Kinetics of the Protonation of Macrocyclic Amines in the Presence of Monovalent Cations in Aqueous Solution

Abstract

For macrocyclic bases such as: 1-aza-15-crown-5 (N15C5),1,4,10-trioxa-7,13-diazacyclopentadecan (21), 1,7,10,16-tetraoxa-4,13-diazacyclooctadecan (22) and 1, 4, 7, 13, 16-pentaoxa-10, 19-diazacycloheneicosane (23), the kinetics of deprotonation and protonation reactions in the presence of monovalent cations was studied using the temperature jump technique. For the sake of comparison, the measurements were also performed for 1,4-diazabicyclo[2,2,2]octane (DABCO) base, which does not form complexes with monovalent cations. The monovalent cations affect the temperature dependence of the kinetic parameters of deprotonation. They also affect the activation parameters, which is shown by a distribution of ΔH≠ and ΔS≠ values, but do not influence the value of ΔG≠.     

Formation Constants of Complexes of Monovalent Cations with Benzocrown Ethers in Nitromethane

The complexation reactions between the macrocyclic polyethers dibenzo-18-crown-6, benzo-18-crown-6, benzo-15-crown-5 and polyethers bearing a stilbene unit with alkali metal and silver cations have been studied conductometrically in nitromethane. The formation constants of 1 : 1 and 1 : 2 (metal : ligand) complexes were determined and found to decrease with increasing cation diameter. The stability of the stilbene crown – metal cation complexes is lower than for complexes of other investigated crown ethers with analogous cations. There seem to be some effects of double bond-silver ion interactions.     

Re-examination of the Kinetics of the Thermal Dehydroxylation of Goethite

The kinetics of thermal dehydroxylation of aluminuous goethites [1] synthesised from a ferrous salt has been re-examined using the general reaction order kinetic law. The utilised data processing was based on the procedures employed by dissolution kinetics. Recalculation of the activation energies E_A of the dehydroxylation yielded the values 130, 132, 128, and 123 kJ mol⁻¹ for pure goethite, goethite with 10, 20, and 30 mol% Al substitution, respectively. The values of E_A are in a good agreement with those given for goethite in literature. The E_A values are linearly related with the chemically bound excess H₂O/OH⁻ in the crystal lattice that is apparently influenced by Al substitution. This revised version was published online in August 2006 with corrections to the Cover Date.     

Kinetics of Thermal Transformations of Precipitated Magnetite and Goethite

The aim of the present study was to determine the kinetic equations for the thermal transformations of precipitated iron oxides and hydroxides, namely for the process of thermal dehydroxylation of goethite and consecutive of hematite crystal structure growth as well as for the oxidation of magnetite to maghemite and its thermal transformation into crystalline hematite. The investigations have been carried out using thermogravimetry (TG/DTG/DTA), X-ray powder diffractometry (XRD) and high temperature powder diffractometry (HT-XRD). This presentation contains the continuation of our earlier works. This revised version was published online in July 2006 with corrections to the Cover Date.     

化妆品中阴阳离子的快速测定及其用于化妆品鉴别的研究

用离子色谱电导检测器对黑泥类化妆品中的阴、阳离子(Na+,NH+4,K+,Mg 2+ ,Ca 2+ ,Cl-,Br-,NO-2,NO-3和SO 2- 4)进行了测定。阳离子分离条件: 阳离子交换柱ICS C25,均苯四甲酸淋洗液浓度2.0 mmol/L ,流速0.6 mL/min ;阴离子分离条件: 阴离子交换柱Shim pack IC A1,淋洗液为2.5 mmol/L 邻苯二甲酸和2.4 mmol/L 三羟基氨基甲烷,流速1.0 mL/min 。结果表明,上述10种离子在较宽浓度范围内有良好     

Coadsorption of Tetraalkylammonium Cations and Halide Anions on the Uncharged Surface of Mercury Electrode

The data on coadsorption of tetraethylammonium (Et₄N⁺), tetrapropylammonium (Pr₄N⁺), and tetrabutylammonium (Bu₄N⁺) cations with Cl^–, Br^–, and I^– anions on an uncharged mercury electrode are compared with the models of coadsorption in a common monolayer and two parallel layers. The second model is shown to be in best agreement with experimental isotherms. However, the least discrepancy between calculations and experimental results is obtained when coadsorption of mentioned cations and anions is described by the Frumkin isotherm for neutral molecules with certain effective adsorption parameters.     

