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221.
The charge–transfer (CT) complex of donor antipyrine with Π‐acceptor 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) has been investigated spectrophotometrically in different halocarbon and acetonitrile solvents. The results indicated immediate formation of an electron donor–acceptor complex (DA), which is followed by two relatively slow consecutive reactions. The pseudo–first‐order rate constants for the formation of the ionic intermediate and the final product at various temperatures were evaluated from the absorbance–time data. The activation parameters, viz. activation energy, enthalpy, entropy, and free energy of activation, were computed from temperature dependence of rate constants. The stoichiometry of the complex was found to be 1:1 by Job's method of continuous variation. The formation constants of the resulting DA complexes were determined by the Benesi–Hildebrand equation at four different temperatures. The enthalpies and entropies of the complex formation reactions have been obtained by temperature dependence of the formation constants using Van't Hoff equation. The results indicate that DDQ complexes of antipyrine in all solvents are enthalpy stabilized but entropy destabilized. Both the kinetics of the interaction and the formation constants of the complexes are dependent upon the polarity of the solvents. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 81–91, 2013 相似文献
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Farhad Shirini Abdollah Fallah-Shojaei Masoumeh Abedini Laleh Samavi 《Journal of the Iranian Chemical Society》2016,13(9):1699-1712
P4VPy–CuO nanoparticles were synthesized using ultrasound irradiations. Relevant properties of the synthesized nanoparticles were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. After identification, the prepared reagent was used for the promotion of different types of protection reactions of alcohols, phenols and amines. Easy workup, short reaction times, excellent yields, relatively low cost and reusability of the catalyst are the striking features of the reported methods. 相似文献
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A novel magnetic hybrid system containing nano‐magnetic Fe2O3 hollow spheres, silica shell, [pmim]Cl ionic liquid and silver nanoparticles was synthesized and characterized. The silver nanoparticles were prepared via biosynthesis using Achillea millefolium flower as reducing and stabilizing agent. The hybrid system was successfully used as an efficient and reusable catalyst for promoting green ultrasonic‐assisted A3 and KA2 coupling reactions as well as benzo[b]furan synthesis. It was found that decoration of the magnetic core with non‐magnetic moieties decreased the maximum saturation magnetization. However, the catalyst was still superparamagnetic and could be simply separated from the reaction mixture using an external magnet. The heterogeneous nature of the catalyst was also confirmed by studying its reusability and stability and the leaching of silver. Use of aqueous media, high yields, short reaction times, broad substrate tolerance and low required amount of catalyst are the merits of this protocol. 相似文献
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Mohammad?Mehdi?Kashani-MotlaghEmail author Masoumeh?Karami?Mahmoudabad 《Journal of Sol-Gel Science and Technology》2011,59(1):106-110
Our goal in this research was to obtain lead oxide nano-powders by sol–gel method. In this method, lead oxide nano-powders
were synthesized through the reaction of citric acid (C6H7O8·H2O) solution and lead acetate [Pb(C2H3O2)2] solution as stabilizer and precursor, respectively. The effect of different parameters including calcination temperature,
(molar ratio of citric acid to lead acetate) and drying conditions were investigated. The prepared lead oxide nano-powders
were characterized by FT-IR spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy.
The prepared PbO samples consist of the particles in the range of 50–120 nm or the thick plate like structures with thickness
of 53 nm depending on the drying conditions. 相似文献