二氧化硫脲还原沉析银的电势法研究

本文采用电势法研究二氧化硫脲的银氨溶液以沉析银的反应体系。获知体系温度、ｐＨ值、氨含量对反应速度和银沉析率均有较大的影响。在ＮＨ３和Ａｇ＾＋摩尔比为１８：１时，体系的最佳反应条件是：ｐＨ＝１２．００，温度为５０℃。在此条件下，将二氧化硫脲溶液不断地加入到［Ａｇ（ＮＨ３）２＾＋］溶液中，当反应体系的电势降到－７００ｍＶ（ｖｓ．ＳＣＥ）时，停止加入还原剂，并迅速中止反应，此时银的还原沉析率达９９．９％     

水溶性铑－膦配合物催化1－十二碳烯常压氢甲酰化反应研究

本文研究了水溶性铑配合物ＲｈＣｌ（ＣＯ）（ＴＰＰＴＳ）２在常压（ＣＯ：Ｈ２＝１：１）条件下对１－十二碳烯氢甲酰化反应的催化性能，并对催化剂浓度、表面活性剂浓度、溶液ｐＨ值、膦铑比、溶剂等因素的变化对催化活性的影响作了考察．结果表明，表面活性剂（ＣＴＡＢ）的加入，可以在反应体系中形成胶束．加速有机相和水相间的传质速度，从而提高催化转化速度．在反应温度（８０℃）下，ＣＴＡＢ的临界胶束浓度（ＣＭＣ）较室温下高．达到最佳催化活性的ｐＨ范围为７～９，［Ｐ］／［Ｒｈ］比为１６，而有机溶剂的加入则使转化数降低．     

胶束催化对硝基苯酚乙酸酯碱性水解的动力学研究

碱性溶液中羧酸酯的催化水解反应有些报道[1~4],OH-对乙酸酯的亲核进攻,形成了一个阴离子四面体中间物,该四面体中间物的C为sp3杂化,反应裂解成为CH3COO-和对硝基苯酚。然而,目前对胶束溶液中对硝基苯酚乙酸酯的碱性水解方面的系统研究还未见报到,因此,本文在30℃、1·62×10-3     

催化褪色光度法测定痕量铜

1　引　　言催化动力学光度法是一种高灵敏度的分析方法 ,用此方法测定铜已有不少报道。但在ｐＨ =1 0的氨性溶液中 ,阳离子表面活性剂氯化十六烷基吡啶 (ＣＰＣ)存在下 ,Ｃｕ2 + 催化Ｈ2 Ｏ2 对间甲酚紫 (ｍ ＣＰ)的褪色反应尚未见报道。研究发现 ,间甲酚紫在ｐＨ =1 0的ＮＨ3 ＮＨ4Ｃｌ溶液中呈紫红色 ,再加入阳离子表面活性剂氯化十六烷基吡啶 ,溶液呈蓝紫色 ,Ｃｕ2 + 对Ｈ2 Ｏ2 氧化这种蓝紫色溶液的褪色反应有催化作用 ,从而建立了催化褪色光度法测定铜的新方法。本方法具有灵敏度高 ,操作简便、重现性好、选择性强等优点 ,直接用于人…     

水溶性钯－膦配合物催化1－己烯加氢反应研究

研究了水溶性钯－膦配合物ＰｄＣｌ２（ＴＰＰＴＳ）２催化１－己烯加氢反应，考察了两相催化体系中添加表面活性剂ＣＴＡＢ，膦配体ＴＰＰＴＳ，以及溶液ｐＨ值等对反应的影响，证明了１－己烯加氢反应中有一诱导期．反应中涉及两种催化活性物种．一种是由ＰｄＣｌ２（ＴＰＰＴＳ）２还原生成的低氧化态催化物种，它在一定的ＣＴＡＢ浓度下，可以保持相当的稳定性．另一种是被ＴＰＰＴＳ或Ｈ２还原形成的钯黑．根据ＰｄＣｌ２和ＴＰＰＴＳ反应过程的３１ＰＮＭＲ研究，对ＰｄＣｌ２（ＴＰＰＴＳ）２分子中Ｐｄ被还原和ＴＰＰＴＳ被氧化提出了解释     

反胶团相转移法提取青霉素G的研究

报道了非蛋白质类活性物质青霉素Ｇ在反胶团相转移提取中的特性和机理。结果表明，青霉素Ｇ在ＣＴＡＢ／正辛醇：氯仿（４：１，Ｖ／Ｖ）反胶团体系中的相转移提取为离子对静电作用与胶团溶解机理；在室温及ｐＨ值５～８的条件下，提取率在９０％以上，且保持了青霉素的稳定性。     

