Mechanism of radiation-induced addition reaction of carbon tetrachloride onto liquid 1,2-polybutadiene accompanied by cyclization

Effects of irradiation conditions were investigated in the γ-ray-induced addition reaction of carbon tetrachloride onto liquid 1,2-polybutadiene. The rate of addition reaction was proportional to the dose rate, and its apparent activation energy was 1.4 kcal/mole in the range of ca. 20–80°C; the G values for the addition of carbon tetrachloride and vinyl consumption were high. The addition reactions of methyl isobutylate, isopropyl amine, and bromotrichloromethane to liquid 1,2-polybutadiene by γ rays were studied to compare with carbon tetrachloride. Methyl isobutylate and isopropyl amine were added much more slowly. On the other hand, in bromotrichloromethane the rate of addition reaction was much faster but cyclization was less pronounced than in carbon tetrachloride. On the basis of these results a mechanism of a radical chain reaction which includes the addition of carbon tetrachloride, cyclization, and crosslinking, is proposed.     

Determination of copper,iron and zinc in spirituous beverages by total reflection X-ray fluorescence spectrometry

The concentration of copper in traditional homemade alcoholic distillates produced in Venezuela (Cocuy de Penca) were determined by total reflection X-ray fluorescence (TXRF) using vanadium as internal standard. The results were compared to those obtained by flame atomic absorption spectrometry (FAAS). Three preparative methods of addition of vanadium were compared: classical internal standard addition, ‘layer on layer’ internal standard addition and in situ addition of internal standard. The TXRF procedures were accurate and the precision was comparable to that obtained by the FAAS technique. Copper levels were above the maximum allowed limits for similar beverages. Zinc and iron in commercial and homemade distilled beverages were also analyzed by TXRF with in situ addition of internal standard demonstrating the usefulness of this technique for trace metal determination in distillates.     

Degradation of Acetophenone in Water by Pulsed Corona Discharges

Degradation of acetophenone in dilute aqueous solution has been studied using pulsed corona discharges in water. Higher conversions of acetophenone were obtained with the addition of oxygen or ozone than with the addition of nitrogen and without the addition of any gas. Intermediates of acetophenone degradation, as determined by gas chromatography–mass spectroscopies (GC–MS), were phenethyl alcohol, toluene, and 2-acetylphenol. In addition, the degradation reaction pathways of acetophenone in water are discussed.     

Effect of Monomer Feeding Mode on thePreparation of Hollow Latexes with High MAA Content in the Core Latex Preparation简

In order to prepare hollow latex particles with optimum morphology based on osmotic swelling principle, three- layer core/shell latex particles with 40 wt% MAA in the core were first prepared via multistep seeded emulsion copolymerization, in which monomers were added by a semi-continuous process with monomer addition under two different forms： pure monomers＇ mixture （monomer addition）, and pre-emulsified monomers （pre-emulsion addition）. Then, the hollow latex particles with different morphologies were obtained after alkali post-treatment. Influences of the monomer feeding mode on the emulsion polymerization and the particle morphology were investigated. Results showed that the pre- emulsion addition could significantly improve the polymerization stability in each step, and greatly enhance the uniformity of shell encapsulation. The sizes of the core and core/shell latex particles obtained by the pre-emulsion addition were smaller and more uniform than those synthesized by the monomer addition, and the hollow latex particles with intact morphology were generated by alkali post-treating of the core/shell latexes prepared from the pre-emulsion addition. As the core size increased, the morphology of the post-treated particles underwent evolution from hollow to collapse. Moreover, the mechanism of the particle morphological evolution was proposed.     

A highly regio- and enantioselective organocatalyzed Michael addition of malonates to nitrodienes

An organocatalyzed direct Michael addition of unsubstituted/substituted malonates, acetoacetate, or acetylacetones to conjugated nitrodienes using a cinchona alkaloid-based thiourea catalyst is disclosed. The addition products were formed in high yields and regioselectivity. The enantioselectivities of the addition products were high in most cases and could significantly be improved upon by a single recrystallization. The addition products easily undergo chemoselective nitro group reduction and subsequent lactamization with a high synthetic potential.     

