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2002

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Metallation Of Mesitylene By Organolithium Compounds In The Presence Of Lithium Polyether Alkoxides, Tuba Kayhan, Ni̇han Nugay, Turgut Nugay Jan 2002

Metallation Of Mesitylene By Organolithium Compounds In The Presence Of Lithium Polyether Alkoxides, Tuba Kayhan, Ni̇han Nugay, Turgut Nugay

Turkish Journal of Chemistry

The catalytic effect of polyether alkoxides (PEAs) on the activity Of organolithium compounds as a metallating agent studied. The sites of metallation as mono, di, tri, and gem metallation at three different benzylic positions were investigated in terms of relative yield by using gas chromatography-mass spectroscopy (GC-MS couple) techniques. The yield of the trimetallated (1,3,5-metallated) mesitylene was optimized by improving the metallation conditions. Special attention was paid to the effect of metal type, alkoxide structure, solvent polarity, temperature and also relative mole ratios of was reactants such as alkoxide to mesitylene and n-butyllithium to mesitylene on metallation reactions. It was …

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A Comparative Study Of Just-In-Time (Jit) And Theory Of Constraints (Toc) Systems With Varying Constraint Locations And Operational Characteristics, Pirun Hemmondharop Jan 2002

A Comparative Study Of Just-In-Time (Jit) And Theory Of Constraints (Toc) Systems With Varying Constraint Locations And Operational Characteristics, Pirun Hemmondharop

Doctoral Dissertations

"Various researchers have extolled the benefits of Theory of Constraints (TOC), Just-in-Time (JIT), and other manufacturing strategies. Some supporters of JIT argue it is the least costly, while others point to the overall benefits of TOC. There are conflicting claims as to the best manufacturing philosophies which is compounded by the fact that no one system is best in every situation. The success of a production system truly depends on the manufacturing environment rather than the philosophy being used. This study uses computer simulations of differing manufacturing environments to compare Just-in-Time (JIT) and Theory of Constraints (TOC) philosophies over two …

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An Investigation Of Some Parameters On Electrorheological Properties Of Polypyrrole Suspensions, Deni̇z Şahi̇n, Beki̇r Sari, Hali̇l İbrahi̇m Ünal Jan 2002

An Investigation Of Some Parameters On Electrorheological Properties Of Polypyrrole Suspensions, Deni̇z Şahi̇n, Beki̇r Sari, Hali̇l İbrahi̇m Ünal

Turkish Journal of Chemistry

In this study, polypyrrole (PPy) was synthesized by cationic addition polymerization. The polymer was characterized by FTIR spectroscopy, scanning electron microscopy (SEM), particle size, magnetic susceptibility, and four-probe conductivity measurements. From the magnetic susceptibility measurements, it was found that the polymer was a bipolaron conducting mechanism. From the particle size measurements, the average particle size of PPy was determined to be 3.2 \mu m. Suspensions of this polymer were prepared in silicone oil, mineral oil, trioctyltrimellitate (TOTM), dioctylphthalate (DOP) and marlotherm-s in different concentrations (5-20%, m/m). The electrorheological (ER) properties of these suspensions were investigated under various d.c. electric field …

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Determination Of Manganese And Iron In Magmatic Rocks After Ultrasonic Leaching By Flame Aas, M. Hi̇kmet Özkan, Mehmet Akçay Jan 2002

Determination Of Manganese And Iron In Magmatic Rocks After Ultrasonic Leaching By Flame Aas, M. Hi̇kmet Özkan, Mehmet Akçay

Turkish Journal of Chemistry

An alternative sample preparation method has been developed for destructive analysis of magmatic rock sample. The method simply included the crushing, HF treatment and 1% HCl leaching steps of the rock samples under ultrasonic effects. There is no need to exhaust all of the sample through the operation. A reproducible and representative, partial recovery of an analyte was expected in a procedural sequences consisting of strictly defined steps. The changes in analyte recoveries were investigated by sample grain size, sample mass, applied ultrasonic power and sonication time. The optimum recovery conditions were examined. In addition, the kinetics of the dissolution …

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Extraction Equilibria Of Nicotinic Acid Using Alamine 300/Diluent And Conventional Solvent Systems, Aynur Şenol Jan 2002

