Identification of cis/trans isomers of methyl ester and oxazoline derivatives of unsaturated fatty acids using GC–FTIR–MS

Identification of cis/trans isomers of unsaturated fatty acids cannot usually be achieved by GC-MS (gas chromatography-mass spectrometry) without reference substances. In this study a GC-FTIR-MS system (gas chromatography-Fourier transform-mass spectrometry) was used to identify fatty acid methyl esters (FAMEs) and differentiate between the cis/trans isomers. Besides methyl esters, 2-alkenyl-4,4-dimethyloxazoline derivatives (DMOX), which have been used to locate double bond positions of unsaturated fatty acids, were examined with respect to their suitability for cis/trans differentiation. A combined GC-FTIR-MS system with a wide band (4000–550 cm^?1) mercury cadmium telluride (MCT) detector was used in series and parallel to identify 31 reference unsaturated fatty acids, including 7 pairs of cis/trans isomers. Serum samples of healthy persons and commercially available fish oil were analyzed as examples of complex mixtures. Using splitless injection the detection limit for the less sensitive IR detector was 25 ng/μl in case of the weak cis and trans bands. In the FTIR spectra cis/trans isomers were identified by analysis of bands arising from C? H out-of-plane (oop) bending: for both the FAME and DMOX derivatives cis-1,2-disubstituted double bonds give a strong band near 720 cm^?1 and the corresponding trans isomers near 967 cm^?1. cis Isomers could be identified further by a band at 3012 cm^?1. With the combined data of the GC-FTIR-MS system it is now possible to identify polyunsaturated fatty acids with regard to the discrimination of cis/trans isomers.     

催化动力学光度法测定槲皮素

在稀硫酸介质中,槲皮素对KBrO3氧化甲基红褪色反应有明显的催化作用。研究了该反应的最佳条件,建立了测定槲皮素的催化动力学光度法。当甲基红、硫酸、KBrO3的用量分别为0.70 mL、0.30 mL、0.25 mL,反应温度80℃,反应时间8 min时,该法测定槲皮素的线性范围为0.0~0.05 mg/L,检出限为0.002 mg/L。方法用于银杏叶和中草药鱼腥草中槲皮素含量的测定,结果满意。     

A new route for the functionalisation of wood through transesterification reactions

A novel transesterification reaction between acetylated maritime pine sapwood (Pinus pinaster Soland) and methyl benzoate (MB), in the presence of dibutyltin oxide (DBTO) as a catalyst, was performed. Reaction was confirmed by Fourier-transform infrared spectroscopy (FTIR) and ¹³C nuclear magnetic resonance cross-polarisation with magic-angle spinning (NMR CP MAS) analysis: signals corresponding to benzoylated wood were identified and, when transesterification was performed with ethyl trimethylsilylacetate (ETMSA), characteristic trimethylsilyl groups were detected. The acetyl/benzoyl exchange rate was found to increase with increasing amount of DBTO, temperature and reaction time and a concurrent deterioration of the woody material was evidenced.     

Analysis of sorption and bioavailability of different species of mercury on model soil components using XAS techniques and sensor bacteria

The present work studies the adsorption behaviour of mercury species on different soil components (montmorillonite, kaolinite and humic acid) spiked with CH₃HgCl and CH₃HgOH at different pH values, by using XAS techniques and bacterial mercury sensors in order to evaluate the availability of methyl mercury on soil components. The study details and discusses different aspects of the adsorption process, including sample preparation (with analysis of adsorbed methyl mercury by ICP-OES), the various adsorption conditions, and the characterization of spiked samples by XAS techniques performed at two synchrotron facilities (ESRF in Grenoble, France and HASYLAB in Hamburg, Germany), as well as bioavailability studies using mercury-specific sensor bacteria. Results show that XAS is a valuable qualitative technique that can be used to identify the bonding character of the Hg in mercury environment. The amount of methyl in mercury adsorbed to montmorillonite was pH-dependent while for all soil components studied, the bond character was not affected by pH. On the other hand, clays exhibited more ionic bonding character than humic acids did with methyl mercury. This interaction has a higher covalent character and so it is more stable for CH₃HgOH than for CH₃HgCl, due to the higher reactivity of the hydroxyl group arising from the possible formation of hydrogen bonds.The bioavailability of methyl mercury adsorbed to montmorillonite, kaolinite and humic acids was measured using recombinant luminescent sensor bacterium Escherichia coli MC1061 (pmerBR_BSluc). In case of contact exposure (suspension assays), the results showed that the bioavailability was higher than it was for exposure to particle-free extracts prepared from these suspensions. The highest bioavailability of methyl mercury was found in suspensions of montmorillonite (about 50% of the total amount), while the bioavailabilities of kaolinite and humic acids were five times lower (about 10%). The behaviour of methyl mercury in the presence of montmorillonite could be explained by the more ionic bonding character of this system, in contrast to the more covalent bonding character observed for humic acids. Thus, XAS techniques seem to provide promising tools for investigating the mechanisms behind the observed bioavailabilities of metals in various environmental matrices, an important topic in environmental toxicology.     

