氯代甲苯双电荷离子的单分子解离反应研究

研究了在70 eV电子轰击电离条件下，氯代甲苯及氯化苄产生的双电荷离子[C_7H_7Cl]~(2＋)、[C_7H_6Cl]~(2＋·)和[C_7H_5Cl]~(2＋)为母体的两种类型单分子解离反应．主要讨论了亚稳双电荷离子的异构化反应、失H解高的“偶电子规则”以及单分子电荷分离过渡态的结构．     

Recent advances in the formation of ultrathin polymeric membranes for gas separations

During the past 20 years membrane systems have been applied to a limited number of commercial gas separations. To further advance membrane-based gas separations, current research efforts focus on optimization of (i) membrane materials, (ii) membrane structures and (iii) membrane system design. In this overview, recent developments in the formation of high-performance gas separation membranes are discussed. The gas separation properties of state-of-the-art integrally skinned asymmetric membranes and thin-film composite membranes are summarized. Future directions for the preparation of advanced gas separation membranes are highlighted.     

Effect of p-tert-Butylcalix[4]arene Fitted with Phosphinoyl Pendant Arms as Synergistic Agent in the Solvent Extraction and Separation of Some Trivalent Lanthanoids with 4-Benzoyl-3-methyl-1-phenyl-5-pyrazolone

The synergistic solvent extraction of five selected lanthanoid ions (La³⁺, Nd³⁺, Eu³⁺, Ho³⁺ and Lu³⁺) with a 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone(HP) and the 5,11,17,23-tert-butyl-25,26,27,28-tetrakis(dimethylphosphinoylmethoxy)calix[4]arene, (S) in CHCl₃ has been studied. It was found that in presence of this phosphorus-containing calix[4]arene the lanthanoids have been extracted as LnP₃ · S. On the basis of the experimental data, the values of the equilibrium constants have been calculated. The influence of the synergistic agent on the extraction process has been discussed. A synergistic effect of almost three orders of magnitude occurs in the extraction of Ln(III) with mixture of HP and S. The values of the separation factors (S.F.) between the adjacent elements have been evaluated. On the basis of the IR and NMR spectra the stoichiometry and the structure of the solid complexes of Eu(III) with HP and Eu(III) with HP and S were proposed.     

Indirect thermal lens detection for capillary electrophoresis

Thermal lens detection with a 325.0 nm He-Cd excitation laser is used for thermooptical indirect detection in combination with the capillary electrophoretic separation of organic anions. The optimization of indirect thermooptical detection is discussed. With Mordant Yellow 7 (an azo dye) chosen as a probe ion limits of detection for 1-heptane-, 1-pentane-, 1-butane-, 1-propanesulfonic, and acetic acid at a level of n × 10⁻⁷ M were achieved with a separation electrolyte containing 50 μM of the probe ion and 5 mM Tris pH 9.90. A further increase in the detection sensitivity (twofold decrease in the limit of detection ) was obtained with a separation electrolyte containing a volume fraction of 20% acetonitrile.     

Resolution of (+/-)-ibuprofen using (-)-brucine as a chiral selector by thin layer chromatography

The enantiomeric resolution of (+/-)-ibuprofen into its enantiomers was achieved by TLC on silica gel plate using optically pure (-)-brucine as a chiral selector and acetonitrile-methanol (5:1, v/v) as the solvent system. Spots were located in an iodine chamber. The detection limit was 4.9 microg. The effect of concentration of the chiral selector, temperature and pH on resolution has been studied.     

Enatiomeric analysis of simendan by CE with beta-CD as chiral selector compared with CMPA-HPLC

The chiral separation of simendan enantiomers using capillary electrophoresis was studied with beta-cyclodextrin (beta-CD) as chiral selector. The influences of the concentration and pH of borate buffer solution, beta-CD concentration and methanol content in the background electrolyte were investigated. These factors were compared with those in an HPLC with beta-CD as chiral mobile phase additive (CMPA-HPLC). The quantification properties of the developed CE method were examined. A baseline separation of simendan enantiomers was achieved in the background electrolyte of 20 mmol/L borate buffer (pH 11.0) containing 12 mmol/L beta-CD-methanol (50:50 in volume ratio). The CE method is comparable with CMPA-HPLC in chiral resolution, although the optimal pH in CE (11.0) is much higher than that (6.0) in CMPA-HPLC. This chiral CE method is applicable to the quantitative ananlysis and enantiomeric excess value determination of L-simendan.     

Determination of D- and L-amino acids in biological samples by two-dimensional column liquid chromatography

Summary A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citratesodium chloride buffer. Enantioseparation is by subsequent injection of 3 l heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity.     

Retention,enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column

Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an ₁-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.     

Synthesis and properties of chiral ammonium-based ionic liquids

New chiral ammonium-based ionic liquids containing the (1R,2S,5R)-(-)-menthyl group can be easily and efficiently prepared under ambient conditions. The preparation and characterization of trialkyl[(1R,2S,5R)-(-)-menthoxymethyl]ammonium salts is reported. The salts have been demonstrated to be air- and moisture-stable under ambient conditions and can be readily used in a variety of standard experimental procedures. The single-crystal X-ray structure of butyldimethyl[(1R,2S,5R)-(-)-menthoxymethyl]ammonium chloride has been determined. The chiral, room-temperature ionic liquids have been characterized by physical properties such as specific rotation, density, viscosity, thermal degradation, and glass transition temperature. Trialkyl[(1R,2S,5R)-(-)-menthoxymethyl]ammonium chloride prototype ionic liquids have also been found to exhibit strong antimicrobial and high antielectrostatic activities.     

First synthesis of enantio-uracil dinucleotide, comparison of physicochemical properties of their enantiomers, and separation by chiral column chromatography

Enantio-uracil dinucleotide 5, which consists of two l-uridylic acids and one pyrophosphate, was synthesized for the first time in our laboratory. Benzolyated l-uridine was prepared by a stereoselective glycosylation of silylated uracil with l-1-O-acetyl-2,3,5-tri-O-benzoylribose (l-ABR 7). After deprotection, l-uridine 9 was converted to P¹,P⁴-di(l-uridine 5′-) tetraphosphate tetrasodium salt (l-UP₄U 5) by treatment of l-UMP morpholidate 10c with triethylammonium pyrophosphate (TEA-PPi 11b). Spectral data of synthesized l-UP₄U 5 are given in the references. All spectral data were identical with those of UP₄U 3 except the specific rotation, which showed a positive value compared to UP₄U 3 having a negative value. Furthermore, the separation by chiral column chromatography was investigated.