Ultrasound-assisted one-pot synthesis of 2,4,5-triarylimidazole derivatives catalyzed by ceric (Ⅳ) ammonium nitrate in aqueous media

2,4,5-Triarylimidazoles could be obtained in excellent yields by the one-pot three-component condensation of benzil/benzoin, aldehydes and ammonium acetate in the presence of catalytic amount of the inexpensive, readily available and non-toxic ceric （IV） ammonium nitrate （CAN） in aqueous media under ultrasound at room temperature. In this reaction the products were obtained in short reaction time and easy operation under mild conditions.

Optimization of Ceric Ammonium Nitrate Initiated Graft Copolymerization of Acrylonitrile onto Chitosan

In the present work, graft copolymerization of polyacrylonitrile onto chitosan has been carried out in the presence of ceric ammonium nitrate redox initiator. Optimization of grafting of polyacrylonitrile onto chito-san was performed by varying the process parameters such as ceric ammonium nitrate (CAN) concentration, polyacrylonitrile concentration and reaction time to study their influence on percent grafting and grafting ef-ficiency. The optimum reaction conditions obtained for grafting of acrylonitrile onto chitosan were reaction time 55 mins, CAN concentration 1% in Con. HNO3, and polyacrylonitrile concentration 0.75 mol/L. The characterization of the grafted products by means of FTIR, thermal analysis, X-ray diffraction and scanning electron microscopy furnished the evidence of grafting of polyacrylonitrile onto chitosan.

GRAFTING OF ACRYLAMIDE ONTO SURFACE OF COPOLYMERS CONTAINING P-TOLYLCARBAMOYL PENDANT GROUP INITIATED WITH CERIC SALT

Two copolymers containing p-tolylcarbamoyl pendant group poly (MAMT-co-VAc) and poly(MAMT-co-MA) were synthesized f and the graft copolymerization of AAM onto these two func-tional copolymers films initiated with ceric salt were carried out in aqueous solution for variousperiods at 30℃. The formation of graft copolymer was verified by water absorption, ESCA andSEM photographs. Based on the results of the study of the initiation mechanism of model com-pounds and ceric salt systems, the reaction mechanism of the graft copolymerization initiated withceric salt was proposed.

VINYL RADICAL POLYMERIZATION INITIATED WITH CERIC ION AND ETHYL N, N-DIETHYLDITHIOCARBAMYL ACETATE SYSTEM

Acrylamide polymerization initiated with a redox initiation system consisting of eerie ion and ethyl N,N-diethyldithiocarbamyl acetate (EDCA) has been studied. It was found that the polymerization rate equation is in good agreement with that of a redox initiated polymerization, and the overall activation energy of the polymerization was determined to be 25.2 kJ.mol(-1). Accordingly, the system belongs to a redox initiator. The initiation mechanism was proposed based on the end group analysis using FT-IR, UV spectroscopies. Analysis results revealed that the N, N-diethyldithiocarbamyl radical produced from the redox reaction of EDCA with eerie ion can initiate acrylonitrile (AN) polymerization and form the end group on PAN. The resulting PAN was photopolymerized with butyl acrylate (BE) to form PAN-b-PBA block copolymer.

Initiation Mechanism of Polymerization of Acryl－amide by Ceric Ion／2－Benzoyl Acetanilide System

he initiation mechanism of ceric ion/2-benzoyl acetanilide system was studiedby means of FT-IR, EPR and kinetic studies which revealed that 2-benzoyl ac-etanilide acts as a very active promotor to the polymerization initiated by ceric ion.The initiation mechanism was then proposed which involved the complex formationbetween a ceric ion and a l ,3-diketone group or a carbamate group, followed by,thedecomposition of the complex to generate C-centered secondary alkyl radical and N-centered anillido radical, both of which would initiate polymerization of vinylmonomer as the end groups of the polymers formed.

GRAFT POLYMERIZATION OF ACRYLAMIDE ONTO HOMOPOLYMER OF 5-METHYL-5-HEXEN-2, 4-DIONE INITIATED BY CERIC ION

The homopolymerization of 5-methyl-5-hexen-2,4-dione (methacryloylacetone, MAA), a vinyl monomer having beta-diketone group, was carried out in the presence of benzophenone (BP)/N, N-dimenthyl-4-toluidine (DMT) system. Graft polymerization of acrylamide initiated by eerie ion onto the homopolymer film was investigated and the mechanism of the grafting reaction was proposed on the basis of ESR study. The grafted copolymer was characterized by means of grafting percentage, water absorption, XPS spectra and scanning electron photomicrographs.