Extraction Equilibria Of Nicotinic Acid Using Alamine 300/Diluent And Conventional Solvent Systems, Aynur Şenol

Turkish Journal of Chemistry

The distribution of nicotinic acid between water and Alamine 300 (tri-n-octylamine) dissolved in various (proton-donating and -accepting, polar and nonpolar) diluents, and a comparison with the extraction equilibria of pure diluent alone were studied at 298 K and a phase ratio of 1:1 (v/v). The cyclic alcohol/amine system yielded the highest synergistic extraction efficiency. The strength of the complex solvation was found to be reasonably high for halogenated aliphatic hydrocarbons and nitrobenzene, activating mainly the formation of the acid_{1}-amine_{1} structure. The influence of the acid structure over distribution was evaluated through comparing the extractabilities of three acids containing different functional …

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Partially Purification And Characterization Of Polyphenol Oxidase Of Quince, Hülya Yağar, Ayten Sağiroğlu Jan 2002

Partially Purification And Characterization Of Polyphenol Oxidase Of Quince, Hülya Yağar, Ayten Sağiroğlu

Turkish Journal of Chemistry

Polyphenol oxidase (PPO, EC 1.14.18.1) was extracted from quince (Cydonia oblonga) by using 0.1 M phosphate buffer, pH 6.8. The polyphenol oxidase of quince was partially purified by (NH_{4})_{2}SO_{4} and dialysis. Substrate specificity experiments were carried out with catechol, pyrogallol, L-DOPA, p-cresole and tyrosine. Catechol was the most suitable substrate compound for quince PPO. The Michaelis constants were 4.54 mM, 7.35mM and 17.8 mM for catechol, pyrogallol and L-DOPA, respectively at 25^oC. The optimum pH and temperature were determined with the specific substrate catechol as 8.0 and 40$^oC, respectively. Of eight inhibitors tested L-cysteine, ascorbic acid and potassium cyanide were …

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Dehydration Behaviour Of Borax Pentahydrate To Anhydrous Borax By Multi-Stage Heating In A Fluidized, Ömer Şahi̇n, A. Nusret Bulutcu Jan 2002

Dehydration Behaviour Of Borax Pentahydrate To Anhydrous Borax By Multi-Stage Heating In A Fluidized, Ömer Şahi̇n, A. Nusret Bulutcu

Turkish Journal of Chemistry

In order to optimize the anhydrous borax process in a fluidized bed calcinator, it is absolutely necessary to study the dehydration behaviour of borax pentahydrate. It was found that the basic feature of the dehydration of borax pentahydrate to anhydrous borax is concerned with the conditions employed. The bulk density and sodium borate content of the end product were determined to be a function of number of stages of temperature of the dehydration period in the fluidized bed. It was observed that bulk density also depends on the number of moles of water remaining in the borax pentahydrate structure. High …

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Phenolic Constituents From Phlomis Lycia, İclal Saracoğlu, Ü. Şebnem Harput, İhsan Çaliş, Yukio Ogihara Jan 2002

Phenolic Constituents From Phlomis Lycia, İclal Saracoğlu, Ü. Şebnem Harput, İhsan Çaliş, Yukio Ogihara

Turkish Journal of Chemistry

From the aerial parts of Phlomis lycia L. (Labiatae) a lignan glucoside, (-)-dihydrodehyrodiconiferyl alcohol-9-O-\beta -D-glucopyranoside (1); a caffeic acid ester, chlorogenic acid (2); three phenylethanoid glycosides, forsythoside B (3), alyssonoside (4) and leucosceptoside B(5); and two iridoid glucosides, lamiide (6) andauroside (7), were isolated. The structure elucidation of the isolated compounds was carried out by spectroscopic (UV, IR, 1D- and 2D-NMR, FAB-MS) methods. (-)-Dihydrodehyrodiconiferyl alcohol-9-O-\beta -D-glucopyranoside (1) and chlorogenic acid (2) were isolated for the first time from Phlomis species in this study.

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Cover And Contents Jan 2002

Cover And Contents

Turkish Journal of Chemistry

No abstract provided.

