共查询到19条相似文献,搜索用时 78 毫秒
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通过氯甲基化反应,将冠醚二苯并-18-冠-6(DBC)转变为氯甲基化的冠醚(CMDBC),使交联聚乙烯醇(CPVA)微球表面的羟基与CMDBC之间发生亲核取代反应,从而实现冠醚的固栽化,制得了固载有冠醚的功能微球DBC-CPVA.在建立了冠醚DBC固载量测定方法(溴百里香酚蓝-固相萃取法)的基础上,重点研究了主要因素对DBC固栽化过程的影响规律.结果表明:反应温度与溶剂性质对DBC在CPVA微球上的固载化反应有较大的影响,在70℃极性较强的N,N-二甲基甲酰胺(DMF)溶剂中,可制得冠醚DBC固载量为1.72 mmol/g的DBC-CPVA功能微球. 相似文献
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应用液/液界面微电极对二苯并18-冠-6(DB18-C-6)辅助推动Ba~(2+)在1,2-二氯乙烷/水(DCE/W)界面转移的电化学过程进行了详细探讨,证明该过程遵循TIC机理,是受扩散控制的可逆过程。通过转移电流和反应物浓度之间的线性关系,测定了Ba~(2+)以及用其它方法难以测定的DB18-C-6。 相似文献
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将有机相和水相分别灌入双通道玻璃微米管θ管中的一个管中,利用θ管表面的亲水特征,在灌有有机相的微米管口附近形成微-液/液界面.利用循环伏安法研究了电荷在这种微-液/液界面上的转移反应,包括简单离子(四甲基铵离子TMA+)转移、加速离子转移(DB18C6加速K+离子)和电子转移(二茂铁/铁氰化钾+亚铁氰化钾体系)反应过程.结果表明,这种双通道微米管所得到的微-液/液界面具有不对称扩散场的特性.此装置是目前最简单的可用于研究液/液界面上的电荷转移反应的装置之一,即所谓的可进行"无溶液"液/液界面电化学及电分析化学研究的装置. 相似文献
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以二甘醇和邻苯二酚为原料制得二苯并-18-冠-6;以多聚磷酸为催化剂和溶剂,将二苯并-18-冠-6与叔丁醇反应实现叔丁基化;利用正庚烷重结晶对叔丁基化反应产物进行纯化,得到4,4′-二叔丁基二苯并-18-冠-6和4,5′-二叔丁基二苯并-18-冠-6两种对称的二叔丁基二取代苯并冠醚产品.利用红外光谱和核磁共振谱表征了二叔丁基二取代苯并冠醚产物的结构。 相似文献
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在交联聚乙烯醇(CPVA)微球表面固载冠醚二苯并-18-冠-6 (DBC), 从而制得三相相转移催化剂DBC-CPVA; 在此基础上, 以苯甲酸钾与溴代正丁烷的酯化反应为模型反应体系, 重点研究固体催化剂DBC-CPVA的相转移催化性能, 考察主要因素对液-固-液三相相转移催化反应的影响. 结果表明, 在本研究体系中, 水相中的苯甲酸钾与有机相中的溴代正丁烷可顺利地发生酯化反应, 这一结果显示出固载于DBC-CPVA表面的DBC与K+离子形成的络合物阳离子, 能有效地将苯甲酸根负离子转移至有机相, 使酯化反应顺利地进行. 有机相的极性越强, 酯化反应的速率越快, 溴代正丁烷的转化率越高; 有机相与水相体积比为1:4时, 酯化反应具有最大的速率, 溴代正丁烷的转化率可达70%. 固体催化剂DBC-CPVA循环使用8次, 催化活性保持稳定. 相似文献
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采用玻璃微米管支撑的液/液界面通过循环伏安法(CV)研究了二环己基-18冠6(DCH18C6)加速Sr2+在水/1,2-二氯乙烷(W/DCE)界面上的转移反应,考察了DCH18C6加速Sr2+在W/DCE界面转移的影响因素,如DCH18C6和Sr2+浓度等,并求算其络合物的稳定常数。实验结果表明,Sr2+与DCH18C6发生的是一个1:1的扩散控制的界面络合转移过程,其络合常数β为5.31×1023。本研究可为理解溶剂萃取Sr2+行为提供基础理论数据。 相似文献
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Facilitated ion transfer reactions across oilwater interfaces based on different competitive ligands
In this paper, we present the general equations for facilitated ion transfer reactions across oilwater interfaces based on different competitive ligands, i.e., the transfer of a cation that, under given conditions, is assisted by a mechanism that involves ligands exchange. The obtained results agree with the general voltammetric criteria reported by Girault and co-workers [F. Reymond, P.-A. Carrupt, H.H. Girault, J. Electroanal. Chem. 449 (1998) 49; F. Reymond, G. Lagger, P.-A. Carrupt, H.H. Girault, J. Electroanal. Chem. 451 (1998) 59] for the facilitated transfer of a unique cation assisted by a neutral ligand. The equations reported in this paper grant to simulate the system under all possible conditions. The results are interpreted for different zones determined by the ratio of cation and ligand concentrations. 相似文献
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The transfer of the protonated forms of heptylamine, octylamine, decylamine, procaine and procainamide facilitated by dibenzo-18-crown-6 from water to a solvent polymeric membrane has been investigated by using cyclic square wave voltammetry. The experimental voltammograms obtained are in good agreement with theoretical predictions. The values of the standard ion transfer potential, complexation constant and diffusion coefficient in water have been obtained from these experiments, and have been used to draw some conclusions about the lipophilicity of these species and the relative stability of the organic ammonium complexes with dibenzo-18-crown-6. The results have been compared with those provided by linear sweep voltammetry. Calibration graphs were obtained with both techniques. An interesting chronoamperometric method for the determination of the diffusion coefficient of the target ion in the membrane has been developed and applied to all these protonated amines. 相似文献
