Effects of diffusion of a naturally-derived plasticizer from soft PVC

Soft PVC was obtained by using a new plasticizer, based on cardanol, a renewable resource characterized by chemical and physical properties very close to those of diethylhexyl phthalate (DEHP). Cardanol acetate (CA) was obtained by solvent free esterification of cardanol, and used as secondary plasticizer, by partial substitution of DEHP in soft PVC formulations. Ageing tests were performed in order to study the stability of properties of the soft PVC formulations related to plasticizer diffusion. Tensile properties and hardness changes were used to monitor the macroscopic effects of plasticizer diffusion. Soft PVC obtained by partial substitution of DEHP by CA showed a significant modification of mechanical properties related to a higher plasticizer evaporation during ageing tests. Migration tests confirmed that CA is characterized by a higher diffusivity in soft PVC compared to DEHP.     

吡啶高三蝶烯的合成

2-溴-4-甲基吡啶（1）经氯代和碘代反应合成了2-溴-4-碘甲基吡啶（3）,3和蒽酮（4）反应生成10,10-二（2-溴-4-吡啶甲基）-9（10H）蒽酮（5）,5在3 MPa下与NaOCH3反应得到10,10-二（2-甲氧基-4-吡啶甲基）-9（10H）蒽酮（6）,6经硼氢化钠还原得到蒽醇（7）,7在对甲苯磺酸催化...     

Acid hydrolysis of carboxymethylcellulose of low degree of substitution

Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.     

The influence of the addition of electrolytes on the degree of dispersion of silver iodide hydrosol

The changes in the degree of dispersion of AgI hydrosols produced by reaction of AgNO₃ and KI with the addition of other electrolytes (1–60 min after addition of AgNO₃ to KI) were investigated by photometric methods. The results obtained suggest that in the process of rapid condensation (caused by a sudden increase in concentration to a value considerably higher than the critical one) colloidal particles do not form by continuous growth of individual nuclei but through disaggregation of loose and amorphous, i. e. thermodynamically unstable clusters of previously formed embryos. This disaggregation process, termed protopeptization by the authors in order to underline its analogy with the peptization process, increases in magnitude with the strengthening adsorption of potential-determining ions (protopeptizing agents) by the particles formed in the precipitation process.     

Recognition of hepatotoxic homologues of Microcystin using a combination of selective adsorption media

Microcystin, a hepatotoxin produced by cyanobacteria, was chromatographically discriminated with newly prepared selective adsorption media. Since the name Microcystin refers to up to 70 different homologues, we have developed a novel technique to prepare selective recognition sites, based on the "Fragment Imprinting Effect". The homologues of Microcystin can be individually discriminated from each other by antigen-antibody assay as well as by C18-based HPLC. This is mainly due to differences in the three dimensional structure of Microcystin homologues; however, differences in toxicity are relatively small among the homologues. Therefore we have to measure the total amount of Microcystin homologues present to determine contamination by Microcystins. We have demonstrated the first group recognition for Microcystin homologues through combination of two different selective adsorption media prepared by a fragment imprinting technique.     

Testing the veracity of claims of Lewis acid catalysis

Are reactions employing Lewis acids really catalysed by those Lewis acids, or by “hidden Brønsted acids”, i.e. Brønsted acids generated in situ by hydrolysis? Testing of a series of reactions using Sc(III), Fe(III), In(III) and Y(III) by addition of 2,6-di-t-butyl-4-methylpyridine reveal that all are likely to follow the latter pathway. A reaction claimed to be catalysed by CBr₄ through halogen bonding is also likely to be Brønsted acid catalysed.     

