Competition of monomolecular and bimolecular reactions of the alkyl radicals of artemisinin

The competition between monomolecular and bimolecular reactions of alkyl radicals of artemisinin is considered theoretically. The enthalpies of these reactions are calculated. The activation energies and rate constants of intramolecular hydrogen atom transfer, of the decyclization of the alkyl radicals of artemisinin, and of the bimolecular reactions of these radicals with C-H, S-H, and O-H bonds of biological substrates and their analogues are calculated in the framework of the parabolic model. The intramolecular hydrogen transfer reactions proceed at the highest rate. The bimolecular reactions occur somewhat less rapidly. The fastest of them are the reactions of the alkyl radicals with the thio groups of cysteine. The decyclization reactions of all artemisinin alkyl radicals are very slow.     

两种含杂环的氨基萘醌化合物的合成

以2,3-二氯-1,4-萘醌为主要原料,分别与吗啡啉和糠胺在一定条件下反应生成2种含杂环的氨基萘醌类化合物。2,3-二氯-1,4-萘醌与吗啡啉及2,3-二氯-1,4-萘醌与糠胺物质的量比均为1∶2,反应温度为60℃,溶剂为乙醇。2,3-二氯-1,4-萘醌与吗啡啉反应时间为1 h,产物2-氯-3-吗啡啉基萘-1,4-二酮(a)收率为93.5%;2,3-二氯-1,4-萘醌与糠胺反应时间为4 h,产物N~2,N~3-二(2-呋喃甲基)-1,4-二((2-呋喃甲基)亚胺)-1,4-二氢化萘-2,3-二氯化铵(d)收率为46.7%。对产物进行IR、Uv、MS和H-NMR等分析表征。     

Quantitative evaluation of the mechanism of electroreduction of benzoyl cyanides

The mechanism of reduction of benzoyl cyanide, 6, p-methoxybenzoyl cyanide, 7, and p-chlorobenzoyl cyanide, 8, has been studied in acetonitrile (6 and 7), N,N-dimethylformamide (6), and acetonitrile containing water (all three compounds). The reaction proceeds by initial reduction to form the anion radical followed by dimerization to produce an intermediate dianion, the dianion of the dicyanohydrin of benzil. The latter loses cyanide to give the anion of the monocyanohydrin of benzil, which undergoes two parallel reactions: expulsion of cyanide to give the corresponding benzil and rearrangement to the monoanion of mandelonitrile benzoate. The addition of water brings about an increase in the dimerization rate constant and an associated increase in the amount of benzil that is produced. The standard potentials for the initial reduction step have been evaluated, and their dependence on the substituent is discussed. The dimerization rate constants have also been evaluated.     

Ecological Dangers of Chemical Contamination of Urban Areas Soils: Casestudy of Tomsk

The elemental composition of soils in Western Siberia industrial center – Tomsk city is studied. The content of 28 elements in soils of the four administrative districts is determined by the instrumental neutron activation analysis method. The value of calculated total pollution index indicates a high degree of soil contamination, and dangerous levels of human health risk. The main contributors to the total pollution index value are elements: Tb, Br, Sb and Ta. The districts were ranked by the accumulation level of some elements, and it is shown that increased concentration values are confined to industrial enterprises and fuel cycle. The specificity of city districts soil cover is the increased values of relative to the city average values of several elements contents: Kirovsky district- Na and Ba, Oktyabrsky - Hf, Sc, Tb, Sm, La, Ce, Yb, Lu, and Br, Leninsky - Ca, Rb, Sr. The main sources of chromium and barium in the Tomsk city environment are analyzed.     

Mechanism of oligomerization reactions of silica

The mechanism of the oligomerization reaction of silica, the initial step of silica formation, has been studied by quantum chemical techniques. The solvent effect is included by using the COSMO model. The formation of various oligomers (from dimer to tetramer) was investigated. The calculations show that the anionic pathway is kinetically preferred over the neutral route. The first step in the anionic mechanism is the formation of the SiO-Si linkage between the reactants to form a five-coordinated silicon complex, which is an essential intermediate in the condensation reaction. The rate-limiting step is water removal leading to the oligomer product. The activation energies for dimer and trimer formation ( approximately 80 kJ/mol) are significantly higher than those of the subsequent oligermerization. The activation energies for the ring closure reaction ( approximately 100 kJ/mol) are even higher. The differences in activation energies can be related to the details in intra- and intermolecular hydrogen bonding of the oligomeric complexes.     

Quantum-chemical study of tautomers of reduced forms of anthraquinone

The quantum-chemical method B3LYP/6-311G(d,p) was used to calculate structural parameters of four conformers of 9,10-dihydroxyanthracene, two conformers of 9-hydroxyanthrone, and the corresponding anions, dianion, and radical anion. The energy of 9,10-dihydroxyanthracene in a gas phase is higher and in aqueous solution lower than the energy of 9-hydroxyanthrone. The dianion can exist exclusively in a polarizable medium.     

