异戊二烯-甲基丙烯酸甲酯的阴离子嵌段共聚合

在四氢呋喃(THF)与环己烷的混合溶剂中,以正丁基锂(n-BuLi)为引发剂,采用具有较大空间位阻和特定电荷环境的P配合物为添加剂,实现了异戊二烯(Ip)和甲基丙烯酸甲酯(MMA)的阴离子嵌段共聚。分别采用GPC、1H-NMR对聚合物的结构进行了分析表征。结果表明：随着THF与环己烷体积比的增大,单体的转化率呈现下降的趋势;同时空间位阻较大的P配合物的加入,堵塞了正、负离子对之间的部分通道,有效地抑制了MMA段聚合副反应的发生,在易于工业化的0 ℃之下成功合成了分子量分布窄(1.21)的聚异戊二烯聚甲基丙烯酸甲酯嵌段共聚物(PI-b-PMMA),并且共聚物中PI嵌段以3,4结构链节为主。     

Determination of ethane, pentane and isoprene in exhaled air--effects of breath-holding, flow rate and purified air

Aim: Exhaled ethane, pentane and isoprene have been proposed as biomarkers of oxidative stress. The objectives were to explore whether ethane, pentane and isoprene are produced within the airways and to explore the effect of different sampling parameters on analyte concentrations. Methods: The flow dependency of the analyte concentrations, the concentrations in dead‐space and alveolar air after breath‐holding and the influence of inhaling purified air on analyte concentrations were investigated. The analytical method involved thermal desorption from sorbent tubes and gas chromatography. The studied group comprised 13 subjects with clinically stable asthma and 14 healthy controls. Results: Ethane concentrations decreased slightly, but significantly, at higher flow rates in subjects with asthma (P = 0.0063) but not in healthy controls. Pentane levels were increased at higher flow rates both in healthy and asthmatic subjects (P = 0.022 and 0.0063 respectively). Isoprene levels were increased at higher flow rates, but only significantly in healthy subjects (P = 0.0034). After breath‐holding, no significant changes in ethane levels were observed. Pentane and isoprene levels increased significantly after 20 s of breath‐holding. Inhalation of purified air before exhalation resulted in a substantial decrease in ethane levels, a moderate decrease in pentane levels and an increase in isoprene levels. Conclusion: The major fractions of exhaled ethane, pentane and isoprene seem to be of systemic origin. There was, however, a tendency for ethane to be flow rate dependent in asthmatic subjects, although to a very limited extent, suggesting that small amounts of ethane may be formed in the airways.     

Alkyl Zinc Chlorides as New Initiators for the Polymerization and Copolymerization of Isobutene

Mixtures of RZnCl and tBuCl (R = Et) initiate the polymerization of isobutene in the temperature range of (?35)—(+35) °C. The order of addition of the reagents is important for effective polymerization. Increasing the solubility of the zinc reagent (R = n‐octyl) and use of cumyl chloride as co‐initiator provides a system that is active from (?90)—(+35) °C. The molecular weights show a remarkably small temperature dependence, E_DP = ?3.3 kJ · mol^?1, compared to E_DP = ?23 kJ · mol^?1 in classical systems (AlCl₃, EtAlCl₂). The molecular weights increase with decrease in zinc concentration and are consistently higher for n‐octyl zinc chloride, as expected for a bulkier, less coordinating counteranion. The polymerizations are not retarded by isoprene addition; homopolymers and copolymers show essentially identical conversions and molecular weights.

     

马来酸酐接枝稀土异戊橡胶接枝率的测试方法

以马来酸酐(MAH)和稀土异戊橡胶(IR)聚合液为主要原料,采用溶液接枝改性反应制备了马来酸酐接枝稀土异戊橡胶(IR-g-MAH)。以IR-g MAH接枝率的测试方法为研究对象,对比直接滴定法和返滴法,并进一步优化直接滴定法的测试条件。实验结果表明,直接滴定法测试的结果准确度高、重复性好,且测试过程简单。其较优的测试条件为：水解试剂为乙醇,样品用量为0.2~0.5 g,KOH-乙醇标准溶液浓度为0.02~0.06 mol/L。     

Elective haemodialysis increases exhaled isoprene.

