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2010

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Articles 6541 - 6570 of 6945

Full-Text Articles in Physical Sciences and Mathematics

Acceleration Of Suprathermal Particles By Compressional Plasma Wave Trains In The Solar Wind, Ming Zhang Jan 2010

Acceleration Of Suprathermal Particles By Compressional Plasma Wave Trains In The Solar Wind, Ming Zhang

Aerospace, Physics, and Space Science Faculty Publications

This paper presents a calculation of particle acceleration by an idealized compressional plasma wave train. In this model, suprathermal particles, such as pickup ions, are continuously injected into a wave train consisting of a series of compression or rarefaction regions. The momentum distribution of particles will become broader and broader as they go through the wave train, which is very similar to diffusion in momentum space. The acceleration process is very fast: it does not take too many wave cycles even with a small compression amplitude to reach an asymptotic steady state momentum distribution. In the absence of large-scale adiabatic …

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Diffusion Of Relativistic Runaway Electrons And Implications For Lightning Initiation, Joseph R. Dwyer Jan 2010

Diffusion Of Relativistic Runaway Electrons And Implications For Lightning Initiation, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

Using detailed Monte Carlo simulations, the diffusion coefficients for relativistic runaway electron avalanches in air are found for the range of electric field strengths applicable to thunderclouds. Diffusion causes runaway electron avalanches to spread perpendicular to and parallel to the avalanche direction, resulting in much smaller peak conductivities than would be inferred otherwise. The idea that runaway electron avalanches seeded by extensive cosmic ray air showers may initiate lightning has gained considerable popularity in recent years. However, using the diffusion coefficients calculated in this paper along with the avalanche multiplication limit from X-ray and positron feedback, it is found that …

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First Results On Terrestrial Gamma Ray Flashes From The Fermi Gamma-Ray Burst Monitor, Michael S. Briggs, Joseph R. Dwyer Jan 2010

First Results On Terrestrial Gamma Ray Flashes From The Fermi Gamma-Ray Burst Monitor, Michael S. Briggs, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

The Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope detected 12 intense terrestrial gamma ray flashes (TGFs) during its first year of observation. Typical maximum energies for most of the TGFs are ∼30 MeV, with one TGF having a 38 MeV photon; two of the TGFs are softer and longer than the others. After correcting for instrumental effects, a representative bright TGF is found to have a fluence of ∼0.7 photons cm-2. Pulses are either symmetrical or have faster risetimes than fall times; they are well fit with Gaussian or lognormal functions. The fastest risetime observed was 7 …

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Thunderstorm Characteristics Associated With Rhessi Identified Terrestrial Gamma Ray Flashes, Michael E. Splitt, Steven M. Lazarus, Diana H. Barnes, Joseph R. Dwyer, Hamid K. Rassoul, David M. Smith, Bryna J. Hazelton, Brian W. Grefenstette Jan 2010

Thunderstorm Characteristics Associated With Rhessi Identified Terrestrial Gamma Ray Flashes, Michael E. Splitt, Steven M. Lazarus, Diana H. Barnes, Joseph R. Dwyer, Hamid K. Rassoul, David M. Smith, Bryna J. Hazelton, Brian W. Grefenstette

Aerospace, Physics, and Space Science Faculty Publications

The characteristics of thunderstorms that produce terrestrial gamma-ray flashes (TGFs) observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) are determined using climatological and meteorological data. RHESSI observed TGFs follow diurnal, seasonal, and geographic patterns that are very similar to those of thunderstorms confirming, in part, that these events are directly connected to thunderstorm activity. The TGF producing thunderstorms are shown to be closely associated with tall (ranging from 13.6 km to 17.3 km) tropical thunderstorm systems, a finding that is consistent with theoretical expectations from models of relativistic breakdown that relate the source region to the spectral …

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Magnetic Cloud Boundary Layer Of 9 November 2004 And Its Associated Space Weather Effects, Pingbing Zuo, Fengsi Wei, Xueshang Feng, Xiaojun Xu, Wenbin Song Jan 2010

Magnetic Cloud Boundary Layer Of 9 November 2004 And Its Associated Space Weather Effects, Pingbing Zuo, Fengsi Wei, Xueshang Feng, Xiaojun Xu, Wenbin Song