氨三乙酸稀土络合物配体交换反应的NMR研究

利用变温＾１３Ｃ，＾１Ｈ－ＮＭＲ研究了过量配体存在下，氨三乙酸稀土络合物Ｌｎ（ＮＴＡ）２（Ｌｎ＝Ｃｅ，Ｐｒ和Ｎｄ）配体交换反应。在中必不溶液中，分子间的配体交换过程按中下机制进行：Ｌｎ（ＮＴＡ）２＾３－＋ＨＮＴＡ＾２－＝Ｌｎ（ＮＴＡ）（ＮＴＡ）＾３＋＋ＮＨＴＡ＾２－由溶液中溶液中自由ＮＴＡ信号线宽分析了交换速率、确定了反应的活化能。结果表明，分子间配体交换反应化能与相应稀土络合物热力学稳定性有一定     

两相催化体系中α，β－不饱和醛选择加氢反应研究Ⅲ．表面活性剂、溶剂对选择加氢反应的影响

研究了水溶性钌－膦配合物催化肉桂醛选择加氢反应中，相转移剂和表面活性剂对反应转化率和选择性的影响，考察了表面活性剂ＣＴＡＢ（十六烷基三甲溴化铵）浓度以及影响两相界面性质的因素—水相和有机相体积比、有机溶剂的改变等的影响．结果表明，相转移剂可以促进反应进行，其中以季铵盐相转移剂最好；表面活性剂能够显著地加快反应，其中以阳离子表面活性剂的效果最佳，且分子中含有长链烷基者（如ＣＴＡＢ）效果更好，非离子和阴离子表面活性剂的效果较差；对于ＣＴＡＢ，其浓度的增加导致反应速度的明显加快，但ＣＴＡＢ浓度达到１．６５×１０－２ｍｏｌ／Ｌ之后，反应体系乳化严重，反应完成后，两相分离变得困难．而增加水相体积和加入适当的有机溶剂，有利于转化率和选择性的提高．     

读者园地

问 :ＢＣＯ与铜 (Ⅱ )离子的显色反应与所采用的缓冲体系有何关系 ?福建读者———谢敏答 :在现行的分析方法中常采用的缓冲体系有氨性缓冲和硼酸钠缓冲两种。不同的缓冲体系对显色反应的适宜酸度范围及显色后络合物的稳定性等条件有影响。在氨性缓冲溶液中显色的适宜酸度条件为ｐＨ9.0～ 9.5。在硼酸钠缓冲溶液中的酸度条件为ｐＨ8.5～ 9.5。为说明显色时酸度控制的方法 ,选择以下三种操作为实例 :(1)氨性缓冲体系 1:加柠檬酸铵络合大量铁(钢铁试样 )后滴加氨水 (1+ 1)至酚酞指示剂变红色 ,然后加入氨水 氯化铵缓冲溶液 (ｐＨ 9.2 ) 2 0…     

阳,阴,非离子表面活性剂胶束对酯碱性水解的影响

应用紫外分光光度法和热动力学方法研究了芳香酸酯和正脂肪酸酯在表面活性剂ＤＴＡＢ、ＴＴＡＢ、ＣＴＡＢ、ＳＤＳ、Ｂｒｉｊ３５、Ｔｒｉｔｏｎ Ｘ－１００胶束中的碱性水解反应，阳、阴、非离子表面活性剂胶束对酯的碱必水解均有禁阻作用，讨论了胶束对酯碱性水解禁阻作用的原因。     

Hydrolysis of BNPP Catalyzed by the Crowned Schiff Base Co(II) Complex Containing Benzoaza‐15‐Crown‐5 in Micellar Solution

It has been reported that three aza crowned Schiff base cobalt (II) complexes were synthesized and characterized, and the metallomicelle made up of the cobalt (II) complexes and surfactants(Brij35, CTAB, LSS), as mimic hydrolytic metalloenzyme, was used in catalytic hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP). The analysis of specific absorption spectrums of the hydrolytic reaction systems indicated that key intermediates made up of BNPP and Co (II) complexes are formed in the reaction process of BNPP catalytic hydrolysis. The mechanism of BNPP catalytic hydrolysis proposed is based on the analytic result of specific absorption spectra. Based on the mechanism proposed, a kinetic mathematical model for the calculation of the kinetic parameter of BNPP catalytic hydrolysis has been established. The acid effect of reaction system, structure effect of the complexes, effect of temperature and effect of micelles on the rate of BNPP hydrolysis catalyzed by the complexes have been discussed.     

