A unique peroxide formation based on the Mn(III)-catalyzed aerobic oxidation

The autoxidation of a mixture of 1,1-diarylsubstituted alkenes 4 and 4-hydroxy-1H-quinolin-2-ones 5 in the presence of a catalytic amount of manganese(III) acetate dihydrate in air gave 3,3-bis(2-hydroperoxyethyl)-1H-quinoline-2,4-diones 6 in 31-91% yields together with [4.4.3]propellane-type cyclic peroxides 7 (10-34%). A similar aerobic oxidation of 3-substituted quinolinones 8 yielded cyclic peroxide derivatives 9 and/or 3-hydroperoxyethylated quinolinediones 10 depending on the substituent. The structures of the bis(hydroperoxide) 6 (R¹=Me, Ar=4-ClC₆H₄) and the [4.4.3]propellane 7 (R¹=Me, Ar=Ph) have been corroborated by X-ray crystallography.     

AT-column, a novel concentrating technique for large-volume injections in gas chromatography

Nowadays, large-volume injection is widely used for the GC determination of trace analytes, specifically to improve detectability. The most popular injectors for large-volume injections are the programmable temperature vaporisation (PTV) injector and the cold on-column (COC) injector, where each device has its own advantages and limitations. The novel AT-column concentrating technique combines features of two other injection techniques, loop-type large-volume and vapour overflow. AT-column injection is based on solvent evaporation in an empty liner with solvent vapour discharge via the split line. Little or no optimisation is required. The only relevant parameter is the injection temperature which can easily be calculated using the equation of Antoine. As an application, AT-column injection is combined with GC-MS for the trace-level determination of labile analytes and with GC-flame ionisation detection for the analysis of high molecular weight polymer additives. In summary, AT-column is an injection technique that combines the inertness of the COC, and the flexibility and robustness of the PTV large-volume technique.     

New analysis of the Coriolis-interacting v2 and v5 bands of CH3Br and CH3Br

The and fundamental bands of CH₃⁷⁹Br and CH₃⁸¹Br have been studied by Fourier transform infrared spectroscopy with an unapodized resolution of 0.004 cm⁻¹, corresponding to an improvement of one order of magnitude compared to previous studies. For both isotopomers, some 2427 (2239) lines were newly assigned for the parallel and the perpendicular bands and, in addition, 80 perturbation-allowed transitions were also added. The ground-state axial rotational constants A₀ were redetermined from allowed and perturbation-allowed infrared transitions observed in the v₂ and v₅ bands around the local crossing. The A₀ values obtained for both isotopomers are more accurate but fully compatible with those obtained previously. Using those results, and the variation of the rotational constants with vibration, new accurate equilibrium constants A_e and B_e have been also determined for CH₃⁷⁹Br and CH₃⁸¹Br. The excited states v₂=1 and v₅=1 are coupled by Coriolis-type interactions (Δl=±1,ΔK=±1) and (Δl=?1,ΔK=±2), while the l₅=±1 levels of v₅ interact also through “l(2,2)”-type interaction (Δl=±2,ΔK=±2). The Coriolis coupling term was determined to be for CH₃⁷⁹Br and for CH₃⁸¹Br. All interaction parameters have been determined with higher accuracy, compared to previous studies. A total of 4213 (3704) line positions with J?68(64) and K?16(11) including all available data was fitted using 20 (18) parameters with a root-mean-square deviation of 0.0007 (0.0006) cm⁻¹ for CH₃⁷⁹Br and CH₃⁸¹Br, respectively. Two different but equivalent forms of reduced Hamiltonians with two different sets of constrained constants were successfully applied according to Lobodenko's reduction [J. Mol. Spectrosc. 126 (1987) 159]. The ratio of the transition moments, |d₂/d₅|=1.65, and a positive sign of the Coriolis intensity perturbation d₂×ζ₂₅×d₅ were determined. Therefore, it has been possible to generate an accurate prediction of the whole spectrum between 1200 and 1650 cm⁻¹, including Q branches.     

Entrap-immobilization of biocatalysts on cellulose acetate-inorganic composite gel fiber using a gel formation ofcellulose acetate–metal (Ti, Zr) alkoxide

We developed a new entrap-immobilization method, using a gel formationof cellulose acetate and metal (Ti, Zr) alkoxide. Several biocatalysts(-galactosidase, -chymotrypsine, invertase, urease, lipase andSaccharomyces cereviciae) were successfullyentrap-immobilized on this composite gel fiber. The immobilization process wassimple and the resultant immobilized biocatalysts on the gel fiber were easy tohandle. It is considered that the biocatalysts are physically entrapped amongthe gel networks and distribute throughout the gel fiber. The gel fiber wasstable in phosphate buffer solution, electrolyte solution and organic solvent,because the gel formation was due to coordination interaction between celluloseand transition metal. Therefore, it can be applicable as a support for abiotransformation in various reaction media. We examined some enzyme reactionsand biotransformation using the immobilized biocatalysts on this gel fiber andevaluated this immobilization matrix in the reactions compared to the resultsobtained by the other immobilization method. The immobilized biocatalyst showedstable activity for repeated cycles and over a long period of time. Moreover,continuous reaction could be carried out in a column reactor packed with thisimmobilized biocatalyst.     

