Talat Özpozan

Monitoring of the polymerization of vinylacetate by near IR FT Raman spectroscopy

Abstract Emulsion polymerization of vinylacetate was studied to monitor the reaction on-line by the near infrared FT-Raman technique. The experimental conditions for monitoring the reaction by Raman spectroscopy were determined and discussed with regard to their applicability to industrial production of the polymer. The reaction goes to approximately 90% completion in 50 min and the polymerization can be succesfully monitored by taking full-scan measurements between 20–3500 cm −1 at every 8 min.

Thermal studies of p-toluidino-p-chlorophenylglyoxime and of some corresponding Ni(II), Cu(II) and Co(II) complexes

Abstract The thermal behaviour of p -toluidino- p -chlorophenylglyoxime ( p T p CPG) and its Cu(II), Ni(II), and Co(II) complexes have been studied by DTA and TG. It was found that pyrolytic decomposition undergoes with melting in both ligand and its metal complexes and metal oxides remained as end products of the metal complexes. The ligand decomposes in two stages through two different mechanisms and the metal chelates undergo decomposition in three stages. GC–MS combined system was used to identify the products during pyrolytic decompositions. The pyrolytic end products were identified by X-ray powder diffraction.

Thermal behaviours of Co(II), Ni(II), Cu(II)), and Pb(II) complexes of N,N-dipropyl-N′-benzoylthiourea

Abstract The Co(II), Ni(II), Cu(II)), and Pb(II) complexes of N,N-dipropyl-N′-benzoylthiourea (DPBT) are synthesised. The order, the activation energies, the entropies, and the pre-exponential factors of the thermal decomposition reactions are calculated with the thermogravimetric curves. The kinetic analysis of the thermogravimetric data was performed by using the Coats–Redfern and Horowitz–Metzger methods.

Vibrational and theoretical analysis of pentyl-4-benzoyl-1-[2,4-dinitrophenyl]-5-phenyl-1H-pyrazole-3-carboxylate.

Infrared spectrum of the compound, pentyl-4-benzoyl-1-[2,4-dinitrophenyl]-5-phenyl-1H-pyrazole-3-carboxylate (PBDPPC) has been measured. Conformational search through relaxed scan has been carried out to find the most stable conformational isomer. After the full geometry optimization for the most stable conformer using B3LYP and BLYP hybrid functionals of Density Functional Theory (DFT), vibrational normal modes have been calculated at the same theoretical levels. Potential Energy Distribution (PED) of each normal mode has been calculated by means of VEDA4 to obtain contributions of internal coordinates to the normal modes. Natural Bond Orbital (NBO) analysis has been performed to get insights into the possible hydrogen bonding sites for all the conformational isomers.

Novel acid mono azo dye compound: Synthesis, characterization, vibrational, optical and theoretical investigations of 2-[(E)-(8-hydroxyquinolin-5-yl)-diazenyl]-4,5-dimethoxybenzoic acid

Novel acid mono azo dye, 2-[(E)-(8-hydroxyquinolin-5yl)-diazenyl]-4,5-dimethoxybenzoic acid (HQD), was synthesized by coupling diazonium salt solution of 2-amino-4,5-dimethoxybenzoic acid (DMA) with 8-hydroxyquinoline (HQ). This dye was characterized by UV-vis, IR & Raman, (1)H and (13)C NMR spectroscopic techniques and elemental analysis. The normal coordinate analysis of HQD was also performed to assign each band in vibrational spectra. DFT (B3LYP and B3PW91) calculations were employed to optimize the geometry, to interpret NMR spectra, to calculate and to determine the stable tautomeric structure of the compound. Natural Bond Orbital (NBO) analysis was performed to investigate intramolecular interactions. The vibrational spectral data obtained from solid phase IR & Raman spectra were assigned based on the results of the theoretical calculations. UV-vis spectroscopic technique was employed to obtain the optical band gap of HQD. The analysis of the optical absorption data revealed the existence of direct and indirect transitions in the optical band gaps. The optical band gaps of HQD have been found 1.95 and 1.90eV for direct and indirect transitions, respectively.

