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Articles 27331 - 27360 of 34726

Full-Text Articles in Physical Sciences and Mathematics

Determination Of Selenium(Iv) Using O-Phenylenediamine By Differential Pulse Polarography/Interference Of Metal Ions, Recai̇ İnam, Çi̇ğdem Toprak Jan 2004

Determination Of Selenium(Iv) Using O-Phenylenediamine By Differential Pulse Polarography/Interference Of Metal Ions, Recai̇ İnam, Çi̇ğdem Toprak

Turkish Journal of Chemistry

A new sensitive and selective pulse polarographic method for the determination of Se(IV) next to interfering ions is described. This method is based on the highly sensitive peak formed by the reaction of Se(IV) with o-phenylenediamine in Britton-Robinson buffer solution (pH 2.5) at --0.08 V vs. SCE. The new peak due to the Se(IV)/o-PDA complex not only prevents the interference of Pb(II), Cd(II) and Sn(II) for selenium, but also increases its sensitivity. A linear calibration graph is obtained for Se(IV) at a concentration of 5.0 x 10^{-8} to 6.8 x 10^{-5} M with a correlation coefficient of 0.9988. The proposed …

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A Convenient Synthesis Of 3,6-Disubstituted-1,4-Dihydro-[1,2,4,5]Tetrazines And Preparation Of New Acetic Acid Derivatives Containing 5-Oxo-4-Phenylamino- 4,5-Dihydro-[1,2,4]Triazole, Ahmet Demi̇rbaş Jan 2004

A Convenient Synthesis Of 3,6-Disubstituted-1,4-Dihydro-[1,2,4,5]Tetrazines And Preparation Of New Acetic Acid Derivatives Containing 5-Oxo-4-Phenylamino- 4,5-Dihydro-[1,2,4]Triazole, Ahmet Demi̇rbaş

Turkish Journal of Chemistry

A series of compounds 8a-e, was synthesized by condensation of compounds 7a-e with ethyl bromoacetate. The treatment of compounds 8a-e with hydrazine hydrate afforded the corresponding hydrazide derivatives (9a-e). Subsequently, compounds 9a-e were converted to alkylidene hydrazides (10a-e). Moreover, upon heating in the presence of carboxylic acids, compounds 9a-e unexpectedly gave 1,4-dihydro-[1,2,4,5]tetrazine derivatives (11a-e).

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A Rapid Spectrophotometric Method To Resolve A Binary Mixture Of Food Colorants (Riboflavine And Sunset Yellow), Mahmure Üstün Özgür Jan 2004

A Rapid Spectrophotometric Method To Resolve A Binary Mixture Of Food Colorants (Riboflavine And Sunset Yellow), Mahmure Üstün Özgür

Turkish Journal of Chemistry

A very simple and rapid spectrophotometric method using measurements at zero-crossing wavelength is described for resolving binary mixtures of riboflavine (E-101) and sunset yellow (E-110) in a powder drink. The assay procedure for E-110 and E-101 involves the extraction of the colorants from the powder drink with pH 4.5 acetate buffer, filtration, appropriate dilution, and measurement of the first derivative absorbance values (denoted as ^1D). Calibration graphs are linear up to 25.0 \mu g.mL^{-1} for E-101 and 40.0 \mu g.mL^{-1} for E-110. The sensitivity and reproducibility of the method were determined by using the synthetic mixtures in different ratios prepared …

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A Sensitive Spectrophotometric Assay For Tinidazole And Metronidazole Using A Pd-C And Formic Acid Reduction System, Nandipura Dyavegowda Dinesh, Padmarajaiah Nagaraja, K. Subbegowda Rangappa Jan 2004

A Sensitive Spectrophotometric Assay For Tinidazole And Metronidazole Using A Pd-C And Formic Acid Reduction System, Nandipura Dyavegowda Dinesh, Padmarajaiah Nagaraja, K. Subbegowda Rangappa

Turkish Journal of Chemistry

A simple, sensitive and rapid spectrophotometric method for the determination of tinidazole (TZ) and metronidazole (MZ) in pure as well as in dosage form is described. The method is based on the reduction of the nitro group of drugs using a novel and versatile reduction system comprising 10% Pd-C and formic acid. The resulting amine was then subjected to a condensation reaction with sodium 1,2-naphthaquinone-4-sulfonate (NQS) to form red Schiff base with an absorption maximum at 510 nm. Beer's law was obeyed in the concentration ranges 2.0 to 45.0 \mu g mL^{-1} and 1.5 to 37.0 \mu g mL^{-1} with …

