NO2-在CTMAB-氧化钕纳米修饰电极上的电化学行为及其测定

制备了十六烷基三甲基溴化铵-氧化钕纳米修饰电极。用循环伏安法和示差脉冲伏安法研究了NO2-在该修饰电极上的电化学行为,结果表明,该修饰电极对NO2-的氧化具有良好的电催化能力,NO2-的氧化峰电流与其浓度在3.33×10-8～1.04×10-6mol/L范围内呈现良好的线性关系,检测限为9.86×10-9mol/L(S/N=3)。此外,该修饰电极具有良好的重现性和稳定性。本方法可用于NO2-实际样品的测定。     

直接电沉积金纳米粒子修饰氧化铟锡电极测定亚硝酸根

以电化学沉积法一步制得了金纳米粒子(GNP)修饰氧化铟锡(ITO)电极,采用紫外、扫描电镜及循环伏安法对GNP/ITO修饰电极进行了表征。结果表明,金纳米粒子在ITO电极表面呈球形,分布均匀无团聚,粒径约30 nm。该修饰电极具有良好的电化学性能,在pH 2.2的Na2HPO4-柠檬酸缓冲溶液中其氧化峰电流与NO2-的浓度呈良好的线性关系,线性范围为5×10-6~5.5×10-4mol/L,线性回归方程为:i(μA)=1.07 136C(mmol/L),相关系数r=0.9969;检出限可达1.0×10-6mol/L。该修饰电极用于废水中NO2-的测定,结果令人满意。     

对硫磷在纳米氧化铝薄膜修饰电极上的电化学行为及其测定

制备了纳米氧化铝修饰玻碳电极(nano-Al2O3/GCE/CME),用循环伏安法(CV)、线性扫描伏安法(LSV)研究了对硫磷(TP)在nano-Al2O3/GCE/CME上的电化学行为.实验表明,该修饰电极与裸电极相比能显著提高TP的氧化还原峰电流并降低其氧化峰电位.在0.1 mol/L HAc-NaAc缓冲溶液(pH =5)中,TP在该修饰电极上产生1个不可逆的还原峰( Epc1=-0.567 V)和1对可逆氧化还原峰( Epa2=0.018 V和Epc2=-0.008 V) ,氧化峰电流与TP的浓度在2.5×10-9～1.0×10-7 mol/L和1.0×10-7～1.0×10-5 mol/L范围内具有良好的线性关系,回归方程分别为: ip(μA)=0.2529+4.201C(μmol/L), r=0.9984和ip(μA)=0.6752+0.3181C(μmol/L), r=0.9946.开路富集30 s后,检出限为1.0 ×10-9 mol/L(S/N=3).在1.0×10-5 mol/L TP试液中连续测定10次,其RSD为3.8%.用此方法测定了蔬菜中TP的含量,回收率为95. 6%～100.5% ,结果满意.     

纳米金/三聚氰胺修饰电极检测亚硝酸盐

采用电聚合方法制备三聚氰胺(MA)膜修饰玻碳电极(GCE),然后采用原位恒电位沉积法制备金纳米颗粒(Au),并将其修饰于膜电极表面,制得纳米金/三聚氰胺修饰玻碳电极(Au/MA/GCE)。用扫描电子显微镜(SEM)对修饰电极进行表面形貌和元素成分分析。用循环伏安法研究亚硝酸根(NO2-)在该修饰电极上的电化学行为发现,NO2-在0.85 V出现一灵敏的氧化峰。在优化的实验条件下,NO2-在1.0×10-5～1.0×10-3mol/L浓度范围内与其氧化峰电流成线性关系,检测下限为8.9×10-7mol/L。将修饰电极用于实际样品中NO2-的检测,效果良好。     

抗坏血酸在纳米银DNA修饰电极上的电化学行为研究

利用电化学生长法制备了纳米银DNA修饰电极.在pH 4.1的磷酸盐(PBS)缓冲溶液中研究了抗坏血酸(AA)在该电极上的电化学行为,实验得到电荷传递系数α=0.41、扩散系数D=1.22×10-5 cm2 /s.建立了利用修饰电极催化作用快速测定抗坏血酸的方法,修饰电极对抗坏血酸的催化氧化峰与抗坏血酸的浓度分别在1.0×10-2～5.0×10-5 mol/L、5.0×10-6～5.0×10-8 mol/L范围内呈线性关系,检出限为1.0×10-9 mol/L.该方法快速、灵敏.     