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Iridoid And Phenylethanoid Glycosides From Euphrasia Pectinata, Tayfun Ersöz, M. Zi̇ver Berkman, Deni̇z Taşdemi̇r, İhsan Çaliş, Chris M. Ireland Jan 2002

Iridoid And Phenylethanoid Glycosides From Euphrasia Pectinata, Tayfun Ersöz, M. Zi̇ver Berkman, Deni̇z Taşdemi̇r, İhsan Çaliş, Chris M. Ireland

Turkish Journal of Chemistry

Two specimens of Euphrasia pectinata collected from different regions of northern Anatolia were studied to determine their iridoid and phenylethanoid glycosides. Four iridoid glucosides, aucubin (1), euphroside (2), ixorodoside (3), and boschnaloside (4), and two phenylethanoid glycosides, acteoside (5) and leucosceptoside A (6), were isolated, and characterized from the aerial parts of E. pectinata} collected from Zigana pass (Trabzon). From the aerial parts of E. pectinata} collected from Kartalkaya (Bolu), a phenethyl alcohol glycoside, decaffeoylacteoside (7), was isolated in addition to previously isolated compounds. The structures of the isolated compounds were established by spectroscopic evidence.

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A New Synthesis Of Bromobenzotropones: Oxidation Of 8-Bromo-5 H -Benzo[A]Cycloheptene, Ari̇f Daştan, Y. Kemal Yildiz, Cavi̇t Kazaz, Meti̇n Balci Jan 2002

A New Synthesis Of Bromobenzotropones: Oxidation Of 8-Bromo-5 H -Benzo[A]Cycloheptene, Ari̇f Daştan, Y. Kemal Yildiz, Cavi̇t Kazaz, Meti̇n Balci

Turkish Journal of Chemistry

The oxidation of 8-bromo-5H-benzo[a]cycloheptene with some oxidation reagents was studied. 2,3- and 4,5-benzotropone derivatives were obtained. The structures of the bromobenzotropones were determined by ^{1}H- and ^{13}C-NMR data.

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Solvent, Temperature And Concentration Effects On The Adsorption Of Poly(N-Butyl Methacrylate) On Alumina From Solutions, Nursel Pekel, Olgun Güven Jan 2002

Solvent, Temperature And Concentration Effects On The Adsorption Of Poly(N-Butyl Methacrylate) On Alumina From Solutions, Nursel Pekel, Olgun Güven

Turkish Journal of Chemistry

Adsorption of poly(n-butyl methacrylate) (PnBMA) on alumina from solution was studied by UV and FT-IR Photoacoustic Spectroscopy techniques. The effects of the solvent, temperature, concentration, and molecular weight of the polymer on adsorption were investigated. Three solvents, cyclohexane, carbon tetrachloride and benzene, were employed. The adsorption was dependent on molecular weight and much more polymer was adsorbed in cyclohexane than in other solvents on the alumina surface. A decrease in adsorption was observed with increasing temperature. The results are in conformity with Langmuir's isotherm. The differences observed in Langmuir parameters were explained by polymer-polymer, polymer-solvent, polymer-adsorbent, and solvent-adsorbent interactions.

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Diterpenes From Sideritis Sipylea And S. Dichotoma, Gülaçti Topçu, Ahmet C. Gören, Turgut Kiliç, Y. Kemal Yildiz, Gülendam Tümen Jan 2002

Diterpenes From Sideritis Sipylea And S. Dichotoma, Gülaçti Topçu, Ahmet C. Gören, Turgut Kiliç, Y. Kemal Yildiz, Gülendam Tümen

Turkish Journal of Chemistry

Two Sideritis species afforded eleven kaurene and one beyerene diterpenes. Structures of the compounds from Sideritis sipylea} were elucidated as linearol (1), 7-epicandicandiol (2), sideridiol (3), siderol (4), isolinearol (5), isosidol (6) and epoxyisolinearol (7). Linearol was treated with m -chloroperbenzoic to afford its analogues ent-3\beta ,7\alpha ,17-trihydroxy-18-acetoxykaur-15-ene (1a) and ent}-7\alpha ,17,18-trihydroxy-3\beta -acetoxykaur-15-ene (1b) as new compounds. From the second species, Sideritis dichotoma, the kaurenes sideridiol (3) siderol (4), ent-7\alpha ,18-dihydroxy-15\beta ,16\beta -epoxykaurane (8)}, ent}-7\alpha -acetoxy,18-hydroxy-15\beta ,16\beta -epoxykaurane (9), ent-7\alpha -acetoxy-15,18-dihydroxy-kaur-16-ene (10), ent-7\alpha ,15,18-trihydroxykaur-16-ene (11) and the beyerene ent-7\alpha ,18-dihydroxybeyer-15-ene (12) were isolated. Structural elucidation is based on NMR techniques …

