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Articles 27811 - 27840 of 34720

Full-Text Articles in Physical Sciences and Mathematics

Thermal Decomposition Kinetics Of Anilino-P-Chlorophenylglyoxime Complexes Of Cobalt (Ii), Nickel (Ii) And Copper (Ii), Hakan Arslan, Nevzat Külcü, Ali̇ İhsan Pekacar Jan 2003

Thermal Decomposition Kinetics Of Anilino-P-Chlorophenylglyoxime Complexes Of Cobalt (Ii), Nickel (Ii) And Copper (Ii), Hakan Arslan, Nevzat Külcü, Ali̇ İhsan Pekacar

Turkish Journal of Chemistry

The Co(II), Ni(II) and Cu(II) complexes of anilino-p-chlorophenylglyoxime were synthesised. The thermal behaviour of all complexes was studied by DTA and TG. It was found that pyrolytic decomposition occurs with melting in metal complexes and that metal oxides remain as final products of the metal complexes. A GC-MS combined system was used to identify the products during pyrolytic decomposition. The pyrolytic end products were identified by x-ray powder diffraction. The orders, n, the activation energies, E^*, the pre-exponential factors, A, and the entropies, \Delta S^*, of thermal decomposition reactions were derived from thermogravimetric and differential thermogravimetric curves. The kinetic analysis …

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Differential Pulse Polarographic Determination Of Enalapril Maleate, Fi̇kri̇ye Elmali, Güzi̇n Alpdoğan, Şule Aycan, Sidika Sungur Jan 2003

Differential Pulse Polarographic Determination Of Enalapril Maleate, Fi̇kri̇ye Elmali, Güzi̇n Alpdoğan, Şule Aycan, Sidika Sungur

Turkish Journal of Chemistry

A differential pulse polarographic (DPP) method has been developed for the quantitative analysis of enalapril maleate. Enalapril maleate gives a peak at -1.4 V in methanol. A calibration curve was constructed for the 20 -100 \mu g ml^{-1} concentration range. As a reference method, a reversed phase high performance liquid chromatographic procedure has been developed. Commercially available tablets were analysed by the two methods. Statistical evaluations indicated that there was no significant difference between the mean values and precisions of the two methods at a 95\% confidence level.

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^1h Nmr Studies Of Some Imidazole Ligands Coordinated To Co(Iii), Kosrow Zamani, Akbar Mobinikhaledi, Naser Foroughifar, Khalil Faghihi, Vahid Mahdavi Jan 2003

^1h Nmr Studies Of Some Imidazole Ligands Coordinated To Co(Iii), Kosrow Zamani, Akbar Mobinikhaledi, Naser Foroughifar, Khalil Faghihi, Vahid Mahdavi

Turkish Journal of Chemistry

Chemical shifts for proton signals of an imidazole ring coordinated to Co(III) move downfield as the total complex charge increases. However, the C_{(2) - H} chemical shift of the imidazole ring in cis-[Co(en)_{2}(N-mIm) OPO_{3}H]°, which has no charge compared to those of cis-[Co(en)_{2}(N-mIm) OPO_{3}H]^{+} and cis}-[Co(en)_{2}(N-mIm) OPO_{3}H_{2}]^{2 +} , moves downfield. These unexpected phenomena could be attributed to an intramolecular interaction between the phosphate anion group and C_{(2) - H} of the imidazole ligand.

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Conductimetric And Potentiometric Investigation Of Effects Of Solvents And Titrant On Formation Of Homoconjugates, Esi̇n Canel, Mustafa Taşteki̇n, Orhan Atakol, Esma Kiliç Jan 2003

Conductimetric And Potentiometric Investigation Of Effects Of Solvents And Titrant On Formation Of Homoconjugates, Esi̇n Canel, Mustafa Taşteki̇n, Orhan Atakol, Esma Kiliç

