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Articles 2581 - 2608 of 2608
Full-Text Articles in Physical Sciences and Mathematics
The Facile Synthesis Of Cyclopentanoid Antibiotic Kjellmanianone, Ayhan S. Demi̇r, Cihangir Tanyeli̇, Volkan Gülbeyaz, Hülya Akgül
The Facile Synthesis Of Cyclopentanoid Antibiotic Kjellmanianone, Ayhan S. Demi̇r, Cihangir Tanyeli̇, Volkan Gülbeyaz, Hülya Akgül
Turkish Journal of Chemistry
The synthesis of cyclopentanoid antibiotic Kjellmanianone is described in this study. The C-acylation of lithium enolates of 3-Methoxycyclopentenone by N-carbomethoxyimidazole or methylcyanoformate \beta-ketoester, which when oxidized with Mn(III) acetate produces kjellmanianone in good yield.
An Amperometric Biosensor For The Determination Of Organophosphorus Pesticides, Azmi Telefoncu
An Amperometric Biosensor For The Determination Of Organophosphorus Pesticides, Azmi Telefoncu
Turkish Journal of Chemistry
Organophosphorus pesticides are inhibitors of cholinesterase and this enzyme is used as a monitoring system for pesticides containing organophosphorus compounds. The decrease in activity of cholinesterase is monitored by the choline sensor and is correlated to the concentration of pesticide present in solution. According to this observation a biosensor for pesticides was determined. This biosensor consists of a Clark oxygen electrode, modified with cellulose acetate and dialysis membranes. Between the two membranes there are two immobilized enzymes: acetyl-cholinesterase and choline oxidase.
A Comparison Of Normal(-Cn) And Reversed (C-18) Phase Chromatographic Behaviour Of Polycyclic Aromatic Hydrocarbons, S. Fatma Aygün, Mustafa Özci̇mder
A Comparison Of Normal(-Cn) And Reversed (C-18) Phase Chromatographic Behaviour Of Polycyclic Aromatic Hydrocarbons, S. Fatma Aygün, Mustafa Özci̇mder
Turkish Journal of Chemistry
Because of the well-known carcinogenic and mutagenic character of polycyclic aromatic hydrocarbons (PAHs), still new methods have been tried for their qualitative and quantitative determinations in various smaples. Liquid chromatography is one of the most widely applied techniques. In this study we used liquid chromatography in normal and reversed phase modes for the determinations of PAHs and tried to find a relation between the retention times and various parameters, such as molecular shape, water solubility and number of carbon atoms.
Adsorption Of Monovalent Cationic Dyes On Some Silicates, Oğuz İnel, Ayşegül Aşkin (Börekçi̇)
Adsorption Of Monovalent Cationic Dyes On Some Silicates, Oğuz İnel, Ayşegül Aşkin (Börekçi̇)
Turkish Journal of Chemistry
Adsorption of two cationic dyes, methylene blue (MB) and malachite green (MG), was studied on the bentonite, sepiolite and zeolite samples by the batch equilibration technique using a spectrophotometer. In addition, cation exchange capacities (CEC) of samples were determined by NH_4^{+} saturation using Kjeldhal distillation. The adsorption data was found to conform with the Langmuir equation within the concentration range studied, and Langmuir constants were determined for each of the samples. It was observed that the amount of dyes adsorbed was in excess of CEC in the case of bentonite and sepiolite. The adsorption capacities of the samples for both …
Synthesis, Characterization And Formation Kinetics Of Sn(Ii) And (Iv)-Schiff Base Complexes, Yakup Baran, Birgül Erk
Synthesis, Characterization And Formation Kinetics Of Sn(Ii) And (Iv)-Schiff Base Complexes, Yakup Baran, Birgül Erk
Turkish Journal of Chemistry
The synthesis and characterization of Sn(II) and Sn(IV) complexes of nitrogen and oxygen ligands, {\it p}-dimethyl aminophenylenesalicyladimine ( DPS), N,N'phenylenebis(salicylaldimine)(PBS) and N, N'-triethylenetetramine bis (salicylaldimine)(TTS) are reported. The structure of free ligands and their tin complexes were determined by elemental analysis, ir and nmr measurements. The kinetics of formation of the complexes were studied by stopped-flow technique at several temperatures with \mu=0.100 M (NaClO_{ 4}). Activation parameters \Delta H^{\ast} and \Delta S^{\ast} were determined.
