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11.
Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm−1 region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined.
We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed
in these distances is an indication of the substitution effect.
It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the
case of o-disubstituted benzenes it is only 80% of the para-substituted shift. 相似文献
12.
A new organocatalytic system, novel chiral bisformamide and in situ generated L-proline-derived allylsilane reagent , which converts different aldimines to homoallylic amines in good to high yields (up to 95%) and good enantioselectivities (up to 85% ee) has been described. 相似文献
13.
14.
Devkar Santosh T. Badhe Yogesh S. Jagtap Suresh D. Hegde Mahabaleshwar V. 《平面色谱法杂志一现代薄层色谱法》2012,25(4):290-294
JPC – Journal of Planar Chromatography – Modern TLC - The high-performance thin-layer chromatography (HPTLC) method has been developed for the simultaneous quantification of withaferine... 相似文献
15.
A differential spectrophotometric determination of rhenium in its binary compound with uranium is described; the method is based on the action of tin(II) chloride on perrhenate in the presence of dimethylglyoxime with measurement at 445 nm. Uranium does not interfere. For solutions containing about 1 mg of rhenium, the coefficient of variation was 0.08%. 相似文献
16.
V. G. Dedgaonkar M. Mukherjee N. Jagtap 《Journal of Radioanalytical and Nuclear Chemistry》1988,126(4):301-305
Gamma irradiation of cation exchange resins results in breaking down of functional groups and as a result decreases in exchange capacity, weight and moisture content. There are significant changes in the pH of the effluent as well. The influence on these physico-chemical properties is more by 10–15% when the thorium form of polyacrylic carboxylic acid type exchanger is exposed to radiation as compared to the polystyrene sulphonic acid type exchanger exposed. 相似文献
17.
Measurement of methyl mercury (I) and mercury (II) in fish tissues and sediments by HPLC-ICPMS and HPLC-HGAAS 总被引:1,自引:0,他引:1
A procedure for the extraction and determination of methyl mercury and mercury (II) in fish muscle tissues and sediment samples is presented. The procedure involves extraction with 5% (v/v) 2-mercaptoethanol, separation and determination of mercury species by HPLC-ICPMS using a Perkin-Elmer 3 μm C8 (33 mm × 3 mm) column and a mobile phase 3 containing 0.5% (v/v) 2-mercaptoethanol and 5% (v/v) CH3OH (pH 5.5) at a flow rate 1.5 ml min−1 and a temperature of 25 °C. Calibration curves for methyl mercury (I) and mercury (II) standards were linear in the range of 0-100 μg l−1 (r2 = 0.9990 and r2 = 0.9995 respectively). The lowest measurable mercury was 0.4 μg l−1 which corresponds to 0.01 μg g−1 in fish tissues and sediments. Methyl mercury concentrations measured in biological certified reference materials, NRCC DORM - 2 Dogfish muscle (4.4 ± 0.8 μg g−1), NRCC Dolt - 3 Dogfish liver (1.55 ± 0.09 μg g−1), NIST RM 50 Albacore Tuna (0.89 ± 0.08 μg g−1) and IRMM IMEP-20 Tuna fish (3.6 ± 0.6 μg g−1) were in agreement with the certified value (4.47 ± 0.32 μg g−1, 1.59 ± 0.12 μg g−1, 0.87 ± 0.03 μg g−1, 4.24 ± 0.27 μg g−1 respectively). For the sediment reference material ERM CC 580, a methyl mercury concentration of 0.070 ± 0.002 μg g−1 was measured which corresponds to an extraction efficiency of 92 ± 3% of certified values (0.076 ± 0.04 μg g−1) but within the range of published values (0.040-0.084 μg g−1; mean ± s.d.: 0.073 ± 0.05 μg g−1, n = 40) for this material. The extraction procedure for the fish tissues was also compared against an enzymatic extraction using Protease type XIV that has been previously published and similar results were obtained. The use of HPLC-HGAAS with a Phenomenox 5 μm Luna C18 (250 mm × 4.6 mm) column and a mobile phase containing 0.06 mol l−1 ammonium acetate (Merck Pty Limited, Australia) in 5% (v/v) methanol and 0.1% (w/v) l-cysteine at 25 °C was evaluated as a complementary alternative to HPLC-ICPMS for the measurement of mercury species in fish tissues. The lowest measurable mercury concentration was 2 μg l−1 and this corresponds to 0.1 μg g−1 in fish tissues. Analysis of enzymatic extracts analysed by HPLC-HGAAS and HPLC-ICPMS gave equivalent results. 相似文献
18.
This work reports rhodium catalyzed selective hydroformylation of natural olefins like eugenol, estragole, anethole, prenol and isoprenol using biphenyl based Buchwald phosphine ligands (S‐Phos ( L 1 ), t‐Bu XPhos ( L 2 ), Ru‐Phos ( L 3 ), Johnphos ( L 4 ) and DavePhos ( L 5 ). Ru‐Phos ( L 3 ) ligand exhibited high impact on the hydroformylation of eugenol providing high selectivity (90%) of linear aldehyde as major product. In addition, internal natural olefins like anethole and prenol provided moderate to high selectivity (65% and 85% respectively) of branched aldehydes as a major products. The various reaction parameters such as influence of ligands, P/Rh ratio, syngas pressure, temperature, time and solvents have been studied. A high activity and selectivity gained on the way to the linear aldehydes it may be due to the bulky, steric cyclohexyl and isopropoxy groups present in L 3 phosphine ligand. Moreover, this catalytic system was smoothly converting natural olefins into corresponding linear and branched aldehydes with higher selectivity under the mild reaction conditions. 相似文献
19.
Many aspects of photophysical, photostability and laser properties of kiton red S dye remain unresolved, particularly for
pumping with 578 nm radiation of CVL and 532 nm output of Nd:YAG lasers, and these are studied using different alcohol- and
water-based binary solvents. Our results show that methanol is better suited for low and high-repetition-rate KRS dye lasers
because of its superior laser efficiency, photostability as well as photothermal properties. 相似文献
20.
The synthesis of diblock copolymer of tert butyl acrylate and methyl methacrylate (PTBA‐b‐PMMA) was prepared by Atom Transfer Radical Polymerization (ATRP). At the outset, macroinitiator of tert butyl acrylate (TBA) was prepared by using N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) ligand, Cuprous Bromide (CuBr) catalyst, and ethyl 2‐bromo isobutyrate (2‐EiBBr) initiator. Immediately after the intake of the utmost TBA in the macroinitiator, the second monomer, methyl methacrylate (MMA) was added to the reaction medium, for further polymerization. In these experiments the compositions of the monomers were varied, although the concentrations of ligand, catalyst and the initiator were kept constant. Subsequently, the diblock copolymers were hydrolyzed, under acidic conditions, using HCl catalyst, to obtain an amphiphilic copolymer. These block copolymers were characterized by NMR, IR, GPC, and DSC techniques. These copolymers will be used in, powder coatings, pigment dispersions, and as compatibilizers in polymer blends. 相似文献