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Facile Synthesis Of Hydantoin Derivatives Under Microwave Irradiation, Khalil Faghihi, Khosrow Zamani, Akbar Mobinikhaledi Jan 2004

Facile Synthesis Of Hydantoin Derivatives Under Microwave Irradiation, Khalil Faghihi, Khosrow Zamani, Akbar Mobinikhaledi

Turkish Journal of Chemistry

The rapid and highly efficient synthesis of hydantoin derivatives 3(a-f) was achieved under microwave irradiation by using a domestic microwave oven from the reactions of cyanohydrin derivatives 2(a-f) with ammonium carbonate. The reaction proceeded rapidly (2-5 min.), and as a result a series of hydantoin derivatives 3(a-f) were obtained in high yields. All of the synthesized compounds were fully characterized by their melting point, ^1H-NMR, FTIR spectroscopy and elemental analyses. Cyanohydrin derivatives 2(a-f) were also prepared from the ketone derivatives 1(a-f) with potassium cyanide in the presence of sodium metabisulfite in an additional reaction.

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The Kinetics Of The Photochemical Reaction Of Methylene Green With Methylamine And Ethylamine, Rehana Saeed, Fahim Uddin, Zahida Khalid Jan 2004

The Kinetics Of The Photochemical Reaction Of Methylene Green With Methylamine And Ethylamine, Rehana Saeed, Fahim Uddin, Zahida Khalid

Turkish Journal of Chemistry

The photochemical reduction of methylene green with methylamine and ethylamine in 50% aqueous isopropanol was studied. The photochemical reduction was carried out in a special type of optical processor associated with a deoxygenating system, a temperature controlling unit and a magnetic stirring system. A monochromatic light of 657 nm wavelength was used for irradiation of oxygen free reaction solutions in a double walled reaction cell. The transmitted light was measured and recorded in terms of electrical signals with the help of a calibrated galvanometer. Acidities of the solutions were measured with the help of a spectrophotometer based on the Hammet …

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Electrocatalytic Determination Of Ascorbic Acid Using Glassy Carbon Modified With Nickel(Ii) Macrocycle Containing Dianionic Tetraazaannulene Ligand, Mozhgan Khorasai-Motlagh, Meissam Noroozifar Jan 2004

Electrocatalytic Determination Of Ascorbic Acid Using Glassy Carbon Modified With Nickel(Ii) Macrocycle Containing Dianionic Tetraazaannulene Ligand, Mozhgan Khorasai-Motlagh, Meissam Noroozifar

Turkish Journal of Chemistry

A symmetric Ni(II) tetraaza macrocycle modified glassy electrode shows electrocatalytic activity for the oxidation of L-ascorbic acid at pH 7. It was shown the peak potential shifted to the negative by 250 mV compared with that for the bare electrode in the cyclic voltammograms. The calibration curve was linear up to 5 mM with a detection limit of 2.5 \times 10^{-4} mM and RSD% better than 2.8%. Excipients used as additives in pharmaceutical formulations and foods did not interfere in the proposed procedure. This new modified electrode was applied to commercial pharmaceutical tablets, injections and foods. The obtained results were …

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Formation Of The Monolithic Silica Gel Column With Bimodal Pore Structure, Wenhui Gao, Gegliang Yang, Jing Yang, Haiyan Liu Jan 2004

Formation Of The Monolithic Silica Gel Column With Bimodal Pore Structure, Wenhui Gao, Gegliang Yang, Jing Yang, Haiyan Liu

Turkish Journal of Chemistry

A biporous monolithic silica gel column possessing both micrometer sized through-pores and nanometer sized mesopores located in the silica skeletons was prepared and the high concentration porogen (e.g., 2 mol/L ammonium hydroxide solution) was use for increasing mesopore size in this work. The mechanism for the preparation of the monolithic column was investigated in detail. Moreover, the effect of the polyethylene glycol concentration in the starting solution was studied and it was found that a lower concentration range was also suitable for forming the interconnected porous structure for the monolithic silica gel column. At lower concentrations, however, the phase separation …

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Anionic Polymerization Of Methyl Methacrylate As Promoted By A N-Butyl Lithium-Pyridazine-Polyether Alkoxide Based Complex Initiator System, Z. Tim Hamaudi, Ni̇han Nugay, Turgut Nugay Jan 2004

Anionic Polymerization Of Methyl Methacrylate As Promoted By A N-Butyl Lithium-Pyridazine-Polyether Alkoxide Based Complex Initiator System, Z. Tim Hamaudi, Ni̇han Nugay, Turgut Nugay

