Synthesis of hydroxyethylhydrazine by the Raschig process and comparison with synthesis by the alkylation process

The Raschig synthesis of hydroxyethylhydrazine (HEH) is studied, that is, the reaction of monochloramine on ethanolamine. The formation of HEH is monitored by UV spectrometry, and the influence of temperature and pH is studied. The primary reaction is an SN₂‐type mechanism, whereas the main secondary reaction is the oxidation of HEH by monochloramine. This reaction is also monitored by UV spectrometry, and the oxidation product is identified by GC–MS analysis, showing the formation of hydroxyethylhydrazone. The reaction mechanisms and the rate constants were determined, and the results permit establishing the main reactions occurring during HEH synthesis. These reactions were validated in a concentrated medium, with the systematic study of the influence of the molar ratio p ([HEH]₀/[NH₂Cl]₀) and the final sodium hydroxide concentration and temperature. A comparison is made with the other synthesis process already published, that is, the alkylation of hydrazine by either chloroethanol or epoxide. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 331–344, 2011     

Polystyrene fractionation by liquid chromatography and identification of the compounds by spectroscopy

Summary The fractionation of polystyrene materials including NBS polystyrene standards 705 and 706 was investigated by liquid adsorption chromatography. Identification of some of the individual components was achieved by infrared spectroscopy using solid pellets, micro internal reflectance techniques and computer-based background substraction methods. Ultraviolet spectroscopy was used as an additional means of identification. The advantages and disadvantages of these techniques are discussed.     

Synthesis of vinylindoles and vinylpyrroles by the Peterson olefination or by use of the Nysted reagent

Vinylindoles and vinylpyrroles were prepared from their corresponding aldehydes or ketones using the Peterson olefination, or by use of the Nysted reagent, a commercially available gem‐dimetallic compound. The two methods provide efficient and convenient access to these useful heterocyclic 1,3‐diene systems. J. Heterocyclic Chem., (2011).     

Structure and acid-basic properties of the surface of titanium oxides modified by phosphorus and aluminum and prepared by the alkoxo method

An alkoxo method for the preparatio of single-phase titanium oxides modified by phosphorus and aluminum is proposed and the mechanism of oxide formation is investigated. Structural studies showed that the sizes of the anatase microcrystallite grains and mesopores in the systems are characterized by a uniform distribution. The nature of the modifying agent and the conditions of synthesis influence the interatomic distances and the dimension ofc, the tetragonal unit cell constant of anatase. Published inIzvestiya Akademiii Nauk. seriya Khimicheskaya, No. 11, pp 1829–1834, November, 2000.     

Characterization of surface coatings by the scratch adhesion test and by indentation measurements

Summary Functional coating and surface modified layers can be characterized by engineering related criteria such as the ultramicrohardness test and the scratch adhesion test. The ultramicrohardness test is based on penetration depth measurements during a loading and unloading cycle. The depth sensing indentation provides a means of evaluating the elastic and plastic deformations of the tested material, from which, by calculation, the microhardness, HV, and the elasticity modulus, E, can be derived as illustrated on a number of examples of hard and soft materials and coating composites. The scratch test (REVETEST^R) and microscratch test (MST^R) has been applied to determine the adhesive and/or cohesive strength of coatings deposited on softer or tougher substrates. A Rockwell C diamond cone is used to scratch the surface of the coated or surface-modified specimen at a constant speed and under a continuously increasing load. The smallest load at which the coating is damaged, called the Critical Load, L_c, is determined by optical, electron optical, acoustic emission detection and/or by frictional force measurement, i.e. by the sudden increase of the driving force. This is illustrated on hard, brittle, and on soft coatings.     

Fluorescence Enhancement of Oxadiazole by Albumin and the Microdetermination of Albumin by Fluorospectrophotometry

A simple, rapid, and sensitive fluorometric method for determining microamount albumin selectively is presented. The fluorescence of 2,5-di(orthoamino phenyl)-1,3,4-oxadiazole is enhanced greatly by the addition of albumin. Based on this, a range of 6.8–47.6 μg/ml albumin can be detected. All other proteins have little interferences on the assay. Experimental parameters are optimized. In detection of serum albumin, the method gives values close to those of the BCG method. Scatchard analyses show that the association constant of bovine serum albumin with oxadiazole is 6.82 × 10⁴M⁻¹. Fluorescence displacement data indicate that oxadiazole binds to the bilirubin site.     