Chemical modifications of polycyclopentadiene

Polycyclopentadiene, which is known to undergo extremely fast autoxidation resulting in insoluble products, was chemically modified, leading to derivatives no longer sensitive to oxygen. Soluble and stable products can be obtained in high conversions by Diels-Alder addition of hexachlorocyclopentadiene (96.5 mole-%), by epoxidation (93.5 mole-%), and by addition of thioglycolic acid (97.9 mole-%). A prerequisite is an efficient purification of polycyclopentadiene via reprecipitations in an oxygen-free atmosphere. Other attempted alterations of the double bond were the hydroxyformylation and the free-radical addition of haloalkanes, which, however, resulted in completely insoluble products. Typical addition reactions were carried out with the epoxy derivative of polycyclopentadiene, e.g., additions of hydrogen chloride, monochloracetic acid, chlorophenol, thiophenol, piperidine, hydrolysis to glycols. Easily initiated polymerization of the epoxy group is believed to be a conversion-limiting side reaction in certain addition reactions, such as addition of hydrochloric acid or hydrolysis to glycols.     

液液萃取-GC-MS法测定水中硝基苯质量控制指标研究

采用液液萃取–气相色谱–质谱法测定水中硝基苯,通过统计全国多家实验室的测定数据,对平行样测定结果相对偏差、空白加标回收率、样品加标回收率、空白加标回收率相对偏差及样品加标回收率相对偏差5个质控指标进行分析,得出质控指标评价标准。在概率P,γ均为0.90时,平行样测定结果允许最大相对偏差应控制在11.0%;当空白加标浓度为0.2～30μg/L时,回收率控制范围为59%～113%;当样品未检出、加标浓度在0.25～50μg/L时,样品加标回收率控制范围为56%～110%;空白加标、样品加标回收率最大相对偏差应分别控制在10.0%和11.1%。在概率P和γ均为0.95时,平行样测定结果允许最大相对偏差应控制在13.5%;当空白加标浓度为0.2～30μg/L时,回收率的控制范围为50%～122%;当样品未检出、加标浓度在0.25～50μg/L时,样品加标回收率控制范围为49%～117%;空白加标、样品加标回收率最大相对偏差应分别控制在12.6%和14.6%。     

表面活性剂对CdSe量子点荧光性能的影响

通过添加不同类型的表面活性剂在水相中制备了CdSe量子点。用透射电子显微镜(TEM)、X射线衍射(XRD)、X-射线光电子能谱(XPS)对其进行了表征,并用紫外-可见(UV-Vis)和荧光(PL)分光光度法研究了不同类型的表面活性剂对CdSe量子点吸收光谱和荧光光谱的影响。结果表明,加入长链的非离子型和阴离子型表面活性剂制备的CdSe量子点颗粒只有几个纳米,分散性好,量子点的荧光强度也有明显的增强,而加入阳离子表面活性剂制备的量子点颗粒团聚明显,其荧光出现淬灭。     

5-烷氧基-2(5H)-呋喃酮在有机合成中的应用

综述了国内外5-烷氧基-2（5H）-呋喃酮通过Michael加成、[3＋2]环加成、光催化加成等反应在有机合成中的应用。参考文献56篇。     

Analysis of an asymmetric addition with a 2:1 mixed lithium amide/n-butyllithium aggregate

A 2:1 lithium amide/ n-butyllithium aggregate 1 is investigated as an asymmetric addition template in hydrocarbon solvents. Several different chiral lithium amides were synthesized from l-valine and tested in the asymmetric addition of n-BuLi to various aldehydes. Enantiomeric excesses up to 83% were obtained in the case of the addition of n-BuLi to pivaldehyde at -116 degrees C in pentane. (1)H and (13)C INEPT DOSY were utilized to characterize a new trimeric complex 12 between 2 equiv of lithium amide and 1 equiv of lithium alkoxide. This mixed aggregate strongly indicates the possibility of product-induced chirality inhibition that is detrimental to the enantioselectivity of asymmetric addition reaction.     

