推荐几个有趣的演示实验

推荐几个有趣的演示实验侯文祥，张孟冬，龙玉英（天津大学化学系３０００７２）一、ｐＨ试液的连续变色试验药品固体甲基红、甲基黄、酚酰、百里酚蓝、溴百里酚蓝；乙醇，１ｍｏｌ·Ｌ－１ＮａＯＨ，１ｍｏｌ·Ｌ－１ＨＣｌ，０．１ｍ０ｌ·Ｌ－１ＮａＯＨ。仪器２５０ｍ...     

微分电位溶出法测定人发中铜铅镉锌的研究

本文报道了０．００２５ｍｏｌ·Ｌ￣（－１）ＨＣｌ－０．２ｍｏｌ·Ｌ￣（－１）ＮＨ＿（４）Ｃｌ底液中连续测定人发中铜、铅、镉、锌的微分电位溶出法。四元素峰电位分别为－０．２０Ｖ，－０．４６Ｖ，－０．６７Ｖ，一１．０２Ｖ（ＳＣＥ），峰形好，灵敏度高，干扰少，测定发样相对标准偏差≤４．３％，回收率为９７．６％～１０４．６％。并对ＨＮＯ＿３－ＨＣｌＯ＿４和ＨＮＯ＿（３）Ｈ＿（２）Ｏ＿２消化发样进行了比较。     

显色试剂6—硝基—苯并噻唑重氮氨基偶氮苯的合成及与镉的显色反应

合成了新的显色试剂６－硝基－苯并噻唑重氮氨基偶氮苯，并研究了在乳化剂ＯＰ存在下马镉的显色反应。镉与试剂于ｐＨ ９．０～１０．０的缓冲介质中形成稳定的红色络合物，表观摩尔吸光系数 ε５２６＝２． ４５ × １０５Ｌ·ｍｏｌ－１·ｃｍ－１，镉浓度在０～ ０． ５ ｍｇ／Ｌ范围内符合比尔定律。该方法灵敏度高，选择性好，并用于废水和环境水样中的微量镉的测定。     

吸附溶出伏安法测定水中痕量镉

报道了测定痕量镉的一种新方法．在０．０１ｍｏｌ／ＬＨＡｃ－０．０１ｍｏｌ／ＬＮａＡｃ－１．２×１０－５ｍｏｌ／Ｌ乙醛酸缩氨基硫脲（ＧＡＴＳＣ）体系中，Ｃｄ－ＧＡＴＳＣ产生一灵敏的吸附还原波，波的峰电位是－０．４３Ｖ（ｖｓ·ＳＣＥ），峰电流与镉的浓度在１．０×１０－８～８．０×１０－７ｍｏｌ／Ｌ范围内成直线关系．此法用于测定水中痕量镉，结果令人满意。     

4,4‘—二偶氮苯重氮氨基偶氮苯分光光度法测定水和废水中的痕量汞（Ⅱ）

报道了分光光度测定汞的一种新方法。在ＰＨ９．５的ＮＨ３·ＮＨ４Ｃｌ介质和ＴｒｉｔｏｎＸ－１００存在下，４，４‘－二偶氮苯竽氮氨基偶氮苯（ＢＢＤＡＢ）与汞（Ⅱ）迅速形成橙红色配合物，并且至少稳定４８ｈ。在实验条件下，配合物的最大吸收波长为５１５ｎｍ，摩尔吸光系数ε＝１．８×１０＾５Ｌ·ｍｏｌ＾－１·ｃｍ＾－１，Ｈｇ（Ⅱ）在０￣１２ｍｇ／２５Ｌ范围内遵守比耳定律。体系具有较强的抗干扰能力， 有镉（Ⅱ）     