Comparison of the Activation Energies as Determined by DSC and by Conventional Methods

The results of determination of activation energies (E_A) of polymeric cable insulations obtained by conventional methods (usually based on the evaluation of changes of mechanical properties of insulations after their ageing in thermal chamber at different temperatures) have been compared with results obtained by methods employing the differential scanning calorimetry (DSC). Three DSC methods have been tested: the method according the ASTM E 698; measuring of DSC characteristics in the isothermal mode at several different temperatures; and the method based on evaluation of DSC characteristics of insulations after their thermal ageing in thermal chamber. The last method — which can be called as a modified conventional method, because instead of mechanical properties, the DSC characteristics are determined — has been found as most acceptable and giving similar values of E_A as the other conventional methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

应用超临界流体萃取分离-气相色谱-质谱分析法建立中药温郁金的指纹图谱及其系统聚类分析

收集生长于浙江省瑞安市8个产地的温郁金样品14批次,分别经清洗、冷冻干燥及碾磨粉碎,得到通过0.425mm筛孔药筛的粉末状样品14个。称取此样品各30g,分别按试验选定的最佳条件[萃取温度35℃,萃取压力15MPa,萃取时间(静态30min,动态90min)]进行超临界流体萃取分离,所得萃取物收集于甲醇5mL中,并进行气相色谱-质谱法(GC-MS)分析。色谱分离采用HP-5ms石英毛细管色谱柱和在50~220℃之间程序升温模式;质谱测定采用电子轰击离子源(EI),在质荷比(m/z)50~650内进行扫描。所得总离子流色谱图中共有50多个色谱峰,选择保留时间在40min以内的共有峰26个作为考察对象,选择保留时间为17.12min的莪术二酮为参考峰,计算共有峰的相对保留时间α和峰面积百分比S以及各样品与S3的S值的最大差值ΔS(Max)%,并建立了14个样品的指纹图谱。根据GC-MS分析所得结果并与NIST 14谱库比对,对共有峰作出鉴定。通过SPSS 16.0软件,采用系统聚类分析法对所分析的14批次温郁金样品的指纹图谱进行分类比较。应用指纹图谱对2个市售温郁金产品作了组分鉴定和产地认定。     

Hydrogen absorption and desorption by the Li-Al-N-H system

Lithium hexahydridoaluminate Li(3)AlH(6) and lithium amide LiNH(2) with 1:2 molar ratio were mechanically milled, yielding a Li-Al-N-H system. LiNH(2) destabilized Li(3)AlH(6) during the dehydrogenation process of Li(3)AlH(6), because the dehydrogenation starting temperature of the Li-Al-N-H system was lower than that of Li(3)AlH(6). Temperature-programmed desorption scans of the Li-Al-N-H system indicated that a large amount of hydrogen (6.9 wt %) can be released between 370 and 773 K. After initial H(2) desorption, the H(2) absorption and the desorption capacities of the Li-Al-N-H system with a nano-Ni catalyst exhibited 3-4 wt % at 10-0.004 MPa and 473-573 K, while the capacities of the system without the catalyst were 1-2 wt %. The remarkably increased capacity was due to the fact that the kinetics was improved by addition of the nano-Ni catalyst.     

Studying the Glass Transition by DSC and TMDSC

First, the principal features of the glass transformation process in polymers are reviewed, and then it is shown how they are manifest in conventional DSC, and the quantitative analysis of typical DSC data is discussed in terms of the Tool-Narayanaswamy-Moynihan (TNM) model. Subsequently, the way in which the glass transition is manifest in Temperature Modulated DSC is presented, and the effects of both experimental and material parameters are discussed. In conclusion, the two techniques are compared in terms of the information they provide about the glass transformation process. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparison of the localization of an electron as determined by the two-particle distribution function and by the single-particle sharing index

A comparison of the measure of the delocalization of a particle based on the two-particle distribution function and that based on the single-particle density matrix is made using a simple set of wave functions which span states ranging from single determinant ground and doubly excited states through states mimicking correlated states and which include the singly excited state for electrons and for bosons replacing electrons in H2. The comparison further includes an analysis of the application of the measures to a classical ideal gas and a compressible fluid. It is found that the values of the integrated atom-atom measures agree for a range of wave functions involving combinations of the two single determinant (and equivalent Bose) wave functions but disagree for a different range of these wave functions and for the singly excited wave functions. Aside from the single determinant (and equivalent Bose) wave functions, the two sets of point-point measures that underlie the integrated measures all differ. For the sets of wave functions considered, the values of the measures are identical for electrons and bosons. When applied to a closed classical ideal gas and to a closed compressible fluid, the delocalization measure based on the two-particle distribution has a residual long range term, whereas the sharing index in the classical limit gives a completely localized particle. In general, the two measures describe different aspects of the behavior of the particles. The measures based on the two-particle distribution function give only two-particle properties and the single-particle density, and the sharing quantities give only single-particle properties. The latter includes, however, the quantitative measures of the delocalization of a single particle, the point-point sharing index and the sharing amplitude.     