乙醇胺类原料形成亚硝胺的比较

为了探究目前表面活性剂生产和应用中用脂肪酸甲基单乙醇酰胺或脂肪酸单乙醇酰胺替代脂肪酸二乙醇酰胺的趋势的可行性,本文首先采用亚硝酸叔丁酯法合成3种乙醇胺的亚硝胺化合物作为基准物,通过鉴定产物结构研究亚硝胺的形成历程,然后以亚硝酸法合成亚硝胺化合物,通过生成率比较3种乙醇胺形成亚硝胺化合物的难易程度。 亚硝化历程分析结果表明,二乙醇胺或甲基单乙醇胺均直接形成相应的亚硝胺,而单乙醇胺通过歧化反应生成二乙醇胺继而形成少量N-亚硝基二乙醇胺。 与二乙醇胺相比,甲基单乙醇胺或单乙醇胺更不易生成亚硝胺,因此用脂肪酸甲基单乙醇酰胺或脂肪酸单乙醇酰胺替代脂肪酸二乙醇酰胺是合理可行的。 本研究结果对保障人类生命健康安全具有理论和实践意义。     

Pulse polarographic determination of the complexation capacity of various organic phosphonates of heavy metals with the aid of design of experiments

This study presents the determination of the complexation capacity of phosphonates (ATMP, EDTMP, and DTPMP) by differential pulse polarography. All of them are non-volatile, stable in water samples, and resistant to hydrolysis. Therefore, their decomposition rate in natural water is low. The metal complexation capacity of these phosphonates was detected for cobalt, copper, and zinc ions. DTPMP is the best of the investigated chelating agents for these three metal ions.Owing to the environmental fate of aminocarboxylates, these were often replaced by phosphonates. Therefore, we compared NTA and EDTA with ATMP and EDTMP according to their Zn-CC and could find out approximately four times higher complexation of zinc ions by phosphonates than by aminocarboxylates.Furthermore, the interaction between phosphonates and the influence of iron ions on the Zn-CC were investigated by chemometric means. The design of experiments indicated no significant interaction in phosphonate mixtures but significant influence of iron ions. Thus, the complexation capacity of a mixture of ATMP, EDTMP, and DTPMP can be calculated by the addition of several individual Zn-CC of the phosphonates according to their percentage in the mixture. A similar calculation is impossible in the presence of iron ions.     

CuY制备方法对其催化甲醇氧化羰基化活性中心的影响

以Cu(NO₃)₂为铜源,以NaY和HY分子筛为载体,通过溶液离子交换法和等体积浸渍法制备了不同的无氯CuY催化剂,并进行了气相甲醇氧化羰基化催化活性研究。通过浸渍法制备的催化剂Cu含量为10%,而以NaY和铜氨溶液离子交换制备的催化剂Cu含量只有6.3%,但其催化活性和选择性均较好。通过催化剂的Cu元素分析、低温氮吸附-脱附、XRD、H₂-TPR、XPS和TPD等表征表明,溶液离子交换法制备的催化剂,Cu物种以离子的形式高度分散于分子筛骨架结构中,较好地保持了分子筛晶体结构,并对甲醇有较强的吸附能力,催化活性较高,而将等体积浸渍Cu(NO₃)₂溶液后的HY或NaY分子筛,在400 ℃焙烧过程中,发生了固体离子交换反应,形成了连接于分子筛骨架的Cu²⁺,但以HY为载体更容易进行固体离子交换,未交换的铜物种以CuO的形式分散到分子筛表面。在600 ℃高温活化中,催化剂中Cu²⁺可部分还原为活性物质Cu⁺,但以NaY和铜氨溶液离子交换制备的催化剂Cu²⁺自还原能力最大。     

Emulation of racemase activity by employing a pair of stereocomplementary biocatalysts

Racemization is the key step to turn a kinetic resolution process into dynamic resolution. A general strategy for racemization under mild reaction conditions by employing stereoselective biocatalysts is presented, in which racemization is achieved by employing a pair of stereocomplementary biocatalysts that reversibly interconvert an sp3 to a sp2 center. The formal interconversion of the enantiomers proceeds via a prochiral sp2 intermediate the formation of which is catalyzed either by two stereocomplementary enzymes or by a single enzyme with low stereoselectivity. By choosing appropriate reaction conditions, the amount of the prochiral intermediate is kept to a minimum. This general strategy, which is applicable to redox enzymes (e.g., by acting on R2CHOH and R2CHNHR groups) and lyase-catalyzed addition-elimination reactions, was proven for the racemization of secondary alcohols by employing alcohol dehydrogenases. Thus, enantiopure chiral alcohols were used as model substrates and were racemized either with highly stereoselective biocatalysts or by using (rarely found) non-selective enzymes.     

