ICP—AES测定钯—钡合金中常量钡

本文采用ＩＣＰ－ＡＥＳ法测定钯－钡合金中常量钡。考察了其体及无机酸的存在对钡发射线强度的影响，采用标准曲线法对含量分别为０．５９％和２６．０４％的两个试样进行了测定，结果满意。     

PAR光度法测定铜合金中常量铅

本文探讨了PAR光度法测定铜合金中常量铅的条件。在pH9.5—10.5的氨性介质中,PAR与铅离子形成稳定的有色络合物,其最大吸收位于520n m处,摩尔吸光度数3.25×10~4,铅含量在0—250μg/50mL服从比耳定律。采用酒石酸钾钠、氟化铵和丙酮氰醇     

紫外分光光度法直接测定常量硫酸根

提出了紫外分光光度法直接测定常量硫酸根。将脱硫石膏样品以盐酸溶解并使其中的硫酸根沉淀为硫酸钡,通过磷酸钠置换使硫酸根全部溶出,在紫外波段193,210nm处分别测定吸光度。硫酸根的线性范围为0.002~0.01mol·L-1,方法的检出限(3s/k)为3.2×10-4 mol·L-1。方法用于脱硫石膏样品的分析,测定结果与硫酸钡重量法测定值相符,测定结果的相对标准偏差(n=5)在0.18%~0.23%之间。     

新生儿头发微量及常量元素测定

采用ＪＹ－７０合并型等离子体光谱仪测定了１０４名健康足月新生儿头发中１４种微量元素和２种常量元素含量。结果表明，新生儿发生中Ｆｅ，Ｃｏ，Ｎｉ，Ｍｎ，Ｃｒ，Ｍｏ，Ｓｒ，Ｖ，Ｃａ和Ｍｇ等元素的含量水平较高；新生儿发Ｆｅ男性显著高于女性，发Ｍｇ则女性高于男性，发Ｓｒ女性高于男性，其它各元素性别间无差异或差异不显著。     

败酱草中常量和微量元素的形态分析

按照传统煎煮法对败酱草中Ca、Mg、Fe、Cu、Zn、Al、P、B、Mn和Sr 10种元素进行提取;用0.45μm微孔滤膜分离提取液中的可溶态与悬浮态;LSA-10大孔吸附树脂柱分离可溶态中的有机态与无机态;并采用正辛醇/水分配体系,在模拟人体胃肠环境条件下,将水煎液中这10种元素分离为醇溶态和水溶态;用电感耦合等离子体原子发射光谱法(ICP-AES)对各形态中的10种元素进行测定。结果表明,败酱草中10种元素的总提取率在17.2%～84.2%,悬浮态的颗粒吸附率在2.74%～71.6%,加标回收率在95.0%～105.9%,相对标准偏差(RSD)≤2.4%。     

ICP-AES法测定硼硅酸盐玻璃中的常量及微量元素

应用电感耦合等离子体原子发射光谱(ICP-AES)法,对硼硅酸盐玻璃中的常量元素Si、Ca、Al、B及微量元素Fe、Ti、Mg进行测定。在优化的工作条件下,各元素的检出限:SiO20.026μg/mL,Ca0.0002μg/mL,Al0.028μg/mL,B0.005μg/mL,Mg0.0002μg/mL,Fe0.006μg/mL,Ti0.005μg/mL。样品测定结果的相对标准偏差(n=6)在0.02%~1.47%之间,加入标准溶液的回收率为93.0%~103.2%。采用该方法对硼硅酸盐玻璃标准样品进行测定,测定值与标准值一致。     

碘量法测定复杂含硒物料中常量硒

用碘量法测定复杂含硒物料中常量硒并对测定条件做试验。试样经硝酸及硫酸溶解、蒸发至冒烟后,盐类溶于盐酸中。在酒石酸存在下加盐酸羟胺,于70℃保温1h,放置1.5h使硒还原为单质硒并陈化。过滤,将单质硒溶于盐酸中,溶解温度为90℃,溶解时间为5min,滴定时溶液酸度宜在0.2~0.5mol·L-1(盐酸介质)。滴定时采用分步滴加碘化钾溶液,随即用硫代硫酸钠标准溶液滴定至淀粉指示剂所显蓝色消失,至再次加入碘化钾无蓝色出现为终点。按所耗硫代硫酸钠标准溶液的体积计算试样的含硒量。     

二级反应速率常数与活化能计算问题的讨论

In this paper, we discussed several problems on calculation of reaction rate constant in physical chemistry reference books. When calculating the rate constant k of the second-order reaction, we should make the half-life formula consistent with the reaction stoichiometric equation. And when calculating the activation energy with Arrhenius formula for ideal gas-phase reaction, attention should be paid to identifying the difference between the reaction rate constant k_c and k_p, as well as the difference between corresponding activation energy E_ac and E_ap. It is beneficial for students to have a correct understanding in calculation.     

