氯球键合氮氧自由基的合成及在醇氧化中的应用

本文以氯甲基化聚苯乙烯珠体（简称氯球）为原料,和４－羟基－２．２．２．２－四甲基哌啶氮氧自由基反应,合成出氯球键合氮氧自由基。通过基对醇的氧化反应,考察了负载氮氧自由基的氧化性能。     

聚乙烯醇缩对甲酰基苯偶氮变色酸的结构与性能

研究了聚乙烯醇缩对甲酰基苯偶氮变色酸(Polyvinylalcoholcondensedpoformylphenylazochromotropicacid,称PVA·FPAC)的结构与性能。结果表明,小分子试剂甲酰基苯偶氮变色酸(FPAC)高分子化后,性能有了较大的改善;表现为不同聚合度和羟基取代度(聚乙烯醇主链上羟基被取代的程度)的高分子显色剂其性能有较显著的差异;就聚乙烯醇缩对甲酰基苯偶氮变色酸而言,同一聚合度的试剂,羟基取代度越大,溶解性越好,显色反应的灵敏度越高,但对非有机溶剂液-固萃取影响不大;对不同聚合度的试剂,聚合度高的,显色灵敏度和萃取率均有明显提高。     

抗坏血酸和亚硝酸反应的动力学研究

抗坏血酸和亚硝酸反应的动力学研究肖士民，李翠荣（华南理工大学应用化学系广州５１０６４１）关键词抗坏血酸，亚硝酸，动力学Ｎ－亚硝基胺是一种很强的致癌物质，在人胃的弱酸性环境中，可由来源于食物及防腐剂的亚硝酸盐与来源于药物的仲胺化合而成。近年来国内外都有...     

抗坏血酸作基体改进剂石墨炉原子吸收光谱法测水中铷

提出了以抗坏血酸作基体改进剂石墨炉原子吸收光谱测定水中铷的新方法.本法特征量为4.6pg Rb,检出限(3s)为 0.27μg·L~(-1)样品加标回收率为95%～110%.方法简便、快速、结果准确可靠.     

褶合光谱法测定复方苯甲酸醇溶液中的苯甲酸和水杨酸

利用褶合光谱法不经分离同时测定复方苯甲酸醇溶液中苯甲酸和水杨酸的含量，苯甲酸和水杨酸的平均回收率分别为100.15%、100.02%，测定结果的相对标准偏差分别为1.40%、0.58%。     

QUENCHING OF THE TRIPLET STATE OF CHLOROPHYLL a BY ASCORBIC ACID AND ASCORBATE IN ETHANOLIC SOLUTION

Abstract— Ascorbic acid and ascorbate in chlorophyll ethanol solution were found to be fairly efficient quenchers of the chlorophyll triplet state; comparable to the efficiency of ascorbic acid as a quencher in aqueous pyridine solution.
It has been well established that ascorbic acid quenches the triplet state of chlorophyll in aqueous pyridine solution.^(1,2) The bimolecular quenching constant, kQ , is very much less than that for O₂ or quinine.^(3,4)
Information regarding the quenching of the triplet state of chlorophyll by ascorbic acid in ethanolic solution is lacking. There has been some question as to whether ascorbic acid reduces photoexcited chloro-phyll-ethanolic solution because of its high oxidation potential, or because like the ascorbate ion, it acts only as a quencher; both ascorbic acid and ascorbate in high concentrations gave low quantum yields.⁽⁵⁾ The quenching of the triplet state by ascorbic acid and ascorbate was determined by the flash-photolytic method.     

酸增殖剂研究进展

本文综述了能有效提高化学增幅抗蚀剂体系感度的各种类型酸增殖剂及其酸增殖机理.对某些常用于光致抗蚀剂中的酸增殖剂的特性作了介绍.并对它们的应用前景、现存问题和改进方向进行了简单讨论和介绍.     

抗坏血酸在聚甲苯胺蓝膜修饰的玻碳电极上的电催化氧化及流动注射分析

在玻碳电极上用循环伏安法电聚合一层聚甲苯胺蓝膜,该膜修饰电极对抗坏血酸(VC)的氧化具有良好的电催化作用,能够降低其过电位约100mV。将该修饰电极应用于流动注射能大大提高VC的检测灵敏度,其线性范围为2.0×10-7～1.2×10-3mol·L-1,检出限为4.8×10-8mol·L-1,连续注射检测,其电流信号能够保持稳定24h。     