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端烯基液晶冠醚推动钠离子在微液/液界面的转移 总被引:1,自引:0,他引:1
用循环伏安法研究新型载体端烯基液晶冠醚推动钠离子的转移,结果表明,钠离子的转移由扩散控制.探讨了影响钠离子转移的因素,如端烯基液晶冠醚和钠离子的浓度等.求算出端烯基液晶冠醚在1,2-二氯乙烷中的扩散系数为(2.61±0.12)×10-6cm2/s,端烯基液晶冠醚和钠离子在1,2-二氯乙烷中所形成的配合物稳定常数lgβo=5.7. 相似文献
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In this work, the analytical use of facilitated ion transfer of catecholamines by dibenzo‐18‐crown‐6 was investigated at the water/1,6‐dichlorohexane interface using electrochemical methods (cyclic and square wave voltammetry). The experimental conditions for the analytical determination of noradrenaline and dopamine were established and detection limits of 1.7 and 0.35 µM were obtained, respectively. The effect of excess ascorbic acid on the transfer and detection of the two catecholamines was investigated. The selectivity coefficients obtained for dopamine and noradrenaline in the presence of ascorbic acid were 3.5×10?4 and 2.5×10?3, respectively. 相似文献
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Kinetically controlled electro-oxidation of a redox probe dissolved in the organic solvent, which is interposed between an electrode surface and an aqueous solution as a thin layer, is analyzed theoretically. It is demonstrated that the electrode reaction rate constant can be measured by the variation of scan rate in linear scan voltammetry both in the absence and in the superfluity of the supporting electrolyte dissolved in the film.Dedicated to Professor Dr. Alan M. Bond on the occasion of his 60th birthday 相似文献
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Yoshihiro Kitatsuji Zenko Yoshida Hiroshi Kudo Sorin Kihara 《Journal of Electroanalytical Chemistry》2002,520(1-2)
A novel electrochemical method based on controlled-potential electrolysis has been developed for the elucidation of the ion transfer at the interface between two immiscible electrolyte solutions (ITIES). A relationship between the applied interfacial potential (Eapp) and the amount of the ion transferred (Atr) was investigated after an electrolytic equilibrium was attained by controlled-potential electrolysis. The Atr was determined chemically or radiometrically instead of by current measurement. It was found that (i) controlled-potential electrolysis was applicable to the study of the transfer of such hydrophilic ions as transition metal ions which gave no appreciable current within the potential window in voltammetry or polarography at ITIES, (ii) controlled-potential electrolysis in combination with a sensitive analytical method enabled a study of the transfer reaction of an ion of very dilute concentration, and (iii) even when the transfer reaction of an ion was irreversible or quasi-reversible, a standard ion transfer potential could be determined by controlled-potential electrolysis without using a kinetic parameter. The controlled-potential electrolysis method developed was applied to the transfer reactions of actinide ions such as UO2 2+ and Am3+ from aqueous solution to nitrobenzene solution in the absence or presence of an ionophore facilitating the transfer. The Gibbs energy for the transfer of actinide ion and a stability constant of the complex between an actinide ion and the ionophore in nitrobenzene solution were determined from log D versus Eapp plots (D the ratio of the concentration of the ion in nitrobenzene solution to that in aqueous solution). The feasibility of controlled-potential electrolysis as a method for electrolytic separation of actinide ions is discussed. 相似文献