多个时间常数线性体系恒电量响应的频谱分析

从线性条件出发,利用拉普拉斯变换及其逆运算推导多个时间常数体系在恒电量激励条件下线性响应暂态方程,并推导出恒电量激励下Rs(C₁(R₁(C₂(R₂(C₃R₃)))))电路模型的极化电位响应式. 通过线性响应方程的理论验证以及与实际腐蚀体系的EIS进行对比,结果表明：对恒电量瞬态响应进行频谱分析,可以促进恒电量测量结果与EIS进行更加细致的对比验证. 对含有多时间常数的电极过程,利用阻抗拟合软件进行局部拟合,可以确定初始值的设置,以避免时域的曲线拟合时出现多种结果的局面,大大地提高了恒电量瞬态响应数据解析的准确性.     

Synthesis of four stereoisomers of the higher dipteran juvenile hormone III bisepoxide

The 6S,7S,10R-, 6S,7S,10S-, 6R,7R,10S-, and 6R,7R,10R-stereoisomers of the juvenile hormone III bisepoxide from higher Dipteran insects have been synthesised in high stereoisomeric purity. The route involves Sharpless epoxidation of geraniol to enantiomeric epoxyalcohols, which are each elaborated via separable diastereomeric bromohydrins.     

Synthesis of four enantiomerically pure 4-(4-carbamoyl-1,2,3-triazol-1-yl)-2,3-dihydroxy-1-methoxybutylphosphonic acids

CuCl-catalysed cycloaddition of methyl propiolate to O,O-diisopropyl (1S,2R,3S)- and (1R,2R,3S)-, or O,O-dibenzyl (1S,2R,3S)-, (1R,2R,3S)-, (1S,2R,3R)- and (1R,2R,3R)-4-azido-1,2,3-trihydroxy-2,3-O-isopropylidenebutylphosphonates followed by methylation of HO–C-1, ammonolysis of methoxycarbonyl groups and hydrolysis of isopropylidene acetals led to diisopropyl (1S,2R,3S)- and (1R,2R,3S)-4-(4-carbamoyl-1,2,3-triazol-1-yl)-2,3-dihydroxy-1-methoxybutylphosphonates or, after hydrogenolytic removal of benzyl groups, to (1S,2R,3S)-, (1R,2R,3S)-, (1S,2R,3R)- and (1R,2R,3R)-4-(4-carbamoyl-1,2,3-triazol-1-yl)-2,3-dihydroxy-1-methoxybutylphosphonic acids.     

Enantioselektive Katalyse VII. Komplexe von (P(R,S),3R,4R,P′(R,S))-3,4-Bis(phenylphosphino)pyrrolidinen. Die Darstellung optisch reiner 1,2-Bisphosphanliganden mit vier Stereozentren, die zusätzliche funktionnelle Gruppen enthalten

Diastereomeric mixtures of the palladium, the platinum, and the rhodium complexes were prepared from [P(R,S),3R,4R,P′(R,S)]-3,4-bis(phenylphosphino)pyrrolidine (1a). The phosphorus atoms in bis[(P(R,S),3R,4R,P′(R,S))-1-(t-butoxycarbonyl)-3,4-bis(phenylphosphino)pyrrolidine-P,P′]dihalogenopalladium (2) can be alkylated stereoselectively with iodomethane. The P---H bonds in 2 open epoxides, and add to Michael systems, to give new ligands, which can be split off from the palladium with cyanide. The three isomerically pure [(PR,3R,4R,P′R)(PS,3R,4R,P′S)(PR,3R,4R,P′S)]-1-(t-butoxycarbonyl)-3,4- bis[(2-cyanoethyl)phenylphosphino]pyrrolidines were prepared via the neutral diiodopalladium complexes. [(PS,3R,4R,P′S)1-(t-butoxycarbonyl)-3,4-bis[(2-cyanoethyl)phenylphosphino]pyrrolidine-P,P′]diiodopalladium(II) (14-1) was characterised by X-ray crystallography.     