Studies on PNPP Hydrolysis Catalyzed by Divalent Metal Ion Macrocyclic Schiff Base Complexes in Micellar Solution

Two transitional metal ion macrocyclic Schiff base complexes, NiL and CuL were synthesized and characterized, and the metallomicelles made up of the nickel(II) and copper(II) complexes and surfactants(LSS, Brij35, CTAB), as mimic hydrolytic metalloenzyme, were used in catalytic hydrolysis of carboxylic ester (PNPP). The analysis of specific absorption spectrums of the hydrolytic reaction systems indicates that key intermediates, made up of PNPP and Ni(II) or Cu(II) complexes, have formed in the reaction processes of the PNPP catalytic hydrolysis. In this, based on the analytic result of specific absorption spectrum, the mechanism of PNPP catalytic hydrolysis has been proposed; a kinetic mathematical model, applied to the calculation of the kinetic parameter of PNPP catalytic hydrolysis has been established on the foundation of the mechanism proposed; the acid effect of reaction system, structure effect of the complexes, effect of temperature and effects of micelle on the rate of PNPP hydrolysis catalyzed by the complexes also have been discussed.     

Catalytic Kinetics of the Schiff Base Metal Complexes Bearing Side Chain of Cyclic morpholine in Carboxylic Ester Hydrolysis

It has been reported that two Schiff base transition metal complexes bearing the side chain of the morpholine ring were synthesized and characterized, and two complexes with the same base agent but different metal ions were used as a simulant hydrolase in the catalytic hydrolysis of p-nitrophenyl picolinate in this paper. The mechanism of PNPP catalytic hydrolysis is proposed and supported by the results of the spectral analysis and the kinetic calculation. A kinetic mathematical model, applied to the calculation of the kinetic and thermodynamics parameters of PNPP catalytic hydrolysis, has been established on the foundation of the mechanism proposed. The result of the study shows that the two complexes have a good catalytic activity in PNPP catalytic hydrolysis, and the rate of the PNPP catalytic hydrolysis was increased with the increase of the pH values in the buffer solution and affected by the polarization effect of metal ion of the complexes.     

MICELLAR CATALYSIS OF COMPOSITE REACTIONS I MICELLAR EFFECT ON THE CONSECUTIVE FIRST ORDER REACTION

The micellar catalytic model (or the consecutive first order reaction has been proposed in this paper. It was applied to the alkaline hydrolysis of dimethyl phthalate in micellar solutions of surfactants (CTAB, SDS and Triton X-100), and the alkaline hydrolysis of bis (2,4-dinitrophenyl) posphate in CTAB micellar solution. Rate constants obtained in micellar phase indicate that the two steps of alkaline hydrolysis of dimethyl phthalate are both inhibited by all of the surfactants investigated. CTAB micelle exhibits a greater catalytic effect on the alkaline hydrolysis of bis (2, 4-dinitrophenyl) phosphate. this may be arised from the local concentration effect of hydroxide ion in CTAB micellar phase. Nevertheless. the second order rate constant of bis-(2, 4-dinitrophenyl) phosphate in the micellar phase is smaller than that in the bulk phase.     

A study on the hydrolysis of bis(nitrophenyl)phosphate catalyzed by N‐methyldiethanolamine‐Ce(III) complex

The hydrolysis of bis(p‐nitrophenyl)phosphate (BNPP) catalyzed by N‐methyldiethanolamine‐Ce(III) complex in the presence and absence of cetyltrimethylammonium bromide (CTAB) and Brij35 surfactants at pH 7.20 and 303 K has been studied. The experimental results indicate that N‐methyldiethanolamine‐Ce(III) complex remarkably accelerates the hydrolysis of BNPP. The observed first‐order rate constant of the hydrolysis of BNPP catalyzed by N‐methyldiethanolamine‐Ce(III) complex at pH 7.20 and 303 K is 1.22 × 10^?2 s^?1, which is 1.09 × 10⁹ times of that of spontaneous hydrolysis of BNPP at pH 7. It is close to the activity of natural enzyme. A general quantitative treatment of the catalytic reaction involved a ternary complex as M_mL_lS has also been proposed in this paper. Applying this method to the catalytic hydrolysis of BNPP, we have obtained its thermodynamic and kinetic parameters. CTAB and Brij35 surfactant micelles obviously influence the rate constants of the catalytic hydrolysis of BNPP. Brij35 micelles promote the catalytic hydrolysis of BNPP, while CTAB micelles inhibit it. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 687–692, 2004     

Studies on PNPP Hydrolysis Catalyzed by Schiff Base Cobalt（Ⅱ） Complexes

Two cobalt（Ⅱ） complexes of the Schiff base with morpholino or aza-crown ether pendants, CoL^1 and CoL^2, as mimic hydrolytic metalloenzyme, were used in catalytic hydrolysis of carboxylic ester （PNPP）. The analysis of specific absorption spectra of the hydrolytic reaction systems indicates that key intermediates, made up of PNPP and Co（Ⅱ） complexes, have been formed in reaction processes of the PNPP catalytic hydrolysis. The mechanism of PNPP catalytic hydrolysis has been proposed based on the analytic result of specific absorption spectrum. A kinetic mathematical model, applied to the calculation of the kinetic parameter of PNPP catalytic hydrolysis, has been established based on the mechanism proposed. The acid effect of buffer solution, structural effect of the complexes, and effect of temperature on the rate of PNPP hydrolysis catalyzed by the complexes have been also discussed.     