Turkish Journal of Chemistry

Trichloro-, tribromo- and trifluoro- acetic acids were both conductimetrically and potentiometrically titrated in acetonitrile and 2-propanol media. The titrations were carried out at 25°C under nitrogen atmosphere and titrants used were the solutions of triethyl, di-n-butyl and n-butyl amines prepared in the same solvents. Whether these acids gave a homoconjugation reaction during titration was investigated by the use of conductimetric and potentiometric titration curves. In acetonitrile media trichloro- and tribromo-acetic acids decomposed to give chloroform and carbon dioxide, and bromoform and carbon dioxide respectively. It was observed that the acid concentration and the type of titrant used had no effect …

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Purification And Partial Characterization Of Catalase From Chicken Erythrocytes And The Effect Of Various Inhibitors On Enzyme Activity, Tüli̇n Aydemi̇r, Kevser Kuru Jan 2003

Purification And Partial Characterization Of Catalase From Chicken Erythrocytes And The Effect Of Various Inhibitors On Enzyme Activity, Tüli̇n Aydemi̇r, Kevser Kuru

Turkish Journal of Chemistry

Catalase plays a major role in the protection of tissues from the toxic effects of H_{2}O_{2} and partially reduced oxygen species. A nearly 136-fold enzyme purification was obtained from chicken erythrocyte by acetone precipitation, ethanol-chloroform treatment, CM-cellulose and Sephadex G-200 chromatography. The specific activity of purified enzyme was 42,556 U/mg. The molecular weight of the native chicken erythrocyte catalase was estimated at 240 kDa by gel filtration. SDS-gel electrophoresis results indicated that chicken erythrocyte catalase consists of four apparently identical subunits, with a molecular weight of around 57.5 kDa. The optical spectrum of the purified enzyme shows a Soret band …

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Kinetics Of Polymerization Of 2-Hydroxyethylmethacrylate Initiated By A Titanium(Iii)-Dimethylglyoxime Redox System, Kalappa Prashantha, K. V. Kumar Pai, M. Puttegowda Yashoda, B. Sheena Sherigara Jan 2003

Kinetics Of Polymerization Of 2-Hydroxyethylmethacrylate Initiated By A Titanium(Iii)-Dimethylglyoxime Redox System, Kalappa Prashantha, K. V. Kumar Pai, M. Puttegowda Yashoda, B. Sheena Sherigara

Turkish Journal of Chemistry

The polymerization of 2-hydroxyethylmethacrylate (HEMA) initiated by the redox system titanium(III)-dimethyl glyoxime (DMG) was studied in dimethyl formamide (DMF)-water (80:20 v/v) medium in the temperature range 290-310 K. The rate of polymerization (R_{p}) was investigated at various concentrations of reductant, oxidant, sulfuric acid, and monomer. Cyclic voltametric sensing of dimethylglyoxime under the kinetic conditions demonstrated its reduction behavior. From the obtained results, it was inferred that the polymerization reaction was initiated by an organic free radical arising from the titanium(III)-dimethylglyoxime redox system. Chain termination of the polymer took place predominantly by mutual coupling and small fraction by chain transfer mechanism …

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Kinetics Of Aqueous Pyrite Oxidation By Potassium Dichromate - An Experimental Study, Paul Chirita Jan 2003

Kinetics Of Aqueous Pyrite Oxidation By Potassium Dichromate - An Experimental Study, Paul Chirita

Turkish Journal of Chemistry

The kinetics of pyrite oxidation in perchloric acid solutions were investigated at temperatures ranging from 30°C to 40°C, potassium dichromate concentration from 0.001 to 0.05 mol L^{ - 1}, particle size fractions from 50 to 150 \mu m and pH values down to 2.83. The rate of the oxidation reaction is described by the following expression: r = bkS^{0.51}[K_{2}Cr_{2}O_{7}]^{0.64}[H^{+} ]^{0.22} where S is the surface area of reacting solid, r represents the amount of Fe release in solution per unit surface area per unit time, b is a stoichiometric factor, k is the rate constant, and [K_{2}Cr_{2}O_{7}] and [H^{+} ] …

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Synthesis Of Some New Substituted 1,2,4-Triazole And 1,3,4-Thiadiazole And Their Derivatives, Khosrow Zamani, Khalil Faghihi, M. Reza Sangi, Javad Zolgharnein Jan 2003

