催化动力学光度法测定人发中的痕量铜

在NH3.H2O介质中,微量Cu(Ⅱ)能显著催化过硫酸铵氧化溴百里酚蓝的褪色反应。研究了该褪色反应的最佳反应条件,建立了催化动力学测定铜的新分析方法。本法测定铜的线性范围在0.00~0.08μg.mL-1。回收率在97.5%~99.0%之间,RSD为0.6%~1.6%,检出限为4.8×10-8g.L-1。用于人发中痕量Cu(Ⅱ)的测定,结果满意。     

酶催化荧光法测定河流污水中的痕量Cu(Ⅱ)

基于Tris-HCl缓冲介质中,血红蛋白对H2O2氧化L-酪氨酸体系有强烈催化作用,而Cu(Ⅱ)对这一反应体系具有强烈抑制作用,据此建立了一种酶催化荧光法测定Cu(Ⅱ)的新方法。荧光强度的变化与Cu(Ⅱ)的浓度在2.7~530μg/L范围内呈线性关系,检出限为0.6μg/L;对270μg/L Cu(Ⅱ)溶液进行11次平行测定其相对标准偏差为3.60%。该方法已成功应用于河流污水中痕量Cu(Ⅱ)的测定。     

催化褪色光度法测定痕量铜的新体系

研究了硫酸介质中铜 ( )催化高碘酸钾氧化中性红褪色反应的适宜条件 ,建立了动力学光度法测定痕量 Cu( )的新方法。Cu( )的质量浓度在 0～0 .5μg/2 5 m L范围内与ΔA值呈良好的线性关系 ,检出限为 3.5× 10 -8g/L。已用于饮用水和海产品中铜的测定     

催化激光热透镜光谱法测定铜

基于铜催化邻苯二胺氧化反应,以激光热透镜光谱法测定微量铜,讨论了测定条件的影响。结果表明,该方法测定灵敏度高,在0．2－1．2μg/L铜（Ⅱ）浓度范围内呈线性关系,重现性及回收率实验均取得满意的结果。     

KBrO_3-邻氨基酚体系催化动力学光度法测定微量Cu(Ⅱ)

在pH为4.5的HAc-NaAc缓冲溶液介质中,Cu(Ⅱ)能催化KBrO_3氧化邻氨基酚而显色,据此建立了测定微量Cu(Ⅱ)的新方法。方法的测定波长为430nm,反应温度为60℃时控制反应时间为6min,Cu(Ⅱ)在0.10~1.2μg/mL范围内吸光度与Cu(Ⅱ)的浓度呈良好的线性关系,相关系数r为0.9971。方法用于测定冶炼厂电解银废液中铜含量,相对标准偏差为2.49%(n=6),加标回收率在91.6%~99.4%之间。     

高碘酸钾氧化刚果红和萘酚绿B褪色催化动力学光度法测定茶叶中的微量锰

在NH3-NH4Cl缓冲溶液介质中,以氨三乙酸为活化剂,利用微量Mn(Ⅱ)对KIO4氧化刚果红和萘酚绿B的褪色反应具有催化作用,通过测量480nm和720nm波长处催化和非催化体系吸光度的变化,建立了双波长双指示剂催化动力学光度法测定微量Mn(Ⅱ)的新方法。方法的线性范围为2.4～40μg/L,检出限为0.301μg/L。用于茶叶中锰的测定,加标回收率为96.2%～101.4%。     

过氧化氢氧化二氯荧光素动力学荧光法测定痕量铜

研究了在氨性介质中，铜(Ⅱ)催化过氧化氢氧化二氯荧光素的褪色反应，建立了动力学荧光法测定痕量铜的新方法。方法的检出限为0．06μg/L，测定铜的线性范围为0．2～4．0μg/L。已用于人发、茶叶和自来水中痕量铜的测定。     

酸性靛蓝-H_2O_2-OH~-化学发光测定Cu(Ⅱ)的新体系

本文拟定了酸性绽蓝-H_2O_2-OH-体系测定微量Cu(Ⅱ)的新化学发光分析法。该方法测定Cu(Ⅱ)的检测限为0.3μg/L,线性范围为10～200μg/L。三十余种共存离子中,Fe(Ⅲ)、Cr(Ⅲ)等离子对测定有干扰。     

双波长双指示物催化光度法测定水中痕量铜

研究了在pH5.5的Na2HPO4-NaH2PO4缓冲溶液介质中，痕量Cu（Ⅱ）催化过氧化氢氧化吖啶黄和酸性品红褪色的指示反应。通过测量450nm和540nm处，催化反应体系和非催化反应体系吸光度的变化，利用铜离子浓度与两波长处吸光度差值的和呈线性关系，建立了双波长双指示物催化光度法测定痕量铜的新方法。在最佳实验条件下，测定铜的线性范围为0．60～32μg/L，检出限为0．24μg/L。该方法操作简单，灵敏度高，选择性好，用于水样中痕量铜的测定，获得满意结果。     

Cu(Ⅱ)-KIO4-胭脂红-1,10-菲罗啉体系催化动力学光度法测定人发中痕量铜

基于pH6.5的Na2HPO4-NaH2PO4缓冲介质中铜离子对高碘酸钾氧化胭脂红褪色反应的催化作用,提出了催化动力学光度法测定痕量铜的新方法.研究了该方法的适宜反应条件,方法的检出限为1.1×10-7g/L Cu(Ⅱ),表观摩尔系数ε=7.8×105L·mol-1·cm-1,线性范围为0～0.5μg/10mLCu(Ⅱ),方法已用于人发中痕量铜的测定.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

Exploring the scope of the Gewald reaction: Expansion to a four-component process

An efficient four-component reaction was developed to take advantage of the reactivity of the 2-aminothiophene-3-carbonitrile functionality, which is obtained during the classical three-component Gewald reaction. Various α-methylene bearing ketones were reacted with malononitrile, elemental sulfur, and aryl/heteroarylnitrile derivatives in t-BuOH/NaOH to afford 2-arylthieno[2,3-d]pyrimidin-4-amines in high yields. Preliminary studies revealed the photophysical properties of the products and their potential for use as metal sensors.