排序方式: 共有62条查询结果,搜索用时 281 毫秒
31.
32.
Ali Ramazani Vahid Azizkhani Farideh Gouranlou 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):719-724
Protonation of the highly reactive 1:1 intermediates, produced in the reaction between tributylphosphine and alkyl acetylenecarboxylates by 2-hydroxybenzaldehyde derivatives, leads to vinyltributylphosphonium salts, which undergo a Michael addition reaction with conjugate base to produce corresponding phosphorus ylides. The phosphorus ylides convert to electron-poor O-vinyl ether derivatives under reaction conditions. 相似文献
33.
Mansoureh Zahedi-Tabrizi Farideh Badalkhani-Khamseh 《Journal of the Iranian Chemical Society》2013,10(4):685-694
A density functional theory (DFT) study-based method B3LYP/6-311++G** was carried out to investigate the methyl groups substitution effect on the structure and the strength of intramolecular hydrogen bonding in naphthazarin (NZ) (5,8-dihydroxy-1,4-naphthoquinone). The full geometry optimization of molecular structures, the difference between the energies of hydrogen-bonded and non-hydrogen-bonded rotamers, and the proton chemical shift of the hydroxyl groups in NZ and its methyl substituents obtained at the B3LYP/6-311++G** level. The vibrational frequencies of all samples and their deuterated analogues were calculated at the same theoretical level. The 1H chemical shifts for NZ and its methyl substituents were computed at the B3LYP/6-311++G** level using the gauge-including atomic orbital method. Furthermore, in order to investigate the changes in bond order, electron density, electron delocalization, and steric effects caused by methyl substituents, natural bond orbital analysis were carried out at the B3LYP/6-311++G** level. After comparing these effective parameters in methyl substituents with those of their parent, NZ, we concluded that, in general, intramolecular hydrogen bonding strength increases by substituting methyl groups in the different positions of NZ. 相似文献
34.
The operational Tau method, a well known method for solving functional equations is employed to approximate the solution of
nonlinear fractional integro-differential equations. The fractional derivatives are described in the Caputo sense. The unique
solvability of the linear Tau algebraic system is discussed. In addition, we provide a rigorous convergence analysis for the
Legendre Tau method which indicate that the proposed method converges exponentially provided that the data in the given FIDE
are smooth. To do so, Sobolev inequality with some properties of Banach algebras are considered. Some numerical results are
given to clarify the efficiency of the method. 相似文献
35.
Hakimian Farideh Shayesteh Mohammad Reza Moslemi Mohammad Reza 《Optical and Quantum Electronics》2020,52(1):1-18
Optical and Quantum Electronics - We review a novel approach to the light scattering by small layered particles in the electrostatic limit when the particle is considered to be in the uniform... 相似文献
36.
37.
Farideh Abbasi Shahram Mehdipour‐Ataei Zahra Tabatabaei‐Yazdi Samal Babanzadeh Ebrahim Abouzari‐Lotf 《先进技术聚合物》2017,28(3):404-410
A new poly(sulfone ether imide) was prepared, and related nanocomposites were produced through introduction of sepiolite nanoparticles into the matrix of polymer. Inherent viscosity, thermal and mechanical features of pristine poly(sulfone ether imide), and nanocomposite samples were evaluated and compared. The crystallinity was also investigated. Dispersion and distribution behaviors of nanocomposite samples and cross‐sectional morphology of nanocomposite films were also studied. Also, the optimized amounts of sepiolite nanoparticles in the matrix of polymer were determined by microscopic techniques (scanning electron microscope and transmission electron microscope). By introduction of 3 wt% of sepiolite, superior thermal and mechanical properties were observed. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
38.
A "green" highly selective oxidation of organic sulfides to the corresponding sulfoxides was developed using hydrogen peroxide and glacial acetic acid under transition metal-free and mild conditions. The oxidation procedure is very simple and the products are easily isolated in excellent yields (90-99%). 相似文献
39.
Jamshid Soltani-Nabipour Khorshidi Abdollah Sadeghi Farideh 《Physics of Particles and Nuclei Letters》2019,16(6):789-795
Physics of Particles and Nuclei Letters - Background: From the health physics perspective, radon gas is one of the most dangerous gases in residential and business environments. According to the... 相似文献
40.
Protonation of the highly reactive 1:1 intermediate produced in the reaction between alkyl or aryl isocyanides and electron-deficient acetylenic esters with 3,6-dihydroxypyridazine, leads to a vinylisonitrilium cation, which undergoes an addition reaction with the conjugate base of the 3,6-dihydroxypyridazine to produce dialkyl 3-(alkyl or arylamino)-5,8-dioxo-5,8-dihydro-1H-pyrazolo[1,2-a]pyridazine-1,2-dicarboxylates in good yields at room temperature. 相似文献