1,721,030 research outputs found
Semiemprical gas phase study of tautomerizm of cytosine, uracil and their tautomeric forms
No full textBu çalışmada sitozin, urasil ve bu moleküllerin olası tautomerik yapıların geometrileri, relatif stabiliteleri, oluşum entalpileri, iyonlaşma potansiyelleri, dipol momentleri ve entropi değerleri semiampirik moleküler orbital yönteminde AMI, PM3 ve MNDO metotları ile gaz fazında hesaplandı. Elde edilen sonuçlardan daha kararlı formlar belirlendi.The geometry, relative stabilities, heat of formations, ionization potentials, dipole moments and entropy properties of cytosine, uracil and their tautomeric forms were calculated with full geometry optimization using AMI, PM3 and MNDO semiempirical methods in gas phase. The results predicted were more stable forms
MICROWAVE ASSISTED and TRADITIONAL SYNTHESIS and CHARACTERIZATION of 2-ALLYL-6,6\'-[(3,3\'-DIMETHOXY[1,1\'-BIPHENYL]-4,4\'- DIYL)BIS(NITRILOMETHYLIDYNE)]BIS-PHENOL and EXPERIMENTAL and THEORETICAL INVESTIGATION of ITS TAUTOMERIC PROPERTIES
Full text link2-Allil-6,6\'-[(3,3\'-dimetoksi[1,1\'-bifenil]-4,4\'-diyil)bis(nitrilometiliden)]bis-fenol (3) Schiff bazı bileşiği, 3-allilsalisilaldehitin (1) o-dianisidin (2) ile kondenzasyon reaksiyonundan geleneksel ısıtma ve mikrodalga-ışınlama yöntemi kullanılarak sentezlendi. Bileşik (3)'ün kimyasal yapısı element analizi, FTIR, 1H NMR, ve 13C NMR teknikleri kullanılarak karakterize edildi. Bileşiğin farklı organik çözücülerde fenol-imin (O-H…N) ve keto-amin (O…H-N) tautomerik dengeleri, UV-görünür bölge spektrofotometrik yöntem kullanılarak incelendi ve keto-amin yüzdeleri hesaplandı. Ayrıca, bileşiğin geometrisi, farklı çözücülerdeki fenol-imin ve keto-amin tautomerlerinin enerjisi, moleküliçi O-H…N ve O…H-N hidrojen bağ uzunluğu, UV-görünür bölge uyarılma enerjisi ve ossilatör kuvveti DFT (B3LYP)/6-311+G(d,p) hesaplama yöntemiyle teorik olarak hesaplandı ve hesaplamalar deneysel sonuçlar ile karşılaştırıldıSchiff base compound 2-allyl-6,6\'-[(3,3\'-dimethoxy[1,1\'-biphenyl]-4,4\'- diyl)bis(nitrilomethylidyne)]bis-phenol (3) was synthesized using traditional heating and microwave- irradiation method with the condensation reaction of 3-allylsalicylaldehyde (1) and o-dianisidine (2). The chemical structure of compound (3) was characterized by elemental analysis, FTIR, 1H NMR and 13C NMR techniques. The tautomeric equilibria (for phenol-imine O-H...N and keto-amine O... H-N tautomers) in various organic solvents were studied using UV-visible region spectrophotometric method and keto-amine percentages were calculated. Furthermore, the geometry of compound, the energies of phenol-imine and keto-amine tautomers in different organic solvents, intramolecular O-H...N and O...H- N hydrogen bond length, UV-visible excitation energy and oscillator strength were calculated with the theoretical calculation method DFT (B3LYP)/6-311+G(d,p) and calculations were compared with experimental results
Quantum chemical studies on some 1,2,4-triarylsubstituted imidazoles
No full textWOS: 000173428400011The geometries, proton affinities and thermodynamic properties of some 1,2,4-triarylsubstituted imidazole derivatives were calculated with full geometry optimization using AM1 and PM3 methods in aqueous phase. A possible correlation between experimentally obtained results and the computed data was searche
Novel formazan derivatives containing phenylsulfanyl and carbonyl units: synthesis, optical and electrochemical properties
No full textWOS: 000385633100085A series of phenylsulfanyl and aryl carbonyl containing formazan derivatives 4a-4h and 5a-5h were synthesized by coupling of substituted phenylhydrazones with diazonium salts of 2-(phenylthio) benzenamine and 5-chloro-2-benzoylbenzenamine in pyridine. The electronic properties of the new formazans were studied by cyclic voltammetry and UV-vis spectroscopy. Fluorescence emission wavelengths were measured in solution, and fluorescence quantum yields and Stokes shifts were calculated. Computational studies were carried out on the tautomer structures formed through intramolecular proton transfer in the formazan backbone, and their HOMO-LUMO energy values were estimated. In addition, the influences emerging from ether, thioether and carbonyl groups on the properties of formazans were elaborated.Anadolu University Research Fund [1004F94, 1102F027]We are very grateful to the Anadolu University Research Fund for providing financial support for this project (Projects No: 1004F94 and 1102F027). We are indebted to the Medicinal Plants and the Medicine Research Center of Anadolu University Eskisehir (Turkey) for the NMR measurements and to Anadolu University for the ChemBioDraw Ultra 2013 program
