液体推进剂偏二甲肼自动电位滴定分析方法的建立

设计了Metrohm809型自动电位滴定仪分析液体推进剂偏二甲肼的应用程序，解决了程序设计中滴定模式和终点确定方式选择、滴定速度确定等关键性技术问题，考察了环境温度对分析结果的影响，确定了最佳条件，实现了液体推进剂偏二甲肼的自动电位滴定分析。重复性试验和准确度试验表明，自动电位滴定法分析偏二甲肼具有准确度高、精密度好等优点，测量结果完全符合GJB753-89的要求：     

光度滴定法在分析化学中的应用

介绍了光度滴定法的基本原理和装置,综述了光度滴定法在食品、药品、化工等领域的应用情况。我国光度滴定法大多是通过浸在溶剂中的光度电极的电位变化来确定滴定终点,操作复杂;国外则是自制光度滴定仪系统,可以实现无校正曲线情况下的定量,自动化程度更高。因此,在推进光度滴定技术在分析化学中应用的同时,我国还需要开发一系列集合溶剂流路控制系统和高精度光度计的全自动滴定装置,以满足食品、药品、化工等领域快速检测、批量检测的要求。     

自动电位滴定仪的“前世”

正滴定分析法的历史可追溯到18世纪晚期。19世纪上半叶,法国化学家Joseph Louis Gay-Lussac命名了这一化学分析方法,因此常被认为是滴定法的发明者。如今,滴定法成为最重要的化学分析技术之一,这种方法应用广、速度快、成本低且可自动化。自动电位滴定法在20世纪中期开始流行,Metrohm公司是这一领域的先锋。1949年,Metrohm迈出了自动电位滴定的第一步,推出第一台自动电位滴定仪Titriskop。这是一款为滴定用户特别设计的酸度仪。     

自动电位滴定法测定冷轧薄板酸洗液中总酸度

自动电位滴定法测定酸液中总酸度具有简单、快捷、不受其他元素干扰等优点。用硫代硫酸钠掩蔽铁离子,利用自动电位滴定仪测定冷轧薄板酸洗液的总酸度(以盐酸量计)。当电位突变达30mV以上时,仪器自动判定滴定终点。自动电位滴定法测定冷轧薄板酸洗液中总酸度结果与酸碱中和滴定方法具有较好的一致性。相对标准偏差小于0.6%,能够满足生产检验的要求。     

电位滴定法测定抛光液中的三酸含量

探讨了利用自动电位滴定仪对抛光液中磷酸、硫酸及硝酸的分析方法,以及对溶剂的标定方法。电位滴定法测定三酸,先用硫酸亚铁铵滴定硝酸,再用氢氧化钠滴定磷酸和硫酸,从而计算三酸含量。结果表明,与传统滴定法相比,电位滴定法标定硫酸亚铁铵的相对标准偏差(RSD)从1.1%降至0.13%,标定氢氧化钠的RSD从0.72%降至0.06%。电位滴定法测定自配样品及工厂抛光产品中的硝酸,回收率分别在96%及93%以上。电位滴定法测定自配样品及工厂抛光产品中磷酸和硫酸的回收率偏差在3%以内。手动滴定法测定磷酸和硫酸的回收率偏差在5%~10%,回收效果不如电位滴定法。电位滴定法测定工厂抛光液的三酸加标回收率偏差均小于3%。自动电位滴定法比手工滴定的准确性和精密度明显提高,弥补了手工滴定法只能分析磷酸和硫酸,而无法测定硝酸的缺陷。     

电位滴定法测定抛光液中的三酸含量

探讨了利用自动电位滴定仪对抛光液中磷酸、硫酸及硝酸的分析方法,以及对溶剂的标定方法。电位滴定法测定三酸,先用硫酸亚铁铵滴定硝酸,再用氢氧化钠滴定磷酸和硫酸,从而计算三酸含量。结果表明,与传统滴定法相比,电位滴定法标定硫酸亚铁铵的相对标准偏差(RSD)从1.1%降至0.13%,标定氢氧化钠的RSD从0.72%降至0.06%。电位滴定法测定自配样品及工厂抛光产品中的硝酸,回收率分别在96%及93%以上。电位滴定法测定自配样品及工厂抛光产品中磷酸和硫酸的回收率偏差在3%以内。手动滴定法测定磷酸和硫酸的回收率偏差在5%～10%,回收效果不如电位滴定法。电位滴定法测定工厂抛光液的三酸加标回收率偏差均小于3%。自动电位滴定法比手工滴定的准确性和精密度明显提高,弥补了手工滴定法只能分析磷酸和硫酸,而无法测定硝酸的缺陷。     

自动电位滴定法连续测定水中卤素离子

目前化验室滴定分析普遍采用指示剂滴定法检测水中卤素离子。由于指示剂受到人眼辨色能力、有色或浑浊样品影响较大,特别是对滴定平衡常数[1]较小(Ka/b<10-7),变色不敏锐,或者指示剂不够灵敏时,会造成一定的终点误差。电位滴定法克服了这些缺点,以测量待测溶液的电位突变来确定滴定终点。本文利用卤化银的Ksp差异,用自动电位滴定法连续测定Cl-、Br-I、-的含量。水样无须预处理,对有色、浑浊等水样可直接参与滴定分析。1试验部分1.1仪器808 DMP型自动电位滴定仪。1.2工作条件信号漂移值为30 mV·min-1,最小增液量为10μL,加液速率50 mV…     

表面活性剂碱度测定方法的改进和验证

表面活性剂碱度的检测主要依照国标GB/T 7378-1996中的方法,使用手动滴定、依据指示剂来判断滴定终点.本文基于全自动电位滴定仪对国标方法进行了改进和验证,建立了表面活性剂碱度测定的光度滴定法和电位滴定法,并对两种改进方法进行了验证.改进后的方法分别根据光度电极和电位电极的突跃点来判断滴定终点,判断更准确,与国标方法的结果相一致,重复性RSD≤3.0％.在国标方法基础上改进的光度滴定法和电位滴定法,滴定体积控制精确、自动化程度高、重复性和准确性好,可作为国标方法的改进方法用于实际检测.     

分析化学整体式电位滴定仪的自制研究

研制了整体式电位滴定仪,该滴定仪综合了加热、搅拌、酸度值测定、电位测定等功能,具有简便易操作、测试稳定、精准性和重复性高等优点,同时该仪器还可进一步应用于酸碱滴定、氧化还原滴定、络合滴定、沉淀反应、非水滴定等电位滴定的分析。从而增加了实验手段的多样化,提高了实验的趣味性和学生的积极性。     

自动电位滴定法分析液体推进剂单推三的研究

设计自动电位滴定仪分析单推三的应用程序。主要解决了程序设计中滴定终点判定等参数设置、数据处理以及数值传递等技术难点,与Q／Sdll—92标准容量法分析结果进行比较,两种方法的测定结果无显著性差异,自动电位滴定法分析单推三具有速度快、准确度高、可靠性好等优点,可替代容量法。     

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.     

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%).