L－色氨酸－H_2O_2－ClO~－－CTAB流动注射化学发光反应的研究

本文采用反相流动注射法研究了在阳离子表面活性剂ＣＴＡＢ存在下，Ｌ－色氨酸－Ｈ２Ｏ２－ＣｌＯ－体系的化学发光行为，对影响化学发光强度的诸因素和表面活性剂的增强作用进行了试验和探讨，建立了化学发光测定Ｌ－色氨酸的新方法。线性范围１．０×１０－８～８．０×１０－６ｍｏｌ·Ｌ－１，检测限为４．０×１０－９ｍｏｌ·Ｌ－１（Ｓ／Ｎ＝２）。对合成试样中三种浓度的Ｌ－色氨酸测定的回收率在９７％～１０６％之间，相对标准偏差小于４％。     

镉（II）—β—巯基丙酸配合物极谱吸附波研究

在ｐＨ５．１的ＨＣｌ－六次甲基四胺缓冲溶液中，Ｃｄ（Ⅱ）－β－巯基丙酸配合物产生－灵敏的极谱吸附波。峰电流在－０。６７Ｖ（ｖｓ．ＳＣＥ）左右，峰高与镉浓度在１．８×１０＾－９￣３．６×１０＾－６ｍｏｌ／Ｌ范围内呈线性关系。检出限为９×１０＾－１０ｍｏｌ／Ｌ。研究了极谱波的性质和电极过程机理。本法用于食品中痕量镉的测定，结果满意。     

含有吸附络合物溶液的倒数示波计时电位法的应用

Ｐｂ（Ⅱ）在０．２％乙二胺－５×１０＾－３ｍｏｌ·Ｌ＾－１ＨＯｘ－０．３ｍｏｌ·Ｌ＾－１ＫＯＨ溶液中，有良好的全数示波图，其峰电位Ｅｐ＝－１．０５（ｖｓ．ＳＣＥ），峰高与Ｐｂ＾２＋溶度在４．０×１０＾－７～２．０×１０＾－５ｍｏｌ·Ｌ＾－１内成正比，检测下限可达２．０×１０＾－７ｍｏｌ·Ｌ＾－１。本实验采用倒数示波计时电位法对铝合金“Ａ”中铅进行了测定，并直接通过示波图，对络合物的吸附属于性进行了     

托美汀的吸附伏安法研究

在０．２ｍｏｌ／Ｌ ＮＨ３－ＮＨ４Ｃｌ底液中，托美汀在悬汞电极上有一灵敏的还原峰。峰电位为Ｅｐｃ＝－１．４８Ｖ，该峰具有明显的吸附性，峰电流ｉｐｃ与ＴＯＬ浓度在４．０×１０＾－９－７．０×１０＾－７ｍｏｌ／Ｌ范围内呈线性关系；检出限为５．０×１０＾－１０ｍｏｌ／ｌ，用该法测定了片剂ＴＯＬ的含量，结果良好。     

三乙醇胺活化钴（Ⅱ）催化过硼酸钠氧化荔枝红色素褪色光度法测定痕量钴

基于三乙醇胺活化钴（Ⅱ）催化过硼酸钠氧化荔枝红色素的褪色反应，提出测定痕量钻的高灵敏的催化光度法。其摩尔吸光系数ε５００＝１．８×１０７Ｌ·ｍｏｌ－１·ｃｍ－１；线性范围为０～０．４μｇ／Ｌ；工作曲线的回归方程为；相关系数ｒ＝０．９９９８；检测限１．０×１０－１３ｇ／ｍＬ。该褪色反应的表观活化能 Ｅ＝４２．１２ ｋＪ·ｍｏｌ－１，速率常数 ｋ＝１，６×１０－３·ｓ－１。此法用于血清、尿液等样品中钻的测定，结果满意。     

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.     

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%).     

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.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Synthesis and antioxidative/anti-inflammatory activity of novel fullerene–polyamine conjugates

(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C₆₀, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine.     

Copper-catalyzed multicomponent reactions of 2-iodoanilines,benzylamines, and elemental sulfur toward 2-arylbenzothiazoles

A relatively cheap copper salt-catalyzed, three-component approach providing 2-arylbenzothiazoles in good to excellent yields from readily available 2-iodoanilines, benzylamines, and sulfur powder is reported. This methodology allows preparation of various classes of 2-arylbenzothiazoles and provides a general, reliable approach.