Aerospace, Physics, and Space Science Faculty Publications

On 9 November 2004, the WIND spacecraft detected a magnetic cloud boundary layer (MCBL) during the interval from 19:07 UT to 20:30 UT. Within the MCBL, there is intense southward magnetic field and the dynamic pressure is rather high, which makes it much geoeffective. Twenty-three minutes later, the MCBL arrived on the magnetopause. An intense geomagnetic storm main phase was driven by the sustaining strong southward magnetic field within the MCBL. During the passage of the MCBL, a typical magnetospheric substorm was triggered. The substorm onset was synthetically identified by the aurora breakup, magnetic dipolarization, dispersionless particle injection, Pi2 pulsation, …

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Isolation And Identification Of A New Acetildenafil Analogue Used To Adulterate A Dietary Supplement: Dimethylacetildenafil, Ali̇ Hakan Göker, Maksut Coşkun, Mehmet Alp Jan 2010

Isolation And Identification Of A New Acetildenafil Analogue Used To Adulterate A Dietary Supplement: Dimethylacetildenafil, Ali̇ Hakan Göker, Maksut Coşkun, Mehmet Alp

Turkish Journal of Chemistry

A new sildenafil analogue was found to have been added illegally to a dietary supplement marketed for the enhancement of sexual function. The structure was determined as 5-(2-ethoxy-5- {[4-(3,5-dimethyl)piperazin-1-yl]-acetyl}phenyl)-1,6-dihydro-1-methyl-3- propyl-7H-pyrazolo [4,3-d]pyrimidin-7-one. Owing to the inclusion of a dimethyl group in acetildenafil, the detected compound was called dimethylacetildenafil. The sample was purified with column chromatography. The IR, LC/MS (ESI), and completely assigned NMR data of dimethylacetildenafil are reported for the first time. The structure was compared with that of acetildenafil and the results showed that the ethyl substitution at the 4-position of the piperazine ring had been replaced by a 3,5-dimethyl …

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Synthesis Of Some New Biheterocyclic Triazole Derivatives And Evaluation Of Their Antimicrobial Activity, Hakan Bektaş, Ahmet Demi̇rbaş, Nesli̇han Demi̇rbaş, Şengül Alpay Karaoğlu Jan 2010

Synthesis Of Some New Biheterocyclic Triazole Derivatives And Evaluation Of Their Antimicrobial Activity, Hakan Bektaş, Ahmet Demi̇rbaş, Nesli̇han Demi̇rbaş, Şengül Alpay Karaoğlu

Turkish Journal of Chemistry

2-{3-(4-Substitutedbenzyl)-4-[2-(1H-indol-3-yl)ethyl]-5-oxo-4,5- dihydro-1H-1,2,4-triazol-1-yl}-N'-(aryl-methylene)acetohydrazides (5a-g), 4-amino-2-{-(4-substitutedbenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol- 1-yl}-N'-(arylmethylene)acetohydrazides (6a,b), and 4-[2-(1H-indol- 3-yl)ethyl]-5-(4-substitutedbenzyl)-2-{5-(phenylamino)-1,3,4-thiadiazol- 2-yl]methyl}-2,4-dihydro-3H-1,2,4-triazol-3-ones (8a,b) were synthesized starting from 4-alkyl-5-(4-substitutedbenzyl)-2,4-dihydro- 3H-1,2,4-triazol-3-ones (2a-c) by several steps and their structures were well characterized by elemental analyses, IR, ^1H-NMR, ^{13}C-NMR, and mass spectral studies. They were also screened for their microbial activities. The obtained antimicrobial activity results revealed that 12 among the 24 compounds tested displayed variable growth inhibition effects on the tested gram-positive and gram-negative bacterial strains. None of the compounds showed antifungal activity against yeast-like fungi.

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Highly Stereoselective And Efficient Synthesis Of The Dopa Analogue In Pepticinnamin E Via Enantioselective Hydrogenation Of Dehydroamino Acids, Dequn Sun Jan 2010

Highly Stereoselective And Efficient Synthesis Of The Dopa Analogue In Pepticinnamin E Via Enantioselective Hydrogenation Of Dehydroamino Acids, Dequn Sun

Turkish Journal of Chemistry

An efficient and new method was developed to prepare the dopa analogue 11 in natural pepticinnamin via catalytic hydrogenation of dehydroamino acids (DDAA) with a good yield and ee. Product 11 is a key intermediate towards the total synthesis of pepticinnamin E and its analogues.