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Synthesis And Electronic Structure Of New Aryl- And Alkyl-Substituted 1,3,4-Oxadiazole-2-Thione Derivatives, Feray Aydoğan, Zuhal Turgut, Nüket Öcal, Safi̇ye Sağ Erdem Jan 2002

Synthesis And Electronic Structure Of New Aryl- And Alkyl-Substituted 1,3,4-Oxadiazole-2-Thione Derivatives, Feray Aydoğan, Zuhal Turgut, Nüket Öcal, Safi̇ye Sağ Erdem

Turkish Journal of Chemistry

New 5-alkyl and 3-(2,4-dimethylphenyl) substituted 1,3,4-oxadiazole-2-thione derivatives were synthesized by the ring closure reactions of various acylhydrazides with carbon disulphide. Mannich bases for some of these compounds were also synthesized by condensation with benzaldehyde and primary amines. All new compounds were characterized by spectral data. Most of them were tested for their antibacterial and antituberculostatic activity. Molecular orbital calculations at the HF/6-31G** level were also performed to determine the optimized geometrical structures. Results indicated electron delocalization over several atoms of the ring. An additional study on the tautomeric equilibrium between 1,3,4-oxadiazole-2-thione and its thiol form showed that the thione tautomer …

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Thermodynamic And Kinetic Parameters Concerning Complex Formation Between 3-Hydroxy- And 1-Aminopyrene And Pyridine, Nursel Acar, Özgül Koçak Jan 2002

Thermodynamic And Kinetic Parameters Concerning Complex Formation Between 3-Hydroxy- And 1-Aminopyrene And Pyridine, Nursel Acar, Özgül Koçak

Turkish Journal of Chemistry

Systems formed by the pyrene derivatives 3-hydroxypyrene and 1-aminopyrene with pyridine were studied. The thermodynamic and kinetic parameters of the systems were calculated using the changes in the absorption and emission spectra which occur due to hydrogen bond or complex formation. The decrease of the formation rate constant in the series methylcyclohexane, benzene, and o-chlorotoluene may be due to a more difficult formation of the hydrogen bond complex due to the increase of the dielectric constant in the solvent series.

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Glycine Transport Through A Charged Polysulfone Cation Exchange Membrane, Nuri̇ Ünlü, Hüseyi̇n Kara, Mustafa Ersöz Jan 2002

Glycine Transport Through A Charged Polysulfone Cation Exchange Membrane, Nuri̇ Ünlü, Hüseyi̇n Kara, Mustafa Ersöz

Turkish Journal of Chemistry

The transport of glycine through a charged polysulfone cation exchange membrane was studied as a function of pH at different initial conditions of less than pH 5.9 and the glycine permeability was explained under the experimental conditions as pH dependent interfacial transport. The glycine permeability increases with a decreasing pH in the receiver phase. The largest permeability was obtained if the initial pH on the source side was pH 5.9 and that on the opposite side was pH 2.0. The transport phenomena can be explained by the interfacial transport based on the interfacial chemical reaction (protonation, deprotonation or ion-exchange) between …

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A Comparative Study For Basic Characterization Of Three Clinoptilolite Specimens, Eva Chmielewska, Eva Samajova, Jan Kozac Jan 2002

A Comparative Study For Basic Characterization Of Three Clinoptilolite Specimens, Eva Chmielewska, Eva Samajova, Jan Kozac

Turkish Journal of Chemistry

Physicochemical and mineralogical characteristics of the clinoptilolite tuffs of Chinese, Slovakian and American origin were investigated using various techniques, i.e. X - ray powder diffraction, water vapour desorption, ion exchange and chemical analysis.

