The Mechanism Of Copper-catalyzed Cyclopropanation Reaction: A Dft Study

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2007Siklopropanlar biyolojik aktiviteleri ve çeşitli organik reaksiyonlarda başlangıç bileşiği olarak kullanılmasından dolayı önemli bileşiklerdir. Diazoesterlerin olefinlerle geçiş metali katalizörleri altında yaptığı bozunmalar siklopropanların sentezi için en yaygın yöntemdir. Geçiş metalleri arasından bakır ucuz olması ve verimliligi sayesinde bu alanda en çok kullanılan katalizördür. Bu çalışmada, olefin olarak ethen sistemi sterik etkilerden elimine ederek salt reaksiyon mekanizması araştırmak için seçilmiştir. DFT (Density Functional Theory) kullanılarak siklopropanasyon için olası reaksiyon mekanizmaları B3LYP/6-31G(d) seviyede teorik olarak incelenmiştir ve elde edilen veriler temodinamik açıdan degerlendirilmiştir. Literatür verilerinide göz önüne alarak yaptığımız çalışmalarda, siklopropanasyon için belirli bir mekanizma olmayıp mekanizmanın sistemin yüküne ve diazoesterdeki substute gruba bağlı olduğu görülmüştür. Buna karşın herbir mekanizma için ortak noktaların bulunduğu belirlenmiştir.Cyclopropanes are very important molecules because of their biological activity and serving as a starting compound in various organic reactions. The metal-catalyzed decomposition of diazoesters with olefins is the most common method for synthesizing the cyclopropanes. The mechanism of the copper(I)-catalyzed olefin cyclopropanation reaction with dimethyl diazomalonate has been extensively investigated using B3LYP/6-31G(d). Ethene has been chosen as olefin to eliminate steric effects and to concentrate solely on the mechanisms. However, carbene formation and its further reaction as an electrophile have ambiguous points since the metal carbene can hardly be observed spectroscopically. In our work, four different mechanisms has been developed. In each of the mechanisms, oxygen copper interaction has been observed at the beginning of the reaction which subsequently generates rate-determining nitrogen extrusion stage in accordance with the literature. Afterthat, cyclopropanation step takes place through a direct carbene addition, metallacyclobutane intermediate formation or insertion of a second alkene. The energetics of possible carbene formation and cyclopropanation mechanisms are demonstrated by our calculationsYüksek LisansM.Sc

Diprosopus, craniorachischisis, arthrogryposis, and other associated anomalies in a stillborn lamb

Congenital malformations with multiple anomalies have been described infrequently in the veterinary literature. A stillborn male crossbred lamb with diprosopus, craniorachischisis, and arthrogryposis was examined macroscopically and histopathologically in this study. The left head was smaller than the right head. Micrencephaly, agnathia, and a rudimentary tongue, which was adherent to the palate, were present in the left head. Micrencephaly, brachygnathia superior, and cleft palate were present in the right head. Cerebellar agenesis and spinal cord hypoplasia were observed. The cerebrums and the spinal cord were covered with a tapering membranous structure. Neural and dermal tissues were noted to intervene upon microscopic examination of this structure. Disorganization of neurons was observed in both cerebrums, though it was more severe in the left one. This case demonstrates many congenital defects occurring together in a lamb

First-line treatment of patients with HER2-positive metastatic gastric and gastroesophageal junction cancer