Hydrolysis of PNPP Catalyzed by Cu (II), Ni (II) Schiff Base Complexes in CTAB Micellar Solution

The kinetics of hydrolysis of p‐nitrophenyl picolinate(PNPP) catalyzed by metallomicelles formed from Cu (II), Ni (II) Schiff base complexes (CuL, NiL) and CTAB micelle were investigated in the pH range of 6.0–9.0 at 30°C. For the Cu (II) Schiff base complex CuL, the apparent rate constants (k _obsd) of PNPP hydrolysis initially increased with the increasing pH of reaction media, then fell off. For the Ni (II) Schiff base complex NiL, the k _obsd always increased with the increasing pH. The kinetic and thermodynamic parameters were calculated. The hydrolysis rate of PNPP catalyzed by Cu (II) complex was much larger than that by Ni (II) complex in CTAB micellar solution. The catalytic mechanism of the PNPP hydrolysis was discussed in detail, and the possibly active specie for the catalytic hydrolysis of PNPP was the monohydroxo metal complex.     

Influence of Amine‐Based Cationic Gemini Surfactants on Catalytic Activity of α‐Chymotrypsin

The α‐chymotrypsin activity was tested in aqueous media with the presence of novel cationic amine–based gemini surfactant, with different spacer chain lengths and head group size, and also compared with the cationic cetyltrimethylammonium bromide (CTAB) and cetyltriphenylphosphonium bromide (CTPB) surfactants and aqueous buffer only. The p‐nitrophenyl acetate (PNPA) hydrolysis rate was monitored in the presence of the surfactant concentration at 30°C. Most of these gemini surfactants gave higher catalytic activity as compared to cationic CTAB and CTPB. The highest superactivity was measured in the presence of gemini 16‐12‐16, [dodecanediyl‐1,12‐bis(cetyldimethylammonium bromide)] surfactant at pH 7.5. The catalytic reaction follows the Michaelis–Menten mechanism. The catalytic rate constants, k_cat, show the same profile that the catalytic affinity; K_M being enhanced with increasing space chain length. The results are favorable for considering that the amine‐based gemini surfactant influences more than both the aqueous and cationic micellar media.     

Studies on p-Nitrophenyl Picolinate Cleavage by Unsymmetrical Bis-Schiff Base Manganese(III) and Cobalt(II) Complexes in CTAB Surfactant Micellar Solution

The unsymmetrical bis-Schiff base manganese(III) and cobalt(II) complexes with either benzo-10-aza-crown ether pendants (MnL¹Cl, MnL²Cl) or morpholino pendant (MnL³Cl, CoL³) have been employed as models for hydrolase by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP) in the buffered CTAB micellar solution. A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit higher catalytic activity in the buffered CTAB micellar solution and the rate increases with pH of the buffered CTAB micellar solution under 25°C. The complexes containing a crown ether group exhibit higher catalytic activities than the free-crown analogues. The catalytic activity of manganese(III) complex is superiority over cobalt(II) complex in catalyzing hydrolysis of PNPP under the same ligand.     

Metallomicellar Catalysis: Hydrolysis of PNPP Catalyzed by Copper(II), Zinc(II), Cerium(IV) Complexes with Long Alkyl Pyridine Ligands in CTAB Micellar Solution

A kind of new functional surfactant with substituted long alkyl pyridine was synthesized and its Ce(IV), Zn(II), and Cu(II) complexes were used as hydrolytic metalloenzyme models. The hydrolysis of p-nitrophenyl picolinate (PNPP) catalyzed by the metallomicelles in CTAB micellar solution was investigated at different pH and 30°C. Kinetic parameters of catalytic hydrolysis were obtained by employing the ternary complex kinetic model for metallomicellar catalysis. Effects of the structure of ligands and microenvironment of reaction on the hydrolytic reaction of PNPP have been discussed in detail. From the apparent rate constants (k _obsd ) of the catalytic hydrolysis of PNPP, it can be seen that the catalytic effect of complexes of ligand L² with long hydrocarbon chain was stronger than that of ligand L¹, and complex CuL² showed higher catalytic efficacy on the hydrolytic reaction than those of ZnL² and CeL². However, experiment results in this article showed that ZnL² and CeL² are more susceptible to environment than CuL². The catalytic mechanism was proposed, and the possibly active species for the catalytic hydrolysis of PNPP was determined to be the hydroxylated metal complex.