Ceric(Ⅳ)-mediated Oxidative Addition of 1,3-Dicarbonyl Compounds to MCPs:A Facile Access to Dihydrofuran Derivatives Incorporating Cyclopropyl Groups

Alkylidenecyclopropanes undergo ceric（Ⅳ） ammonium nitrate （CAN）-mediated addition reaction with 1,3-dicarbonyl compounds leading to dihydrofuran derivatives incorporating cyclopropyl groups in moderate yields.

STUDIES ON THE INITIATION MECHANISM OF CERIC ION AND ACETYLACETONE REDOX SYSTEM IN VINYL POLYMERIZATION

The initiation mechanism of acrylamide (AAM)polymerization using ceric ion/acetylacetone system as an initiator has been studied. The redox polymerization was revealed by the low value of overall activation energy of AAm polymerization. The structure of free radicals formed from above-mentioned initiation sytem were detected by radical trapping and ESR spectra techniques and the end groups of polymers obtained were determined by FT-IR spectra analysis method. Based on these results the initiation mechanism is proposed.

VINYL RADICAL POLYMERIZATION INITIATED WITH CERIC ION AND N-(SUBSTITUTED PHENYL) ACETAMIDE SYSTEMS

The polymerization of acrylamide (AAM)in H_2O/DMF or in H_2O/CH_3CN mixed solvent initiated with ceric ion (Ce^(4+) )/N-(substituted phenyl)-acetamide systems have been studied. The redox polymerization was revealed by the low value of overall activation energy (E_α) of AAM polymerization using ceric ion/N-(substituted phenyl) acetamide system as an initiator. The end group of polymer formed was detected by IR spectrum analysis method, it revealed the presence of N-(m-acetoxy-methylphenyl) acetamide (m-AAe) moiety end group in the polymer obtained with ceric ion/m-AAe initiation system.

PHOTOSENSITIVITY OF CERIC ION INITIATED METHYL ACRYLATE POLYMERIZATION

The polymerization of methyl acrylate was sensitive to UV light. Under UV light,the rate of polymerization is 8 times as high as the rate in dark.The overall activation energy was decreased by the UV light (313nm).A tentative explanation is given and the mechanism is discussed.

STUDIES ON THE KINETICS AND INITIATION MECHANISM OF ACRYLAMIDE POLYMERIZATION USING CERIC/ACETOACETANILIDE SYSTEM AS INITIATOR

It is found that acetoacetanilide possesses very high promoting reactivity towards ceric ion in initiating polymerization of vinyl monomer. The kinetics of acrylamide polymerization and the activation energies were studied. The initiation mechanism of ceric/acetoacetanilide is proposed on the basis of experimental results of FT-IR and ESR.

A New Method for the Cleavage of Carbohydrate Benzylidene Acetal by Ceric (IV) Ammonium Nitrate in CH_3CN-H_2O (10: 1)

A new method for the cleavage of carbohydrate benzylidene acetal has been developed using Ceric (YV) ammonium nitrate (CAN) [(NH4)2Ce(NO3)6] in CH3CN-H2O (10/1, v/v).

The Influence of Ceric Oxide on Phase Composition and Activity of Iron Oxide Catalysts

The process of dehydrogenation of methyl butenes to isoprene is conducted in the presence of iron oxide catalysts whose composition may include oxides of alkaline metals, alkaline earth metals, and transition metals. Catalysts of latest generation can also contain oxides of rare earth elements, particularly cerium oxide. However there is no any common opinion concerning its effect on catalytic properties of iron oxide catalysts. It is well known that ceric oxide has a positive effect on the quantity and stability of active centers and can play a critical role in a redox cycle of the dehydrogenation process. By means of differential thermal analysis, dispersion analysis and X-ray phase analysis, it was found in present study that introducing of ceric oxide promotes the decrease in hematite crystallite sizes. At the same time, it prevents potassium polyferrites formation, with the equilibrium of topochemical reaction between ferric oxide and po tassium carbonates moving predominantly to the formation of intermediate products–monoferrite systems, having greater catalytic activity. The increase in potassium monoferrite content results in dispersion of particles in the Fe2O3-K2CO3-СеО2 system that is accompanied by modification of texture characteristics. For this catalyst composition, the optimum concentration of ceric oxide (8.7 wt.%), leading to the formation of a certain ratio of mono- and polyferrite phases, was found. If more than 8.7 wt.% of СеО2 is introduced, the modification of texture characteristics of catalyst samples takes place, that negatively affects their selectivity.