Turkish Journal of Chemistry

Polymerization of methyl methacrylate was conducted using a n-butyl lithium/pyridazine system as initiator in tetrahydrofuran (THF) and toluene. Special attention was focused on using some lithium polyether alkoxides as polymerization is promoted at ambient temperatures. The positive effects of these \mu /\sigma -type ligands such as lithium 2-(2-methoxyethoxy)ethoxide and lithium 2-(methoxy)ethoxide on controlling the living character, molecular weight, stereoregularity and yield of the produced polymers were all demonstrated. It was found that initiator/lithium-2-(methoxy)ethoxide in a 1/10 ratio gives the most controlled polymerization. All products were then characterized by size exclusion chromatography (SEC), proton nuclear magnetic resonance (^1H NMR) and differential …

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An Efficient Synthesis Of Substituted 4-Aryl-3-Cyano-2-Amino Thiophenes By A Stepwise Gewald Reaction, Ferhan Tümer, Duygu Eki̇nci̇, Kani̇ Zi̇lbeyaz, Ümi̇t Demi̇r Jan 2004

An Efficient Synthesis Of Substituted 4-Aryl-3-Cyano-2-Amino Thiophenes By A Stepwise Gewald Reaction, Ferhan Tümer, Duygu Eki̇nci̇, Kani̇ Zi̇lbeyaz, Ümi̇t Demi̇r

Turkish Journal of Chemistry

The title compounds were efficiently synthesised starting from aryl methyl ketones in 3 steps. Knoevenagel condensation of aryl methyl ketones with malononitrile gave the corresponding crotonitriles (5a-f). Methyl groups of the crotonitriles (5a-f) were then efficiently brominated by refluxing and lightening the reaction media to give bromocrotonitriles (6a-f). The bromocrotonitriles (6a-f) were finally cyclised by treatment with NaSH to give the title compounds.

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Synthesis, Magneto-Spectral And Thermal Characteristics Of Some 7-Coordinated Compounds Of Lanthanides(Iii) Chlorides With 4[(Furan-2-Ylmethylene)Amino]-1,5-Dimethyl-2-Phenyl Pyrazol-3-One And Isonicotinic Acid(3',4',5'-Trimethoxybenzylidene)Hydrazide, Ram K. Agarwal, Surendra Prasad, Neetu Goel Jan 2004

Synthesis, Magneto-Spectral And Thermal Characteristics Of Some 7-Coordinated Compounds Of Lanthanides(Iii) Chlorides With 4[(Furan-2-Ylmethylene)Amino]-1,5-Dimethyl-2-Phenyl Pyrazol-3-One And Isonicotinic Acid(3',4',5'-Trimethoxybenzylidene)Hydrazide, Ram K. Agarwal, Surendra Prasad, Neetu Goel

Turkish Journal of Chemistry

In the present work, we describe the isolation of some lanthanide(III) chlorides coordination compounds with 4[(furan-2-ylmethylene)amino]-1,5-dimethyl-2-phenyl pyrazol-3-one (FDPPO) and isonicotinic acid(3',4',5'-trimethoxybenzylidene)hydrazide (ITMBH) with the general composition [Ln(L)_2Cl_3] (Ln = La, Pr, Nd, Sm, Gd, Tb, Dy or Ho; L = FDPPO or ITMBH). All the isolated compounds were characterized through various physico-chemical studies. The coordinating ligands FDPPO or ITMBH act as neutral bidentate N and O-donors in the present compounds. The central metal ion displays the coordination number 7 in these complexes. Thermal stabilities of these complexes were also studied through thermogravimetric analysis.

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Photophysical Properties And Electrochemistry Of The N,N'-Bis-N-Butyl Derivative Of Naphthalene Diimide, Yevgen Posokhov, Serap Alp, Banu Köz, Yusuf Di̇lgi̇n, Siddik İçli̇ Jan 2004

Photophysical Properties And Electrochemistry Of The N,N'-Bis-N-Butyl Derivative Of Naphthalene Diimide, Yevgen Posokhov, Serap Alp, Banu Köz, Yusuf Di̇lgi̇n, Siddik İçli̇

Turkish Journal of Chemistry

The spectral-luminescent properties and electrochemistry of the N,N'-bis-n-butyl derivative of naphthalene diimide were studied. The main photophysical parameters (quantum yield, rate constants of fluorescence and of non-radiative deactivation and fluorescence lifetime) were determined. The LUMO value (-3.51 eV) was determined by cyclic voltammetry. The N,N'-bis-n-butyl derivative of naphthalene diimide (BBND) shows 2 reversible reduction steps (-1.19 V and -1.75 V vs. Ferrocene) in chloroform. Quenching the fluorescence emissions of aromatic donor molecules in acetonitrile revealed the electron acceptor ability of the studied naphthalene diimide derivative. It has been found that, in contrast to perylene diimide derivatives, which form \pi-electron donor-acceptor …

