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141.
Frank Jordan Reza Fathi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):341-344
Abstract α-D-Ribofuranosyl-1,2-cyclic monophosphate and 5-phospho-α-D-ribofuranosy1-1, 2-cyclic monophosphate were synthesized in good yields. The five-membered ring cyclic phosphates have 31p chemical shifts similar to those found for such structures, presumably reflecting the smaller O-P-O bond angle, compared to that in six-membered ring phosphates. The rate of OH? catalyzed ring opening was similar to that reported for ethylene phosphate, indicating relief of ring strain during hydrolysis. α-D-Ribofuranosyl-1, 2-cyclic monophosphate was found to irreversibly inactivate purine nucleoside phosphorylase (EC 2.4.2.1) at its catalytic center. 相似文献
142.
Foad Kazemi Ali Reza Kiasat 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):1333-1337
Epoxids are efficiently converted to the corresponding thiiranes by ammonium thiocyanate (NH 4 SCN) in the presence of catalytic amounts of oxalic acid with excellent isolated yields under mild and nonaqueous reaction conditions. This conversion performed under both conventional heating and microwave conditions. Distinct rate enhancement is observed under microwave irradiation. 相似文献
143.
Abdolreza Iraj Mansouri Zahra Hassani Mohammad Reza Islami 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1753-1758
2-Aminobenzoic acids or 4-aminobenzoic acid react with dimethyl acetylenedicarboxylate/triphenylphosphine in less than 20 min at 15–25°C to produce new organic phosphorus compounds in good to excellent yields. The conversion occurs with selective N- over O-alkylation of the amino group and isolation of the products is accomplished simply by filtration. 相似文献
144.
Ali Reza Mahdavian Mahdi Abdollahi Leila Mokhtabad Farshid Ziaee 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):1583-1596
Many reports exist in the literature about the application of 1H and 13C‐NMR techniques to analyze the copolymer structure and composition and also determination of reactivity ratios. In this work, on‐line 1H‐NMR spectroscopy has been applied to identify reactivity ratios of itaconic acid and acrylonitrile in the solution phase (DMSO as the solvent) and in the presence of AIBN as the radical initiator. All the peaks corresponding to the existing protons were assigned quietly. Therefore, the kinetics of the copolymerization reaction was investigated by studying the variation of integral of two characteristic peaks regarding each monomer. The obtained data were used to find the reactivity ratios of acrylonitrile and itaconic acid by linear least‐squares methods such as Finemann‐Ross, inverted Finemann‐Ross, Mayo‐Lewis, Kelen‐Tudos, extended Kelen‐Tudos and Mao‐Huglin. In addition, a non‐linear least‐square method (Tidwell‐ Mortimer) was used at low conversions. Extended Kelen‐ Tudos and Mao‐Huglin were applied to determine reactivity ratio values at high conversions as well. 相似文献
145.
Hossein Reza Darabi Abbas Darestani Farahani Mohammad Hashemi Karouei Kioumars Aghapoor Rohoullah Firouzi Rainer Herges 《Supramolecular chemistry》2013,25(9):653-657
A new E,E-stilbenophane was synthesised and characterised. The crystal structure of this cyclophane shows that this molecule has a cup-shaped structure, which hosts a phenyl ring of neighbouring molecule as guest in its cavity with a π–π distance of about 3.7 Å. Moreover, the NMR spectra and theoretical analysis (gauge-independent atomic orbitals (GIAO) and quantum theory of atoms in molecules (QTAIM)) suggest that the silver recognition by E,E-stilbenophane host molecules is based on cation–π interactions in which the π-electrons of the double bonds play a major role. 相似文献
146.
Mohammad Hossein Keshavarz Somayeh Moradi Bahman Ebrahimi Saatluo Hadi Rahimi Ali Reza Madram 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1453-1463
A novel general method is introduced to predict deflagration temperature of organic energetic compounds containing at least –NNO2, –ONO2, or –CNO2 groups. Deflagration temperature is an important safety parameter in working with dangerous energetic compounds and their environmental problems. It is shown that the contribution of some molecular structure parameters can be used to interpret thermal decomposition of an energetic compound. For 86 energetic materials (corresponding to 102 measured values) with different molecular structures, the new correlation has the root mean square (rms) and the average deviations of 23.8 and 19.0 K, respectively. The new method is also tested for some energetic compounds with complex molecular structures, e.g., two new organic energetic molecules N,N′-bis(1,2,4-triazol-3yl)-4,4′-diamino-2,2′,3,3′,5,5′,6,6′-octanitroazobenzene (BTDAONAB) and 2,4,6-trinitrophloroglucinol. 相似文献
147.
