质谱离子源技术用于电化学反应机理研究的进展

电化学反应是连续的动态变化过程,伴随着瞬时中间体和复杂结构物质的产生,因此,精确而有效地捕捉反应过程中的一系列产物,有助于准确推导其电化学反应机理,进而优化反应条件,提高反应效率.目前,主流的电化学在线监测技术包括光谱法、循环伏安法和线性极化曲线等,这些方法能够胜任反应过程中大部分物质的结构及组成变化检测,然而,为了更加系统和精确地掌握电化学反应过程中所有产物的信息,仍需进一步拓展实时、原位反应监测技术.质谱具有灵敏度高、选择性好、分析速度快、可以结构解析等特点,是一种理想的电化学反应研究手段.近年来,采用质谱法研究电化学反应机理的报道越来越多,尤其是采用以电喷雾离子源（Electrospray Ionization,ESI）及其衍生离子源为代表的常压离子源对电化学反应过程进行实时、原位监测已经成为研究热点.本综述主要介绍了近期发表的电化学-质谱联用技术,详细描述了其针对不同类型电化学反应监测要求而设计和开发的电化学离子源装置.     

同轴式电化学电喷雾质谱离子源研究蒽电化学衍生十二胺

提出一种同轴式电化学电喷雾质谱离子源, 用于电化学与质谱分析在线联用. 离子源结构简单, 造价低廉, 容易制作. 离子源内的电化学反应器工作在两电极模式, 利用自制的悬浮在电喷雾高压上的无线电化学工作站控制. 使用二苯基蒽或三乙胺的乙腈溶液作为分析物, 全面测试了离子源的性能, 包括电势控制精度、电化学转化率、响应时间和抗污能力等. 测试溶液添加浓度约10 mmol·L^-1的银盐作为电解质和去极剂, 将溶液电阻降至250 Ω, 提高了在线联用的电势控制精度. 所测二苯基蒽溶液流动时的伏安曲线与常规三电极体系的循环伏安曲线基本一致. 在3.6 μL·min^-1的流速下, 离子源的响应时间不超过5 s, 三乙胺的电化学转化率高达77%. 利用此离子源, 研究了蒽的电化学衍生反应, 衍生试剂为十二胺. 蒽作为一种非极性物质, 不能为常规电喷雾质谱检测. 而利用电化学电喷雾质谱离子源, 蒽首先发生电化学氧化反应, 进而与衍生试剂作用生成各种极性物质, 被电喷雾质谱检测. 依据质谱检测到的主要反应产物的相对分子质量与结构提出了衍生反应的机理, 有助于理解蒽的复杂电化学行为.     

在线电化学／分离分析方法

对电化学衍化之后续以分离分析手段的在线联用方法作了 概述，讨论了电化学／质谱，在化学。高效液相色谱／质谱，电质学／质谱／质谱，电化学／高效液相色谱和电化学／气相色谱等的研究与应用，展 望了这个领域的发展前景。     

电化学生物传感器在污水分析及污水流行病学中的应用进展

近年来,污水流行病学（wastewater-based epidemiology, WBE）已被证明是用来监测社区毒品滥用和公共健康的一种有效评估方法,该方法通过定量分析指定社区污水回收站中污水的药物残留或者代谢物来反推社区中人们对毒品的消耗量并结合指定社区的人口数量对其进行归一化处理. 电化学生物传感器具有响应时间快、成本低、分析样品需求量小、数据分辨率高以及能够现场快速测试等特点,已被广泛应用于疾病快速诊断、环境污染监测、食品安全以及毒品检测等领域. 液相色谱-质谱联用是分析污水中的毒品及其代谢物的主要方法,但随着传感技术尤其是电化学传感器近来的快速发展,也开始被用于研究污水传染病学并可实现现场快速测量. 本文综述了电化学生物传感器在污水中无机污染物（如重金属）、有机污染物（如农药、毒品）、生物分子（如 DNA）以及细菌等微生物分析中的最新进展,同时还论述了目前电化学传感器技术在污水流行病学领域的应用和未来所面临的主要挑战.     

质谱技术在反应监测中的发展和应用

质谱因具有分辨率高、 灵敏度好、 响应快速以及结构鉴定能力强等特点, 近年来在反应监测研究领域应用广泛. 本文介绍了基于质谱的经典在线直接采样实时监测方案; 综合评述了常压质谱离子化技术在反应监测领域的发展和应用, 主要包括基于常压质谱的快反应监测、 微滴加速在长时间反应研究中的应用, 以及其它常压质谱在反应监测中的应用; 并对质谱在反应监测研究领域面临的挑战和发展趋势进行了总结和展望.     

电化学质谱在锂-氧电池研究中的应用

质谱技术与电化学方法相结合,能原位或在线检测电化学反应的中间产物和最终产物,利于深入研究电极反应机理. 本文结合作者应用电化学质谱研究锂-氧电池反应机理的科研背景,综述了目前该技术在研究锂-氧电池体系中的电解液、电极材料和催化剂的进展情况,此外还介绍了电池体系中的不可逆副反应对电池充放电过程的影响.     

毛细管电泳技术在氨基酸分析中的研究进展

对毛细管电泳技术在氨基酸分析中的研究进展进行了综述,分析了直接法和衍生法对氨基酸进行分析的优缺点,详细叙述了毛细管电泳中的紫外、激光诱导荧光、电化学及质谱等检测方法在氨基酸分析中的应用,并重点总结了毛细管电泳在手性氨基酸分离中的应用.     

高通量药物筛选现代检测技术研究进展

高通量药物筛选是发现创新药物的重要技术途径.高通量筛选结果必须通过适当的检测方法才能反映出来,检测技术是实现高通量药物筛选的基础.本文综述了近年来有关光学分析、色谱分析、热分析、电化学分析、质谱、核磁共振等现代检测技术在高通量药物筛选研究中的进展.     

微流控玻璃芯片毛细管电泳鞘流型紫外光度检测系统

目前,微流控芯片分析系统中常用的检测方法有激光诱导荧光检测、质谱、化学发光、电化学和光度法等.其中应用最多的是激光诱导荧光检测器,但其所测样品大部分需要衍生.     

电位调控电解质迁移过程的ToF-SIMS可视化研究

电子转移过程是电化学反应的核心,而构成电极反应的前提则是电活性物质在电极表面的迁移扩散.对电位调控下电解质迁移过程的观测,有助于对电极表面电化学反应机理进行更加深入的理解.以氯化钾溶液在金电极表面的迁移过程为研究模型,通过制备可用于高真空环境中的微流控电化学池,实现液体电化学飞行时间-二次离子质谱（ToF-SIMS）联用,用于氯化钾溶液在不同电极电位条件下迁移过程的实时监测.通过化学成像呈现不同电位下氯化钾溶液在金电极附近的分布情况,观测到K⁺与H⁺（H₂O）_n在施加-0.30 V电压后,在电极附近存在聚集,施加0.70 V电压后,电极附近处,两物种浓度明显降低.通过液体电化学ToF-SIMS联用,可实现电极调控作用下电解质迁移过程的原位监测,展现了带电粒子在电场作用下的宏观迁移过程,为电极-电解质界面的原位实时监测提供可视化的研究手段.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.