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Diffusion Effect On The Anodic Reactions Of Tungsten, Mustafa Anik, Tuba Cansizoğlu, Si̇nem Çevi̇k Jan 2004

Diffusion Effect On The Anodic Reactions Of Tungsten, Mustafa Anik, Tuba Cansizoğlu, Si̇nem Çevi̇k

Turkish Journal of Chemistry

Potentiodynamic and potentiostatic polarizations, and a rotating disk electrode technique were used to study the influence of diffusion on the anodic reactions of tungsten (W) in a broad pH range (\sim 0.3--13.5) in H_3PO_4 buffered solutions. The anodic current was controlled totally by the kinetics of H^+ -assisted dissolution below pH 1 (Region A). At around pH 2.5 (Region B), in addition to the kinetics of H_2O-assisted dissolution, specimen rotation had an effect on the current. This observation was attributed mainly to the physical damage to an oxide phase by hydrodynamic effects and partly to the diffusion of surface H_2WO_4(aq) …

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Synthesis And Microbiological Activity Of Some Substituted N-(2-Hydroxy-4-Nitrophenyl)Benzamides And Phenylacetamides As Possible Metabolites Of Antimicrobial Active Benzoxazoles, İlkay Yildiz Ören, Esi̇n Aki Şener, Cengi̇z Ertaş, Özlem Temi̇z Arpaci, İsmai̇l Yalçin, Nurten Altanlar Jan 2004

Synthesis And Microbiological Activity Of Some Substituted N-(2-Hydroxy-4-Nitrophenyl)Benzamides And Phenylacetamides As Possible Metabolites Of Antimicrobial Active Benzoxazoles, İlkay Yildiz Ören, Esi̇n Aki Şener, Cengi̇z Ertaş, Özlem Temi̇z Arpaci, İsmai̇l Yalçin, Nurten Altanlar

Turkish Journal of Chemistry

Some new antimicrobial active N-(2-hydroxy-4-nitrophenyl)- p-substituted benzamide and phenylacetamide analogues (I-II) were prepared by 2-step procedures from the corresponding carboxylic acids as possible metabolites of benzoxazoles. Their antimicrobial activities were tested against 3 Gram-positive and 2 Gram-negative bacteria with the fungus Candida albicans and were also compared with several control drugs. The compounds Ia, Id, IIa, and IIe were active at a MIC value of 12.5 \mu g/mL against the Gram-positive microorganism Bacillus subtilis. Most of the compounds exhibited antifungal activity at a MIC value of 12.5 \mu g/mL against C. albicans. On the other hand, the antimicrobial activity of …

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Naphthoquinones From The Roots Of Onosma Argentatum Hub.-Mor. (Boraginaceae), Ufuk Özgen, Maksut Coşkun, Cavi̇t Kazaz, Hasan Seçen Jan 2004

Naphthoquinones From The Roots Of Onosma Argentatum Hub.-Mor. (Boraginaceae), Ufuk Özgen, Maksut Coşkun, Cavi̇t Kazaz, Hasan Seçen

Turkish Journal of Chemistry

Onosma argentatum Hub.-Mor. is an endemic species growing in Turkey. In this study, the roots of O. argentatum were extracted with n-hexane-dichloromethane (1:1). The extract was separated on a silica gel column eluting with n-hexane-ethyl acetate by gradient elution. New naphthoquinone compounds (3 known and 1 new) were isolated and their structures were elucidated by spectroscopic methods as deoxyshikonin, acetyl shikonin, 3-hydroxy-isovaleryl shikonin, and 5,8-O-dimethyl acetyl shikonin.

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Phenolic Compounds From Globularia Cordifolia, Hasan Kirmizibekmez, İhsan Çaliş, Sonia Piacente, Cosimo Pizza Jan 2004

Phenolic Compounds From Globularia Cordifolia, Hasan Kirmizibekmez, İhsan Çaliş, Sonia Piacente, Cosimo Pizza

Turkish Journal of Chemistry

From the methanolic extract of the underground parts of Globularia cordifolia, a new neolignan diglycoside, dehydrodiconiferyl alcohol 9-O-\beta -D-glucopyranosyl-(1 \to 2)-\beta -D-glucopyranoside (1) was isolated along with a known neolignan glycoside, dehydrodiconiferyl alcohol 9-O-\beta -D-glucopyranoside (2). In addition, 2 flavone glycosides, chrysoeriol 7-O-\beta -D-allopyranosyl-(1 \to 2)-\beta -D-glucopyranoside (3), stachyspinoside (4) and 5 phenylethanoid glycosides, verbascoside (5), isoverbascoside (6), leucosceptoside A (7), martynoside (8) and rossicaside A (9) were obtained and characterized. The structures of the isolates were established by 1D and 2D NMR spectroscopy in combination with IR, UV and MS analysis.

