Au单晶电极上H2O2的氧化反应研究

本文利用旋转圆盘电极系统研究了酸性介质中H₂O₂在Au(100)和Au(111)电极表面的电化学行为. 实验发现在Au电极上H₂O₂难以发生还原,但是当电位稍微正于H₂O₂氧化为O₂的平衡电势时即可发生氧化. 在Au(111)上H₂O₂氧化的起始电位比在Au(100)正0.1 V左右. Au(100)上的双桥位位点能增强反应中间体*OOH的吸附,可能是导致Au(100)上H₂O₂氧化反应超电势比Au(111)低的主要原因. 在较正电位区(E>1.2 V), 当电极表面被氧物种覆盖时,H₂O₂在两个电极上的氧化都会受到一定程度的抑制,这种影响在Au(111)上比Au(100)上更加明显,这与Au(111)上氧物种的生成与逆向还原可逆性差的趋势一致. 最后还将Au与Pt单晶电极上H₂O₂氧化的行为进行了对比分析.     

泡沫镍载 NiCO2O4电极的制备及其催化 H2O2电氧化的性能

本文以水热法结合热处理法原位制备了泡沫镍载 NiCo₂O₄纳米线电极,使用XRD、SEM和TEM对合成的 NiCo₂O₄纳米线进行了表征,NiCo₂O₄纳米线直径约80 nm,长度约 3 ~ 5 μm. 使用循环伏安和计时电流法测试了泡沫镍载NiCo₂O₄纳米线催化H₂O₂的电氧化性能,结果表明泡沫镍载NiCo₂O₄纳米线对H₂O₂电氧化有着优良的催化活性、稳定性和传质性能,在0.3 V电位下0.4 mol·L ^-1 H₂O₂和2 mol·L ^-1 NaOH溶液中氧化电流可达380 mA·cm ^-2.     

以城市污泥基氧化石墨烯为模拟酶比色传感检测H2O2

本研究构建了以城市污泥基氧化石墨烯(GO)为模拟酶的比色传感器用于定量检测H₂O₂。以城市污泥为基质利用改进Hummers法制备氧化石墨烯(GO),利用GO具有过氧化物模拟酶的特性，能够催化H₂O₂与3,3′,5,5′-四甲基联苯胺(TMB)的显色反应定量检测H₂O₂。结果显示，在最佳检测条件HAc-NaAc缓冲溶液pH 4.8、TMB溶液浓度30 mmol·L^-1和城市污泥基GO浓度460μg·mL^-1时，H₂O₂浓度在0.1～2μmol·L^-1和10～150μmol·L^-1范围内，与体系吸光度呈良好的线性关系，最低检测限为0.01μmol·L^-1。此方法对实际水样中H₂O₂含量进行检测，回收率在99%～103.77%之间。研究表明，城市污泥基GO具有与传统G...     

苯甲醇的绿色选择性氧化

醇的氧化是制备醛和酮的重要反应之一,也是有机化学理论教学和实验教学的一个重点内容。目前,大多数本科生实验教材安排了环己醇氧化合成环己酮的实验。虽然现有实验教材提供了一例将伯醇氧化为醛的方案,即采用Na₂WO₄·2H₂O/（C₄H₉）₄NHSO₄催化体系,在90°C用H₂O₂将苯甲醇选择性氧化为苯甲醛,但是存在着产率低、安全性不高和重金属污染等问题。本文采用Fe（NO₃）₃·9H₂O、4-羟基-2,2,6,6-四甲基哌啶氧化物（4-OH-TEMPO）和乙酸（HOAc）为催化剂、O₂为氧化剂,以H₂O为溶剂,在温和的反应条件下高选择性地将苯甲醇氧化为苯甲醛,分离产率可达91%,这为伯醇的选择性氧化提供了一个低成本且高效绿色的实验教学新方案。同时,在实验过程中引入薄层色谱、气相色谱、快速制...     

SnCl4催化丙酮与过氧化氢反应制取大环过氧化物

H₂O₂与过渡金属构成的催化体系可选择性地氧化烃类化合物,如芳烃的羟基化和烯烃的环氧化等^[1～3],且H₂O₂在应用中无环境污染,是一种颇有前途的氧化剂.有关金属催化H₂O₂与酮类化合物反应的报道很少.     

