钴-锌试剂络合吸附伏安法测定中草药中钴

研究了测定痕量钴的一种灵敏的吸附伏安法 ,利用钴和锌试剂络合物在悬汞电极上的吸附性 ,有效地提高了分析的灵敏度。在 0 .0 0 5mol·L-1NH3 和 0 .0 6mol·L-1NH4Cl及 2 .5× 1 0 -6mol·L-1锌试剂底液条件下 ,该体系 1 .5 ,2 .5阶微分吸附伏安法测定钴的线性范围为 1× 1 0 -10 ～ 1× 1 0 -7mol·L-1,用 2 .5阶微分吸附伏安法 ,富集 3min的检出限为 5× 1 0 -11mol·L-1。用此法直接测定了中草药中痕量钴     

尿素与Keggin结构磷钼酸电荷转移盐的合成与表征

在水中合成了两种新的有机 金属氧酸盐电荷转移配合物H3 PMo12 O4 0 ·4.5CO(NH2 ) 2 ·2 .5H2 O和H3 PMo12O4 0 ·12CO (NH2 ) 2 ,用IR、UV、TG、XRD及元素分析对其进行了表征。结果表明两种化合物中均存在[(H2 N) 2 COH]+ ,阴离子保持Keggin结构 ,但Keggin结构由于尿素的有机给体作用发生了不同程度的畸变。H3 PMo12 O4 0 ·4.5CO(NH2 ) 2 ·2 .5H2 O在固态 ,H3 PMo12 O4 0 ·12CO(NH2 ) 2 的水溶液具有光致变色效应     

阻抑-褪色光度法测定痕量硅

基于NH3 NH4 Cl缓冲溶液介质中 ,Si 对H2 O2 氧化十六烷基三甲基溴化铵 姜黄素离子缔合物的褪色反应的抑制作用 ,提出了测定痕量硅新的高灵敏的褪色光度法。该方法的表观摩尔吸光系数ε50 0=5 .70× 10 5L·mol-1·cm-1;线性范围为 0 .4～ 3.6 μg/L ;线性回归方程ΔA =2 .2 3× 10 -4 + 0 .0 2 0 17CSi (μg/L) ;相关系数r =0 .9999;测定下限为 2 0× 10 -8g/L。本法用于人发样和水样中痕量硅的测定 ,结果满意。     

磷钼杂多酸光度法测定吲哚乙酸

研究了吲哚乙酸与磷钼杂多酸在浓度为 0 .0 3 mol/L的硫酸介质中发生氧化还原反应 ,形成的还原产物 (钼蓝 )在 NH3-NH4Cl缓冲溶液 (p H8.4)中最大吸收波长为 314 nm,表观摩尔吸光系数 ε值为 3.5 4× 10 4L· mol-1·cm-1 ,吲哚乙酸含量在 5 .0× 10 -7～ 5 .0× 10 -5 mol/L范围内符合比尔定律 ,检出限为 1.0× 10 -7mol/L,对 2 .0 0× 10 -5 mol/L吲哚乙酸测定 10次的相对标准偏差为 6 .42 % ,加标回收率为 94.2 %～ 10 0 .1%     

2002年全国高中学生化学竞赛理论试题答案

第1题1－1(NH4)3H4PMo12O42·H2O＋26NaOH＝12Na2MoO4＋Na2HPO4＋3NH3＋17H2ONH3＋HCI＝NH4 Cl计量关系 P2O5－(NH4)3H4PMo12O42·H2O－NaOH1－2－46P2O5的摩尔质量:142g·mol-1P2O5%:(1．026mol·dm－3×0．04000dm-3－0．1022mol·dm－30．01520dm-3×142g·mol-1(46×0．385g)＝0．317＝31．7%(计量关系正确得3分,计算合理结果错扣1分,有效数字错扣0．5分)     