Synthesis Of Some New Substituted 1,2,4-Triazole And 1,3,4-Thiadiazole And Their Derivatives, Khosrow Zamani, Khalil Faghihi, M. Reza Sangi, Javad Zolgharnein

Turkish Journal of Chemistry

Several 5-(isomeric pyridyl)-4-aryl-1,2,4-triazole-3-thiol/yl-thiomethyl/yl-thioethyl/yl-thiobenzyl and yl-thioglycolic acids were prepared as possible biologically active agents. The infrared, nuclear magnetic resonance (^{1}H-NMR and ^{13}C-NMR), mass spectra and elemental analysis of these compounds are reported

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A Novel Silver Recovery Method From Waste Photographic Films With Naoh Stripping, Nuri̇ Naki̇boğlu, Duygu Toscali, Gürel Ni̇sli̇ Jan 2003

A Novel Silver Recovery Method From Waste Photographic Films With Naoh Stripping, Nuri̇ Naki̇boğlu, Duygu Toscali, Gürel Ni̇sli̇

Turkish Journal of Chemistry

A novel, simple, fast, cheap and pollution-free method was developed for recovering the silver from waste X-ray photographic films with NaOH stripping. The method has a number of advantages because it obviates the need for burning, oxidizing, electrolysis or purifying steps. Moreover, all experiments were carried out in the same flask, unlike other techniques. Silver recovery conditions were optimized and silver a purity level of 99\% was recovered. The metal impurities (Al, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Sn) in the recovered silver were determined using the ICP-MS method. The results were compared with results in …

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Synthesis, Characterization And Electrical Conductivity Of Poly(P-Phenylene Vinylene), Ali̇ Çirpan, Zuhal Küçükyavuz, Savaş Küçükyavuz Jan 2003

Synthesis, Characterization And Electrical Conductivity Of Poly(P-Phenylene Vinylene), Ali̇ Çirpan, Zuhal Küçükyavuz, Savaş Küçükyavuz

Turkish Journal of Chemistry

Poly(p-phenylene vinylene) (PPV) was prepared electrochemically from p-xylene-bis(diethylsulphonium chloride) in a solvent-electrolyte couple of acetonitrile-tetrabutylammonium tetrafluoroborate (TBAFB). The polymer obtained from the electrode surface was converted to PPV by the thermal elimination of diethyl sulfide, HCl and ethyl sulfide. PPV was also obtained chemically in order to investigate the effect of the synthetic method on the structure and electrical conductivity. The characterization of the polymers was carried out by means of fourier transform infrared spectrometer (FTIR), differential scanning calorimetry (DSC) and thermal gravimetry analysis (TGA) techniques. The doping effect on the conductivity of the PPV was investigated by using different …

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Studies On The Mechanism Of Base-Catalyzed Decomposition Of Bicyclic Endoperoxides, Ebru Mete, Ramazan Altundaş, Hasan Seçen, Meti̇n Balci Jan 2003

Studies On The Mechanism Of Base-Catalyzed Decomposition Of Bicyclic Endoperoxides, Ebru Mete, Ramazan Altundaş, Hasan Seçen, Meti̇n Balci

Turkish Journal of Chemistry

Kinetic studies were performed to clarify the Kornblum-Delamare reaction mechanism of bicyclic endoperoxides. Ascaridol and 1,4-diphenyl-2,3-dioxa-bicyclo[2.2.2]oct-5-ene, not having \alpha -protons, did not provide any reaction with bases. Reaction with different bases has revealed that reaction rates for the base-catalyzed decomposition of 2,3-dioxa-bicyclo[2.2.2]oct-5-ene depend strongly on the base strength. The stronger the base used, the faster the conversion rate. Reaction rate values k of endoperoxides with different skeletons were also studied with NEt_{3}. It has been noted that the strength of the base plays the dominant role in determining the rate of the reactions.

