Transition-Metal-Catalyzed Direct Substitution of Alcohols in Aqueous Media

The direct use of alcohols as the much greener and more sustainable alkylated reagents in substitution reactions is one of the emerging areas in green chemisty. However, owing to the poor leaving character of OH group, the direct substitution of alcohols is not an easy thing. Transition metal (TM) catalysis such as Pd-catalyzed allylic/benzyl substitution and Ir-catalyzed borrowing hydrogen provides efficient protocols for the direct substitution of alcohols, however, an organic solvent and servely anhydrous conditions are generally required. In recent decade, TM-catalyzed direct substitution of alcohols in aqueous media was developed as a much greener alternative. In this review, the recent develpoments of this area are summarized. The activation mechanism of alcohols in aqueous reactions are emphatically discussed.     

Ceric Ammonium Nitrate Catalyzed Oxidation of Aldehydes and Alcohols

A variety of aromatic, aliphatic and conjugated aldehydes and alcohols were transformed to the corresponding carboxylic acids and ketones with a quantitative conversion in high yields with 70% t‐BuOOH solution in water in the presence of catalytic amounts of ceric ammonium nitrate [Ce(NH₄)₂(NO₃)₆] (CAN) under room temperature conditions. The scope of our catalytic system is applicable for a wide range of aromatic, conjugated and aliphatic substrates. These aldehydes were converted to the corresponding carboxylic acids in good isolated yields in reasonable times. This method possesses a wide range of capabilities since it can be used with other functional groups which may not tolerate oxidative conditions, involves fairly simple method for work‐up, exhibits chemoselectivity and proceeds under ambient conditions. The resulting products are obtained in good yields within reasonable time.     

Novel Method of Synthesis of Quaternary Ammonium Tribromides and Investigation of Catalytic Role of Benzyltrimethylammonium Tribromide in Oxidation of Alcohols to Carbonyl Compounds

Stable crystalline organic quaternary ammonium tribromides (QATBs) have been easily synthesized by the oxidation of the corresponding organic ammonium bromides (QABs) with ammonium persulfate. The reactions have been performed under solvent-free conditions in the presence of sulfuric acid and silica as supporting agent. Two equivalents of potassium bromide have been used as the source of additional bromides for quantitative conversion of QABs to QATBs. Ammonium persulfate, a cheap and readily available oxidant, carries out the bromide oxidation to tribromide very effectively under solvent-free conditions. The synthesized QATBs have been shown to catalyze the oxidation of alcohols to carbonyl compounds with hydrogen peroxide as oxidant in good yields under mild reaction conditions.     

利用离子膜电解法改进过硫酸铵生产研究

国内工厂生产过硫酸铵大多采用工艺简单且产品纯度高的电解法,但是电解法在生产过程中存在能耗过高的问题。这一问题限制了过硫酸铵在许多领域的进一步发展。针对这一现象,对硫酸铵电解生成过硫酸铵的设备及工艺进行设计和研究,以期达到降低能耗的目的。实验基于零极距和离子交换膜电解槽的设计,研究了加酸量、抑制剂用量、出入口温度和电解液浓度等因素对电解效率的影响。结果表明,在电解液中加酸并且在阳极液中添加抑制剂对提高电流效率和降低槽电压具有很大的影响,在最优条件下电流效率可达到98%,生产过程能耗显著降低。另外,电解槽还具有连续性生产、占地面积小的优势,进一步解决了厂家所面临的生产成本过高的问题。     

Oxidation of Long Chain Primary Alcohols to Acids over the Quaternary Ammonium Peroxotungstophosphate Catalyst System

Factors influencing the catalytic properties for long chain primary alcohol oxidation to acid over quaternary ammonium peroxotungstophosphate catalyst were investigated. The catalysts were characterized by means of IR and NMR techniques. Based on the experimental results, the catalyst active centers for the title reaction were elucidated and optimal reaction conditions given.     

