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991.
992.
Sayanti Chatterjee Tapan Kanti Paine 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(32):9470-9474
Many iron‐containing enzymes involve metal–oxygen oxidants to carry out O2‐dependent transformation reactions. However, the selective oxidation of C H and CC bonds by biomimetic complexes using O2 remains a major challenge in bioinspired catalysis. The reactivity of iron–oxygen oxidants generated from an FeII–benzilate complex of a facial N3 ligand were thus investigated. The complex reacted with O2 to form a nucleophilic oxidant, whereas an electrophilic oxidant, intercepted by external substrates, was generated in the presence of a Lewis acid. Based on the mechanistic studies, a nucleophilic FeII–hydroperoxo species is proposed to form from the benzilate complex, which undergoes heterolytic O O bond cleavage in the presence of a Lewis acid to generate an FeIV–oxo–hydroxo oxidant. The electrophilic iron–oxygen oxidant selectively oxidizes sulfides to sulfoxides, alkenes to cis‐diols, and it hydroxylates the C H bonds of alkanes, including that of cyclohexane. 相似文献
993.
Polystyrene nanoparticles (nPS) in the range of 10–100 nm with spherical shape were synthesized by oil/water (o/w) microemulsion process. In this process ammonium persulfate (APS) as an initiator, sodium dodecyl sulphate as a surfactant and n‐pentanol as cosurfactant were used. Isolated nPS was characterized by FTIR and 1H NMR spectroscopy. DSC studies of nPS showed higher Tg as compared to bulk PS. The effect of lower weight percentage (wt%) of nPS on the mechanical, rheological, and thermal properties of PP was investigated. The blends were prepared individually on brabender plastograph by incorporating nPS of ～60 nm with different wt% of loading (i.e., 0.10–0.5%). It was shown from the experimental results that thermal, rheological, and mechanical properties were increased as the polymer particles blended with PP. Blends with 0.25 wt% loading of nPS exhibit better properties compared with that of other wt% loadings. The improvements in properties were due to the close packing of PP chains as recorded by improvement in crystallinity of PP with the addition of nPS as shown by SEM. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
994.
The present paper relates to the atomized process for the synthesis of nanoparticles of polystyrene (nPS), polyacrylonitrile (nPAN), and poly(styrene/acrylonitrile) (nP[SAN]) copolymers with different monomer ratios and with controlled particle size in the range from 10 to 100 nm. In this process, ammonium persulfate (APS) was used as thermal initiator, along with sodium dodecyl sulfate (SDS) and n‐pentanol (n‐Pt) as surfactant and cosurfactant, respectively. The effect of different parameters on particle size and morphology of polymer nanoparticles has been reported in this work. Transmission electron microscopy (TEM) study showed the changes in particle morphology of pure nPS, nPAN, and their copolymers. Structural property and interaction of PS and PAN were investigated by Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD). The effect of particle size and crystalline structure on glass transition temperature (Tg) and melting temperature (Tm) were also investigated by differential scanning calorimetry (DSC). Thermal stability of polymer nanoparticles was studied by thermo gravimetric analyzer (TGA) and it showed that the copolymer nanoparticles of nP[SAN] were more stable with minimum weight loss (WL). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
995.
A theoretical model based on physical, chemical, and biochemical mechanisms has been presented to evaluate the yields of DNA strand breaks (single and double) as a function of linear energy transfer (LET ) or ?dE/dx. Energetic heavy charged particles are considered explicitly to provide a general theory for low- as well as for high-LET radiation. There are three main features of the calculation: (a) track structure considerations for the energy deposition pattern, (b) three-dimensional structure of DNA molecules to provide information on the exact location of damage, and (c) a Monte-Carlo scheme to simulate the diffusion processes of water radicals. To avoid the complexities of a cellular medium, an aqueous solution of DNA is considered in the calculation. When the results of the calculations are compared with experimental measurements of the yields of strand breaks in mammalian DNA (exposed in a cellular complex), reasonable agreement is obtained. However, only those experimental data have been compared where there were no enzyme repair processes. The method of calculation has also been extended to study breaks in higher-order structures of DNA molecules such as chromatin. Specific limitations of the present model have been pointed out for making further improvements. 相似文献
996.
Pyridyl-2-azo-chromotropic acid (disodium salt) is proposed as a new reagent for the determination of nickel and cobalt in the presence of many ions and for their simultaneous determination in the absence of cyanide and EDTA. The wavelengths of maximum absorption for the nickel and cobalt complexes are 570 and 640 mmu respectively. Beer's law is obeyed by the complex systems from 0.125-0.8 ppm of nickel and 0.16-1.2 ppm of cobalt. The optimum concentration ranges are 0.25-0.8 ppm for nickel and 0.16-1.2 ppm for cobalt and the relative error is 2.7 %. The molar absorptivities for the complexes of nickel and cobalt are 40,720 and 33,600, while the dissociation constants at pH 7.5 and 22 degrees are of the order of 10(-12) and 10(-13), respectively. The metal to reagent ratio is 1:3. 相似文献
997.
Calculations have been made for Hafner's hydrocarbons using a refined form of the Hückel MO method in which dependence of ‘Coulomb’ integral on charge density and ‘resonance’ integral on bondlength via bond order have been allowed for in a selfconsistent manner. Bondlengths, π → πk̊ spectra, stability and reactivity of the molecules as given by the refined MO method have been compared with the simple Hückel MO method results. 相似文献
998.
Vaibhav Kulshrestha Uma Chatterjee Saroj Sharma B. S. Makwana P. D. Maru 《Macromolecular Symposia》2015,357(1):194-199
999.
1000.
Banerjee P Chatterjee S Pramanik S Hossain SU Bhattacharya S Bhattacharya SC 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,66(4-5):1110-1114
Spectroscopic studies of newly synthesized bioactive compound 2-(2-bromo-ethyl)-6-nitro-benzo[de]isoquinolene-1,3-dione (BNBIO) have been carried out in polar aprotic solvent, viz. acetonitrile, tetrahydrofuran, 1,4-dioxan, ethylene glycol, dimethyl formamide, and polar protic solvent, viz. methanol, ethanol, propanol, water. Variation in absorbance of BNBIO in water-methanol, water-ethanol and water-propanol mixtures at their different compositions have been observed. Absorption behaviour of the dye has been studied in poly(oxyethylene) nonylphenol surfactants Igepal CO 630, Igepal CO 720 and Igepal CO 890 containing same hydrophobic tail and different numbers of poly(oxyethylene) groups. Experimental results of the BNBIO nonionic micelles have been explained in terms of 1:1 electron donor-acceptor (EDA) complexation and the complexation equilibrium becomes suppressed with increasing number of poly(oxyethylene) residue on the Igepal surfactant. Variation in binding constant of dye-micelle complexation has been rationalized considering a competitive equilibrium process between the BNBIO-water interactions. 相似文献