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.     

On-Line Standard Addition Technique for the Determination of Elements in the Samples with High Dissolved Solids by ICP-OES: Application to Determination of Rare Earth Elements in Geological Samples

A simple and rapid on-line standard addition method for analysis of samples with high dissolved solids by ICP-OES is reported. The method involves on-line addition of standard solutions to the sample using a T-piece, prior to the sample introduction system. The standard addition method is commonly used in the analysis of samples with complex matrices. However, the conventional standard addition method is a tedious and time-consuming process. Therefore, in this study, on-line standard addition technique was offered to significantly decrease the analysis time and increase the simplicity of the standard addition method. The performance of the proposed method was tested by determination of rare earth elements in geological samples. This method showed a high level of accuracy in comparison with external calibration and internal standard addition methods.     

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.     

[6+2] Cycloaddition of N-phenyltriazolinedione with cycloheptatriene derivatives mediated and stereodirected by a chiral 3-oxy substituent

The addition of N-phenyltriazolinedione to a 7,7-dimethylcycloheptatriene derivative afforded a [6+2] adduct, which was found to be produced by the rearrangement of an initially formed [4+2] adduct. The regioselectivity of the initial addition was controlled by the 3-oxy-substituent, which also mediates the PTAD addition to the tropilidene form. The chiral 3-substituent also controlled the stereoselectivity of the addition to a high degree.     

Catalytic asymmetric addition of dialkylzinc reagents to alpha-aldiminoesters

[reaction: see text] The first catalytic, enantioselective addition of organozinc reagents to alpha-aldiminoesters is described. The use of a Lewis acid/Lewis base containing bifunctional catalyst preorganizes both reactive substrates to promote enantioselective addition over the racemic background reaction and alternative addition modes. Alcohol additives were found to enhance the enantioselection. The addition product was also found to cyclize with remaining substrate to provide imidazolidines.     

Anionic Polymerization Chemistry of Epoxides: Electron-Transfer Processes

The reaction of poly(styryl)lithium (PSLi) with styrene oxide (SO) in benzene solution has been investigated. In addition to the functionalized polymer (83.5 wt %) the product mixture consisted of unfunctionalized polymer (9 wt %) and a dimeric product (5.6 wt %). The structure of the dimeric product was determined to be the head-to-head dimer. The regiochemistry of the addition reaction was unselective: 53 mol % addition to the methylene carbon and 47 mol % corresponding to addition to the hindered, methine carbon. Based on the formation of the dimer and the lack of regioselectivity, a pathway involving electron transfer from PSLi to SO was proposed. To further investigate the propensity to react via this electron-transfer mechanism, the SO functionalization of the adduct of PSLi with 1,1-diphenylethylene was investigated as well as the functionalization of PSLi with 1,1-diphenylethylene oxide.     

Effect of polyamines on shoot multiplication and furanocoumarin production in Ruta graveolens cultures

The influence of the polyamines putrescine (Put), spermine (Spr) and spermidine (Spd) on growth and furanocoumarin production was investigated by exogenous addition, at different concentrations, to shoot cultures of Ruta graveolens at different phases of growth. Preliminary studies indicated that addition of Put (20 microM) and Spr (80 microM) had a promotive effect on shoot multiplication rate and number of multiple shoots formed. Spd was toxic, even at lower concentrations. The growth-phase of the culture at the time of exogenous addition of polyamines was found to be an important factor. Put was most effective when added at the lag phase, while Spr was most effective when added in the log phase. Time course studies of growth and furanocoumarin content were carried out for each polyamine and phase of addition. It was seen that maximum production of furanocoumarins (256.8 mg/10 g DW) occurred in the second week when Put was added in the lag phase and 260.5 mg/10 g DW in the fourth week when Spr was added in the log phase. Put addition resulted in a 3.10 fold increase in psoralen, 6.12 in xanthotoxin and 1.46 fold in bergapten production. Spr addition resulted in a 1.31 fold increase in psoralen, 4.11 fold in xanthotoxin and 1.49 fold in bergapten production. Results indicate that alteration of growth and furanocoumarin production kinetics is a combined outcome of choice of polyamine and the phase of culture at the time of exogenous addition. Polyamine addition enabled significant enhancement in production of pharmaceutically important bergapten and xanthotoxin in shoot cultures of Ruta graveolens, which could be explored for commercial production.     

