Styrene–substituted‐styrene copolymerization using diphenylzinc–metallocene–methylaluminoxane systems

Homopolymerization of disubstituted styrenes (2,4‐ and 2,5‐dimethylstyrene) and trisubstituted styrene (2,4,6‐trimethylstyrene) and their copolymerization with styrene were carried out using diphenylzinc–metallocene–methylaluminoxane initiator systems for metallocene (n‐BuCp)₂TiCl₂ and for half‐metallocene CpTiCl₃. The studied comonomers were found to be less reactive than p‐tertbutylstyrene, p‐methylstyrene and styrene. The results indicate that, even though the methyl group has I+ inductive effect, di‐ and tri‐methylstyrenes are reluctant to undergo either homopolymerization or copolymerization. This behavior suggests that the reactivity is regulated not only by the inductive effect of the alkyl group but also by the steric impediment caused by the crowding of the substituents on the benzene ring. Copyright © 2006 Society of Chemical Industry     

Preparation of substituted carbonyl compounds by catalytic dehydrogenation of substituted alcohols

Possibilities for the preparation of substituted ketones by catalytic dehydrogenation of corresponding secondary alcohols were explored using a ZnO–Cr₂O₃ catalyst at 370–400°C. It was found that addition of about 1 wt% of sodium to the catalyst increases the yield of the ketone because the competitive dehydration of the alcohol is suppressed. Further improvement of the process was achieved by adding 20 wt% of water to the alcohol feed, which inhibited catalyst deactivation. Preparative experiments were conducted and 1-methoxy-2-propanone, 1-methoxy-2-butanone, 1-phenoxy-2-propanone and 2-methoxy-1-cyclohexanone were obtained.     

Monomeric and dimeric phenolic acids released from cell walls of grasses by sequential treatment with sodium hydroxide

Cell walls of tall fescue Festuca arundinacea Schreb and coastal bermudagrass Cynodon dactylon L Pers were treated sequentially with increasing concentrations of sodium hydroxide (0·1 M to 10 M) to release monomeric and dimeric phenolic acids. (E)-p-Coumaric and (E)-ferulic acids were the major monomers released. Most of the saponifiable feruloyl groups (97% for tall fescue, 89% for coastal bermudagrass) were released with 0·1 M sodium hydroxide. Much lower proportions of saponifiable p-coumaroyl groups (67% for tall fescue, 46% for coastal bermudagrass) were released with this treatment. The major dimers from both grasses were 4,4′-dihydroxy-α-truxillic, 4,4′-dihydroxy-3-methoxy-α-truxillic, and 4,4′-dihydroxy-3,3′-dimethoxy-α-truxillic acids, and were mainly released with 0·1 M sodium hydroxide. Similar proportions of the monomers and dimers were released from the cell walls of each grass with the 0·1 M and 1 M sodium hydroxide sequential treatments. It is probable that most if not all of the monomers and dimers released by the sequential alkali treatments were originally ester linked to the cell walls. If it is assumed that the cell wall bound dimers are formed photochemically from p-coumaroyl and feruloyl groups during plant growth, it is calculated that, for the two grasses, between 12 and 17% of the monomer units were converted to dimers.     

二苯硫脲类化合物的粉末倍频性能研究

本文设计合成了十二种二取代二苯硫脲类化合物，粉末测试表明其中三种化合物具有倍频效应，最大者为ＫＤＰ的６倍，初步讨论了这类化合物的倍频性能与分子结构的关系。     

二氯二茂钛与取代苯甲醛肟的反应

二氯二茂钛与取代苯甲醛肟钠在二氯甲烷中反应，生成二茂钛单肟衍生物Ｃｐ２ＴｉＣｌ（ＯＮ＝ＣＨＡｒ），其中Ａｒ为邻硝基苯基，间硝基苯基，对硝基苯基，邻氯苯基，间氯苯基，３，４－二氯苯基，间甲氧基苯基，对甲氧基苯基，２，４－二甲氧基苯基和３，４－亚甲基二氧苯基。所有这些新化合物在干燥空气中稳定，对潮湿空气敏感。经元素分析外，核磁氢谱表征，确认了其结构。     

Variations in Cytotoxicity During Ozonation of Substituted Aromatics

The cytotoxicity test, using BGM cells and a colorimetric protein assay (Lowry, 1951) was a more sensitive modification of those described by Christian (1973) and Elias, et al. (1978). The cytotoxicity varied during ozonation, reaching a maximum after 50%90% degradation of the initial compound; aniline solution, 6.5x10³ M, showed a maximum cytotoxicity at 90% degradation after 60 min of ozonation, which decreased to 0% after 180 min 0₃. Ozonated nitro– and chloro–cresol solutions showed similar patterns. The variations in cytotoxicity seem to be related to the formation of intermediate oxidation products. The preliminary results suggest that this type of test, being both simple and fast, would be useful in toxicological screening of wastewater.     

溴甲基取代的香豆素的合成

介绍了合成的7-溴甲基香豆素等6个溴甲基取代的香豆素化合物,这些化合物的合成文献少有报道。     

N-(取代苯基)马来海松酸酰亚胺的合成及表征

松香树脂酸衍生物具有广泛的生物活性。该文以松香为原料,在催化剂对甲基苯磺酸作用下与马来酸酐经Diels-Alder反应制得马来海松酸;马来海松酸与取代苯胺采用一步法在N,N-二甲基甲酰胺(DMF)溶剂中,于155℃反应4 h,合成了8个具有潜在生物活性的N-(取代苯基)马来海松酸酰亚胺化合物,产率为42.5%~84.8%;对产物结构进行了IR、1HNMR、13CNMR光谱表征确认。     

2008年公开的新农药品种

概述了2008年公开的11个新农药品种,其中杀菌剂2个、杀虫剂3个、除草剂6个。     

Ca含量对 Ca-La-Co 联合取代M型锶铁氧体的影响

本文采用固相球磨法制备M型锶铁氧体,研究了Ca含量对Ca-La-Co联合取代M型锶铁氧体的影响。采用X射线衍射、场发射扫描电镜、永磁测量仪对M型铁氧体的物相、晶胞结构、微观形貌和磁性能进行了表征。Ca_²⁺部分取代Sr_²⁺会造成晶胞c轴收缩,Ca取代量x’’≤0.2 at%时,得到单一的磁铅石相,Ca取代量x’’≥0.3 at%时,开始出现α-Fe₂O₃相。Ca_²⁺与SrO等形成低共熔物,加速晶粒c轴方向上的生长,促进六角片状结构的形成,Ca取代量xx’’=0.2 at%时,粒径在1.0 μm左右,分布均匀,随着取代量的增加,出现晶粒异常长大的现象。Ca取代量的增加会降低磁体的饱和磁化强度M_s、剩磁B_r,但会提高矫顽力H_cj,当Ca取代量x’’≤0.2 at%时,样品的剩磁略微下降,而矫顽力却急剧上升。