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排序方式: 共有94条查询结果,搜索用时 15 毫秒
71.
Dubravka Matkovi‐alogovi Erim Bei Mladen Biru Mario Gabri
evi 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):o694-o695
The title compound, N‐hydroxy‐2‐(trimethylammonio)acetamide chloride, C5H13N2O2+·Cl−, has been synthesized and structurally characterized. The structure consists of betainohydroxamic acid cations and Cl− anions linked by N—H⋯Cl and O—H⋯Cl hydrogen bonds into chains along [001]. It was found that the positive inductive effect of the charged N atom in close proximity to the hydroxamate carbonyl O atom has a negligible effect on the hydroxamic C—N bond length. 相似文献
72.
73.
Dr. Dubravka Z. Vojislavljević‐Vasilev Dr. Goran V. Janjić Dr. Vesna B. Medaković Jelena P. Blagojević Prof. Dr. Snežana D. Zarić 《Chemphyschem》2014,15(11):2386-2396
The parallel interactions of non‐coordinated and coordinated water molecules with an aromatic ring were studied by analyzing data in the Cambridge structural database (CSD) and by using quantum chemical calculations. The CSD data show that water/aromatic contacts prefer parallel to OH/π interactions, which indicates the importance of parallel interactions. The results reveal the influence of water coordination to a metal ion; the interactions of aqua complexes are stronger. Coordinated water molecules prefer a parallel‐down orientation in which one O?H bond is parallel to the aromatic ring, whereas the other O?H bond points to the plane of the ring. The interactions of aqua complexes with parallel‐down water/benzene orientation are as strong as the much better known OH/π orientations. The strongest calculated interaction energy is ?14.89 kcal mol?1. The large number of parallel contacts in crystal structures and the quite strong interactions indicate the importance of parallel orientation in water/benzene interactions. 相似文献
74.
Dubravka Pokrajac Lorna Jane Campbell Vladimir Nikora Costantino Manes Ian McEwan 《Experiments in fluids》2007,42(3):413-423
We explore a new application of the quadrant method in the context of the double-averaged Navier–Stokes equations for studying
open channel flow near rough beds. Quadrant analysis is applied to spatial disturbances of time-averaged velocity components,
using the experimental data from flow over two-dimensional regular transverse square-bar roughness. The spatial velocity disturbances
change periodically performing a full cycle over a single roughness element, so that the quadrant diagrams are regular closed
orbits. A colour code is used to produce a quadrant map of the flow cross-section, which reveals contributions from each quadrant
to the time-averaged momentum transfer. 相似文献
75.
A new sensitive potentiometric surfactant sensor was prepared based on a highly lipophilic 1,3-didecyl-2-methyl-imidazolium cation and a tetraphenylborate antagonist ion. This sensor was used as a sensing material and incorporated into the plasticized PVC-membrane. The sensor responded fast and showed a Nernstian response for investigated surfactant cations: cetylpyridinium chloride (CPC), hexadecyltrimethylammonium bromide (CTAB) and Hyamine with slope 59.8, 58.6 and 56.8 mV/decade, respectively. The sensor served as an end-point detector in ion-pair surfactant potentiometric titrations using sodium tetraphenylborate as titrant. Several technical grade cationic surfactants and a few commercial disinfectant products were also titrated, and the results were compared with those obtained from a two-phase standard titration method. The sensor showed satisfactory analytical performances within a pH range of 2-11, and exhibited excellent selectivity performance for CPC compared to all of the organic and inorganic cations investigated. The influence of the nonionic surfactants on the shape of titration curves was negligible if the mass ratio of ethoxylated nonionic surfactants and cationic surfactants (EONS:CS) was not greater than 5. 相似文献
76.
Kobetić R Gembarovski D Baranović G Gabelica V 《Journal of mass spectrometry : JMS》2008,43(6):753-764
In order to monitor the progression of the synthesis and the separation of novel mixed-ligand iron complexes containing 1,10-phenanthroline, 1,10-phenanthroline-5,6-dione, and NCS- as ligands all products were mass analyzed by electrospray ionization ion trap MS/MS. The spectra of methanol (MeOH), acetonitrile (ACN), water, and ethanol (EtOH) solutions were collected and the results were compared. It was detected under applied electrospray ionization mass spectrometry (ESI-MS) conditions that MeOH, water, and EtOH formed solvent clusters around the free or complexed 1,10-phenanthroline-5,6-dione. Owing to the solvent-ligand hydrogen-bond formation, the solvent-ligand clusters were formed in the polar protic solvents. The number of protic solvent molecules per complex ion in cluster depended on the number of 1,10-phenanthroline-5,6-dione ligands in the complex ion. Unlike MeOH, EtOH, or water, ACN was not involved in the formation of the solvent clusters with the iron complexes containing 1,10-phenanthroline-5,6-dione as ligand. We also showed that the NCS- group under certain solvent conditions served as a bidentate ligand. 相似文献
77.
78.
Pavle Trošelj Ivica Đilović Dubravka Matković‐Čalogović Davor Margetić 《Journal of heterocyclic chemistry》2013,50(1):83-90
Cycloaddition reaction of 2,5‐bis(trifluoromethyl)‐1,3,4‐oxadiazole with strained olefinic bonds of norbornenes was used to synthetize functionalized polynorbornanes. This simple, one step procedure was more effective when reaction was carried out by classical heating, in comparison to microwave‐assisted reactions. Various functional groups were stable in the reaction conditions (ester, imide, phthalimide, piperidyl, and carboxylic acid), whereas anhydride, N‐Boc, or TMS functionalities do not withstand reaction conditions. 相似文献
79.
Jürgen Brem Monica-Ioana Toşa Csaba Paizs Anca Munceanu Dubravka Matković-Čalogović Florin-Dan Irimie 《Tetrahedron: Asymmetry》2010,21(16):1993-1998
The synthesis of both enantiomers of 1-(10-alkyl-10H-phenothiazin-3-yl)ethanols and their butanoates by enantiomer-selective acylation of racemic alcohols with the lipase from Pseudomonas fluorescens (L-AK) or/and by methanolysis of the corresponding racemic esters with lipase B from Candida antarctica (CaL-B) is described. The absolute configuration of the enantiomerically pure enantiomers was determined by X-ray crystallography. 相似文献
80.
Berislav Perić Nevenka Brničević Marijana Jurić Pavica Planinić Dubravka Matković-Čalogović 《Structural chemistry》2009,20(5):933-941
Abstract The compound [NH4][(CH3)2NH2]2[Ta(C2O4)4]·2H2O has been synthesized and characterized by elemental and TG/DTA analyses, IR spectroscopy and by the single-crystal X-ray
diffraction study. The structure comprises the [Ta(C2O4)4]3− anion, NH4
+ and [(CH3)2NH2]+ cations and crystallization water molecules. The Ta atom is octacoordinated by oxygen atoms from four bidentate oxalate groups
forming a coordination polyhedron close to the triangular dodecahedron. The charge-assisted hydrogen bonds from both cations
connect the [Ta(C2O4)4]3− anions into a three-dimensional framework.
Graphical Abstract The synthesis and properties of [NH4][(CH3)2NH2]2[Ta(C2O4)4]·2H2O, the first structurally characterized compound with the tetra(oxalato)tantalate(V) anion, is reported.
相似文献