乙酰丙酮氧钒催化氧化α-蒎烯一步转化成龙脑烯醛

以乙酰丙酮氧钒为催化剂,过氧化氢为氧化剂,研究了由α-蒎烯直接合成龙脑烯醛的反应。考察了溶剂、温度、催化剂用量、反应时间等因素对催化性能的影响。结果表明,乙酰丙酮氧钒与H2O2反应得到的高价态V5+是优良的氧化还原-Lewis酸双功能催化剂,易使α-蒎烯经氧化、2,3-环氧蒎烷异构得到龙脑烯醛。在n(H2O2):n(α-蒎烯):n(乙酰丙酮氧钒)=2.5:1:0.01、反应温度为20℃、丙酮为溶剂、反应2h条件下,α-蒎烯转化率为50.2%,龙脑烯醛的选择性达58.7%,反应6h后α-蒎烯转化率可达73.0%,主要产物龙脑烯醛和马鞭草烯酮的选择性分别为47.2%和13.2%。     

不饱和卡宾的单重态与三重态

对X2C=C:和X2C=C=C:(X=H,Li,F)进行了量子化学计算和研究,得到了不饱和卡宾单重态(^1A1)和三重态(^3B1)的几何构型及其相对稳定性随取代基X电负性变化的一般规律,结果表明,不饱和卡宾的基态都是单重态,第一激发态与基态的能量差ΔE(^1A1 - ^3B1)随X的电负性大小而变化,其值一般在60kcal.mol^-^1以内,累积烯基的大小对ΔE(^IA1-^3B1)的影响相对较小,^IA1和^3B1的平衡几何构型并不相同。     

射流式单重态氧发生器研究

单重态氧O2(a1△g)是迄今唯一能用纯化学反应高效产生的具有长寿命的亚稳激发态分子.为了考察提出的用两个O2(1△)能量汇集反应生成氧第二单重激发态O2(b1∑+g)以实现近可见短波长化学激光方案的现实性,设计和实验了一个氯流量为3～10 mmol/s的射流式单重态氧发生器(JSOG).考察了三种具有不同孔径和孔数目的喷头、氯气流量和脱水冷阱温度等对JSOG出口的O2(1△)浓度、O2(1△)分压、氯利用率及水蒸气含量的影响.发现用聚氯乙烯管作冷阱时,最佳冷阱介质温度为-140～-150℃,对此提出了O2(1△)表面脱活与脱水互相竞争的解释.在最佳条件下,可将O2(1△)气中水分压降低至4 Pa,这一结果是首次报导.     

γ-手性顺式的共轭烯醛与有机锂化合物的立体选择性反应

本文研究了在手性的顺式-γ-氨基-α,β-不饱和醛(7)与有机锂化合物的亲核加成反应中的1,4-不对称诱导效应.结果表明: 7与α-烷氧基乙烯醇锂类化合物的反应导致了优良的非对映立体选择性(d.e. : 60～90%), 而与烷基锂试剂的反应也给出了高度的立体选择性(d.e.: 74～86%). 这说明在这些反应中 , 存在着一种1,4-不对称诱导反应 .     

龙脑烯醛对9,10-二腈蒽荧光的猝灭作用

本文研究了在不同溶剂中龙脑烯醛对DCA荧光的猝灭作用, 通过稳态和瞬态荧光猝灭特性的比较, 溶剂极性对猝灭速度的影响, 自由能变化的估算及其与乙腈中双分子猝灭速率常数相关比较, 证明这是一个电子转移的动态猝灭过程。     

荧光黄素敏化胆固醇的单重态氧反应

黄素(Flavins)是一类典型的蛋白辅酶,其激发态参与许多重要的光生化过程。其中,黄素作为光敏剂可敏化一系列生物活性物质的光氧化,如氨基酸、蛋白质。DNA等,引起光致损伤作用。对于有重要生理作用的胆固醇(1),已发现血卟啉、玫瑰红(RB)、9,10-二氰蒽(DCA)等光敏剂敏化其单线态氧(~1O_2)反应,然而迄今对于核黄素(RF)敏化1的光氧化研     

荧光黄素敏化胆固醇的单重态氧反应

本文合成了无长链的荧光黄素, 在不同溶剂中研究了荧光黄素敏化胆固醇的光氧化反应, 实验观察到, 荧光黄素敏化胆固醇在乙腈, 吡啶和苯中光氧化, 形成胆固醇的5或7位过氧化氢和胆甾烯酮, 这些胆固醇氢过氧化基可用三苯基膦将其还原成相应的醇:6-胆甾烯-3β, 5α-二醇, 5-胆甾醇-3β, 7α-二醇, 5-胆甾烯-3β-醇-7酮.     

