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991.
This paper describes the synthesis and characterization of aromatic diimide–diacids (DIDAS) obtained by reacting pyromellitic
dianhydride (PMDA), 4,4′-oxo diphthalic anhydride (ODA), 1,4,5,8-naphthalene tetra carboxylic dianhydride (NTDA) with excess
of 4-aminobutyric acid (B) or 6-aminohexanoic acid (H) using N,N-dimethyl formamide (DMF) as solvent. The synthesized compounds were used as curing agents to investigate the effect of structure
on the curing and thermal behaviour of diglycidyl ether of bisphenol-A (DGEBA). Structural characterization of DIDAS was done
by using FTIR, 1H-NMR, 13C-NMR spectroscopy and elemental analysis. Curing behaviour of DGEBA in the presence of aromatic DIDAS was investigated by
differential scanning calorimetry (DSC). The peak exotherm temperature (T
P) was low in the case of DIDAS synthesized from ODA and high in the case of DIDAS synthesized from NTDA. Thermal stability
of the isothermally cured DGEBA with DIDAS was investigated using dynamic thermogravimetry in nitrogen atmosphere. The char
yield was highest for resin cured with DIDAS containing NTDA. 相似文献
992.
Bruno Fabre Soraya Ababou-Girard Prabhpreet Singh Jitendra Kumar Sandeep Verma Alberto Bianco 《Electrochemistry communications》2010,12(6):831-834
Redox-active ferrocene was assembled on gold surfaces through the hydrogen bonding interactions between adenine-substituted ferrocene and a uracil-terminated organothiol monolayer. The surface coverage of ferrocene Γ could be varied from ca. 4 × 10? 11 to 2.0 × 10? 10 mol cm? 2 by diluting the thiol-modified uracil derivative with inert 1-octanethiol. A decrease in the apparent electron transfer rate constant for ferrocene, kapp, from ca. 50 to 10 s? 1 was observed upon increasing Γ. 相似文献
993.
Hari Ji Singh Bhupesh Kumar Mishra Nand Kishor Gour 《Theoretical chemistry accounts》2010,125(1-2):57-64
The unimolecular decomposition reaction of CF3CCl2O radical has been investigated using theoretical methods. Two most important channels of decomposition occurring via C–C bond scission and Cl elimination have been considered during the present investigation. Ab initio quantum mechanical calculations are performed to get optimized structure and vibrational frequencies at DFT and MP2 levels of theory. Energetics are further refined by the application of a modified Gaussian-2 method, G2M(CC,MP2). The thermal rate constants for the decomposition reactions involved are evaluated using Canonical Transition State Theory (CTST) utilizing the ab initio data. Rate constants for C–C bond scission and Cl elimination are found to be 6.7 × 106 and 1.1 × 108 s?1, respectively, at 298 K and 1 atm pressure with an energy barrier of 8.6 and 6.5 kcal/mol, respectively. These values suggest that Cl elimination is the dominant process during the decomposition of the CF3CCl2O radical. Transition states are searched on the potential energy surface of the decomposition reactions involved and are characterized by the existence of only one imaginary frequency (NIMAG = 1) during frequency calculation. The existence of transition states on the corresponding potential energy surface is further ascertained by performing intrinsic reaction coordinate (IRC) calculation. 相似文献
994.
Manish Pratap Singh Rajendra Kumar Singh Dr. Suresh Chandra Prof. 《Chemphyschem》2010,11(9):2036-2043
Porous silica matrices of different pore sizes with confined ionic liquid (1‐butyl‐3‐methylimidazolium hexafluorophosphate) [BMIM] [PF6] were prepared by sol‐gel technique using a tetraethyl orthosilicate (TEOS) precursor with an aim to study the changes in physico‐chemical properties of ionic liquid on confinement. It is found that on confinement 1) melting point decreases, 2) fluorescence spectra shows a red shift and 3) the vibrational bands are affected particularly those of imadazolium ring, which interacts more with the walls of the silica matrix. Preliminary theoretical calculations suggest that SiO2 matrix interact more with the heterocyclic group of [BMIM] cation than the tail alkyl chain end group resulting in significant changes in the aromatic vibrations. 相似文献
995.
Nanocrystalline Ce(1-x)Fe(x)O(2-δ) (0 ≤ x ≤ 0.45) and Ce(0.65)Fe(0.33)Pd(0.02)O(2-δ) of ~4 nm sizes were synthesized by a sonochemical method using diethyletriamine (DETA) as a complexing agent. Compounds were characterized by powder X-ray diffraction (XRD), X-ray photo-electron spectroscopy (XPS) and transmission electron microscopy (TEM). Ce(1-x)Fe(x)O(2-δ) (0 ≤ x ≤ 0.45) and Ce(0.65)Fe(0.33)Pd(0.02)O(2-δ) crystallize in fluorite structure where Fe is in +3, Ce is in +4 and Pd is in +2 oxidation state. Due to substitution of smaller Fe(3+) ion in CeO(2), lattice oxygen is activated and 33% Fe substituted CeO(2)i.e. Ce(0.67)Fe(0.33)O(1.835) reversibly releases 0.31[O] up to 600 °C which is higher or comparable to the oxygen storage capacity of CeO(2)-ZrO(2) based solid solutions (Catal. Today 2002, 74, 225-234). Due to interaction of redox potentials of Pd(2+/0)(0.89 V) and Fe(3+/2+) (0.77 V) with Ce(4+/3+) (1.61 V), Pd ion accelerates the electron transfer from Fe(2+) to Ce(4+) in Ce(0.65)Fe(0.33)Pd(0.02)O(1.815), making it a high oxygen storage material as well as a highly active catalyst for CO oxidation and water gas shift reaction. The activation energy for CO oxidation with Ce(0.65)Fe(0.33)Pd(0.02)O(1.815) is found to be as low as 38 kJ mol(-1). Ce(0.67)Fe(0.33)O(1.835) and Ce(0.65)Fe(0.33)Pd(0.02)O(1.815) have also shown high activity for the water gas shift reaction. CO conversion to CO(2) is 100% H(2) specific with these catalysts and conversion rate was found to be as high 27.2 μmoles g(-1) s(-1) and the activation energy was found to be 46.4 kJ mol(-1) for Ce(0.65)Fe(0.33)Pd(0.02)O(1.815). 相似文献
996.