4-乙烯吡啶-丁烯酮共聚物与铑的顺二羰基配合物结构和性能研究

<正> 在铑催化剂的作用下,甲醇与一氧化碳经羰基化反应为乙酸和乙酸甲酯,是60年代发展起来的新工艺,但以往多是采用均相小分子铑催化剂,除我们的工作以外,迄今尚少见报道有采用以共聚物为配体的高分子铑催化剂的成功先例。     

Methyl torsional potentials of rotational isomers of m-methylanisole studied by spectral hole-burning spectroscopy

Laser-induced fluorescence (LIF) excitation spectra of m-methylanisole in a supersonic jet were measured. Two series of progressions were observed in the spectrum, originating at 36048 and 36115 cm⁻¹, which were successfully assigned to the transitions to the methyl internal rotational vibronic levels of the two isomers, i.e. cis and trans isomers, with the aid of hole-burning spectrum measurements and quantum-chemical calculations. The progression for the trans isomer was observed up to the 6a₁ band, while only the 3a₁ band in addition to the 0a₁ and 1e bands was observed for the cis isomer. This finding can be explained by the conformational change upon the electronic excitation; the 60° rotation of the methyl torsional angle takes place for the trans isomer but not for the cis isomer.     

KINETICS OF SUSPENDED EMULSION POLYMERIZATION OF METHYL METHACRYLATE

The kinetics of suspended emulsion polymerization of methyl methacrylate (MMA), in which water acted as the dispersed phase and the mixture of MMA and cyclohexane as the continuous phase, was investigated. It showed that the initial polymerization rate (Rp0) and steady-state polymerization rate (Rp) were proportional to the mass ratio between water and oil phase, and increased as the polymerization temperature, the potassium persulphate concentration ([I]) and the Tween20 emulsifier concentration ([S]) increased. The relationships between the polymerization rate and [I] and [S] were obtained as follows: Rp0 ∝ [I]0.73[S]0.32 and Rp ∝ [I]0.71[S]0.23. The above exponents were close to those obtained from normal MMA emulsion polymerization. It also showed that the average molecular weight of the resulting poly(methyl methacrylate) decreased as the polymerization temperature, [I] and [S] increased. Thus, MMA suspended emulsion polymerization could be considered as a combination of many miniature emulsion polymerizations proceeding in water drops and obeyed the classical kinetics of MMA emulsion polymerization.     

亚硝酸甲酯分子在440nm附近的激光光解

近年来亚硝酸甲酯分子（CHa0NO）的光解动力学研究十分活跃｛‘5］，主要集中在紫外激光的单光子解离的机理，光解过程的矢量相关性质和光解产物的态分布．CH30NO分子的解离能D。（CH30－NO）＝174kJ·mol‘，若单从能量上看，人＜689。的光就能使其解离，但人＞400urn的光解离研究还未见报导．＊H30＊0分子在人＞40onm的强激光场下是充电离还是先解离，是单光子解离还是多光子解离，以及通过哪个电子态解离都不清楚．时间飞行质谱不仅具有质量分辨率高、范围宽，而且响应快，因此适合做光解光电离过程初生态产物的探测．特别是时间飞…     

First total synthesis of isoquinolinone alkaloid marinamide and its methyl ester

The first total synthesis of isoquinolinone alkaloid marinamide 1 and its methyl ester 2 was described. The key steps involved a regioselective Frieclel-Crafts reaction of 1-benzyl-1H-pyrrole to form the intermediate 8.     

Characteristics of Heterophase Graft Copolymerizations

Abstract

Persulfate-initiated graft copolymerizations of glutaraldehyde crosslinked gelatin with acrylic acid, acrylamide, vinyl acetate, and methyl methacrylate in the aqueous phase were investigated. It was observed that percentage grafting, molecular weights of the grafts, and grafting efficiencies were greatly influenced by the nature of the monomers. Hydrophilic monomers gave a higher frequency of grafting but lower molecular weights. While the frequency of grafting with hydrophobic monomers was low, the molecular weights of the grafts were comparatively high. The results are explained in terms of microdomain kinetics, similar to those encountered in emulsion or suspension polymerizations.