盐酸羟胺存在下极谱动力波法测定阿托品

研究了NH2 OH·HCl存在下测定阿托品的极谱动力波法。在 0 .1mol/LLiCl 4.4× 1 0 - 3 mol/LNH2 OH·HCl支持电解质溶液中 ,阿托品于 - 1 .90V(vs.SCE)处产生一个极谱动力波 ,其二阶导数峰电流与阿托品在 6.0× 1 0 - 5～ 4.0×1 0 - 4 mol/L浓度范围内呈线性关系 (r=0 .9992 ,n =5 )。与无NH2 OH·HCl存在时相应还原波相比 ,该动力波电流可提高分析灵敏度一个数量级。讨论了该动力波的产生机理     

黄芩甙的线性扫描伏安法测定研究

研究了黄芩甙在多壁碳纳米管修饰电极上的伏安行为。结果表明 ,该修饰电极对黄芩甙产生较强的吸附催化作用 ,催化电流与黄芩甙浓度在 1 .0× 1 0 - 7～ 6.0×1 0 - 5mol·L- 1范围内呈线性关系。利用本法测定了中药黄芩中的黄芩甙的含量 ,效果良好     

环境水中总铁的测定

在pH 8 5 ,0 0 4mol/L的NH3·H2 O NH4 Cl底液中,铁-甲基百里香酚蓝络合剂在NaNO2存在下,于-1 1 0V (vs.SCE)产生一尖锐、灵敏的二次导数极谱波,峰电流与铁离子浓度在3 0×1 0 - 8～5 0×1 0 - 6 mol/L范围内呈线性关系,检出限为1 0×1 0 - 8mol/L。研究了该波的性质,证明该波为催化吸附波。铁(Ⅱ)与络合剂的组成比为1∶1。方法用于环境水和矿泉水中痕量总铁的测定,结果满意     

催化动力学光度法测定井水中痕量锰

研究了在 NH3· H2 O- NH4 Cl介质中锰催化过氧化氢氧化苋菜红的褪色反应及其动力学条件 ,测定了反应级数和表观活化能 ,建立了测定痕量锰的新方法。该方法的检出限为 2 .7× 1 0 -4 μg/m L Mn,线性范围为 0～ 2 .4μg/2 5m LMn。用于测定井水中痕量 Mn,与原子吸收法的测定结果一致。     

铍试剂Ⅲ/钙色素双偶氮染料-示波计时电位法快速测定天然水中不同形态铝

采用铍试剂Ⅲ (简称BER)和钙色素 (简称CAL)双偶氮染料 示波计时电位法快速测定天然水中不同形态铝。实验条件和结果如下 :在pH 5 .0NH4Ac HAc缓冲溶液中 ,BER在dE dt E示波图上出现一个切口 ,Ep1 =-0 .3 5V。加入铝后出现一新切口 ,Ep2 =-0 .70V ,该切口深度与加入铝量在 1 .0× 1 0 - 6 ～ 2 .0× 1 0 - 5mol L浓度范围内呈线性关系 ;检出限为 5 .0× 1 0 - 7mol L ;在 5 .0× 1 0 - 6 mol LAl时相对标准偏差为 5 5 % (n=1 0 )。在pH 8.0NH4Ac NH3·H2 O缓冲溶液中 ,CAL在示波图上出现一个切口 ,EP′1 =-0 .60V。加入铝后出现一新切口 ,EP′2 =-0 .75V ,该切口深度与加入铝量在 1 .0×1 0 - 6 ～ 1 .0× 1 0 - 5mol L浓度范围内呈线性关系 ,检出限为 5 .0× 1 0 - 7mol L ;在 2 .0× 1 0 - 6 mol LAl时 ,相对标准偏差为 5 .5 % (n =1 0 )。分别采用两种试剂在弱酸性和弱碱性条件下测定了天然水样中的铝浓度 ,发现在弱酸性下测定的是无机单核铝 ,而在弱碱性下则是总单核铝 ,据此可以实现对 5种铝形态的区分。测定了实际天然水样 ,与Driscoll方法进行了对照 ,结果基本一致     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

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.