新型显色剂3,3,5,5''''-四甲基联苯胺分光光度法测定余氯的研究

本文报道了采用新型氧化还原剂3,3’,5,5’-四甲基联苯胺(TMB)测定水中总余氯的分光光度法,并对其灵敏度、稳定性、准确性作了较为详细的研究,探讨了分析条件,提出了分析方法。在pH≤2时,最大吸收峰为450 nm,表观摩尔吸光系数为6.89×10~4L·mol~(-1)·cm~(-1),可测范围为0.01～2.5 mg/L。与目前使用的传统显色剂邻联甲苯胺(DMB)相比较,具有灵敏度高,显色稳定,重现性好及使用安全等优点。     

金(Ⅲ)与 3,3’,5,5’-四甲基联苯胺显色反应的研究和应用于微量金的测定

本文研究了An(Ⅲ)与 3,3′,5.5′-四甲基联苯胺(TMB)的显色反应,在0.02mol/L盐酸介质中,TMB于波长450nm处有最大吸收,摩尔吸光系数为1.03×10~5L·mol~(-1).cm~(-1).25ml溶液中0～40μg金(Ⅲ)符合比尔定律,本方法已用于粗铜中微量金的测定.     

食品中残留过氧化氢的测定

利用猪血红蛋白(pHb)的催化特性,以3,3’,5,5’-四甲基联苯胺(TMB)为底物,建立了一种催化光度终止法测定食品中残留过氧化氢(H2O2)的方法。实验考察了终止剂的类型和浓度、反应时间、pH、温度、TMB浓度对H2O2检测的影响。在选定的反应条件下,体系吸光值与H2O2浓度在1.46×10-6～2.91×10-5mol/L范围内呈良好的线性关系,线性相关系数为0.9958,方法对H2O2的检出限为5×10-7mol/L,测定标准偏差为4.9%,样品的加标回收率为92.9%～103%,利用该方法进行了实际样品中的H2O2分析,结果与国标法无显著性差异。     

以3,3′,5,5′-四甲基联苯胺为底物的伏安酶联免疫分析体系研究

对 3 ,3′,5 ,5′ 四甲基联苯胺 (TMB) H2 O2 辣根过氧化物酶 (HRP)伏安酶联免疫分析体系进行了研究。HRP催化H2 O2 氧化TMB ,其氧化产物在汞电极上可以发生还原反应 ,在B R缓冲溶液中 ,-0 .76V(vs.SCE)处产生较为灵敏的伏安波。将此伏安波应用于测定HRP和HRP的标记物。测定HRP的线性范围为 6.0×1 0 - 1 1 ～ 5 .0× 1 0 - 9g mL ,检测限为 5 .0× 1 0 - 1 1 g mL。对该体系酶催化反应机理及产物的电极还原过程进行了探讨     

碘酸根与3,3‘,5,5’—四甲基联苯胺的显色反应研究及其分析应用

研究了碘酸根与 3,3′,5 ,5′-四甲基联苯胺 (TMB)的显色反应 ,建立了测定微量碘的分光光度法。在盐酸介质中 ,碘酸根能定量氧化 TMB生成黄色的TMB亚胺盐 ,其最大吸收波长为 45 0 nm,表观摩尔吸光系数为 2 .13× 10 5 L·mo1-1·cm-1 ,碘的质量浓度在 0～ 0 .7mg/ L 范围内符合比尔定律 ,该法已应用于加碘酸钾食盐中碘含量的测定     

水及土壤浸出液中 NO_3~--N 和 NO_2~--N 的流动注射分光光度同时测定

本文提出采用流动注射技术,以分光光度计为检测器,同时测定水及土壤浸出液中NO_3~-—N和NO_2~-—N的方法。以非致癌性化合物α-萘胺-7-磺酸和磺胺为显色剂,在520nm下比色。流路中装有镀镉锌粒还原柱,把NO_3~--N还原为NO_2~--N。NO_2~--N的检出限是0.005mg/l,NO_3~--N是0.020mg/l。在含量为1mg/l时NO_2~--N的变异系数是1％;在含量为3mg/l时NO_3~--N的变异系数是0.5％。由于引入双通道交替进样旋转定容采样阀,可以交替地对同一样品进行两项测定。分析速度为60样/小时双项测定,即120次/小时。     