通过阴离子型和阳离子型活性链的偶合反应合成甲基丙烯酸甲酯-四氢呋喃嵌段共聚物

两亲性或双亲水性嵌段共聚物在许多领域有重要的应用 ,如用作乳化剂 [1] 、结晶改性剂 [2～ 4 ] 和金属胶体模板物 [5] 等 .借助于活性聚合反应 (阴离子型、阳离子型、基团转移和自由基等 ) ,通过相继加入单体的方式 ,制备出了大量的嵌段共聚物 [6～ 9] ,但这种方法有一定局限性 .对于四氢呋喃与各种 (甲基 )丙烯酸酯的两亲性共聚物的合成 ,由于前者只能进行阳离子型开环聚合 ,而后者则只能进行阴离子聚合和自由基聚合 ,因此难以通过上述方法制得嵌段共聚物 .本文报道了通过 PTHF阳离子型活性链与 PMMA阴离子型活性链偶合反应制备 PMMA…     

Microstructure of glycidylmethacrylate/vinyl acetate copolymers by two‐dimensional nuclear magnetic resonance spectroscopy

Glycidylmethacrylate/vinyl acetate copolymers were prepared by solution polymerization with benzene as a solvent and benzoyl peroxide as an initiator. Copolymer compositions were determined from ¹H NMR spectra, and comonomer reactivity ratios were determined by the Kelen–Tudos (KT) method and the nonlinear least‐squares error‐in‐variable method (EVM). The reactivity ratios obtained from KT and EVM were r_G = 37.4 ± 12.0 and r_V = 0.036 ± 0.019 and r_G = 35.2 and r_V = 0.03, respectively. Complete spectral assignments of ¹³C and ¹H NMR spectra were done with the help of distortionless enhancement by polarization transfer and two‐dimensional ¹³C–¹H heteronuclear single quantum coherence and total correlation spectroscopy. The methyl, methine, and methylene carbon resonance showed both stereochemical and compositional sensitivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4051–4060, 2001     

End‐functionalized copolymers prepared by the addition–fragmentation chain‐transfer method: Vinyl acetate/methacrylonitrile system

Copolymers of vinyl acetate and methacrylonitrile were prepared by free‐radical polymerization in the presence of the chain‐transfer agent (CTA) ethyl‐α‐ (t‐butanethiomethyl)acrylate. Molecular weight measurements showed that the chain‐transfer constants increased with the vinyl acetate content of the comonomer mixture, ranging from 0.42 for methacrylonitrile to 6.3 for the copolymerization of a vinyl acetate‐rich monomer mix (89/11). The bulk copolymer composition was not appreciably affected by the amount of CTA used in the copolymerization. The efficiency of the addition–fragmentation mechanism in producing specifically end‐functionalized copolymers was investigated with ¹H NMR spectroscopy. Spectral peaks consistent with all the expected end groups were observed for all comonomer feeds. Peaks consistent with other end groups were also observed, and these were particularly prominent for copolymers made with lower CTA concentrations. At the highest concentrations used, quantitative measurements of end‐group concentrations indicated that 70–80% of the end groups were those expected on the basis of the addition–fragmentation chain‐transfer mechanism. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2911–2919, 2001     

高选择性催化光度法测定痕量铜的研究

本文研究了在柠檬酸介质中 ,铜催化抗坏血酸还原甲基红的新指示反应及动力学条件 ,并测定了反应的活化能 ,建立了高选择性测定痕量铜的新方法。铜的测定线性范围为 0— 140 ng/ 2 5m L,检出限为 1.2 1× 10 -11g/ m L ,用于铝合金及人发样中铜的测定 ,结果令人满意。     

新型酸性离子液体[hmim]hso4中合成乙酸酯

制备了一种新型B rφnsted酸性离子液体[Hm im]HSO4,用于乙酸与醇的酯化反应,通过简单的相分离就可以实现产物乙酸酯与离子液体的分离。考察了温度、时间、物料配比、离子液体用量等因素对乙酸与正丁醇的反应的影响,得出反应的最佳条件为:反应温度110℃,反应时间2 h,酸醇摩尔比为2,酸性离子液体[Hm im]HSO4与醇的体积比为1,乙酸正丁酯的产率为97%。离子液体重复使用5次,乙酸正丁酯的产率均大于94%。利用核磁共振、红外和元素分析测试技术对酸性离子液体[Hm im]HSO4的结构进行了表征,是以一水合物的形式存在。测定了不同浓度[Hm im]HSO4水溶液的酸强度数据,结果表明,其酸性明显高于酸性离子液体[Hm im]CF3COO的酸性。