Yasemin Çimen

Synthesis of novel methacrylate based adsorbents and their sorptive properties towards p-nitrophenol from aqueous solutions

The polymeric adsorbents were synthesized from 2-dimethylaminoethyl methacrylate (DMA) and [2-(methacryloyloxy)ethyl]dimethylhexadecylammonium bromide (DMAC(16)) monomers in the presence of ethylene glycol dimethacrylate (EDMA) cross-linking monomer using suspension polymerization technique and their adsorption efficiencies in the removal of p-nitrophenol from aqueous solutions were investigated. DMAC(16) monomer was prepared by means of modification of DMA monomer with 1-bromohexadecane. Adsorption experiments were carried out in a batch system and the experimental parameters were evaluated with respect to pH, agitation time, temperature and initial p-nitrophenol concentration. It was observed that the adsorbent poly[2-(methacryloyloxy)ethyl]dimethylhexadecylammonium bromide (p-DMAC(16)) prepared from DMAC(16) monomer was more effective in the removal of p-nitrophenol than the adsorbent poly(2-dimethylaminoethyl methacrylate) (p-DMA) prepared from DMA monomer. The effective pH ranges for the adsorption of p-nitrophenol onto p-DMAC(16) and p-DMA were 2-12 and 3-9, respectively. Langmuir and Freundlich adsorption models were used to describe the isotherms and find isotherm constants. The Langmuir model was well agreed with experimental data for both adsorbents. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models were used to understand the mechanism of the adsorption process and it fitted very well the pseudo-second-order kinetic model for each adsorbent. Thermodynamic parameters such as activation energy and changes of free energy, enthalpy, and entropy were also evaluated for the adsorption of p-nitrophenol onto each adsorbent. Additionally, reusability of the adsorbents was investigated and the results showed that both adsorbents can be employed many times without a significant loss in their adsorption capacities for the removal of p-nitrophenol from water.

Facile, efficient, and environmentally friendly α- and aromatic regioselective chlorination of toluene using KHSO5 and KCl under catalyst-free conditions

Toluene was subjected to room-temperature chlorination with the KHSO5–KCl system in organic solvent–water mixtures. In a typical reaction, the amounts of toluene, KHSO5, and KCl were 1.0, 5.0 and 7.5 millimoles, respectively. The reaction mixtures, consisting of an organic solvent (2.50 mL) and water (1.50 mL), were rather multiphase like slurry. Depending on the nature of the organic solvent present in the solvent mixtures, either α-chlorination or aromatic chlorination of toluene was favoured. The chlorinated solvents CH2Cl2, CHCl3, and CCl4 favoured the α-chlorination, yielding >81% benzyl chloride selectivity in 38–59% toluene conversions in 1 hour. The water miscible polar solvents C2H5OH, CH3OH, and CH3CN favoured the aromatic chlorination, yielding 61–86% chlorotoluene selectivity in >98% toluene conversions in 1 hour. Reactions carried out in all solvent mixtures yielded only chlorinated toluene products. The method presented here for the regioselective chlorination of toluene meets the goals of green chemistry as well in a number of ways: (a) catalyst-free conditions; (b) nontoxic, green, safe, stable, and inexpensive reagents; (c) low environmental impact; (d) no heating or cooling; (e) simple and cheap operation; and (f) high regioselectivity.

2,6-Di-tert-Bütilfenolün Potasyum Peroksimonosülfat, tert-Bütil hidroperoksit ve Hidrojen Peroksit Varlığında Kobalt-Tetra-(4-karboksifenil)porfirin Katalizörlüğünde Oksidasyonu

Bu calismada 2,6-di- tert -butilfenolun (DTBP) cesitli oksidantlarla [5,10,15,20-tetrakis(4-karboksifenil)porfirinato]kobalt(II) ([CoTCPP]) tarafindan katalizlenen oksidasyonu arastirilmistir. Oksidant olarak potasyum peroksimonosulfat (okzon), tert -butilhidroperoksit (Bu t OOH) veya hidrojen peroksit (H 2 O 2 ) kullanilmis ve reaksiyonlar hacimce %10-15 su iceren metanol cozeltilerinde oda sicakliginda yurutulmustur. Oksidasyona substrat, katalizor ve oksidant derisimlerinin etkileri incelenmistir. Reaksiyon urunleri gaz kromatografisi-kutle spektrometresiyle (GC-MS) belirlenmis ve urunlerin ve reaksiyona girmemis DTBP miktarlari gaz kromatografisi (GC) ile elde edilen kromatogramlardaki pik alanlarindan belirlenmistir. DTBP oksidasyonunda oksidant olarak okzon ve Bu t OOH kullanildiginda [CoTCPP] katalitik aktivite gostermistir. H 2 O 2 varliginda ise [CoTCPP] katalitik aktivite gostermemistir.

Oxidation of 2,4,6-Trichlorophenol Catalyzed by Tetraphenylporphyrin Tetrasulfonate with Different Metal Ions in the Presecence ofDifferent Oxidants

Anahtar kelimeler Oksidasyon; Metalotetrafenilporfirin tetrasülfonat; Katalizör; 2,4,6-triklorofenol Özet Bu çalışmada demir-tetrafenilporfirin tetrasülfonat ([FeTSPP]) katalizörlüğündetert-bütil hidroperoksit (Bu t OOH) veya hidrojen peroksit (H2O2) varlığında 2,4,6-triklorofenolün (TCP) oksidasyonu araştırılmıştır. Reaksiyonlar hacimce %10-15 su içeren metanol çözeltilerinde oda sıcaklığında yürütülmüş ve oksidasyonlar üzerine substrat, katalizör ve oksidant derişimlerinin etkileri incelenmiştir. Reaksiyon karışımlarının ürün bileşimleri GC-MS, nicel analizleri ise GC kullanılarak yapılmıştır. [FeTSPP] katalizörlüğünde TCP nin H2O2ile oksidasyonunda en yüksek katalitik döngü sayısı (Turnover number, TON) ve katalitik döngü frekansı (Turnover frequency, TOF) 512,0 olarak katalizör:substrat:oksidant mol oranı 1:500:300 olan reaksiyon içinelde edilmiştir. Ayrıca kobalt-, nikel-, paladyumve bakırtetrafenilporfirin tetrasülfonatın TCP oksidasyonu için katalitik aktiviteleri incelenmiş ve bu yapıların katalitik aktivite göstermediği belirlenmiştir. Tekrar kullanılabilirliğini iyileştirmek amacıyla [FeTSPP],Amberlite IRA-900 reçinesine bağlanmış, ancak [FeTSPP]-IRA heterojen katalizörü ile yürütülen deneylerde TCP dönüşümünün azaldığı, optimum oksidasyon süresinin arttığı ve çevrim sayısının arttırılamadığı belirlenmiştir.