高碘酸钾氧化酚藏花红褪色催化动力学光度法测定食品中的痕量亚硝酸根

基于在硫酸介质中,亚硝酸根对高碘酸钾氧化酚藏花红褪色反应具有较强的催化作用,建立了测定痕量亚硝酸根的催化动力学光度法。线性范围为0．12～1．22mg/L,相关系数为0．9990,检出限为0．016mg／L。用于食品中痕量亚硝酸根的测定,测定结果的相对标准偏差为2、6％～4．2％,回收率为97％．103％。     

以酚藏花红为指示剂催化荧光法测定痕量亚硝酸根的研究

基于稀磷酸介质中，亚硝酸根对溴酸钾氧化酚藏花红反应的催化作用，建立了催化荧光法测定痕量亚硝酸根的新方法。反应在５５℃水浴中进行８ｍｉｎ，线性范围为０．２７～７．３μｇ／Ｌ，其回归方程为ΔＦ＝０．４０＋１０．９３ｃ，ｒ＝０．９９９４。用于水样中痕量亚硝酸根的测定，结果良好。     

水中亚硝酸根的表面活性剂增敏催化动力学流动注射荧光法测定

研究发现十二烷基硫酸钠对稀磷酸介质中亚硝酸根催化溴酸钾氧化藏红T有显著的增敏作用；据此建立了催化动力学流动注射荧光法测定痕量亚硝酸根的方法，方法检出限为0．2μg／L，线性范围为0．5～25．0μg／L，进样频率为72次／h；该法用于水样中亚硝酸根的测定，结果与标准方法相符。     

催化光度法测定水中痕量亚硝酸根

利用在硫酸介质中亚硝酸根催化溴酸钾氧化吖啶橙的褪色反应 ,建立了测定痕量亚硝酸根的新方法。方法检出限为 7.6× 1 0 -8mol/ L,线性范围 0～1 .1 2× 1 0 -6mol/ L。本法可用于测定雨水和自来水中的痕量亚硝酸根     

催化光度法测定水中的痕量NO2-

基于磷酸介质中亚硝酸根催化溴酸钾氧化靛蓝胭脂红的褪色反应,建立了测定水中痕量亚硝酸根的催化光度法,并利用正交试验对测定方法进行了优化,亚硝酸根的检测限为1.36×10~(-6)g/L,线性范围为0.3～2.0 μg/25mL。该法用于蔬菜及环境水样中痕量亚硝酸根的测定,结果准确。     

催化动力学光度法测定新鲜果蔬中痕量亚硝酸根

基于在稀磷酸介质中亚硝酸根对溴酸钾氧化百里酚蓝褪色反应的催化效应 ,建立了一种测定痕量亚硝酸根的催化光度法。该方法测定亚硝酸根的线性范围为 0～ 6 .5 μg/ 2 5ml,灵敏度为 0 .6 7ng·ml- 1。用于新鲜果蔬样品中痕量亚硝酸根的测定 ,结果满意     

催化光度法测定痕量亚硝酸根

基于稀磷酸介质中亚硝酸根催化溴酸钾氧化溴酚红的褪色反应,建立测定痕量亚硝酸根的新方法。方法检出限为0.58×10-6g/L,线性范围为0.5×10-6~20×10-6g/L,回收率为96%~104%。该法已用于食品中亚硝酸根的测定,结果满意。     

氧化还原荧光法测定痕量亚硝酸根

建立了碘化钾与亚硝酸根氧化还还原反应生成游离碘使异硫氰酸荧光素荧光猝灭测定痕量亚硝酸根的新方法,其线性范围为25－100ug/L,回归方程为ΔF＝7．98C－10．5,r=0.990,方法的检测限为12ug/L。本法快速,灵敏,操作简便,用于水样中痕量亚硝酸根的测定,结果良好。     

氯酸钾-灿烂甲酚蓝催化褪色光度法测定痕量亚硝酸根的研究

在0.1 mol/L硫酸介质中,亚硝酸根对KClO3氧化灿烂甲酚蓝的褪色反应具有明显的催化作用,据此建立了催化光度分析测定痕量亚硝酸根的新方法.研究了反应的适宜条件及动力学参数.在最大吸收波长630 nm及选择的最佳实验条件下,方法线性范围为0.05～0.4μg/mL,检出限为0.014μg/mL.该法直接用于雨水和湖水中痕量亚硝酸根的测定,结果满意.     

催化动力学极谱法测定痕量亚硝酸根

在硫酸介质中，痕量亚硝酸根对溴酸钾氧化酸性铬深蓝的反应有极强的催化作用，研究了最佳反应条件，发现在氨缓冲溶液中酸性铬深蓝具有良好的极谱峰，以极变法监测催化反应过程中酸性铬深蓝浓度的变化，建立了催化动力学极谱法测定痕量亚硝酸根的方法，方法的线性范围为0．20－1．34μg.ml^-1，检出限为0．088μg.ml^-1，应用于雪水，雨水中痕量亚硝酸根的测定，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.     

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.