Some kinetics aspects of chlorine-solids reactions(
洗必泰对克雷伯氏肺炎杆菌生物被膜分解作用的影响
洗必泰对克雷伯氏肺炎杆菌生物被膜分解作用的影响户登，苏显中，房婷中国矿业大学化工学院，江苏徐州（221008）E-mail: dengwho@摘要：目的研究药物洗必泰对革兰氏阴性菌克雷伯肺炎杆菌(Klebsiella pneumoniae ) 生物被膜形成的影响，为生物被膜病的治疗提供理论依据。
方法本研究通过克雷伯氏肺炎杆菌在聚苯乙烯棒上培养形成生物被膜；结晶紫染色鉴定生物被膜；洗必泰治疗；扫描电镜观察生物被膜变化。
结果洗必泰对克雷伯肺炎杆菌形成的生物被膜有一定分解作用。
洗必泰有可能被广泛地用作抗生物被膜药剂。
关键词：克雷伯肺炎杆菌；生物被膜；洗必泰；聚苯乙烯棒中图分类号：Q734，Q935细菌生物被膜( bacterial biofilm, BBF )是指细菌粘附于固体或有机腔道表面，形成微菌落，并分泌细胞外多糖蛋白复合物将自身包裹其中而形成的具有一定空间结构的膜状物[1]，其成分包括近95~99％水[1,4]，2~5％细菌以及2％的胞外多糖( EPS )[4]。
据估计约65％的细菌感染是由生物被膜引起的[2,3]。
革兰氏阴性菌克雷伯肺炎杆菌( Klebsiella pneumoniae，KP )是引发植入导管和其他医疗器械感染的最常见的细菌之一,可引发尿道感染、下呼吸道、血液、消化道、外科伤口、颅内、皮肤软组织等多个部位感染，是医院感染及免疫缺陷者感染的重要病原菌。
它可在细胞外产生粘质，使其能够在生物材料表面形成粘着的生物被膜。
这层生物被膜可使其内部菌体对抗生素和宿主自身免疫具有很强的抗性，很难根除。
洗必泰(chlorhexidine,CHX ,学名醋酸氯己啶)以其低毒性、低腐蚀性、低刺激性和极强的抑菌能力而被广泛应用于皮肤、粘液、物体表面以及口腔消毒。
已有研究表明洗必泰对口腔内多种细菌产生的生物被膜具有抑制作用[7]。
本实验通过观察克雷伯氏肺炎杆菌在聚苯乙烯棒表面形成生物被膜和洗必泰对该菌生物被膜的治疗效果,目的在于为医疗器械的消毒和生物被膜病的治疗提供实验依据。
过氧化氢-硫代硫酸钠-亚硫酸钠-高氯酸反应体系的脉冲波
论 文第50卷 第9期 2005年5月 869过氧化氢-硫代硫酸钠-亚硫酸钠-高氯酸反应体系的脉冲波安英莉 白云峰 高庆宇*(中国矿业大学化工学院, 徐州 221008. * 联系人, E-mail: gaoqy@ )摘要 实验研究发现过氧化氢-硫代硫酸盐-亚硫酸盐-高氯酸(H 2O 2-S 2O 32−-SO 32−-H +)反应在凝胶扩散介质中呈现出化学脉冲波时空动力学行为, 脉冲波在特定初始浓度组成中存在特定的最大半径和最大寿命, 它们随着硫代硫酸盐初始浓度的增加先增大而后减小. 过氧化氢初始浓度增大, 脉冲波中心的pH 值会出现二次下降, 甲基红存在条件下体系呈现为带有红心的脉冲波. 另外, 脉冲波在演化过程中, 出现有趣的回缩现象. 并结合相关机理对脉冲波动力学进行了讨论.关键词 非线性化学 自催化 脉冲波化学波是非线性化学动力学研究的一个重要领域, 它的研究对聚合物合成、催化动力学、燃烧学和生命科学中自组织等领域的发展有着重要意义[1~3]. 含硫化合物氧化还原反应体系中硫元素复杂价态变化过程常伴随着pH 变化, 可以用来设计pH 振荡器和化学波[4~8], Rábai 和Hanazaki [7]发现H 2O 2-S 2O 32−-SO 32−-H +体系在连续流动反应器(CSTR)中可以呈现pH 简单振荡, 倍周期振荡和混沌等丰富的非线性动力学现象. 他们还在研究H 2O 2-S 2O 32−-SO 32−-H +振荡体系的温度补偿作用时发现, 振荡周期在25.5~33.5℃之间几乎保持不变[9], 这个发现说明化学体系中的自组织现象与生物体系中的生物钟现象之间存在着重要的联系[10]. 但是, 有关该反应的时空动力学行为的研究却未见报道. 我们认为闭系复杂的pH 振荡行为可能在相应的反应-扩散(R-D)体系中表现为脉冲波等时空动力学行为. 本文从实验方面研究了H 2O 2-S 2O 32−-SO 32−-H +体系在凝胶扩散介质中的时空动力学行为及其影响因素, 并对实验中出现的化学脉冲波进行了讨论.1 实验实验所用试剂Agar(Fluka)为生化试剂, 其余均为分析纯. 所用溶液当日配制, 其中HClO 4用高温干燥的无水碳酸钠标定, 硫代硫酸钠和亚硫酸钠用碘量法进行标定, 过氧化氢在酸性介质中由高锰酸钾标定. 用Millipore-Q 处理的去离子水(18.2 M Ω·cm)配制溶液. 封闭搅拌反应器外接精密恒温槽((20.0±0.1)℃, Polyscience, USA), 体积为40 mL. 以Hg|Hg 2SO 4|K 2SO 4为参比电极, 231型pH 电极信号通过Powerlab/4sp (ADInstruments, Australia)采集并转入 IBM PC 等待处理. 闭系实验试剂加入顺序为HClO 4→SO 32−→S 2O 32−→H 2O 2. 凝胶介质中的实验在自制的凝胶反应器(直径12.5 cm)中进行, 体系由精密恒温槽控温. 凝胶采用Agar 水溶液制备而成, 实验时首先配置0.4%的Agar 水溶液(称取0.4 g Agar 溶解在100 g 70℃水中), 然后在水浴槽中冷却至45℃, 并保持此温度使之处于液体状态备用. 依次取一定量的高纯水、高氯酸、亚硫酸钠、硫代硫酸盐溶液和Agar 水溶液混合后(均相反应扩散实验再加入过氧化氢溶液混合), 加入几滴0.1%甲基红乙醇溶液, 再混合后倒入凝胶反应器中, 冷却2 h 充分凝化, 控制胶层厚度为1.5 mm, 体系中含0.25%的Agar. 实验时用精密移液管(Ultra, England)移取一定浓度过氧化氢垂直滴于反应器中心. 产生的化学波通过视频采集卡(DVC, Singapore)把CCD 系统(WV EP460, Japan)的影像输入电脑.2 结果及讨论实验发现过氧化氢-硫代硫酸钠-亚硫酸钠-高氯酸反应扩散体系可以产生化学单脉冲波. 在含有亚硫酸盐、硫代硫酸盐、高氯酸溶液和少量甲基红溶液的Agar 凝胶薄层中, 由于质子平衡因素亚硫酸根离子结合质子主要以亚硫酸氢根离子的形式存在, 初始体系呈碱性显黄色. 当向中心加入5 µL 过氧化氢溶液(1 mol/L), 如图1(a)中心逐渐变红(pH<4.2), 而后红色区域逐渐向外扩展, 中心却由红色恢复到原来的黄色(pH>6.4)并随着红色区域的扩展而扩展, 红色区域逐渐发展为环状从而形成二维脉冲波, 当圆环达到最大直径时脉冲波停止扩张, 然后圆环收缩直到消失, 整个体系恢复为黄色.理论上如果一个化学反应扩散体系不仅含有自催第50卷 第9期 2005年5月论 文图1(a) 脉冲波的演化, 图片拍摄时间依次为200, 2000, 10000, 12000, 16000和20000 s. (b) 脉冲波半径随时间的变化. [H +]0=0.001 mol/L, [S 2O 32−]0= 0.0025 mol/L, [SO 32−]0 = 0.0015 mol/L, gel% = 0.25%, 5 µL 1 mol/L H 2O 2化反应步骤能够产生前沿波, 而且含有抑制剂参与的消耗自催化剂过程, 合适的自催化剂消耗过程在一定程度上使前沿波经过的区域又恢复到原来的状态, 即波的前面和后面处于同一状态, 而波峰处于另一种状态, 便产生脉冲波. 在过氧化氢-硫代硫酸钠-亚硫酸钠-高氯酸反应体系中, 过氧化氢与亚硫酸氢根离子之间的反应, 具有质子自催化性质[11], 反应方程如下:H 2O 2+HSO 3−⎯⎯→SO 42−+H ++H 2O (M1) 同时体系中还存在过氧化氢与硫代硫酸盐之间的质子负反馈反应M2,H 2O 2+2S 2O 32−⎯⎯→S 4O 62−+2OH − (M2) 由图1(b)可以看出, 脉冲波在演化过程中, 其传播速度随时间的增加而减慢, 当脉冲波的半径扩展到一定程度时, 停止向外传播. 而后发生有趣的回缩现象. 分析其原因如下: 在闭系反应扩散过程中, 过氧化氢随脉冲波半径的增大逐渐扩散且被消耗引起浓度递减,因此过氧化氢向外扩散速度逐渐减慢, 化学波传播速度减慢, 既而如同生命体系断了养分供应就会停止生长脉冲波达到最大半径时停止向外传播. 另一方面, 脉冲波将体系分为两个反应物浓度明显不同的两个区域, 在脉冲波的后方因发生自催化反应, 亚硫酸氢根离子被消耗, 脉冲波的前方, 由于未发生反应, 亚硫酸氢根离子处于高浓度状态. 明显的浓度差使环外亚硫酸氢根离子向环内扩散, 与缓慢扩散过来的过氧化氢自催化反应, 同时硫代硫酸根离子也由于浓度差的原因向环内扩散, 并与剩余过氧化氢发生反应提供质子负反馈, 从而使脉冲波反向传播, 出现脉冲波向环内收缩现象. 随着各反应物的消耗, 红色圆心变浅, 最终消失而使整个体系恢复为黄色.脉冲波在演化过程中存在最大传播半径, 并且因其会出现回缩和消失而具有一定寿命. 图2显示实验研究发现固定其他反应条件, [S 2O 32−]0对脉冲波的最大传播半径、寿命有重要影响. 脉冲波最大传播半径变化曲线1和脉冲波的寿命变化曲线2随着硫代硫酸盐的初始浓度的增大均先上升而后下降. 另外, 实验中还发现随硫代硫酸盐初始浓度的升高脉冲波的平均环宽明显变窄.图2 [S 2O 32−]0对脉冲波的影响1, 脉冲波最大半径变化曲线; 2, 脉冲波寿命变化曲线. [H +]0=0.001mol/L; [SO 32−]0 = 0.0015 mol/L; gel% = 0.25%; 5 µL 1mol/L H 2O 2硫代硫酸盐初始浓度对脉冲波影响的复杂性源自过氧化氢氧化硫代硫酸盐的两种不同计量方程的氧化反应方式. 一般认为在过氧化氢氧化硫代硫酸盐的过程中存在中间产物HOS 2O 3−[12], 1996年Kurin- Csorgei 等人[13]提出H 2O 2-S 2O 32−-H +体系的反应机理模型[8]中将M2反应分解为以下三个步骤: S 2O 32−+H 2O 2⎯⎯→HOS 2O 3−+ OH − (M2-1) S 2O 32−+HOS 2O 3−⎯⎯→S 4O 62−+OH − (M2-2)H 2O 2+S 4O 62−⎯⎯→2HOS 2O 3− (M2-3) M2-1, M2-2和M2-3构成一个质子负反馈反应方870 论 文第50卷 第9期 2005年5月式, 硫代硫酸盐完全被过氧化氢氧化最终生成SO 42−:H 2O 2+ HOS 2O 3−⎯⎯→2HSO 3−+H + (M3′)M2-1, M3′和M1反应叠加成M3:4 H 2O 2+S 2O 32−⎯⎯→2SO 42−+2H + (M3) 相比较M2为质子负反馈反应, M3则是质子生成的反应计量学方程式. 当H 2O 2过量时, 随着硫代硫酸盐起始浓度的增加有更多的质子生成, 造成脉冲波的半径和寿命升高. 继续增加硫代硫酸盐起始浓度, 反应计量学从M3逐渐转化为优势的M2, 减弱脉冲波的前进, 结果改变硫代硫酸盐起始浓度出现脉冲波的半径和寿命的极值. 过氧化氢初始浓度对脉冲波的影响主要表现在, 当H 2O 2的浓度增大时脉冲波的环中心会再度变为红色而形成带有红心的单脉冲化学波如图3(a). 这与封闭搅拌体系的实验得出的单峰振荡后出现的pH 二次下降(图3(b))相对应, 第二次下降源自中间物连四硫酸根离子与过氧化氢的进一步反应, 当H 2O 2浓度足够高时由于中心区域H 2O 2相对过量很多, 即在波环中心的硫代硫酸盐氧化中间物连四硫酸根离子与过氧化氢进行质子自催化反应(M2-3, M3′和M1), 引起pH 二次下降, 从而在脉冲波后产生前沿波. 同不带红心的脉冲波一样, 带红心的脉冲波在停止扩张一段时间后, 也会发生收缩现象.图3(a) 带红心脉冲波的形成. [S 2O 32−]0 = 0.0025 mol/L, [H +]0 = 0.001 mol/L, [SO 32−]0 = 0.0015 mol/L, 10 µL 1.5 mol/L H 2O 2. (b) H 2O 2-S 2O 32−- SO 32−-H +体系pH 曲线, 其中, [S 2O 32−]0 = 0.006 mol/L, [H +]0 = 0.001mol/L, [H 2O 2]0 = 0.1 mol/L, [SO 32−]0 = 0.006 mol/L另外, 值得一提的是脉冲波的形成需要一定的初始浓度条件: (1) [S 2O 32−]0至少要大于[H +]0. 当硫代硫酸根离子完全按照方程式M2进行反应时, 产生等摩尔的OH −, 前沿波经过区域的H +的浓度大致等于[H +]0, 故当[S 2O 32−]0至少要大于[H +]0才有可能提供足够强度的负反馈使前沿波经过区域的恢复至黄色. 实验中当[H +]0为0.001 mol/L 时, [S 2O 32−]0 > 0.00125 mol/L, 出现脉冲波; [S 2O 32−]0<0.00125 mol/L 时, 只出现红色的前沿波而没有脉冲波, 即红色前沿波经过的地方没有恢复到黄色状态. [S 2O 32−]0的最低值略大于[H +]0, 这是因为Agar 凝胶呈酸性额外增大了[H +]0. (2) [SO 32−]0要大于[H +]0使体系初始状态成黄色, 否则从颜色的变化上观察不到脉冲波.3 结论 过氧化氢-亚硫酸氢钠-硫代硫酸钠-高氯酸反应体系包含质子正负反馈反应, 在闭系搅拌反应器中表现为时间序列大幅度的pH 单峰或准振荡, 在二维凝胶介质中, 对应的pH 振荡过程在空间展现为脉冲波. 