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The Kinetics And Mechanism Of Oxidation Of Vanillin By Diperiodatonickelate(Iv) In Aqueous Alkaline Medium, Chandrashekhar Kathari, Pandurang Pol, Sharanappa Nandibewoor Jan 2002

The Kinetics And Mechanism Of Oxidation Of Vanillin By Diperiodatonickelate(Iv) In Aqueous Alkaline Medium, Chandrashekhar Kathari, Pandurang Pol, Sharanappa Nandibewoor

Turkish Journal of Chemistry

The title reaction was investigated in aqueous alkaline medium. A first order dependence in diperiodatonickelate (IV) (DPN) and an apparent fractional order in both vanillin and alkali were obtained. Periodate has a retarding effect on the reaction. The effect of added products and the ionic strength of the reaction medium have no significant effect on the reaction rate. A decrease in the dielectric constant of the medium decreases the rate of reaction. Effects of temperature on the rate of reaction were studied. A mechanism based on experimental results was proposed, and constants involved in the mechanism were evaluated. A good …

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Iridoid And Phenylpropanoid Glycosides From Phlomis Grandiflora Var. Fimbrilligera And Phlomis Fruticosa, Tayfun Ersöz, İclal Saracoğlu, Ü. Şebnem Harput, İhsan Çaliş, Ali̇ Arslan Dönmez Jan 2002

Iridoid And Phenylpropanoid Glycosides From Phlomis Grandiflora Var. Fimbrilligera And Phlomis Fruticosa, Tayfun Ersöz, İclal Saracoğlu, Ü. Şebnem Harput, İhsan Çaliş, Ali̇ Arslan Dönmez

Turkish Journal of Chemistry

From the aerial parts of Phlomis grandiflora var. fimbrilligera, two iridoid glucosides, 8-epi-loganin (1) and auroside (2), together with five phenylethanoid glycosides, forsythoside B (3), alyssonoside (4), verbascoside (5), hattushoside (6) and phlomisethanoside (7), were isolated. Iridoid glucosides auroside (2) and lamiide (8) and phenylethanoid glycosides, forsythoside B (3), alyssonoside (4), and verbascoside (5) as well as a lignan glucoside, syringaresinol-4 ' -O-\beta -D-glucoside (9), were characterized from the overground parts of P. fruticosa. The structures of the isolates were elucidated by means of one and two dimensional (COSY, HSQC and HMBC) NMR techniques and ESI MS.

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Aspertins A-D: Further Piperidine Alkaloids From Andrachne Aspera} (Euphorbiaceae), Viqar Uddin Ahmad, Arshad Kamal, Muhammad Shaiq Ali Jan 2002

Aspertins A-D: Further Piperidine Alkaloids From Andrachne Aspera} (Euphorbiaceae), Viqar Uddin Ahmad, Arshad Kamal, Muhammad Shaiq Ali

Turkish Journal of Chemistry

The aerial parts of Andrachne aspera belonging to the family Euphorbiaceae yielded four new piperidine alkaloids: aspertin-A (1), aspertin-B (2), aspertin-C (3) and aspertin-D (4). The structures of isolated alkaloids were elucidated by NMR, mass spectrometery and chemical means.

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Diels-Alder Reactions Using 5 M Liclo_{4} -Diethyl Ether Catalyst, Mesut Kacan, H. R. Ferhat Karabulut Jan 2002

Diels-Alder Reactions Using 5 M Liclo_{4} -Diethyl Ether Catalyst, Mesut Kacan, H. R. Ferhat Karabulut

Turkish Journal of Chemistry

The rate acceleration of Diels-Alder reactions in 5.0 M lithium perchlorate-diethyl ether was re-examined using itaconic anhydride and itaconic acid. Rate acceleration was observed for non-functionalised dienes, but functionalised dienes gave the starting or polymeric materials.

