铋-N-苯甲酰苯胲络合吸附波的研究

在pH5.6的0.2mol/L NH_4Ac-3×10~(14)mol/L N-苯甲酰苯胲(N-BPHA)底液中,用单扫示波极谱法可得到Bi(Ⅲ)的络合物吸附波,峰电位-0.33V(vs.SCE)左右。导数峰高与铋的浓度在5.0×10~(-8)～4.0×10~(-6)mol/L的范围内呈线性关系,检出限为2.0×10~(-8)mol/L。实验表明,该极谱峰属于络合物吸附波,测定其络合比为Bi(Ⅲ):N-BPHA=1:3。测定了该体系的吸附量;Bi(Ⅲ)-N-BPHA络合物在悬汞电极上的吸附符合Frumkin等温式,测得吸附系数β=2.87×10~5,吸引因子α=0.984。用于矿石中微量铋的测定。     

铟-8-氨基喹啉络合吸附波的研究

在0.04Mol/L HAc-0.36Mol/L NaAc(pH5.7)和3.5×10~(-4)Mol/L 8-氨基喹啉(8-Aminoquinoline)溶液中,用单扫示波极谱法可得到In(Ⅲ)-8-氨基喹啉络合吸附波,峰电位在-0.78V处。其导数峰高与铟在5.0×10~(-8)-4.0×10~(-6)Mol/L范围内的浓度呈线性关系,最低检出限为2.0×10~(-8)Mol/L。研究确定该波为1∶1铟-8-氨基喹啉络合物的吸附波。测定了几种地球化学标准样品中的锢,结果满意。     

导数吸附计时电势法测定水中的痕量铍

建立了导数吸附计时电势法测定水中痕量铍的方法。采用三电极体系,Be(Ⅱ)和铍试剂Ⅲ形成的络合物,首先通过吸附富集在工作电极上,然后,通以恒电流使之还原,记录时间对电势的一阶导数随电势变化的曲线(dt/dE～E曲线)。Be(Ⅱ)溶液浓度在3.0×10~(-10)～2.0×10~(-7)mol/L范围内与络合物曲线的峰高呈线性关系,方法的检出限为3.0×10~(-10)mol/L。     

吸附溶出伏安法测定痕量砷的研究

在稀盐酸底液中,砷(Ⅲ)与吡咯烷二硫代甲酸铵(APDC)形成的络合物在悬汞电极(HME)上有良好的吸附溶出行为,于—0.53V(vs. SCE. )处有一灵敏的二次导数溶出峰。在1.3×10~(-9)—2.6X10~(-7)mol/As(Ⅲ)浓度范围内,峰高与As(Ⅲ)浓度有良好的线性关系,检出限为1.3×10~(-10)~mol/L。曾用本法测定两种标样以及茶叶中的砷,结果满意。本文还研究了电流性质及电极过程机理。     

示波极谱法同时测定痕量硒和砷

在盐酸-酒石酸锑钾介质中,Se(Ⅳ)在—0.59V(vs.SCE,下同)左右产生示波极谱峰,其二阶导数峰高IP″_(Se)与Se(Ⅳ)浓度在1.26×10~(-8)～1.26×10~(-4)mol·L~(-1)范围呈良好线性关系,Se(Ⅳ)检出下限为5.0×10~(-9)mol·L~(-1)。在相同底液中,当Se(Ⅳ)浓度大于2.5×10~(-6)mol·L~(-1)时,As(Ⅲ)在—0.79V左右也出现一良好极谱峰,其峰高IP″_(As)与As(Ⅲ)浓度在5.3×10~(-7)～2.6×10~(-4)mol·L~(-1)之间呈良好线性关系,As(Ⅲ)检出下限为2.7×10~(-7)mol·L~(-1)。Se(Ⅳ)、As(Ⅲ)两峰电位相差较大,可在同一底液中同时测定。曾用本法测定了煤飞灰标样(82201)中痕量硒和砷,结果与证书值相符。硒、砷加标回收率为95％～110％,还研究了Se(Ⅳ)、As(Ⅱ)极谱波性质。     

锑(Ⅲ)-邻苯三酚红-硫脲体系的极谱络合吸附波

在0.08 mol/L磷酸溶液中,锑(Ⅲ)-邻苯三酚红络合物产生一灵敏的吸附波,加入硫脲对峰高有增敏作用.峰电位在-0.30 V(vs.SCE)左右,峰高与锑浓度在4.1×10-10～2.1×10-6 mol/L间呈线性关系;检出限为2×10-10 mol/L.并进行了机理研究.方法应用于铜合金中锑的直接测定,结果满意.     

铕(Ⅲ)在邻菲啰啉/Nafion薄膜修饰电极上的伏安行为

本文研究了铕(Ⅲ)在邻菲啰啉/Nafion聚合物薄膜修饰电极上的伏安行为。在pH5.1的六次甲基四胺底液中,实验了多种因素对铕(Ⅲ)的还原电流的影响。在选定分析条件下,铕(Ⅲ)的还原峰高在1.0×10~(-7)～1.0×10~(-5)mol/L范围内有良好的线性关系。富集时间15min时,检出限可达3.0×10~(-8)mol/L。用于发光材料中铕(Ⅲ)的测定,取得满意结果。     

碳糊电极上吸附伏安法测定痕量钪的研究

研究了钪(Ⅲ) 茜素氨羧络合剂(ALC)络合物在碳糊电极正电位区的吸附伏安行为,利用该络合物产生的二次导数吸附氧化峰电流与钪浓度成正比测定钪。其线性范围为2.0×10-9～6.0×10-7mol/L;富集120s,检出限达1.0×10-9mol/L(S/N=3)。探讨了电极反应机理。在同一支电极同一表面上15次连续测定4.0×10-8mol/L的Sc(Ⅲ),方法的相对标准偏差为3.7%。该法用于矿石样品中钪的测定,结果满意。     

锡(Ⅳ)-邻苯三酚红-钒(Ⅳ)-十二烷基磺酸钠体系极谱吸附催化波研究

在0.1mol/L氯乙酸盐缓冲溶液(pH2.4)中,锡(Ⅳ)-邻苯三酚红(PR)-钒(Ⅳ)-十二烷基磷酸钠(SDS)体系产生一灵敏的吸附平行催化波,峰电位为-0.53V(vs.SCE),一次导数峰高与锡浓度在6.7×10~(-10)～10×10~(-6)mol/L范围内呈良好的线性关系,检测限为4×10~(-10)mol/L.方法已成功地应用于罐装食品中微量锡的测定,结果满意.     

铜—四（4—甲氧基—3—磺酸苯基）卟啉配合物吸附伏安法的研究

铜-四(4-甲氧基-3-磺酸苯基)卟啉络合物在0.1mol/L KOH溶液中,在-1.25V(vs.SCE)有一灵敏的吸附还原峰,峰高与Cu~(2+)浓度在3.1×10~(-9)～1.5×10~(-7)mol/L范围内呈线性关系。检出限达8×10~(-10)mol/L(富集2min)。本文详细讨论了测定铜的最佳条件,并对试剂及其铜络合物在悬汞电极上的伏安特性和吸附行为作了探讨。此法用于工业硫酸锌盐中微量铜的测定,结果与光度法、原子吸收法一致。     

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.     

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.     

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.     

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.     

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.