Preparation of Organic/Inorganic Hybrid Materials Using Agregates of Poly{2-methyl-N-[2-(phenylthio)phenyl] Acrylamide-co-2-(Trimethylsyloxy)Ethyl Methacrylate} as Precursor and Vibrational Investigation of the Polymerization

Acrylamide based monomer, 2-methyl-N-[2-(phenylthio)phenyl]acrylamide (MPPA) was synthesized by reacting 2-(phenylthio) aniline with methacryloylchloride. The copolymerization of MPPA, with 2-(trimethylsyloxy)ethyl methacrylate(TSEM) was carried out with different monomer-to-monomer ratios in the feed. All the compounds were characterized by IR, Raman and 1H- and 13C-NMR techniques and SEM analysis. The elemental analysis of the copolymer composition led to the determination of reactivity ratios employing Fineman-Ross, Kelen-Tüdös and Extended Kelen-Tüdös linearization methods. These parameters were also estimated using a non-linear computational fitting procedure, known as reactivity ratio errors in variable model. The molecular weights and polydispersity index of polymers was determined by gel permeation chromatography. Thermal stability of the copolymers were found to increase with increasing mole fraction of MPPA from thermogravimetric analysis. The vibrational analysis of MPPA and poly(MPPA) were also performed to explain the vibrational spectra and to confirm the polymerization on the basis of a theoretical and experimental aproach.

Synthesis, experimental spectra (IR & Raman and NMR), vibrational analysis and theoretical DFT investigations of N-(5-(4-methylbenzoyl)-2-oxo-4-(4-methylphenyl)pyrimidine-1(2H)-yl)-4-methylbenzamide.

The title molecule, N-(5-(4-methylbenzoyl)-2-oxo-4-(4-methylphenyl)pyrimidine-1(2H)-yl)-4-methylbenzamide (C27H23N3O3), was synthesized and characterized by elemental analysis, IR, Raman, (1)H and (13)C NMR spectral data. To determine conformational flexibility, potential energy surfaces of the title compound were obtained by DFT regarding the selected degree of torsional freedom, which was varied from 0° to 360° in 6° and 20° steps. The ten conformers of the title compound were determined and it was found that the conformer 1 basis the most stable one. All conformers were also optimized by using the density functional theory (DFT/B3LYP) method with the 6-31G(d,p), 6-311G(d,p) and cc-pVDZ basis sets in the ground state. Potential energy distribution was calculated with the 6-31G(d,p) basis set. The vibrational spectra were recorded in solid phase IR and Raman spectra were compared based on the results of the theoretical calculations. The formation of hydrogen bonds was explained using natural bond orbital (NBO) analysis and spectroscopic analysis. NMR analysis and frontier molecular orbitals (FMOs) were also investigated by DFT.

Nonionic and zwitterionic forms of glycylglycylarginine as a part of spider silk protein: Spectroscopic and theoretical study.

Glycylglycylarginine as a part of GGX motif of spider silk spidroin in nonionic (non-GGR) and zwitterionic (zwt-GGR) forms have been examined from theoretical and spectroscopic aspects. The most stable conformational isomers of non-GGR and zwt-GGR were obtained through relaxed scan using the DFT/B3LYP with 6-31G(d) basis set. Nonionic and zwitterionic forms of 310-helix structures of GGR have also been calculated and compared with the most stable conformers obtained as a result of conformer analysis of isolated three peptide structures. This comparison should give an idea about the stability contribution of intermolecular interactions between the 310-helix structured peptide chains. O3LYP and B3PW91 hybrid functionals beside B3LYP have also been used for further calculations of geometry optimization, vibrational analysis, Natural Bond Orbital (NBO) analysis, HOMO-LUMO analysis and hydrogen bonding analysis. Normal Mode Analysis was carried through Potential Energy Distribution (PED) calculations by means of VEDA4 program package. IR and Raman spectra of GGR have also been used to relate the spectroscopic data obtained to electronic and structural features.