A Novel And Stereospecific Synthesis Of Conduritol-E Via Cyclohexa-3,5-Diene-1,2-Diol, Ahmet Maras, Hasan Secen, Yasar Sütbeyaz, Metin Balci
A Novel And Stereospecific Synthesis Of Conduritol-E Via Cyclohexa-3,5-Diene-1,2-Diol, Ahmet Maras, Hasan Secen, Yasar Sütbeyaz, Metin Balci
Turkish Journal of Chemistry
Conduritol-E was synthesized starting from cyclohexa-3,5-diene-1,2-diol {\bf 1a} in six steps. Acetylation of the diol {\bf 1a} followed by bromination gave (2\alpha/1\beta, \,\, 3\beta, \,\, 4\beta)-1,2-dibromo-2,3- diacetoxy- 5-cyclohexene {\bf 3} as main product. KMnO_{4}-hydoxylation of the dibromide {\bf 3} followed by acetylation, Zn-elimination and hydrolysis afforded conduritol-E {\bf 5a}.
Chemistry Of Aerosol In Uludağ National Park, Serpil Y. Karakaş, Semra G. Tuncel
Chemistry Of Aerosol In Uludağ National Park, Serpil Y. Karakaş, Semra G. Tuncel
Turkish Journal of Chemistry
Chemical composition of aerosol samples which were collected daily during September 1993 - April 1994 was examined by determining the concentrations and variations of major ions in aerosol samples, determining the binary correlations and the sources of them. Sulfate made up the 30% of aerosol mass with an 2.14 \mug m^{-3} average concentration. Measured chemical parameters in Uludağ National Park were comparable with other rural area data expect Ca^{2+} which was higher in our station with an average concentration of 1.61 \mug m^{-3}. Ion balance showed a deficiency of acid forming anions (SO^{2-}_4 and NO^-_3 for about 30% on the …
The Epoxidation Of Oil Obtained From The Eastern Black Sea Fishes, Eyüp Özcan, Bahri Ülküseven
The Epoxidation Of Oil Obtained From The Eastern Black Sea Fishes, Eyüp Özcan, Bahri Ülküseven
Turkish Journal of Chemistry
In this study we have investigated the suitable reaction conditions for the epoxidation of the semi-refined fish oil obtained from the fishes of eastern Black Sea, with peracetic acid. Various oxidation mixtures to reach the highest epoxyd-oxygene amount have been tested mean while the effective factors were established. In order to establish some specifications of the epoxy-product. Iodine-, hydroxyl-indices and epoxyd-oxygene percents were determined. We've also tried to explain how some reaction conditions (mole ratio of acetic acid to double bond and temperature) influenced the epoxy-product.
The Effect Of Metal Loading On The Adsorption Parameters Of Carbon Dioxide On Coprecipitated Nickel-Alumina Catalysts, A. Erhan Aksoylu, A. Nilgün Akin, S. Gönenç Sunol, Z. İlsen Önsan
The Effect Of Metal Loading On The Adsorption Parameters Of Carbon Dioxide On Coprecipitated Nickel-Alumina Catalysts, A. Erhan Aksoylu, A. Nilgün Akin, S. Gönenç Sunol, Z. İlsen Önsan
Turkish Journal of Chemistry
A coprecipitation method has been developed and modified for the preparation of nickel-alumina catalysts having metal loadings in the 0-25 wt\% Ni range. The effect of metal loading on CO_{2} adsorption was investigated under isothermal chromatographic conditions using an elution technique in the temperature range 483-533 K. Average enthalpies of adsorption were determined using the isosteres obtained from the experimental adsorption isotherms. The isotherms were also fitted to the Langmuir equation for the evaluation of adsorption equilibrium coefficients, Gibbs free energies, average adsorption enthalpies and entropies. Keywords: nickel-alumina, coprecipitated nickel-alumina, CO_{2} adsorption
Validity Of A Linear Estimator For The Total \Pi-Electron Energy Of Alternant Hydrocarbons, Lemi Türker
Validity Of A Linear Estimator For The Total \Pi-Electron Energy Of Alternant Hydrocarbons, Lemi Türker
Turkish Journal of Chemistry
The validity of a linear topological estimator formula which possesses a slope k such that 0
The Concept Of Molecular Similarity And The Angle Of Total \Pi-Electron Energy, Lemi Türker
The Concept Of Molecular Similarity And The Angle Of Total \Pi-Electron Energy, Lemi Türker
Turkish Journal of Chemistry
The concept of molecular similarity is developed and a novel similarity index based on the cosine of the angle of total \Pi-electron energy is proposed to interrelate structural variations to operant properties of molecules isoconjugate with alternant hydrocarbons.