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Synthesis And Antinociceptive Activity Of 2-[(2-Oxobenzothiazolin-3-Yl)Methyl]- 5-Aminoalkyl/Aryl-1,3,4-Thiadiazole, Ti̇jen Önkol, Bi̇lge Çakir, M. Fethi̇ Şahi̇n, Engi̇n Yildirim, Kevser Erol Jan 2004

Synthesis And Antinociceptive Activity Of 2-[(2-Oxobenzothiazolin-3-Yl)Methyl]- 5-Aminoalkyl/Aryl-1,3,4-Thiadiazole, Ti̇jen Önkol, Bi̇lge Çakir, M. Fethi̇ Şahi̇n, Engi̇n Yildirim, Kevser Erol

Turkish Journal of Chemistry

Ten 2-[(2-oxobenzothiazolin-3-yl)methyl]-5-aminoalkyl/aryl-1,3,4-thiadiazole derivatives were synthesized. The chemical structures of these compounds were elucidated by their FT-IR and ^1H-NMR spectral data, as well as their elemental analyses. The compounds were tested for antinociceptive activity. Among these compounds, 2-[(2-oxobenzothiazolin-3-yl)methyl]-5-aminomethyl-1,3,4-thiadiazole (5a) was found to be significantly more active than the others and the standards in all the tests.

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Photoinitiated Crosslinking And Grafting Of Methylmethacrylate Using N,N-Dimethyl Amino Functional Polystyrene Block Copolymers, Ali̇ Ekrem Müftüoğlu, Yusuf Yağci, Kazunori Se Jan 2004

Photoinitiated Crosslinking And Grafting Of Methylmethacrylate Using N,N-Dimethyl Amino Functional Polystyrene Block Copolymers, Ali̇ Ekrem Müftüoğlu, Yusuf Yağci, Kazunori Se

Turkish Journal of Chemistry

Monodisperse poly(N,N-dimethyl-4-vinylphenethylamine)-block-polystyrene was synthesized via anionic living polymerization carried out at -78 °C under a pressure of 10^{-6} torr using cumyl potassium as the initiator. Subsequent photoinduced radical polymerization of styrene through side chain-functional N,N-dimethyl amino groups yielded a crosslinked polymer and a brush type block-graft copolymer to a lesser extent. Upon irradiation at a wavelength of 350 nm, macroradicals were generated via hydrogen abstraction from amino side-chain groups by the excited benzophenone. The block-graft copolymer was characterized by ^1H-NMR, IR, and GPC analysis.

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Thermally Induced Cationic Polymerization Of 2-Ethyl-2-Oxazoline By Benzyl Pyridinium And Anilinium Salts, Hali̇l Ki̇rli̇bal, Yusuf Yağci Jan 2004

Thermally Induced Cationic Polymerization Of 2-Ethyl-2-Oxazoline By Benzyl Pyridinium And Anilinium Salts, Hali̇l Ki̇rli̇bal, Yusuf Yağci

Turkish Journal of Chemistry

N-Benzyl pyridinium (BP), N-benzyl o-cyano pyridinium (BoCP), N-benzyl p-cyanopyridinium (BpCP), N-benzyl N, N-dimethyl anilinium (BDA) and benzyl triphenyl phosphonium (BTP) salts with bromide counter anion, thermal initiators for cationic polymerization, were synthesized and characterized. Their capability to act as initiators for the polymerization of 2-ethyl-2-oxazoline (EOZO) was examined. The postulated mechanism is based on the generation of benzyl bromide by the thermolysis of either BoCP or BDA that reacts with the monomer, EOZO. The polymerization proceeds via an oxazolonium bromide as the propagating end. BP, BoCP and BTP were found to be unreactive towards EOZO.

