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排序方式: 共有407条查询结果,搜索用时 15 毫秒
51.
Ly HV Forster TD Maley D Parvez M Roesler R 《Chemical communications (Cambridge, England)》2005,(35):4468-4470
A heterocyclic cyclopentadienyl analog containing only one carbon atom in the ring was prepared and a polymeric lithiocene and a monomeric zincocene containing this novel ligand have been isolated and crystallographically characterized. 相似文献
52.
The salts [(C2H5)3NH]2[M4(SC6H5)10] (M = Zn, Cd) can be prepared by the electrochemical oxidation of the metal in an acetonitrile solution of triethylamine and benzenethiol. An X-ray crystal structure determination shows that the anion consists of a tetrahedron of metal atoms, each carrying a terminal -SC6H5 ligand, and connected to the three other metal atoms by bridging > SC6H5 groups. The results are compared with those for similar compounds reported in the literature. 相似文献
53.
In this paper we investigate the exact traveling wave solutions of the fifth-order Kaup-Kuperschmidt equation. The bifurcation and exact solutions of a general first-order nonlinear equation are investigated firstly. With the help of Maple and by using the bifurcation and exact solutions of two derived subequations, we obtain two families of solitary wave solutions and two families of periodic wave solutions of the KK equation. The relationship of the two subequations and the two known rst integrals are analyzed. 相似文献
54.
J. Zafar H. Zafar K. Masood A. A. P. Gibson 《International Journal of Infrared and Millimeter Waves》2008,29(12):1205-1214
High power line source emitter assembly was coupled to a twin symmetric H-plane slab loaded accelerating structure for beam
acceleration. Closed form field analysis of the accelerating structure that includes guideline information regarding modal
hierarchy, mode nomenclature, propagation plane, cut-off plane and dispersion relations is presented. Furthermore it was confirmed
that by using symmetrically loaded dielectric accelerating structures with one rotated through 90° results in exerting a uniform
acceleration impact on a travelling beam passing through the structure. 相似文献
55.
56.
Summyia Masood Rehana Saeed Maria Ashfaq Afshan Irfan 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(12):2102-2107
Viscosities of sodium chloride in concentration range 1 × 10?2 to 9 × 10?2 ± 0.001 mol dm?3, have been determined in aqueous and aqueous maltose systems (1.0 to 9.0 wt %) at different temperatures (298 to 323 K). The viscosity data have been analyzed by using Jones-Dole equation and the derived parameters A and B coefficients were also calculated. The data obtained from viscometric studies has been used to investigate the ion-solvent interaction and ion-ion interaction. Thermal effects on the ionic interactions were also examined under the light of transition state theory. 相似文献
57.
S. Masood W. Rehman Z. Khan H. Arshad S. Begum A. Perveen 《Journal of Structural Chemistry》2018,59(5):1148-1157
Densities of acefylline piperazine (AP) in aqueous, aqueous methanol, and aqueous ethylene glycol (10% v/v) systems are determined in the concentration range 0.04-0.14±0.001 mol/dm3 at different temperatures (298.15-318.15 K) with the interval of 5 K. The apparent molar volume (φv), the partial molar volume \((\phi_v^0)\), and the ion-ion interaction parameter (Sv) are calculated using the Masson equation. Partial molar expansibilities \((\phi_E^0)\), which indicate the presence or absence of the caging or packing effect, are also evaluated and discussed. The results are interpreted in terms of solute-solvent and solute-solute interactions of AP in aqueous, aqueous methanol, and aqueous ethylene glycol systems. The structure-breaking and structure-making properties of AP are inferred by the sign of Hepler′s criterion \((\partial^2\phi_v^0/\partial{T}^2)_p\), i.e. the second derivative of the partial molar volume with respect to the temperature at the constant pressure. 相似文献
58.
