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排序方式: 共有137条查询结果,搜索用时 15 毫秒
1.
Cory Momany Marvin L. Hackert Jyotsna Sharma Narinder S. Poonia 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(3):343-354
Sodium salicylate (NaSal where Sal=2-hydroxybenzoate), when mixed with dibenzo-24-crown-8 (DB24C8) yields a bimetallic complex [NaSal]2DB24C8 in most polar organic media, while potassium salicylate (KSal) under similar conditions shows a tendency to yield 11 or 21 complexes depending upon medium or synthesis. However, the presence of both NaSal and KSal together results in a unique mixed cation complex of composition NaKSal2DB24C8. This product melts sharply (190-92°C) without decomposition, displays IR spectral characteristics comparable to those of [Na(Sal)]2DB24C8, and is stable in aqueous media as shown by the detectable cation effect on the UV absorption bands of Sal and DB24C8. Single crystal X-ray analysis of NaK(Sal)2DB24C8 reveals that the system represents a co-crystallization complex of individual (KSal)2DB24C8 and (NaSal)2DB24C8 molecules. The crystals are monoclinic,P21/c,a=19.976(2) Å,b=9.031(1) Å,c=25.541(5) Å,=122.065(9)°, Å3,T=298 K,Z=2+2, CuK =1.5418 Å, and 2 (2.5°–100°). FinalR factor for the 3012 observed reflections (F>3) is 0.092. Both the Na2- and K2-molecules possess crystallographic centers of symmetry with one metal and its associated anion on each side of the crown ring. However, the conformations of the crowns are very different in the two molecules, with the K2-crown being nearly planar and the Na2-crown being quite puckered. Four oxygen atoms from the DB24C8 (KO, 2.680–2.908 Å) and three carboxyl oxygen atoms (KO, 2.472–2.708 Å) from separate salicylate ions coordinate with each potassium. Three oxygens from the crown (NaO, 2.536–2.65 Å) and three carboxyl oxygens (NaO, 2.31–2.563 Å) coordinate with each sodium. The salicylate ions lie on opposite sides and nearly perpendicular (77.2°, Na2-molecule; 82.7° K2-molecule) to each crown but coordinate to both of the metal ions within a molecule. The K+K+ and Na+Na+ distances in the respective molecules are 3.95 and 3.34 Å.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82044 (18 pages). 相似文献
2.
A rapid and selective method has been developed for the extraction of Co/II/ with isonitrosobenzoylacetone into chloroform. The effect of various parameters on the extraction coefficient value such as effect of pH, time of equilibration, effect of various cations and anions have been evaluated. The stoichiometry of metal to reagent determined by the method of substoichiometric extraction was found to be 12. It was further supported by the slope ratio method. 相似文献
3.
L. Chandrasekhara Rao H.M. Meshram N. Satish Kumar N. Nageswara Rao N. Jagadeesh Babu 《Tetrahedron letters》2014
A convenient and efficient method is described for the synthesis of alkoxy substituted 2H-chromens by l-proline catalyzed reaction of salicylaldehydes with diketone in alcohol. The method is applicable for various substituted salicylaldehydes and aliphatic as well as benzylic alcohols. 相似文献
4.
B. Madhu Babu Pramod B. ThakurN. Nageswara Rao G. Santosh KumarH.M. Meshram 《Tetrahedron letters》2014
A rapid, efficient, and convenient synthesis of functionalized triarylmethane is described by the Friedel–Crafts alkylation of methoxybenzenes with a variety of aldehydes in the presence of BF3·OEt2. The generality of the method is demonstrated by screening a variety of di- or tri-substituted arenes as well as substituted aromatic, heteroaromatic, and aliphatic aldehydes. (−)-Tatarinoid C is synthesized in a single step following the same protocol. 相似文献
5.
A convenient and facile synthesis of Meflo-quine, based on sulphoxide-Grignard approach is described. 相似文献
6.
Disulfide bond formation by the oxidative cleavage of thiol acetates and thiol esters using “Clayan”s under microwave irradiation is described. The non-metallic and inexpensive nature of the reagent are the important features of the procedure. 相似文献
7.
Venkateshwarlu Jetti Ramakanth Pagadala Jyotsna S. Meshram Himani N. Chopde Latha Malladi 《Journal of heterocyclic chemistry》2013,50(Z1):E160-E165
In an attempt to synthesize antibacterial agents effective against gram‐positive and gram‐negative bacteria, the efficient synthesis of novel bis‐azetidinones ( 3a–j ) has been established. Thus, cycloaddition reaction of substituted bis‐imines with chloroacetylchloride under microwave irradiation in the presence of zeolite yielded bis‐azetidinones ( 3a–j ). Structures of the synthesized compounds have been elucidated on the basis of their elemental analysis and spectral data (IR, 1H‐NMR, 13C‐NMR, and mass spectra). The synthesized bis‐azetidinones were screened for their antibacterial activity against five microorganisms: Bacillus subtilis, Proteus vulgaris, Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli. They were found to exhibit good to moderate antibacterial activity. 相似文献
8.
A mild and efficient method has been developed for the chemoselective preparation of 1,1-diacetates (acylals) from aldehydes catalyzed in the presence of a catalytic amount (0.1 mmol) of anhydrous cobalt(II) bromide under solvent-free conditions. The remarkable selectivity under mild and neutral conditions, excellent yields, short reaction time, and easily available and inexpensive catalyst are important features of this method. 相似文献
9.
A one-pot three-component approach for the synthesis of thiazol-2-imines has been described by the reaction of amine, phenyl isothiocyanate and β-nitroacrylate in [Hbim]BF4 ionic liquid. The method is applicable for aromatic, benzylic, aliphatic and cyclic amines. Reusable reaction media, regioselectivity, mild reaction condition, catalyst free and high yield of products are the salient features of this protocol. 相似文献
10.
S. Paradkar C. Vrinda N. Jyotsna N. Sivaprasad 《Journal of Radioanalytical and Nuclear Chemistry》1999,241(3):561-567
A simple immunoradiometric assay for human follicle stimulating hormone (hFSH) was developed using a pair of monoclonal antibodies
obtained from commercial sources. The system developed makes use of a capture antibody covalently coupled to magnetisable
cellulose, which is a more economical and stable immunosorbent as compared to the other solid phases. The detector antibody
is labeled with125I using the chloramine-T oxidation method and purified by gel filtration. After initial cross-matching of the capture and
detector antibodies, various assay parameters have been optimised. This assay does not show any significant cross reactivity
with homologous hormones. A number of serum samples from men and women from reproductive age group was screened and compared
with another commercially available kit (r=0.98). Sensitivity of the assay is 1.4 mIU/ml, interassay variation is <5% and intraassay variation around 15%. The assay
is reproducible and sensitive enough for regular estimation of serum hFSH and is relatively inexpensive. 相似文献