BACKGROUND: Uraemic odour is a characteristic feature of patients with end-stage renal disease (ESRD). However, few investigations have been carried out into the composition of exhaled air in ESRD patients undergoing haemodialysis (HD). Increases of exhaled isoprene levels by a factor of up to 2.7 following HD have been reported. METHODS: We attempted to confirm these findings in 50 patients undergoing HD using haemophan (n=23) or polysulphone (n=27) dialysis membranes. Parallel evaluation of ambient air, calorie intake, medication and haemodynamic variables was performed. Samples were analysed using proton transfer reaction-mass spectrometry (PTR-MS). RESULTS: Significant changes in breath isoprene concentration were observed when comparing patients before [39.14+/-14.96 parts per billion (ppbv)] and after (63.54+/-27.59 ppbv) dialysis (P<0.001). The quotient of values before and after dialysis was 1.84 (SD 1.41). No significant differences in isoprene kinetics were found between the use of haemophan and polysulphone membranes. No significant correlations were observed between isoprene quotients and variations in blood pressure during HD, calorie intake, ingestion of lipid-lowering drugs or serum lipid levels. CONCLUSIONS: Isoprene concentration was higher in the exhaled air of patients after HD as compared with values before HD. Large interindividual variability existed in isoprene kinetics. Oxidative stress appears to be an unlikely cause for this rise. An alternative hypothesis is an influence of respiratory variables on isoprene exhalation based upon Henry's law constant. We therefore propose to perform online monitoring of isoprene exhalation by PTR-MS during the HD session to investigate the possible influence of respiratory variables.     

High‐Molecular‐Weight Isobutene–Isoprene Copolymers Containing Unusually High Isoprene Content

Summary: The 1:2 adduct of the highly electrophilic borane B(C₆F₅)₃ with n‐decanoic (stearic) acid, [n‐C₁₇H₃₅CO₂H][B(C₆F₅)₃]₂ exhibits sufficiently enhanced acidity that it is an excellent initiator for the carbocationic copolymerization of isobutene with isoprene in methylene chloride and methyl chloride. High conversions to gel free, high‐molecular‐weight copolymers containing up to 15 wt.‐% isoprene are readily obtained, consistent with the anion [n‐C₁₇H₃₅CO₂{BC₆F₅)₃}₂]^? being very weakly coordinating. Thus chain transfer following IP incorporation into the growing polymeric chain, which normally results in low average molecular weights, is much less of a factor here.

The acidic 1:2 adduct of B(C₆F₅)₃ with n‐decanoic acid, [n‐C₁₇H₃₅CO₂H][B(C₆F₅)₃]₂, as an initiator for the carbocationic copolymerization of isobutene with isoprene.     

苦瓜子非皂苷类成分研究

目的: 研究苦瓜Momordica charantia子中的化学成分。 方法: 利用各种色谱方法进行分离纯化,根据理化性质和NMR,MS等波谱技术鉴定化合物的结构。 结果: 从苦瓜子乙醇提取物中分离鉴定了10个化合物,包括5个生物碱,2个异戊二烯,2个木脂素,1个胆甾醇,分别为24β-乙基-5α-胆甾-7-反式-22E,25(27)-三烯-3β-羟基-3-O-β-D-吡喃葡萄糖苷(1),1-甲基-1,2,3,4-四氢-β-咔啉-3-羧酸 (MTCA)(2),烟酰胺(3),尿嘧啶(uracil, 4),(6S,7E,9S)-6,9,10-trihydroxy-4,7-megastigmadien-3-one (5),表松脂酚-4,4'-二-O-β-D-吡喃吡喃葡萄糖苷 (6),lectin (7),长寿花糖苷(8),蚕豆苷(9),6-(2,3-二羟基-4-羟甲基-四氢呋喃)-环戊烯[c]吡咯-1,3-二醇(10)。 结论: 化合物2,3,5,6,7,9,10均为首次从苦瓜子中分离得到。     

