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91.
Synthesis and photochemistry of several title compounds 1-3 containing multiple chromophoric systems are described. The Diels-Alder reactions of 2,6,6-trimethylcyclohexa-2,4-dienone (5) with acetylenes 6a-d provided the adducts 7a-d, which upon hydrolysis furnished the desired bicyclo[2.2.2]octenediones 1a-d. Oximes 2a-d were prepared from diones 1a-d by treatment with hydroxylamine hydrochloride in pyridine. 5-Methylenebicyclo[2.2.2]oct-7-en-2-ones 3a-d were obtained via chemoselective Wittig reaction of the corresponding diones 1a-d. Bicyclo[2.2.2]octenediones 1a-c underwent chemoselective oxa-di-pi-methane rearrangement under sensitized conditions and suffered formal ketene extrusion upon direct irradiation. Direct irradiation of 1d afforded 11d via formal ketene extrusion but under sensitization it remained unchanged. Oximes 2a-d suffered ketene extrusion upon direct irradiation and E/Z isomerization under sensitized conditions. On the other hand, 5-methylenebicyclo[2.2.2]oct-7-en-2-ones 3a-d generally underwent 1,3-acyl shift. The plausible courses of all these photochemical processes are discussed. 相似文献
92.
Solvent water tapes in two hydrates of μ‐oxo‐bis[bis(2,2′‐bipyridine‐κ2N,N′)(sulfato‐κO)iron(III)]
O. O. E. Onawumi O. O. P. Faboya O. A. Odunola T. K. Prasad M. V. Rajasekharan 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(10):m480-m483
The title compound, [Fe2O(SO4)2(C10H8N2)4], crystallizes as two different hydrates, viz. 11H2O, (I), and 15H2O, (II). The complex is binuclear, in which the two FeIII atoms are coordinated in an octahedral geometry to four N atoms from the two bipyridine ligands, to one O atom from the sulfate ion and to an oxide ion on a twofold axis, which acts as a bridge between the symmetry‐related units. The Fe⋯Fe separation is 3.556 (4) Å and the Fe—O—Fe angle is 161.6 (2)° in (I); the corresponding values are 3.544 (1) Å and 165.8 (2)° in (II). In (II), one of the O atoms of the sulfate ion is disordered over two positions. In both compounds, the solvent water molecules form slightly different one‐dimensional hydrogen‐bonded networks which pass along the c axis of the unit cell. In (I), three solvent water molecules and, in (II), one solvent water molecule, are situated on the twofold axis. In both (I) and (II), the central O atom of the metal complex lies on a twofold axis. 相似文献
93.
The interaction between polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS) after the procedure of addition of the surfactant to polymer and the reverse procedure of addition of polymer to SDS micelles has been studied by tensiometric, conductometric, and microcalorimetric methods. The results have been analyzed and correlated with reference to SDS interfacial adsorption, association, and binding to PVP. Two aggregation states of SDS in presence of PVP have been found. The enthalpies of formation of SDS aggregates/micelles and their binding to the polymer have been evaluated. The interaction of PVP with SDS at concentrations below its critical micellar concentration (CMC) and above have evidenced distinctions. The forward addition protocol (FAP, SDS addition to PVP) and reverse addition protocol (RAP, PVP addition to SDS) have shown similarities and differences. Electrokinetic measurements have evidenced the interacted (SDS–PVP) colloidal products to possess negative zeta potential in the range of −39 to −65 mV. The hydrodynamic diameters of the PVP–SDS dispersion obtained from DLS measurements have ranged between 60 and 160 nm. Both zeta potential and hydrodynamic diameter have depended on [SDS] showing a maximum for the former at twice the critical micellar concentration of SDS. 相似文献
94.