Comparison study of several numerical integration schemes used in calculations of density functional theory

Several numerical integration schemes for the evaluation of matrix elements in density functional theory calculations have been studied and compared by computational practice. The best scheme was found to be the combination of the atomic partition function proposed by Becke with the scaled generalized Gauss-Laguerre quadrature formula for radial integration suggested by Yang, which achieve the highest convergence rate to the numerical integration. With the same number of integration points, the accuracy of the calculated results by this scheme is higher by 1 to 2 orders of magnitudes than that by other schemes. The reason for achieving higher accuracy by this scheme has been proposed preliminarily.     

Chronocoulometric study of the electrochemistry of Prussian blue

During the electrochemical oxidation of Prussian blue (PB) to Prussian yellow (PY), an electrocatalytic oxygen production proceeds at the electrode when aqueous electrolyte solutions are used. The formed oxygen is scavenged by the PY, probably by absorption, and it is consumed during the electrochemical reduction of PY to PB by a heterogeneous chemical reaction of PB with oxygen to PY and hydrogen peroxide. Because of this catalytic regeneration of PY, it is impossible to determine the amount of low-spin iron by chronocoulometry using a potential program in which PB is first oxidized to PY and then the charge is measured to reduce PY to PB. The latter charge is biased by the electrocatalytic PY regeneration.     

Preparation of Hybrid Nanocapsules

Hybrid nanoparticles with a polystyrene core and a hybrid copolymer shell were used to produce hybrid nanocapsules by dissolving the polystyrene core from the previously elaborated core-shell particles. Following previous works, the core-shell particles were prepared by emulsion polymerization of styrene and subsequent addition of γ-methacryloxy propyl trimethoxy silane (MPS) to produce the shell by copolymerization reaction of MPS with the residual styrene. Core extraction was performed by diluting the core-shell particles in an excess of tetrahydrofuran (THF). Two procedures were investigated to separate the dissolved polymer chains from the nanocapsules. In the first procedure, the polymer was isolated by successive centrifugation and redispersion in THF, whereas in the second procedure, the free polymer chains were removed by dialysis. The polymer molecular weight was optimized in order to promote dissolution of the polymer chains and allow them to diffuse through the shell.     

利用两种微生物的协同作用进行柴油的深度脱硫

红串红球菌通过4S途径降解二苯并噻吩(DBT)产生 和2-羟基联苯(2-HBP). 和2-HBP的存在对红串红球菌的进一步脱硫有抑制作用, 加入脱 和2-HBP 的菌株可以解除 和2-HBP对红串红球菌脱硫反应的抑制, 使该反应继续向生成产物的方向移动, 从而提高其脱硫率. 在脱硫菌和专一性降解 的水解好氧菌(代号: PYS)的协同作用下可以使高浓度的DBT从1.142 mmol/L降到0.0468 mmol/L, 降解率达到95.9%, 比没有加PYS时提高32%的脱除率. 在油水比为1∶9的条件下, 可以将柴油中的硫从554 mg/mL降到306 mg/mL, 降解率达到44.8%.     

Stereoselective synthesis of the octahydroisobenzofuran skeleton of the eunicellins

A de novo asymmetric synthesis of the octahydroisobenzofuran skeleton contained within the eunicellin family of natural products has been completed. The key transformations involve the convergent assembly of a tetrasubstituted tetrahydrofuran by condensation of a functionalised allylsiloxane with an aldehyde; controlled epimerisation of a C4 aldehyde by intramolecular trapping; installation of the isopropyl substituent by stereoselective Michael addition to a 5,5-bicyclic enone; and ring expansion of the 5,5-system to the target structure by radical-mediated cyclopropane fragmentation.     