顺, 顺-1,5-环辛二烯的单重态氧反应及其产物的重排

本文报道用竹红菌甲素作光敏剂匹配高压钠灯光源, 对1,5-环辛二烯(1)进行单重态氧氧化反应, 高产率和立体选择性地得到顺-5,8-二(氢过氧基)-1,3-环辛二烯(7). 证明了7还原产物顺-5,8-二烃基-1,3-环辛二烯(8)热重排的产物是6-羟基-4-环辛烯酮(3). 而不是6-羟基-3-环辛烯酮(6). 并讨论了热重排过程的机理.     

烯烃光敏氧化反应机理——Ⅲ.丙烯与单重态氧Ene反应途径的解析

用MINDO/3法对丙烯与单重态氧Ene反应机理进行了详细研究。利用Fukui提出的IRC理论计算了整个反应途径。计算结果预期反应是分步进行的,且经由桥环过氧化物中间体。通过沿反应途径的分析,对反应过程中,反应物间的相互作用的情况,立体化学等进行了较为详细的讨论。     

RATES OF REACTION OF SINGLET OXYGEN WITH SULFIDES

Abstract—Reaction rate constants for the reaction of singlet oxygen with a series of 24 sulfides in chloroform have been measured by inhibition of the self-sensitized photooxidation of rubrene. The reaction rate constant is sensitive to steric effects, decreasing as the carbons α- to sulfur become more highly substituted. Addition of a methyl group to each of the carbons α- to sulfur decreases the rate constant by about a factor of 10. From a series of p - and m -substituted thioanisoles, a ρ of -1.67 ± 0.09 was found. A much better correlation was found with σ than with σ⁺ indicating there is no resonance interaction with the reaction center. Typical rate constants are: di- n -butyl sulfide, 2.3 × 10⁷ M ^-1 s^-1; CBZ-L-methionine methyl ester, 1.4 × 10⁷; di-s-butyl sulfide, 1.8 × 10⁶; di- t -butyl sulfide, 1.3 × 10⁵; and thioanisole, 2.3 × 10⁶.     

REACTION OF RETINOL AND RETINAL WITH SINGLET OXYGEN

Abstract— The rate constants for the reactions of all- trans retinol and retinal with singlet oxygen were measured in a variety of solvents of different polarities. The rate constants increased with increasing solvent dielectric constant, which suggests that a charge transfer mechanism plays a part in the reaction. Further, the rate constant of reaction of singlet oxygen with retinal is greater than that with retinol. Since retinal has a lower ionization potential than retinol, these relative rates also support the hypothesis of charge transfer involvement in the reaction.     

THEORETICAL STUDY ON THE 1,4-CYCLO-ADDITION REACTION BETWEEN SINGLET OXYGEN (~(1)O_(2)) AND IMIDAZOLE

Quantum chemical ab initio method has been used to study the cycloaddition reaction between singlet oxygen and imidazole theoretically. The intermediate product, an endoper-oxide, of which the structure has not yet been found experimentally was optimized by using energy gradient method. The transition state (TS) structure of this reaction was also located on the potential energy surface and characterized. From the structural features of the TS, e.g. the transition vector of the imaginary vibration mode, as well as the interaction of orbitals, it is realized that this cycloaddition is a synchronous concerted reaction. The activation barriers calculated are 69.5 kJ·mol (forward reaction) and 140.4 kJ·mol-1 (backward reaction) respectively (6-31G results).     