D. P. Singh V. Malik R. Kumar K. Kumar 《Russian Journal of Coordination Chemistry》2010,36(3):220-225
The condensation reaction of succinyldihydrazide with glyoxal in the presence of divalent metal ions (1: 1: 1) results in
the formation of the complexes of type [M(C6H8N4O2)X2], where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and X = Cl−, NO3−, CH3COO−. The complexes have been characterized with the aid of elemental analyses, conductance measurements and electronic, NMR,
infrared spectral studies. On the basis of these studies, a six-coordinated distorted octahedral geometry in which two nitrogen
and two carbonyl oxygen atoms are suitably placed for coordination toward metal ion, has been proposed for all the complexes.
The complexes were tested for their in vitro antibacterial activity. Some of the complexes showed remarkable antibacterial
activities against some selected bacterial strains. 相似文献
997.
The potentiometric response characteristics of zinc ion selective PVC-based membrane electrode employing 1,12,14-triaza-5,8-dioxo-3(4),9(10)-dibenzoyl-1,12,14-triene as an inophore was investigated. The proposed electrode exhibits a Nernstian behavior with a slope of 29.2 ± 0.4 mV per decade with a working concentration range of 1.3 × 10?7–1.0 × 10?1 mol L?1 and a detection limit of 1.0 × 10?8 mol L?1. The membrane having the composition as TDODBCPT:O-NPOE:PVC:OA; 7:57:30:6 wt.% exhibits the best results. It has a fast response time of 7 s and can be used for at least 100 days without any considerable divergence in potential. The proposed electrode show good discrimination of Zn2+ ion from diverse ions. The potential response remains constant over a pH range of 3.5–9.2. The electrode found well work under laboratory conditions. The proposed sensor directly used for determination of zinc ions in human hair sample, wastewater and an indicator electrode with EDTA titration. 相似文献
998.
999.
Smithia conferta Sm. (Leguminasae), is a commonly used plant in Indian traditional medicine. In the current study anti-ulcer activity of its petroleum ether, alcohol and aqueous extracts of leaves were investigated using different animal models. All extracts were also subjected to phytochemical analysis and their toxic potential. Petroleum ether extract was found to contain steroids; alcohol extract revealed the presence of isoflavonoids, alkaloids and carbohydrates; while aqueous extract was found to contain amino acids, carbohydrates and flavonoids. S. conferta aqueous and alcoholic extracts were found to be non-toxic up to 5000 mg/kg dose level while petroleum ether extract was safe only up to a dose of 2000 mg/kg after single dose administration of the extracts.During confirmation of the claimed anti-ulcer activity, treatment with aqueous and alcoholic extracts showed significant reduction in ulcer index, free acidity as well as total acidity in pylorus ligated rats. However, petroleum ether extract showed relatively less profound reduction in all these indices. The anti-ulcer activity observed in aqueous extract treatment group was nearly equivalent to the standard group. 相似文献
1000.
Ashok K.S. Chauhan Poornima Singh Ray J. Butcher 《Journal of organometallic chemistry》2010,695(23):2532-2539
Room temperature oxidative addition of α-bromo-2-acetylthiophene to elemental tellurium and aryltellurium(II) bromide provides direct routes to (2-thiophenoylmethyl)tellurium(IV) dibromides, (2-(C4H3S)COCH2)2TeBr2 (1b) and 2-(C4H3S)COCH2ArTeBr2 (Ar = 1-C10H7, Npl, 2b; 2,4,6-Me3C6H2, Mes, 3b). The chloro analogues, 2-(C4H3S)COCH2ArTeCl2 (Ar = Npl, 2a; Mes, 3a) were prepared by the condensation reaction of the parent methyl ketone with NplTeCl3 or MesTeCl3. Metathesis of these products with an alkali iodide affords the iodo analogues 1c, 2c and 3c. These diorganotellurium dihalides are reduced with aqueous bisulfite to diorganotellurides 1-3, which can be oxidized readily with dihalogens to the desired diorganotellurium(IV) dihalides. Compound 1 is a rare example of a symmetrical telluroether with Csp3-Te-Csp3 grouping that has been characterized by single-crystal diffraction techniques. Preference of the 2-thiophenoylmethyl ligand for small-bite (C, O) chelation over less strained (C, S) coordination is evident in the crystal structures of the Te(IV) compounds 1b, 2a, 2b and 3a. The unexpected transoidal orientation of the two acylmethyl ligands in the solid state molecular configuration of symmetrical diorganotellurium(IV) dibromide 1b appears to be a combined effect of electronic repulsion due to the thiophene moieties and steric repulsion of bromo ligands. 相似文献