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Performance Evaluation Of Platinum-Based Catalysts For The Development Of Proton Exchange Membrane Fuel Cells, Abdul Sattar Ali Khan, Riaz Ahmed, Muhammad Latif Mirza Jan 2010

Performance Evaluation Of Platinum-Based Catalysts For The Development Of Proton Exchange Membrane Fuel Cells, Abdul Sattar Ali Khan, Riaz Ahmed, Muhammad Latif Mirza

Turkish Journal of Chemistry

Platinum-based catalysts are considered the most efficient catalysts for triggering electrochemical reactions in proton exchange membrane (PEM) fuel cells. In the present study, commercial catalysts containing 10% and 30% Pt supported on Vulcan XC-72 carbon were studied to assess their performance in PEM fuel cells. Both catalysts consisted of Pt particles of almost the same size. The utility of these catalysts in PEM fuel cells was studied by finding the real surface area and rate of electro-oxidation of methanol in 0.5 M H_2SO_4 by using cyclic voltammetry. The methanol oxidation reaction was used for characterization of catalysts of PEM fuel …

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Chelating Agent Free Solid Phase Extraction (Caf-Spe) Method For Separation And/Or Preconcentration Of Iron(Iii) Ions, Özcan Yalçinkaya, Orhan Murat Kalfa, Ali̇ Rehber Türker Jan 2010

Chelating Agent Free Solid Phase Extraction (Caf-Spe) Method For Separation And/Or Preconcentration Of Iron(Iii) Ions, Özcan Yalçinkaya, Orhan Murat Kalfa, Ali̇ Rehber Türker

Turkish Journal of Chemistry

This paper presents a chelating agent free solid phase extraction (CAF-SPE) method for the separation and/or preconcentration of trace iron(III) ions. This method is based on the sorption of Fe(III) ions without using any chelating agent onto Amberlyst 36 resin. A good relative standard deviation (3%), high recovery (>95%), high enrichment factor (100), and low detection limit (0.32 \mu g L^{-1}) were obtained. The adsorption capacity of resin was 117 mg g^{-1} for iron(III). The method was applied for the determination of iron various in water and commercial tea bag samples. The accuracy of the method was confirmed by …

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Synthesis And Antimicrobial Activity Of N-Alkyl Substituted P-Methyl (E)-3- And 4-Azachalconium Bromides, Nuretti̇n Yayli, Gülbi̇n Misir, Nuran Yayli, Ahmet Yaşar, Emi̇ne Demi̇r, Zi̇hni̇ Demi̇rbağ Jan 2010

Synthesis And Antimicrobial Activity Of N-Alkyl Substituted P-Methyl (E)-3- And 4-Azachalconium Bromides, Nuretti̇n Yayli, Gülbi̇n Misir, Nuran Yayli, Ahmet Yaşar, Emi̇ne Demi̇r, Zi̇hni̇ Demi̇rbağ

Turkish Journal of Chemistry

Twenty new N-alkyl substituted p-methyl (E)-3- and 4-azachalcones (1a-j, 2a-j){3-[(1E)-3-(4-methylp-henyl)-3- oxoprop-1-en-1-yl]-1-alkyl (C_{5-12,_{14-15) pyridinium bromides (1a-j) and 4-[(1E)-3-(4-methylp-henyl)-3-oxoprop-1-en-1-yl]-1-alkyl (C_{5-12,_{14-15) pyridinium bromides (2a-j)} were synthesized and tested for antimicrobial activities against Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Enterococcus faecalis, Proteus vulgaris, and Escherichia coli. They showed good antimicrobial activity especially against the gram-positive bacteria tested with minimal inhibitory concentration (MIC) values less than 4.7 \mu g/mL in most cases. The optimum length of the alkyl chain for better and broader activity is situated in the range of 8-12 carbon atoms in the series of compounds 1a-j, 2a-j. The non-alkylated compounds 1-2 were …

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Electrooxidation Of Hydrazine By Carminic Acid As A Mediator On A Glassy Carbon Electrode, Mohammad Mazloum Ardakani, Seyed Hossein Moosavizadeh, Ali Sadeghiane, Mohammad Hossein Mashhadzadeh, Mohammad Ali Karimi Jan 2010

Electrooxidation Of Hydrazine By Carminic Acid As A Mediator On A Glassy Carbon Electrode, Mohammad Mazloum Ardakani, Seyed Hossein Moosavizadeh, Ali Sadeghiane, Mohammad Hossein Mashhadzadeh, Mohammad Ali Karimi

