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Organic sulfonyl fluorides are of interest owing to their insecticidal, germicidal and enzyme inhibitory properties. In the current work, synthesis of p-toluenesufonyl fluoride was accomplished by reacting p-toluenesulfonyl chloride with solid potassium fluoride using PEG-400 as a catalyst under solid-liquid phase transfer catalysis (S-L PTC) at 30 °C. p-Toluenesulfonyl fluoride is used as peroxygen bleach activator. It also finds use in the treatment of Alzheimer's disease. The mechanism is based on homogeneous solubilization of solid. PEG forms a complex with metal cation which associates with the nucleophile and it participates in SN2 type reactions. The reaction is intrinsically kinetically controlled. A complete theoretical analysis is done to determine both the rate constant and equilibrium constant from the same set of data. The activation energy and Gibbs free energy are also calculated. 相似文献
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R. T. Chitnis S. G. Talnikar V. A. Thakur A. H. Paranjape 《Journal of Radioanalytical and Nuclear Chemistry》1979,49(1):63-70
The method for plutonium determination based on secondary controlled-potential coulometry, as described by SHULTS, is applied
for analysis in the range of 0.1–5 mg plutonium. The method involves the oxidation of plutonium to Pu(VI) with perchloric
acid followed by its reduction by an internally generated ferrous mediator. This is a two step procedure, involving the reduction
of Pu(VI) and Fe(III) to a mixture of Pu(III) and Fe(II), followed by the oxidation of Pu(III) and Fe(II) to Pu(IV) and Fe(III),
respectively. The net results is the reduction of Pu(VI) to Pu(IV), measured as the difference between the currents consumed
during the reduction and oxidation steps. The original method of SHULTS involves 10–25 mg plutonium for each determination.
Since the present method is intended for the analysis of smaller amounts of plutonium, the oxidation procedure described in
the original version had to be modified. The method is found to work satisfactorily with a precision better than 0.1% at 5
mg level and 1.2% for 0.1 mg plutonium. 相似文献
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We consider the one dimensional, periodic spin chain with N sites, similar to the one studied by Haldane [1], however in the opposite limit of very large anisotropy and small nearest neighbour, anti-ferromagnetic exchange coupling between the spins, which are of large magnitude s. For a chain with an even number of sites we show that actually the ground state is non-degenerate and given by a superposition of the two Neél states, due to quantum spin tunnelling. With an odd number of sites, the Neél state must necessarily contain a soliton. The position of the soliton is arbitrary thus the ground state is N-fold degenerate. This set of states reorganizes into a band. We show that this occurs at order 2s in perturbation theory. The ground state is non-degenerate for integer spin, but degenerate for half-odd integer spin as is required by Kramers' theorem [18]. 相似文献
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If general relativity (GR) describes the expansion of the Universe, the observed cosmic acceleration implies the existence of a "dark energy." However, while the Universe is on average homogeneous on large scales, it is inhomogeneous on smaller scales. While GR governs the dynamics of the inhomogeneous Universe, the averaged homogeneous Universe obeys modified Einstein equations. Can such modifications alone explain the acceleration? For a simple generic model with realistic initial conditions, we show the answer to be "no." Averaging effects negligibly influence the cosmological dynamics. 相似文献