阴离子聚合理论新见解应用于聚异戊二烯结构控制的研究

以正丁基锂(nBuLi)为引发剂,环己烷为溶剂,在40～70 ℃下进行异戊二烯(Ip)阴离子聚合的研究。考察了极性调节剂四氢呋喃(THF),结构调节剂P配合物对异戊二烯聚合特点及聚异戊二烯(PI)结构的影响。分别采用GPC、 1HNMR以及7LiNMR对P配合物、引发剂以及聚合物的结构进行了分析。结果表明,当聚合温度远高于聚异戊二烯的玻璃化温度时,转化率时间曲线仅出现加速拐点而不会出现转化率停滞平台。用先前提出的缔合引发剂引发聚合并崩解,以及通过控制离子对之间距离可实现对聚异戊二烯结构进行控制新见解,解释了以往在阴离子聚合中难以解释的问题。当把P配合物加入到以nBuLi为引发剂的聚合体系中,由于锂被P配合物和nBuLi共享,从而强化了两者之间的结合。而P配合物较大的空间体积封堵了部分的离子对通道,使得聚异戊二烯中3,4结构链节显著增加至50%以上。     

鼠尾藻的化学成分研究

 目的 研究鼠尾藻的化学成分。方法 采用正相及反相硅胶柱色谱、Sephadex LH-20凝胶柱色谱、半制备高效液相色谱等方法进行分离纯化,根据理化性质及波谱学数据鉴定化合物的结构。结果 从鼠尾藻乙醇提取物中,分离鉴定了15个化合物,其中9个异戊二烯类化合物,分别为黑麦草内酯（1）,异黑麦草内酯（2）,loliolide acetate（3）,蚱蜢酮（4）,apo-9′-fucoxanthinone（5）,3α-hydroxy-5,6-epoxy-7-megastigmen-9-one（6）,deacetylate-apo-13′-fucoxanthinone（7）,apo-13′-fucoxanthinone（8）,(R)-(-)-3-羟基-β-紫罗兰酮（9）,6个其他类型的化合物,sargassum ketone（10）,2-heptenoic acid-4,4-dihydroxy-2,3-dimethyl-γ-lactone（11）,(R)-2-hydroxy-3-phenylpropanamide（12）,脱氧核糖胸腺嘧啶（13）,岩藻甾醇（14）,甘油脂肪酸酯（15）。结论 deacetylate-apo-13′-fucoxanthinone (7) 为新化合物,化合物3,5,6,8,9,15为首次从该属植物中分离得到。     

Isoprene interferes with the attraction of bodyguards by herbaceous plants

Isoprene is the most abundant volatile compound emitted by vegetation. It influences air chemistry and is part of plant defense against abiotic stresses. However, whether isoprene influences biotic interactions between plants and other organisms has not been investigated to date. Here we show a new effect of isoprene, namely its influence on interactions between plants and insects. Herbivory induces the release of plant volatiles that attract the herbivore's enemies, such as parasitic wasps, as a kind of bodyguard. We used transgenic isoprene-emitting Arabidopsis plants in behavioral, chemical, and electrophysiological studies to investigate the effects of isoprene on ecological interactions in 2 tritrophic systems. We demonstrate that isoprene is perceived by the chemoreceptors of the parasitic wasp Diadegma semiclausum and interferes with the attraction of this parasitic wasp to volatiles from herbivore-infested plants. We verified this repellent effect on D. semiclausum female wasps by adding external isoprene to the volatile blend of wild-type plants. In contrast, the antennae of the parasitic wasp Cotesia rubecula do not perceive isoprene and the behavior of this wasp was not altered by isoprene emission. In addition, the performance of the 2 examined lepidopteran herbivores (Pieris rapae and Plutella xylostella) was not affected by isoprene emission. Therefore, attraction of parasitic wasps to host-infested herbaceous plants in the neighborhood of high isoprene emitters, such as poplar or willow, may be hampered by the isoprene emission that repels plant bodyguards.