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The Hydrodynamic Properties Of Micelles Formed By Block Copolymers Of Isoprene And Tert-Butylacrylate In N-Octane, Hali̇l İbrahi̇m Ünal, Colin Price Jan 2004

The Hydrodynamic Properties Of Micelles Formed By Block Copolymers Of Isoprene And Tert-Butylacrylate In N-Octane, Hali̇l İbrahi̇m Ünal, Colin Price

Turkish Journal of Chemistry

The hydrodynamic properties of micelles formed by 2 block copolymers of isoprene and tert-butylacrylate in n-octane were investigated by dynamic light scattering (DLS) over a range of temperatures and concentrations using both the cumulants and histogram methods. By means of the histogram method it was possible to determine the average hydrodynamic diameters of both micelles and unassociated-chains in the same solution. It was also used to determine the z-average fraction of unassociated-chains at a particular concentration and temperature, and it provided an alternative route when combined with static light scattering (SLS) for determining the thermodynamics of micellisation. The overall-average diffusion …

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Genetic Multivariate Calibration Methods For Near Infrared (Nir) Spectroscopic Determination Of Complex Mixtures, Durmuş Özdemi̇r, Betül Öztürk Jan 2004

Genetic Multivariate Calibration Methods For Near Infrared (Nir) Spectroscopic Determination Of Complex Mixtures, Durmuş Özdemi̇r, Betül Öztürk

Turkish Journal of Chemistry

The simultaneous determination of ternary mixtures of methylene chloride, ethyl acetate, and methanol using near infrared (NIR) spectroscopy and 4 different genetic algorithms based multivariate calibration methods was demonstrated. The 4 genetic multivariate calibration methods are genetic partial least squares (GPLS), genetic regression (GR), genetic classical least squares (GCLS) and genetic inverse least squares (GILS). The sample data set contains the NIR spectra of 63 ternary mixtures and covers the range from 900 to 2000 nm in 2 nm intervals. Of these 63 spectra, 42 were used as the calibration set, and 21 were reserved for the prediction purposes. Several …

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Stereoselective Photochemistry Of Methoxy Chalcones In Solution And Their Radical Scavenging Activity, Nuretti̇n Yayli, Osman Üçüncü, Ahmet Yaşar, Yaşar Gök, Murat Küçük, Sevgi̇ Kolayli Jan 2004

Stereoselective Photochemistry Of Methoxy Chalcones In Solution And Their Radical Scavenging Activity, Nuretti̇n Yayli, Osman Üçüncü, Ahmet Yaşar, Yaşar Gök, Murat Küçük, Sevgi̇ Kolayli

Turkish Journal of Chemistry

The photochemical dimerization of 3 known methoxy derivatives of chalcones, (2E)-1-(2-methoxy)phenyl-3-phenylpropen-1-one (1), (2E)-1-(3-methoxy)phenyl-3-phenyl-propen-1-one (2), and (2E)-1-(4-methoxy) phenyl-3-phenylpropen-1-one (3), yielded 3 new \delta -truxinic type dimers in solution: rel-(1\beta ,2\alpha)- di-(2-methoxy)-benzoyl-rel-(3\beta ,4\alpha )-diphenylcyclobutane (4), rel-(1\beta ,2\alpha )-di-(3-methoxy)benzoyl-rel-(3\beta, 4\alpha )-diphenylcyclobutane (5), and rel-(1\beta ,2\alpha)- di-(4-methoxy)benzoyl-rel-(3\beta ,4\alpha )-diphenylcyclobutane (6), stereoselectively. Precursor chalcones showed high superoxide radical scavenging activity although the dimers were inactive.

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Electrochemical Detection Of Specific Dna Sequences From Pcr Amplicons On Carbon And Mercury Electrodes Using Meldola's Blue As An Intercalator, Kagan Kerman, Di̇lşat Özkan, Pinar Kara, Hakan Karadeni̇z, Zeynep Özkan, Arzum Erdem, Frantisek Jelen, Mehmet Özsöz Jan 2004

Electrochemical Detection Of Specific Dna Sequences From Pcr Amplicons On Carbon And Mercury Electrodes Using Meldola's Blue As An Intercalator, Kagan Kerman, Di̇lşat Özkan, Pinar Kara, Hakan Karadeni̇z, Zeynep Özkan, Arzum Erdem, Frantisek Jelen, Mehmet Özsöz

Turkish Journal of Chemistry

The electrochemical parameters for 7--dimethyl--amino--1,2-- benzophenoxazinium Meldola's Blue, (MDB) on binding to DNA at both a hanging mercury drop electrode (HMDE) and carbon paste electrode (CPE) are described. MDB, which interacts with immobilized calf thymus DNA, was detected using double stranded DNA modified HMDE or CPE (dsDNA modified HMDE or CPE), bare HMDE or CPE and single stranded DNA modified HMDE or CPE (ssDNA modified HMDE or CPE) in combination with adsorptive transfer stripping voltammetry (AdTSV) techniques and decreased peak currents were observed. The discrimination of dsDNA and ssDNA and detection of hybridization between synthetic oligonucleotides were determined from changes …

