多壁碳纳米管修饰玻碳电极测定多巴酚丁胺的研究

研究了多巴酚丁胺在多壁碳纳米管修饰电极上的电化学行为,建立了一种直接测定多巴酚丁胺的电化学方法。在0.3mol·L-1H2SO4底液中,氧化峰电位为0.57V(vs.Ag/AgCl),峰电流与多巴酚丁胺的浓度在5.0×10-8～1.0×10-5mol·L-1范围内呈良好的线性关系。该法的检出限为3.0×10-8mol·L-1。平均回收率为99.15%。1.0×10-5mol·L-1多巴酚丁胺平行测定8次的标准偏差为4.8%。用拟定的方法测定了多巴酚丁胺注射液中多巴酚丁胺的含量,结果满意。     

纳米银修饰电极对痕量硫氰根的测定

用纳米银修饰玻碳电极并检测了痕量硫氰根。在pH6.0的磷酸盐缓冲溶液中,运用示差脉冲伏安法,氧化峰电流值和硫氰根的浓度在5.0×10-7～4.0×10-4mol·L-1范围内呈良好的线性关系;检出限为4.137×10-8mol·L-1;应用于吸烟人和非吸烟人的唾液中痕量硫氰根的测定,结果满意。     

铈(Ⅳ)-吐温40-对苯二酚化学发光体系测定氢醌乳膏中对苯二酚

讨论了表面活性剂对铈(Ⅳ)氧化对苯二酚化学反应的影响,发现了铈(Ⅳ) 吐温40 对苯二酚化学发光新体系,建立了测定对苯二酚化学发光分析方法,该法测定对苯二酚的线性范围为8.0×10-7～5.0×10-5mol·L-1,检出限为5.0×10-7mol·L-1,相对标准偏差为2.5%(5.0×10-6mol·L-1对苯二酚,n=11)。该法应用于测定氢醌乳膏中的对苯二酚,结果满意。     

电位溶出分析法同时测定罐头食品中痕量铅锡

利用不除氧电位溶出分析法成功地测定了溶出电位相近的铅、锡两元素。以0.05mol·L-1草酸为介质,调节溶液pH1.0,以溶解氧作氧化剂,静止溶出,两元素均有分离清晰的平台出现。铅、锡的线性范围分别为2.0×10-9～2.0×10-7mol·L-1和2.0×10-8～2.0×10-6mol·L-1。当富集时间为4min时,铅、锡的检出限分别为5.0×10-10mol·L-1和5.0×10-9mol·L-1。此法已成功地应用于测定罐头食品中痕量铅和锡。     

粉末微电极溶出伏安法检测溶液中的重金属离子

本文利用粉末微电极技术得到了Hg2+、Pb2+、Cu2+及Cd2+的溶出伏安曲线,并分别检测了溶液中微量Hg2+、Pb2+、Cu2+及Cd2+的浓度,其测量灵敏度分别为:514.6μA/cm2·μmol·L-1、131.5μA/cm2·μmol·L-1、41.2μA/cm2·μmol·L-1和96.5μA/cm2·μmol·L-1;检出限分别为:5.0×10-7mol/L、5.0×10-7mol/L、1.0×10-6mol/L和2.0×10-6mol/L;线性检测范围分别为:3.4～10.9μmol/L、4.5～10.0μmol/L、2.9～10.0μmol/L和2.2～11.2μmol/L。当溶液中同时存在上述四种金属离子时,采用粉末微电极技术得到了四个完全分离、互不干扰的氧化电流峰。     

聚L-苏氨酸修饰电极对多巴胺和肾上腺素的电催化氧化

利用循环伏安法将L-苏氨酸聚合修饰在玻碳电极表面, 制成聚L-苏氨酸修饰电极. 实验表明, 该电极对多巴胺和肾上腺素都有较好的催化氧化效果. 运用循环伏安法详细研究了修饰电极的电化学性质. 在pH 2.5的磷酸盐缓冲溶液(PBS)中, 肾上腺素的电子传递系数为0.51, 表观反应速率常数为1.33 s-1; 在pH 7.5的PBS中, 多巴胺在电极上产生一对氧化还原峰, 多巴胺在电极上的电子传递系数为0.60, 表观反应速率常数为0.92 s-1. 该修饰电极对多巴胺和肾上腺素能够进行同时测定, 还原峰电流与多巴胺和肾上腺素浓度分别在1.0×10-6-5.0×10-4 mol·L-1和3.0×10-6-1.0×10-4 mol·L-1范围内呈现良好的线性关系.     

线性扫描极谱法测定微量肉桂酸

在 1mol·L-1HOAc NaOAc介质中 (pH =3.6 ) ,肉桂酸有一还原峰 ,其峰电位为 - 1.4 7V(vs.SCE)。峰电流与肉桂酸浓度在 2 .0× 10 -5～ 8.0× 10 -4 mol·L-1之间呈线性关系 (r =0 .9989) ,检出限为 1.0× 10 -5mol·L-1。该法应用于肉桂酸含量的测定 ,结果满意 ,并对肉桂酸的电化学性质进行了研究     

聚乙烯吡咯烷酮修饰碳糊电极上酪氨酸的电化学研究及其测定

研究了酪氨酸在聚乙烯吡咯烷酮修饰碳糊电极的伏安行为,优化了测定条件,在此基础上建立了一种直接测定酪氨酸的电分析方法。氧化峰电流与酪氨酸的浓度在2×10-7～5×10-5mol·L-1之间有良好的线性关系,开路富集3min,检出限为1×10-7mol·L-1。用此方法测定了酒样和人尿中酪氨酸的含量,结果满意。     

痕量雌二醇的吸附方波伏安法检测

本文报道一种简便、快速、灵敏检测痕量雌激素的吸附溶出方波伏安法。该法先将雌二醇在玻碳电极上吸附富集一定时间 ,然后以方波伏安溶出法检测其氧化电流。介质为含有 8× 1 0 - 5mol· L- 1溴化十六烷基三甲铵 ( CTAB)的 0 .1 mol· L- 1磷酸盐缓冲溶液 ( p H=1 0 .0 )。该法检出限为 5× 1 0 - 8mol· L- 1,线性范围为 5 .2× 1 0 - 7～ 5× 1 0 - 5mol· L- 1。研究了雌二醇的电极反应机理     

L-半胱氨酸自组装膜修饰电极对对氨基酚电催化氧化及其分析应用

在裸金电极上制备了L 半胱氨酸自组装膜修饰电极(L Cys/AuSAMs),研究了对氨基酚(p AP)在L Cys/AuSAMs上的电化学行为,发现该膜电极对p AP的氧化具有良好的电催化作用。氧化峰电位降低了128mV,测得p AP的扩散系数D为1.27×10-6cm2·s-1,初步探讨了电催化机理。采用水平衰减全反射 傅立叶变换红外光谱(ATR FTIR)技术对L Cys/AuSAMs进行了表征;方波伏安法(SquareWaveVoltammetry,SWV)测定p AP,其氧化峰峰电流与p AP浓度在1.0×10-8～8.0×10-8mol·L-1和1.0×10-7～2.0×10-4mol·L-1范围内呈线性关系,相关系数分别为0.9978和0.9977,检出限为2.0×10-9mol·L-1。该电极用于模拟废水样的测定,结果满意。     

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%.     

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.     

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.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

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.