Persulfate Oxidation and Diphenylcarbazide Photometric Determination of Chromium in Super Alloys

The quantitative analysis of Cr in super alloys with the presence of a wide variety of elements, Al, B, C, Co, Cu, Hf, Fe, Mn, Mo, Ni, Nb, P, Si, S, Ti, Ta, W, Zr; and trace amounts (a few ppm) of Pb, Se, Bi, Tl and Te has been studied. Persulfate oxidation and diphenylcarbazide photometric method were studied with the purpose of developing a relatively fast and reliable measurement for Cr by wet chemical analysis. The results indicate that the latter is supperior to the former in practical view. In the photometric method, solid sample (0.1g alloys) when treated with HClO₄ and H₂SO₄ took ca. 72 hrs. for complete dissolution. When treated with HCl followed by HNO₃, 0.1 g alloys were completely dissolved within 1&1/2; hours. The best experimental conditions for diphenylcarbazide photometric determination of Cr was thus established. Photometric determination of Cr complexes was made at 540 nm.     

基于过硫酸盐活化的微界面电子转移氧化技术

基于过硫酸盐活化的高级氧化技术是当前环境领域的研究热点.然而,环境中广泛存在的基质严重地制约了这一技术的实际应用.最新研究表明,在某些催化剂的作用下,过硫酸盐能够以电子转移的非自由基机制氧化降解污染物,而催化剂主要起电子转移媒介的作用.这一技术不易受水环境中氯离子、碳酸氢根离子等常见阴离子和天然有机物的影响,对目标污染...     

过硫酸盐活化高级氧化新技术

过硫酸盐在热、光、过渡金属催化等条件激活下产生强氧化性的硫酸根自由基·SO₄^-。基于·SO₄^-的过硫酸盐活化“高级氧化技术”在环境污染治理领域的应用,是刚刚发展起来的崭新的研究方向,具有广阔的应用前景。本文在分析其基本原理的基础上,综述了过硫酸盐活化技术在国内外土壤地下水有机污染原位修复、难降解有机废水处理等环境污染治理方面的研究进展,并就存在问题进行了研究展望。     

醇在钒基催化剂上的氧化

以过氧化叔丁醇作为氧化剂,研究了醇类(苯甲醇、1-苯基乙醇和环己醇)在钒基催化剂上的氧化反应.制备了含苯磷二酚配体或吡嗪-2-羧酸酯配体的钒配合物,并运用傅里叶变换红外光谱、核磁共振谱、紫外-可见光谱及元素分析对其进行了表征.考察了溶剂对该类反应的影响.发现在甲苯溶剂中进行氧化反应时,苯甲醇被氧化成苯甲醛而不会被深度氧化为苯甲酸;而在乙腈溶剂中,苯甲醛和苯甲酸均有生成.此外,对不同钒磷氧化物的催化活性进行了比较,结果表明,在乙腈溶剂中的产品收率比在甲苯溶剂中高.     

醇的催化氧化研究进展

从醇在金属催化剂作用下的催化氧化方面,较为详细的介绍了近年来在该研究领域内的研究进展,并指出了金属催化相对于非金属催化的优点.     

Aerobic Oxidation of Alcohols Catalyzed by a New ZnO-Supported Copper Oxide Nanocatalyst in Aqueous Media

ZnO-supported copper oxide nanocatalyst is reported as an efficient recyclable catalyst for the aerobic oxidation of alcohols in the presence of oxygen as the oxidant. The catalyst was prepared by coprecipitation method and characterized by x-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM) analysis. A variety of primary and secondary alcohols were oxidized into the corresponding carbonyl compounds in good to excellent yields. The catalyst can be recovered by simple filtration and recycled up to five consecutive runs without significant decrease in the catalytic activity.     

Determination of the Total Nitrogen Content of Organic Substances Through the Ammonia Formed in Oxidation by Persulfate

Abstract

A new concept for the analytical application of persulfate oxidation in alkaline media is presented: The persulfate oxidation of organic compounds has been utilized to determine their nitrogen content. The ammonia formed in the oxidation coupled distillation was measured acidimetrically with an accuracy of ± 0.5 % (rel.). The applicability of the method proposed is shown in the determination of the organically bound nitrogen content of numerous model substances as well as industrial and natural matrices: vinasse, aluminate liquor, white- and soy-bean samples, eggprotein.     