B-TS-1分子筛的合成及其催化氧化性能

通过将杂原子B引入钛硅-1（TS-1）分子筛对其进行改性,并研究其催化氧化性能。结果发现,B-TS-1明显延长了环己酮氨肟化反应运行寿命。结合氨肟化体系催化剂失活主要原因以及反应体系H₂O₂反应路径,分析表明,H₂O₂是控制TS-1/H₂O₂氨肟化体系副反应发生的关键,并且有机副产物是导致催化剂堵孔失活的重要原因。本文提出B-TS-1能有效控制体系H₂O₂残留,从而进一步抑制副反应发生与积碳生成以延长催化剂寿命。结合Al-TS-1的催化特性,发现同时引入适量B、Al的B/Al-TS-1具有进一步提高环己酮肟化反应稳定性的作用。     

溶解有机质对光照自然水体生物膜体系中H2O2生成的影响

通过模拟实验研究了生物膜胞外聚合物(EPS)和乙二胺四乙酸(EDTA) 2种典型溶解有机质(DOM)成分对自然水体生物膜体系中过氧化氢(H₂O₂)生成特征的影响, 并研究了体系初始pH值、 DOM浓度、 溶解氧(DO)等因素的影响. 结果表明, DOM的存在对自然水体生物膜体系中H₂O₂的生成有明显影响. 光照能促使EPS产生H₂O₂, 而EPS的存在对生物膜产生H₂O₂的直接影响不显著, EPS与生物膜共存体系中的H₂O₂由二者共同产生; EDTA本身不产生H₂O₂, 且对H₂O₂分解影响很小, 但会显著抑制生物膜产生H₂O₂, 且浓度越高抑制作用越明显. 体系pH值、 DOM浓度和DO均能不同程度影响EPS产生H₂O₂及EDTA抑制生物膜产生H₂O₂的作用.     

UV-Vis/H2O2/草酸铁络合物法在水处理中的应用

介绍了各光Fenton法的运行机理及存在的优缺点,综述了UV-Vis/H₂O₂/草酸铁络合物法在水处理中的应用状况,并对其今后的发展趋势进行了阐述.UV-Vis/H₂O₂/草酸铁络合物法是一种新的高级氧化技术,是对光Fenton法的发展,在处理高浓度难降解有机废水方面效果优于UV/Fe²⁺/H₂O₂法、UV/H₂O₂法、TiO₂法和WO₃法等,因其具有一定的利用太阳能的潜力,所以具有较好的应用前景.     

过氧化氢调控藜芦醇介导木素过氧化物酶催化氧化邻苯三酚红研究

木素过氧化物酶(LiP)催化H₂O₂氧化邻苯三酚红(PR)反应的氧化产物受H₂O₂与PR的摩尔比控制, H₂O₂与PR的摩尔比不同, 所得降解产物不一样. 分析表明, H₂O₂在LiP催化氧化PR过程中的双重作用(即低浓度的H₂O₂是LiP的激活剂, 高浓度的H₂O₂是LiP的抑制剂)是导致上述现象的根本原因. 藜芦醇(VA)对LiP催化氧化PR的反应有促进作用, 尤其是当H₂O₂与PR的摩尔比较高时这种促进作用更为明显; 然而PR对LiP催化氧化VA的反应却有抑制作用. 后者可以用来解释为什么在用白腐菌降解染料时在培养液中常常检测不到LiP的藜芦醇活力. 分析表明, VA的存在不但促进了LiP酶中间体LiP(II)和/或LiP(III)向LiP的转化, 使LiP的催化循环加速, VA生成的VA^＋·也间接氧化了染料PR, 从而使PR的氧化速率提高.     

基于CoFe(Ⅲ)PBA/GO过氧化物模拟酶化学发光法检测H2O2和抗坏血酸

制备了一种具有过氧化物酶活性的类普鲁士蓝/氧化石墨烯复合纳米材料(CoFe(Ⅲ)PBA/GO)。将具有过氧化物酶活性的CoFe(Ⅲ)PBA/GO和化学发光法相结合,构建了一种用于检测H₂O₂和抗坏血酸(AA)的化学发光分析法。CoFe(Ⅲ)PBA/GO催化H₂O₂产生的O₂·^-,·OH,1O₂自由基氧化Luminol会产生很强的化学发光信号,通过检测化学发光强度可以实现对H₂O₂的检测。该方法检测H₂O₂的线性范围为0~0.8μmol/L,检测限为11 nmol/L。利用AA作为活性氧消除剂可以抑制化学发光反应的特点,实现了AA的检测。该方法测定AA的线性范围为0.02~0.8μmol/L,检测限为20 nmol/L。方法已应用于H₂O₂消毒水中H₂O₂和维生素C片中抗坏血酸的检测。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.