Liquid-Phase Catalytic Oxidation of Organic Substrates by a Recyclable Polymer-Supported copper(II) Complex

Chloromethylated polystyrene beads cross-linked with 6.5 % divinylbenzene were functionalized with 2-(2′-pyridyl) benzimidazole (PBIMH) and on subsequent treatment with Cu(OAc)2 in methanol gave a polymer-supported diacetatobis(2-pyridylbenzimidazole)copper(II) complex [PS-(PBIM)2Cu(II)], which was characterized by physicochemical techniques. The supported complex showed excellent catalytic activity toward the oxidation of industrially important organic compounds such as phenol, benzyl alcohol, cyclohexanol, styrene, and ethylbenzene. An effective catalytic protocol was developed by varying reaction parameters such as the catalyst and substrate concentrations, reaction time, temperature, and substrate-to-oxidant ratio to obtain maximum selectivity with high yields of products. Possible reaction mechanisms were worked out. The catalyst could be recycled five times without any metal leaching or much loss in activity. This catalyst is truly heterogeneous and allows for easy work up, as well as recyclability and excellent product yields under mild conditions

Effect of Addition of Treated Coir Fibres on the Compression Behaviour of Clay

This paper presents the effect of treated coir fibres (15 mm in length) on the unconfined compressive strength of clay. Dry, sodium hydroxide and carbon tetrachloride–treated coir fibres were used in the study. The coir fibre content was varied from 0.4% to 1.6%. The results indicated that the unconfined compressive strength of clay and clay with dry coir fibres can be increased by treatment with carbon tetrachloride and sodium hydroxide. The increase in unconfined compressive strength was highest with carbon tetrachloride treatment. The clay reinforced with treated fibres was able to bear higher strains at failure as compared to clay and clay with dry fibres. With the increase in coir fibre content (0.4%-1.6%) in clay, there was an increase in the unconfined compressive strength. The clay with treated coir fibres can be used for making bricks for mud houses in rural India

Imidazole Chloramine-B Oxidation kinetics Mechanism Activation parameters Structure reactivity Int

2-(20 -Pyridyl)benzimidazole (PBIMH) was functionalized onto chloromethylated polystyrene beads crosslinked with 6.5 % divinylbenzene, and this solid support was then reacted with Na2PdCl4 in methanol. The functionalized beads were then activated using sodium borohydride. The resultant polymer-supported [2-(20 - pyridyl)benzimidazole]palladium complex (PSDVB– PBIM–PdCl2) and its activated form were characterized by various physicochemical techniques. XPS studies con- firmed the ?2 oxidation state of palladium in the supported complex. The activated complex was found to catalyse the hydrogenation of various organic substrates including olefins, nitro and Schiff base compounds. Kinetic measurements for the hydrogenation of cyclopentene, cyclohexene and cyclooctene were carried out by varying temperature, catalyst and substrate concentration. The energy and entropy of activation were evaluated from the kinetic data. The catalyst showed an excellent recycling efficiency over six cycles without leaching of metal from the polymer support, whereas the unsupported complex was unstable as metal leached out into the solution during the first run

A polymer-supported diacetatobis(2-quinolylbenzimidazole)copper(II) complex as an efficient catalyst for oxidation of alcohols with tert-butyl hydroperoxide

A polymer-supported diacetatobis(2-quinolylbenzimidazole)copper(II) complex PS-(QBIM)2Cu(II) was synthesized by functionalization of chloromethylated polystyrene cross-linked with 6.5 % divinyl benzene with 2-(2â²-quinolyl)benzimidazole and subsequent treatment with Cu(OAc) 2 in methanol. The complex was characterized by physical, analytical and spectroscopic techniques. Electronic and ESR spectra, together with magnetic susceptibility measurements, indicated that the complex was paramagnetic with distorted octahedral geometry around the copper. The complex was found to be active toward oxidation of various alcohols including phenol, benzyl alcohol and cyclohexanol using 70 % aqueous tert-butyl hydroperoxide under mild conditions. Under the optimized reaction conditions, cyclohexanol gave 100 % conversion to cyclohexanone, benzyl alcohol gave 98 % yield of benzaldehyde and phenol gave 89 % yield of catechol and 4 % of hydroquinone. The complex was recycled five times without much loss in catalytic activity. © 2012 Springer Science+Business Media Dordrecht

Polymer immobilized Fe(III) complex of 2-phenylbenzimidazole: An efficient catalyst for photodegradation of dyes under UV/Visible light irradiation

Fe(III) complex of 2-phenylbenzimidazole has been covalently anchored on polymer and characterized by elemental analysis, FT-IR, far-IR, BET surface area measurements, UV-Vis/DRS spectroscopy, thermo-gravimetric analysis and magnetic moment measurements by VSM which confirmed an octahedral environment around Fe(III) in the bound complex. The photocatalytic performance of this complex was evaluated in the photodegradation of dyes in presence of H2O2 as an oxidizing agent. Suitable reaction conditions have been optimized by considering the effects of various reaction parameters such as pH, oxidants, concentration of dye, H2O2 and catalyst for the maximum degradation of dye. The photodegradation was found to be 100 with complete mineralization in 150 min. The comparison of photocatalytic efficiency of the catalyst under visible light, sunlight and dark conditions are accomplished. Comparison between catalytic activity of the polymer-supported complex and unbound complex demonstrated that the polymer-supported complex was more active. Photocatalytic performance of PS-Fe(III)PBMZL was also compared with commercial TiO2 (P25). This heterogeneous complex retained its activity up to 8 runs. A tentative mechanism has been proposed. © 2017 King Saud University

Uncertainties in the Measurements in Differential Scanning Calorimeter and Thermomechanical Analyser

Reproducibility of the output signal in Differential Scanning Calorimeter has been examined in detail. The ordinate calibration factor has been found to diminish at higher temperatures. Calibration factor for enthalpy output has also been evaluated. A procedure for calibrating the area by the proper selection of the base-line for both scanning and isothermal modes of operation has been described. This factor has largely been ignored in the papers published so far. And also the assessment of the performance of Thermomechanical analyser has been done by using AI as expansion standard varying heating rate, sensitivity and load. A simple method for the determination Youngs modulus at room temperature using TMA is also given

Oxidation of Benzyl Alcohols by Polymer Supported V(IV) Complex Using O2

Polymer supported and unsupported oxovanadium(IV) complexes with 2,6-bis(benzimidazolyl)pyridine were synthesized and characterized by elemental analyses, molar conductance, magnetic moment measurements, electronic, IR, ESR spectral studies, LC–MS and thermogravimetric analysis. Based on the results, an octahedral geometry was intended around V(IV) complexes. Polymer-anchored V(IV) complex catalyzed the oxidation of benzyl alcohols in acetonitrile with O2 as an oxidant. Several parameters were differed to optimize the reaction conditions. Under the optimized reaction conditions, benzyl alcohol oxidation confirmed 96% conversion with 100% selectivity towards benzaldehyde. The developed catalyst revealed excellent benzyl alcohol oxidation at moderate temperature in presence of oxygen making the reaction simpler and environmentally benign. The polymer anchored V(IV) complex showed excellent recyclability as compared to its unsupported analogue