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Electrochemical Behaviour Of Thymolphthalein, Mustafa Uçar, Necati̇ Menek Jan 2003

Electrochemical Behaviour Of Thymolphthalein, Mustafa Uçar, Necati̇ Menek

Turkish Journal of Chemistry

The polarographic and voltammetric behaviour of thymolphthalein in ethanol-water (1/5 v/v) was studied using various electrochemical techniques. The reduction of thymolphthalein on a mercury drop electrode was investigated. The adsorption effect on the electrode surface was observed. The rate constants for the electron transfer steps were determined by and without taking adsorption into occount using the Laviron technique and Nicholson technique respectively. The diffusion coefficients were calculated from the cyclic voltammetric data using the method developed by Garrido. Reversibility for the electrode reaction was investigated and a mechanism for the electrode reaction was proposed.

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Flow Injection Amperometric Determination Of Ascorbic Acid Using A Photoelectrochemical Reaction After Immobilization Of Methylene Blue On Muscovite, Yusuf Di̇lgi̇n, Zekerya Dursun, Gürel Ni̇şli̇ Jan 2003

Flow Injection Amperometric Determination Of Ascorbic Acid Using A Photoelectrochemical Reaction After Immobilization Of Methylene Blue On Muscovite, Yusuf Di̇lgi̇n, Zekerya Dursun, Gürel Ni̇şli̇

Turkish Journal of Chemistry

The photoelectrochemical determination of ascorbic acid (AA) was studied based on the photochemical reduction of methylene blue (MB) in 0.1 M phosphate buffer (pH 7.0). MB was used as a redox mediator for the modification of a carbon paste electrode (CPE) due to its facile reducible-oxidizible behaviour. Muscovite, which has a layered structure, was found to be a good and stable supporting material for the immobilization of MB by an ion exchange reaction. The dye is strongly retained and not easily leached from the matrix. MB was reduced to nearly quasi-reversible at the modified carbon paste electrode (MCPE). The oxidation …

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Bromination Of Tricyclo[7.2.1.0^{2,7}]Dodeca-2,4,6,10-Tetraene Derivatives: Highly Brominated Benzobicyclic Systems, Ari̇f Daştan Jan 2003

Bromination Of Tricyclo[7.2.1.0^{2,7}]Dodeca-2,4,6,10-Tetraene Derivatives: Highly Brominated Benzobicyclic Systems, Ari̇f Daştan

Turkish Journal of Chemistry

The bromination reaction of tricyclo[7.2.1.0^{2,7}]dodeca- 2,4,6,10-tetraene derivatives was studied and the possible role of a substituent in rearrangements is discussed.

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Inhibition Studies Of A Few Organic Compounds And Their Condensation Products On The Corrosion Of Zinc In Hydrochloric Acid Medium, Shanthamma K. Rajappa, Thimmappa V. Venkatesha Jan 2003

Inhibition Studies Of A Few Organic Compounds And Their Condensation Products On The Corrosion Of Zinc In Hydrochloric Acid Medium, Shanthamma K. Rajappa, Thimmappa V. Venkatesha

Turkish Journal of Chemistry

The corrosive behavior of zinc in HCl solution containing various concentrations of glutaraldehyde GTD, glycine GLN, methionine MTN, and their condensation products formed between GTD + GLN (CP1) and GTD + MTN (CP2) was investigated. The corrosion-inhibitive action of these compounds on zinc metal was studied using chemical and electrochemical methods. The results showed that the compound CP2 is the best inhibitor and that its inhibition efficiency reaches 92.56% at 10^{-2} M in 0.05 M acid concentration. As an inhibitor, CP2 was found to have a predominant cathodic effect and its adsorption was confirmed with the Temkin isotherm. The effect …

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Evaluation Of Thermal Decomposition Kinetics Of Borax Pentahydrate Using Genetic Algorithm Method By Isothermal Analysis, Ömer Şahi̇n, A. Nusret Bulutcu Jan 2003

Evaluation Of Thermal Decomposition Kinetics Of Borax Pentahydrate Using Genetic Algorithm Method By Isothermal Analysis, Ömer Şahi̇n, A. Nusret Bulutcu

Turkish Journal of Chemistry

The thermal calcination of borax pentahydrate was investigated for both dehydration and decomposition steps at temperatures between 392 and 573 K in a controlled fluidized bed drier. The best kinetic parameters (reaction rate constants, reaction order and equilibrium values) of both steps were determined by the genetic algorithm (GA) method for each calcination temperature in respect of relative standard deviation. The values of the kinetic parameters showed that the dehydration step of borax pentahydrate was controlled by a homogeneous reaction of the order of about 2/3 whereas the decomposition step was controlled by a reaction order of about 1. These …

