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排序方式: 共有259条查询结果,搜索用时 15 毫秒
71.
Kazem Naghavi Elias Saion Khadijeh Rezaee Wan Mahmood Mat Yunus 《Radiation Physics and Chemistry》2010,79(12):1203-1208
Colloidal silver nanoparticles were synthesized by γ-irradiation-induced reduction method of an aqueous solution containing silver nitrate as a precursor in various concentrations between 7.40×10?4 and 1.84×10?3 M, polyvinyl pyrrolidone for capping colloidal nanoparticles, isopropanol as radical scavenger of hydroxyl radicals and deionised water as a solvent. The irradiations were carried out in a 60Co γ source chamber at doses up to 70 kGy. The optical absorption spectra were measured using UV–vis spectrophotometer and used to study the particle distribution and electronic structure of silver nanoparticles. As the radiation dose increases from 10 to 70 kGy, the absorption intensity increases with increasing dose. The absorption peak λmax blue shifted from 410 to 403 nm correspond to the increase of absorption conduction electron energy from 3.02 to 3.08 eV, indicating the particle size decreases with increasing dose. The particle size was determined by photon cross correlation spectroscopy and the results showed that the particle diameter decreases exponentially with the increase of dose. The transmission electron microscopy images were taken at doses of 20 and 60 kGy and the results confirmed that as the dose increases the diameter of colloidal silver nanoparticle decreases and the particle distribution increases. 相似文献
72.
Various aryl aldehydes underwent prompt one pot conversion into the corresponding nitriles in high yields by reacting with hydroxylamine hydrochloride supported on melamine formaldehyde under microwave irradiation in the presence of ammonium acetate as catalyst. 相似文献
73.
Mohammad Hossein Habibi Morteza Montazerozohori Kazem Barati Ross W. Harrington William Clegg 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(12):m592-m594
The 1:1 adduct of N,N′‐bis(2‐chlorobenzylidene)ethylenediamine (cb2en) with copper(I) chloride proves to be an ionic compound with CuI‐centred cations and anions, [Cu(C16H14Cl2N2)2][CuCl2]·CH3CN. In the cation, the CuI atom has a flattened tetrahedral coordination geometry, with a small bite angle for the chelating ligands, which form a double‐helical arrangement around the metal centre. The anion is almost linear, as expected. The packing of the cations involves intermolecular π–π interactions, which lead to columns of translationally related cations along the shortest unit‐cell axis, with anions and solvent molecules in channels between them. 相似文献
74.
The 4-chloromethyl styrene (CMS) was copolymerized with different styrenic monomers such as methyl styrene, 4-methoxy styrene and α-methyl styrene by free radical polymerization method at 70 ± 1 °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator and the copolymers I, II and III collected respectively. The very bulky tris(trimethylsilyl)methyl {trisyl} substituents were covalently attached to the obtained copolymers with replacement of all the chlorine atoms in CMS units. The polymers, obtained in quantitative yields, were characterized by FT-IR, 1H NMR and 13C NMR spectroscopy; differential scanning calorimetry (DSC) and GPC studies. All the polymers containing trisyl groups showed a high glass transition temperature (in the range 150-190 °C) in comparison with copolymers I-III (in the range 90-95 °C). The increase of the glass transition temperature reflects the substantial increase in rigidity of new polymers bearing very bulky substituents in side chains. 相似文献
75.
Mohammad Kazem Rofouei Asieh Ahmadalinezhad Mehdi Taghdiri 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):377-382
The interaction of 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (Kryptofix5) with alkali-metal cations (Li+, Na+, K+) in aprotic medium (acetonitrile) has been investigated. Conductance measurements demonstrated that 1:1 metal cation:ligand
stoichiometries are found with these cations in this solvent. 7Li and 23Na NMR experiments were carried out by titration of the metal cation solutions with Kryptofix5 solution in CD3CN + CH3CN at 298 K. Thermodynamic parameters of complexation for this ligand and alkali-metal cations in acetonitrile at 278–308 K
were derived from titration conductometry. The highest stability is found for sodium complex. The complexation sequence, based
on the value of log K at 278–308 K was found to be Na+ > K+ > Li+. 相似文献
76.
77.
Benzyl chloride was treated with (Me3Si)3CLi to give (Me3Si)3CCH2Ph (1). A new styrene derivative, (Me3Si)3CCH2C6H4(CHCH2-p) (2), was synthesized by reaction of p-vinylbenzyl chloride with (Me3Si)3CLi in the presence of CuCl. Addition and oxidation reactions on 2 gave a series of new compounds (Me3Si)3CCH2C6H4X-p (X = CH2CH3, CHBrCH2Br, CHClCH2I, CHBrCH2I, cyclo-C3H3Cl2, CHOHCH2OH, COOH, CH2OH). 相似文献
78.
Colin Eaborn Duncan A.R. Happer Peter B. Hitchcock Steven P. Hopper Kazem D. Safa Stephen S. Washburne David R.M. Walton 《Journal of organometallic chemistry》1980,186(3):309-323
The compound (Me3Si)3CSiPh2F loses Me3SiF under reflux or on passage through a tube at 450°C to give three products, A, B, and C, in approximately 20/20/60 ratio. Products A and B, which are solids, were shown by X-ray crystallographic analysis to be the diastereoisomeric forms of 1-dimethylsila-2-trimethylsilyl-3-[(methyl)(phenyl)sila]indane. From its mass and 1H NMR spectra, C (a liquid) was tentatively identified as 1,3-bis(dimethylsila)-2-[(dimethyl)(phenyl)silyl]indane. All three products are isomers of the sila-olefin (Me3Si)2CSiPh2, and it is suggested that the latter is first formed by loss of Me3SiF from (MeSi)3CSiPh2F, and the equilibrium (Me3Si)2CSiPh2 ? (Me3Si)(Ph2MeSi)CSiMe2 ? (Me3Si)(PhMe2Si)CSiMePh ? (Me2PhSi)2CSiMe2 is then rapidly established; internal cyclizations involving addition of aryl CH bonds across SiC bonds then occur to give the observed products. Consistent with this is the observation that a mixture of silicon alkoxides, thought to be (Me3Si)2CHSiPh2OMe and its isomers (which would be formed by addition of methanol across the SiC bonds of the four sila-olefins) is produced when methanol is passed through the hot tube with the (Me3Si)3CSiPh2F.Full structural details are given for compounds A and B. Some features of interest are: (a) the conformation of the 5-membered ring is different in the two diastereoisomers; (b) the exocyclic SiCSiMe3 bond angles, of ca. 120° are unusually large; and (c) there is a little distortion of the fused benzene ring, which is attributed to the effect of silicon substituents on the hybridization of carbon atoms to which they are attached. 相似文献
79.
80.