纳米二氧化钛分离富集和ICP-AES测定水样中Cr(Ⅵ)/Cr(Ⅲ)

利用ＩＣＰ－ＡＥＳ研究了纳米ＴｉＯ２材料对Ｃｒ（Ⅵ）／Ｃｒ（Ⅲ）的吸附性能,并将其用于水样中铬的形态分析。结果表明,该法对１０ｍＬ试样测定Ｃｒ（Ⅵ）和Ｃｒ（Ⅲ）的检测限分别为６１ｎｇ／ｍＬ和４５ｎｇ／ｍＬ,其浓度在０．１～１０ｕｇ／ｍＬ范围内线性关系良好,５０倍量的Ｃｒ（Ⅵ）对Ｃｒ（Ⅲ）的检测不产生干扰。本法测定Ｃｒ（Ⅵ）和Ｃｒ（Ⅲ）的相对标准偏差分别为３．６％和４．２％（ｃ＝２．０ｕｇ／ｍＬ,ｎ     

微乳液-SAF体系测定Cr(Ⅵ)

研究了在溴化十六烷基三甲基铵（ＣＴＭＡＢ）／正戊醇／正庚烷／水组成的阳离子型微乳液中Ｃｒ（Ⅵ）与水杨基荧光酮（ＳＡＦ）的显色反应。结果表明，微乳液对Ｃｒ（Ⅵ）－ＳＡＦ显色体系有较好的增敏作用。在ｐＨ６．７～６．９的（ＣＨ２）６Ｎ４－ＨＣｌ缓冲溶液中，经７０℃水浴加热１０～１５ｍｉｎ，Ｃｒ（Ⅵ）－ＳＡＦ在微乳液介质中形成一紫红色配合物，ε５６６达１．２３×１０５Ｌ·ｍｏｌ－１·ｃｍ－１，Ｃｒ（Ⅵ）浓度在每２５ｍＬ０～６μｇ范围内遵守比尔定律。在ＣＹＤＴＡ和ＮａＦ掩蔽下，对实际水样进行测定，结果满意。     

Cr(Ⅵ)与N,N-二乙基-1,4-苯二胺的显色反应及其应用研究

研究了铬与Ｎ,Ｎ－二乙基－１,４－苯二胺的显色反应,提出光度法测定微量Ｃｒ（Ⅲ）和Ｃｒ（Ⅵ）的新方法。用环己二胺四乙酸掩蔽Ｃｒ（Ⅲ）,显色测定Ｃｒ（Ⅵ）;Ｃｒ（Ⅲ）不掩蔽并氧化成Ｃｒ（Ⅵ）,显色测总铬。方法显色迅速,显色稳定时间长,在３－４５℃范围几乎不受温度影响。线性范围的质量浓度为０－５０μｇ／２５ｍＬ,λｍａｘ＝５５０ｎｍ,ε５５０＝４．９×１０＾４Ｌ·ｍｏｌ＾－１·ｃｍ＾－１,相对标准偏差     

二安替比林邻溴苯基甲烷光度法测定环境水样中的Cr(Ⅲ)及Cr(Ⅵ)

研究了在磷酸介质中，Ｍｎ（Ⅱ）和吐温２０协同作用下，二安替比林邻溴苯基甲烷（ＤＡｏＢＭ）和Ｃｒ（Ⅵ）生成橙色产物，λｍａｘ＝４８０ｎｍ，ε＝９．１９×１０５Ｌ·ｍｏｌ－１·ｃｍ－１，Ｃｒ（Ⅵ）含量在每５０ｍＬ０～３．０μｇ内符合比尔定律。结合离子交换分离，方法用于环境水样中Ｃｒ（Ⅲ）及Ｃｒ（Ⅵ）的分析，结果满意。     

Cr（VI）及Cr（Ⅲ）混合物中Cr（Ⅵ）的原子吸收测定：Cr（TTA）3…

在ｐＨ５．７的乙酸－乙酸钠缓冲介质中，噻吩甲酰三氟丙酮（ＴＴＡ）与Ｃｒ（Ⅲ）络合，生成的络合物具有挥发性。Ｃｒ（Ⅵ）在同样条件下不发生反应。利用此特点可实现Ｃｒ（Ⅵ）和Ｃｒ（Ⅲ）在石墨炉内分离并测定Ｃｒ（Ⅵ）。研究了影响Ｃｒ（Ⅲ）与ＴＴＡ络合的反应酸度、试剂加入量、静置时间等条件，并对石墨炉内定量挥发Ｃｒ（Ⅲ），保留Ｃｒ（Ⅵ）的原子化条件进行了探讨，所拟定的方法用于合成水样分析，获得满意结果。     

铬(Ⅵ)在过氧化氢氧化碘离子反应中的动力学行为的研究

铬（Ⅵ）在过氧化氢氧化碘离子反应中的动力学行为的研究朱仲良,顾志澄,陈荣妹（同济大学化学系,上海,２０００９２）（武进化学工业公司,常州）关键词铬（Ⅵ）－碘离子－过氧化氢体系,动力学分析,反应级数长期以来Ｃｒ（Ⅵ）和Ｍｏ（Ⅵ）一直作为稀硫酸介质中Ｈ２...     