Turkish Journal of Chemistry

Electrocatalytic oxidation of hydrazine on a glassy carbon electrode with carminic acid as a homogeneous mediator in 0.1 M phosphate buffer solution (pH 8.0) was studied. Cyclic voltammetry study showed that the catalytic current of the system depends on the concentration of hydrazine. The magnitude of the peak current obtained by linear sweep voltammetry for carminic acid increased sharply in the presence of hydrazine and proportional to the hydrazine concentration in the ranges of 5.0-800.0 \mu M and the detection limit was 3.0 \mu M by this technique. The detection limit was promoted by differential pulse voltammetry and decreased to …

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Synthesis, Structural Determination, And Biological Activity Of New 7-Hydroxy-3-Pyrazolyl-4h-Chromen- 4-Ones And Their O-\Beta-D-Glucosides, Kishor Hatzade, Vijay Taile, Pravin Gaidhane, Vishwas Ingle Jan 2010

Synthesis, Structural Determination, And Biological Activity Of New 7-Hydroxy-3-Pyrazolyl-4h-Chromen- 4-Ones And Their O-\Beta-D-Glucosides, Kishor Hatzade, Vijay Taile, Pravin Gaidhane, Vishwas Ingle

Turkish Journal of Chemistry

A convenient route to synthesize some new medicinally important 7-hydroxy-3-pyrazolyl chromones (3a-i) is described. The interaction of 7-hydroxy-3-formyl chromone (1) with various substituted acetophenones and further cyclization with hydrazine hydrate in an aprotic solvent followed by condensation with 2, 3, 4, 6-tetra-o-acetyl-\alpha-dglucopyranosyl bromide afforded 2, 3, 4, 6-tetra-o-acetyl-\beta-d-glucopyranosyloxy-3-(3-aryl-1H-pyrazol-5- yl)-4H-chromen-4-ones (4a-i). Later deacetylation with anhydrous zinc acetate in methanol gave 7-o-\beta-d-glucopyranosyloxy-3-(3-aryl- 1H-pyrazol-5-yl)-4H-chromen-4-ones (5a-i). These compounds were evaluated for their in vitro antimicrobial and anti-oxidant activity. The structures of these newly synthesized o-glucosides were established by IR, NMR, mass spectra, elemental analysis, and chemical analysis.

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Synthesis And Characterization Of Non-Symmetric Tetradentate Complexes Of Zn(Ii), Co(Ii), And Cu(Ii), Maryam Lashanizadegan, Shima Seraj Jan 2010

Synthesis And Characterization Of Non-Symmetric Tetradentate Complexes Of Zn(Ii), Co(Ii), And Cu(Ii), Maryam Lashanizadegan, Shima Seraj

Turkish Journal of Chemistry

The non-symmetrical tetradentate Schiff-base H_2L was obtained using the half-unit N-(1-hydroxy-2-acetophenone)-1-amino- 2-phenyleneimine (HL) with 2-hydroxyl-1-naphthaldehyde. ZnL, CoL, and CuL complexes were prepared and characterized by ^1H-NMR, IR, electronic, and atomic absorption spectra. The single crystal X-ray structure of CuL was determined. Crystal data for CuL are triclinic space group P-1, a = 8.3933 (17) Å, b = 11.197 (2) Å, c = 13.381 (3) Å, \alpha = 95.29 (3)°, \beta = 94.37 (3)°, \gamma = 95.82 (3)°, and z = 2.

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Stabilizing Cyclacene Molecules, Muthana Shanshal Jan 2010

Stabilizing Cyclacene Molecules, Muthana Shanshal

Turkish Journal of Chemistry

It is shown that introducing a single methylene group into each trannulene ring of a cyclacene molecule compels the formation of a non-bonded molecular orbital, NBMO, in the ring. The union of both trannulenes conforms to a first order perturbation change in the total energy according to Dewar's PMO theory. The NBMO coefficients can be calculated then according to Coulson's pairing theorem. The PMO calculated new HOMO-LUMO energies of the cyclacene indicate the relative stabilization of the singlet over the triplet state of the cyclacene. The results are confirmed by the DFT calculation of differently substituted bis, methylene cyclacenes. The …