硫代硫酸盐对脉冲波性质的影响表现为非单调形式, 它与过氧化氢的反应存在着两种方式: 质子正反馈方式(M1)和质子负反馈方式(M2). 封闭体系的正负反馈反应与脉冲波波前和波尾的动力学存在着对映关系, 作为一个新的研究体系, 其二维化学波及其收缩现象有助于进一步理解自然界相类似的复杂性动力学. 致谢 本工作为国家自然科学基金(批准号: 20103010)和教育部优秀青年教师资助项目.参 考 文 献 1 Epstein I R, Pojman J. Introduction to nonlinear chemical dynamics: oscillations, waves, patterns and chaos. New York: Oxford UniversityPress, 19982 Winfree A. The Geometry of Biological Time. Second ed. New York: Springer, 20013 Bub G , Shrier A, Glass L. Spiral wave generation in heterogeneous ex-citable media. Phys Rev Lett, 2002, 88(5): 058101-1~058101-44Orbán M, Epstein I. Chemical oscillators in group VIA: the Cu(Ⅱ)- catalyzed reaction between hydrogen peroxide and thiosulfate Ion. J Am Chem Soc, 1987, 109(1): 101~106[DOI]5Kovács K, Rábai G. Large amplitude pH oscillations in the hydrogen peroxide-dithionite reaction in a flow reactor. J Phys Chem A, 2001, 105(40): 9183~9187[DOI]6Gaoffre F, Labrot V , Boissonade J, et al. Reaction-diffusion patterns of the chlorite-tetrathionate system in a conical geometry. J Phys Chem A, 2003, 107(22): 4452~4456[DOI]7Rábai G , Hanazaki I. Chaotic pH oscillations in the hydrogen perox-ide-thiosulfate-sulfite flow system. J Phys Chem A, 1999, 103(36): 7268~7273[DOI]8Gao Q, wang J. pH oscillations and complex reaction dynamics in the non-buffered chlorite-thiourea reaction. Chem Phys Lett, 2004, 391(4-6): 349~353[DOI]9Rabai G , Hanazaki I. Temperature compensation in the oscillatory hy-drogen peroxide-thiosulfate-sulfite flow system. Chem Commun, 1999, (19): 1965~196610Hanazaki I, Ishibashi N, Mori H, et al. Bifurcation structure in the hy-drogen peroxide-sulfite system. J Phys Chem A, 2000, 104(32): 7695~7699[DOI]11 Rabai G, Orban M, Epstein I. Design of pH-regulated oscillators. Acc Chem Res, 1990, 23(8): 258~263[DOI]12 Schiller J E. A new reaction of cyanide with peroxide and thiosulfate at pH 7-9. Inorganic Chemistry, 1987, 26(6): 948~950[DOI]13Kurin-Csorgei K, Orbán M, Rábai G, et al. Model for the oscillatory re-action between hydrogen peroxide and thiosulfate catalysed by copper(Ⅱ) ions. J Chem Soc Faraday Trans, 1996, 92(16): 2851~2855[DOI](2004-09-09收稿, 2004-12-28收修改稿) 871。
化学基础英文3_chemical_reactivity化学反应性
3-2 Reaction Classification
If you scan any organic textbook you will encounter a very large, often intimidating, number of reactions. These are the "tools" of a chemist, and to use these tools effectively, we must organize them in a sensible manner and look for patterns of reactivity that permit us make plausible predictions. Most of these reactions occur at special sites of reactivity known as functional groups, and these constitute an organizational scheme that helps us catalog and remember reactions.
Ultimately, the best way to achieve proficiency in organic chemistry is to understand how reactions take place, and to recognize the various factors that influence their course.
A rearrangement reaction generates an isomer, and again the number of bonds normally does not change.
离子色谱法测定水中氯酸盐
参考文献
沟等，如果发生事故废水排放，废水依靠地面高度位差流入 四周的地沟，然后通过泵送至事故废水收集池，再送入污水 站处理。为了防止废水通过雨水管网排放污染环境，在各生 产装置界区雨水排放总出口窨井处设雨水集水井，并且在集 水井出口设置切断阀门，发生污染事故后可切断集水井出口
[1] 陈军海，徐红霞，刘海亚 . 环境事故应急池管理研究 [J]. 环境科学 与管理，2015，40（2）：1–4.
生产装置区事故
其他场所事故水
车间地沟或围堰
所在区域围堰或地沟
事故水 厂内雨水管网
事故池
21–23. [5] 李彦文 . 化工生产企业应急事故水池的一次建设实践 [J]. 能源与环
境，2018（4）：90–92. [6] 樊 旭 . 焦 化 工 程 事 故 池 的 设 计 [J]. 煤 炭 与 化 工，2018，41（5）：
[2] 化工建设项目环境保护工程设计标准 ：GB/T 50483–2019[S]. [3] 事故状态下水体污染的预防和控制规范 ：Q/SY 08190–2019[S]. [4] 徐挺挺 . 论石化企业事故池容量确定方法 [J]. 宁波化工，2013（1）：
阀门，将事故污水截留在厂区内，以截断事故情况下通过雨 水系统排入外环境的途径。在雨水集水井安装废水输送泵， 将废水送事故收集池或相应的处理装置处理。
应采取下列处置措施 ： 1）能够回用的应回用。 2）不符合回用要求，但符合排放标准的废水，可直接排放。 3）对不符合排放标准，但符合污水处理站进水要求的废
水，应限流进入污水处理站进行处理。
4 结束语 对于《化工建设项目环境保护工程设计标准》和《事故
状态下水体污染的预防和控制规范》中的应急事故水池容积 设计方法进行分析，两者均有各自的适用范围，在事故水量、 消防水量、物料转移和储存等方面存在不同。在具体项目中，
给排水消毒技术讲义 Disinfection 英文
9
Cryptosporidium analysis
Techniques for sampling and analysis are complicated and time consuming - requires filtration of large volumes of water (100 -1000 litres) - followed by several stages of elution, isolation and concentration of the oocysts - identification and enumeration by immuno-fluorescent microscopy. Initial testing does not provide information on whether the oocysts are viable and therefore capable of causing disease - requires further testing. Identification of the species sub-type can be helpful in tracing the source of contamination - this requires much additional work. For these reasons there is no specific standard for Cryptosporidium in the EU Drinking Water Directive or the national regulations
污水中溶解性有机氮类化合物的氯化反应特性及其消毒副产物生成潜能
环 境 科 学 ENVIRONMENTAL SCIENCE
Vol． 34 ， No． 8 Aug． ， 2013
污水中溶解性有机氮类化合物的氯化反应特性及其消 毒副产物生成潜能
1 2 1 3 1 1 1 刘冰 ， 于鑫 ， 余国忠 ， 古励 ， 赵承美 ， 翟慧敏 ， 李清飞
中图分类号： X52 ； X703. 1 文献标识码： A 文章编号： 0250-3301 （ 2013 ） 08-3156-08
Chlorination Characteristic and Disinfection Byproduct Formation Potential of Dissolved Organic Nitrogen Compounds in Municipal Wastewater
+ N 分 别 为 2. 47 荧光光谱对与氯反应前后的水样进行表征 ． 结 果 表 明， 城 市 污 水 厂 二 级 出 水 中 DON、DOC、UV254 和 NH4 -
mg · L －1、 14. 45 mg · L －1、 15. 88 m － 1 和 5. 42 mg · L －1， DOC 与 DON 比值［ m （ DOC ） / m （ DON） ］为 5. 85 mg · mg － 1 ， SUVA 为 1. 09 L · （m · mg）
． 但是， 出水 DON 中已经确定的含氮化的出水普遍采用加氯消毒的方式， 程会与有机物发生加成或取代作用等而生成对人体 ［5 ］ 有危害的 卤 代 和 非 卤 代 物 质， 即 DBPs ． 污 水 中 DON 类化合物在氯化消毒过程中， 其母体部分碳链 和官能团结构被加成、氧化、取代和重构， 形成含 硝 基 （ —NO2 ） 、 腈 基 （ —C 帒N ） 、 酰 胺 基 （ —CO—NH2 ） 和亚硝胺（ —N—N O ） 的卤代和非 卤 代 化 合 物，即 含 氮 消 毒 副 产 物 （ nitrogenous NDBPs ） ， disinfection byproducts， 与 之 相 应 的 NDBPs 分别包括卤化硝基甲烷 （ HNMs ） 、卤化乙腈 （ HANs） 、卤代乙酰胺 （ HAcAms ） 和非卤代的亚硝 ［6 ～ 8 ］ ． 同时， 胺类 （ Nitrosamines ） 城市污水处理厂二 级出水经消毒处理后如排入河流或湖泊， 可能直接 ［9 ］ ． Lee 或间接地作为下游饮用水源 等 对美国 28 家 饮用水厂中常规工艺对 DON 处理结果进行了统计， 结果表明 DON 的去除率仅 20% 左右． 因此， 城市污 DBPs 的研究是十 水处理厂二级出水中 DON 及 N分必要的． 本实验以城市污水处理厂二级出水为研究对 + N 等浓度水平 象， 在调查污水中 DON、DOC 和 NH4 的基础上， 对相关含氮氯化消毒副产物的生成潜能 同时结合分子量切割、傅里叶红外光 进行了评价， 谱（ FTIR） 和三维荧光光谱分析手段， 对氯化反应前
IBX氧化的机理研究