Thermal decomposotion and rearrangement of branched methylsiloxane oligomers

The pyrolysis products of bi-, tri- and poly-cyclic methylsiloxane oligomers were studied using gas chromatography; it was concluded that reversible elimination and addition of dimethylsilanone groups led to the observed product distribution. Polycyclic siloxane oligomers were pyrolysed together with cyclic dimethylsiloxanes in order to investigate the addition reactions. The splitting of the polycycles into bicycles containing only two branching points was observed as a consequences of dimethylsiloxane addition above 500°C.     

Radiation-Induced Addition Reaction of Ethyl Mercaptan and Carbon Tetrachloride to 1,2-Polybutadiene

γ-Ray-induced addition reactions of syndiotactic 1,2-polybuta-diene film with various compounds were carried out at room temperature. The weight of the film markedly increased when ethyl mercaptan was used. In the reaction with ethyl mercaptan, only addition took place without crosslinking. The addition of ethyl mercaptan to the vinyl group of syndiotactic 1,2-poly-butadiene followed anti-Markownikoff rule, and gave a 1:1 addition product. The rate of addition increased as the crys-tallinity of syndiotactic 1,2-polybutadiene used became lower. A similar relation between the crystallinity and the rate of addition was also observed in the γ-ray-induced addition of carbon tetrachloride to syndiotactic 1,2-polybutadiene, but at the same time gelation was pronounced. When liquid 1,2-polybutadiene was used instead of syndiotactic-1,2-polybutadiene, gelation which made the polymer insoluble in carbon tetrachloride did not take place, although a crosslinking reaction was noted. The appearance of the product in this case changed from a viscous liquid to a white powder as the reaction proceeded. The addition of carbon tetrachloride to the vinyl group of liquid 1,2-polybutadiene was also of the anti-Markownikoff type. This addition was accompanied by unexpectedly large vinyl consumption. The total decrease in vinyl group was found to be much larger than the decrease in vinyl group which was brought about by the addition of carbon tetrachloride. This discrepancy was attributed to cyclization and crosslinking reactions which were ascribed to the vinyl group bound by the main chain.     

3-叔丁氧甲酰基氨基吡咯烷催化酮和硝基芳基乙烯的不对称Michael加成

用3-叔丁氧甲酰基氨基吡咯烷催化酮和硝基芳基乙烯的不对称Michael加成,并考察了反应物结构对加成的影响,得到了较高的收率和较好非对映选择性.     

Synthesis of different types of valerolactams starting from 2,5-dihydrooxazoles

Tricyclic valerolactams characterized by a variable heteroatom in γ-position, for example, sulfur, oxygen or nitrogen, were synthesized starting from 2,5-dihydrooxazoles. The chosen synthetic procedures included the addition of thiosalicylic acid as well as the addition of salicyl chloride. The nitrogen containing lactams were prepared in a cycloaddition and subsequent oxidation.     

C60的六加成反应

以六加成反应为代表的C60的多加成反应已经成为富勒烯化学的一个重要组成 部分。综述了C60的六加成反应，包括具有不同对称性的各种C 60六加成产物的合 成和表征，以及六加成产物的基本性质和应用。     

Influence of yttria addition on the phase transformations of zirconia from zircon ore by carbothermal reduction process

Zircon ore carbothermal reduction with yttria addition has been carried out. The influences of heating temperature and yttria addition on the phase transformations of zirconia from zircon ore by carbothermal reduction have been investigated in detail. The phase transformations of zirconia from zircon ore by carbothermal reduction were monitored by X-ray diffraction. The microstructure and micro-area chemical analysis of the products were characterized by scanning electron microscopy and energy dispersive spectrometer. The chemical states of Zr 3d, Y 3d and O 1s presented in the products of zircon carbothermal reduction with 10 wt% yttria addition were investigated by X-ray photoelectron spectroscopy. The results showed that the optimized heating temperature of zircon carbothermal reduction with no addition was 1600 °C, and the main phase of the products consists of m-ZrO₂, c-ZrO₂, ZrC and β-SiC. Yttria addition could be introduced into zirconia lattice and caused it to form Y₂O₃ stabilized zirconia. Zirconia in the products would be turned into partially stabilized zirconia with yttria addition from 1 wt% to 5 wt% while it would exist in the form of fully stabilized zirconia with over 8 wt% yttria addition.     