Distribution Of Ce (Iv) Species In Hno_{3}-Hcio_{4} Media And Determination Of Stability Constants Of The Nitrato Complexes, Seval Bayülken, A. Sezai Saraç
Distribution Of Ce (Iv) Species In Hno_{3}-Hcio_{4} Media And Determination Of Stability Constants Of The Nitrato Complexes, Seval Bayülken, A. Sezai Saraç
Turkish Journal of Chemistry
In this paper, the distribution of cerium (IV) species depending on the charges of nitric acid-perchloric acid concentration at constant ionic strength (I=1.0) was investigated. Cerium (IV), being a strong oxidant, was utilized for investigating the oxidation kinetics of some amino acids. Knowing the distribution of cerium (IV) species is beneficial for better understanding this type of kinetics. Distribution of cerium (IV) species in aqueous media was studied by measuring the total optical absorbance of cerium (IV) species in different nitric acid-perchloric acid mixture solutions. The stability constants (K_{1} and K_{2}) of the nitrato cerium complexes were determined spectrophotometrically from …
Automation Of Dipole Moment Measurements Using Microprocessor Controlled System, Nil Tarim, Hakan Kuntman, Ayten Kuntman
Automation Of Dipole Moment Measurements Using Microprocessor Controlled System, Nil Tarim, Hakan Kuntman, Ayten Kuntman
Turkish Journal of Chemistry
A microprocessor controlled instrument that can be used in physical chemistry research laboratories has been designed and constructed. The intended use is the measurement of the dipole moment and determination of the temperature dependency of the dipole moment for polar substances, especially for macromolecules. Measurement techniques with conventional dipolmeters require fine adjustments and measurements which seem to be very tedious and time consuming. Provided automation enables very frequent measurements with a step of 1^{\circ}C and disallows any user-oriented error. The dielectric constant measurement is performed within an accuracy limit of less than \pm 0.001. Furthermore, the equipment designed provides the …
Polyelectrolytes In Immunology: Fundametals And Perspectives, Mehmet I. Mustafaev
Polyelectrolytes In Immunology: Fundametals And Perspectives, Mehmet I. Mustafaev
Turkish Journal of Chemistry
Physico-chemical criteria for the construction of artifical immunomodulators and immunogens(and vaccines) on the basis of synthetic polyelectrolyte(PE) and polyelectrolyte complexes(PEC) with low molecular weight ligands and protein (and polysaccharide) antigens are considered. The role of electric charge, chain length, conformation, hydrophobicity, polydispersity and supramolecular structure in the immunomodulating activity of PE(PEC) and the conditions facilitating the transformation of their suppressor capacity into immunostimulating one in the same polymerhomologues series are discussed. A structure-function relationship of immunogenicity of PE(PEC), a structural model of an artificial polymer- subunit immunogen and some practical applications of them as valuable tools in theoretical immunological studies …
The Determination Of Some Heavy Metal Cations By Tlc/Photodensitometry, Şahin Savaşçi, Mehmet Akçay
The Determination Of Some Heavy Metal Cations By Tlc/Photodensitometry, Şahin Savaşçi, Mehmet Akçay
Turkish Journal of Chemistry
The samples having complex matrices were analyzed for some heavy metal cations by using a thin layer chromatography/photodensitometry (TLC/PD) system. The rock samples were dissolved by suitable methods. Nickel, Cobalt and Copper were dedected and analyzed by photodensitometric comparison of corresponding spots of samples with those of standards. The results of the same samples and standards were compared with those obtained by atomic absorption measurements. Our results are comparable with the results of flame atomic absorption measurements. The precision of TLC method was calculated to be 9.4\% as relative standard deviations depending on 17 replicate measurements. The accuracy of TLC …