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Isolation Of Bis(1,4-Diphenyl-1,4-Bis(2-Pyridyl)-2,3-Diaza-1,3-Butadiene) Disilver With Bridging (N-N) Dinucleating Subunits: Formation Of A 6-Membered Chelate Ring, Amitabha Datta, Neerish Revaprasadu Jan 2010

Isolation Of Bis(1,4-Diphenyl-1,4-Bis(2-Pyridyl)-2,3-Diaza-1,3-Butadiene) Disilver With Bridging (N-N) Dinucleating Subunits: Formation Of A 6-Membered Chelate Ring, Amitabha Datta, Neerish Revaprasadu

Turkish Journal of Chemistry

A novel Ag(I) dinuclear complex {[(C_6H_5)(C_5H_4N)-C=N-N=C- (C_5H_4N)(C_6H_5)]Ag}_2.ClO_4(ClO_4) (1/2CH_3CN) (1) that was derived under mild conditions, during the course of combination of AgClO_4 with a polymorphic azine ligand, 1,4-diphenyl-1,4-bis(2-pyridyl)-2,3- diaza-1,3-butadiene (L) (condensed product of phenyl 2-pyridyl ketone and hydrazine monohydrate) is reported. The aforementioned complex is based on a central rotationally flexible diazine subunit (N-N). The azine ligand, L, having the N_2 dinucleating fragment, provides a coordination focus for pairs of metal centres and ultimately leads to the formation of a 6-membered chelate ring in 1.

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An Investigation Of Energy Transfer Between Coumarin 35 And Xanthene Derivatives In Liquid Medium, Mahmut Toprak, Mustafa Arik Jan 2010

An Investigation Of Energy Transfer Between Coumarin 35 And Xanthene Derivatives In Liquid Medium, Mahmut Toprak, Mustafa Arik

Turkish Journal of Chemistry

The energy transfer between coumarin 35 (C35) and pyronin compounds, which are xanthene derivatives, i.e. pyronin B (PyB) and pyronin Y (PyY), in methanol was investigated at room temperature by using steady-state absorption, emission, and time-resolved fluorescence spectroscopy. Fluorescence energy transfer rate constants (k_T) and critical radius (R_0) were determined for C35-PyB and C35-PyY molecular pairs in methanol. The obtained values of k_T and R_0 indicated that the dipole-dipole interaction between C35-PyB and C35-PyY molecular pairs accounted for the energy transfer mechanism. The energy transfer efficiency and the distance between the donor and acceptor (r) were also calculated for donor-acceptor …

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Simultaneous Determination Of Cu(Ii) And Pd(Ii) As 4-Phenylpiperazinecarbodithioate Complex Using H-Point Standard Addition Method And Derivative Spectrophotometry, Varinder Kaur, Ashok Kumar Malik, Neelam Verma Jan 2010

Simultaneous Determination Of Cu(Ii) And Pd(Ii) As 4-Phenylpiperazinecarbodithioate Complex Using H-Point Standard Addition Method And Derivative Spectrophotometry, Varinder Kaur, Ashok Kumar Malik, Neelam Verma

Turkish Journal of Chemistry

A new, simple, inexpensive, and sensitive method for the simultaneous spectrophotometric determination of Cu(II) and Pd(II) by H-point standard addition method and derivative spectrophotometry is described. 4- Phenylpiperazinecarbodithioate (PPDTC) in an anionic micellar solution of SLS was used as a reagent at pH 4. The experimental parameters, such as pH, type of surfactant, concentration of reagent, and surfactant used, were optimized to minimize the errors. The linear ranges of the method were 0.1-10 and 0.1-11 \mu g mL^{-1} for Cu(II) and Pd(II), respectively. The results of applying H-point standard addition and fourth derivative spectrophotometry showed that Cu(II) and Pd(II) can …

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Direct Reductive Amination Of Carbonyl Compounds Using Sodium Borohydride-Silica Chloride, Heshmatollah Alinezhad, Mahmood Tajbakhsh, Neda Hamidi Jan 2010

Direct Reductive Amination Of Carbonyl Compounds Using Sodium Borohydride-Silica Chloride, Heshmatollah Alinezhad, Mahmood Tajbakhsh, Neda Hamidi

Turkish Journal of Chemistry

A simple and convenient procedure for reductive amination of aldehydes and ketones using sodium borohydride in the presence of silica chloride as an active, inexpensive, recoverable, and recyclable catalyst is described. The reactions were carried out with equimolar amounts of amine and carbonyl compound using silica chloride-sodium borohydride in THF at room temperature.