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Organotin(Iv) Complexes Of Aniline Derivatives Part-Ii - Synthesis And Spectroscopic Characterization Of Organotin(Iv) Derivatives Of 2-[(4-Bromoanilino)Carboxyl]Benzoic Acid, Khadija Shahid, Saqib Ali, Saira Shahzadi, Zareen Akhtar Jan 2003

Organotin(Iv) Complexes Of Aniline Derivatives Part-Ii - Synthesis And Spectroscopic Characterization Of Organotin(Iv) Derivatives Of 2-[(4-Bromoanilino)Carboxyl]Benzoic Acid, Khadija Shahid, Saqib Ali, Saira Shahzadi, Zareen Akhtar

Turkish Journal of Chemistry

A series of organotin(IV) complexes with the general formula R_{2}SnL_{2} and R_{3}SnL, where R = CH_{3}, C_{2}H_{5}, n-C_{4}H_{9}, C_{6}H_{5}, C_{6}H_{5}CH_{2} and L = 2-[(4-bromoanilino)carboxyl]benzoate, were synthesized and characterized by infrared, mass and multinuclear NMR (^{1}H, ^{13}C, ^{119}Sn) spectroscopies. The coordination around tin in solid as well as in solution has been proposed on the basis of spectroscopic results.

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Characterization Of Polyphenol Oxidase From Jerusalem Artichoke (Helianthus Tuberosus), Emi̇ne Zi̇yan, Şule Pekyardimci Jan 2003

Characterization Of Polyphenol Oxidase From Jerusalem Artichoke (Helianthus Tuberosus), Emi̇ne Zi̇yan, Şule Pekyardimci

Turkish Journal of Chemistry

Polyphenol oxidases (PPO) in Jerusalem arthichoke (Helianthus tuberosus) skin and flesh were extracted and purified through (NH_{4})_{2}SO_{4} precipitation, dialysis and gel filtration chromatography. The samples obtained from ammonium sulfate precipitation and dialysis were used for the characterization of crude skin and flesh PPO. Optimum pH values were 7.5 for skin PPO and 8.0 for flesh PPO with 50 mM catechol. The optimum temperatures for skin and flesh PPO were 25 °C and 30 °C respectively with catechol. Six inhibitors were tested in the study and the most effective inhibitors were found to be sodium azide and thiourea for both flesh …

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Flow Injection Speciation Analysis Of Manganese In Real Samples By Diphenylcarbazide-Spectrophotometric Determination, Kazem Kargosha, Meissam Noroozifar Jan 2003

Flow Injection Speciation Analysis Of Manganese In Real Samples By Diphenylcarbazide-Spectrophotometric Determination, Kazem Kargosha, Meissam Noroozifar

Turkish Journal of Chemistry

The flow injection speciation of manganese in aqueous solution using a spectrophotometry method of detection is presented. Manganese (VII) can be determined spectrophotometrically at 308 nm after the reaction with Sym-diphenycarbazide in buffered at pH = 3.05 with phosphate. Under the optimized conditions, total manganese concentration can also be determined after oxidation of Mn^{2+} to MnO_{4}^{-} and then Mn^{2+} concentration can be calculated from the difference. The linear range of determination is 0.047-4.50 mg/l with a 3\sigma detection limit of 31 \mu g/l. The proposed method is applied to the determination of MnO_{4}^{-} and Mn^{2+} in effluent streams and foods …

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Column Preconcentration/Separation And Atomic Absorption Spectrometric Determinations Of Some Heavy Metals In Table Salt Samples Using Amberlite Xad-1180, Mustafa Soylak, Aslihan Uzun Karatepe, Lati̇f Elçi̇, Mehmet Doğan Jan 2003

Column Preconcentration/Separation And Atomic Absorption Spectrometric Determinations Of Some Heavy Metals In Table Salt Samples Using Amberlite Xad-1180, Mustafa Soylak, Aslihan Uzun Karatepe, Lati̇f Elçi̇, Mehmet Doğan