HPLC study of the efficiency of extraction of phenolic compounds

Summary The rate of extraction of phenolic compounds in two different solvents has been studied by liquid chromatography (HPLC) under reverse phase, gradient elution conditions. The solvents were diethyl ether and ethyl acetate. The method has been applied to two natural samples, a white wine and apple pulp.     

Thermal analysis of synthesis of wulfenite

A derivatograph was used in a thermal analysis study of the synthesis of wulfenite (lead molybdate) by the sintering of cerussite or lead oxide with molybdite. The reaction products were identified microscopically and by using a Siemens crystalloflex diffractometer. The DTA curves of mixtures of cerussite with molybdite show first the characteristic peaks of cerussite. The sharp endothermic peak at 300°C reflects the dehydration of hydrocerussite associated with cerussite. The endothermic peak at 350°C indicates the first step of cerussite decomposition, into PbO·PbCO₃, and that at 400°C indicates the second step of its decomposition, into lead oxide. The formation of wulfenite takes place at 520°C in an exothermic reaction. The medium endothermic peaks at 880 and 955°C reflect the melting and volatilization of unreacted lead and molybdenum oxides. The DTA curve of sintering of molybdite with lead oxide reveals the formation of wulfenite at 500°C. The melting and volatilization of unreacted lead and molybdenum oxides appear in only one large and sharp endothermic peak at 980°C.The resulting wulfenite is pale-yellow in thin section, and crystallizes in the tetragonal system, in the form of square tabular crystals, with distinct (011) cleavage.     

Molecular-dynamics simulation of nanoclusters of crystal modifications of titanium dioxide

The thermodynamic and structural properties of titanium dioxide nanoclusters belonging to the two most common crystal modifications, rutile and antase, were studied by molecular-dynamics simulation. The local densities of particles in the systems, two-particle distribution functions, and electric potential profiles were calculated. The influence of the size of nanoclusters on their properties and structure was examined.     

Calculation of enthalpies of hydrogenation of hydrocarbons

Sets of hydrogen molecule equivalents have been developed which permit the calculation of hydrogenation of different types of carbon-carbon bonds from ab initio total energies (3-21G and 6-31G* basis sets, and, to a more limited extent, for MP2/6-31G* data) of reactants and products. The calculated enthalpies of hydrogenation are in good agreement with experiment for unstrained molecules, with average errors on the order of 2 kcal/mol. The 6-31G* equivalents allow the enthalpies for strained molecules to be calculated accurately, but the 3-21G equivalents do not. The equivalents for both basis sets have been tested by calculating the enthalpies of hydrogenation of carbon-carbon bonds in nitrogen- and oxygen-containing organic molecules, free radicals, and classical carbocations. The results are in good agreement with experiment in most cases.     

Comparative study of the structure of products of plasma modification of globular and fibrillar proteins

The molecular-mass distribution and amino acid composition of globular (albumin, lysozyme) and fibrillar (collagen) proteins subjected to treatment in electron-beam plasmas of various gases were experimentally studied. The samples were treated in the forms of powders and freeze-dried thin films. The electron-beam plasma treatment of powdered collagen resulted in the formation of low-molecular-mass compounds only. The modification of albumin and lysozyme was accompanied by polymerization of the proteins against the background of insignificant degradation. The plasma-stimulated processes occurred in the surface layer of powder particles, whereas the bulk of the sample remained intact. The degradation and polymerization processes in thin films of globular proteins occurred throughout the entire volume of the sample.     

Investigation of the kinetics of the nitration of thiophene derivatives

The kinetics of the nitration of thiophene derivatives with nitric acid in acetic anhydride were investigated. The nitration of 2-substituted thiophenes is a second-order reaction. The rate constants and activation parameters of the reaction were calculated. The possibility of the use of the Hanmett and Yukawa-Tsuno equations for this reaction series is demonstrated. An isokinetic dependence is observed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 167–170, February, 1982.     

卷烟化学指标的因子分析

运用因子分析法对A牌号卷烟的18个化学指标进行分析,结果表明:烟丝的总糖、还原糖、总氮、总植物碱、水分、氯离子、钾离子、葡萄糖、麦芽糖、苹果酸、异戊酸、苯甲醇、茄酮、β-大马酮14个指标,及主流烟气的水分、CO、烟碱、焦油4个指标所含的信息可由8个因子来表示。该8个因子模型解释了试验数据总方差的86.7%;烟丝的致香成分、水分、糖类物质、有机酸类物质对卷烟A的质量风格具有重要影响,特别是致香成分在进行卷烟质量表征时应该重点关注。因子分析结果为卷烟的化学表征和质量控制提供了有用的参考。     