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Composition Of The Essential Oils Of Pinus Nigra Arnold From Turkey, Ekrem Sezi̇k, Osman Üstün, Bülent Demi̇rci̇, Kemal Hüsnü Can Başer Jan 2010

Composition Of The Essential Oils Of Pinus Nigra Arnold From Turkey, Ekrem Sezi̇k, Osman Üstün, Bülent Demi̇rci̇, Kemal Hüsnü Can Başer

Turkish Journal of Chemistry

Essential oil composition of the needles of Pinus nigra Arnold collected from different localities in Turkey was investigated by GC and GC/MS. The main components in the oils were \alpha-pinene, \beta-pinene, \beta-caryophyllene, and germacrene D.

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Picolyl Substituted N-Heterocyclic Carbene/Palladium Catalyzed Heck Reactions, Murat Yi̇ği̇t, Beyhan Yi̇ği̇t, İsmai̇l Özdemi̇r, Engi̇n Çeti̇nkaya Jan 2010

Picolyl Substituted N-Heterocyclic Carbene/Palladium Catalyzed Heck Reactions, Murat Yi̇ği̇t, Beyhan Yi̇ği̇t, İsmai̇l Özdemi̇r, Engi̇n Çeti̇nkaya

Turkish Journal of Chemistry

Novel 1,3-dialkylimidazolinium and 1,3- dialkyltetrahydropyrimidinium hexafluorophosphate salts as N-heterocyclic carbene precursors were prepared by reacting N,N'-dialkylethandiamine or N,N'-dialkylpropandiamine, triethyl orthoformate, and ammonium hexafluorophosphate. The salts were characterized spectroscopically and tested in homogeneous Heck reactions.

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Synthesis, Characterization, Crystal Structures, And Antibacterial Activity Of Some New 1-(3,4,5-Trimethoxybenzoyl)-3-Aryl Thioureasreas, Aamer Saeed, Rasheed Ahmad Khera, Naeem Abbas, Muhammad Latif, Imran Sajid, Ulrich Flörke Jan 2010

Synthesis, Characterization, Crystal Structures, And Antibacterial Activity Of Some New 1-(3,4,5-Trimethoxybenzoyl)-3-Aryl Thioureasreas, Aamer Saeed, Rasheed Ahmad Khera, Naeem Abbas, Muhammad Latif, Imran Sajid, Ulrich Flörke

Turkish Journal of Chemistry

Synthesis of some novel 1-(3,4,5-trimethoxy)benzoyl-3- arylthiourea derivatives (1a-o) was accomplished in 2 steps. The synthetic route involves the reaction of 1-(3,4,5-trimethoxy)benzoyl chloride with potassium thiocyanate in 1:1 molar ratio in acetone to afford the corresponding isothiocyante followed by treatment with suitably substituted anilines. The structures of the products were established by elemental analyses, IR, ^1H- and ^{13}C-NMR, and mass spectroscopy and for 1b and 1m from single crystal X-ray diffraction data. All of the synthesized compounds (1a-o) were screened for antibacterial activity against gram positive and gram negative bacterial strains and were found to exhibit low activity towards the tested …

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Synthesis And Antimicrobial Activities Of 2-(5-Mercapto)-1,3-Oxadiazol-2-Ylmethyl-1,2,4-Triazol-3-One Derivatives, Nesli̇han Demi̇rbaş, Ahmet Demi̇rbaş, Hakan Bektaş, Şengül Alpay Karaoğlu, Deni̇z Şahi̇n Jan 2010

Synthesis And Antimicrobial Activities Of 2-(5-Mercapto)-1,3-Oxadiazol-2-Ylmethyl-1,2,4-Triazol-3-One Derivatives, Nesli̇han Demi̇rbaş, Ahmet Demi̇rbaş, Hakan Bektaş, Şengül Alpay Karaoğlu, Deni̇z Şahi̇n