Turkish Journal of Chemistry

A simple and sensitive solid phase extraction procedure on Amberlite XAD-1180 resin is presented for the determination of chromium, cobalt, manganese and nickel at trace levels by atomic absorption spectrometry. The analyte ions were quantitatively taken at pH 9 by using ammonia/ammonium acetate buffer without any chelating agent. The influences of some analytical parameters such as sample volume, eluent type and flow rates on the retention of Cr, Co, Mn and Ni ions were examined. No influences were observed from the matrix ions of table salt samples. The detection limits for Cr, Co, Mn and Ni were 0.27 \mu g/g, …

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The Kinetic Study Of The Chemical Oscillating System Of 1,3-Propanediol/Acetone As The Organic Substrate, Shi-Gang Shen, Caiqin Yang, Han-Wen Sun, Jin-Huan Shan, Ying Liu Jan 2003

The Kinetic Study Of The Chemical Oscillating System Of 1,3-Propanediol/Acetone As The Organic Substrate, Shi-Gang Shen, Caiqin Yang, Han-Wen Sun, Jin-Huan Shan, Ying Liu

Turkish Journal of Chemistry

This work was primarily an experimental investigation of the bromate oscillator using 1,3-propanediol and acetone as the mixed organic substrates. The empirical equation of the induction period and oscillating period with the concentrations of the reactants and temperature were obtained. The oscillating characteristic and possible oscillation mechanism were studied.

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A Study On The Fatty Acid Composition Of Fish Liver Oil From Two Marine Fish, Eusphyra Blochii And Carcharhinus Bleekeri, Zafar S. Saify, Shamim Akhtar, Khalid Mohammed Khan, Shahnaz Perveen, Syed Abdul Majid Ayattollahi, Sohail Hassan, M. Arif, Syed Moazzam Haider, Faheem Ahmad, Sazada Siddiqui, Mohammeda Zarrar Khan Jan 2003

A Study On The Fatty Acid Composition Of Fish Liver Oil From Two Marine Fish, Eusphyra Blochii And Carcharhinus Bleekeri, Zafar S. Saify, Shamim Akhtar, Khalid Mohammed Khan, Shahnaz Perveen, Syed Abdul Majid Ayattollahi, Sohail Hassan, M. Arif, Syed Moazzam Haider, Faheem Ahmad, Sazada Siddiqui, Mohammeda Zarrar Khan

Turkish Journal of Chemistry

Two species of shark found in the coastal waters Karachi (Pakistan) were studied, Eusphyra blochii (winghead snark) and Carcharhinus bleekeri (sandbar shark) for their liver oil fatty acid composition. Since liver has high lipid content and traditionally the liver oil of these species been used to relieve muscular pain and arthritis in Pakistan this study was conducted. The isolation, identification and characterization of these fatty acids were carried out by gas liquid chromatography (GLC) and a combination of the thin layer chromatography (TLC)-GLC technique. A large variation was observed between winghead shark liver oil and sandbar shark liver oil. Twenty-five …

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Gas Chromatographic Separation Of Phenol Derivatives By Schiff-Base Liquid Crystalline Stationary Phases, M. A. Ali, A. M. Al-Haideri, M. T. S. Al-Mehdawy Jan 2003

Gas Chromatographic Separation Of Phenol Derivatives By Schiff-Base Liquid Crystalline Stationary Phases, M. A. Ali, A. M. Al-Haideri, M. T. S. Al-Mehdawy

Turkish Journal of Chemistry

The chromatographic behaviour of liquid crystalline compounds benzylidene-p-aminobenzoic acid and 4-(p-methyl benzylidene)-p-aminobenzoic acid as stationary phases for the separation of dimethylphenol isomers was investigated. These isomers were analysed on benzylidene-p-aminobenzoic acid within a nematic range of 169-194 °C with a temperature interval of 5 °C. Better peak resolution was at a column temperature of 190 °C. The analysis was repeated on a 4-(p-methyl benzylidene)-p-aminobenzoic acid column at a nematic temperature of 256 °C, which represented the end of the nematic range, and gave the optimum peak resolution. It was found that isomer better separation was obtained at 20% loading for …