Effect of surface interaction of silica nanoparticles modified by silane coupling agents on viscosity of methylethylketone suspension

In order to control the viscosity of a dense silica methylethylketone (MEK) suspension, the surfaces of silica nanoparticles were modified by 3-glycidoxypropyltrimethoxysilane (GPS) or hexyltrimethoxysilane (C6S) in MEK with the addition of a small amount of pH-controlled water. First, the effect of water addition on the amount of chemisorbed coupling agent was investigated. pH-controlled water enhanced the reactivity of the coupling agent in MEK. The amount of chemisorbed coupling agent increased slightly with the addition of pH 3 water and increased remarkably with the addition of pH 12 water. Next, the effect of the organic functional groups of the coupling agent, pH of the additive water, and additive amount of coupling agent on surface interaction were determined by colloid probe AFM. The steric repulsive force between the silica nanoparticles increased due to water addition, particularly when the pH was maintained at 3. The viscosity of the silica MEK suspension reduced effectively when this repulsive force appeared; however, the optimum condition for reducing the suspension viscosity was dependent on the coupling agent species. The viscosity of the dense silica MEK suspension can be controlled by the addition of small amounts of pH-controlled water and the functional groups of the coupling agent.     

Preparation of degradable polypropylene by an addition of poly(ethylene oxide) microcapsule containing TiO2

In order to prepare a novel photo-degradable polypropylene (PP), an addition of poly(ethylene oxide) (PEO) microcapsule containing TiO₂ to PP was performed. Adsorbed H₂O in the PEO phase and the TiO₂ photocatalytically reacted, and a hydroxyl radical (OH), which initiated the PEO degradation, was produced. The degraded PEO produced an acid and an aldehyde, which were able to facilitate PP degradation. The addition of the PEO/TiO₂ microcapsule brought about the facilitative effect of the PP degradation. In addition, an addition of a hindered amine light stabilizer (HALS) had a potential to suppress the PP degradation initiated by the microcapsule. The suppression effect was rising by the simultaneous addition of a phenolic antioxidant in the early phase of the PP degradation. However, the simultaneous addition showed an antagonism after 4 h degradation. This behavior suggested that the HALS also worked as a neutralizer of the produced acid.     

Radiation-induced addition reaction of carbon tetrachloride onto 1,2-polybutadiene

The γ-ray-induced addition reaction of carbon tetrachloride onto syndiotactic 1,2-polybutadiene film and liquid 1,2-polybutadiene was carried out at room temperature. In the film gelation was pronounced and the rate of addition increased as the crystallinity of the polymer decreased. In the liquid gelation, which makes the polymer insoluble in carbon tetrachloride, did not take place, although a definite crosslinking reaction was noticed. In this case the appearance of the product changed from a viscous liquid to a white powder as the reaction proceeded. Its structure was compared with that of chlorinated 1,2-polybutadiene. The addition of carbon tetrachloride to the vinyl group in liquid 1,2-polybutadiene caused an anti-Markownikoff-type reaction and was accompanied by an unexpectedly large vinyl depletion in the polymer. The total decrease in the vinyl group was found to be much larger than that brought about by the addition of carbon tetrachloride. This discrepancy was attributed to a cyclization and crosslinking reaction ascribed to the vinyl group bound by the main chain. Cyclization and crosslinking were less noticeable in the chlorination than in the carbon tetrachloride.     

用氨基酸加和法计算多肽的脂水分配系数

Based on amino acid addition model, a set of hydrophobicity contributions of amino acids was obtained from the multivariate linear regression analysis of peptides' octanol/water partition coefficients. Multivariate regression was performed on a training set of 219 peptides including dipeptides to pentapeptides which we compose 21 natural amino acids. The correlation coefficients for the whole set fitting are 0. 978 and 0- 974, for log P and log D respectively. In addition, a new test method -evolution test-for regression analysis was discussed. The result of evolution test for amino acid addition model shows the advantage of this new test method.     

标准加入法在酸碱分析中的应用

本文推导了单元酸标准加入法的线性公式。在被测酸溶液中,等量加入同种酸的标准溶液多次,并记录pH值,代入线性公式计算后即可得一直线,该直线在纵轴上的截距为被测酸浓度,斜率为该酸的条件稳定常数。本文还对单元酸及其共轭碱的标准加入法同时测定进行了研究。     

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.     