OXIDATION OF ASCORBIC ACID AS AN INDICATOR OF PHOTOOXIDATIVE STRESS IN THE EYE

When whole retinal pigmented epithelium (RPE) cells isolated from bovine eyes are incubated with 14C-labeled ascorbic acid and exposed to a visible laser, the ascorbic acid is oxidized to dehydro-L-ascorbic acid (DHA). The amount of ascorbic acid which is oxidized is proportional to the radiant exposure of the sample (i.e. the total amount of radiation per unit area delivered over the exposure time). Blue light is more effective than red light in driving the reaction. The amount of label appearing in the DHA fraction is increased if unlabeled DHA is present in the reaction mixture, indicating that some redox cycling of ascorbate is occurring in the RPE cells. The ascorbic acid oxidizing activity does not depend on intact cells, is not inactivated by heating the cells to 80 degrees C, and appears to reside mainly in the subcellular fraction which contains melanin pigment granules. The ascorbic acid oxidation may be caused by free radicals formed when melanin is illuminated with light. This reaction appears to be a useful method for quantifying the production of free radicals during photooxidative stress.     

THE CRYSTAL AND MOLECULAR STRUCTURE OF p-NITROPHENACETURIC ACID

Abstract

The crystal and molecular structure of p-NO₂C₆H₅CH₂CONHCH₂COOH or C₁₀ H₁₁ N₂O₅ has been determined by single crystal x-ray diffraction techniques. The compound crystallizes in the space-group P₂₁. /c with four molecules in a unit cell of dimensions: a = 11.8748(5)Å, b = 11.2732(4)Å, c = 8.8073(5)Å and β = 112.966(4)°. The structure was solved by direct methods and refined to a final value of R = 0.042. The molecule assumes a conformation similar to that found for the analogous side-chain in the penicillin G molecule and hence should be a convenient model system in studying copper catalyzed degradations of penicillin. The hydrogen bonding between the amide oxygen of one molecule to the carboxylic acid proton, 2.67(1)Å, and the amide nitrogen, 2.91(1)A, of another molecule creates a three-dimensional network identical to that found for hippuric acid.     

间接光度法测定药物中的抗坏血酸

研究了一种简便的选择性高的药物中抗坏血酸含量的测定方法。该方法基于在弱酸性介质中 ,有盐酸羟胺、碘酸存在下 ,抗坏血酸还原对氨基苯磺酸与N 1 萘乙二胺盐酸盐混合体系生成的有色物质 ,体系的最大吸收波长为 5 40nm ,工作曲线的线性范围为 0 .5～ 4 .0 μg·ml- 1。方法灵敏度高 ,选择性好 ,对药用维生素C中抗坏血酸含量进行测定 ,结果满意     

应用UHF-INDO方法对氰乙酸自由基结构的计算

本文应用UHF-INDO方法研究了氰乙酸自由基的结构.计算了氰乙酸自由基的本征值.本征向量、价电子密度、自旋密度、各向异性耦合常数、各向同性耦合常数以及总能量、键能和偶极矩:计算的各向同性耦合常数和各向异性耦合常数与实验值符合很好.     

卟啉铁与抗坏血酸均相电子转移反应的动力学和机理

采用电子吸收光谱和光谱－电化学方法研究了中位－四（邻硝基苯基）四苯并卟啉的Fe(Ⅲ）配合物与抗坏血酸在DMF溶液中的均相电子转移反应的动力学和机理。结果表明此电子转移反应来源于抗坏血酸与铁卟啉中心铁离子的轴向配位作用,并将一个电子转移至铁离子。反应速度对铁卟啉和抗坏血酸均为一级,并与抗坏血酸的离解有关。     

DIRECT SYNTHESIS AND CRYSTAL STRUCTURE OF DIIODOETHYLENDIAMINELEAD(II) DIMETHYLSULFOXIDE

Abstract

A direct method of obtaining PbEnI₂.DMSO is reported. The crystal structure of the compound was determined by X-ray techniques. PbEnI₂.DMSO is triclinic, space group P 1, C₄H₁₄I₂N₂PbS, a=10.225(3), b=10.132(3), c=6.900(2) Å; α=90.83(2), β=88.30(2), γ=106.35(4)°; V=685.6(4) ų; z=2, calculated density 2.92 gcm^?3. Neutral PbEnI₂ complexes are associated with DMSO molecules via H-bonds. The lead(II) ion is covalently linked with a chelated En molecule (Pb-N 2.46–2.48 Å) and I^? anions (Pb-I 3.087–3.343 Å). Covalently bonded atoms form an umbrella-like coordination Pb(II) polyhedron. The side containing the lone electron pair of the lead(II) ion has coordination completed by two I^? anions of neighbouring molecules with the Pb-I 3.621–3.627 Å.     

