Presence Of Ammonium Peroxydisulfate Research Articles

Sonochemical-assisted synthesis of nano-structured lead dioxide

PbO2 nano-powder was synthesized by the ultrasonic irradiation of an aqueous suspension of dispersed β-PbO, as precursor, in the presence of ammonium peroxydisulfate as an oxidant. The reaction rate increased with an increase in temperature and ammonium peroxydisulfate concentration. In the presence of ammonium peroxydisulfate, the increased concentration of hydroxyl radical facilitated the oxidation of β-PbO to PbO2 under ultrasonic irradiation. The PbO2 nano-powder was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the applied ultrasonic wave determines the particle size. PbO2 samples prepared under optimized experimental conditions have lead dioxide particles in the range of 50–100nm, as shown by SEM. The XRD results reveal that only β-PbO2 is formed under optimum conditions. When the reaction mixture was stirred instead of ultrasonically irradiated, only a fraction of the lead oxide was converted to lead dioxide, and lead sulfate was the main reaction product.

Synthesis and morphological characterization of PMMA/polyaniline nanofiber composites

Poly (methyl methacrylate) (PMMA)/Polyaniline nanofibers composite films were prepared by solution casting. Doped polyaniline self-assembled nanofibers (PANFs) were synthesized by interfacial polymerization performed in an aqueous HCl/dichloromethane biphasic system in the presence of ammonium peroxydisulfate as oxidant agent. Sodium dodecyl sulfate (SDS) was added to the organic phase in order to verify possible modification the morphology the nanostrucutures when compared with previous reports. Treatment in an ultrasonic bath of PANFs on butanone resulted in a green dispersion (up to 250mg/dL). Dispersed PANFs were then combined with PMMA/butanone solution. Additional sonication and posterior film cast from solution procedures resulted in slight green PMMA/PANFs 0.15–0.30% (wt/wt) composite films. Film composites were characterized by UV–Vis spectroscopy and Scanning Electron Microscopy (SEM). PANFs powder was investigated by (SEM).An investigation by viscosity method on molecular structure of neat PMMA exposed to ultrasonic irradiation up to 2h showed small change (<5%) in the viscosity-average molar mass, Mv (≈100kg/mol). It suggests that mechanical degradation by cavitation does not occur on PMMA under those conditions. Thus, ultrasonic bath treatment is a simple, accessible method for mitigating solubility problems of PANI doped with inorganic acids and improving quality of low concentration PMMA/PANI composites. Application of these composites relies on the radiolytic stabilization effects of PANI on PMMA matrix.

Solution properties of gas-phase-polymerized sodium acrylate microparticles. I. Influence of coinitiators

A partially neutralized sodium acrylate (NaAc) monomer was polymerized in the gas phase in the presence of ammonium peroxydisulfate [(NH4)2S2O8] as the primary initiator and zinc acetate (ZnAc) as the coinitiator. The effect of the coinitiator on the solution properties of the spray-polymerized product was investigated for the conversion percentage as a function of (1) the primary initiator (NH4)2S2O8 concentration, with the concentration (14.8% with respect to the monomer) of the coinitiator kept constant; (2) the coinitiator (ZnAc) concentration, with the primary initiator concentration (4% with respect to the monomer) kept constant; and (3) the reaction temperature. The viscosity of the product as a function of the coinitiator concentration was also investigated. The conversion percentage of gas-phase-polymerized NaAc increased by approximately 8% (i.e., from 91.6 to 99.3%) with an increasing (NH4)2S2O8 concentration (0.5–5% with respect to the monomer). The conversion percentage as a function of the coinitiator concentration (0–15% with respect to the monomer) increased by 25% (from 75 to 100%). When the concentrations of the initiators (NH4)2S2O8 and ZnAc were kept constant at 4 and 14.8% (with respect to the monomer), respectively, the conversion increased from 48 to 83% when the reaction temperature was increased from 100 to 140°C. The viscosity (at 20°C) of sodium polyacrylate decreased with an increasing coinitiator concentration. The relative rate of polymerization, as a function of the pH of the polymer, showed a minimum at pH ≈ 6 and subsequently increased steeply, reaching a plateau at pH ≈ 11; it then decreased again very sharply. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1034–1043, 2003

Post-column reaction detection system for the determination of organophosphorus compounds by liquid chromatography

The development and application of a post-column reaction detection system for organophosphorus compounds based upon theri photodegradation to orthophosphate followed by the formation of reduced heteropolymolybdate is reported. Photodegradation occurs in a fused-silica tube coiled about a 450-W xenon lamp in the presence of ammonium peroxydisulfate. Photodegradation yields were practically quantitative for the organophosphates, -phosphonates, and -phosphorodithioates tested. Factors affecting the rate of the chromogenic reaction were optimized so that its contibution to the total band-broadening was negligible. The effect of intefering organic modifiers in the mobile phase was studied using the acetate ion as a model. Separations were developed using no organic solvents in the mobile phases. The determination of dialkylphosphates in urine and organophosphorus pesticides in tomatoes illustrate the potential of the methodology.

過硫酸アンモニウム存在下におけるQuinolinium Perchlorate類のα-オキシアルキル化反応

共通した電子的寄与が期待されるキナルジンあるいはレピジンの4種の誘導体, すなわち遊離塩基の過塩素酸塩, N-オキサイド, N-オキサイドの過塩素酸塩, およびN-オキサイドの四級塩（N-ethoxy体）を用い, 過硫酸アンモニウム存在下ジオキサンによる, homolytic α-oxyalkylationを検討した. その結果をまとめると次のとおりである：1）いずれの場合もhomolytic oxyalkylationが生起し, キノリン核の2あるいは4位にジオキサンが導入される. 2）遊離塩基の過塩素酸塩およびN-オキサイドの四級塩（N-ethoxy体）とも高収率で反応するが, 後者の方が好結果を与えた. 3）N-オキサイドも低収率ながら反応し, N-オキサイド基を保持した生成物を与える. 以上の事実より, N-アルコキシあるいはN-オキソ-1,2-ジヒドロキノリンラジカル中間体を含む反応コースを推定した. また, homolytic hydroxymethylationに関しては遊離塩基の過塩素酸塩はN-ethoxy体よりもやや反応性がまさっているが, 両者とも定量的にhydroxymethyl体を生成した.