化学修饰石墨探针预富集－石墨炉原子吸收法测定Cr（Ⅵ）和Cr（Ⅲ）

本文将化学修饰石墨探针选择性预分离富集和石墨炉探针原子化测定的高灵敏度结合起来，建立了用ＴＯＰＯ修饰的石墨探针络合富集Ｃｒ（Ⅵ）、Ｎａｆｉｏｎ修饰的石墨探针交换富集Ｃｒ（Ⅲ）的双修饰石墨探针顺序预分离富集、石墨炉探针原子化法测定水体中Ｃｒ（Ⅵ）和Ｃｒ（Ⅲ）的方法。Ｃｒ（Ⅲ）的检出限为１．０３ｎｇ／ｍＬ，线性范围为０～５１ｎｇ／ｍＬ。Ｃｒ（Ⅵ）的检出限为０．３７ｎｇ／ｍＬ，线性范围为０～８１ｎｇ／ｍＬ。用Ｃｒ（Ⅲ）与Ｃｒ（Ⅵ）合成样品进行回收实验，回收率对Ｃｒ（Ⅲ）与Ｃｒ（Ⅵ）分别为９５％～９８％与９８％～１０２％，利用所建立的方法测定了清华运河水样和实验室自来水样，获得了满意的结果。     

偶氮氯膦pA褪色分光光度法测定铬(Ⅵ)

1 引 言2－（４－氯－２－膦酸基苯偶氮）－７－（４－乙酰基苯偶氮）－ｌ，８－二羟基－３，６－萘二磺酸（简称偶氮氯膦ｐＡ）是测定稀土金属及钯、铑等贵金属离子的灵敏显色剂。实验发现Ｃｒ２Ｏ_７～（２－）离子在酸性介质中能使偶氮氯膦ｐＡ氧化褪色，且褪色程度与Ｃｒ２Ｏ_７～（２－）的含量呈线性关系，由此建立了测定微量铬（Ⅵ）的分光光度新方法。该方法所用试剂种类少，且在水相中进行，因而简单快速。Ｃｒ２Ｏ_７～（２－）在０．０４～ｌ．２０ ｍｇ／Ｌ范围内符合比尔定律，表观摩尔吸光系数ε５５０＝３．３３ ×１０～５…     

测定电镀废水中痕量Cr(Ⅵ)的高灵敏光度法

利用偶氮胂Ⅲ与Ｃｒ２Ｏ７２ － 的褪色反应, 对含Ｃｒ６ ＋ 电镀废水中痕量铬（ Ⅵ） 进行测定。结果表明, 在硝酸介质中褪色反应具有高的灵敏度, 反应产物的摩尔吸光系数为３ ．９ ×１０６ Ｌ·ｍｏｌ － １ ·ｃｍ － １ 。铬（ Ⅵ） 含量在０ ．０ ～４０ ．０ μｇ／Ｌ 范围内服从比耳定律。 该法用于测定电镀废水中的铬（ Ⅵ） , 得到了满意的结果。     

纳米氧化镁对Cr(Ⅵ)、Cr(Ⅲ)和Cu(Ⅱ)的吸附特性

采用乳液法制备不同形貌的花状和片状MgO纳米粒子并研究其对Cr(Ⅵ)、Cr(Ⅲ)和Cu(Ⅱ)的吸附性能。运用静态吸附实验考察吸附时间和吸附剂MgO用量对Cr(Ⅵ)、Cr(Ⅲ)和Cu(Ⅱ)的去除率影响,探讨MgO纳米粒子的微观机构对其吸附性能的影响机制。结果表明,花状MgO和片状MgO对Cu(Ⅱ)、Cr(Ⅵ)和Cr(Ⅲ)离子表现出优异的吸附性能,对金属离子的去除效果是Cu(Ⅱ)Cr(Ⅵ)Cr(Ⅲ),5min基本达到吸附平衡;花状MgO对金属离子Cr(Ⅵ)和Cr(Ⅲ)的吸附性能明显优于片状MgO,这归因于比表面积大、多孔结构的花状MgO为金属离子提供更多的吸附活性位。与Temkin模型和Freundlich模型相比,Langmuir等温吸附模型更符合MgO样品在含Cu(Ⅱ)离子溶液体系中对Cr(Ⅵ)和Cr(Ⅲ)离子的吸附过程,这意味着Cr(Ⅵ)和Cr(Ⅲ)离子在MgO纳米粒子表面的吸附属于单分子层吸附。花状和片状MgO对金属铬离子的吸附行为符合伪一级动力学模型。     

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.     

Studies of Photoionization of CF3 I by Femtosecond Time-resolved Mass Spectrometry

The multi-photon dissociative photoionization dynamics of CF3I has been studied with femtosecond two-color pump-probe time of flight mass spectra at a pump pulse of 265 nm and a probe pulse of 398 nm. The life constants of CF3I+ and its fragment ions CF3+ and I+ are obtained as (96±7), (198±130) and (167±6)fs, respectively. The multi-photon dynamics leading to these ions differ. CF3I+ corresponds to a (1+2′) transition with one-photon pump excitation to the A band of CF3I. CF3+ are mainly formed by a tow-photon probe excitation to the CF3+ with subsequent dissociation of parent ions. I+ are produced in (2+2′) combined with (1+1′+2′) process. The results provide information on the multi-photon pathways involved.