Oxidation Of 4-methoxybenzyl Alcohol Research Articles

Synthesis of hollow shell TiO2 nanostructures enclosing Au nanoparticles and evaluation of their photoelectrocatalytic activity

Titania hollow shell structures enclosing Au nanoparticles (NPs) Void@Au@TiO2 were synthesized and applied for photoelectrochemical and chemical catalysis. SiO2 nanospheres were first synthesized to be used as templates for the nanostructures. These SiO2 nanospheres were then functionalized with gold nanoparticles (Au NP) using a bifunctional linker APTES [(3-Aminopropyl)triethoxysilane]. A titania coating was carried out on these Au-decorated SiO2 spheres, followed by calcination to enhance the crystallinity of these SiO2@Au@TiO2 structures. Thereafter, the SiO2 template was etched out using NaOH leaving behind Au NPs encapsulated in TiO2 hollow shell nanospheres Void@Au@TiO2. These structures were characterized by using TEM, XRD, UV–Vis-DRS, Raman and FTIR spectroscopy. The catalytic activity was evaluated using the selective oxidation of 4-methoxy benzyl alcohol as a test reaction. Further the photo-electrocatalytic activity of these nanostructures was evaluated.

Single-Atom-Based Vanadium Oxide Catalysts Supported on Metal–Organic Frameworks: Selective Alcohol Oxidation and Structure–Activity Relationship

We report the syntheses, structures, and oxidation catalytic activities of a single-atom-based vanadium oxide incorporated in two highly crystalline MOFs, Hf-MOF-808 and Zr-NU-1000. These vanadium catalysts were introduced by a postsynthetic metalation, and the resulting materials (Hf-MOF-808-V and Zr-NU-1000-V) were thoroughly characterized through a combination of analytic and spectroscopic techniques including single-crystal X-ray crystallography. Their catalytic properties were investigated using the oxidation of 4-methoxybenzyl alcohol under an oxygen atmosphere as a model reaction. Crystallographic and variable-temperature spectroscopic studies revealed that the incorporated vanadium in Hf-MOF-808-V changes position with heat, which led to improved catalytic activity.

Facile two-step preparation of polystyrene/anatase TiO2 core/shell colloidal particles and their potential use as an oxidation photocatalyst

Titania and materials containing titania have received considerable attention due to their technological importance in many areas. In this study, anatase crystalline titania (TiO2) coated polystyrene (PS) colloidal particles were successfully prepared in two easy steps. First, a one pot synthesis of the colloidal particles was produced via an emulsifier-free emulsion copolymerization of styrene (S) and 2-(dimethylamino)ethyl methacrylate (DMA) at pH 4.0. In the second step, the synthesized particles were coated by titania using a sol–gel process in-situ hydrolysis and a condensation reaction of titanium(IV) isopropoxide in an acidic aqueous solution. In this way, anatase crystalline titania, rather than the usual amorphous form, was obtained as a shell on the PS colloidal particles. Both the PS colloidal particles and the polystyrene/anatase titania (PS/TiO2) core/shell colloidal particles had monodisperse morphology and were characterized using SEM, Zetasizer, FTIR, XRD and TGA techniques or measurements. In addition, the photocatalytic activity of the PS/TiO2 core/shell particles was tested for the first time in an oxidation reaction, in the oxidation of 4-methoxybenzyl alcohol (MBA) with O2 in water. Much higher selectivities of the target product, p-anisaldehyde (AA), were obtained with the PS/TiO2 core/shell particles than with a commercial anatase crystalline TiO2.

Simple cyclodextrin aldehydes as excellent artificial oxidases

Cyclodextrin based oxidases, with a ketone as functional group are well known as good artificial enzyme mimics (Fenger et al. Org Biomol Chem 7:933–943; Marinescu and Bols Angew Chem Int Ed 45:4590–4593; Bjerre et al. Eur J Org Chem 704–710; Marinescu et al. J Am Chem Soc 127:17578–17579). We here report a series of modified cyclodextrins, having aldehydes as functional groups. The aldehyde based artificial enzymes have, in most cases, better catalysis than the ketones, because of their powerful covalent binding of hydrogen peroxide. Among the modified cyclodextrins studied are mono and di aldehydes on the 6 positions, with or without methylated hydroxyl groups. The aldehyde functionality was also introduced close to the secondary side, by attaching ethoxy-2-al or propoxy-3-al to the 2 position. The modified cyclodextrins showed excellent enzymatic activity towards oxidation of different aminophenols, and 4-methoxy benzyl alcohol with hydrogen peroxide as a stoichiometric oxidant. Rate enhancements up to 4,600 were achieved for oxidation of 4-methoxy benzyl alcohol, where as oxidation of amines gave rate enhancements up to 3,400. The artificial oxidases catalyses oxidations under enzymatic conditions (water, pH 7, 25 °C), following Michaelis–Menten kinetics. To confirm the enzyme activity, inhibition studies with sodium naphthalene-2-sulfonate were carried out. These studies showed competitive inhibition of the enzymes, verifying the cyclodextrins enzyme like character.

Water-soluble manganese(III) salen complex as a mild and selective catalyst for oxidation of alcohols

Abstract Dicationic Mn(III) salen, containing phosphonium groups at 5,5′-positions of salen ligand, was used as an efficient and selective catalyst for oxidation of alcohols to their corresponding aldehyde or ketone derivatives at room temperature in good to excellent yields. The effect of different solvents was studied in the oxidation of 4-methoxybenzyl alcohol, CH3CN/H2O was better solvent. Also the effect of the oxygen donors such as NaIO4, Bu4NIO4, Oxone, H2O2, H2O2/urea, NaOCl and tert-BuOOH was studied in the oxidation of 4-methoxybenzyl alcohol and selected NaIO4 as oxygen donor.

Comparing the catalytic efficiency of some mediators of laccase

The mechanism of oxidation of non-phenolic substrates by laccase/mediators systems has been investigated. Oxidation of 4-methoxybenzyl alcohol ( 1), taken as a benchmark reaction, enabled us to compare and to rank the relative ability of twelve mediators: TEMPO proved most effective, and a ionic mechanism is suggested for its action. Data on intermolecular selectivity of substrate oxidation are in favour of an electron transfer (ET) mechanism in the case of ABTS-mediated oxidations, and of a radical mechanism in HBT- and HPI-mediated reactions. Investigation by cyclic voltammetry (CV) of some of the mediators revealed that an important role in determining the mechanism of substrate oxidation may be played by the stability of the oxidised form of the mediator, as well as by its redox potential.