Published:February 16,2011ARTICLE/JACSThe Nature of the Catalytically Active Species in Olefin Dioxygenation with PhI(OAc)2:Metal or Proton?Yan-Biao Kang †and Lutz H.Gade*,†,‡†Catalysis Research Laboratory (CaRLa),Im Neuenheimer Feld 584,69120Heidelberg,Germany ‡Anorganisch-Chemisches Institut,Universit €a t Heidelberg,Im Neuenheimer Feld 270,69120Heidelberg,GermanybSupporting Information ABSTRACT:Evidence for the protiocatalytic nature of the diacetoxylation of alkenes using PhI(OAc)2as oxidant is presented.Systematic studies into the catalytic activity in the presence of proton-trapping and metal-complexing agents indicate that protons act as catalysts in the ing tri flic acid as catalyst,the selectivity and reaction rate of the conversion is similar or superior to most e fficient metal-based catalysts.Metal cations,such as Pd(II)and Cu(II),may interact with the oxidant in the initiation phase of the catalytic transformation;however,1equiv of strong acid is produced in the first cycle which then functions as the active catalyst.Based on a kinetic study as well as in situ mass spectrometry,a mechanistic cycle for the proton-catalyzed reaction,which is consistent with all experimental data presented in this work,is proposed.’INTRODUCTIONThere are several classical methods for the dioxygenation of alkenes that are still widely used in organic synthesis.These include two-step-reactions,such as the Woodward -Prevost reaction (pathway a,Scheme 1)1and the epoxidation followed by ring-opening (pathway c).2Both operate under relatively mild reaction conditions,even though the former is not a catalytic reaction.The one-step dioxygenation of alkenes catalyzed by OsO 4,3along with its asymmetric version,the Sharpless dihydroxylation,4are among the most widely used methods but involve an expensive and highly toxic catalyst (pathway b).The development of new e fficient catalytic dioxygenation meth-ods for alkenes has therefore remained a challenge.In recent years,there has been considerable interest in the development of alternative dihydroxylation protocols involving other metal catalysts.With the emergence of palladium(IV)chemistry in catalysis,5-13the dioxygenation of alkenes has been reinvestigated using Pd-or Cu-catalysts instead of the very toxic osmium.14Very recently,Dong et al.reported a Pd(OTf)2-catalyzed diacetoxylation of alkenes using PhI(OAc)215-18as oxidant.14a In this case,a cationic palladium complex with electron-rich diphosphines as ligands as well as the use of the anionic tri flato ligand were claimed to be essential for the reaction because,for instance,Pd(OAc)2itself was found to be inert.Although a Pd IV intermediate was invoked in the proposed catalytic cycle for this reaction,no detailed mechanistic investiga-tions were carried out.Related diacetoxylations were also ob-served as leading to undesired side products in Pd-catalyzedamino acetoxylations.6h It is notable that Chai and co-workers reported the same type of reaction for a copper(II)catalyst,in which the tri flate counterion also proved to be essential.In this case,all other copper salts tested,such as Cu(OAc)2and CuCl 2,were catalytically inert.14b Claims for a mechanism involving Cu III intermediates were based on in situ high resolution mass spectrometry.However,closer inspection of the data revealed signi ficant discrepancies between the expected and observed data,along with the observation of many other unassigned ion peaks,which make this interpretationquestionable.Scheme 1.Approaches for Dioxygenation or Diacetoxylation ofAlkenesReceived:December 2,2010The nature of the active catalyst in both the palladium-and copper-catalyzed diacetoxylations thus remains to be resolved.However,this point is essential for the further development of the method as a synthetic tool.In view of this uncertainty,we set out to further explore the mechanism of dioxygenation reaction of alkenes using PhI(OAc)2as oxidant and to identify the active catalyst(s).In this work,we provide new mechanistic insight into this reaction,both its intramolecular and intermolecular version,the catalytically active species involved,and the key role that tri flate may play as a weakly coordinating anionic ligand or counterion.’RESULTS AND DISCUSSIONScreening of Metal Salts for Catalytic Activity in the Intramolecular Diacetoxylation of Alkenes.As indicated,both palladium and copper salts have been reported as catalysts for the diacetoxylation of alkenes.It was thus essential to establish to which degree these two metals were necessary,or in fact,whether a metal-based catalyst in general was an indis-pensible prerequisite.The results of the screening of metal salts and complexes for the intramolecular diacetoxylation repre-sented in eq 1are summarized in Table 1.Besides Cu(OTf)2and Pd(OTf)2,other transition metal Lewis acids such as Ni(ClO 4)2and Co(BF 4)2were also found to be efficient catalysts,while the corresponding salts with more basic or strongly coordinating counterions,such as Pd(OAc)2,Cu-(OAc)2,CuCl 2,and NiCl 2,proved to be inactive.Surprisingly,we found that alkali earth metal salts also displayed catalytic activity (entries 20-26).For instance,using 0.1mol %of extremely pure Ba(ClO 4)2,a full conversion of 2a was obtained within 20min (entry 26).ICP-OES analysis of the calcium and barium salts established that traces of copper andpalladium in these salts,if present,were well below the 1and 5ppm level,respectively (Supporting Information).Since at these concentrations none of the transition metal salts was found to be active,“hidden ”catalysis by these metals may be ruled out.A similar behavior was observed for the intermolecular diacetox-ylation of styrene with PhI(OAc)2(eq 2).For comparison the conversion curves for the Pd-,Ca-,and TfOH-catalyzed reaction are