DA和AA在CPB现场修饰碳糊电极上的电化学行为及电分析方法

研究了多巴胺(Dopamine,DA)和抗坏血酸(Ascorbic acid,AA)在裸碳糊电极(Carbon Paste Electrode,CPE)和溴化十六烷基吡啶(Cetylpyrid bromide,CPB)现场修饰碳糊电极(CPB/CPE)上的电化学行为。与CPE相比,DA在CPB/CPE上与CPB产生了静电排斥作用,氧化峰电流减小,氧化峰电位正移;AA和CPB产生了静电吸引作用,氧化峰电流增大,氧化峰电位负移。循环伏安法研究表明,在DA和AA共存体系中,DA和AA的氧化峰电位相差约340 mV,以此建立了DA和AA的电化学同时测定方法。微分脉冲伏安法研究结果表明,DA和AA氧化峰电流和其相应浓度在1.0×10-5~5.0×10-3mol/L的范围内呈良好的线性关系。本方法也可用于DA和AA共存体系中选择性测定DA。在100倍AA共存时DA的检出限为2.0×10-6mol/L,CPB修饰碳糊电极直接用于市售针剂中DA含量的测定,所得结果令人满意。     

尿酸和抗坏血酸在CPB现场修饰碳糊电极上的电化学行为

研究了尿酸(UA)和抗坏血酸(AA)在裸碳糊电极(CPE)和溴化十六烷基吡啶CPB)现场修饰碳糊电极(CPB/CPE)上的电化学行为,研究结果表明在PBS(pH=6.8)缓冲溶液中,UA和AA在CPE和CPB/CPE电极上的氧化均为一不可逆过程,在CPB/CPE上UA和AA的氧化峰电位负移,氧化峰电流增大,CPB/CPE对UA和AA的电化学氧化产生了促进作用。用电化学方法测得了UA和AA在CPE和CPB/CPE上的动力学参数如电荷转移系数α,扩散系数D,反应级数和反应速率常数k1。     

抗坏血酸和尿酸在CPB现场修饰碳糊电极上的电化学行为及其选择性测定应用

研究了抗坏血酸(AA)和尿酸(UA)在裸碳糊电极(CPE)和溴化十六烷基吡啶(CPB)现场修饰碳糊电极(CPB/CPE)上的电化学行为.研究结果表明,在PBS水溶液中,AA和UA在CPB/CPE上氧化峰电流增加,峰电位负移,CPB/CPE对AA,UA电化学氧化反应产生了催化作用.微分脉冲法研究表明,在AA和UA共存体系中,AA和UA的氧化峰电位相差约220 mV,以此建立了AA和UA的电化学选择性测定方法.AA和UA的微分脉冲伏安氧化峰电流和其相应浓度分别在7.0×10-6～6.0×10-3 mol/L和5.0×10-7～6.0×10-4 mol/L的范围内呈良好的线性关系.在200倍AA共存时UA的检出限为5.0×10-6 mol/L,CPB修饰的碳糊电极直接应用于实际尿样中UA的测定.     

多巴胺在聚溴甲酚绿修饰碳糊电极上的电化学行为

以碳糊电极(CPE)为基底,采用电聚合方法制备出聚溴甲酚绿修饰碳糊电极(PBG/CPE),运用循环伏安法(CV)对修饰电极进行表征,通过扫描电子显微镜(SEM)对聚合膜的表面形貌进行观察分析。利用PBG/CPE研究了多巴胺(DA)的电化学行为,并对最佳实验条件进行了探讨。研究结果表明:DA在PBG/CPE上于0.32V和0.24V处分别出现一对可逆氧化还原峰,PBG/CPE对DA有显著的催化作用,该催化过程受吸附控制。DA催化氧化还原峰电流与其浓度在1.0×10-5~2.0×10-4mol/L范围内呈现良好的线性关系,检出限为1.0×10-6mol/L。     

多巴胺在聚亚甲基蓝/石墨烯修饰电极上的电化学行为研究

利用电聚合方法在石墨烯修饰的玻碳电极表面制备了聚亚甲基蓝/石墨烯修饰电极(PMB/GH/GCE)。采用循环伏安法(CV)和差分脉冲伏安法(DPV)研究了多巴胺(DA)和抗坏血酸(AA)在该修饰电极上的电化学行为。在pH 6.9的磷酸盐缓冲溶液中,DA和AA分别在0.208 V和-0.108 V处产生灵敏的氧化峰,与其在聚亚甲基蓝和石墨烯单层修饰电极上的电化学行为相比,两者的峰电流明显增加,峰电位差达316 mV。研究表明,电聚合方法使亚甲基蓝牢固地非共价修饰到石墨烯上,并产生协同增效作用,较好地提高了电极的灵敏度和分子识别性能,有利于在大量AA存在下实现对DA的选择性测定。在1.00×10-3mol/L AA的存在下,DA的差分脉冲伏安法峰电流与其浓度在1.00×10-7～5.00×10-3mol/L范围内呈良好的线性关系,检出限达1.00×10-8mol/L。将该方法用于盐酸多巴胺注射液的测定,结果满意。     