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Kinetics And Mechanism Of Oxidation Of Some Hydroxy Butyric Acid Salts By Ditelluratocuprate(Iii) In Alkaline Medium, Jin-Huan Shan, Li-Ping Wang, Shi-Gang Shen, Han-Wen Sun Jan 2003

Kinetics And Mechanism Of Oxidation Of Some Hydroxy Butyric Acid Salts By Ditelluratocuprate(Iii) In Alkaline Medium, Jin-Huan Shan, Li-Ping Wang, Shi-Gang Shen, Han-Wen Sun

Turkish Journal of Chemistry

The kinetics of oxidation of 2-hydroxy butyric acid salt (2-HBAS) and 3-hydroxy butyric acid salt (3-HBAS) by ditelluratocuprate(III) (DTC) were studied spectrophotometrically between 298.2 K and 313.2 K in alkaline medium. The reaction rate showed first order dependence in DTC and a fractional order in HBAS. It was found that the pseudo-first order rate constant k_{obs} increased with an increase in the concentration of OH^- and a decrease in the concentration of TeO_{4}^{2-}. The reaction rate changed with the position of the hydroxyl group. There was a negative salt effect. A plausible mechanism involving a pre-equilibrium of adduct formation between …

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Bisabolane Type Sesquiterpenes From A Marine Didiscus Sponge, Deni̇z Taşdemi̇r, Timothy S. Bugni, Gina C. Mangalindan, Gisela P. Concepcion, Mary Kay Harper, Chris M. Ireland Jan 2003

Bisabolane Type Sesquiterpenes From A Marine Didiscus Sponge, Deni̇z Taşdemi̇r, Timothy S. Bugni, Gina C. Mangalindan, Gisela P. Concepcion, Mary Kay Harper, Chris M. Ireland

Turkish Journal of Chemistry

Two bisabolane type sesquiterpene phenols, (+)-curcuphenol (1) and (+)-curcudiol (2), were isolated from a Philippine marine sponge, Didiscus sp., in addition to \beta -sitosterol (3) and phenethylamine (4). The structures of the metabolites were established on the basis of spectral evidence (1D- and 2D NMR, [\alpha]_{D}, EIMS). (+)-Curcuphenol (1) showed cytotoxicity, which is indicative of a p53 independent mechanism.

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Crystal Structure Of Cis-Bis(N,N-Dimethyl-N'-Benzoylthioureato)Palladium(Ii), Göktürk Avşar, Hakan Arslan, Hans-Jurgen Haupt, Nevzat Külcü Jan 2003

Crystal Structure Of Cis-Bis(N,N-Dimethyl-N'-Benzoylthioureato)Palladium(Ii), Göktürk Avşar, Hakan Arslan, Hans-Jurgen Haupt, Nevzat Külcü

Turkish Journal of Chemistry

In this study cis-bis(N,N-dimethyl-N'-benzoylthioureato) palladium(II) is synthesised and the crystal structure is determined by X-ray diffraction methods. It crystallises in the space group P2_{1}/c, with a = 11.943(1) Å, b = 11.713(1) Å, c = 15.345(1) Å, \beta = 93.90(1)°, and D_{calc} = 1.616 g cm^{-1} for Z = 4. The Pd(II) atom is in a four-coordinate geometry consisting of two thiocarbonyl S and two carbonyl O atoms from two ligand groups. The Pd-S and Pd-O bond lengths are 2.2313(6) and 2.0211(16) Å, respectively.

