNC6 H4 OH)] 3,[MoOCl2 (=NC6 H4 NH2)] 4,and [MoOCl2 (=NC6 H4 OCH3)] 5, were synthesized by the reactions of [MoOCl2 (THF)2]with XC6 H4 Y(X =NH2, Y = CN; X= CN, Y = OH; X = Y = NH2;X=NH2,Y=OCH3). All the new compounds were characterized by elemental analyses, and FTIR, UV-Vis, and 1 H and 13 C-NMR spectra. Geometrical parameters and molecular orbital calculations showed that compounds 2-5 are stabilized by a charge transfer between the Mo center and the phenyl ring.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 13
    Near Infrared Spectroscopic Determination of Diesel Fuel Parameters Using Genetic Multivariate Calibration
    (Taylor and Francis Ltd., 2008) Özdemir, Durmuş
    The use of full spectral region from near infrared spectroscopic analysis does not always end up with a good multivariate calibration model as many of the wavelengths do not contain necessary information. Due to the complexity of the spectra, some of the wavelengths or regions may, in fact, disturb the model-building step. Genetic algorithms are one of the useful tools for solving wavelength selection problems and may improve the predictive ability of conventional multivariate calibration methods. This study demonstrates application of genetic algorithm-based multivariate calibration to near infrared spectroscopic determination of several diesel fuel parameters. The parameters studied are cetane number, boiling and freezing point, total aromatic content, viscosity, and density. Multivariate calibration models were generated using genetic inverse least squares (GILS) method and used to predict the diesel fuel parameters based on their near infrared spectra. For each property, a different data set was used and in all cases the number of samples was around 250. Overall, percent standard error of prediction (%SEP) values ranged between 2.48 and 4.84% for boiling point, total aromatics, viscosity, and density. However, %SEP results for cetane number and freezing point were 11.00% and 14.86%, respectively.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 8
    Evaluation of Dissolution Methods in the Presence of High Chloride Content for the Determination of Germanium in Geological Matrices by Hydride Generation Atomic Absorption Spectrometry
    (Japan Society for Analytical Chemistry, 2001) Abbasi, Husam U.; Eroğlu, Ahmet Emin; Anwari, Mohammad A.; Volkan, Mürvet
    The sample dissolution is probably the most crucial step in the determination of germanium in geological and metallurgical samples due to formation of volatile germanium compounds during the course of dissolution. It has been stated that this is especially true for the samples having high sulfide and/or chloride content.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 2
    Synthesis of Α,β-Unsaturated Ketones by Rhodium-Catalyzed Carbonylative Arylation of Internal Alkynes With Arylboronic Acids
    (Georg Thieme Verlag, 2008) Kuş, Melih; Aksın Artok, Özge; Ziyanak, Fırat; Artok, Levent
    The Rh-catalyzed reaction of arylboronic acids with internal alkynes under a CO atmosphere in the presence of an acid additive afforded α,β-unsaturated ketones as the major products. Hydroacylation of internal alkynes, except in the case of diaryl acetylenes, proceeded in syn fashion, yielding the E-configured isomer. A mixture of E- and Z-isomers was obtained with diphenyl acetylene. Reactions were also highly regioselective for various nonsymmetric alkynes.
  • Article
    Citation - WoS: 27
    Citation - Scopus: 30
    Rhodium Catalyzed Reaction of Internal Alkynes With Organoborons Under Co Atmosphere: a Product Tunable Reaction
    (Elsevier Ltd., 2009) Artok, Levent; Kuş, Melih; Aksın, Özge; Dege, Fatma Nurcan; Özkılınç, Fatma Yelda
    Alkynes react with organoborons under a CO atmosphere in the presence of a rhodium(I) catalyst to afford mainly 5-aryl-2(5H)-furanones, α,β-unsaturated ketones, and indanones. The product selectivity can be tuned by modifying the reaction conditions.