Turkish Journal of Chemistry

The synthesis of 4-amino-2-[(5-mercapto-1,3,4-oxadiazol-2- yl)methyl]-5-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazol-3-one (2) and 4-amino-2-[(4-amino-5-mercapto-4H-1,2,4-triazol-3-yl)methyl]- 5-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazol-3-one (5) was performed starting from 2-[4-amino-3-(4-methylphenyl)-5-oxo-4,5- dihydro-1H-1,2,4-triazol-1-yl]acetohydrazide (1). The treatment of 2 and 5 with 4-fluorobenzaldehyde (for 8) or salicylaldehyde (for 6) afforded the corresponding Schiff bases (6 and 8). The condensation of 5 with phenacyl bromide produced 4-amino-5-(4-methylphenyl)-2- [(6-phenyl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-3-yl)methyl]- 2,4-dihydro-3H-1,2,4-triazol-3-one (7). The alkylation of 2 and 8 was carried out by using methyl iodide in basic media. Compounds 3 and 10a,b were prepared by aminoalkylation of 2 and 8 with 4-fluorophenyl piperazine, morpholine, or 4-methyl piperazine in the presence of formaldehyde. The synthesized compounds were screened for their antimicrobial activities …

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Convenient Synthesis Of Monomeric Steroids From Steroidal Oxalate Dimers Using Flash Vacuum Pyrolysis (Fvp), Lutfun Nahar, Alan Turner, Satyajit Sarker Jan 2010

Convenient Synthesis Of Monomeric Steroids From Steroidal Oxalate Dimers Using Flash Vacuum Pyrolysis (Fvp), Lutfun Nahar, Alan Turner, Satyajit Sarker

Turkish Journal of Chemistry

Flash vacuum pyrolysis (FVP) or thermolysis (FVT), an environmentally friendly method for studying organic reaction mechanisms as well as synthesis, was applied to a series of oxalate dimers (1, 3, 5, 7, 9, 11, 13, and 15) to synthesise monomeric enes, dienes, and a triene (2, 4, 6, 8, 10, 12, 14, and 16). All steroidal monomers were identified by spectroscopic means.

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An Efficient Synthesis Of Schiff Bases Containing Benzimidazole Moiety Catalyzed By Transition Metal Nitrates, Akbar Mobinikhaledi, Naser Foroughifar, Mehdi Kalhor Jan 2010

An Efficient Synthesis Of Schiff Bases Containing Benzimidazole Moiety Catalyzed By Transition Metal Nitrates, Akbar Mobinikhaledi, Naser Foroughifar, Mehdi Kalhor

Turkish Journal of Chemistry

A simple and efficient method has been developed for the synthesis of some novel Schiff bases via the reaction of aromatic aldehydes with 2-aminobenzimidazole by using catalytic amount of M(NO_3)_2.xH_2O in an organic solvent at room temperature. Some advantages of this protocol are its very good yields, use of available catalysts, simple workup procedure, and short reaction times.

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Asymmetric Synthesis Of 8-O-4'-Neolignan Perseal B, Yamu Xia, Wei Wang, Yinglan Guo, Junfeng Li Jan 2010

Asymmetric Synthesis Of 8-O-4'-Neolignan Perseal B, Yamu Xia, Wei Wang, Yinglan Guo, Junfeng Li

Turkish Journal of Chemistry

Full details of an enantioselective total synthesis of 8-O-4'-neolignan perseal B are presented for the first time. The synthesis was achieved in 8 steps from vanillin and involved the asymmetric dihydroxylation reaction using AD-mix-\alpha to give the key intermedium (1S,2S)-1-(4-(benzyloxy)-3-methoxyphenyl)propane-1,2,3- triol, and the Mitsunobu reaction between phenylpropanoid and vanillin formed perseal B. The synthetic method of perseal B exhibits a new route for 8-O-4'-neolignan.

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Comparative Kinetic Studies On The Alkaline Hydrolysis Of Halogen Substituted Isocoumarins, Hafiz Badaruddin Ahmad, Muhammad Aslam Malana, Muhammad Yousaf, Muhammad Rehan, Mazhar Abbas Jan 2010

Comparative Kinetic Studies On The Alkaline Hydrolysis Of Halogen Substituted Isocoumarins, Hafiz Badaruddin Ahmad, Muhammad Aslam Malana, Muhammad Yousaf, Muhammad Rehan, Mazhar Abbas