Kinetics of Anodic Dissolution of a Hydrophilic Metal: Effect of the Surface Morphology

Current-voltage curves for the anodic dissolution of iron in acid chloride and sulfate solutions containing Cl^–, Br^–, and I^– ions are calculated. Calculations, made on the basis of a model of spatial separation of dissolution and passivation processes, account for the formation of pairs of kinks on stationary steps. The calculated curves quantitatively coincide with those found in literature. It is shown that portions of passivity in the curves are caused by specifically adsorbed anions, which hinder motion of kinks, while regions of nonpolarizability are connected not with the desorption of anions but with accelerated formation of vacancies on the steps, generating fresh active dissolution centers.     

Dicationic Sulfur Analogues of N‐Heterocyclic Silylenes and Phosphenium Cations

DABling with sulfur : Sulfur(II) dications can be prepared using α‐diimines to stabilize the positive charge (see scheme; DAB=diazabutadiene, Dipp=2,6‐diisopropylphenyl, OTf=CF₃SO₃). The bonding is best described as that of a N,N‐chelated sulfur(II) dication; these species represent the first sulfur‐based structural mimics of N‐heterocyclic silylene compounds and phosphenium cations.

     

离子色谱法在离子液体阴阳离子分析中的应用

离子液体作为一种新型绿色环保有机化合物,因具有饱和蒸气压低、溶解性良好以及电导率高等优异性质,而在化学化工领域中得到了较为广泛的应用,并越来越受到人们的关注。该文综述了近年来离子色谱在离子液体阴阳离子分析中的应用,对离子色谱法分析离子液体阳离子、离子液体阴离子以及同时分析离子液体阴阳离子三方面进行讨论,并对离子色谱法分析离子液体的发展趋势进行了展望。     

离子色谱法测定高氯、高钠油田回注水中的阴、阳离子及有机酸

建立了高氯、高钠油田回注水中痕量无机阴、阳离子和有机酸的离子色谱分析方法。对高钠基质中痕量阳离子的测定,选用IonPac CS12A分析柱、H2SO4溶液梯度淋洗、电导检测器检测;对高氯基质中阴离子及有机酸的测定,选用对OH-具有高选择性的高容量的IonPac AS11-HC柱、KOH梯度淋洗、电导检测器检测。在优化的梯度淋洗条件下,高氯或高钠的存在不影响痕量阴离子或阳离子的测定。该方法具有良好的线性(r=0.9926~0.9990)和精密度(测定组分峰面积的相对标准偏差(n=7)在8.0%以下),回收率     

毛细管区带电泳同时测定化妆品中的阴阳离子

Natural Sea Beauty系列化妆品富含来自Dead Sea水中的矿物质,对皮肤有较好的治疗和滋养作用.本文采用毛细管区带电泳的技术,电迁移双端进样,5 mmol/L咪唑-2 mmol/L硝酸为背景电解质,以富马酸调至pH 4.1,UV间接测定法(214nm),在6min内同时检测了化妆品中的阴阳离子(K⁺、Na⁺、Ca²⁺、Mg²⁺、Cl^-、Br^-),与离子色谱法所得结果进行了对照.此方法可为鉴别不同品牌的化妆品提供一定的依据.     

基于课程标准的教学——以常见阴、阳离子的检验为例

以常见的阴、阳离子的检验为例，研究了如何实施基于标准的教学。校本教材的开发为标准、教材、教学、评价的一致性提供保障；以学生应知的和能做的驱动课堂活动；根据达成标准应有怎样的质量表现，试卷编制先于教学设计。课堂上，“教”“学”双方都明确学习目标，教师提供多种策略来满足学生多样的学习需要，如提供工具，搭建脚手架，并以“微”研究性学习的方式展开教学，给学生提供了充分的进步空间。     

单柱离子排斥-阳离子交换色谱法测定酸雨组分

采用单柱离子色谱系统和电导检测的方法,首次以ＤＬ－苹果酸－甲醇水溶液为淋洗液,简便、有效地同时分离、检测了溶液ＳＯ＾－２４、Ｃｌ＾－、ＮＯ＾－３、Ｆ＾－、Ｎａ＾＋、ＮＨ＾＋４、Ｋ＾＋、Ｍｇ＾２＋、Ｃａ＾２＋９种离子。研究了ＤＬ－苹果酸浓度、甲醇浓度、流速和温度对各离子保留时间的影响。方法用于上海部分地区降水中的阴、阳离子分析,并与其它方法对比,结果良好。     

Cover Picture: Dicationic Sulfur Analogues of N‐Heterocyclic Silylenes and Phosphenium Cations (Angew. Chem. Int. Ed. 12/2009)

Highly reactive electrophilic compounds centered around multicationic main‐group elements are notoriously difficult to isolate. In the Communication on page 2210 ff., P. J. Ragogna and co‐workers describe the synthesis and characterization of salts of sulfur(II) dications stabilized by two chelating nitrogen atoms. These species are the first sulfur‐based analogues of N‐heterocyclic silylene compounds and are the most recent addition to the family of compounds featuring divalent p‐block elements. Mitch Zimmer is acknowledged for the cover design.