Asymmetric silyl nitronate cycloadditions with bornane-10,2-sultam derivatives

Asymmetric silyl nitronate cycloadditions with N-acryloyl (2R)-bornane-10,2-sultam, N-acryloyl (2S)-bornane-10,2-sultam, and N-methacryloyl (2R)-bornane-10,2-sultam have been studied. The asymmetric silyl nitronate cycloaddidon/elimination methodology provides a general route for the asymmetric synthesis of 2-isoxazolines.     

Two new megastigmane O-glucopyranosides from the leaves of Broussonetia papyrifera

Two new megastigmane O-glucopyranosides,named (2R,3R,5R,6S,9R)-3-hydroxy-5,6-epoxy-β-ionol-2-O-β-D-glucopyrano- side(1) and (2R,3R,5R,6S,9R)-3-hydroxyl-5,6-epoxy-acety-β-ionol-2-O-β-D-glucopyranoside(2) together with six known mega- stigmanes,were isolated from the leaves of Broussonetia papyrifera (Linn.) Vent.Their structures were established by chemical methods and spectroscopic techniques including 2D NMR.     

Polyhydroxylated pyrrolizidines. Part 3: A new and short enantiospecific synthesis of (+)-hyacinthacine A2

(1R,2R,3R,7aR)-1,2-Dihydroxy-3-hydroxymethylpyrrolizidine (+)-Hyacinthacine A₂ 1 has been synthesized by Wittig's methodology using [(2′S,3′R,4′R,5′R)-3′,4′-dibenzyloxy-N-tert-butyloxycarbonyl-5′-tert-butyldiphenylsilyloxymethylpyrrolidin-2′-yl]carbaldehyde 3, prepared from a partially protected DMDP 2, and the appropriated ylide, followed by cyclization by an internal reductive amination process of the resulting unsaturated aldehyde 4 and total deprotection.     

Extraordinary chiral discrimination in inclusion gas chromatography. Thermodynamics of enantioselectivity between a racemic perfluorodiether and a modified γ-cyclodextrin

The enantiomers of the perfluorodiether “compound B” [2-(fluoromethoxy)-3-methoxy-1,1,1,3,3-pentafluoropropane], a decomposition product of the inhalational anesthetic sevoflurane [2-(fluoromethoxy)-1,1,1,3,3,3-hexafluoropropane], were separated by gas chromatography on octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-γ-cyclodextrin (Lipodex E), dissolved in polysiloxane PS 255 (30% w/w), with an unexpectedly high separation factor of =10.6 at 26 °C. Using the concept of the retention increment R′, non-enantioselective and enantioselective contributions to retention were separated and thus reliable thermodynamic parameters of enantioselectivity, i.e. −Δ_S,R(ΔG)=5.7 (0.05) kJ/mol at 303 K, −Δ_S,R(ΔH)=20.1 (0.64) kJ/mol, Δ_S,R(ΔS)=−47.4 (2.0) J/K mol and T_isoenant=424 (30) K or 150 °C, were determined by temperature-dependent measurements. The enantiomeric bias represents the largest values ever measured in enantioselective gas chromatography. An equation is presented which allows calculation of the non-enantioselective contributions to retention from measurements at two arbitrary concentrations of Lipodex E in polysiloxane. Surprisingly, the enantioselectivity is greatly reduced when employing the β-cyclodextrin analogue and breaks down completely with the -cyclodextrin analogue of Lipodex E.     

Preparation of both enantiomers of malic and citramalic acid and other hydroxysuccinic acid derivatives by stereospecific hydrations of cis or trans 2-butene-1,4-dioic acids with resting cells of Clostridium formicoaceticum

(R)-Malic, (S)-malic, (R)citramalic, (S)-citramalic, (2R,3S)-2-hydroxy-3-methyl-succinic and (2R,3S)-2,3-dimethyl-2-hydroxysuccinic acid were prepared on scales up to 25 mmol by stereospecific addition of water to different 2-butene-1,4-dioic acid derivatives catalyzed by resting cells of Clostridium formicoaceticum (Scheme 1). The (3R)-monodeuterio (R)- and (S)-malic acid as well as (R)- and (S)-citramalic acid were prepared using freeze-dried cells in ²H₂O-buffer. The stereochemical purity of the products was in most cases ≥ 99%.