PHASE EQUILIBRIA IN THE SYSTEMS OF ACETIC AND GLYCOLIC ACID WITH WATER AND LAURETH 4

The effect of α-hydroxy group on the phase behavior in a skin lotion model system was studied by determining the phase diagrams for the two systems acetic acid / Laureth 4 / white oil / water and glycolic acid / Laureth 4 / white oil / water using visual observation by optical microscopy. The two acids when combined with surfactant and water gave an isotropic liquid solution, and a lamellar liquid crystal with different amounts of solubilization showing both acids to act as hydrotropes. The result provided essential information about the differences in the phase behavior which can attribute to the presence of a-hydroxy group in the glycolic acid. Small angle x-ray diffraction was used to determine the boundaries of the lamellar liquid crystal phases in the two systems, both acids were found to be located in the water region in the liquid crystal.     

STUDIES ON THE CHEMILUMINESCENCE OF LUMINOL IN DIMETHYLSULFOXIDE AND DIMETHYLSULFOXIDE-WATER MIXTURES*

Abstract— The absorption, fluorescence, and chemiluminescence (CL) characteristics of luminol have been studied in basic dimethylsulfoxide (DMSO) and various basic DMSO — water mixed solvents. It has been shown that the luminol dianion can be produced quantitatively in carefully deoxygenated ‘dry’ DMSO using potassium t-butyl alcoholate (BTO) as the base. A direct correlation has been found between the intensity of CL and the concentration of luminol dianion, Indicating that the dianion is the reactive species in the chemiluminescent reaction in DMSO. Increasing concentrations of water in the mixed solvents greatly reduced the CL intensity because of the decrease in luminol dianion concentration. Solvent effects on the fluorescence of 3-aminophthalic acid samples was noted and identified. Chemiluminescent spectra of luminol were run as a function of solvent composition, and compared with fluorescence spectra in the same media. The need for correcting these spectra for comparison was noted. Stopped flow kinetic studies were run in DMSO and DMSO-water mixtures. These data can be interpreted on the basis of two second-order steps and one first-order step in the reaction. The first-order step is probably last and probably arises from decomposition of a ‘peroxy’ intermediate. The rate constant for this step is k= 1·2±0·3×10^-1 sec^-1.     

土槿甲酸的分子结构及晶体结构的研究

土槿甲酸是抗真菌土槿皮酸的成分之一.晶体属四方晶系,空间群P422晶胞参数a=b=8.956Å,c=51.834Å,α=β=γ=90°,z=∑a_n=4564.土槿甲酸的粗结构模型和化学结构式通过直接法测定.     

二苯基四硫富瓦烯-十二钨杂多酸自由基盐的合成、性质和结构

用电结晶法合成了二苯基四硫富瓦烯(DBTTF)-十二钨杂多酸自由基盐，(DBTTF)₆HSiW₁₂O₄₀·2H₂O和(DBTTF)₆PW₁₂O₄₀·5H₂O，并用红外光谱、电子光谱和ESR谱进行了表征。测定了两个盐的磁化率、电导率和(DBTTF)₆HSiW₁₂O₄₀·2H₂O的单晶结构以及X-射线粉末衍射图。晶体属三斜晶系，P1空间群；晶胞参数为：a=13.774(2)?, b=14.196(2)?, c=15.628(3)?, α=104.48(1)°, β=103.97(1)°, γ=95.82(1)°, V=2828.4(8)?³, Z=1, Dc=2.789 mg/m³, R=0.0615。两种盐均为顺磁性物质，具有半导体的电传导性。     

光化学反应在分析化学中的应用研究 光激活产生碘测定食品中的抗坏血酸

本文探讨了酸性介质中于紫外光的照射下,利用光激活产生碘的光化学动力学法测定抗坏血酸的可能性。结果表明,在0.25mol/L的硫酸介质中,在过量碘化钾的存在下,抗坏血酸的含量与到达滴定终点的时间在较宽的浓度范围内呈良好的线性关系。用于蜂蜜,黄瓜、蕃茄及Vc药片等样品分析,其相对标准偏差均在1％以下,准确度令人满意。     

THE FLAVIN SENSITISED PHOTOOXIDATION OF ASCORBIC ACID: A CONTINUOUS AND FLASH PHOTOLYSIS STUDY

Abstract —The mechanism of the photooxidation of ascorbic acid by flavin mononucleotide has been studied by steady state and flash photolysis techniques. The primary reaction consists of an electron abstraction from ascorbic acid by the flavin singlet and triplet states by a diffusional process and in the latter case also by the formation of a triplet flavin-ascorbic acid complex. Under anaerobic conditions, the secondary reactions consist primarily of a radical recombination and a 'dark'chemical back reaction, leading to the reformation of unchanged flavin and ascorbic acid. In the presence of oxygen, the 'back reactions'are prevented, resulting in the efficient photooxidation of ascorbic acid.