     

双通道离子色谱法同步检测DOPO中的无机离子

以氯仿溶解9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO),离心取清液,自动进样器-双通道离子色谱法同步检测DOPO中的无机阴阳离子,采用自动进样器与双通道同步进行,大大缩短了分析时间,离子保留时间的相对标准偏差RSD(n=6)在0.07%～0.18%,峰面积的RSD(n=6)在0.43%～0.88%,重现性好。3种离子的平均回收率在94.87%～98.30%,结果令人满意。     

单柱阴离子色谱法同时测定无机阴离子、无机阳离子和有机酸的研究

自Small等首次采用双柱阴离子色谱法测定无机阴离子以来,单柱阴离子色谱法已被用于测定无机阴离子、有机酸,并利用金属阳离子与EDTA形成的阴离子配合物分离测定阳离子。但用单柱阴离子色谱法同时测定无机阴离子、无机阳离子和有机酸尚未见报道。本文采用EDTA为淋洗液的单柱阴离子色谱法研究了无机阴离子、无机阳离子和有机酸的同时分析测定。     

Kinetics and Substrate Selectivity of the Oxidation of Saturated Hydrocarbons by Adamantyl Cations in Sulfuric Acid

It was shown that at 70 °C sulfuric acid ([H₂SO₄] > 85 wt.%) solutions of 1-hydroxyadamantane and the solutions obtained in the reaction of adamantane with concentrated sulfuric acid oxidize saturated hydrocarbons (RH). Data on the kinetics, selectivity, kinetic isotope effect, and the effect of the acidity of the medium on the oxidation rate of RH indicate cleavage of the C—H bond in the substrate at the rate-determining stage and the direct participation of adamantyl carbocations.     

Activation of CS2 and CO2 by Silylium Cations

The hydride-bridged silylium cation [Et₃Si−H−SiEt₃]⁺, stabilized by the weakly coordinating [Me₃NB₁₂Cl₁₁]⁻ anion, undergoes, in the presence of excess silane, a series of unexpected consecutive reactions with the valence-isoelectronic molecules CS₂ and CO₂. The final products of the reaction with CS₂ are methane and the previously unknown [(Et₃Si)₃S]⁺ cation. To gain insight into the entire reaction cascade, numerous experiments with varying conditions were performed, intermediate products were intercepted, and their structures were determined by X-ray crystallography. Besides the [(Et₃Si)₃S]⁺ cation as the final product, crystal structures of [(Et₃Si)₂SMe]⁺, [Et₃SiS(H)Me]⁺, and [Et₃SiOC(H)OSiEt₃]⁺ were obtained. Experimental results combined with supporting quantum-chemical calculations in the gas phase and solution allow a detailed understanding of the reaction cascade.     

Analysis of wastewater for anionic and cationic nutrients by ion chromatography in a single run with sequential flow injection analysis

To prevent nutrient enrichment and, hence the undesirable ecological impacts, the nutrients monitored in wastewater samples include two anionic species, i.e., nitrate and orthophosphate, and a cationic species, ammonium. Ion chromatography (IC) is one of the popularly used techniques for determinations of nitrate and phosphate in these samples, whereas determination of ammonium in wastewater samples is typically done using manual or automated wet chemistry, e.g., flow injection analysis (FIA). We have developed a sequential IC–FIA method, using Lachat’s QC8000 IC system, which allows determinations of nitrate, phosphate and ammonia in a single injection. In this system, a QuikChem Small Suppressor cartridge is regenerated in between the samples. A sample is injected while leaving the suppressor off-line. Ammonium, a cation, elutes in the void volume of an anion-exchange column. The unsuppressed column effluent, exiting the conductivity flow cell, up to this point is used for FIA determination of ammonia. When ammonia exits the conductivity flow cell, a fully regenerated suppressor is brought in-line for conductometric detection of the anions. Analog data are simultaneously acquired from colorimetric and conductometric detectors, for the cationic and anionic nutrients, respectively. The method is accurate with spike recoveries in wastewater samples ranging from 91% for nitrate to 114% for chloride. It is precise with RSD values, for replicate analyses (n=7) of a mid-range standard, ranging from 0.4% for phosphate to 1% for nitrate.