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Item A computational study on 4,7-di(furan-2-yl)benzo[c][1,2,5] thiadiazole monomer and its oligomers(Journal of Molecular Modeling, 2014-04-23) KAYI, HakanThe energy gap, Eg, between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molec ular orbital (LUMO) energy levels that determines the elec tronic and optical properties of 4,7-di(furan-2- yl)benzo[c][1,2,5]thiadiazole (FSF) polymer is calculated by performing quantum chemical calculations. First, we theoret ically investigated the most stable conformers of FSF mono mer and its corresponding oligomers at the B3LYP/6-31G(d) and B3LYP/LANL2DZ levels of theory. We reveal the theoret ical molecular structure of this very recently synthesized novel monomer and its oligomers for the first time in the literature. Our results from the B3LYP/6-31G(d) calculations indicated that FSF polymer has a low HOMO-LUMO gap of 1.55 eV to be in good agreement with the experiments. Experimental design and synthesis of novel conjugated polymers require time-consuming and expensive procedures. The findings from this study are promising for the use of computational methods in the design of the novel conjugated polymers, and help to narrow the materials to be used in design and synthesis of conjugated polymers with desired properties.Item A theoretical investigation of 4,7-di(furan-2-yl)benzo[c][1,2,5]selenadiazole-based donor–acceptor type conjugated polymer(Computational and Theoretical Chemistry, 2014-12-19) KAYİ, Hakan; ELKAMEL, AliQuantum chemical calculations are performed using density functional theory (DFT) to investigate the HOMO–LUMO energy gap of the 4,7-di(furan-2-yl)benzo[c][1,2,5]selenadiazole-based (FSeF) donor– acceptor type conjugated polymer which ascertains the optoelectronic properties and plays a crucial role, especially in polymeric solar cell applications. In this paper, the most stable conformers of the FSeF monomer and its corresponding oligomers are investigated at the B3LYP/Def2TZV and B3LYP/LANL2DZ levels of theory, and their molecular structures are revealed. The band gap of the polymer is determined by linear-fitting and extrapolation of the DFT data. This gap is found to be 1.44 eV and 1.45 eV by the B3LYP/Def2TZV, and B3LYP/LANL2DZ with PCM calculations, respectively. Our theoretical findings related to the band gap of the FSeF polymer (PFSeF) are in good agreement with other experimental stud ies in the literature and, hence, the theoretical methods used in this study are promising for the design of similar donor–acceptor type novel conjugated polymers.Item Az bilinen fakat potansiyeli yüksek sürdürülebilir bir enerji türü: Mavi Enerji(Herkese Bilim Teknoloji, 2017-08-08) Güler, Enver21. yüzyılda insanoğlunun karşılaştığı ve ileride ziyadesiyle sözkonusu olacak en temel durum enerji, su ve gıdaya olan taleptir. Bu talebin karşılanmasında ise sürdürülebilirlik şimdiki ve gelecek kuşakların temel sorunu olmaya devam edecektir. Su, enerji ve gıda arasındaki sıkı bağ açıkça gösteriyor ki; su ve enerji gıda üretiminde, su enerji üretiminde ve enerji su temini ve üretiminde en temel faktörlerdir [1]. Bunun neticesinde bu üçlü bağlam, 2035 yılında enerjiye olan talebin en fazla değer olarak % 50 olacağını öngörmektedir (Şekil 1). Enerjiye olan bu yüksek talebin yakın gelecekte fosil yakıtlar ile sürdürülebilir şekilde karşılanamayacağı aşikardır. Bu durum, enerjinin sürdürülebilir olarak üretimini sağlayacak alternatif teknikler geliştirilmesini bir öncelik haline getirmiştir.Item Conformational behaviors of trans-2,3- and trans-2,5-dihalo 1,4-diselenanes. A complete basis set, hybrid-density functional theory study and natural bond orbital interpretations(Journal of Molecular Modeling, 2014-05-14) NORİ-SHARGH, Davood; MOUSAVI, Seiedeh Negar; KAYI, HakanComplete basis set CBS-4, hybrid-density func tional theory (hybrid-DFT: B3LYP/6-311+G**) based methods and natural bond orbital (NBO) interpretations have been used to examine the contributions of the hyperconjugative, electrostatic, and steric effects on the con formational behaviors of trans-2,3-dihalo-1,4-diselenane [halo=F (1), Cl (2), Br (3)] and trans-2,5-dihalo-1,4- diselenane [halo = F (4), Cl (5), Br (6)]. Both levels of theory showed that the axial conformation stability, compared to its corresponding equatorial conformation, decreases from com pounds 1→3 and 4→6. Based on the results obtained from the NBO analysis, there are significant anomeric effects for compounds 1-6. The anomeric effect associated with the electron delocalization is in favor of the axial conformation and increases from compounds 1→3 and 4→6. On the other hand, dipole moment differences between the axial