多巴胺在牛磺酸修饰玻碳电极上的电化学行为及其分析应用

采用电化学聚合法制备了牛磺酸修饰玻碳电极,研究了多巴胺在聚牛磺酸修饰电极上的电化学行为,建立了测定痕量多巴胺的新方法.在pH 7.2的磷酸盐缓冲溶液中,多巴胺在修饰电极上产生一对灵敏的氧化还原峰,采用差分脉冲伏安法测定,其氧化峰电流与多巴胺浓度在8.0×10-8～1.0×10-4 mol/L范围内呈良好的线性关系,检出限为1.0×10-8 mol/L.     

水合肼在多壁碳纳米管修饰电极上的电化学行为及测定

报道了水合肼在碳纳米管修饰电极上的电化学行为以及水合肼测定的新方法。与裸玻碳电极相比,多壁碳纳米管修饰玻碳电极使水合肼的氧化峰电流显著提高,同时氧化过电位降低,测定灵敏度大为提高。优化了底液、pH、修饰剂量等测定条件。在最佳条件下,该修饰电极测定水合肼的线性范围为2.9×10-8~9.8×10-4mol/L,线性相关系数为-0.9945,检出限为1.0×10-9mol/L。对1.0×10-4mol/L的水合肼平行测定10次的相对标准偏差为4.4%。此方法已用于模拟水样中水合肼的测定。     

NO2-在CTMAB-碳纳米管修饰电极上的电化学行为及测定

制备了十六烷基三甲基溴化铵-多壁碳纳米管修饰电极.用循环伏安法和示差脉冲伏安法研究了NO2 -在该修饰上的电化学行为,该修饰电极对NO2 -的氧化具有良好的电催化能力,NO2 -的氧化峰电流与其浓度在1.67×10-7 ～2.2×10 -5mol/L范围内呈现良好的线性关系,检测限为5.6×10-8mol/L(S/N=...     

CeO2纳米晶包裹碳纳米管修饰电极对特布他林的电催化测定

制备出CeO2纳米晶包裹碳纳米管修饰玻碳电极,并运用循环伏安法、交流阻抗谱探讨了该电极的电化学特性。研究了特布他林在该修饰电极上的直接电化学行为。实验结果表明,特布他林在该修饰电极上具有良好的电流响应,与裸玻碳电极相比在pH 7.0缓冲溶液中氧化峰电位负移314 mV。采用计时电流法测定特布他林,其氧化峰电流与浓度在5.0×10-7~1.0×10-4mol/L范围呈良好线性关系,线性方程为:Ip(μA)=4.952-0.04724c(μmol/L),线性相关系数为0.9920,检出限为5.0×10-8mol/L(信噪比为3)。该电极已用于特布他林片剂中特布他林的测定。     

亚硝酸根和L-色氨酸在多壁碳纳米管、氧化石墨烯和羧甲基壳聚糖修饰的玻碳电极上的电化学行为及其含量测定

将氧化石墨烯(GO)、多壁碳纳米管(MWNTs)和羧甲基壳聚糖(CMCS)超声混合后滴涂到玻碳电极(GCE)基体上得到修饰电极(MWNTs/GO/CMCS/GCE),采用循环伏安法(CV)考察NO2-和L-色氨酸(L-Trp)在修饰电极上的电化学行为。计算得MWNTs/GO/CMCS/GCE的有效面积为3.243 0×10-6cm2,电极膜表面积明显增加,加速了电子转移,有利于被测物质的吸附和富集。结果表明:NO2-(在pH 4.7磷酸盐缓冲溶液中)和L-Trp(在pH 4.0乙酸-乙酸钠缓冲溶液中)在该修饰电极上分别有明显的电催化氧化作用;两者的浓度依次在1.0×10-7~3.5×10-1 mol·L-1和1.0×10-8~2.7×10-1 mol·L-1内与其相应的氧化峰电流值之间呈线性关系,其检出限(3S/N)依次为1.2×10-8,5.0×10-8 mol·L-1。方法用于腐败生菜中NO2-含量和模拟样品中L-Trp含量的CV测定,所得测定结果分别与紫外-可见分光光度法和荧光光度法的测定结果相符。     

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.     

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.     

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.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.