Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
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Article Citation - WoS: 6Citation - Scopus: 6Palladium-Catalyzed Coupling of 2-En Carbonates With Terminal Alkynes(Elsevier Ltd., 2018) Taç, Doğan; Artok, LeventThe first palladium-catalysed coupling of the carbonates of (E)-configured conjugated enynols with terminal alkynes is described. This method allows the synthesis of vinyl-allenynes with good yields. It has been determined that the method is not suitable for the (Z)-configured substrates.Article Citation - WoS: 4Citation - Scopus: 6The Effect of Additives on Hydrodesulfurization of Dibenzothiophene Over Bulk Molybdenum Sulfide: Increased Catalytic Activity in the Presence of Phenol(Elsevier Ltd., 2008) Gül, Ömer; Atanur, Osman M.; Artok, Levent; Erbatur, OktayThe effect of various additive organic reagents on the activation of MoS3 as molybdenum sulfide catalyst precursor during hydrodesulfurization reaction of dibenzothiophene was studied. It was found that the presence of phenol or 1-naphthol greatly promoted the activity of the catalyst, while tetralin, 9,10-dihydrophenanthrene, ethylbenzene, and pyridine reagents were found to be detrimental for the activity of the catalyst.Article Citation - WoS: 27Citation - Scopus: 30Rhodium Catalyzed Reaction of Internal Alkynes With Organoborons Under Co Atmosphere: a Product Tunable Reaction(Elsevier Ltd., 2009) Artok, Levent; Kuş, Melih; Aksın, Özge; Dege, Fatma Nurcan; Özkılınç, Fatma YeldaAlkynes react with organoborons under a CO atmosphere in the presence of a rhodium(I) catalyst to afford mainly 5-aryl-2(5H)-furanones, α,β-unsaturated ketones, and indanones. The product selectivity can be tuned by modifying the reaction conditions.Article Citation - WoS: 167Citation - Scopus: 197Preparation and Characterization of Activated Carbons by One-Step Steam Pyrolysis/Activation From Apricot Stones(Elsevier Ltd., 2006) Şentorun-Shalaby, Çiğdem; Uçak Astarlıoğlu, Mine G.; Artok, Levent; Sarıcı, ÇiğdemThe activated carbons were prepared from Malatya (a city located in the south-east of Turkey) apricot stones by one-step steam pyrolysis/activation process and characterized for their pore structures. Three kinds of apricot stones that differ in their sulfur content, because of the different drying processes, were chosen for this study to investigate the effect of sulfur in the activated carbon production. The effect of process variables, such as activation temperature, soak time, and particle size range was studied on these samples. The activation temperature and time tested were in the ranges of 650-850 °C for 1-4 h. The activated carbons were evaluated for their chemical (elemental composition), surface (BET surface area, mercury porosimetry), and adsorption (iodine number) properties. Carbonization behavior of the apricot stones was investigated by thermogravimetric analysis. Scanning electron microscopy (SEM) was used to follow the changes in the carbon texture upon activation. The experimental results revealed that carbons obtained by the same conditions of activation show differences in their pore structures and adsorption characteristics due to their sulfur contents. The highest BET surface area carbon (1092 m2/g) was obtained from the low sulfur content (0.04%) apricot stone with a particle size range of 1-3.35 mm at the activation conditions of 800 °C for 4 h. The experimental results showed that commercial production of porous activated carbons from Malatya apricot stones is feasible in Turkey.Article Citation - WoS: 85Citation - Scopus: 88Effect of Immobilization on Catalytic Characteristics of Saturated Pd-N Carbenes in Mizoroki-Heck Reactions(Elsevier Ltd., 2006) Aksın, Özge; Türkmen, Hayati; Artok, Levent; Çetinkaya, Bekir; Ni, Chaoying; Büyükgüngör, Orhan; Özkal, ErhanA saturated Pd-N-heterocyclic complex was immobilized on an amorphous silica. The complex itself is of very high thermal stability. However, TEM observations, hot filtration, reusability, and poisoning tests all revealed that the complex acted only as a precatalyst to highly active Pd species in Mizoroki-Heck reactions when immobilized. The complex appears more stable when used under homogeneous reaction conditions. The immobilized complex afforded high turnover numbers, 104-105. The higher turnover frequencies were realized at the lower Pd