and equa torial conformations [Δ(μeq - μax)] decrease from compounds 1→3. Although Δ(μeq-μax) parameter decreases from com pound 1 to compound 3, the dipole moment values of the axial conformations are smaller than those of their corresponding equatorial conformations. Therefore, the anomeric effect as sociated with the electron delocalizations (for halogen-C-Se segments) and the electrostatic model associated with the dipole-dipole interactions fail to account for the increase of the equatorial conformations stability on going from com pound 1 to compound 3. Since there is no dipole moment for the axial and equatorial conformations of compounds 4-6, consequently, the conformational preferences in compounds 1-6 is in general dictated by the steric hindrance factor asso ciated with the 1,3-syn-axial repulsions. Importantly, the CBS-4 results show that the entropy difference (ΔS) between the equatorial axial conformations increases from compounds 1→3 and 4→6. This fact can be explained by the anomeric effect associated with the electron delocalization which affects the C2-Se bond orders and increase the rigidity of the corre sponding rings. The Gibbs free energy difference values be tween the axial and equatorial conformations (i.e. ΔGax-ax and ΔGeq-eq) of compounds 1 and 4, 2 and 5 and also 3 and 6 have been calculated. The correlations between the anomeric effect, electrostatic model, ΔGeq-ax, ΔGax-ax, ΔGeq-eq, bond orders, dipole-dipole interactions, structural parameters and confor mational behaviors of compounds 1-6 have been investigated.Item Correlations between hardness, electrostatic interactions, and thermodynamic parameters in the decomposition reactions of 3-buten-1-ol, 3-methoxy-1-propene, and ethoxyethene(Structural Chemistry, 2014-08-11) HASANZADEH, Neda; NORİ-SHARGH, Davood; KAYI, Hakan; JAVID, Nargess RezaiDecomposition of the three isomeric com pounds, 3-buten-1-ol (1), 3-methoxy-1-propene (2), and ethoxyethene (3), at two different (300 and 550 K) tem peratures has been investigated by means of ab initio molecular orbital theory (MP2/6-311?G**//B3LYP/6- 311?G**), hybrid-density functional theory (B3LYP/6- 311?G**), the complete basis set, nuclear magnetic reso nance analysis, and the electrostatic model associated with the dipole–dipole interactions. All three levels of theory showed that the calculated Gibbs free energy differences between the transition and ground state structures (DG=) increase from compound 1 to compound 3. The variations of the calculated DG= values can not be justified by the decrease of the calculated global hardness (g) differences between the ground and transition states structures (i.e., D[g(GS)-g(TS)]). Based on the synchronicity indices, the transition state structures of compounds 1–3 involve syn chronous aromatic transition structures, but there is no significant difference between their calculated synchronicity indices. The optimized geometries for the transition state structures of the decomposition reactions of compounds 1–3 consist in chair-like six-membered rings. The variation of the calculated activation entropy (DS=) values can not be justified by the decrease of D[g(GS)- g(TS)] parameter from compound 1 to compound 3. On the other hand, dipole moment differences between the ground and transition state structures [D(lTS-lGS)] decrease from compound 1 to compound 3. Therefore, the electrostatic model associated with the dipole–dipole interactions jus tifies the increase of the calculated DG= values from compound 1 to compound 3. The correlations between DG=, D[g(GS)-g(TS)], (DS=), k(T), electrostatic model, and structural parameters have been investigated.Item İlaç Araştırmalarında Yeni Nesil Uygulamalar: Kontrollü İlaç Salımı(Bilim ve Teknoloji, 2012-09-21) İŞGÖR, Belgin S.; KORKMAZ ÖZKAN, Filiz16.yüzyılda yaşamış olan ve bugünkü Modern tıbbın kurucularından sayılan Paracelsus’un “Her şey zehirdir. Zehirle ilacı ayıran dozudur” sözü, bugünkü modern toksikolojinin temeli olan doz-cevap ilişkisine dikkat çekmesi açısından son derece önemlidir. Günümüzde ilaç olarak sunulan sentetik ve doğal kaynaklı kimyasal bileşiklerin vücuda alımı genel olarak ağızdan (oral) katı veya sıvı formlarda, damar ve kas içerisine sıvı enjeksiyonuyla, nazal yol aracılığıyla sprey veya toz formunda inhalatör yardımıyla, veya deriden lokal uygulamalarla gerçekleşmektedir. Vücuda verilen ilaç ilk olarak dolaşım sistemine alınır ve tedavi için hedeflenen dokuya kan damarları ile taşınır. Hedef dokulara ise bu dokulara nüfuz etmiş kılcal damarlar yoluyla ulaşır. İlacın vücuda alımından hedef dokuya taşınması sürecinde, damar yolu üzerinde bulunan tüm dokularca alınıp hücresel mekanizmalarca işlenmesi mümkündür.Item Natural