Oxidative addition of aryl tosylates to palladium(0) and coupling of unactivated aryl tosylates at room temperature

Aryl tosylates are attractive substrates for Pd-catalyzed cross-coupling reactions, but they are much less reactive than the more commonly used aryl triflates. We report the oxidative addition of aryl tosylates to Pd(PPF-t-Bu)[P(o-tolyl)3] and to Pd(CyPF-t-Bu)[P(o-tolyl)3] at room temperature to produce the corresponding palladium(II) aryl tosylate complexes. In the presence of added bromide ions, arylpalladium(II) bromide complexes were formed. The rate of oxidative addition was accelerated by addition of either coordinating or weakly coordinating anions, and the reactions were faster in more polar solvents. The mild conditions for oxidative addition allowed for the development of Pd-catalyzed Kumada couplings and amination reactions of unactivated aryl tosylates at room temperature. The catalysts for these mild couplings of aryl tosylates were generated from palladium precursors and the sterically hindered Josiphos-type ligands that induced oxidative addition of aryl tosylates to Pd(0) at room temperature.     

Rheological properties of doughs with buckwheat and quinoa additives

Rheological properties of doughs prepared from wheat flour with buckwheat and quinoa flour addition (2.5 mass %, 5.0 mass %, 7.5 mass %, and 10 mass %) were investigated using a farinograph and compared with those of standard dough (without addition of pseudocereals). The following characteristics were determined: water absorption capacity, water consumption, dough growth time, level of dough softening, dough stability, mechanical resistance, and dough elasticity. Dough stability showed a linear decrease with the increasing content of pseudocereals. Doughs containing quinoa flour were more stable than those with buckwheat flour addition. Dough growth time was reduced with increasing amounts of buckwheat flour but it was not affected in the case of quinoa flour addition. From the comparison of the studied characteristics it can be concluded that an addition of lower amounts of quinoa (up to 5.0 mass %) to wheat flour will not significantly impair rheological properties of the dough but provides for enhanced nutritional value of the prepared bakery products.     

The Effect of Salvia hispanica and Nigella sativa Seed on the Volatile Profile and Sensory Parameters Related to Volatile Compounds of Dry Fermented Sausage

The aim of the study was to evaluate the effects of Salvia hispanica and Nigella sativa seed addition on the volatile compounds and sensory characteristics (with particular emphasis on odor and flavor) of traditionally produced dry fermented sausages with reduced nitrites. Five different sausage formulations were prepared: control sample; samples with 1% and 2% addition of chia seed; samples with 1% and 2% addition of black cumin seed. The sausages were subjected to analysis including proximate chemical composition, volatile compound determination, and sensory analysis. The sausages with chia seed in the amounts of 1% and 2% as well as the sample with 1% addition of black cumin seed were characterized by positive sensory features, and their overall quality was rated above 7 c.u. on a 10-point scale, similar to the control sausage. Sausage samples with the addition of cumin seed were characterized by the highest herbal odor and flavor. The addition of Salvia hispanica and Nigella sativa seed significantly affected the amount of volatile compounds in fermented sausages. Sausages with black cumin presented the greatest amount of total volatile compounds, mainly contributed by terpenes.     

Effect of polyvinylchloride on the properties of rubber vulcanizates

Natural rubber (NR) and styrene-butadiene rubber (SBR) were compounded with polyvinylchloride (PVC). Some physico-mechanical and dielectric properties of resulting rubber vulcanizates were measured. It was found that the addition of PVC to both NR and SBR results in slight decreases in tensile strength and elongation at break but a marked increase in oil-resistance of the vulcanizates. Moreover, the addition of PVC to NR slightly increases both dielectric constant and dielectric losses while the addition of PVC to SBR loaded with 50 phr carbon black (HAF) lowers these parameters. Both rubber blends, especially NR, show a reasonable stability with ageing.