栽培草莓品种果实香气特性研究

通过对4个不同栽培草莓(Fragaria ananassa Duch．)品种果实糖和氨基酸测定及香气的GC-MS分析,结果表明：不同品种间氨基酸和糖含量不同,氨基酸含量由高到低依次为丰香、瓦尔达、哈达和全明星;哈达、丰香、全明星和瓦尔达4个品种果实分别检测出39、46、37和44种香气成分,各占总峰面积98.52％、99.15％、98.77％和95.4l％,检测成分的多少与氨基酸总量显著正相关,相关系数为0.967;哈达有5种独有的成分,丰香有9种独有的成分,全明星有3种独有的成分,瓦尔达有2种独有的成分,4个品种共有的成分有19种。     

广东省高校大学生膳食调查及营养配餐推荐

本调查报告采用问卷法了解广东主要高校大学生一周内熟食进食量及用餐情况，计算出每人每日热量和各种营养素的摄人量，采用Microsoft Excel软件进行数据处理和统计分析，并用中国营养学会制订的DRIs(膳食营养素参考摄人量)和中国居民膳食指南及平衡膳食宝塔进行比较分析，且通过微量元素检测对结果进行了验证，最后提供了为期一周的营养配餐作为膳食参考。主要调查结果如下：男女生的蛋白质、尼克酸、维生素C、维生素E、碘和男生锰的摄入量已经满足人体需要。男生铁和锰的摄入量基本满足需要。男女生的能量、脂肪、膳食纤维、维生素A、硫胺素、核黄素、钙、锌的摄人量都不足，且女生铁的摄人量同样不足。男女生一日三餐热量分配结构十分不平衡，早餐的热量摄入均偏低，膳食结构也不合理。在分析广东省大学生膳食状况的基础上，推出五套营养配餐方案供高校膳食部门和大学生参考选用。     

纯液体饱和蒸气压测定实验的改进

The measurement of saturated vapor pressure of pure liquid has been improved by designing a novel apparatus. The pure liquid vapor at phase equilibrium could be obtained, and the temperature of phase equilibrium could be accurately measured. In addition, the balance between the internal pressure and external pressure could been conveniently adjusted. The improved method is simple, rapid, easy operate, time-saving and safe.     

Determination of proteolytic hydrolysis of thyroglobulin

A method for the determination of the free thyronine- and tyrosine-like amino acids in the thyroidal protein thyroglobulin is presented. The compounds of interest are monoiodotyrosine, diiodotyrosine, thyronine, diiodothyronine, triiodothyronine and tetraiodothyronine. The extent of proteolysis was followed by high-performance liquid chromatographic monitoring of both the remaining peptides and the formation of the free thyroidal amino acids. Total hydrolysis was achieved by a combination of proteolytic enzymes. A number of enzymes were tested, such as trypsin, chymotrypsin, pronase, aminopeptidase-M, carboxypeptidase-A, carboxypeptidase-P and carboxypeptidase-Y. The best combination turned out to be pronase followed by aminopeptidase-M. The relative amounts of the enzymes, with respect to the substrate thyroglobulin, and the time of incubation were optimized to achieve total proteolysis in 4 h. The method was applied successfully to samples from a toxicological experiment with sodium bromide.     

基于壳聚糖的浊度法测定超滤膜截留率

研究了以壳聚糖为基准物、浊度法测定超滤膜截留率的方法。以氢氧化钠为沉淀剂,用浊度法分别对6种不同相对分子质量的壳聚糖浓度进行检测,探讨了壳聚糖相对分子质量与氢氧化钠浓度等因素对浊度的影响。结果表明,壳聚糖含量在25~1 000 mg/L范围内与浊度呈现良好的线性关系,线性相关系数r~2≥0.996,检出限在2.1~4.8mg/L之间,样品加标回收率为82.1%~122%。测量结果的相对标准偏差为0.75%~8.7%(n=6)。该法快速、简便,可为超滤膜研究、生产、改性及应用等提供理论指导。     

Methodology of the spectrophotometric analysis of mixtures of organic substances: Nonadditivity of light absorption

The typology of the problems being solved in the analysis of multicomponent mixtures of organic substances (pharmaceutical preparations, petroleum products, and others) is proposed. The difficulties associated with the problems of each type are discussed, and the potential of spectrophotometry without the separation of components in overcoming the difficulties is considered. The nonadditivity of light absorption due to the interaction of components is the most complicated problem. The methods for revealing deviations from additivity, the correlation of these deviations with the composition of the mixture, the effect of nonadditivity on the results of determination, and the approaches to reducing the corresponding systematic errors based on chemometric algorithms are discussed.     

Basis of Solid-Phase Grafting of Polypropylene

Abstract

The chemical modification of polymers opens new dimensions for the development and design of materials based on plastics. The chemical modification of polymers by reactions is performed by reactions in a melt, in a solution, or in a solid phase. The modification of polymers in solid phases (powder or granular material directly from the polymerization) has great advantages compared with reactions in solution or melt. The advantages are lower costs and, most important, greater creative variability. A special advantage of solid-phase modification of polypropylene (PP) is the fact that the degradation reaction is reduced.