Synthesis Of Some Pyrazolo-Pyridazine Compounds, Adem Önal, Yunus Akçamur, Behzat Altural
Synthesis Of Some Pyrazolo-Pyridazine Compounds, Adem Önal, Yunus Akçamur, Behzat Altural
Turkish Journal of Chemistry
Addition of {\bf 1} to two moles of phenylhydrazine gives 1,2,4,6- tetraphenyl-(2,3-d)-pyrazolo-5,6-pyridazine-7-one {\bf 4} isomer compound 1, 2,3,5-tetraphenyl-(2,3-d) pyrazolo-5,6-pyridazine-7-one {\bf 5} of {\bf 4} was synthesized by the reaction of {\bf 2} with phenylhydrazine. 3,4- Diphenyl-(2,3-d)-pyrazolo-(1H,6H)-pyridazine-7-one {\bf 6} was also obtained in two different ways. Reaction of {\bf 1} and 4-benzoyl-5 phenyl- furan-2,3-dione {\bf 3} with hydrazinium hydrate furnished compound {\bf 6}. The structures of {\bf 4,5} and {\bf 6} were determined by the ^{13} C- NMR, IR spectra and elemental analysis. These new isomer and condensed compounds synthesized in this study are important for heterocyclic chemistry.
Cycloaddition Reactions Of Dichloroketene To Allyl Ethers, Hülya Şenöz, Süleyman Yildirir
Cycloaddition Reactions Of Dichloroketene To Allyl Ethers, Hülya Şenöz, Süleyman Yildirir
Turkish Journal of Chemistry
Allyl ethers reacted with dichloroketene by [2+2] Cycloaddition to produce 2,2-dichlorocyclobutanones structure of products were determined by IR, NMR, GC MS tecniques.
A Kinetic Study Of Homogeneous Bulk Polymerization Of Ethyl Methacrylate Initiated By Benzoyl Peroxide And An N, N^{\Prime} -Dimethylaniline Redox Pair, Serap Şenel, Belma Işik-Yürüksoy, Olgun Güven
A Kinetic Study Of Homogeneous Bulk Polymerization Of Ethyl Methacrylate Initiated By Benzoyl Peroxide And An N, N^{\Prime} -Dimethylaniline Redox Pair, Serap Şenel, Belma Işik-Yürüksoy, Olgun Güven
Turkish Journal of Chemistry
The homogenous bulk polymerization of ethyl methacrylate (EMA) was studied using benzoyl peroxide (BPO) and an N,N^{\prime}-dimethylaniline (DMA) redox pair with the dilatometric method. The half-order dependence of the polymerization rate upon both the BPO and DMA concentrations was obtained. The overall activation energy of the polymerization was found to be between 32.3-55.3 kJ/mole for different initial molar ratios of the redox pair. A retaring effect was observed at lower polymerization temperatures for low concentrations of BPO. The formation of reddish colored polymers at higher DMA concentrations was explained by the adsorption of adduct formed between DMA radicals.
Synthesis Of 2[1'(3',5'-Disubstituted Pyrazolyl) Methyl]5-Phenyl Amino-1,3,4-Thiadiazoles And 1,2,4-Triazoles As Potential Therapeutic Agents, Roshan Ahmad, M. Zia-Ul-Haq, Rukhsana Jabeen, Helmut Duddeck
Synthesis Of 2[1'(3',5'-Disubstituted Pyrazolyl) Methyl]5-Phenyl Amino-1,3,4-Thiadiazoles And 1,2,4-Triazoles As Potential Therapeutic Agents, Roshan Ahmad, M. Zia-Ul-Haq, Rukhsana Jabeen, Helmut Duddeck
Turkish Journal of Chemistry
A complete synthesis of 2[1'(3', 5'-disubstituted pyrazolyl) methyl] 5- phenyl-1,3,4-thiadiazole V(a-b) and 1,2,4-trizole VI (a-b) is reported. Cyclocondensation of \beta-diketones with etylhydrazino acetate hydrochloride yielded ethyl 3,5-disubstituted pyrazolyl acetate II(a-c) which on treatment with hydrazine hydrate resulted in the formation of their hydrazide derivatives III(a-c). These hydrazides, when treated with phenyl isothiocyanate, gave thiosemicarbazide derivatives IV(a-c), which were cyclised in the presence of con. H_{2}SO_{4} and NaOH to give V(a-b) and VI(a-b), respectively.