displayed in Figure 1,using 5mol %of HOTf and [(R )-BINAP-Pd(H 2O)2(OTf)2]as well as 11mol %of Ca(OTf)2.First of all,we note that the Ca(OTf)2catalysis occurs with much lower activity and that [(R )-BINAP-Pd(H 2O)2(OTf)2]and HOTf display very similar activities at the same catalyst loading.However,the metal-catalyzed reactions are characterized by sigmoidal conversion curves which may indicate the (reversible)generation of the catalytically active species in the initial stages of the reaction and its gradual disappearance near the end.Table 1.Catalyst Screening of Metal Salts and Brønsted Acids aentry catalyst loading (mol %)%conv b entry catalyst loading (mol %)%conv b 1Ni(ClO 4)236H 2O110017d Pd(OAc)2162Ni(ClO 4)236H 2O 0.19418d Cu(OAc)2123Ni(ClO 4)236H 2O 0.058819d CuCl 2174Ni(ClO 4)236H 2O 0.011020g Ca(ClO 4)234H 2O 10995Ni(ClO 4)236H 2O 0.001 3.821g Ca(OTf)210996Ni(ClO 4)236H 2O 0.0001122dCaCl 21027cNi(Cl)23glyme 5623Mg(OTf)2101008d Cu(OTf)20.59924Mg(ClO 4)236H 2O101009e Co(BF 4)2109925d ,g Ba(ClO 4)2(99.999%)110010f ,d Pd(L)(H 2O)2(OTf)219926d ,g Ba(ClO 4)2(99.999%)0.12311f ,d Pd(L)(H 2O)2(OTf)20.59627acetic acid (>99.99%)175712f ,d Pd(L)(H 2O)2(OTf)20.259528g HClO 4(99.999%)0.19313f ,d Pd(L)(H 2O)2(OTf)20.19529g tri flic acid (99%)0.18814f ,d Pd(L)(H 2O)2(OTf)20.034330tri fluoroacetic acid 0.1215f ,d Pd(L)(H 2O)2(OTf)20.01331HCl0.1216f ,dPd(L)(H 2O)2(OTf)20.0012324-CF 3-benzoic acid0.12aReaction conditions:1(0.13)mmol;2a (0.1mmol);CH 2Cl 2(1mL).3a forms after a rearrangement of phenyl group in the reaction (see ref 19for details).b Determined by 600MHz 1H NMR.c Refers to NiCl 2-CH 3OCH 2CH 2OCH 3.d Reaction time:20min.e Co(BF 4)236H 2O was used.f (R )-BINAP-Pd(H 2O)2(OTf)2was used.g ICP-OES measurements show the trace amount of metals:Cu <1ppm and Pd<5ppm;see Supporting Information for details.Figure 1.The comparison of the conversion curves for the Pd-,Ca-,and TfOH-catalyzed diacetoxylation of styrene.Note that no in flection point was seen for the tri flic acid-catalyzed transformation.It is clear from these results that high valent Pd IV or Cu III are not necessarily involved in the catalytic diacetoxylation with PhI(OAc)2.Remarkably,several Brønsted acids proved to cata-lyze the reaction,albeit under very speci fic conditions.We note that in a previous study of a noncatalytic version of this reaction 19no conversion had been observed in the presence of a dilute acidic solution.In our investigations of the reaction,very low activity and conversion was found in the presence of AcOH (175mol %,entry 27),while 0.1mol %of HClO 4or HOTf gave rise to complete conversion (entries 28and 29).Again,ICP-OES analyses of the acids established levels of Cu and Pd of below 1and 5ppm,thus again ruling out hidden metal catalysis.However,under the same reaction conditions,other strong acids only induced very low conversions (entries 30-32),thus raising the question as to the speci ficity of the observed acid catalysis.Both metal salts as well as tri flic and perchloric acid thus appear to catalyze the diacetoxylation.The nature of the actual catalytically active species in these reactions therefore remains to be resolved and,in particular,whether there might be a common underlying principle.In Figure 2the conversion curves of the [(R )-BINAP-Pd(H 2O)2(OTf)2]-catalyzed diacetoxylation of styrene with PhI(OAc)2as oxidant (eq 2)are compared for di fferent Pd catalyst loadings (and with HOTf).At all catalyst loadings,the sigmoidal characteristics of the conversion curves,already noticed in Figure 1,are found.At the point of in flection,the activity of the Pd catalyst is essentially the same as that of HOTf at an equal catalyst loading (in this case:5mol %).It appears that for the Pd catalyst,the active species,which we propose to be the “excess ”proton,is being formed initially,an aspect that will be further discussed below.Proton-Trapping Study.To investigate the possible catalytic role of protons in this dioxygenation reaction,proton-trapping agents were added to the reaction in eq 1for various catalysts.As shown in Table 2,the intramolecular reference reaction catalyzed by HOTf was effectively inhibited by either 5mol %of proton sponge (N ,N ,N 0,N 0-tetramethyl-1,8-naphthalenediamine)or 100mol %of Bu 4NOAc (entries 2and 4).On the other hand,EDTA as neutral tetracarboxylic acid,which was added as a metal complexation agent,had no inhibitive e ffect on the Cu(OTf)2,Ba(ClO 4)2,and (R )-BINAP-Pd(H 2O)2-(OTf)2-catalyzed dioxygenation (entries 9,15,and 21),while the ligand EDTA itself (in its neutral,protonated form)was inactive (entry 6).This indicated that the scavenging of the metal by a complexone did not impede the activity of the system.On theother hand,both proton-sponge and Bu 4NOAc were e fficient inhibitors for the Cu(OTf)2-,Pd(OTf)2-,and Ba(ClO 4)2-cata-lyzed reaction (entries 10-13,16-19,22-24)in the presence or absence of EDTA.Analogous proton-trapping experiments were carried out for the intermolecular dioxygenation of styrene with iodobenzene diacetate (eq 2).This reaction proceeded smoothly in the presence of 5mol %of HOTf to give 97%conversion at room temperature within 6h (Table 3,entry 1).When proton sponge or Bu 4NOAc were added at the outset,no conversion was observed even after 24h.In the cases of Cu(OTf)2and Pd(OTf)2,the proton traps also e fficiently suppressed the reaction,and Cu(OAc)2as well as Pd(OAc)2,containing the basic acetate as counteranion,were found to be inactive as noted in previous studies.14In Figure 3the conversion curves of the [(R )-BINAP-Pd-(H 2O)2(OTf)2]-catalyzed diacetoxylation of styrene with or without an equivalent amount of Bu 4N(OAc)are displayed.We note that 1mol of added base essentially quenches 1mol of Pd catalyst.This would be consistent with a mechanistic scenario,in which