Synthesis of hexasaccharide fragments of pectin

Short syntheses of partially methyl-esterified hexagalacturonates 1-5 are described as part of the development of strategies for the preparation of larger pectic oligosaccharides. The methodology is based on the repeated coupling of galactose mono- and disaccharide donors onto a galactose acceptor until a hexagalactan is obtained. All glycosylations are carried out with n-pentenyl glycosides to provide good yields of the desired alpha anomers. Pentenyl disaccharide donors are prepared by the coupling of two pentenyl galactosides controlled by either the armed-disarmed effect or by converting one pentenyl galactoside into the corresponding galactosyl bromide or fluoride. Two orthogonal protecting groups are employed at C6, which makes it possible to oxidize these positions to either the carboxylic acid or to the methyl ester. Each hexagalactan is therefore able to bifurcate into two different hexagalacturonates with a reverse methyl-esterification pattern. The methyl ester distribution in the hexagalacturonates is confirmed by tandem mass spectrometry.     

Versatility of cyclodextrins in self-assembly systems of amphiphiles

Recently, cyclodextrins (CDs) were found to play important yet complicated (or even apparently opposite sometimes) roles in self-assembly systems of amphiphiles or surfactants. Herein, we try to review and clarify the versatility of CDs in surfactant assembly systems by 1) classifying the roles played by CDs into two groups (modulator and building unit) and four subgroups (destructive and constructive modulators, amphiphilic and unamphiphilic building units), 2) comparing these subgroups, and 3) analyzing mechanisms. As a modulator, although CDs by themselves do not participate into the final surfactant aggregates, they can greatly affect the aggregates in two ways. In most cases CDs will destroy the aggregates by depleting surfactant molecules from the aggregates (destructive), or in certain cases CDs can promote the aggregates to grow by selectively removing the less-aggregatable surfactant molecules from the aggregates (constructive). As an amphiphilic building unit, CDs can be chemically (by chemical bonds) or physically (by host–guest interaction) attached to a hydrophobic moiety, and the resultant compounds act as classic amphiphiles. As an unamphiphilic building unit, CD/surfactant complexes or even CDs on their own can assemble into aggregates in an unconventional, unamphiphilic manner driven by CD–CD H-bonds. Moreover, special emphasis is put on two recently appeared aspects: the constructive modulator and unamphiphilic building unit.     

Combination of LC-ICP-MS, LC-MS and NMR for investigation of the oxidative degradation of selenomethionine

Selenomethionine (SeMet) was oxidized by heating an acidic solution with hydrogen peroxide. Samples were taken before and during the oxidation process. The oxidation products were separated by cation exchange chromatography followed by ICP-MS detection to identify the selenium containing compounds as well as electrospray ionization MS detection to determine the masses of the degradation products. Furthermore, the samples were analyzed by ⁷⁷Se-NMR. The first appearing degradation product was selenomethionine selenoxide, which was converted via the deaminated selenoxide to methane seleninic acid and selenite.     

Oxidations and reductions of iron-cyanogen compounds of cobalt,nickel, cadmium and zinc

I. Cobalt ferrocyanide is oxidized by bromine water, by nitrous acid or by hydrogen peroxide in presence of acids to cobalt ferroferricyanide (cobalt Prussian blue), while cobalt ferricyanide is reduced by sulfurous acid to cobalt Prussian blue.II. Nickel ferrocyanide is oxidized by nitrous acid or by hydrogen peroxide in presence of acids to nickel ferricyanide.III. Nickel ferrocyanide and cadmium ferrocyanide are oxidized by bromine water to the ferricyanides.IV. The ferricyanides of nickel, cadmium and zinc are reduced by sulfurous acid to the ferrocyanides.     

Contribution of the secondary crystallization to the overall crystallinity of heatset polyester

The crystallinity of poly(ethyleneterephthalate) has been determined by differential scanning calorimetry and by density. The results obtained by calorimetry show that the increment in the crystallinity due to the heatsetting treatment is produced by the increase of the crystallinity corresponding to the premelting endothermic peak.