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Pyrrolizidine Alkaloids From Symphytum Sylvaticum Boiss. Subsp. Sepulcrale. (Boiss.& Bal.) Greuter & Burdetvar. Sepulcrale And Symphytum Aintabicum Hub.- Mor. & Wickens, Semra Kurucu, Murat Kartal, Muhammad Iqbal Choudhary, Gülaçti Topçu Jan 2002

Pyrrolizidine Alkaloids From Symphytum Sylvaticum Boiss. Subsp. Sepulcrale. (Boiss.& Bal.) Greuter & Burdetvar. Sepulcrale And Symphytum Aintabicum Hub.- Mor. & Wickens, Semra Kurucu, Murat Kartal, Muhammad Iqbal Choudhary, Gülaçti Topçu

Turkish Journal of Chemistry

Pyrrolizidine alkaloid (Echimidine-N-oxide) was isolated from Symphytum sylvaticum Boiss. subsp. sepulcrale (Boiss. & Bal.) Greuter & Burdet var. sepulcrale and pyrrolizidine alkaloid (Echimidine) was isolated from Symphytum aintabicum Hub. - Mor. & Wickens. The structures of the isolated compounds were elucidated based on IR, EIMS, ^{1}H, and ^{13}C NMR analysis and also on 2D NMR (COSY, HMBC, HMQC) experiments.

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Determination Of Zinc In Aerosol Samples By Discrete Nebulization Flame Atomic Absorption Spectrometry, Deni̇z Yurtsever Sarica, Di̇lek Akim, Tuncel Özden Jan 2002

Determination Of Zinc In Aerosol Samples By Discrete Nebulization Flame Atomic Absorption Spectrometry, Deni̇z Yurtsever Sarica, Di̇lek Akim, Tuncel Özden

Turkish Journal of Chemistry

A well-known analytical method, ``discrete nebulization'', which is suitable for samples having a limited amount like body fluids, high solid content or salt solutions, and less volatile metals, has been further developed for zinc determination in aerosol samples. The effects of injection volume and nebulizer aspiration rate on absorbance and precision were studied. A calibration graph was obtained linearly up to 1.75 mg/L Zn with a 0.9988 correlation coefficient and 3.09\% RSD using 50 \mu L injection volume, values comparable to conventional continuous nebulization. The detection limit (3S) achieved by the method was calculated to be 1.09 ng or 0.020 …

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Determination Of Trace Elements In Iron Minerals By Atomic Absorption Spectrometry, Trajce Stafilov, Dragica Zendelovska Jan 2002

Determination Of Trace Elements In Iron Minerals By Atomic Absorption Spectrometry, Trajce Stafilov, Dragica Zendelovska

Turkish Journal of Chemistry

A method for the determination of lead, cobalt, nickel, chromium, zinc and manganese in iron minerals siderite (FeCO_3), hematite (Fe_{2}O_{3), pyrite and marcasite (FeS_{2) by flame and Zeeman electrothermal atomic absorption spectrometry (ETAAS) was developed. Interferences were investigated by measuring the absorbance of the elements investigated in series of samples with varying mass ratios of the elements investigated and iron as the potential interfering element. It was found that there was no interference in the determined mass ratios of iron on the absorbance of Mn and Zn and that they could be directly analyzed by flame and electrothermal atomic absorption …

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Effects Of Ozonation On Characteristics Of Aquatic Fulvic Acid, Şermi̇n Gül Jan 2002

Effects Of Ozonation On Characteristics Of Aquatic Fulvic Acid, Şermi̇n Gül

Turkish Journal of Chemistry

Aquatic fulvic acid (FA) treated with ozone was characterized by physical/chemical (dissolved organic carbon-DOC), spectroscopic (UV/VIS, IR, fluorescence), chromatographic (gel permeation chromatography-GPC) methods. The influence of ozonation on the subsequent water treatment process such as flocculation and chlorination was also examined. The DOC concentration of the 20 min ozonated FA samples was reduced only a small amount (5%) whereas the UV absorption reduced to a higher percent (40%). The IR spectra of ozonated samples showed a moderate attenuation of the double band and aromatic character of FA. Ozonation of the FA caused the fluorescence intensities to increase steadily with ozonation …

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A Study Of The Adsorption Of Phenol By Activated Carbon From Aqueous Solutions, Riaz Qadeer, Abdul Hameed Rehan Jan 2002

A Study Of The Adsorption Of Phenol By Activated Carbon From Aqueous Solutions, Riaz Qadeer, Abdul Hameed Rehan

Turkish Journal of Chemistry

A commercial active carbon was tested as an adsorbent for the removal of phenol from aqueous solutions. The optimum conditions for maximum adsorption in terms of shaking time, amount of the adsorbent, and concentration of the adsorbate were identified. The adsorption data fitted the Langmuir isotherm equation in the whole range of concentrations studied. The adsorption of picric acid, pyrogallol and salicylic acid at selected conditions for phenol was also studied. Elution studies to recover the adsorbed phenol from active carbon were performed with distilled water, NaOH and HCl solutions.