Waseeq Ahmad Siddiqui Saeed Ahmad Hamid Latif Siddiqui Masood Parvez 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(7):o367-o371
The structures of 2‐[(2,3‐dimethylphenyl)carbamoyl]benzenesulfonamide, 2‐[(3,4‐dimethylphenyl)carbamoyl]benzenesulfonamide and 2‐[(2,6‐dimethylphenyl)carbamoyl]benzenesulfonamide, all C15H16N2O3S, are stabilized by extensive intra‐ and intermolecular hydrogen bonds. In all three structures, the sulfonamide and carbamoyl groups are involved in hydrogen bonding. In the 2,3‐dimethyl and 2,6‐dimethyl derivatives, dimeric units and chains of molecules are formed parallel to the c axis. In the 3,4‐dimethyl derivative, the hydrogen bonding creates tetrameric units, resulting in macrocyclic R44(22) rings that form sheets in the ab plane. The three analogues are closely related to the fenamate class of nonsteroidal anti‐inflammatory drugs. 相似文献
59.
Ly HV Konu J Parvez M Roesler R 《Dalton transactions (Cambridge, England : 2003)》2008,(26):3454-3460
Two heterocyclic cyclopentadienyl analogs with a CB2N2 skeleton, 4-methyl-1,2,3,5-tetraphenyl-1,2-diaza-3,5-diborolidine and 4-methyl-3,5-dimethylamino-1,2-diphenyl-1,2-diaza-3,5-diborolidine were prepared through cyclocondensation of the corresponding 1,1-bis(organochloroboryl)ethane with 1,2-diphenylhydrazine. The former diazadiborolidine featured a cyclopentadiene-like structure with short B-N bonds and a planar ring framework, while in the latter the B-N bonds were noticeably longer and the ring framework was considerably folded as a result of the interaction between boron and the electron donating NMe2 groups. The dimethylamino substituted diazadiborolidine could not be deprotonated due to the reduced acidity of the ring proton, however, the B-phenylated analog was easily deprotonated and the lithium, sodium and potassium 1,2-diaza-3,5-diborolyls were isolated and structurally characterized. The solid state structures of the lithium and sodium salts were similar, with an eta(1)-coordinated pi ligand and three THF molecules completing the coordination sphere of the metal. The potassium salt featured a highly unusual mono-dimensional polymeric structure with the metal pi-coordinated by the CB2N2 ligand and two of the phenyl groups on boron and nitrogen, and sigma-coordinated by one THF molecule. 相似文献
60.
Several representative acetylenic sulfones were immobilized on a polymer support derived from Merrifield resin by means of ester linkers that were used to couple free carboxylic acid groups on the solid support with benzylic hydroxyl functions on the arylsulfonyl moieties of the acetylenes. Several examples of reversed ester linkers, using Merrifield resin directly, were also successfully prepared. The 1,3-dipolar cycloadditions of the solid-supported acetylenic sulfones were investigated with a series of 1,3-dipoles, including benzyl azide, ethyl diazoacetate, diazomethane, as well as representative nitrile oxides, nitrile imines, nitrile ylides, nitrones, azomethine imines, azomethine ylides, munchnones, and sydnones. In general, analogous cycloadditions were also performed with acetylenic sulfones in solution phase for comparison. The cycloadditions typically afforded good to excellent yields of the desired products in both solution and solid phase, although the latter reactions sometimes required more vigorous conditions. Except in the case of benzyl azide and diazo compounds, where mixtures of regioisomers were obtained, the other 1,3-dipoles reacted with high regioselectivity and afforded essentially unique regioisomers. Cleavage of the products from the resin was smoothly effected by alkaline hydrolysis, while several attempts at reductive desulfonylation with sodium amalgam or samarium diiodide-HMPA resulted in N-O or C-O scission, in addition to cleavage from the polymer. The method provides access to a number of important classes of heterocycles, including variously substituted and functionalized triazoles, pyrazoles, 1,2-oxazoles, pyrroles, as well as their dihydro and bicyclic analogues. The success of the cycloadditions on polymer supports paves the way to future investigations of sequential transformations leading to libraries of useful heterocycles. 相似文献