双硫腙还原法测定痕量IO_3~-

在含IO_3~-的0,5～lmol/L盐酸溶液中,用10mL双硫腙-四氯化碳溶液进行萃取时,IO_3~-能氧化双硫腙使其在有机相中的绿色减退。借反应前后有机相中双硫腙吸光度的改变,建立了一个测定痕量IO_3~-的方法。方法的灵敏度ε=1.7×10~5,最低检出限为1.75×10~(-8)g/mL IO_3~-线性范围0.175～6.15μg/10mLIO_3~-。对于能与双硫腙(H_2Dz)螯合的金属离子如Au~(3+)、Ag~+、Cu~(2+)、Cu~+、Hg~(2+)等的干扰,可将水相调至pH3～7,先用H_2Dz-CCl_4溶液萃取除去,在此条件下,H_2Dz不还原IO_3~-。方法用于KNO_3中IO_3~-的测定,得到了满意的结果。一、仪器与试剂     

以乙基紫—IO_4~-缔合物为电活性物质的PVC膜IO_4~-离子选择电极的研制

本文研制了以乙基紫-IO_4~-缔合物为电活性物质的PVC膜IO_4~-离子选择电极,它对IO_4~-浓度在2×10~(-0)—1×10~(-1)M间的响应符合Nernst关系式,级差为56毫伏(9—12℃),响应时间小于1分钟,适宜的pH范围为3.8—6.5,内阻为1.5×10~5 欧姆左右,电极寿命在七个月以上。还进行了电极的选择性、重现性和稳定性实验,也得到较满意结果。     

3,5-Br_2-PADAP—IO_3~-—SCN~-三元离子缔合物测定微量IO_3~-的研究

研究了3,5-Br_2-PADAP在酸性介质中质子化。与IO_3~-和SCN~-形成三元离子缔合物的最佳条件,其表观摩尔吸光系数为1.4×10~5L·mol~(-1)·cm~(-1),缔合物组成比为3,5-Br_2-PADAP:IO_3~-:SCN=1:1:1。提供了测定微量IO_3~-的新方法,可用于加碘食盐及海带等样品中含碘量的测定,获得满意结果。     

碳棒涂膜式PVC膜离子选择电极的研究 1.丁基罗丹明B-AuCl_4~-离子选择电极的研制和应用

本文研制了以丁基罗丹明B-AuCl_4~-为电活性物质的碳棒涂膜式PVC膜金离子选择电极。电极对AuCl_4~-离子在1×10~(-3)-7.1×10~(-7)mol/L范围内呈能斯特响应,检测限为5.0×10~(-7)mol/L,级差为58mV(20℃)。电极内阻为0.1MΩ,响应时间小于30秒。电极稳定性、重现性良好。该电极结构简单,制作、储存方便,价格低廉,已成功用于矿样中金的测定。     

钴-5,10,15,20-四(3-甲氧基-4-羟基苯基)卟啉修饰玻碳电极的L-抗坏血酸化学传感器研究

将水合 5,10,15,20-四-(3-甲氧基-4-羟基苯基)钴卟啉(CoTMHPP)修饰在玻碳电极表面,制成CoTMHPP修饰电极.电极稳定性好且灵敏度高,对抗坏血酸有良好的电催化氧化作用,测定线性响应范围为1.0×10(-5)～1.0×10(-2)mol/L,响应时间小于12s.本文研究了电极的性质和应用,并用于药物中抗坏血酸的测定,其测定结果与碘量法一致.     

5—Br—PADAP为显色剂吸光光度法测定微量碘酸根的研究

在硫酸介质中,2-(5-溴-2-吡啶偶氮)-5-二乙氨基酚(5-Br-PADAP)与IO_3~-及SCN~-生成红色缔合物,用于吸光光度法分析微量IO_3~-,加入表面活性剂吐温-80可以提高测定的灵敏度和选择性。在最大吸收波长550nm处,可测IO_3~-浓度范围为0～2.45μg·ml~(-1),摩尔吸光系数ε为8.2×10~4,离子缔合物的组成比为5-Br-PADAP:IO_3~-:SCN~-=2:1:4。经测定硝酸钠和氯酸钾中IO_3~-的回收率为97.3％～101.5％,结果令人满意。     

还原氧化石墨烯-多壁碳纳米管复合膜负载金纳米粒子修饰玻碳电极检测双酚A

以水合肼为还原剂,采用均相还原法制备还原氧化石墨烯-多壁碳纳米管复合材料(rGO-MWCNTs),通过滴涂法将其修饰到玻碳电极(GCE)表面.以此复合材料为载体,采用电化学方法制备了金纳米粒子-还原氧化石墨烯-多壁碳纳米管复合膜修饰电极(AuNPs-rGO-MWCNTs/GCE).通过扫描电镜(SEM)、EDS能谱技术和电化学方法对此电极进行了表征.研究了双酚A在修饰电极上的电化学行为.结果表明,此电极对双酚A的电极过程具有良好的电化学活性,在0.10 mol/L PBS溶液(pH 7.0)中,微分脉冲伏安法测定双酚A的线性范围为5.0 × 10-9~1.0 × 10-7 mol/L和1.0 × 10-7~2.0 × 10-5 mol/L,检出限为1.0 ×10-9 mol/L(S/N=3). 将此电极用于模拟水样和超市购物小票样品中双酚A含量的测定,加标回收率分别为97%~110%和98%~104%.     

碳纳米管修饰电极对多巴胺和肾上腺素的电分离及同时测定

研究了多巴胺 (DA)和肾上腺素 (EP)在多壁碳纳米管 (MWNT)修饰电极上的电化学性质 ,发现该修饰电极对神经递质DA和EP有显著的增敏和电分离作用。还原峰电位差达ΔEp=390mV ,可同时测定DA和EP。DA和EP的还原峰电流与其浓度分别在 2 .0× 10 -6～ 1.0× 10 -3 mol/L和 1.0× 10 -6～ 1.0× 10 -3 mol/L浓度范围内呈良好的线性关系 ;方法的检出限分别为 1× 10 -6mol/L和 5× 10 -7mol/L。由于抗坏血酸 (AA)在MWNT修饰电极上的氧化是不可逆的 ,因此利用还原峰进行测定 ,消除了AA对DA和EP的干扰     

2-(5-溴-2-吡啶偶氮)-5-二乙氨基酚-BrO_3~--SCN-三元离子缔合物测定微量BrO_3~-的研究

本文研究了5-Br-PADAP在酸性介质中质子化,与BrO_3~-和SCN~-形成三元离子缔合物的最佳条件,其表观摩尔吸光系数ε_(540)=4.3×10~4L·mol~(-1)·cm~(-1),缔合物组成比为:5-Br-PADAP:BrO_(3-)SCN~-=1:1·1。提供了测定微量BrO_(3-)的新方法,可应用于化学试剂中微量BrO~(3-)的测定。此外,本文还探讨了反应机理。     

肾上腺素在咖啡酸修饰电极上的电化学研究

研究了咖啡酸(CFA)修饰电极的性质,测定了电极反应的动力学常数.结果表明在pH 7.0的的磷酸盐缓冲溶液中,肾上腺素(Ep)在该修饰电极上产生一灵敏的氧化峰,峰电流与Ep浓度在5.0×10-6～1.0×10-4 mol/L范围内线性关系良好,检出限为7.0×10-7 mol/L.修饰电极制备简单,稳定性好.     

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%.     

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.     

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.     

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.     

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.