Suraj N. Bhadani Yugal K. Prasad Swapna Kundu 《Journal of polymer science. Part A, Polymer chemistry》1980,18(5):1459-1469
The electrochemical and chemical polymerization of acrylamide (AA) has been studied. The electrolysis of the monomer in N,N-dimethylformamide (DMF) containing (C4H9)4NClO4 as the supporting electrolyte leads to polymer formation in both anode and cathode compartments. The cathodic polymer dissolves in the reaction mixture and the anodic polymer precipitates during the course of polymerization. A plausible mechanism for the anodic and cathodic initiation reaction has been given. The chemical polymerization of acrylamide that has been initiated by HClO4 is analogous to its anodic polymerization. The polymer yield increases with an increase in concentration of the monomer and HClO4. Raising the reaction temperature also enhances the polymerization rate. The overall apparent activation energy of the polymerization was determined to be ca. 19 kcal/mole. The copolymerization of acrylamide was carried out with methyl methacrylate (MMA) in a solution of HClO4 in DMF. The reactivity ratios are r1 (AA) = 0.25 and r2 = 2.50. The polymerization with HClO4 appears to be by a free radical mechanism. When the polymerization of acrylamide is carried out with HClO4 in H2O, a crosslinked water-insoluble gel formation takes place. 相似文献
95.
Abstract— The order of inhibition of the photooxidation of chlorophyll a in ethanol and ethanol-benzene is as follows: β-carotene, α-tocopherol, benzoquinone, DABCO, menadione, cholesterol and KI. The quenching of singlet oxygen by β-carotene occurs by a collisional quenching mechanism with a diffusion-controlled rate of 1.7 × 1010 M -1 s-1 . Photodecomposition of Chi a is faster in ethanol-D2 O than in ethanol-H2 O. Photoirradiation (660 nm) of the peridinin-Chl a -protein complex, a photosynthetic light-harvesting pigment isolated from marine dinoflagellates, did not show any photo-decomposition of its Chi a in H2 O or D2 O, even after an extended period (12 h) of irradiation. However, the carotenoid, peridinin, in the photosynthetic antenna pigment was photobleached (ca. 10%) during the irradiation. We conclude that the singlet oxygen formed as a result of the Chi photosensitization is immediately quenched by the low-lying triplet state of four peridinin molecules (per Chl a ) bound within the same protein crevice. The carotenoid thus effectively protects Chl a from photodynamic damage, providing a direct proof for the protective role of carotenoids in the photosynthetic pigment complex. 相似文献
96.
97.
John Bentley Dr. Salil Desai Dr. Bishnu Prasad Bastakoti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9241-9252
Tungsten oxide (WO3) has received ever more attention and has been highly researched over the last decade due to its being a low-cost transition metal semiconductor with tunable, yet widely stable, band gaps. This minireview briefly highlights the challenges in the design and synthesis of porous WO3 including methods, precursors, solvent effects, crystal phases, and surface activities of the porous WO3 base material. These topics are explored while also drawing a connection of how the morphology and crystal phase affect the band gap. The shifts in band gap not only impact the optical properties of tungsten but also allow tuning to operate on different energy levels, which makes WO3 highly desirable in many applications such as supercapacitors, batteries, solar cells, catalysts, sensors, smart windows, and bioapplications. 相似文献
98.
Deshabrata Roy Mahapatra Sankar Kumar Roy Mahendra Prasad Biswal 《Applied Mathematical Modelling》2013
In this paper a multi choice stochastic transportation problem is considered where the supply and demand parameters of the constraints follow extreme value distribution. Some of the cost coefficients of the objective function are multi-choice type. At first all the probabilistic constraints are transformed into deterministic constraints. Further using the binary variables, multi-choice type cost coefficients are handled. Then the transformed problem is considered as a deterministic multi-choice transportation problem. Finally, a numerical example is presented to illustrate the solution procedure. 相似文献
99.
100.
B. B. Prasad 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11-12):1493-1505
Polarographic studies on aqueous solutions of the redox polyelectrolyte poly-m-xylylviologen dibromide were carried out in the 1.70–7.90 pH range. The compound revealed two well-defined, diffusion-controlled cathodic waves with half-wave potentials of -0.482 and -0.906 V vs SCE. The electrode processes were found to be irreversible and independent of pH. The system did not conform to the protonation equilibrium (PXVBr2 + H+?PXVBr2H+) in contrast to its ortho and para isomeric compounds. A suitable mechanism for the reduction processes is suggested. 相似文献