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Stabilization Of Papain By Modification With Chitosan, Ali̇ Kilinç, Seçi̇l Önal, Azmi̇ Telefoncu Jan 2002

Stabilization Of Papain By Modification With Chitosan, Ali̇ Kilinç, Seçi̇l Önal, Azmi̇ Telefoncu

Turkish Journal of Chemistry

Papain (EC 3.4.22.2) was immobilized on chitosan by adsorption and subsequent cross-linking with glutaraldehyde. The immobilized papain displayed a lower specific activity than did the native enzyme. The thermal stability of the immobilized papain, relative to that of the free enzyme, was markedly increased. The storage stability of the conjugated enzyme was enhanced such that more than 85% of the initial activity remained after a month storage at 45°C. The optimum pH of immobilized papain was shifted to the acidic region and enzyme stability was increased at pH levels below 3.5.

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Flow Injection Extraction - Spectrophotometric Determination Of Bismuth With Di-(Hydrogenated Tallow Alkyl) Dimethylammonium Chloride, S. A. Barakat Jan 2002

Flow Injection Extraction - Spectrophotometric Determination Of Bismuth With Di-(Hydrogenated Tallow Alkyl) Dimethylammonium Chloride, S. A. Barakat

Turkish Journal of Chemistry

Bismuth(III) (0-25 \mu g/ml) is determined spectrophotometricaly at 513 nm after extraction into dichloromethane of the ion associate di-(hydrogenatedtallowalkyl)dimethylammonium tetraiodobismuthate. The reagent stream is distilled water, merged with 1.0 M sulfuric acid, 5% potassium iodide and 5% (w/v) ascorbic acid solution. The reagent stream is 0.2% (w/v) di-(hydrogenatedtallowalkyl)dimethylammonium chloride solution. The injection rate is 15 h^{-1}. The calibration graph is linear up to 25 \mu g/ml. The detection limit is 0.35 \mu g/ml Bi. The system is applied on water samples and copper-based alloys.

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A Semi-Empirical Study On Metal Ion/Murexide Complexation, N. Zeynep Atay, Tereza Varnali Jan 2002

A Semi-Empirical Study On Metal Ion/Murexide Complexation, N. Zeynep Atay, Tereza Varnali

Turkish Journal of Chemistry

Modeling of the metal ion/ligand complexation reactions between divalent metal cations (M^{2 +} ) and hydrophilic tridentate ligand murexide (Mu^{-} ) in water, water+glycerol, and in glycerol was carried out. Kinetic studies showed that the rate of the reaction is very dependent on the metal ion, with Zn^{2 +} > Ni^{2 +} , but, reactions are slower in dispersed glycerol than in dispersed water. Theoretical calculations, which have shown a metal ion dependence, were consistent with the experimental observations. The entropy values calculated in all solvents were negative and were similar in value, indicating that these spontaneous reactions are enthalpy driven.

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Spectrophotometric Studies Of The Behavior Of P-Amino-N, N-Dimethyl Aniline With Ferric Nitrate In Methanol, Ali Hassoon Al-Taiar, Suhad K. Shubber, A. Megherbi Jan 2002

Spectrophotometric Studies Of The Behavior Of P-Amino-N, N-Dimethyl Aniline With Ferric Nitrate In Methanol, Ali Hassoon Al-Taiar, Suhad K. Shubber, A. Megherbi

Turkish Journal of Chemistry

The UV-visible absorption bands of the new complex were obtained using p-amino-N, N-dimethyl aniline as an electron donor with ferric nitrate as an electron acceptor in methanol at 25°C. The values of association constant K^{AD}, molar extinction coefficient \varepsilon^{AD}, and absorption band energy of charge transfer complex h \varepsilon_{CT} were calculated. The ionization potential of the donor I^{D}, was calculated from the complex band energy. The kinetics of the above association reaction were studied. This reaction was found to be a first order. The values of the rate constant of the forward reaction k_{1}, the rate constant of the reverse …

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