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Defect Structure And Properties Of Sr-Doped La Cr O_{3-\Delta}, Mahmoud Omari, Ilhem Chadli, Salah Belaidi Jan 2004

Defect Structure And Properties Of Sr-Doped La Cr O_{3-\Delta}, Mahmoud Omari, Ilhem Chadli, Salah Belaidi

Turkish Journal of Chemistry

A defect chemical model for the behavior of acceptor-doped LaCrO_3 as a function of oxygen pressure is proposed. This is considered within the regime that corresponds to oxygen deficit oxygen. The mathematical approach allows us to calculate the oxygen partial pressure dependant properties of La_{1-x} Sr_x Cr O_{3-\delta} in the range 0.10 \le x \le 0.30. The results show that the conductivity was independent of pO_2 and was proportional to the dopant concentration at high pO_2. Therefore, under reducing conditions, the conductivity decreased exponentially with decreasing pO_2 and asymptotically approached a pO_2^{1/4} relationship. Stability regimes and compensation mechanisms at various …

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Purification And Characterization Of Pear (Pyrus Communis) Polyphenol Oxidase, Emi̇ne Zi̇yan, Şule Pekyardimci Jan 2004

Purification And Characterization Of Pear (Pyrus Communis) Polyphenol Oxidase, Emi̇ne Zi̇yan, Şule Pekyardimci

Turkish Journal of Chemistry

Three isoenzymes of polyphenol oxidase (PPO) were isolated from a local pear variety (Ankara Armutu) through ammonium sulfate precipitation, dialysis and gel filtration. The sample obtained from dialysis after ammonium sulfate precipitation was used for characterization of the partially purified enzyme. Optimum pH values of PPO were 8.2 for pyrogallol, 7.2 for 4-methylcatechol, 7.0 for catechol, 5.6 for D-tyrosine, 5.0 for p-cresol and 4.8 for L-dopa. The optimum temperature of PPO was 35 °C with 4-methylcatechol. Catechol was oxidized more rapidly than the other substrates; however, 4-methylcatechol, chlorogenic acid and caffeic acid were also good substrates. The effect of 6 …

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Synthesis Of Novel 4-Alkylidene- And 4-Alkylamino-5-Oxo-4,5-Dihydro-[1,2,4] Triazole Derivatives And Investigation Of Their Antitumor Activities, Nesli̇han Demi̇rbaş, Reyhan Uğurluoğlu Jan 2004

Synthesis Of Novel 4-Alkylidene- And 4-Alkylamino-5-Oxo-4,5-Dihydro-[1,2,4] Triazole Derivatives And Investigation Of Their Antitumor Activities, Nesli̇han Demi̇rbaş, Reyhan Uğurluoğlu

Turkish Journal of Chemistry

A series of novel 3-alkyl-4-cyclohexylmethylenamino-5-oxo-4,5-dihydro-[1,2,4]triazoles (6a-e) and 3-alkyl-4-hexylidenamino-5-oxo-4,5-dihydro-[1,2,4]triazoles (7b-e) were synthesized from the reaction of corresponding 3-alkyl-4-amino-5-oxo-4,5-dihydro-[1,2,4]triazoles (1) with cyclohexancarboxaldehyde and capronaldehyde. The acetylation of compounds 6e and 7b resulted in the formation of 1-acetyl-4- cyclohexylmethylenamino-5-oxo-3-(p-tolyl)-4,5-dihydro-[1,2,4]triazole (10) and 3-benzyl-4-hexylidenamino-5-oxo-4,5-dihydro-[1,2,4]triazole (11). 3-Alkyl-4-cyclohexylmethylamino-5-oxo-4,5-dihydro-[1,2,4]triazoles (8a-e) and 3-alkyl-4-hexylamino-5-oxo-4,5-dihydro-[1,2,4]triazoles (9b-e) were obtained from the selective reduction of compounds 6a-e and 7b-e with NaBH_4. The in vitro antitumor activity of some selected compounds was screened by the National Cancer Institute (USA) against several human tumor cell lines, and compounds 8c, 9d and 11c were found to be active.