  • Article
    Citation - WoS: 85
    Citation - Scopus: 88
    Effect of Immobilization on Catalytic Characteristics of Saturated Pd-N Carbenes in Mizoroki-Heck Reactions
    (Elsevier Ltd., 2006) Aksın, Özge; Türkmen, Hayati; Artok, Levent; Çetinkaya, Bekir; Ni, Chaoying; Büyükgüngör, Orhan; Özkal, Erhan
    A saturated Pd-N-heterocyclic complex was immobilized on an amorphous silica. The complex itself is of very high thermal stability. However, TEM observations, hot filtration, reusability, and poisoning tests all revealed that the complex acted only as a precatalyst to highly active Pd species in Mizoroki-Heck reactions when immobilized. The complex appears more stable when used under homogeneous reaction conditions. The immobilized complex afforded high turnover numbers, 104-105. The higher turnover frequencies were realized at the lower Pd concentrations, which is a characteristic property of ligand-free Pd catalyzed reactions.
  • Article
    Citation - WoS: 21
    Citation - Scopus: 21
    Retention of Aqueous Ba2+ Ions by Calcite and Aragonite Over a Wide Range of Concentrations: Characterization of the Uptake Capacity, and Kinetics of Sorption and Precipitate Formation
    (The Geochemical Society of Japan, 2007) Tunusoğlu, Özge; Shahwan, Talal; Eroğlu, Ahmet Emin
    The uptake of aqueous Ba2+, ions by abiogenic calcite and aragonite was studied over a wide range of concentration; 1.0 × 101, 5.0 × 101, 1.0 × 102 5.0 × 102, 1.0 × 103, 5.0 × 104, and 1.0 × 104 mg/L. The uptake process was characterized using ICP-AES, XRPD, SEM/EDS, and FTIR techniques. Up to the initial concentration of 5.0 × 102 mg/L, the uptake of Ba2+ ions was fast and obeyed Lagergren's kinetic model. The equilibrium data were adequately described using Freundlich isotherm model. The overgrowth of BaCO3 (witherite) took place at higher concentrations, in a kinetically slow process and enhanced the uptake of Ba2+ ions. Quantitative XRPD was used to evaluate the fractions of precipitated BaCO3 on calcite and aragonite minerals and monitor their variation with time. At all the studied concentrations, aragonite showed higher removal capacity of Ba2+ and faster uptake kinetics than did calcite. The precipitated crystals appeared to predominantly possess olivary-like morphology with an average particle size of 1-2 μm. EDS was used to reveal the elemental quantities of Ba and Ca after BaCO3 formation on calcite and aragonite surfaces. FTIR spectroscopy was employed to analyze the vibrational modes in carbonate mixtures upon incorporation of Ba2+ by sorption and precipitation mechanisms.
  • Article
    Citation - WoS: 19
    Citation - Scopus: 21
    Kinetic and Thermodynamic Investigations of Strontium Ions Retention by Natural Kaolinite and Clinoptilolite Minerals
    (Walter De Gruyter Gmbh, 2005) Akar, Dilek; Shahwan, Talal; Eroğlu, Ahmet Emin
    The current study was devoted to the determination of various thermodynamic and kinetic parameters resulting from the fixation of Sr2+ by natural samples of kaolinite and clinoptilolite minerals. The sorption process followed pseudo second order kinetics, with faster sorption on kaolinite compared to clinoptilolite, where the uptake is affected by intraparticle diffusion. Freundlich and Dubinin-Radushkevich isotherm models described the data more adequately than Langmuir model, and clinoptilolite showed a higher strontium sorption capacity than kaolinite. Thermodynamically, the activation energy of Sr2+ sorption by kaolinite and clinoptilolite were respectively, -8.5 and -18.4 kJ/mol. The sorption process on both minerals was spontaneous and endothermic at all the studied concentrations, with ΔH° being 11.3 and 9.8 kJ/mol, for sorption on kaolinite and clinoptilolite, respectively. The findings of this study were compared with those of an earlier study on the uptake of Cs+ by the same minerals.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 3
    Synthesis and Characterization of Nitrosyl[tris(3,5dimethylpyrazolyl) Borato]molybdenum Complexes Containing Aryloxo, Arylamido and Arylcyano Ligands
    (TUBITAK, 2005) Sözüer, Hikmet Işıl; Dülger İrdem, Seçkiner
    The complexes [MoTp*(NO)X(ZC6H4CN-p)] [Tp* = 3,5-dimethylpyrazolyl; X = Cl, Z = O and NH; X = I, Z = CN) were prepared and characterized using 1H-NMR, IR, FAB mass spectroscopy and micro analysis.