不同硫醚化合物和单线态氧反应能力的研究

本工作采用Young提出的方法,利用二苯基苯并呋喃及硫醚类化合物对单线态氧的竞争反应,通过荧光强度的比较,测定了一系列烷基和芳基硫醚化合物和单线态氧反应的速度常数。对所得结果,联系立体效应和电子诱导效应进行了讨论。     

THE REACTION OF SINGLET OXYGEN WITH PROTEINS, WITH SPECIAL REFERENCE TO CRYSTALLINS

Photosensitized oxidation of the eye lens proteins, the crystallins, is thought to lead to protein crosslinks and high molecular weight aggregates. Such protein modifications may be important factors in the formation of lens opacities or cataracts. We focus attention here on type 2 photo-oxidation involving the reaction of singlet oxygen (1O2) with crystallins and some "control" proteins. We find that: (1) trp residues are oxidized to N-formyl kynurenine and related products, but this in itself does not lead to the production of high molecular weight protein aggregates of the protein; (2) tyr residues react with 1O2 but we do not detect dihydroxyphenylalanine or bityrosine nor are protein crosslinks formed as a result; (3) oxidation of his residues appears necessary for high molecular weight protein covalent aggregates to form. Proteins devoid of his, e.g. melittin or bovine pancreatic trypsin inhibitor, do not form high molecular weight products upon reaction with 1O2. Prior reaction and blocking of his inhibits the crosslinking reactions. (4) The oxidized protein is seen to be more acidic than the parent and has an altered tertiary structure. (5) Among the crystallins, reactivity towards 1O2 varies in the order gamma greater than beta greater than alpha and also gamma A/E greater than gamma D greater than gamma B crystallin.     

CHEMICAL REACTION RATES OF AMINO ACIDS WITH SINGLET OXYGEN

Abstract— The chemical reactions of amino acids with singlet oxygen have been measured in D₂O solution where the singlet oxygen was generated directly by irradiation of the oxygen ³∑_g^-→¹δ_g+ lv electronic transaction with the 1.06 μm output of an Nd-Yag laser. Chemical reaction was measured as amino acid loss by an amino acid analyzer or by fluorescence in the cases of tryptophan and tyrosine.
The chemical rate constants, in units of 10⁷ M ^-1s^-1, are histidine 10, tryptophan 3, methionine 1.7, tyrosine 0.8 and alanine 0.2, In the cases of histidine, methionine and alanine the interaction appears to be entirely chemical, i.e. there is no evidence for physical quenching in addition to the chemical reaction. The histidine chemical reaction rate constant shows an increase with pD with a p K of 6.9.     

过渡金属络合物猝灭单重态氧能力的研究

研究了多种不同过渡金属络合物对单重态氧的猝灭问题。结果表明过渡金属络合物猝灭单重态氧的能力主要和络合物分子的几何构型有关。能形成平面四方形结构的络合物由于中心金属原子易于和¹O₂分子相接近因而具有强的猝灭¹O₂的能力,反之形成四面体形结构的络合物则猝灭能力减弱。     

ON THE REACTION OF SINGLET MOLECULAR OXYGEN WITH N-ALLYLTHIOUREA IN AQUEOUS SOLUTION

Abstract— Experiments on the photooxidation of N -allylthiourea, thiourea, and N-allylurea sensitized by the dye phenosafranine show that in N -allylthiourea the thiourea group is the site of singlet oxygen attack, while the allyl moiety neither reacts with nor quenches this metastable form of O₂ (in neutral aqueous solutions). Low concentrations of N^-₃ (a known quencher of singlet oxygen) strongly reduce the photooxidation of allylthiourea by a mechanism which apparently obeys simple competition kinetics. From these results the rate constant of the reaction between allylthiourea and singlet oxygen is obtained ( k = 4 × 10⁶ M ^-1 s^-1; pH = 7.1).     

咪唑与单线态氧(~1O_2)1,2-环加成反应的理论研究

采用较新的半经验分子轨道方法Austin Model 1(简称AM1方法),辅以Berny梯度优化方法,对单线态氧(~1O_2)与咪唑的1,2-环加成反应,进行了理论研究。计算获得实验尚未检测到的4,5-二氧环丁烷(4,5-dioxetane)的结构,并在反应势能面上找到单重态双自由基中间体及通过该中间体的两步反应的过渡态。通过对过渡态的结构特征、虚振动方向以及对反应过程的电荷分布情况、轨道相互作用等的分析,说明该反应是经由单重态双自由基中间体的分步反应。两步反应的活化势垒分别为39.2kJ·mol~(-1)和150.5kJ·mol~(-1)。