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Rapid Complexometric Determination Of Mercury(Ii) Using Glutathione As A Selective Demasking Reagent, Prakash Shetty, A. Nithyananda Shetty Jan 2004

Rapid Complexometric Determination Of Mercury(Ii) Using Glutathione As A Selective Demasking Reagent, Prakash Shetty, A. Nithyananda Shetty

Turkish Journal of Chemistry

A simple, rapid and selective complexometric method is proposed for the determination of mercury(II) in the presence of associated metal ions. Mercury(II) is first complexed with an excess of EDTA and the surplus EDTA is titrated against standard zinc sulphate solution at pH 5-6 using xylenol orange indicator. Glutathione is then added to displace EDTA from the Hg-EDTA complex quantitatively and the EDTA released is back titrated against a standard zinc sulphate solution as before. The method works well in the range 4 to 80 mg of mercury with a relative error of less than 0.30% and a coefficient of …

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Direct Dyes Derived From 4,4'-Diaminobenzanilide Synthesis, Characterization And Toxicity Evaluation Of A Disazo Symmetric Direct Dye, Georgeta Maria Simu, Sergiu Adrian Chicu, Nicole Morin, Walter Schmidt, Eugen Şişu Jan 2004

Direct Dyes Derived From 4,4'-Diaminobenzanilide Synthesis, Characterization And Toxicity Evaluation Of A Disazo Symmetric Direct Dye, Georgeta Maria Simu, Sergiu Adrian Chicu, Nicole Morin, Walter Schmidt, Eugen Şişu

Turkish Journal of Chemistry

The synthesis of a new symmetric disazo direct dye containing the non--carcinogenic 4,4'-diaminobenzanilide as the middle component and salicylic acid as the coupling component is presented. The synthesized dye is an analog of the benzidine based dye C. I. Direct Yellow 1 (C. I. 22,250) and was analyzed by thin layer chromatography (TLC), electronic spectra (VIS) and mass spectroscopy (FAB-MS). The coloristic and fastness properties of the synthesized dye were determined and compared with those of C. I. Direct Yellow 1. The toxicities of the dye and of its precursors were evaluated by biological tests, using the process of metamorphosis …

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Electrorheological Properties Of Suspensions Prepared From Poly(Li-Tert-Butyl Methacrylate) Ionomer, Mustafa Yavuz, Hali̇l İbrahi̇m Ünal Jan 2004

Electrorheological Properties Of Suspensions Prepared From Poly(Li-Tert-Butyl Methacrylate) Ionomer, Mustafa Yavuz, Hali̇l İbrahi̇m Ünal

Turkish Journal of Chemistry

The synthesis, characterisation and partial hydrolysis of poly(tert-butylmethacrylate), (PTBMA), and the electrorheological (ER) properties of its suspensions were investigated. The polymer was synthesised by radical polymerisation and partially hydrolysed by para-toluenesulphonic acid monohydrate (PTSA.H_2O), and then converted to a lithium salt (PTBMA-Li) by washing with a LiOH_{(aq)} solution. From particle size measurements, the average particle size of PTBMA-Li was determined to be 74 \mu m. Colloidal suspensions of ionomer were prepared in various insulating oils [silicone oil (SO), mineral oil (MO), threeoctylthreemellitate (TOTM) and dioctylphatalete (DOP)] at a series of concentrations (c = 5-33 m/m, %). The sedimentation stabilities of …

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Separation Of Abscisic Acid, Indole-3-Acetic Acid, Gibberellic Acid In 99 R (Vitis Berlandieri X Vitis Rupestris) And Rose Oil (Rosa Damascena Mill.) By Reversed Phase Liquid Chromatography, Mustafa Kelen, Ebru Çubuk Demi̇ralay, Songül Şen, Güleren Özkan Alsancak Jan 2004

Separation Of Abscisic Acid, Indole-3-Acetic Acid, Gibberellic Acid In 99 R (Vitis Berlandieri X Vitis Rupestris) And Rose Oil (Rosa Damascena Mill.) By Reversed Phase Liquid Chromatography, Mustafa Kelen, Ebru Çubuk Demi̇ralay, Songül Şen, Güleren Özkan Alsancak

Turkish Journal of Chemistry

Plant hormones, specialized chemical substances produced by plants, are the main internal factors controlling growth and development. In this study the pH and polarity of the mobile phase were taken into consideration to optimize the mobile phase for the chromatographic separation of 3 important plant hormones: abscisic acid (ABA), indole-3-acetic acid (IAA) and gibberellic acid (GA_3). pK_a values of ABA, IAA and GA_3 were determined using retention factors. These 3 hormones were extracted from 99 R (Vitis berlandieri x Vitis rupestris) and rose oil (Rosa damascena Mill.) and the chromatographic method developed was used for the separation of these hormones.

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