Bazı Schıff Bazların Teorik ve Deneysel Çalışmaları
No full textAldehitlere ait karbonlar aminlerin nükleofilik saldırmasına uygundur. Bu reaksiyonun sonunda üründe C=O çiftli bağı yerine C=N bağı oluşur. Bu tip birleşiklere Schiff bazı denir. Bu çalışmada Schiff bazları 2-kinolin aldehit ve bazı anilin türevlerinden sentezlenmiştir. Sentezlenen moleküller bazı spektroskopik yöntemlerle karakterize edilmiştir. Moleküllerin pKa değerleri potansiyometrik metod ve DFT metoduyla hesaplanmıştır. Spektroskopik ve teorik sonuçlar karşılaştırılmıştırThe electrophilic carbon atoms of aldehydes can be targets of nucleophilic attack by amines. The end result of this reaction is a compound in which the C=O double bond is replaced by a C=N double bond. This type of compound is known as a Schiff base. In this study some Schiff bases were synthesized from 2-quinoline aldehyde and some aniline derivatives and the molecules were characterized with spectroscopic methods. The pKa values of the molecules calculated with potentiometric methods and DFT calculated methods. The spectroscopic and the potentiometric results were compared with the calculated result
Electronic structure and optical properties of Schiff base hydrazone derivatives by solution technique for optoelectronic devices: Synthesis, experiment and quantum chemical investigation
No full textWOS: 000449310600004In this study, electronic, optical and spectroscopic FT-IR, UV properties of new synthesized Schiff base hydrazone derivatives, 1-(4-nitrophenyl)-2-(4-phenoxybenzylidene)hydrazone and 1-(2,4-dinitropheny1)-2-(4-phenoxybenzylidene)hydrazone are investigated by performing solution techniques and theoretical calculations. Solvatochromism and solute-solvent interactions were discussed based on the spectral results. It is observed that Schiff base hydrazone derivatives exhibit positive solvatochromism. Energy band gap E-g is determined experimentally and theoretically in solution. Concentration effect on E-g was investigated in DCM solvent for different molarities of solute. It is observed that solvent and concentration can be used for tuning E-g. NO2 substituent group gives rise to E-g value lows 0.3 eV. The refractive index (n) values were obtained from Moss, Ravindra, Herve-Vandamme, Kumar-Singh and Reddy relations based on E-g data. It is observed that n can be controlled with solvents and concentration of solutions. External electric field (EF) is theoretically applied in order to tuning HOMO-LUMO gap and dipole moment. Consequently, Schiff base hydrazone derivatives intend to be insulator under applied EFBitlis Eren University, Research Foundation [BEBAP-2013.04, BEBAP-2014.05]; Bitlis Eren UniversityThe authors greatly appreciate Bitlis Eren University, Research Foundation for the financial support via BEBAP-2013.04 and BEBAP-2014.05 projects. The author greatly thanks to Bitlis Eren University for supporting this study by Gaussian 09W and Gauss-View5.0 software. The authors greatly thank Dr. Halil Berber for performing experiments in Chemistry Department, Faculty of Science, Anadolu University
A quantum chemical study on structure of 1,2-bis(diphenylphosphinoyl)ethane and phenol cocrystal
Full text linkWOS: 000225145100022The cocrystal of 1,2-bis(diphenylphosphinoyl)ethane (DPPEO) with phenol (1: 1) were studied theoretically with AM1, PM3, MNDO and MINDO/3 semi-empirical methods to elucidate its structure. The bond lengths and angles from theoretical studies of molecule DPPEO/phenol (1: 1) were found to be as expected. Theoretical results, concerning with intermolecular van der Waals forces in cocrystal, were compared with the previously obtained experimental data and AM1 results were found to be the best fit for bond lengths and angles of DPPEO/pheno