concentrations, which is a characteristic property of ligand-free Pd catalyzed reactions.Article Citation - WoS: 45Citation - Scopus: 48Pd-Loaded Nay Zeolite as a Highly Active Catalyst for Ligandless Suzuki-Miyaura Reactions of Aryl Halides at Low Pd Loadings Under Aerobic Conditions(Elsevier Ltd., 2007) Durgun, Gülay; Aksın, Özge; Artok, LeventThe Pd(NH3)42+-loaded NaY zeolite was found to be a highly active catalyst precursor for Suzuki-Miyaura (SM) reactions of aryl bromides and aryl chlorides at low Pd concentrations in air. Aryl bromides and arylboronic acids can couple effectively both in pure water and in N,N-dimethylacetamide/water mixtures (1/1) within minutes with turnover frequencies (TOF) up to 4 × 105 h-1. The presence of a minute amount of water was crucial for the success of the reaction with chloroarenes. The excess amounts of as-received zeolite provided the necessary water for the reaction. The results suggest that the combined use of the water-zeolite system may have a synergistic effect in the reaction.Article Citation - WoS: 36Citation - Scopus: 40The Kinetics of Citral Hydrogenation Over Pd Supported on Clinoptilolite Rich Natural Zeolite(Elsevier Ltd., 2005) Yılmaz, Selahattin; Uçar, Şule; Artok, Levent; Güleç, HilalThe liquid phase hydrogenation of citral has been investigated over Pd (2.42%) supported on clinoptilolite rich natural zeolite catalyst for different reaction conditions. The zeolite support did not affect the active metal properties. This was attributed to the large size of Pd particles on the support. High selectivity (90%) to citronellal was obtained at complete conversion of citral. The catalytic activity increased with reaction temperature (80, 100, 120°C) following an Arrhenius behaviour, while selectivity remained constant for a given conversion. Selectivity to citronellal increased from 78 to 90% with increase in the amount of catalyst in the reaction solution (Citral/Pd mole ratio 293, 176 and 105). The spent catalyst regained its fresh activity and selectivity upon regeneration.Article Citation - WoS: 107Citation - Scopus: 112Heterogeneous Suzuki Reactions Catalyzed by Pd(0)-Y Zeolite(Elsevier Ltd., 2004) Artok, Levent; Bulut, HaticeThe Pd(0)-Y zeolite showed high activity in the Suzuki cross-coupling reactions of aryl bromides without added ligands. The type of base and organic solvent were found to be critical for the efficiency of the reaction. The presence of water was essential within the reaction medium. The coupling reactions occurred on the external surface of the zeolite. The catalyst is reusable.Article Citation - WoS: 56Citation - Scopus: 59Suzuki Cross-Coupling Reaction of Aryl Halides With Arylboronic Acids Catalysed by Pd(ii)-Nay Zeolite(Elsevier Ltd., 2003) Bulut, Hatice; Artok, Levent; Yılmaz, SelahattinPd(II)-exchanged NaY zeolite showed high activity in the Suzuki cross-coupling reactions of aryl bromides and iodides without added ligands. The DMF:water ratio, and the type and amount of base were found to be critical for the efficiency of the reaction. The catalyst is reusable after regeneration.Conference Object Citation - WoS: 7Citation - Scopus: 8Acylation of 2-Methoxynaphthalene Over Ion-Exchanged Ss-Zeolite(Elsevier Ltd., 2002) Kantarlı, İsmail Cem; Artok, Levent; Bulut, Hatice; Yılmaz, Selahattin; Ülkü, SemraFriedel-Crafts acylation of 2-Methoxynaphthalene was carried out over various ion-exchanged β zeolites (Mn+β, where Mn+: In3+, Zn2+, Al3+, Fe3+, La3+) with various anhydride (acetic, propionic and benzoic anhydrides), or acyl chloride (acetyl, propionyl and benzoyl chlorides) acylating reagents. The results suggested that selectivity towards the 6-substituted products was higher with the larger size anhydrides, propionic and benzoic anhydrides. The metal cation type within the zeolite significantly influenced the extent of conversion and product distribution. That La3+ exchanged zeolite displayed higher selectivity for the 6-position acylated product with anhydrides ascribed mainly to narrowing of channels by the presence of La(OH)2+ ions that leave no room for the formation of more bulky isomeric forms and to enhanced Bronsted acidity of the zeolite. With acyl chlorides, the recovery of ketone products was found to be remarkably low. 1-Acyl-2-methoxynaphthalenes actively underwent deacylation when acyl chlorides were used as the acylation reagent.