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Bromination Of 1-Cyclopent-1-En-1-Ylbenzene And 1-(5-Bromocyclopent-1-En-1-Yl)Benzene And Theoretical Investigation Of The Products, Mustafa Ceylan, Armağan Kinal, Yaşar Sütbeyaz, Meti̇n Balci Jan 2003

Bromination Of 1-Cyclopent-1-En-1-Ylbenzene And 1-(5-Bromocyclopent-1-En-1-Yl)Benzene And Theoretical Investigation Of The Products, Mustafa Ceylan, Armağan Kinal, Yaşar Sütbeyaz, Meti̇n Balci

Turkish Journal of Chemistry

The bromination of 1-cyclopent-1-en-1-ylbenzene (4) in different solvents and at different temperatures was accompanied by the evolution of hydrogen bromide and yielded 1-(5-bromocyclopent-1-en-1-yl)benzene (8). Further bromination of 8 gave exclusively 2R(S),5R(S)-1-(1,2,5-tribromocyclopentyl)benzene (11). The experimental results were compared with the theoretical ones based on semi-empirical (MM+ and AM1), Hartree-Fock (HF) and density functional theory (DFT). The formation of 11 was explained by the formation of a weakly bridged bromoniun ion of type 9.

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Iridoid And Phenylpropanoid Glycosides From Phlomis Samia, P. Monocephala And P. Carica, Funda Nuray Yalçin, Tayfun Ersöz, Pinar Akbay, İhsan Çaliş, Ali̇ Arslan Dönmez, Otto Sticher Jan 2003

Iridoid And Phenylpropanoid Glycosides From Phlomis Samia, P. Monocephala And P. Carica, Funda Nuray Yalçin, Tayfun Ersöz, Pinar Akbay, İhsan Çaliş, Ali̇ Arslan Dönmez, Otto Sticher

Turkish Journal of Chemistry

From the aerial parts of Phlomis samia an iridoid glucoside, shanzhiside methylester (1), and three phenylethanoid glycosides, martynoside (2), 4''-O-acetylmartynoside (3) and samioside (4), were isolated. From the overground parts of P. monocephala two iridoid glucosides, lamiide (5) and ipolamiide (6), as well as three phenylethanoid glycosides, verbascoside (= acteoside) (7), forsythoside B (8), alyssonoside (9), and one lignan glucoside, syringaresinol 4'-O-\beta -D-glucopyranoside (10), were isolated. From the aerial parts of P. carica one phenylethanoid glycoside, verbascoside (= acteoside) (7) and three phenylpropanoid monomeric glucosides, syringin (11), dihydrosyringin (12) and coniferin (13), were isolated. The structures of the isolated compounds …

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Determination Of Manganese, Copper, Cadmium And Lead By Faas After Solid-Phase Extraction Of Their Phenylpiperazine Dithiocarbamate Complexes On Activated Carbon, Hasan Cesur Jan 2003

Determination Of Manganese, Copper, Cadmium And Lead By Faas After Solid-Phase Extraction Of Their Phenylpiperazine Dithiocarbamate Complexes On Activated Carbon, Hasan Cesur

Turkish Journal of Chemistry

A solid-phase extraction method was developed for the pre-concentration of manganese, copper, cadmium and lead in water samples prior to their determination by flame atomic absorption spectrometry using phenylpiperazine dithiocarbamate as a new reagent. The optimum pre-concentration conditions have been investigated such as pH, volume of sample solution and the effects of some matrix elements. The obtained recovery was nearly 90 to 100, while the enrichment factor was 400 for metal spiked solutions.

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Spectrophotometric Determination Of Iron(Ii) With 5-Nitro-6-Amino-1,10-Phenanthroline, Nebahat Demi̇rhan, Fi̇kri̇ye Tuncel Elmali Jan 2003

Spectrophotometric Determination Of Iron(Ii) With 5-Nitro-6-Amino-1,10-Phenanthroline, Nebahat Demi̇rhan, Fi̇kri̇ye Tuncel Elmali

Turkish Journal of Chemistry

A new spectrophotometric method is developed for the determination of Fe(II) with 5-nitro-6-amino-1,10-phenanthroline (NAF). In this work, the effect of factors such as pH, amount of reagent (NAF), reaction time and temperature were investigated. The method is based on the formation of a colored product between Fe(II) and NAF. The reaction proceed quantitatively at 20 °C for 210 min in acidic medium. The absorption maximum was at 520 nm. A linear relationship existed between absorbance and Fe(II) concentration over the range 0.1 \mu g/mL and 0.4 \mu g/mL. The molar ratio of Fe(II) to the reagent was determined as 1:3. …

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