Reza Ojani Jahan-Bakhsh Raoof Akbar Khanmohammadi Ebrahim Zarei 《Journal of Solid State Electrochemistry》2013,17(1):63-68
The widely utilization of phenol and its derivatives such as 3-nitrophenol (3-NP) has led to the worldwide pollution in the environment. In this study, Ti/TiO2 photoelectrode was prepared with anodic oxidation of Ti foil electrode and then the photoelectrocatalytic (PEC) degradation of 3-NP was performed via this electrode, comparing with photocatalytic (PC), electrooxidation and direct photolysis by ultraviolet light. A significant photoelectrochemical synergetic effect in 3-NP degradation was observed on the Ti/TiO2 electrode and rate constant for the PEC process of Ti/TiO2 electrode was about three times as high as its PC degradation process. 3-NP concentration monitoring was carried out with differential pulse voltammetry. Results showed that PEC degradation has highest effect on concentration decreasing of 3-NP at solution and degraded it about 38 %, while other processes degradation efficiencies were about 4, 7, and 12 % for electrooxidation, direct photolysis and photocatalytic degradation, respectively. Finally, effects of solution pH and applied potential on degradation efficiency were studied and results showed that optimum pH for degradation is equal 4.00 and optimum potential is 1.2 V vs. Ag|AgCl|KCl (3M) reference electrode. 相似文献
148.
Mahdi Tohidian Seyed Reza Ghaffarian Seyed Emadodin Shakeri Erfan Dashtimoghadam Mohammad Mahdi Hasani-Sadrabadi 《Journal of Solid State Electrochemistry》2013,17(8):2123-2137
Nanocomposite membranes based on polyelectrolyte complex (PEC) of chitosan/phosphotungstic acid (PWA) and different types of montmorillonite (MMT) were prepared as alternative membranes to Nafion for direct methanol fuel cell (DMFC) applications. Fourier transform infrared spectroscopy (FTIR) revealed an electrostatically fixed PWA within the PEC membranes, which avoids a decrease in proton conductivity at practical condition. Various amounts of pristine as well as organically modified MMT (OMMT) (MMT: Cloisite Na, OMMT: Cloisite 15A, and Cloisite 30B) were introduced to the PEC membranes to decrease in methanol permeability and, thus, enhance efficiency and power density of the cells. X-ray diffraction patterns of the nanocomposite membranes proved that MMT (or OMMT) layers were exfoliated in the membranes at loading weights of lower than 3 wt.%. Moreover, the proton conductivity and the methanol permeability as well as the water uptake behavior of the manufactured nanocomposite membranes were studied. According to the selectivity parameter, ratio of proton conductivity to methanol permeability, the PEC/2 wt.% MMT 30B was identified as the optimum composition. The DMFC performance tests were carried out at 70 °C and 5 M methanol feed and the optimum membrane showed higher maximum power density as well as acceptable durability compared to Nafion 117. The obtained results indicated that owing to the relatively high selectivity and power density, the optimum nanocomposite membrane could be considered as a promising polyelectrolyte membrane (PEM) for DMFC applications. 相似文献
149.
Marzieh Saeedi Maryam Anafcheh Reza Ghafouri Nasser L. Hadipour 《Structural chemistry》2013,24(2):681-689
Density functionla theory (DFT) calculations are performed to characterize geometric and electronic features of the octahedral Al n N n and Al n P n cages (n = 12, 16, 28, 32, and 48). Toward this aim, 15N, 27Al, and 31P chemical shielding (CS) tensors as well as natural charge analyses are calculated for the optimized structures. CS parameters detect three distinct electronic environments for atoms within the Al n N n and Al n P n cages. The chemical shifts of N2 sites belonging to a hexagon and surrounded by three hexagons and a square obtained are different from those of N3 sites belonging to a hexagon that is surrounded only by hexagons—due to different curvatures exerted at the sites with different local structures. In addition, there is an increasing tendency in the Δσ values of the three local structures, Δσ (N1) > Δσ (N2) > Δσ (N3), N1 sites belonging to four-membered rings. The chemical shieldings of those Al and P sites belonging to a hexagon that is surrounded only by hexagons in the cages (360.7–366.7 and 496.5–514.7 ppm) are close to those previously reported for AlP nanotubes. Three distinct electrostatic environments around the N, Al, and P nuclei are also confirmed by the calculated natural charges. It should be noted that the positively charged Al atoms on the cages turn out to be the available sites for adsorption of H2 molecules. 相似文献