聚茜素红功能化碳纳米管修饰电极对多巴胺和抗坏血酸的电化学研究

采用电聚合方法将茜素红非共价修饰到碳纳米管上,制备了聚茜素红/碳纳米管修饰电极.以多巴胺(DA)和抗坏血酸(AA)为模型化合物,研究该修饰电极的电催化作用.结果表明:电聚合法使茜素红牢固地修饰到碳纳米管上,能显著提高电极的灵敏度和分子识别性能.DA和AA的氧化峰位分离达240 mV.在AA的存在下,DA的差分脉冲伏安法峰电流在1×10-7～1×10-5 mol/L范围内呈良好的线性关系,检测下限达1×10-7 mol/L.     

呋塞米在APTS与石墨烯复合修饰碳糊电极上的电化学行为及电分析方法研究

研究了呋塞米(FUR)在3-氨基丙基三氧基硅烷(APTS)和石墨烯(RGO)复合修饰碳糊电极(APTSRGO/CPE)上的电化学行为。实验结果表明,与CPE相比,APTS-RGO/CPE对呋塞米的电化学氧化显著增强,其氧化峰电流增加3.4倍。同时采用循环伏安法(CV)、计时电流法(CA)测定了FUR在APTS-RGO/CPE上的电极反应动力学参数,用微分脉冲伏安法(DPV)测得FUR氧化峰电流与浓度的线性范围为1.3~330 mg/L,检出限(LOD,S/N=3)为1.1×10-2mg/L。将该修饰电极应用于市售呋塞米片剂的检测,相对标准偏差(RSD)为0.4%~4.4%,回收率为98.5%~99.7%,检测结果符合电化学定量测定要求。     

多巴胺在聚中性红修饰碳纤维微电极上的电化学行为

利用电聚合方法制备了聚中性红(PNR)修饰碳纤维微电极.根据循环伏安(CV)、电位阶跃实验结果,得出了多巴胺(DA)在PNR膜中的表观扩散系数D0=7.0×10-9cm2/s、膜表面表观标准电子转移速率常数κ=0.55 cm/s;该电极对DA响应灵敏,对抗坏血酸具有良好的抗干扰能力,可望用于活体中DA的测定.     

抗坏血酸在钴酞菁修饰碳糊电极上的电化学行为

采用掺杂的方法制备了钴酞菁修饰碳糊电极(CoPc/CPE)。利用循环伏安法(CV)和交流阻抗谱(EIS)对修饰电极的电化学性能进行研究,并采用扫描电子显微镜(SEM)观察其表面形貌。运用循环伏安法(CV)、线性扫描伏安法(LSV)、计时电流法(CA)以及计时电量法(CC)研究了抗坏血酸在该修饰电极上的电化学行为并计算了电极过程的动力学参数。结果表明CoPc/CPE对抗坏血酸有明显的电催化作用,抗坏血酸在该修饰电极上的电极反应受扩散控制。计算了抗坏血酸的部分动力学参数:电荷转移系数(α=0.993),扩散系数(D=1.36×10~(-4)cm~2·s~(-1))以及电极反应速率常数(kf=1.62×10~(-2)cm·s~(-1));采用LSV测得抗坏血酸的氧化峰电流与浓度在1.00×10~(-3)(1.00×10~(-6)mol·L~(-1)范围内表现出良好的线性关系,检出限为5.00×10~(-7)mol·L~(-1)(S/N=3)。该修饰电极制备方法简单、灵敏度高、稳定性好,用于实际样品中抗坏血酸的含量分析,结果令人满意。     

纳米Cu_2O/氮掺杂石墨烯复合修饰电极对多巴胺的电化学分析研究

本文通过化学还原法制备纳米Cu_2O/氮掺杂石墨烯(NG)复合材料,用于构建一种新型的多巴胺(DA)电化学传感器。采用X射线衍射法和扫描电镜对纳米Cu_2O/氮掺杂石墨烯复合材料进行表征。在pH为7.0的磷酸盐缓冲液中,采用循环伏安法和计时电流法分别研究了DA在纳米Cu_2O/氮掺杂石墨烯复合修饰电极上的电化学行为。结果表明,该修饰电极对DA表现出显著的电催化活性,且DA在修饰电极上的反应受吸附控制。在最佳实验条件下,催化电流与DA的浓度在0.5~700μmol/L之间呈线性关系(r=0.9943),检测限达0.17μmol/L。该修饰电极的选择性高、重复性和再现性好。方法用于实际样品中DA的检测,获得结果较好。     

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.