the catalytically active proton is generated in a first reaction step of the metal complex with the oxygenation agent PhI(OAc)2(vide infra)and is trapped if additional acetate is present.Substrate Scope of the Metal Catalysts and the Proton.The obervations made in the catalyst screening suggested the possibility of theproton alone acting as a catalytically activeFigure 2.The comparison of the catalytic conversion curves for the diacetoxylation of styrene with PhI(OAc)2as oxidant,obtained for di fferent amounts of [(R )-BINAP-Pd(H 2O)2(OTf)2]and compared to 5%of TfOH as catalyst.Table 2.Proton-Trapping Study on the Intramolecular Reaction aentry catalystadditive%conv b1HOTf -992HOTf 5%H-sponge <43HOTf 20%Bu 4NOAc 334HOTf 100%Bu 4NOAc 115HOTf 200%Bu 4NOAc 16EDTA -07AcOH -08Cu(OTf)2-999c Cu(OTf)21%EDTA9910cCu(OTf)21%EDTA þ5%H-sponge 011Cu(OTf)25%H-sponge 012Cu(OTf)220%Bu 4NOAc 713Cu(OTf)2100%Bu 4NOAc 014Ba(ClO 4)2-9915c Ba(ClO 4)21%EDTA9916cBa(ClO 4)21%EDTA þ5%H-sponge 017Ba(ClO 4)25%H-sponge 018Ba(ClO 4)220%Bu 4NOAc 2319Ba(ClO 4)250%Bu 4NOAc <120d Pd(L)(H 2O)2(OTf)2-9921c ,d Pd(L)(H 2O)2(OTf)21%EDTA9922c ,dPd(L)(H 2O)2(OTf)21%EDTA þ5%H-sponge <123dPd(L)(H 2O)2(OTf)25%H-sponge <124dPd(L)(H 2O)2(OTf)220%Bu 4NOAc6aReaction conditions:1(0.13mmol);2a (0.1mmol);catalyst (1mol %);CH 2Cl 2(1mL);20min.Proton sponge refers to N ,N ,N 0,N 0-tetra-methyl-1,8-naphthalenediamine.b Determined by 600MHz 1H NMR.cAdded as neutral tetracarboxylic acid.d (R )-BINAP-Pd(H 2O)2(OTf)2was used.species in the diacetoxylation of alkenes with iodobenzene diacetate.Therefore,the generality of the catalytic capability of protons in this type of reaction had to be established and compared to previous observations made in the apparent metal catalysis.14As shown in Table 4,both copper triflate and triflic acid itself were efficient,the latter possessing only trace amounts of transition metals (<1ppm of Co,Cu,and Ni,<5ppm of Pd).The less reactive substrates required acetic acid as solvent and elevated reaction temperatures (entries 3-9).For the substrates in entries 4and 5possessing longer chains between the carboxyl and acetyloxy groups,both cyclic and acyclic products were observed by 1H NMR.To avoid this problem,water was added to the reaction mixture,which was subsequently worked up by treatment with acetic anhydride to obtain clean diacetoxylations of the terminal alkenes.By tuning the reaction conditions with or without addition of water,both the cyclic ethers and the acyclic diacetoxylation products were obtained,respectively (entries 6and 7).The cyclizations involving carboxyl groups,giving lactones,proceeded more cleanly compared to those of hydroxyl groups,yielding cyclic ethers that may be due to the eliminationof water as a side reaction.Notably,the latter occurred exclusively in the diacetoxylation of 1-allylcyclohexanol 2f in the presence of water (entry 9).As far as the intermolecular version of this reaction is con-cerned,tri flic acid was e fficient for a variety of alkenes.In a comparative study,HOTf gave the same or better yields and diastereoselectivities than the Pd(OTf)2or Cu(OTf)2catalysts (entries 1-4,Table 5).The reactions were carried out with or without water in glacial acetic acid,giving the same yields but quite di fferent diastereoselectivities (entries 3and 4).As dis-cussed below,a possible explanation is the reaction of a non-metalated cyclic cationic intermediate with water,generating a nonacetylated hydroxyl group,which in turn is transformed to OAc after treatment with acetic anhydride in the workup (vide infra).14a Both cis -and trans -stilbene gave the syn-diastereomer as the major product (entries 1-6),which may be due to an intramolecular rotation within the cationic intermediate.Cyclic and terminal aliphatic alkenes also gave good yields and diaster-eoselectivities (entries 7and 8and entries 14and 15)as did styrene itself and its derivates (entries 9and 10).The reaction in wet acetic acid gave the 2-hydroxyl derivative (entries 11and 13),underscoring the interpretation of the role of water given above.In the presence of water in acetic acid,very similar diastereos-electivites were obtained as reported in ref 14a.However,in dry acetic acid,diastereoselectivities decreased,probably due to the change in the attacking nucleophile.For example,cis -stilbene a fforded the diacetoxylation products with the ratio of syn/anti of 10/1and 6/1in our case (entry 4,Table 5)and in ref14a,respectively.When the reactions were carried out in dry acetic acid,in contrast,very low diastereoselectivities were observed both with the palladium catalyst or tri flic acid (entries 2and 3).Finally,the dioxygenation of R ,β-unsaturated ester 4k also gave the corresponding reaction product in moderate yield (entry 16).It is instructive to compare the results obtained in this study for the intra-and intermolecular diacetoxylations/dioxygenations summarized in Tables 4and 5using tri flic acid as catalyst to those obtained previously as well as in our own study as a result ofTable 3.Proton-Trapping Study onthe Intermolecular Reaction of Styrene with Iodobenzene Diacetateentry catalystadditive (mol %)t ,h %conv 1HOTf (5mol %)-6972HOTf (5mol %)6mol %H-sponge 2403HOTf (5mol %)100mol %Bu 4NOAc 2404HOTf (5mol %)6mol %Bu 4NOAc 2405Cu(OTf)2(5mol %)-4446Cu(OTf)2(5mol %)6mol %Bu 4NOAc 4327Cu(OTf)2(5mol %)12mol %Bu 4NOAc 2408Cu(OTf)2(5mol %)6mol %H-sponge 4369Cu(OTf)2(5mol %)12mol %H-sponge 24010(R)BINAP-Pd(H 2O)2(OTf)2(5mol %)-46611(R)BINAP-Pd(H 2O)2(OTf)2(5mol %)6mol %H-sponge 24012(R)BINAP-Pd(H 2O)2(OTf)2(5mol %)6mol %Bu 4NOAc 24013Pd(OAc)2(5mol %)-4014CuCl 2(5mol %)-4015Cu(OAc)2(5mol %)-4aReaction conditions:1(0.5mmol);2(0.25mmol);CH 2Cl 2(0.5mL);AcOH (12.5μL).bDetermined by 600MHz 1H NMR.Figure 3.The comparison of the [(R )-BINAP-Pd(H 2O)2(OTf)2]-catalyzed (3mol %)diacetoxylation of styrene with or without an equivalent amount of Bu 4NOAc:1mol of added base essentially quenches 1mol of Pd catalyst.catalysis by a palladium triflato complex14a as well as copper triflate.14b The intramolecular dioxygenation of2e with triflic acid (entry7,Table4)gave the reaction product in72%yield compared to78%and80%yield reported in the literature using phosphine palladium triflate and copper triflate as catalysts, respectively.14a,b Furthermore,the dioxygenation of2f catalyzed by triflic acid led to almost the same yield of the reaction product as the Pd(dppp)(H2O)2(OTf)2catalyst reported by Dong et al.14a For the intermolecular diacetoxylation reaction,very similar results were obtained under the same reaction conditions.For example,the diacetoxylation of styrene catalyzed by Pd(dppp)-(H2O)2(OTf)2,copper triflate,and triflic acid(entry9,table5) at room temperature gave the corresponding reaction products in90%,80%(at40°C),and91%yields,respectively.The diacetoxylations of4b,4i,and4j catalyzed by triflic acid (Table5)gave the same or higher yields and diastereoselectiv-ities(same major diastereomers)as those catalyzed by the palladium and copper triflate catalysts.14a,b In conclusion,in both the intra-and intermolecular diacetoxylations,triflic acid always gave comparable yields and diastereoselectivities to those ob-tained with the metal triflato complexes.Assuming a general catalytic principal for this transformation,this further supports the aforementioned hypothesis that the diacetoxylation of alkenes with iodobenzene diacetate is a proton-catalyzed reaction.Kinetic Study of the HOTf-Catalyzed Diacetoxylation of Styrene with Iodobenzene Diacetate.The diacetoxylation of styrene with iodobenzene diacetate may be conveniently fol-lowed by1H NMR which was employed in a kinetic study using added2-bromo-1,3-xylene as internal standard.This established a first-order dependence of the reaction rate on both the concentration of HOTf(Figure4)and the oxidant PhI(OAc)2 (Figure5).Remarkably,zeroth order dependence on the reaction rate was established for the substrate styrene(Figure6),indicating a mechanism in which the rate-determining step precedes the interaction of the oxidant with the olefin.In Situ Mass Spectra and Discussion of a Potential Reac-tion Mechanism.In situ high resolution ESI mass spectra recorded during the diacetoxylation of styrene and R-methyl-styrene are depicted in Figure7A and7B,respectively. Samples were taken1-5min after mixing of the reagents and diluted with CH3CN prior to the injection into the mass spectrometer.First of all,we note the presence of peaks at m/z=262.95635, 344.95942,and260.93336,which are assigned to the ions [PhI(OAc)]þ,[PhI(OAc)2-Na]þ,and[PhI(OAc)2-K]þ, respectively.All three species are derived from the oxidizing agent alone and were also found previously in ESI mass spectra of PhI(OAc)2.20Notably,an additional mass peak in Figure7A ata Reaction conditions:1(0.65mmol);2(0.50mmol);solvent(1mL).b Isolated yield.c Reaction product3a is formed by a rearrangement step following the initial diacetoxylation;see ref19.d With3equiv of H2O;after reaction,if treated with acetic anhydride,OH was transformed to OAc.e Using1.0 mmol of2and0.2mL of AcOH.m /z =306.99782and the corresponding peak in Figure 7B at m /z =321.01347are assigned to [PhCCH 2(IPh)]þand [Ph-(Me)CCH 2(IPh)]þ,respectively,which are species generated by the interaction of the oxidant with styrene and R -methylstyrene.They are thought to be derived from one of the key intermediates in the catalytic cycle for the proton-catalyzed diacetoxylation of alkenes.The proposed mechanism of the catalytic cycle for the diacetoxylation of styrene (as example of alkene substrates in general)is represented in Scheme 2.Upon protonation of iodobenzene diacetate,one molecule of AcOH is eliminated,giving rise to the cationic intermediate A .The possibility of the protolytic formation of A has been previously demonstrated and is supported by a series of X-ray crystal structure determinationsaReaction conditions:1(0.65mmol);4(0.50mmol);AcOH (1mL).b Isolated yield.c (R )-BINAP-Pd(H 2O)2(OTf)2was used.d With 3equiv of H 2O;after reaction,if treated with acetic anhydride,OH was transformed to OAc.of such species reported by Ochiai and co-workers.21The cation A was also observed in the HRMS-ESI study discussed above and was previously found in the HRMS-ESI mass spectra of PhI-(OAc)2.20Our kinetic study established first-order dependence of the reaction rate on the concentration of added tri flic acid as well as oxidant but zeroth order dependence on the concentra-tion of the alkene.This suggests that the formation of A is the rate-determining step in the catalytic cycle and that the cationic iodoso reagent is rapidly trapped by the alkene (in this case styrene)to form B .As indicated in the previous section,the formation of B is supported by the observation of the peakm /z =306.99782and the corresponding peak at m /z =321.01347in the in situ recorded HR mass spectra from the diacetoxylation of styrene and R -methylstyrene.These mass peaks are assigned to [PhCCH 2(IPh)]þand [Ph(Me)CCH 2-(IPh)]þ,respectively,which are probably formed by elimination of AcOH from B under the conditions of the HRMS experi-ments.In the following step,intermediate B could be attacked by acetate either from acetic acid attacking externally (pathway b)or,in an intramolecular rearrangement,from OAc in B (pathway a),and both intermediatescould form the cyclic intermediate E ,Figure 4.Dependence of the initial rate on TfOH:(A)Plots of [styrene]vs time using TfOH;(B)initial rate vs TfOH (mol %).Initial rates were calculated as the slopes of time zero using Originlab software.Reaction conditions (initial):[styrene]=0.50M (0.25mmol),[PhI(OAc)2]=0.7M,TfOH (1-7mol %),AcOH (5.0M),CD 2Cl 2,RT,recorded on 600MHz 1H NMR.Figure 5.Dependence of initial rate on initial [PhI(OAc)2]:(A)Plots of [styrene]vs time and (B)initial rate vs initial [PhI(OAc)2].Initial rates were calculated as the slopes of time zero using Originlab software.Reaction conditions:[styrene]=0.50M,[PhI(OAc)2]=0.6-1.0M,[TfOH]=25mM,AcOH (5.0M),CD 2Cl 2,RT,recorded on 600MHz 1H NMR.Figure 6.Dependence of initial rate on initial [styrene]:(A)Plots of [styrene]vs time,(B)initial rate vs initial [styrene].Initial rates were calculated as the slopes of time zero using Originlab software.Reaction conditions:[styrene]=0.30-0.70M,[PhI(OAc)2]=0.7M,[TfOH]=25mM,AcOH (5.0M),CD 2Cl 2,RT,recorded on 600MHz 1H NMR.which had also been proposed by Dong et al.in the published catalytic cycle based on a Pd II /Pd IV catalytic system.14a Finally,the cyclic cation is attacked by AcOH to a fford the diacetoxyla-tion product along with with the liberation of a proton which then acts as catalyst in the next cycle.What remains to be addressed is the role played by the metal dications/metal complexes which catalyze the diacetoxylation of alkenes.The sigmoidal behavior of the conversion curves and the observation of a point of in flection provide an indication that the catalytically active species is being generated during an initiation step.This may be the formation of the cationic key intermediate A ,the generation of which is initially catalyzed by the Lewis acidic metal dications.In the following reaction steps,one excess proton is generated provided that the metal salt or metal complex does not contain a basic counterion such as acetate.The excess proton(s)then act as (more active)catalyst in the subsequent reaction cycle,thus making the proton the e ffective catalyst also in these cases as demonstrated by theabsence of any catalytic activity in the presence of proton-capturing agents.Finally,the presence of chlorido or other potentially coordinating ligands,in turn,will suppress the formation of A due to recombination with the cation and thus deactivation of the actual oxidizing agent.’CONCLUSIONIn this work,we have provided evidence for the protiocatalytic nature of the diacetoxylation of alkenes using PhI(OAc)2as oxidant.Metal cations,such as Pd(II)and Cu(II),may interact with the oxidant in the initiation phase of the catalytic transfor-mation;however,1equiv of strong acid is produced in the first cycle which then functions as the active catalyst.A mechanistic cycle for the protiocatalytic reaction,which is consistent with all experimental data presented in this work,has been proposed.Based on this discovery of proton catalysis for the reaction at hand,we developed the intra-and intermolecular tri flic acid-catalyzed dioxygenation for a range of alkene substrates.On the basis of our observations,particular care has to be taken in the interpretation of metal catalysis involving Ph(OAc)2as a substrate.It is clear that Pd-catalyzed reactions 6performed under basic conditions are not explicable by a simple protolytic scheme as put forward in this work.’ASSOCIATED CONTENTbSupporting Information.Experimental details and char-acterization data.This material is available free of charge via the Internetat .’AUTHOR INFORMATIONCorresponding Authorlutz.gade@uni-hd.deFigure 7.HRMS-ESI experiments for reaction solutions.Reaction conditions:styrene or R -methylstyrene (0.125mmol),PhI(OAc)2(0.25mmol),TfOH (1M in AcOH,50μL),AcOH (0.45mL),RT,1-5min,diluted with CH 3CN before HRMS-ESI tests.Scheme 2.Proposed Mechanism for the TfOH-Catalyzed Intermolecular Diacetoxylation of StyreneBased on the Evidence Presented in This Work’ACKNOWLEDGMENTWe are grateful to Dr.J€u rgen H.Gross(Univ.of Heidelberg) for help concerning the in situ recorded mass spectra.Y.-B.Kang works at CaRLa of the University of Heidelberg,being cofi-nanced by the University of Heidelberg,the state of Baden-W€u rttemberg,and BASF SE.Support from these institutions is greatly acknowledged.’REFERENCES(1)(a)Woodward,R.B.;Brutcher,F.V.J.Am.Chem.Soc.1958,80, 209.(b)Prevost,pt.Rend.1933,196,1129.(2)(a)Hudlicky,M.Oxidations in Organic Chemistry;ACS Mono-graph Series186;American Chemical Society:Washington,DC,1990;p 174.(b)Johnson,R.A.;Sharpless,K.B.In Catalytic Asymmetric Synthesis,2nd ed.;Ojima,I.,Ed.;Wiley-VCH:New York,2000;p357.(c)Haines,A.H.In Comprehensive Organic Synthesis,1st ed.;Trost,B.M.,Fleming,I.,Eds.;Pergamon:Oxford,1991;Vol.7,p437.(3)(a)VanRheenen,V.;Kelly,R.C.;Cha,D.Y.Tetrahedron Lett. 1976,1973.(b)Eames,J.;Mitchell,H.;Nelson,A.;O’Brien,P.;Warren, 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铝液氢的界面反应过程动力学研究_熊艳才
4. 47× 10- 3 6× 10- 5
在铝液中的扩散能力及自由界面的面积。 反应的动力来 源于氢在铝液与界面上的浓度梯度。 故氢在界面上的反 应速度是不断变化的 , 由于氢和铝液组成理想稀溶液, 那么: C HS = K P H2 ( 5)
式中 K —— Sievert 常数 P H2 —— 界面上氢的分压, P a 在开始时 , 界面上氢的浓度为零 , 此时反应动力最 大 , 随着时间的延长, 界面上的氢分压增大 , 氢的浓度增 加 , 反应动力变小 , 所以反应速度也减慢 , 最后达到平 衡 , 氢的分压也不再变化, 即 CH S = C H 1. 3 析出过程的计算 对任一时刻 t i , 界面上的氢浓度与界面内的氢分压 p i 均遵从 Herry 定律: Ci = k Pi ( 7) ( 6)
X 熊艳才 , 男 , 33 岁 , 高级工程师 , 北京( 100095) 收稿日期 : 1998- 04- 20
dn H2 ——单位时间内生成 H 2 的摩尔数 , mo l/ s dt 铝液中氢原子向自由表面扩散的传质速度为: N H 2 = k ( C H - C HS ) 式中 N H2 ——氢的传质速度, m L ・m / s k ——氢的传质系数 , m/ s CH ——每 100 g 铝液中氢的含量, mL ( 3)
4. 47× 10
- 3
m , 真空系统的体积为 6 ×10
2
- 5
m。
3
若惰性气体的流量为 G , 在时间 $t 内产生气泡的 个数 S 为:
3 S = 6G $t / P d 式中 d —— 气泡直径 , m
2. 2 测试结果 利用上述测试装置, 测试了每 100 g 铝液氢含量分 别为0. 1 mL , 0. 2 mL , 0. 3 mL 三种条件下的氢在探头 表面的析出过程。 上述三种氢含量状态的铝液在测试过 程中取样, 经固态测氢法标定。所用设备为美国 L ECO 公司生产的 L ECO RH -3 型定氢仪。 测试结果如图 3 所 示。
应用化学专业英语第二版万有志主编版(课后答案和课文翻译)
