电位滴定法测定工业废水中铬

报道了以氨三乙酸(NTA，活化剂)存在下，Mn(Ⅱ)催化高碘酸钾氧化孔雀绿的反应指示终点，孔雀绿电极作指示电极用催化电位滴定法测定工业废水中铬的方法。该法不需对样品进行复杂分离，操作简单方便，终点灵敏、准确度高，重现性较好。试验对鞣革废水及电镀废水中的铬进行测定并与火焰原子吸收光谱法比较，结果满意。用标准加入法测得的平均回收率为99．62％，RSD为0．94％。     

催化电位滴定法测定铬鞣剂中铬(Ⅲ)

报道了以氨三乙酸存在下锰(Ⅱ)催化KIO4氧化结晶紫的反应指示终点,结晶紫电极作指示电极用催化电位滴定法测定铬鞣剂中Cr(Ⅲ)的方法。该法终点灵敏、准确度高、重现性好,结果满意,用标准加入法测得的平均回收率为100.03%,RSD为0.24%。     

催化电位滴定法测定铬鞣中铬（III）

报道了以氨三乙酸存在下锰（II）催化KIO4氧化结晶紫的反应指示终点,结晶紫电极作指示电极用催化电位滴定法测定的铬鞣剂中Cr(III)的方法,该法终点灵敏,准确度高,重现性好,结果满意,用标准加入法测得的平均回收率为100．03％,RSD为0．24％。     

离子选择性电极催化电位法测定植物中的微量锰

锰是植物中的微量元素之一,分析测定植物中锰含量,对于研究锰在植物叶绿素的合成和碳水化合物的运输中的生理功能等将有重要意义。本文用离子选择性电极催化电位法—高碘酸根电极指示跟踪锰(Ⅱ)催化     

催化电位滴定法测定奶粉中微量锌

报道了一种以氨三乙酸(NTA,活化剂)存在下锰(Ⅱ)催化KIO4氧化甲基紫的反应指示滴定终点,自制的甲基紫选择性电极为指示电极,用催化电位滴定法测定奶粉中微量锌的新方法。将该方法用于奶粉中锌的测定,结果与火焰原子吸收光谱法一致,样品平均回收率为99．0％,RSD为1．1％。     

半自动催化光度滴定法测定生物样品中的锰

报道了以催化光度返滴定法来测定锰含量的新方法 .以EDTA作络合剂 ,Mn(II)为返滴定剂 ,滴定终点由锰 (II)催化高碘酸钾氧化结晶紫的褪色反应来指示 .在体系中加入表面活性剂 (TritonX - 10 0 )可改善反应条件 ,使测定可在室温下进行 ,用半自动化装置使操作连续、快速、简便 .用该方法测定鸡肝、人发、啤酒中的锰含量 ,结果与原子吸收光谱法所得结果相吻合     

中草药中微量锰的测定

以Ｍｎ＾２＋催化ＫＩＯ４氧化结晶紫为指示反应，用催化滴定法测定了菌陈、丹皮等六种中草药中的锰含量，并用原子吸收分光光度法作对照试验，结果满意。实验表明，该法兼具催化动力学分析法的高灵敏度和滴定分析的高准确度的特点，且仪器简单，操作方便。     

双指示物质动力学分析法研究 Ⅰ.锰(Ⅱ)-乙二胺四乙酸二钠-铬(Ⅳ)催化体系

本文报道了双指示物质测定痕量锰的新催化光度法.探讨了该方法的理论基础,确定了催化体系的适宜反应条件.本法灵敏度比单指示物质法高6.4倍,用于测定谷物样品中锰.     

双指示物质动力学分析法研究Ⅰ.锰(Ⅱ)-乙二胺四乙酸二钠-铬(Ⅵ)催化体系

本文报道了双指示物质测定痕量锰的新催化光度法, 探讨了该方法的理论基础,确定了催化体系的适宜反应条件.本办法灵敏度比单指示物质法高6.4倍,用于测定谷物样品中锰.     

动力极谱法测定海水中痕量锰

本文研究了孔雀绿极谐波性能,确定在醋酸-醋酸钠(pH=4.2)介质中,在示波极谱仪上可得到良好的极谱波。峰电位为-0.67伏(S.C.E)。用极谱法研究锰催化高碘酸钾氧化孔雀绿反应的机理。介绍了不需分离而直接测定海水中痕量锰的方法。其灵敏度可达0.2μg/l,对含10.1/μg锰的海水样进行11次平行测定,相对标准偏差为4.1%。本法亦适合自来水、河水中锰的分析。     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

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.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.