Regioselective Iodination of Chlorinated Aromatic Compounds Using Silver Salts

The iodination of chlorinated aromatic compounds using Ag₂SO₄/I₂, AgSbF₆/I₂, AgBF₄/I₂, and AgPF₆/I₂ offers access to iodoarenes that are valuable intermediates in organic synthesis. Specifically, iodination of phenols, anisoles, and anilines with a 3,5-dichloro substitution pattern preferentially yielded the ortho, para, and para iodinated product, respectively. In the case of chlorobenzene and 3-chlorotoluene, AgSbF₆/I₂, AgBF₄/I₂, and AgPF₆/I₂, but not Ag₂SO₄/I₂, selectively introduced the iodine in para position to the chlorine substituent.     

二茂铁-离子液体修饰碳糊电极的研制

以室温离子液体N-辛基吡啶六氟磷酸盐为粘合剂与二茂铁和石墨粉相混合制备了一种新型二茂铁-离子液体修饰碳糊电极。以该电极为工作电极,采用循环伏安法、计时安培法研究了多巴胺(DA)在该糊电极上的电化学行为。实验结果表明:该电极在pH 5.0的乙酸-乙酸钠缓冲溶液中,外加电压0.8 V条件下,灵敏度最高。电流增量与DA浓度在1.0×10-5～1.0×10-3 mol/L范围内呈良好的线性关系,检出限为5.0×10-6 mol/L(S/N=3)。     

A new 1,3-dibutylimidazolium hexafluorophosphate ionic liquid-based dispersive liquid–liquid microextraction to determine organophosphorus pesticides in water and fruit samples by high-performance liquid chromatography

The paper described a new ionic liquid, 1,3-dibutylimidazolium hexafluorophosphate, as extraction solvent for extraction and preconcentration of organophosphorus pesticides (fenitrothion, parathion, fenthion and phoxim) from water and fruit samples by dispersive liquid–liquid microextraction combined with high-performance liquid chromatography. The effects of experimental parameters, such as extraction solvent volume, disperser solvent and its volume, extraction and centrifugal time, sample pH, extraction temperature and salt addition, on the extraction efficiency were investigated. An extraction recovery of over 75% and enrichment factor of over 300-fold were obtained under the optimum conditions. The linearity relationship was also observed in the range of 5–1000 μg L⁻¹ with the correlation coefficients (r²) ranging from 0.9988 to 0.9999. Limits of detection were 0.01–0.05 μg L⁻¹ for four analytes. The relative standard deviations at spiking three different concentration levels of 20, 100 and 500 μg L⁻¹ varied from 1.3–2.7, 1.4–1.9 and 1.1–1.7% (n = 7), respectively. Three real samples including tap water, Yellow River water and pear spiked at three concentration levels were analyzed and yielded recoveries ranging from 92.7–109.1, 95.0–108.2 and 91.2–108.1%, respectively.     

离子液体[bmim][PF6]与乙腈混合体系中的激光光解研究

以蒽醌(AQ)作为探针分子,利用激光光解技术研究了咪唑型离子液体1-丁基-3-甲基咪唑六氟化磷([bmim][PF6])与乙腈(MeCN)混合体系中的光化学反应行为.研究结果表明,离子液体[bmim][PF6]自身可与激发三线态的蒽醌分子(3AQ*)进行反应,且表观反应速率常数随着[bmim][PF6]/MeCN比例的不同呈现特殊规律性的变化.在离子液体的摩尔分数(xRTIL)为0.06处观察到一个明显的临界点.当xRTIL＜0.06时,表观速率常数随xRTIL的增大而增大;而当xRTIL＞0.06时,表观速率常数随xRTIL的增大而减小.文章给出了[bmim][PF6]/MeCN混合体系中激光诱导化学反应的动力学常数,并初步推测了其反应机理,进一步揭示了离子液体[bmim][PF6]的一些新的光化学特性.     

库仑滴定法测定六氟磷酸锂中微量水分

基于与卡尔-菲休试剂的反应用库仑滴定法测定了六氟磷酸锂中的微量水分.对同一试样的不同进样量(0.5～5.0 mL 共 10 份)按所提出方法对其水分进行了测定,所得结果在26.3～27.9 μg·g-1 之间,平均值为 27.4μg·g-1,相对标准偏差为 0.72%.     

Crystallographic report: Thallium(18‐crown‐6) hexafluorophosphate, [Tl(18‐crown‐6)](PF6)

Thallium(18‐crown‐6) hexafluorophosphate was prepared and its structure was determined by X‐ray diffraction analysis. The Tl⁺ ion is surrounded by six oxygen atoms of 18‐crown‐6 and three fluorine atoms of , forming a sandwiched structure. If the three Tl–F interactions were considered significant, the coordination number in the title compound would be nine. Copyright © 2003 John Wiley & Sons, Ltd.     

‘Bis-ornithine’ (2,2-bis(aminopropyl)glycine): a new tetravalent template for assembling different functional peptides

Synthesis of bis-ornithine, a new C^α,α-disubstituted α-amino acid bearing orthogonally protected α and δ amine groups is reported. Bis-ornithine (bisOrn) and dipeptides containing bis-ornithine have been synthesized in solution up to multigram scale. As a first example, one of these compounds Boc-βAla-bisOrn(Alloc)₂-OH has been attached to a solid support and used as template for the synthesis of a symmetrical assemblage of peptides.     

Study of the Ion Channel Behavior of Didodecyldimethylammonium Bromide Formed Bilayer Lipid Membrane Stimulated by PF6

Bilayer lipid membranes(BLM) formed from didodecyldimethylammonium bromide were made on the freshly exposed surface of a galssy carbon(GC) and were demonstrated by the acimpedance spectroscopy.The ion channels of membrane properties induced by PF6^- were studied by the cyclic voltammetric methods.Experimental results indicated that the ion channel of BLM was open in the presence of the PF6^- due to the interaction of PF6^- with the BLM,while it was switched off in the absence of PF6^-.Because the ion channel behavior was affected by the concentration of PF6^-,a sersor for PF6^- can be developed.     

Low-temperature performance of Li-ion cells with a LiBF<Subscript>4</Subscript>-based electrolyte

The effect of LiBF₄ on the low-temperature performance of a Li-ion cell was studied by using a 1:1:1 (wt) EC/DMC/DEC mixed solvent. The results show that the LiBF₄-based electrolyte has a 2- to 3-fold lower ionic conductivity and shows rather higher freezing temperature compared with a LiPF₆-based electrolyte. Owing to electrolyte freezing, cycling performance of the Li-ion cell using LiBF₄ was significantly decreased when the temperature fell below –20 °C. However, impedance data show that at –20 °C the LiBF₄ cell has lower charge-transfer resistance than the LiPF₆ cell. In spite of the relatively lower conductivity of the LiBF₄-based electrolyte, the cell based on it shows slightly lower polarization and higher capacity in the liquid temperature range (above –20 °C) of the electrolyte. This fact reveals that ionic conductivity of the electrolytes is not a limitation to the low-temperature performance of the Li-ion cell. Therefore, LiBF₄ may be a good salt for the low-temperature electrolyte of a Li-ion cell if a solvent system that is of low freezing temperature, high solubility to LiBF₄, and good compatibility with a graphite anode can be formulated. Electronic Publication