Crystal phase evolution of TiO2 nanoparticles with reaction time in acidic solutions studied via freeze-drying method

The crystal phase evolution of TiO₂ nanoparticles, during hydrolysis and condensation of titanium tetraisopropoxide, was quenched at various reaction times by a freeze-drying method, followed by various characterizations. Three types of solutions with different acid input times were studied: (1) addition in infinite time (no addition), (2) addition at 24 h after the hydrolysis/condensation reaction started, and (3) addition from the beginning of the reaction. The acid-free solution yielded amorphous TiO₂, which transformed to anatase very slowly. The acid input in 24 h resulted in a fast transformation of amorphous to a metastable anatase having a highly distorted atomic arrangement: thereby its transformation to a more stable phase, rutile, was suitable. The acid addition from the beginning of the reaction yielded the formation of a relatively stable anatase from the hydrolysis seed, thereby the subsequent transformation to rutile was sluggish.     

一种可精确控制粒径的SiO2微球合成方法

用改进的种子法合成SiO2微球. 微球生长过程中连续缓慢添加正硅酸乙酯,使用动态光散射法实时监控微球粒径的增长过程,调节正硅酸乙酯的添加,实现对粒径的精确控制. 为制备禁带位置位于1000 nm 的光子晶体,合成粒径为446 nm的SiO2微球,微球粒径在4 h内从193 nm 增长到446 nm,远远快于传统种子法,微球粒径与目标粒径偏差为±5 nm. 制得的SiO2微球被组装为光子晶体,其禁带位置恰好位于1000 nm.     

Hyperproduction of l-glutamate oxidase in submerged fermentation of Streptomyces sp. N1 with culture pH control and calcium addition

Production of l-glutamate oxidase (GluOx) by Streptomyces sp. N1 was investigated by controlling culture pH at 6.2, 6.7, 7.0, and 7.3 in a 5-l stirred fermentor. The corresponding GluOx activities obtained were 2.8, 4.2, 6.0, and 5.3 U/mL, respectively. Microbial growth was inhibited by increasing the medium pH from 6.2 to 7.0. The inhibitory effect was also observed in plate colony growth under incubation with a different initial pH value. The effect of calcium on GluOx production was also studied in the pH-controlled bioreactor. When the culture pH was controlled at 6.2 or 7.0, GluOx production could not be improved or was only improved slightly by initial addition of calcium to the medium. However, when the culture pH was kept at 6.7, initial Ca²⁺ addition (60 mM) conspicuously enhanced GluOx production up to 9.3 U/mL, which was about twofold of that without Ca²⁺ addition. The enzyme production level was the highest ever reported in the literature. During fermentation the inhibition of cell growth by Ca²⁺ addition was observed. For the morphological changes, the cells mostly existed as pellets in the medium without Ca²⁺ addition, whereas few pellets were found and almost all the cells were dispersed mycelia in the broth with Ca²⁺ addition.     

Role of monomer charge-transfer complexes in the free-radical copolymerization of styrene and fumarodinitrile

The equilibrium constant of the charge-transfer complex of styrene and fumarodinitrile was determined by ultraviolet and NMR measurements. Information about the role of the complex in the copolymerization of the two monomers could be obtained from copolymerization experiments at different monomer concentrations and temperatures. In addition, the influence of a second donor, anisole, was studied. The results show that in the copolymerization of styrene with fumarodinitrile addition of charge-transfer complexes has to be taken into account besides the addition of the free monomers.     

Isotope effects and the mechanism of epoxidation of cyclohexenone with tert-butyl hydroperoxide

The mechanism of the epoxidation of 2-cyclohexen-1-one with tert-butyl hydroperoxide mediated by DBU was studied by a combination of experimental kinetic isotope effects (KIEs) and theoretical calculations. A large 12C/13C (k(12C)/k(13C)) isotope effect of approximately equal to 1.032 was observed at the C3 (beta) position of cyclohexenone, while a much smaller 12C/13C isotope effect of 1.010 was observed at the C2 (alpha) position. Qualitatively, these results are indicative of nucleophilic addition to the enone being the rate-limiting step. Theoretical calculations support this interpretation. Transition structures for the addition step lead to predicted isotope effects that approximate the experimental values, while the predicted isotope effects for the ring-closure step are not consistent with the experimental values. The calculations correctly favor a rate-limiting addition step but suggest that the barriers for the addition and ring-closure steps are crudely similar in energy. The stereochemistry of these epoxidations is predicted to be governed by a preference for an initial axial addition, and the role of this preference in experimental diastereoselectivity observations is discussed.     

3,5-二(2-吡啶基)吡唑的合成方法改进

以2-吡啶甲酸为原料,经酯化、缩合、加成合成了平面四齿双核配体3,5-二(2-吡啶基)吡唑。改进合成方法使加成反应的产率由原来的66%提高到98%。