尿素诱导牛血红蛋白变性的微量热和平衡渗析研究

应用恒温微量热技术和平衡渗析技术,对尿素与牛血红蛋白在30℃水溶液中的结合作用及造成牛血红蛋白变性的过程进行了研究,得到了尿素在牛血红蛋白上的平均结合数、二者之间的结合焓及每摩尔尿素与牛血红蛋白结合的焓效应,并根据简单结合模型,计算了它们之间的结合常数、结合自由能.对实验结果的热力学分析表明,尿素是通过直接和间接的两种作用造成牛血红蛋白变性的,它们之间的相互作用分为三个阶段:尿素浓度达到4molL-1之前为第一阶段,主要产生的是尿素与牛血红蛋白的直接结合作用,在弱酸性条件下这种作用较强;尿素浓度为4molL-1到6molL-1之间为第二阶段,主要通过尿素与溶剂水的作用造成牛血红蛋白周围水结构的变化,在尿素浓度达到6molL-1时两种作用的叠加造成牛血红蛋白结构的破坏,暴露出原来处于结构内部的基团;尿素浓度超过6molL-1之后为第三阶段,尿素分子继续与暴露出来的基团进行结合.牛血红蛋白次级结构的维系具有协作性,其结构的破坏不是渐进的,而是一次性全部打开,结构破坏产生的热效应并不太大.     

Antioxidative properties of probucol estimated by the reactivity with superoxide and by electrochemical oxidation

The reaction of probucol with superoxide (O2(*-)) was investigated in acetonitrile using both electron spin resonance (ESR) and electrochemical techniques. The formation of phenoxyl radical was observed during the reaction of probucol with O2(*-) by ESR spectroscopy. The reaction of probucol with O2(*-) in acetonitrile was followed by cyclic voltammetry. With the addition of probucol, the oxidation peak current of O2(*-) decreased concentration dependently. This suggests that probucol reacts with O2(*-), that is, probucol scavenges O2(*-) in acetonitrile. 2,6-Di-tert-butyl-p-benzoquinone was identified as the major product of the reaction of probucol with O2(*-) in acetonitrile. Electrochemical oxidation of probucol was also performed. Probucol gives an irreversible oxidation peak at ca. +1.4 V vs. the saturated calomel electrode in the cyclic voltammogram. Controlled-potential electrolysis was carried out at +1.2 V in a divided cell. 2,6-Di-tert-butyl-p-benzoquinone, 4,4'-dithiobis(2,6-di-tert-butylphenol), and 4,4'-trithiobis(2,6-di-tert-butylphenol) were identified as the products of anodic oxidation. These redox properties of probucol may correlate with the physiological activities.     

Analysis of amides in the air by sampling with SPME and detection by GC-FID

This paper proposes a solid-phase microextraction (SPME) method for the passive sampling and determination of N,N-dimethylacetamide (DMA) and N,N-dimethylformamide (DMF) in air by capillary GC with flame ionization detection. The optimized conditions for SPME method were grab sampling, polydimethylsiloxane/divinylbenzene fiber, extraction for 90 min at 25 +/- 2 degrees C, desorption for 3 min at 220 degrees C, and relative humidity 45 +/- 2%. Under these conditions, the method presented good linearity (R = 0.996), repeatability (%RSD 2.79 and 9.85 for DMF and DMA, respectively), and detection limit (0.021 and 0.024 mg/m3 for DMF and DMA, respectively).     

修饰脂肪酶催化水解反应的动力学和热力学研究

采用邻苯二甲酸酐(PA)对猪胰脂肪酶(PPL)进行了化学修饰,以三硝基苯磺酸法测定修饰酶的平均氨基修饰度,并比较了酶修饰前后的紫外光谱和荧光光谱;采用动力学方法考察了酸碱和热对修饰酶水解活性和稳定性的影响,并计算了一系列动力学和热力学参数.实验结果表明:PA对PPL的修饰度为30%,脂肪酶PPL经PA修饰后,其紫外特征吸收峰发生红移,吸收强度降低,而且最大荧光发射峰发生蓝移,荧光强度增大;PPL经PA修饰前后,催化水解反应的最适pH和最适温度未发生变化,仍为pH7.5和40℃,但修饰后酶催化水解的效率和酶与底物的亲和力得到有效提高,反应的活化能Ea、自由能ΔG≠、活化焓ΔH≠及活化熵ΔS≠均明显降低,如最适条件下修饰酶PA-PPL和脂肪酶PPL的转化数kcat和反应的活化能Ea分别为39.8 s-1、25.8 kJ/mol和34.4s-1、43.8kJ/mol;PPL经PA修饰后,酶分子热变性的热力学参数(变性活化能Ea,d、变性自由能ΔGd≠、变性活化焓ΔHd≠及变性活化熵ΔSd≠)均增大,半衰期t1/2延长,酶分子的热稳定性也得到有效提高.