José R. Romero

Preparation and properties of an electrode coated with a cerium poly(allyl ether p-benzenesulfonate) film for electroorganic reactions

New modified electrodes (ME) were prepared in coating carbon electrodes with cerium poly(allyl ether p-benzenesulfonate) that display reactivity for acetic aldehyde and benzylalcohol oxidation. Electrolysis of benzylalcohol gave benzaldehyde and benzoic acid. These electrodes have been proven to be very stable and resistant and they have the advantage to perform easily in function in the para position of the benzene ring that opens many possibilities for the use of ME of the ion exchange type.

Selectivity in catalytic diol electrooxidation using a polypyridine ru(iv) complex

Abstract 1,2-, 1,3-, and 1,4-Butanediols and phthatic alcohol were oxidized electrocatalytically using the polypyridine [(bpy)(trpy)RuO] 2+ complex ( 1 ) as oxidant under different conditions: concentration of 1 , pH, and temperature. By controlling the number of coulombs passed through the electrolytic cell, it was possible to obtain selective reactions. 1-Hydroxy-2-butanone,1-hydroxy-3-butanone, γ-butyrolactone, phthalide, phtalic aldehyde, and phthalic acid were the products obtained by controlled potential electrolysis from these substrates, with yields ranging from 41 to 89%.

Electrocatalytic oxidation of alcohols, diols and arenes with ceric p-methoxybenzenesulfonate and ceric p-toluenesulfonate

The cerous p-methoxybenzenesulfonate (I) and cerous p-toluenesulfonate (II) mediators were prepared and studied by electrochemical and kinetic methods. The reactivity of several alcohols, diols and arenes in the oxidation reaction with I and II was established, and electrochemical oxidation of some of them was carried out, leading to products with selectivity. The behaviour of these mediators is in agreement with the results of the experiments, and can be explained by the effects produced by the different ligands.

Hidrogenação eletrocatalítica de substratos orgânicos: estudo da eficiência dos metais nobres níquel, paládio e platina usando eletrodos modificados

Nickel, palladium and platinum micro-crystals were dispersed in films covering a vitreous carbon plate electrode by ion exchange followed by electroreduction of their ions. These modified electrodes were used in the electrocatalytic hydrogenation of several substrates of different classes and their efficiency is reported. A comparison among them was performed based on the structural characteristics of the metals. A modified electrode containing platinum showed to be more efficient than a palladium modified electrode and the one of nickel was the less efficient.

Preparation and properties of an electrode with platinum microcrystals dispersed in films of poly(allyl ether p-benzeneammonium derivatives): Electrocatalytic hydrogenation of organic substrates

New modified electrodes were prepared containing platinum microcrystal dispersed in films of poly[allyl ether p-(2-ammoniumethylbenzene)] and poly(allyl ether p-ammoniumbenzene) coating carbon vitreous electrode. They can be used to generate hydrogen from an acid solution and hydrogenation of isosafrole to n-propyl-3,4-methylenedioxobenzene and benzaldehyde to benzylic alcohol with good yields.

OXIDAÇÕES CATALÍTICAS E ELETROCATALÍTICAS DE SUBSTRATOS ORGÂNICOS. O CÉRIO COMO OXIDANTE

This paper reviews the catalytic and electrocatalytic oxidation of organic compounds using cerium (IV) salts. Direct and indirect methods and those using modified electrodes are described.

Oxidações eletrocatalíticas de álcoois e dióis em meio bifásico utilizando metanossulfonato de CeIV como mediador

Some alcohols and diols were oxidized electrocatalytically in a biphasic system using ceriumIV methanesulphonate as mediator. A mixture of methanesulphonic acid solution and benzene was used and aldehydes, ketones and diacids were some of the principal products obtained with yield varying from 27 to 98%. In several cases selectivity was obtained.

Bastões de grafite reciclados de baterias comuns e seu uso como eletrodo modificado em hidrogenação eletrocatalítica de alguns substratos orgânicos

This paper presents some results on the employ of recycled graphite electrode obtained from used common 1.5 V batteries in the preparation of modified electrode and the electrocatalytical hydrogenation of benzaldehyde and of n-valeraldehyde. This inexpensive and easy to obtain electrode was prepared by coating it with a 1:1 mixed film of poly-(allylfenil ether): poly-[allyl p-(2-ethylammonium) benzene ether] and introduction of dispersed platinum particles by ion exchange and reduction of PtCl4-2. Electroreduction of H+ from aqueous H2SO4 using the proposed electrode hydrogenated the substrates in a way comparable with that of vitreous carbon electrode.

Competitive Pathways in the Electrochemical Reduction of Citral

A study of the cathodic reduction of citral at mercury in water/alcohol medium and neutral and basic pH conditions has been carried out using several electrochemical techniques. Controlled-potential coulometric and electrolysis experiments as a function of pH and applied potential showed a monomer/dimer competition. A DISP2 mechanism is proposed. We also make some remarks concerning the literature data about the citral reduction. Our work showed that besides the dimer formation the monomer yield can be improved when proper experimental parameters are chosen.

HIDROGENAÇÃO ELETROCATALÍTICA DE SUBSTRATOS ORGÂNICOS UTILIZANDO ELETRODOS MODIFICADOS POLIMÉRICOS CONTENDO PARTÍCULAS DE Ni/Pd E Ni/Pt

Novel modified electrodes bearing dispersed Pd and Pt particles have been prepared from poly (allyl ether of the p-benzenesulfonic acid) films with incorporated nickel particles making use of galvanic displacement reactions. The SEM analysis of the new modified electrodes revealed efficient deposition of Pd but weak up-take of Pt. Electrocatalytic hydrogenation of several classes of organic substrates were carried out using the MEs Ni, Ni/Pd and Ni/Pt. The Ni/Pd ME showed to be the best of them for the hydrogenation of double, triple and carbonyl bonds. The complete hydrogenation of the aromatic rings for the well-adsorbed substrates acetophenone and benzophenone is noteworthy.