Extraction Of Dyestuff From Madder Plant ( Rubia Tinctorum L.) And Dyeing Of Wool, Feathered-Leather And Cotton}, Adem Önal
Turkish Journal of Chemistry
In this study, the total amount of dyeing substances present in {\it Rubia tinctorum L}. was found by using the extraction method and then separated in column. All of the dyeings were carried out with red component alizarin (1,2-dihydroxyanthraquinone). Dyeing conditions and other characteristics were determined and in most cases high fast colours were obtained.
Oxidative Coupling Of Methane On Lnba_{2}Cu_{3}O_{7-X} Superconductors, N. T. Shamilov, V. P. Vislovskii, E. A. Mamedov, S. M. Aliyev, A. I. Suleimanov, E. G. Ismailov
Oxidative Coupling Of Methane On Lnba_{2}Cu_{3}O_{7-X} Superconductors, N. T. Shamilov, V. P. Vislovskii, E. A. Mamedov, S. M. Aliyev, A. I. Suleimanov, E. G. Ismailov
Turkish Journal of Chemistry
The superconducting oxides LnBa_{2}Cu_{3}O_{7-x} (Ln=Y, Gd, Er, Yb, Lu) showed poor selectivity in the oxidative coupling of methane. The addition of 0.5 mol. %Li_{2}O to these materials considerably enhanced the yield of C_{2} hydrocarbons. This effect was related to both lower redox property and higher basicity of Li-doped catalysts as compared to those of undoped ones.
Deacidification Of High Acid Olive Oil By Immobilized Lipase, Ayşe Makasçi, Kadir Arisoy, Azmi Telefoncu
Deacidification Of High Acid Olive Oil By Immobilized Lipase, Ayşe Makasçi, Kadir Arisoy, Azmi Telefoncu
Turkish Journal of Chemistry
The acidity reduction of high acid oils prior to refining could be an attractive application for industry. In this study the enzymatic deacidification degummed and dewaxed olive oil with a high free fatty acid content, catalysed by an immobilized lipase was optimzed (Novozym 435). The optimum amount of substrate for synthesizing trigliycerides was the necessary stoichiometric amount of fatty acid and glycerol. The mixing was performed with a mechanical stirrer and the dehydration was performed by vacuum pump or by bubbling dry nitrogen. The dehydration rate was faster than the deacidification rate. The four parameters chosen for this experimental plan: …
A New Flavanone From Teucrium Alyssifolium, G. Topcu, C. Eris, S. Kurucu A. Ulubelen
A New Flavanone From Teucrium Alyssifolium, G. Topcu, C. Eris, S. Kurucu A. Ulubelen
Turkish Journal of Chemistry
From the aerial parts of {\it Teucrium alyssifolium} in addition to previously obtained {\it neo-}clerodane diterpenoids, a new flavanone alysifolinone and three flavones cirsiliol, cirsilineol and luteolin-6,7,3', 4'-tetramethyl ether, were isolated. The structure of the compounds was established by spectral data, and by TLC comparison for the known compounds. Keywords: Teucrium alyssifolium, Lamiaceae, flavanone, alysifolinone, flovones.
Synthesis Of Optically Active Camphorsulphonylbenzimidazoles, Mashooda Hasan, Humaira Masood, Naeema Khan, M. Zia-Ul-Haq
Synthesis Of Optically Active Camphorsulphonylbenzimidazoles, Mashooda Hasan, Humaira Masood, Naeema Khan, M. Zia-Ul-Haq
Turkish Journal of Chemistry
The preparation of optically active camphorsulphonylbenzimidazole {(\bf 1)}, a mixture of regioisomeric 5-nitro- {\bf (2A)} and 6-nitro-{\bf (2B)} camphorsulphonylbenzimidazoles, 5-nitro-{\bf (3A)} and 6-nitro-{\bf (3B)} 2- methyl camphorsulphonylbenzimidazoles is described. In this study the structure of the purified camphorsulphonylbenzimidazoles {\bf 1, 2B, 3A} and {\bf 3B} was confirmed by their mass and ^{1}H NMR spectral analysis. The specific rotation of each pure compound is also reported.
