Studies of Solvent Effects on Structure and Low Frequency Vibrational Spectra of 2,4-Dinitrotoluene

Solvent effects on 2,4-dinitrotoluene(2,4-DNT) molecule in different solvents(toluene,ethanol,and water) were studied via DFT PCM method at B3LYP/6-311+G(d,p) level. The influences of these solvents on the molecular structure,vibrational spectra,charge distribution,and dipole moment were studied as well. The results show that PCM computations are successful in describing the vibrational spectra of 2,4-DNT molecules in these solutions and the solvent effects on the low frequency vibrational spectra are weak.     

ICP-OES测定地质样品中微量铼

应用ICP-OES测定矿样中铼,样品经过碱熔水浸取,过滤得到的滤液用环己酮萃取分离,水和三氯甲烷反萃取后得到的水相,酸化后,进行铼的测定。着重讨论了萃取分离的必要性和Mo对铼的干扰,并通过各种参数条件的优化选择进行了铼的测定,取得满意结果。本法准确度高,灵敏度高,分析线性宽,分析速度快,测定范围为0.5-100μg/mL,RSD在2.57%—6.81%之间。     

异丙基膦酸单异辛酯负载树脂用于萃取色层以分离稀土元素

本文报道异丙基膦酸单异辛酯负载树脂分离稀土(Ⅲ)的性能。实验结果表明采用不同浓度的稀盐酸淋洗可依次分离15种稀土(Ⅲ)。除钇(Ⅲ)/铒(Ⅲ)对(R.1.0)外,其余各相邻稀土(Ⅲ)均达到基线分离(R_a≥1.5)。所用酸度不超过2.0mol/L,低于常用的磷酸双(2-乙己基)酯(HDEHP)和2-乙已基膦酸单2-乙己基酯(HEHEHP)所需酸度。     

Influence of the solvent and of the counteranion on the structure of silyl cations stabilized by a terdentate aryldiamine ligand

Solution NMR studies of silyl cations [ArSiMe₂]⁺X⁻ (X = I, CF₃SO₃) incorporating the terdentate aryl diamine ligand Ar - C₆H₃₋ 2,6-(CH₂NMe₂)₂ have been carried out in a protic solvent (methanol-d₄) and in an aprotic solvent (CD₂Cl₂). This study has shown that the structure of these silyl cations is highly dependent on the solvent. In CD₂Cl₂, the silyl cation is five-coordinated owing to the coordination of one NMe₂ group and of the anion to the silicon centre which gives rise to a dissymmetric structure. On the other hand, in CD₃OD there is no coordination of the anion, but the silyl cation is also probably five-coordinated due to the coordination of the solvent to the silicon atom which is supported by the X-ray analysis of the compound 9. With the weakly nucleophilic anion BPh₄⁻ in CD₂Cl₂, in addition to the silyl cation previously described, another five-coordinated silyl cation resulting from the coordination of both NMe₂ groups to the Si centre was postulated.     

Determination of Anionic Surfactant in Fresh Water and in Sea Water

Ion pairs formed from suitable cationic dye and anionic surfactant in water were separated by solvent extraction. The extracts were used subsequently for spectrophotometric determinations. The extraction of ion pairs with various combinations is described. Of the dyes and solvents examined, ethyl violet and p-xylene are the most useful combination as the cationic dye and extraction solvent. The extracts are determined spectrophotometrically at 611.5 nm; the molar absorptivity is 1, 01 × 10⁵ M^?1 cm^?1. The detection limit is 1.4 ppb in water. The method is simple, rapid and sensitive. It can also be applied to the determination of anionic surfactants in sea water.     

Solvent sorption measurements in polymeric membranes with ATR-IR spectroscopy

Long-term stability and performance of polymeric membranes in solvent and mixed solvent media can be reduced due to sorption and swelling of the membrane matrix. For this reason quantification of sorption and swelling is of major importance for the development of future applications of membrane processes in solvent and mixed solvent media. In this work a method is discussed, based on attenuated total reflectance infrared spectroscopy (ATR-IR), to establish sorption and sorption selectivity of a cellulose acetate (CA) membrane in water/methanol and water/ethanol mixtures. By analysis of specific peaks from the ATR-IR spectra of the solvents, the preferential sorption of water in CA membranes can be quantified. In the presence of methanol, the selectivity for water ranges from 2.5 to 3.5 between 52 and 90% of methanol. For ethanol, the selectivity for water ranges from about 1 (30% ethanol) to 2 (90% ethanol). From the work it follows that ATR-IR provides an easy and non-destructive method to study the sorption behavior of the polymeric membrane separation layer.     

The effect of coordination on the reaction of N-tosyl imines with diethylzinc

The effect of coordination on the reaction of N-tosyl imines and diethylzinc was studied in detail. It showed that there was strong coordination between N-tosyl imine and diethylzinc. Due to this coordination, N-tosyl imines could be reduced directly through the β-H transferring mechanism by diethylzinc in nonpolar solvents to afford the corresponding secondary amines in excellent yields at mild conditions. The coordination of diethylzinc and N-tosyl imine was hindered by reacting in polar solvents or adding TMEDA to the reaction, it afforded ethylating product partially or exclusively.     

Effect of mild solvent post-treatments on the gas transport properties of glassy polymer membranes

This study examines the effect of treatment of defective glassy polymer membranes with a variety of vapors and liquids which have varying solvency power for the polymer. The pure-gas oxygen/nitrogen selectivities of defective, asymmetric membranes are shown to be permanently increased, in special cases, by treatment with certain solvents which have adequate solvency power to cause a critical level of swelling in the membrane skin layer. Three distinct types of membranes have been treated; asymmetric polysulfone membranes formed by dry/wet phase inversion, spin-coated poly(phenylene oxide)-ceramic composite membranes and solution-deposited polyimide-ceramic composite membranes. While the detailed fundamental processes controlling the elimination of surface defects are complex, our results suggest that plasticization of the selective skin layer, coupled with surface-tension driven cohesive forces are likely to be the key factors at play.     

Solid phase extraction GC/ECD method for the analysis of organochlorine pesticides in wildlife plasma

A gas chromatographic method for the analysis of nine organo-chlorine pesticides in wildlife plasma is described. Reversed-phase solid phase extraction is utilized to extract the organochlorine pesticides from plasma. This is followed by a normal phase solid phase extraction clean-up as the pesticides are recovered by elution with hexane:ethyl ether (1:1) and quantified by gas chromatogra-phy/electron capture detection. Method limits of detection range from 7.0–25 μg/L. The mean recovery for all pesticides is 81%.     

Extraction chromatographic studies of Ti(IV) with cyanex 301 as impregnant—Recovery from red mud

Summary A silica gel column impregnated with bis-(2,4,4-trimethylpentyl)dithiophosphinic acid has been studied for the uptake of Ti(IV). Its chemical stability has been examined and its regeneration power checked. The stoichiometry of the extracted species is proposed and the loading capacity of the column material for Ti(IV) assessed. Some important binary separations of Ti(IV) from commonly associated metal ions have been achieved and the column has been used to recover high-purity titanium from red mud, a secondary sector material.