流动注射双安培法测定没食子酸

基于没食子酸在经预阳极化的铂电极上的催化氧化和不可逆电对的双安培检测原理,使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0V时,通过偶合没食子酸在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构建流动注射双安培检测体系,建立了一种流动注射双安培直接检测没食子酸的新方法。常用药物赋形剂、无机离子以及生化样品中一些共存物均不干扰没食子酸测定。没食子酸的氧化电流与其浓度在1.0×10-5～1.0×10-3mol/L范围内有良好的线性关系。检出限为5.0×10-6mol/L。连续20次测定2.0×10-4mol/L没食子酸,电流值的RSD为1.7%。该方法有很高的选择性和灵敏度,样品处理方法简单快速,适于在线分析。     

流动注射双安培法测定葛根素

利用不可逆电对的双安培检测原理,建立了流动注射双安培直接检测葛根素的电化学新方法.使用经过恒电位预阳极化处理的双铂电极,通过耦合葛根素在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系.在外加电位差为0.2 V时,pH 8.94的碳酸钠-碳酸氢钠缓冲溶液中,测得氧化电流与葛根素浓度在6.0×10-6～1.0×10-3 mol/L范围内呈线性关系(r=0.997 4,n=8),检出限为1.0×10-6 mol/L.连续40次测定6.0 ×10-4 mol/L的葛根素,RSD=1.58%.用该方法对葛根素含量进行了测定,结果令人满意.     

流动注射双安培法测定橙皮甙

基于橙皮甙的不可逆氧化和氧化铂的不可逆还原体系构成了双安培法直接检测橙皮甙的新方法。在外加电压为0.2 V时,通过偶合橙皮甙在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系。在pH 8.95的B-R缓冲溶液中,测得橙皮甙的氧化电流与其浓度在6.0×10-6~8.0×10-4mol/L范围内呈良好的线性关系(r=0.9997,n=11),检出限为1.0×10-6mol/L。连续30次测定6.0×10-4mol/L橙皮甙,其峰电流相对标准偏差(RSD)为3.2%,常用药物赋形剂和无机离子均不干扰橙皮甙的测定。方法已用于江中健胃消食片中橙皮甙含量的测定。     

流动注射双安培法测定环境水样中苯酚

基于苯酚在铂电极上的氧化和不可逆电对的双安培检测原理,建立了流动注射双安培测定环境水样中苯酚的新方法。通过偶合苯酚在一支铂电极上的氧化和KMnO4在另一支铂电极上的还原这两个不可逆电对,构建双安培检测体系,在外加电位差为0V时,苯酚的氧化电流与其浓度在1.0×10-6～1.0×10-4mol/L范围内呈线性关系,检出限为5.0×10-7mol/L,连续30次测定2.0×10-5mol/L苯酚,电流值RSD为1.4%。用本方法分别对几种含酚废水样品中苯酚含量进行测量,并与4 氨基安替比啉比色法进行了对照。     

流动注射双安培法测定辛弗林

基于辛弗林在经预阳极化的铂电极上的催化氧化和不可逆电对的双安培检测原理,建立了流动注射双安培直接检测辛弗林的电化学分析新方法.本法使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0 V时,通过偶合辛弗林在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系.实验发现,在pH=10.88的BR缓冲溶液中,测得氧化电流与辛弗林浓度在6.0×10-6～1.0×10-3 mol/L范围内呈良好的线性关系(r=0.9990,n=8).检出限为2.0×10-6 mol/L.连续20次测定5.0×10-4 mol/L辛弗林,电流值的相对标准偏差(RSD)为2.2%.方法用于香砂养胃丸中辛弗林含量的测定,结果满意.     

流动注射双安培法测定硫脲

建立了流动注射双安培法检测硫脲的新方法。使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0.30 V时,通过偶合硫脲在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系。结果表明,在pH=5.3的HAc-NaAc缓冲液中,测得硫脲氧化电流与其浓度在1.0×10-5~1.0×10-3mol/L范围内呈线性关系(r=0.9989),检出限为5.0×10-6mol/L。对于6.0×10-4mol/L硫脲,测定的相对标准偏差(RSD)为1.80%(n=23)。该法样品处理简单,且有很高的选择性和灵敏度,结果令人满意。     

流动注射双安培法测定联苯胺

基于联苯胺在预阳极化的铂电极上的催化氧化和不可逆电对的双安培检测原理,建立流动注射双安培直接检测联苯胺的新方法。使用经过恒电位预阳极化处理的双铂电极,在外加电压差为0.3 V时,通过偶合联苯胺在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,建立一种快速准确的在线分析测定联苯胺的流动注射双安培检测法。结果表明:在pH 5.2的KHC8H4O4-NaOH缓冲溶液中,外加电位差为0.3 V时测得联苯胺的氧化电流与其浓度在8.0×10-6~3.0×10-3mol/L范围内呈线性关系(r=0.9962,n=11)。检出限为1.0×10-6mol/L。连续20次测定1.0×10-4mol/L的联苯胺溶液,电流值RSD=1.9%。电极的稳定性良好,常见无机离子和有机物均不干扰测定。用该方法对样品中联苯胺进行了测定,样品处理方法简单,且有很高的选择性和灵敏性。     

流动注射双安培法测定尿囊素的研究

基于尿囊素的不可逆氧化和氧化铂的不可逆还原构成的双安培检测体系,建立了测定尿囊素的电化学新方法.在外加电压为0.10V时,通过偶合尿囊素在一支电极上的氧化及氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测新体系.在pH=2.2的邻苯二甲酸氢钾-盐酸缓冲溶液中,测得尿囊素的氧化电流与其浓度在1.0×1...     

流动注射双安培法测定苯胺

应用苯胺在预阳极化的铂电极上的催化氧化过程,建立了流动注射双安培法直接检测苯胺的电化学新方法.在外加电压差为0.30V时,苯胺在预阳极化处理后铂电极上的和氧化铂在另一支铂电极上的还原为两个不可逆电极过程,在pH=9.94的碳酸钠-碳酸氢钠缓冲溶液中,苯胺的氧化电流与其浓度在4.0×10-6～1.0×10-4 mol/L...     

流动注射双安培法测定尿酸

基于尿酸在预阳极化的铂电极上的催化氧化和不可逆电对的双安培检测原理,使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0 V时,通过偶合尿酸在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,建立了一种快速准确在线分析测定尿酸的电化学新方法———流动注射双安培检测法。在外加电位差为0 V时尿酸的氧化电流与其浓度在1.0×10-6~8.0×10-3mol/L范围内呈线性关系(r=0.998 5,n=11),检出限为5.0×10-7mol/L。连续28次测定4.0×10-4mol/L尿酸,电流值RSD为2.5%。电极的稳定性良好,常见无机离子和有机离子均不干扰测定。用该方法对尿酸含量进行了测定,样品处理简单,且有很高的选择性和灵敏度,结果令人满意。     

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%.     

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.     

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.     

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.