Turkish Journal of Chemistry

Kinetics of the hydrolysis of 3-(2'-chloro-6'-fluorobenzyl) isocoumarin (1), 3-(4'-fluorophenyl)isocoumarin (3), 3-(2'- fluorophenyl)isocoumarin (5), 3-(2'-chlorophenyl)isocoumarin (7), and 3-(4'-chlorophenyl)isocoumarin (9) were studied spectrophotometrically in the presence of aqueous solution of potassium hydroxide. The rates of hydrolyses for these isocoumarins were compared. The data for isocoumarin (1) were further investigated to probe the reaction mechanism. The dependence of pseudo-first order rate constant k_{obs} on hydroxide ion concentration is fitted by the expression k_{obs} = k_o + k_1[OH] + k_2 [OH]^2, showing the formation of monoanionic and dianionic tetrahedral intermediates during the course of reaction. The magnitude of k_o shows significant participation of solvent …

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Synthesis, Characterisation, And Structural Elucidation By Spectral Investigation (Ft-Ir, Multinuclear Nmr, Mass Spectrometry) Of Biologically Active Organotin(Iv) Compounds Containing Germanium, Muhammad Kaleem Khosa, Muhammad Mazhar, Saqib Ali, Sarim Dastgir Jan 2010

Synthesis, Characterisation, And Structural Elucidation By Spectral Investigation (Ft-Ir, Multinuclear Nmr, Mass Spectrometry) Of Biologically Active Organotin(Iv) Compounds Containing Germanium, Muhammad Kaleem Khosa, Muhammad Mazhar, Saqib Ali, Sarim Dastgir

Turkish Journal of Chemistry

A new series of di and tri-organotin(IV) compounds containing germanium with the general formula R_{4-n}SnL_n was synthesised by reaction of 3-triphenylgermanyl-3,3-dimethylpropionic acid with organotin(IV) oxides and organotin(IV) chloride in 2:1 and 1:1 molar ratio, respectively, where R~=~CH_3, C_2H_5, n-C_4H_9, n-C_8H_{17}, and C_6H_5 n = 1 or 2 and L~=~triphenylgermanyl acid anion (GeC_{23} H_{23} O_2^-). These compounds were characterised by elemental analyses, FT-IR, multinuclear NMR (^1H, ^{13}C, ^{119}Sn), and mass spectrometry. The geometry around the tin atom was determined and compared in both solution and solid states. The spectroscopic results indicated that all the diorganotin(IV) compounds containing germanium possess trigonal-bipyramidal structures …

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A Theoretical Study Of The Effects Of Polar Substitution On The Activation Barriers For Internal Rotation Around The C-N Bond In P-Substituted Nitrosobenzenes: Comparison Of Dft And Mp2 Calculations, Şafak Özhan Kocakaya, Necmetti̇n Pi̇ri̇nççi̇oğlu Jan 2010

A Theoretical Study Of The Effects Of Polar Substitution On The Activation Barriers For Internal Rotation Around The C-N Bond In P-Substituted Nitrosobenzenes: Comparison Of Dft And Mp2 Calculations, Şafak Özhan Kocakaya, Necmetti̇n Pi̇ri̇nççi̇oğlu

Turkish Journal of Chemistry

The activation barriers for internal rotation around the C-N bond in p-substituted nitrosobenzenes were calculated using the density functional theory (DFT) and second-order Møller-Plesset (MP2) methods with the 6-31+g(d) basis set. The polarisable continuum model (PCM) was used to model the solvent effect. An explicit water molecule was also introduced to form a hydrogen bond with the nitrosogroup and its effect on the barrier was studied by DFT. The barriers were well-correlated with Hammett sigma^+ rather than sigma values, meaning a strong resonance effect. The MP2 method produces better and comparable results with the few available experimental values.

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An Efficient One-Pot Synthesis Of Dihydropyrimidinones Catalyzed By Zirconium Hydrogen Phosphate Under Solvent-Free Conditions, Mustafa Küçüki̇slamoğlu, Şenol Beşoluk, Mustafa Zengi̇n, Mustafa Arslan, Mehmet Nebi̇oğlu Jan 2010

An Efficient One-Pot Synthesis Of Dihydropyrimidinones Catalyzed By Zirconium Hydrogen Phosphate Under Solvent-Free Conditions, Mustafa Küçüki̇slamoğlu, Şenol Beşoluk, Mustafa Zengi̇n, Mustafa Arslan, Mehmet Nebi̇oğlu

Turkish Journal of Chemistry

A simple, efficient, and practical procedure for the Biginelli reaction using zirconium hydrogen phosphate [Zr(H_2PO_4)_2] as a novel solid acid catalyst is described under solvent-free conditions in high yields. The catalyst exhibited remarkable reactivity and it is reusable.

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