Unit 1 The Roots of ChemistryI. Comprehension.1.C2. B3. D4. C5. BII. Make a sentence out of each item by rearranging the words in brackets.1. The purification of an organic compound is usually a matter of considerable difficulty, and it is necessary to employ various methods for this purpose.2. Science is an ever-increasing body of accumulated and systematized knowledge and is also an activity by which knowledge is generated.3. Life, after all, is only chemistry, in fact, a small example of chemistry observed on a single mundane planet.4. People are made of molecules; some of the molecules in people are rather simple whereas others are highly complex.5. Chemistry is ever present in our lives from birth to death because without chemistry there is neither life nor death.6. Mathematics appears to be almost as humankind and also permeates all aspects of human life, although many of us are not fully aware of this.III. Translation.1. (a) chemical process (b) natural science (c) the technique of distillation2. It is the atoms that make up iron, water, oxygen and the like/and so on/andso forth/and otherwise.3. Chemistry has a very long history, in fact, human activity in chemistry goesback to prerecorded times/predating recorded times.4. According to/From the evaporation of water, people know/realized thatliquids can turn/be/change into gases under certain conditions/circumstance/environment.5. You must know the properties of the material before you use it.IV . Translation化学是三种基础自然科学之一，另外两种是物理和生物。
戊二醛与羟基的交联机理
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REVISTADEMETALURGIA,46(1)ENERO-FEBRERO,22-36,2010ISSN:0034-8570eISSN:1988-4222doi:10.3989/revmetalm.0852
22Somekineticsaspectsofchlorine-solidsreactions(•)N.Kanari*,D.Mishra**,J.Mochón***,L.F.Verdeja****,F.Diot*andE.Allain*AbstractThepresentpaperdescribesdetailedkineticsinvestigationsonsomeselectedchlorine-solidreactionsthroughthermo-
gravimetricmeasurements.Thesolidsstudiedinthisarticleincludechemicalpureoxidesandsulfidesaswellastheirnaturalbearingmaterials.ThechlorinatingagentsemployedaregaseousmixturesofCl2+N2(chlorination),Cl2+O2(oxychlorination),andCl2+CO(carbochlorination).Resultsarepresentedaseffectsofvariousparametersonthe
reactionrateofthesesolidswiththesechlorinatingagents.Itwasobservedthatthereactivityofthesesolidstowardsdifferentchlorinatingagentsvariedwidely.Sulfidescouldbechlorinatedatroomtemperature,whilecarbochlorinationofchromium(III)oxidewaspossibleonlyabove500°C.Thevariationofthechlorinationrateofthesecomplexmaterialswithrespecttogasvelocity,compositionandtemperatureenabledustofocussomelightontheplausiblereactionmechanismsandstoichiometries.Theobtainedresultswereusedforselectiveremovalofironfromchromiteconcentrates,extractionofvaluablemetalsfromsulfidematerials,purificationofMgOsamples,etc.
KeywordsThermogravimetricanalysis;Complexoxides;Sulfides;Chlorination;Oxychlorination;Carbochlorination;Kinetics.
AlgunosaspectoscinéticosdelasreaccionesdesólidosconcloroResumenEstetrabajodescribedetalladasinvestigacionescinéticasenalgunasreaccionesseleccionadasdecloro-sólidoatravés
demedidastermogravimétricas.Lossólidosestudiadosenesteartículoincluyenóxidosquímicospurosysulfuros,asícomosusmaterialesnaturalesdesoporte.LosagentesdecloraciónempleadossonmezclasdegasesdeCl2+N2(clo-ración),Cl2+O2(oxicloración)yCl2+CO(carbocloración).Losresultadossepresentancomoefectodevariospará-metrosenelporcentajedereaccióndeestossólidosconlosagentesdecloración.Sehaobservadoquelareactividaddeestossólidosatravésdediferentesagentesdecloraciónvaríaampliamente.Lossulfurossepudieroncloraratem-peraturaambientemientrasquelacarbocloracióndelóxidodecromo(III)sólofueposibleporencimadelos500°C.Lavariacióndelporcentajedecloracióndeestosmaterialescomplejosconrespectoalavelocidaddelgas,composi-ciónytemperaturapermitióarrojaralgunaluzenlosposiblesmecanismosdereacciónyestequiometrías.Losresul-tadosobtenidossehanusadoparalaeliminaciónselectivadelhierrodeconcentradosdecromo,extraccióndeme-talesvaliososdematerialessulfhídricos,purificacióndemuestrasdeMgO,etc.
PalabrasclaveAnálisistermogravimétrico;Óxidoscomplejos;sulfuros;Cloración;Oxicloración;Carbocloración;Cinética.
1.INTRODUCTIONItiswellknownthatchlorinepossessesahighreactivitytowardsdifferentsubstancesatlowtemperatures.Further,manymetalchloridesand/oroxychlorideshavelowboilingpointsandalsohaveappreciablydifferentvaporpressuresataparticulartemperature.Theseaspectsledthe“chlorine
technique”asthesubjectofmuchattentioninareaslikemineralbeneficiation,metalextractionandwastetreatment.Manyimportantarticlesdevotedtothechlorinationcanbefoundintheliterature[1].
Thepresentpapermainlyfocusesonthekineticsaspectsofchlorine-solidsreactionsapproachedthroughthermogravimetricmeasurements.Besides,higherselectivityofthechlorinationmethodsby
(•)Trabajorecibidoeldía4dediciembrede2008yaceptadoensuformafinaleldía3dejuliode2009.
*LaboratoireEnvironnementetMinéralurgie,UMR7569CNRS,Nancy-University,ENSG,BP40,54501Vandoeuvre-lès-NancyCedex,France.e-mail:ndue.kanari@ensg.inpl-nancy.fr**NationalMetallurgicalLaboratory(NML),Jamshedpur,India–831007.***CENIM-CSIC,Av.GregoriodelAmo8.Madrid28040,Spain.****E.T.S.I.deMinasdeOviedo,CátedradeSiderurgia,Independencias/n.Oviedo33004,Spain.SOMEKINETICSASPECTSOFCHLORINE-SOLIDSREACTIONS
ALGUNOSASPECTOSCINÉTICOSDELASREACCIONESDESÓLIDOSCONCLORO
REV.METAL.MADRID,46(1),ENERO-FEBRERO,22-36,2010,ISSN:0034-8570,eISSN:1988-4222,doi:10.3989/revmetalm.085223employingdifferentchlorinatingmediumsuchasoxychlorination(Cl2+O2)orcarbochlorination
(Cl2+CO)isalsodiscussed.Belowparagraphsdepict
someexampleswheredetailedkineticstudiesweremade.ThefirstexamplepresentshowCl2canbeused
atlowtemperatureforextractionofnon-ferrousmetalsfromsulfideconcentrates(CuFeS2,PbS,ZnS,
FeS2,etc.).Itwasobservedthatthesesulfidesinteract
withchlorineevenatroomtemperature[2-4].Atabout
300°C,generatedironandsulfurchlorideswerevolatilizedwhilstthevaluablemetalchlorides(CuCl2,
PbCl2,andZnCl2)wereessentiallyconcentratedin
thechlorinationresidues.Morethan95%ofcoppercontainedintheconcentratewasrecoveredintheresidueat300°CaswatersolubleCuCl2.