Spectrophotometric determination of the acidity dissociation constants of symmetric Schiff base derivatives
No full textIn this study, the acidity constants of series symmetric Schiff base derivatives have been determined using the UV-visible spectrophotometric method at a temperature of 25(±0.1) °C. The deprotonated acidity constants (pKa) have been found to be associated with the deprotonation of phenolate oxygen. The first and the second protonated acidity constants (pKa1 and pKa2) have been found to cause the protonation of the imine nitrogen atom for all molecules. The deprotonated acidity constants (pKa) were found for molecules 5 (9.088), 8 (9.848), 6 (10.243), 2 (10.2569), 3 (10.297), 1 (10.587), 7 (10.692) and 4 (10.804). The first protonation (pKa1) was found for molecules 2 (3.432), 5 (4.207), 8 (4.612), 7 (4.758), 4 (4.995), 1 (5.288), 6 (5.606) and 3 (6.452). The second protonation (pKa2) was found for molecules 2 (-5.384), 8 (-5.165), 5 (-5.028), 7 (-4.775), 4 (-4.518), 1 (-4.111), 6 (-3.866) and 3 (-3.212)
Bazı 4- (Fenildiazenil)Benzen-1,3-Diol Türevlerinin Sentezi, Karakterizasyonu, Tautomer ve Asitlik Sabitlerinin Spektroskopik Yöntem ile Hesaplanması
Full text linkBu çalışmada, benzen-1,3-triol ve bazı sübstitüe amino benzen ile monoazo boyar maddeleri sentezlendi. Kimyasal yapıları spektroskopik teknikler ile aydınlatıldı. 4-(fenildiazenil)benzen-1,3-diol türevi bileşiklerinin tautomerik özellikleri saf polar ve apolar çözücülerde (dimetil sülfoksit, etanol, kloroform, benzen ve siklohekzan) asidik ve bazik ortamlarda 25±1 °C, 35±1 °C ve 45±1 °C UV-Vis. Spektrometresinde ölçüldü. Sentezlenen bileşiklerin azo-hidrazon tautomerleri hesaplandı. Bütün azo boyar madde bileşiklerinde azo tautomer formunun baskın olduğu belirlendi. Aynı bileşiklerin asitlik sabitleri 25 °C (?0,1 °C) UV-Vis. Spektroskopik teknik ile belirlendi.In this study, monoazo dyes were synthesized through the diazotization of several substituted aminobenzenes and couplings with benzene-1,3-diols. The chemical structures of these compounds were characterized (phenyldiazenyl)benzene-1,3-diol spectrophotometry in pure polar or apolar media (dimethyl sulfoxide, ethanol, chloroform, benzene and cyclohexane) under acidic and basic conditions at 25+-1 °C, 35+-1 °C and 45+-1 °C. The percentage of the azo-hydrazone tautomers was calculated for all of the compounds. The UV-Vis. analysis reveals that the azo form is dominant in the presence of azo-hydrazone tautomerism for all azo dyes. Concurrently, the acidity constants for these derivatives were determined using a UV-Vis. spectroscopic technique at 25 °C (?0.1 °C)
Acidity constant determination of novel drug precursor benzothiazolon derivatives including acyl and piperazine moieties
No full textWOS: 000320481700030PubMed ID: 23644445In this study, protonation and deprotonation behaviors of eight new drug precursor benzothiazolon derivatives in all of acidic and basic scale (super acidic, pH, super basic regions) are analyzed by using UV-visible spectrophotometric technique. Acidity constants (pK(a)), elucidation of the structure and protonation mechanisms of the studied molecules are obtained. Substituent effect on acidity constant values is discussed. These molecules are protonated from oxygen atom of acetamide group in the keto form. The protonation is found to be considerably contributed by the keto formTurkish Scientific Council (TUBITAK) [108T192]; Anadolu University, Faculty of Science, Department of ChemistryWe are grateful to Turkish Scientific Council (TUBITAK) for the financial support to this work via the Research Project with the number of 108T192. We would like to thank Associated Professor Doctor Ahmet Cabuk and his PhD student Serap Gedikli for support with the UV-2550 Shimadzu UV-visible spectrophotometer. We would like to thanks Anadolu University, Faculty of Science, Department of Chemistry for support with CAChe 6.1. software
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