The Substituent Effects of tert-Butyl Radical Addition to 2-Substituted Allyl Chlorides

The relative rates for the addition reactions of tert-butyl radical to 2-substituted ally chlorides I have een determined. The correlation of log k/k₀, vs. σ_m gives a ρ mvalue of 3.59 with correlation coefficient of 0.930. When the substituent CH₂Cl is excluded, correlation coefficient raises to 0.990 and ρ value becomes 3.39. The large p value and the deviation of relative rate of substituent CH₂C1 are discussed.     

煤自燃初期的反应机理研究

从实验得到的可能引起煤自燃的8个活性基团入手，提出了一系列简单煤分子模型，利用密度泛函DFT/6-31G对其完成了几何优化，计算了包括反应焓变、吉布斯自由能和活化能等，从热力学和动力学角度分析了计算结果。基于理论计算获得了煤活性基团的活泼性次序，得出了煤自燃初期的反应机理主要是氧分子先进攻煤分子中的活性基团，产生活泼性很高的中间体，然后中间体进一步反应得到水或二氧化碳及其他反应产物，计算结果与实验基本符合。     

全氟烷基磺酸酯C-O键断裂的同面SN2反应

用密度泛函理论研究了CF3SO3CF2CF3 F^-的碳氧键断裂反应的机理。首先，用DFT方法优化了反应物、中间体、过渡态、产物的平衡构型，分析了碳氧键断裂反应的势能面变化，发现在SN2反应机理中，除了S-O断裂SN2反应外，引起C-O键断裂的同面进攻也是一个可能的反应途径。理论计算表明，最终反应的产物是受热力学控制的，S-O键的断裂绝对地优于C-O的断裂。因此，C-O断裂的同面机理虽然是可能的，但却难以被实验观察到，本文还讨论了端基-CF3在同面SN2反应中的邻位效应，以及基组对这个效应的影响。     

Etude DFT du mécanisme des réactions de cycloaddition dipolaire-1,3 de la C,N-diphénylnitrone avec des dipolarophiles fluorés de type éthylénique et acétylénique

Structures and energetics of reactants, transition states and cycloadducts of cycloadditions of nitrone with three-fluorinated dipolarophiles have been investigated with the density functional theory method B3LYP/6-31G^*. Analysis of the results on the different reaction pathways shows that the reaction takes place along a concerted mechanism and proceeds more or less synchronously. The FMO analysis shows a strong HOMO_dipole-LUMO_{dipolarophile} interaction as the principal reason for the reactivity in these 1,3-dipolar cycloaddition reactions. Regioselectivity of the products of the reaction is predicted reliably by our calculations, the results provide a good prediction of the relatives rates observed experimentally as the dipolarophiles are varied.     

非晶SiO2纳米灯笼的制备和表征

在1000 ℃用活性炭把二氧化锡粉末还原成单质锡, 锡作为催化剂, 硅片作为硅源同时作为收集衬底, 在硅片上制备出了非晶SiO2纳米灯笼. 灯笼的一端连在硅片上, 另一端为一个锡球, 中间是一些圆弧状的SiO2纳米线把两端相连. 纳米灯笼具有良好的对称性. 利用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED) 和HRTEM自带的能谱分析仪(EDS)对样品的表面形貌、微观结构和成分进行了分析研究. 结果表明, 灯笼中SiO2纳米线为非晶态, 结点是晶态锡, 结点表面覆盖一层非晶态的硅的氧化物. 结合实验条件对纳米灯笼的生长机理进行了讨论, 提出了纳米灯笼生长的一个模型.     

叠氮二乙基铝合成及其相关反应的研究

在芳烃溶剂中用氯化二乙基铝和叠氮化钠反应合成了叠氮化二乙基铝(DEAA),其产率高达87%,比文献值高出17%。在正己烷中没有合成出DEAA,在含30%四氢呋喃(THF)的正己烷中合成出DEAA·THF配合物。在芳烃溶剂中,随着苯环上甲基数目的增加,DEAA的收率增加。测定了氯化二乙基铝、氯化二乙基铝的正己烷溶液、氯化二乙基铝的甲苯溶液的 ²⁷Al NMR谱。由 ²⁷Al NMR谱数 据确定了氯化二乙基铝在甲苯中解离平衡式,计算了氯化二乙基铝在甲苯中解离平衡的热力学数据。用DEAA与苯甲酸甲酯直接合成了苯甲酰叠氮,并表征了其结构。这是一个新反应,至今无文献报导。用实验证明了在正己烷溶液中,用氯化二乙基铝、叠氮化钠与苯甲酸甲酯合成苯甲酰叠氮,没有经过氯化二乙基铝和叠氮化钠反应生成中间体DEAA的这一步。依据实验事实建立了上述三种反应的反应机理。     

Study of the Behavior of an EC Mechanism Using Cyclic and Derivative Chronopotentiometric Techniques with Spherical Electrodes

The theory for an EC mechanism in chronopotentiometric techniques – reversal chronopotentiometry, cyclic chronopotentiometry and reciprocal derivative chronopotentiometry – is developed. The equations of this article are valid for spherical electrodes of any size and present a compact and easy‐to‐manage form. Methods for determining kinetic parameters of the chemical reaction are proposed and the influence of the electrode radius is discussed. We conclude that large errors in the determination of these parameters are committed if electrode sphericity is neglected. Reciprocal derivative chronopotentiometry has been applied in its traditional form (dt/dE vs. E), and in a more recently proposed modality consisting of plotting dt^1/2/dE vs. E. These techniques are very convenient for studying an EC mechanism since the response is obtained in the form of peaks which are quantitatively related to the kinetic parameters of the chemical reaction. A comparison of the chronopotentiometric methods analyzed leads us to conclude that working curves based on the dt^1/2/dE vs. E curves are more suitable to obtain accurate values of the rate constants of the chemical reaction.     

稳态双曲流场中液/液混合的粘性液滴哑铃分散模型

通过对稳态双曲流场中液／液混合体系分散相液滴所受分散作用力的分析，建立了粘性液滴的哑铃分散模型．趋于将两粘性液滴分开的分散作用力与粘度比、流场类型和强度、液滴半径、哑铃取向和尺寸有关．该模型解释了流场类型与分散作用的关系．流场类型对液滴的分散具有很大影响，在纯应变拉伸流场中分散作用力是简单剪切流场中的两倍，因而对于液滴的分散，拉伸流场较简单剪切流场更有效，这与以前的实验结论符合．当体系粘度比趋于无穷大时本模型转化为刚性哑铃分散模型     

弹性体共混改性聚丙烯的增韧机理

阐述了以聚丙烯（ＰＰ）／高密度聚乙烯（ＨＤＰＥ）为复合基体，苯乙烯－丁二烯－苯乙烯（ＳＢＳ）为增韧剂经三元共混所得的性能优异的一类新材料．从三个层次（形貌结构转变、宏观力学响应和裂尖过程区演化）系统地探讨了其增韧机理．结果表明由形貌结构控制和对早期体膨胀变形抑制可造成裂尖平面应变区的超钝化从而达到增韧．     

Enhanced Kinetic Isotope Effect of the Phosphate-Catalyzed Proton Exchange in N,N'-Dimethylurea

The concerted mechanism of phosphate-catalyzed proton exchange in N,N'-dimethylurea has been studied. Kinetic data were measured using the technigue of NMR line-shape analysis. A significant kinetic isotope effect was observed for the concerted proton transfer in N,N'-dimethylurea and is attributed to the tunnelling effect.