Fluoropyrimidine+cisplatin/oxaliplatin+trastuzumab therapy is recommended for the first-line treatment of HER2-positive metastatic gastric adenocarcinoma. However, there is no comprehensive study on which platinum-based treatment should be preferred. This study aimed to compare the treatment response and survival characteristics of patients with HER2-positive metastatic gastric or gastroesophageal junction (GEJ) cancer who received fluorouracil, oxaliplatin, and leucovorin (mFOLFOX)+trastuzumab or cisplatin and fluorouracil (CF)+trastuzumab as first-line therapy. It was a multicenter, retrospective study of the Turkish Oncology Group, which included 243 patients from 21 oncology centers. There were 113 patients in the mFOLFOX+trastuzumab arm and 130 patients in the CF+trastuzumab arm. The median age was 62 years in the mFOLFOX+trastuzumab arm and 61 years in the CF+trastuzumab arm (P = 0.495). 81.4% of patients in the mFOLFOX+trastuzumab arm and 83.1% in the CF+trastuzumab arm had gastric tumor localization (P = 0.735). The median progression-free survival (PFS) was significantly higher in the mFOLFOX+trastuzumab arm (9.4 months vs. 7.3 months, P = 0.024). The median overall survival (OS) was similar in both groups (18.4 months vs. 15.1 months, P = 0.640). Maintenance trastuzumab was continued after chemotherapy in 101 patients. In this subgroup, the median OS was 23.3 months and the median PFS was 13.3 months. In conclusion, mFOLFOX+trastuzumab is similar to CF+trastuzumab in terms of the median OS, but it is more effective in terms of the median PFS in the first-line treatment of HER2-positive metastatic gastric and GEJ cancer. The choice of treatment should be made by considering the prominent toxicity findings of the chemotherapy regimens

Genç Yetişkin Kadınlarda Zayıflama Haplarına Yönelik Tutumları Ölçen Bir Ölçeğin Geliştirilmesi

Zayıfl ama hapı kullanımı sağlığa olumsuz etkileri olan bir yöntem olmasına rağmen kullanımı oldukça yaygındır (örn., altın çilek ve Hatay biberi). Bu çalışmanın amacı genç yetişkin kadın örnekleminde (19-39 yaş) bu haplara yönelik tutumları değerlendirmek için bir ölçek geliştirmektir. Ölçek 208 kadına seçkisiz örnekleme yoluyla uygulanmıştır. Sonuçlar, ölçeğin 3 faktörlü (kilo yöntemi, kişisel normlar ve güvenilir olma) olduğunu, iç tutarlılık güvenilirliğinin (α = .93) ve vücut algısı ölçeği ile korelasyonuna bakılarak test edilen ayrışan geçerliğinin (r = -.16, p < .05) yeterli olduğunu göstermiştir. Beden imajından memnuniyet azaldıkça zayıfl ama haplarına yönelik olumlu tutumların arttığı görülmüştür. Ayrıca, daha önce kilo vermek için tehlikeli yöntem girişimleri olan kadınların bu tür girişimleri olmayanlara göre zayıfl ama haplarına yönelik daha olumlu tutumlara sahip olması (t 206 = 4.48, p < .001), ölçeğin ölçüt geçerliliğine sahip olduğunu göstermiştir. Sonuç olarak, bu ölçeğin genç yetişkin kadınların zayıfl ama haplarına yönelik tutumlarını ölçen geçerli ve güvenilir bir ölçek olduğu söylenebili

Assessment of SLW-1 model in the presence of gray and non-gray particles

In this study, predictive accuracy of Gray Gas and SLW-1 approximations is benchmarked against Spectral Line-Based Weighted Sum of Grey Gases Model (SLW) in multidimensional enclosures involving gray/non-gray absorbing, emitting and scattering particles. Input data required for the radiation code and its validation are provided from two combustion tests previously carried out in a 300 kWt Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) test rig burning low calorific value Turkish lignite with high volatile matter/fixed carbon (VM/FC) ratio in its own ash. Comparisons reveal that SLW-1 approximation leads to one order of magnitude higher accuracy in heat flux and source term predictions compared to that of Gray Gas approximation in the presence of gray particles while maintaining a similar computational efficiency. In the presence of non-gray particles, SLW-1 approximation is again found to improve the predictive accuracy compared to that of Gray Gas approximation. However, it is seen that errors in heat flux and source term predictions with SLW-1 approximation are noticeably higher in the presence of non-gray particles compared to those with gray particles