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CHEN Yong YUAN Yi ZHANG Meiqin LI Fei SUN Peng GAO Zhao & SHAO YuanhuaState Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun China College of Chemistry Molecular Engineering Peking University Beijing China 《中国科学B辑(英文版)》2004,47(1)
Facilitated ion transfer reactions of 20 amino acids with dibenzo-18-crown-6 (DB18C6) at the water/1,2-dichloroethane (W/DCE) interfaces supported at the tips of micro- and nano-pipets were investigated systematically using cyclic voltammetry. It was found that there were only 10 amino acids, that is, Leu, Val, lie, Phe, Trp, Met, Ala, Gly, Cys, Gin (in brief), whose protonated forms as cations can give well-defined facilitated ion transfer voltammograms within the potential window, and the reaction pathway was proven to be consistent with the transfer by interfacial complexation/dissociation (TIC/TID) mechanisms. The association constants of DB 18C6 with different amino acids in the DCE (β0), and the kinetic parameters of reaction were evaluated based on the steady-state voltammetry of micro- or nano-pipets, respectively. The experimental results demonstrated that the selectivity of complexation of protonated amino acid by DB18C6 compared with that of alkali metal cations was low, which can be attribu 相似文献
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Failitated ion transfer reactions of 20 amino acids with dibenzo-18-crown-6 (DB18C6) at the water/1,2-dichloroethane (W/DCE)
interfaces supported at the tips of micro- and nano-pipets were investigated systematically using cyclic voltammetry. It was
found that there were only 10 amino acids, that is, Leu, Val, lle, Phe, Trp, Met, Ala, Gly, Cys, Gln (in brief), whose protonated
forms as cations can give well-defined facilitated ion transfer voltammograms within the potential window, and the reaction
pathway was proven to be consistent with the transfer by interfacial complexation/dissociation (TIC/TID) mechanisms. The association
constants of DB 18C6 with different amino acids in the DCE (β°), and the kinetic parameters of reaction were evaluated based
on the steady-state voltammetry of micro- or nano-pipets, respectively. The experimental results demonstrated that the selectivity
of complexation of protonated amino acid by DB18C6 compared with that of alkali metal cations was low, which can be attributed
to the vicinal effect arising from steric hindrance introduced by their side group and the steric bulk effect by lipophilic
stabilization. Moreover, the association constants and the standard rate constants for different amino acids showed good correlations
with their hydrophobicity (π), except Gly and Met, which inferred that the selectivity of such heterogeneous complex reaction for different amino acids
with DB18C6, was not only affected by discrimination in binding these ions to the crown ether macro-cycle, but also significantly
modified by the ion transfer Gibbs energy which was closely related to the structure of the transferred ions, protonated amino
acids. 相似文献