Investigation Of Adsorption Isotherms Used For Wool Dyeing By Aqueous Extraction Of Cehri Fruit (Fructus Rhamni Petiolari) And Dyeing Of Wool And Silk Accompanied By Various Mordants, A. Haluk Aydin, Fuat Güzel, Zeki Tez
Investigation Of Adsorption Isotherms Used For Wool Dyeing By Aqueous Extraction Of Cehri Fruit (Fructus Rhamni Petiolari) And Dyeing Of Wool And Silk Accompanied By Various Mordants, A. Haluk Aydin, Fuat Güzel, Zeki Tez
Turkish Journal of Chemistry
In this study, adsorption isotherms were obtained by processing wool with dyestuff solutions of different concentrations extracted from cehri fruit with water. These isotherms follow the Nernst equation; the Nernst constant was determined and interpreted. In addition, wool and silk fibres were dyed with the same dyestuff solution and various mordants. Colours having a high fastness which could be used on an industrial scale were produced.
Latex Supported Manganese(Iii) Porphyrin Catalysts For Oxidations Of Alkenes By Hydrogen Peroxide And {\It Tert-} Butyl Hydroperoxide In The Aqueous Medium, Hayrettin Türk
Turkish Journal of Chemistry
Cationic polymer latexes were prepared by emulsion copolymerization of vinylbenzyl chloride and divinylbenzene followed by quaternization with trimethylamine and used as catalyst supports for 5,10,15,20-tetrakis(2, 6-dichloro-3-sulfonatophenyl)porphinatomanganese(III) chloride and 5,10,15,20-tetra(4-sul- fonatophenyl)porphinatomanganese(III) chloride. The supported catalysts and water soluble analogues were used for oxidation of styrene, 1-decene and {\it cis}-cyclooctene by hydrogen peroxide and {\it tert}- butyl hydroperoxide in the aqueous phase. The oxidation of 1-decene and {\it cis}-cyclooctene failed. In the oxidation of styrene, the porphyrin catalysts in the latex were more active than in solution. The relative molar ratios of oxidant: styrene: Mn porphyrin were 1250: 750: 1, and about …
The Investigation Of Aluminum Sulfate-Potassium Chloride Solid Phase Reaction, İ. Ayhan Şengi̇l
The Investigation Of Aluminum Sulfate-Potassium Chloride Solid Phase Reaction, İ. Ayhan Şengi̇l
Turkish Journal of Chemistry
It was found that aluminum sulfate reacts with potassium chloride to produce K_{2}SO_{4}, Al_{2}O_{3}, and Cl_{2} in the solid phase at 700 ^{\circ}C. This reaction was investigated with thermal analysis under air and nitrogen atmosphere. By changing temperature and time parameters, the actual yield of conversion in question was examined analytically and the optimum temperature and time were found for the reaction. The rate expression of the solid phase reaction was also investigated and the rate equation was obtained.
Poly (D,L-Lactic Acid) Homopolymers: Synthesis And Characterization, Xu Kaitian, Ahmet Kozluca, Emir B. Denkbaş, Erhan Pi̇şki̇n
Poly (D,L-Lactic Acid) Homopolymers: Synthesis And Characterization, Xu Kaitian, Ahmet Kozluca, Emir B. Denkbaş, Erhan Pi̇şki̇n
Turkish Journal of Chemistry
In this study, poly(D,L-lactic acid or D,L-lactide) (PDLLA) homopolymers were synthesized with different molecular weights. Low molecular weight PDLLAs (MW_n: 500-2300) were synthesized by direct polycondensation of DL-lactic acid without using any catalyst, while high molecular weight PDLLAs ( MW_n: 8x10^3-150x10^3) were produced by ring-opening polymerization of DL-lactide with stannous chloride as catalyst (initiator). Average molecular weights of PDLLAs were determined by end-group analysis, by viscosimetric measurements and by HPLC. PDLLA homopolymers were characterized by FTIR, NMR and DSC. In the production of PDLLAs by direct polymerization, molecular weights of the PDLLAs increased with the increase in the polymerization time …