RADICAL POLYMERIZATION OF VINYL MONOMER INITIATED BY CERIC ION/TARTARIC ACID

The polymerization of acrylamide and acrylonitrile using ceric ion as initiator can be promoted greatly by the tartaric acid. The kinetics of acrylamide polymerization initiated by ceric ion/tartaric acid has been studied. The presence of the species of tartaric acid in Polyacrylonitrile produced by using ceric ion/tartaric acid as niitiator has been confirmed by FT-IR analysis.

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 reason- able 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.

新型绿色荧光粉CeO_(2):Mn(Ⅱ)的发光性能研究

以氧化铈和碳酸锰为主要原料、氧化铝作分散剂,采用高温固相法在碳还原气氛中首次合成一系列掺杂量为0.01~0.04的Mn掺杂CeO_(2)绿色荧光粉(CeO_(2):Mn^(2+)),并分析试样的晶体结构、粒径、形貌和发光性能。结果表明:制得的CeO_(2):Mn^(2+)荧光粉为立方萤石结构,分散剂氧化铝的加入能够避免主晶格CeO_(2)的烧结并促进发光中心的掺杂,氧化铝不会明显改变试样的晶体结构。试样的粒径集中在6~10μm范围内,颗粒的外形为椭球形和条形。荧光光谱显示,掺杂发光中心Mn^(2+)后,该荧光粉在272 nm紫外光激发下能够发出519 nm高强绿光,其中,CeO_(2):0.033Mn试样的发光性能最佳。该CeO_(2):Mn^(2+)绿色荧光粉在显示和照明领域具有良好的应用前景。

Ceric ammonium nitrate supported HY-zeolite:An efficient catalyst for the synthesis of 1,8-dioxo-octahydroxanthenes

Ceric ammonium nitrate （CAN） supported HY-zeolite has been used as an efficient catalyst for the one- pot synthesis of 1,8-dioxo-octahydroxanthenes from the readily available 1,3-diketone and aromatic aldehydes under solvent-free conditions. The present methodology is cost-effective in addition to other advantages like high yields of products in shorter reaction time and simple workup procedure without the use of any injurious solvents.

不同形貌CeO_(2)催化剂用于CO催化氧化研究

为了探究具有不同形貌的CeO_(2)催化剂在CO催化氧化反应中的性能差异,对反应物中的有机配体富马酸的添加量进行调控,通过煅烧获得了片型CeO_(2)、哑铃型CeO_(2)和雪花型CeO_(2)。采用XRD、Raman和SEM测试对三种催化剂的微观结构和形貌进行分析。采用CO催化氧化装置评价了三种催化剂的性能,结合XPS和H2-TPR表征结果分析了雪花型CeO_(2)性能较为优异的主要原因。高结晶性的雪花型CeO_(2)含有丰富的氧空位和活性氧,结合其纳米片自组装的特殊形貌,在催化反应中表现出最低转化温度。

采用不同方法制备CeO_2超细粒子——Ⅰ.溶胶——凝胶法

采用以柠檬酸为配体的溶胶———凝胶法制备了 Ｃｅ Ｏ２ 超细粒子．考察了不同制备条件（ 金属离子与配体的摩尔比、反应温度、ｐ Ｈ、凝胶烘干温度、焙烧温度及时间） 对粒子的影响，获得了最佳的制备条件：金属离子与配体的摩尔比为１ ：３ 、反应温度为６５ ℃、ｐ Ｈ＜ ０（ 未调） 、凝胶烘干温度为６５ ℃、３２０ ℃焙烧温度２ｈ ．并在该条件下成功地制得了均匀分散的 Ｃｅ Ｏ２ 超细粒子（ 平均粒径为１０ｎｍ ，比表面为５７ ｍ ２／ｇ） ．