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971.
One-pot efficient synthesis of functionalized 5,6-dihydropyran-2-ones has been delineated by reacting 2H-pyran-2-ones and acetol in the presence of a base at room temperature. The formation of 5,6-dihydropyran-2-ones revealed that the reaction proceeded in a unique ‘ring transformation-rearrangement’ sequence. 相似文献
972.
Reaction of zinc(II) thiocyanate with pyrazine, pyrimidine, pyridazine, and pyridine leads to the formation of new zinc(II) thiocyanato coordination compounds. In bis(isothiocyanato‐N)‐bis(μ2‐pyrazine‐N,N) zinc(II) ( 1 ) and bis(isothiocyanato‐N)‐bis(μ2‐pyrimidine‐N,N) zinc(II) ( 2 ) the zinc atoms are coordinated by four nitrogen atoms of the diazine ligands and two nitrogen atoms of the isothiocyanato anions within slightly distorted octahedra. The zinc atoms are connected by the diazine ligands into layers, which are further linked by weak intermolecular S ··· S interactions in 1 and by weak intermolecular C–H ··· S hydrogen bonding in 2 . In bis(isothiocyanato‐N)‐bis(pyridazine‐N) ( 3 ) discrete complexes are found, in which the zinc atoms are coordinated by two nitrogen atoms of the isothiocyanato ligands and two nitrogen atoms of the pyridazine ligands. The crystal structure of bis(isothiocyanato‐N)‐tetrakis(pyridine‐N) ( 4 ) is known and consists of discrete complexes, in which the zinc atoms are octahedrally coordinated by two thiocyanato anions and four pyridine molecules. Investigations using simultaneous differential thermoanalysis and thermogravimetry, X‐ray powder diffraction and IR spectroscopy prove that on heating, the ligand‐rich compounds 1 , 2 , and 3 decompose without the formation of ligand‐deficient intermediate phases. In contrast, compound 4 looses the pyridine ligands in two different steps, leading to the formation of the literature known ligand‐deficient compound bis(isothiocyanato‐N)‐bis(pyridine‐N) ( 5 ) as an intermediate. The crystal structure of compound 5 consists of tetrahedrally coordinated zinc atoms which are surrounded by two isothiocyanato anions and two pyridine ligands. The structures and the thermal reactivity are discussed and compared with this of related transition metal isothiocyanates with pyrazine, pyrimidine, pyridazine, and pyridine. 相似文献
973.
RF-excited fast axial flow CO2 lasers in kilowatt regime are presently being used for various new scientific applications in addition to laser material
processing because of its versatility and superior beam quality. We have indigenously developed a compact 2 kW RF-excited
fast axial flow CO2 laser with moderate beam quality. In this paper the key design features of the laser and the associated high power capacitively
coupled RF excitation technique are discussed in detail. Operational characteristics of this system are described along with
the experimental findings. 相似文献
974.
In this paper we present an expression relating the cohesive energy (E coh in kcal/mol) of AIIIBV and AIIBVI semiconductors with the product of ionic charges (Z 1 Z 2) and nearest-neighbour distance d (Å). The cohesive energy values of these solids exhibit a linear relationship when plotted on a log-log scale against the nearest-neighbour distance d (Å), but fall on different straight lines according to the ionic charge product of the solids. A good agreement has been found between the experimental and calculated values of the cohesive energy of AIIIBV and AIIBVI semiconductors. 相似文献
975.
We present a comprehensive phenomenological analysis of the allowed hybrid textures of neutrinos. Out of a total of sixty hybrid textures with one equality between the elements of neutrino mass matrix and one texture zero only twenty three are found to be viable at 99% C.L. whereas the earlier analysis found fifty four to be viable. We examine the phenomenological implications of the allowed hybrid textures including Majorana type CP-violating phases, 1–3 mixing angle and Dirac type CP-violating phase, δ. We, also, obtain lower bound on effective Majorana mass for all the allowed hybrid textures. 相似文献
976.
Study of relativistic effects in the interaction of a spin-1/2 electric charge in the radial field of a spin less point like
dyon has been undertaken using Dirac’s relativistic equation. Angular momentum and energy eigen values have been obtained.
The deviations of the results from those of hydrogen atom like systems have been discussed. 相似文献
977.
S. Verma H. Gupta O. Alam P. Mullick N. Siddiqui S. A. Khan 《Journal of Applied Spectroscopy》2009,76(6):876-882
An attempt was made to develop and validate a novel, simple, cost effective, accurate, and reproducible UV-spectrophotometric
method to estimate mycophenolate mofetil in bulk and pharmaceutical formulations. Mycophenolate mofetil was estimated at 250
nm in 0.1N hydrochloric acid (pH 1.2) and in acetate buffer (pH 4.5). Beer’s law was obeyed in the concentration range of
5–40 μg/ml in hydrochloric acid and in the acetate buffer medium. The methods were tested and validated for various parameters
according to ICH guidelines. The proposed methods were successfully applied for the determination of mycophenolate mofetil
in pharmaceutical formulations (tablets and capsules). The results demonstrate that the procedure is accurate, precise, and
reproducible (relative standard deviation <2%) while being simple, cheap, and less time-consuming, and hence can be suitably
applied for the estimation of mycophenolate mofetil in different dosage forms and for dissolution studies. 相似文献
978.
A series of novel 2,2′‐(N,N′‐diarylamino)‐4,4′‐diaryl‐5,5′‐arylidene‐bisthiazoles 2 were rapidly and smoothly prepared in good yields by using non conventional techniques i.e. microwave or ultrasonic irradiation, through indium trichloride catalyzed electrophilic substitution reaction of 2‐(N‐arylamino)‐4‐arylthiazoles 1 with various arylaldehydes. All the synthesized compounds were characterized on the basis of their elemental analyses and spectral data (IR, PMR and Mass). The synthesized compounds were also evaluated for their insecticidal activity against Helicoverpa armigera and gave promising results. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:224–231, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20537 相似文献
979.
Magnetic moments of heavy charmed baryons with J
P = 3/2+ are predicted employing the concept of effective quark mass and screened charge of quark. We also extend our scheme to predict
the 3/2+
? \rightarrow 1/2+ transition magnetic moments. A comparison of our results with the predictions obtained in recent models is presented. 相似文献
980.
We have studied the high-pressure phase stability of LaF3 using full-potential linear augmented plane wave method. We have shown that experimentally observed orthorhombic phase is less stable compared to the theoretically predicted tetragonal structure above 25 GPa pressure. The structural transition is mainly due to the steric repulsion of ions and electrons to higher pressures. 相似文献