氮氧自由基的研究VII. 二元混合溶剂体系的溶剂效应

1-溴-4-氧戊烷的乙二醇缩酮(1)的格氏试剂, 与草酸二乙酯反应, 得2,6-二氧-6-乙二醇缩酮庚酸乙酯(2). 2     

硝基苯甲酸酯水解反应单电子转移机理的证据: ESR和自旋捕获的研究

对-硝基苯甲酸甲酯(1), 对-硝基苯甲酸正丁酯(2), 对-硝基苯甲酸叔丁酯(3), 对-硝基苯甲酸苄酯(4), 对-硝基苯甲酸苯酯(5), 对-硝基苯甲酸(对-硝基)苯酯(6), 间-硝基苯甲酸甲酯(7), 间-硝基苯甲酸乙酯(8), 间-硝基苯甲酸苯酯(9)和3,5-二硝基苯甲酸甲酯(10)与氢氧化钾在二甲亚砜中反应, 反应产物分别为相应的对-硝基苯甲酸和间-硝基苯甲酸。反应液用ESR检测, 得到1-10自由基负离子的ESR谱。用自旋捕获技术证明反应过程中有OH自由基生成, 自由基捕获剂亚硝基叔丁烷(TNB), 苯基叔丁基硝酮(PBN)和氧气使产物硝基苯甲酸的产率降低, 结果表明, 1-10与KOH与DMSO中反应存在单电子转移机理。     

亚磺化脱卤研究-连二亚硫酸钠引发的全氟烷基自由基对双键的加成

全氟碘代烷或溴代烷与亚硫酸盐或连二亚硫酸钠所发生的亚磺化脱卤反应表现自由基反应的特征,提供了用化学方法截捕全氟烷基自由基中间体的可能性:R_FX SO_2(?)[R_FX·SO_2](?)R_F· X~- SO_2.实验表明,在烯烃存在下,全氟碘代烷或溴代烷可以在亚磺化脱卤的同时生成较高产率的自由基加成产物.连二亚硫酸钠可作为全氟烷基自由基引发剂尚未见文献报道.本文报道了这一工作.全氟碘代烷在连二亚硫酸钠-碳酸氢钠的乙腈水溶液中,与1～1.5当量的烯烃在室温或稍高的温度下反应.即可获得相应的自由基加成产物.产率为50～80％:     

STYRENE POLYMERIZATION MEDIATED BY CYCLIC TRITHIOCARBONATE AS RAFT AGENT

The novel cyclic trithiocarbonate was synthesized by dialkylation of trithiocarbonate anion with 2,2＇- bis（bromomethyl）biphenyl in a two-phase system using an onium salt as a phase-transfer agent. Styrene polymerization was carried out in the presence of cyclic trithiocarbonate （CTTC）. CTTC undergoes ring opening-polymerization and the incorporated trithiocarbonate moiety derived from CTTC performs as the reversible addition-fragmentation chain transfer （RAFT） agent. Through this mechanism, multiblock polys-tyrenes containing various narrow polydispersity blocks can be prepared.     

唑类化合物的荧光猝灭及其与四氯化碳组合时所组成的光诱导引发体系

本工作对 唑类化合物在不同溶剂中的荧光被四氯化碳的猝灭问题进行了研究。发现其荧光猝灭的Stern-Volmer常数与所用溶剂的极性参数E~T(30)值间存在着线性关系, 这一结果表明: 这一猝灭过程具有明确的电子转移性质。在此工作基础上提出唑类化合物与四氯化碳所组成的体系可能是一种新的光诱导引发聚合体系。实验结果表明, 这一体系确能光引发单体化合物进行自由基聚合反应, 对该体系的光引发聚合机理作了初步的讨论。     

Effect of dissolved oxygen and lanthanide ions in solution on TiO2 photocatalytic oxidation of 2-propanol

The photocatalytic degradation of 2-propanol in D₂O solution under UV irradiation was investigated. The conversion yield from 2-propanol to acetone was studied by ¹H-NMR measurements. The study was carried out to elucidate effects of O₂ in the reaction medium and lanthanide ion modification on the TiO₂ surface. Under aerobic conditions, acetone formation was clearly increased in comparison with anaerobic conditions. On the modification of TiO₂ with lanthanide ion, the conversion yield decreased with the increase in the ionic radius. Yb³⁺ ion modification increased the acetone formation by approx. 5% in comparison with the unmodified case. Appreciably large effects of the counter ion in lanthanide salts were also observed. The role of OH^˙ radical formation in the first step of photocatalysis was emphasized in the experimental results.     

OH radical reactions with ethanolamines: formation of reducing as well as oxidizing radicals

The reaction of OH radicals with ethanolamine, diethanolamine and triethanolamine was studied at pH values below and above the pK_a values of these compounds. The rate constants were found to be lower for the protonated amines than those for their neutral forms. The OH radical reaction led to the formation of both oxidizing as well as reducing species, as observed by their reactions with methyl viologen and ascorbic acid. The oxidizing species formed by OH radical reaction at the amine site was not found to react with the parent molecules and thereby no secondary yield of reducing species was obtained as in the case of glycine (except in the case of triethanolamine at pH 9.2).     

氟烷基化和氟烷氧基化的研究2.在铜存在下氟烷基碘与芳烃的反应

氟烷基碘(RfI)在铜存在下与芳烃,C6H5Y(Y=烷基,OCH5,CF3,F,Cl,Br,I)在乙酐中反应得到相应的氟烷基化芳烃(RfC6H4Y)混合物,转化率和产率与所用铜粉量和芳烃上的电子密度有关,带有供电子基的芳烃转化率和产率都较高;反之则低,反应可能是自由基机理,氟烷基自由基能被环己烯和异丙苯所捕获。引发苯乙烯聚合生成含氟聚合物。芳环上的定位效应似乎也支持这一机理。若用DMSO为溶剂则可能是通过氟烷基铜中间体。     

Chemical intermediates scavengers in the therapy of allergic diseases

Although oxidative status has been related to several pathophysiologic processes, there is not a well established connection between antioxidant defense and allergy. An imbalance of reactive oxygen species is related to inflammation in allergic diseases. Antioxidant enzymes are involved in cell detoxification. This primary antioxidant defence system might work against allergic's symptoms. In this work, arguments in favour of the potential of free radical scavengers in antioxidant therapy for allergic patients are discussed.