2-[2'-(6'-甲氧基-苯并噻唑)偶氮]-5-二甲氨基苯甲酸的合成及其与Cu(Ⅱ)显色反应研究

报道了新试剂2-[2’-(6’-甲氧基-苯并噻唑)偶氮]-5-二甲氨基苯甲酸(简称MOBTAB)并研究了其在乙醇介质中与Cu(Ⅱ)的显色反应,试验表明,在pH2.0～4.5时,Cu(Ⅱ)与MOBTAB形成1:1的蓝色络合物.其最大吸收波长为670nm,表观摩尔吸光系数为6.55×10~4,Cu(Ⅱ)浓度在0～0.76μg·ml~(-1)范围内符合比耳定律.本法操作简便,可直接测定铸铝及纯铝中微量铜,结果满意.     

5′-硝基水杨基荧光酮与Cr(Ⅲ)显色反应的研究及其应用

研究了新显色剂5’-硝基水杨基荧光酮在溴化十六烷基三甲铵存在下与Cr(Ⅲ)的显色反应.在磷酸盐缓冲介质中(pH5.7～6.2),经沸水浴加热后.Cr(Ⅲ)与5’-硝基水杨基荧光酮形成组成比为1:2的紫色配合物.其吸收峰波长λ_(max)=590nm,对比度△λ=67nm,表观摩尔吸光系数为1.72×10~5,桑德尔灵敏度为3.0×10~(-4)μg·cm~(-2).Cr(Ⅲ)浓度为0～1.8μg/10ml时服从比耳定律.将Cr(Ⅲ)氧化为Cr(Ⅵ).采用阴离子交换树脂柱离干扰离子,方法用于水样中总铬和Cr(Ⅵ)的测定.Cr(Ⅲ)含量由差减求得.结果与二苯卡巴肼法一致.     

1’-苯基-3’-甲基-5’-氧代吡唑-4’-基乙醛酸希土配合物的合成及性质研究

本文采用电导、pH滴定法研究了乙醇-水溶液中希土与1′-苯基-3′-甲基-5′-氧代吡唑-4′-基乙醛酸(简称H_2A)的配位反应.合成了15种新的希土固态配合物.通过元素分析、化学分析、水份分析确定了配合物的化学组成为RE(HA)_3·nH_2O(RE=Ce、Pr、Sm、Tm、Lu、n=1;RE=La、Nd、Eu、Gd、Tb、Dy、Ho、Er、Yb、Y,n=1-2).并对配合物的红外光谱、核磁共振谱、热稳定性、紫外光谱、溶解性及摩尔电导进行了测定.     

2’-脱氧胞苷-5’-磷酸羟基加合物的分子结构与电子结构

使用密度泛函理论(DFT)的B3LYP/DZP++研究了羟基自由基与2’-脱氧胞苷-5’-磷酸(dCMP)的胞嘧啶环加成产物的分子结构与电子结构. 结果表明, dCMP胞嘧啶环中各C原子上的单羟基加合物的相对稳定性顺序为C5>C6>>C4≥C2. 加合物的稳定性、自旋密度、静电势以及dCMP的电子密度、静电势、电荷分布分析表明, dCMP遭遇多个羟基自由基攻击时, 第一个羟基自由基加在dCMP的C5上, 而C6则成为第二个羟基自由基的进攻目标. 反应中一旦形成了C2-位单羟基加合物, 则极有可能在DNA复制过程中引起致命的基因突变, 也可能诱发DNA-DNA以及DNA-蛋白质的链间交联, 引起更复杂的损伤. 相反, C5、C6-位上单羟基加合物的形成对DNA的稳定性不构成直接威胁.     

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.     

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%).     

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.     

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.     

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.     

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.