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951.
A method for obtaining general equations for the scattered intensities from vibronic systems is given. The approximate formulas obtained are used to calculate the effects on the electron diffraction pattern for molecules with doubly degenerate electronic E terms interacting with e-type vibrations (Ee-type of problem). The results of the approximate calculations are compared to more precise results, based on numerical solution of the vibronic problem. 相似文献
952.
Bukuo Ni 《Tetrahedron letters》2006,47(41):7331-7334
Nine chiral room temperature ionic liquids (RTILs), which contain a chiral moiety and a urea functionality bonded to a imidazolium ring, have been designed and synthesized. The synthesis of these ionic liquids is concise and practical due to the commercial availability of the starting materials. These novel RTILs were readily prepared from 1-(3-aminopropyl)imidazole and amino acid ester derived isocyanates. We envision that these new chiral RTILs can serve as effective reaction media as well as chiral catalysts, which are presently being investigated in our laboratory. 相似文献
953.
Nitrate determination in waters is generally carried out with cadmium filings and carcinogenic reagents or by reaction with phenolic compounds in highly concentrated sulfuric acid medium. In this work, it was developed a green analytical procedure for nitrate determination in natural waters based on direct spectrophotometric measurements in ultraviolet, using a flow-injection system with an anion-exchange column for separation of nitrate from interfering species. The proposed method employs only one reagent (HClO4) in a minimum amount (equivalent to 18 μL concentrated acid per determination), and allowed nitrate determination within 0.50-25.0 mg L−1, without interference of up to 200.0 mg L−1 humic acid; 1.0 mg L−1 NO2−; 200.0 mg L−1 PO43−; 75.0 mg L−1 Cl−; 50.0 mg L−1 SO42− and 15.0 mg L−1 Fe3+. The detection limit (99.7% confidence level) and the coefficient of variation (n = 20) were estimated as 0.1 mg L−1 and 0.7%, respectively. The results obtained for natural water samples were in agreement with those achieved by the reference method based on nitrate reduction with copperized cadmium at the 95% confidence level. 相似文献
954.
Helmut Fischer 《Journal of organometallic chemistry》1979,170(3):309-317
The reaction of pentacarbonyl(arylmethoxycarbene)tungsten, (CO)5W[C(OCH3(p-C6H4R)] [R = OCH3 (a), CH3 (b), H (c), Br (d), CF3 (e)], with tributylphosphane at low temperatures results in a reversible addition of the phosphane to the carbene carbon atom. The addition—dissoziation equilibrium is not only dependent on the temperature but also to a strong degree on the nature of the substituent R. ΔG, ΔH and the equilibrium constant K increase in the series from R = OCH3 to R = CF3. With the exception of R = OCH3 the substituents b to e form an isentropic class. For all substituents (a to e) a linear dependency from Jaffés σ-constants was observed for ΔH. Good linear correlation for the substituents b to e was also found for log K and σ as well as for log K and the CO-force constants kcis and ktrans. 相似文献
955.
The assignment of the fundamental modes and the symmetry of the oxalate ion in solution are re-examined in the light of new experimental evidence. Particular attention is given to the Raman bands at 1455 and 1488 cm?. 相似文献
956.
957.
Mohammad Shakirullah Imtiaz Ahmad Mohammad Saeed Mohammad Arsala Khan Habib‐ur‐Rehman Mohammad Ishaq Amjad Ali Shah 《中国化学会会志》2006,53(2):335-342
The present paper demonstrates the review of some acid processes as well as development of some new solvent processes for reclamation of used lubricating oils. The conventional processes are found to be of low yield (? 50%), laborious, time consuming and environmentally hazardous, because of residual acidic sludge. Based on the findings, a new modified Aluminium sulphate‐sodium silicate‐acid‐base method employing a small quantity of acid and giving a high yield (? 60%) is proposed. Further, to avoid use of acid, new regeneration processes based on solvent extraction were investigated. They are termed CCl4‐alcohol method, Dodecane‐alcohol method and Toluene‐alcohol method. These processes are not only cost effective in terms of complete solvent recovery, but are rapid, less time consuming, more environmentally friendly and gave a high yield (70–75%). The virgin lubricants (Castrol GTX and Rimula‐C) as well as oils recovered by different methods were also characterized physicochemically to determine kinematic viscosity, density, refractive index, carbon distribution, wear scar diameter, % Conradson carbon residue, % ash, % chloride, pour point, etc. Results obtained show that many of the physico‐chemical properties of the recovered oils are in good agreement with those of virgin oils. The n.d.M analysis was also performed which shows that virgin oils have 73 ± 3% paraffinic carbon, 26 ± 3% naphthenic carbon and about 1% aromatic carbon. The recovered oils also showed nearly the same chemical composition. The UV‐Visible spectra of the recovered oils are all similar to those of virgin lubricants. The results suggest that the oils recovered by solvent treatments, particularly Dodecan‐alcohol and Toluene‐alcohol methods, may serve for lubrication purposes and can be rendered as excellent as virgin lubricants with the addition of certain additives. The proposed methods may be considered as alternative cost effective green techniques for acid reclamation processes and being the motivation of the present investigation. 相似文献
958.
Trace amounts of substances have been related to iodine consumption monitored by chemiluminescence from the iodine-luminol system. Iodine titrations of sulphite and arsenic(III) have been carried out at levels of 1.0 x 10(-7) and 5.0 x 10(-8)M with a precision and error of better than 1% on a day-to-day basis. A calibrated standard of 1.8 ppm SO(2) in air was analysed with a precision of +/-1.2%, and an error of 0.9%. A rate method has been developed based on the reaction between iodine and penicillin G; a linear range from 10(-8) to 10(-7)M was found, the precision being +/-9%. 相似文献
959.
Sally Chapman 《Chemical physics letters》1981,80(2):275-279
Energy distributions in the products of the ion-molecule reaction Cl? + HBr → HC1 + Br? have been studied using quasiclassical trajectories on a semi-empirical collinear potential energy surface. Vibrational energy is favored in the products. While some trajectories are long-lived, the kinematic factor of the light central atom prevents effective energy redistribution. 相似文献
960.
Molecular N2 emission, observed from an Ar(3Po, 2) and Xe(3P2) + N2 flowing afterglow apparatus, indicates that the energy pooling reaction by 2N2(A 3Σ+u) generates the emission from the Herman infrared system, which is an unassigned nitrogen band system. A lower limit to the formation rate constant for the upper state of the Herman infrared system was found to be 2.5 × 10-11 cm3 molecule?1 s?1. The information presented here may help in the identification of the upper and lower states of the emission system. The 2N2(A) energy pooling reaction also forms N2(B3 Πg, v? 8) but a rate constant cannot be assigned from the present data. 相似文献