铬酸氢根季铵树脂对烯丙醇的选择性氧化

合成了铬酸氢根季铵盐树脂,以它作为一种选择性氧化剂应用于烯丙醇的氧化反应,考察了温度、时间、溶剂、树脂与醇的物料比对氧化反应的影响。在优化的反应条件下,即以苯为溶剂,n（树脂）：n（醇）=3．5：1,回流12h,丙烯醛产率达60．65％。实验表明,该季铵盐树脂能有效地将烯丙醇选择性地氧化为丙烯醛。     

Simple System for Oxidation of Alcohols in Aqueous Solution

A simple and mild system for conversion of primary and secondary alcohols to corresponding aldehydes and ketones has been developed using aqueous sodium dichloroiodate at room temperature in water. This novel application of aqueous sodium dichloroiodate gives high yield and offers a number of advantages in terms of safety and ease of use in comparison to other methods that often employ toxic and hazardous solvents and materials.     

Microwave-assisted Oxidation of Alcohols and Polyarenes with Cetyltrimethylammonium Bromochromate

An efficient and mild methodology for oxidation of alcohols and polyarenes was described using cetyltrimethylammonium bromochromate (CTMABC) under microwave irradiation. Primary and secondary alcohols and polyarenes could be selectively oxidized under microwave irradiation into the corresponding aldehydes and ketones in high yields and short reaction time, using commercially available and magnetically retrievable oxidative material (CTMABC).     

水相中一些有机合成反应的研究进展

水作为有机合成反应的介质具有价廉、安全、无污染、产物易于分离等优点. 综述了近年来水介质中一些有机合成反应的研究进展, 这些反应包括氧化、还原、烯丙基化、环加成、克来森、迈克尔、维悌希、缩合、偶联、自由基、有机光化学、取代等.     

乳酸促进的仲钼酸铵催化氧化环己烷过程

环己烷的催化氧化是重要的工业反应之一,为了寻找更高效廉价的催化剂,研究了仲钼酸铵(APM)对环己烷氧化的催化活性,并着重探讨了酸助剂的种类及添加量对APM催化活性的影响。 与硝酸相比,乳酸对环己醇转化为环己酮的过程促进作用更强,且使反应物的有效利用率更高,并由此将APM对目标产物的总TON(turn over number)值由124提高到161。     

流光放电等离子体液相氧化亚硫酸铵

在氨-硫铵法烟气脱硫中, 一个关键环节是将副产物的四价硫S(IV)氧化为六价硫S(VI). 采用可规模化的流光放电液相氧化技术, 通过交直流叠加(AC/DC)电源, 激发气体放电产生等离子体对氨法脱硫高浓度的亚硫酸铵进行氧化. 实验测量了该氧化过程与溶液浓度、放电功率密度、溶液pH值、温度以及传质效率因子等各种参数的关系. 研究表明, 在亚硫酸铵摩尔浓度为3 mol·L-1时, 可以获得有实用价值的反应速率, 摩尔能耗减低到50 Wh·mol-1以下, 显示出很好的应用前景.     

多相催化过硫酸盐工艺处理水环境中有机污染物的非自由基过程

20世纪80年代至今,水处理技术中的高级氧化过程(AOP)已被广泛研究及应用。然而水体中的有机污染物仍因种类繁多和降解难易不同困扰着研究者们,因此对于AOP的机理过程需要更深入的分析认识,以利于技术的进一步发展及应用。AOP中的过硫酸盐氧化工艺近年来得到大量关注,其自由基机理的关键活性物种是·OH 和·SO₄^-。非自由基机理分为¹O₂氧化和PS直接氧化(也称电子转移),某些体系中高价态金属也直接或间接地参与氧化过程。但非自由基过程的发生机理及优势特点仍存在争议。本文综述了基于多相催化过硫酸盐高级氧化过程处理水中有机污染物的最新研究,阐述反应机理及其分析手段,并指出当前研究可能存在的问题。对于过硫酸盐高级氧化工艺中非自由基过程的未来研究方向及应用前景提出展望。     

水相中金属有机化学反应的研究进展

本文综述了近年来水相中金属有机化学反应的研究进展, 讨论了该类反应在反应机理、试剂及立体化学等方面的特点, 以及在天然产物全合成和工业生产等方面的应用。