bond orbital, nuclear magnetic resonance analysis and hybrid-density functional theory study of σ-aromaticity in Al2F6, Al2Cl6, Al2Br6 and Al2I6(Journal of Molecular Modeling, 2013-02-11) NORI-SHARGH, Davood; YAHYAEI, Hooriye; MOUSEVI, Seiedeh Negar; MAASOOMI, Akram; KAYI, HakanNatural bond orbital (NBO), nuclear magnetic res onance (NMR) analysis and hybrid-density functional theory based method (B3LYP/Def2-TZVPP) were used to investigate the correlation between the nucleus-independent chemical shifts [NICS, as an aromaticity criterion], σAl(1)-X2(b) → σ*Al(3)-X4(b) electron delocalizations and the dissociation ener gies of Al2F6, Al2Cl6, Al2Br6 and Al2I6 to 2AlX3 (X=F, Cl, Br, I). The results obtained showed that the dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6 decrease from Al2F6 to Al2I6. Like aromatic molecules, these compounds have relatively significant negative NICSiso(0) values. Clearly, based on mag netic criteria, they exhibit aromatic character and make it possible to consider them as σ-delocalized aromatic species, such as Möbius σ-aromatic species. The σ-aromatic character which is demonstrated by their NICSiso(0) values decreases from Al2F6 to Al2I6. The NICSiso values are dominated by the in-plane σ22 (i.e., σyy, the plane containing halogen atoms bridged) chemical shift components. The increase of the NICSiso values explains significantly the decrease of the corre sponding dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6. Importantly, the NBO results suggest that in these compounds the dissociation energies are controlled by the stabilization energies associated with σAl(1)-X2(b) →σ*Al(3)- X4(b) electron delocalizations. The decrease of the stabilization energies associated with σAl(1)-X2(b) →σ*Al(3)-X4(b) electron delocalizations is in accordance with the variation of the calculated NICSiso values. The correlations between the dis sociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6, σAl(1)- X2(b) →σ*Al(3)-X4(b) electron delocalizations, natural atomic orbitals (NAOs) and NICSiso values have been investigated.Item Spectroelectrochemical Investigation of Nuclease Active Pt(II) Complexes Containing Pyrrole Oxime(Electrochimica Acta, 2015-01-28) ALTUNÖZ ERDOĞAN, Deniz; KAYI, Hakan; ÖZALP YAMAN, ŞenizIn this paper, the electrochemical oxidation of three Pt(II) complexes containing pyrrole oxime (HL) having a general formula of [Pt(NH3)Cl(L)] (1), [Pt(L)2] (2), and K[PtCl2(L)] (3) has been investigated by in-situ spectroelectrochemistry in dimethylformamide (DMF). An irreversible metal-based oxidation process occurs during the anodic scan for each of the three complexes. The electronic absorption spectral changes indicate that all the three complexes generate similar Pt(IV) compounds and free ligand. Our experimental data is supported by quantum chemistry calculations utilizing density functional theory. In addition, the frontier orbital energy distributions indicate that electron densities are localized on mainly platinum atom.Item TÜRKİYE'DE TEMEL BİLİMLERİN ÇÖKÜŞÜ(Bilim ve Teknoloji, 2015-11-09) CİHANER, AtillaÖncelikle Türkiye'nin bugünkü bilim ve teknolojideki konumunu görmek ve kat ettiği mesafeyi anlayabilmek için, Türkiye'nin geçmişten bugüne olan bilim ve teknolojinin üç ayağı olarak nitelendirebileceğimiz, bilim politikalarını, bilim üretimini ve bilim anlayışını kısaca göz atmakta fayda var. Osmanlı'daki Batılılaşma, modernleşme ve yenileşme hareketleri 17. yy'ın sonlarına doğru başlayıp (1683 Viyana bozgunu sonrası) 18. yy'ın ilk yarısına kadar sürer. Lale Devri, ilk matbaa'nın kullanımı, II. Mahmut Devri, III. Selim Devri, Tanzimat, vb. olaylar Osmanlı'ını Batılılaşma ve modernleşme serüvenindeki önemli olaylardan birkaçıdır.Item TÜRKİYE’DE TEMEL BİLİMLERİN ÇÖKÜŞÜ(Bilim ve Teknoloji, 2015-11-09) CİHANER, AtillaÜniversitelerdeki ilk çöküşün habercisi, temel bilimler kontenjanında yaşanan sıkıntılar ve kapanan bölümler olmuştur. Yürütülen bilim politikalarının yanlışlığından kaynaklı olarak son yıllarda boş kontenjanlarla gündemde olan temel bilimler programlarıyla ilgili çalışma başlatan YÖK, 2014 yılında 11’den az öğrenci kaydolan devlet üniversitelerindeki programlara artık kontenjan verilmeyeceğini duyurmuştur. Uygulanan bilim politikasının yanlışlığını 2010 yılında üniversitelerin temel bilimler bölümlerine ayrılan kontenjan sayılarından net olarak anlamak mümkündür. Bir yıl öncesinde mevcut kontenjanlar doldurulmamış olmasına rağmen kontenjan sayıları arttırılırken bu bölümlere yerleşen öğrenci sayılarında dramatik bir düşüş görülmüştür. YÖK’ün kontenjan verilmeyeceğine dair yaptığı açıklama bir domino etkisi yaratmış ve sonraki yıllarda temel bilimler bölümleri bir bir kapanmaya başlamıştır.