Cs. Visy

Effect of anions on the transient redox behavior of polypyrrole in anhydrous acetonitrile

Abstract The transient redox behavior of polypyrrole in acetonitrile containing 10 ± 1 ppm water has been studied in the presence of the spherical anions ClO 4 − , BF 4 − and PF 6 − by a spectroelectrochemical method. The rate of absorbance changes as well as the transferred charge values registered after different potential steps have been correlated to the radii and association tendencies of the anions participating in the redox process. It is concluded that ‘net’ effect of the dopant can be observed only when hydration of the anions is excluded as far as possible.

Separation of faradaic and capacitive current regions in the redox transformation of poly(3-methylthiophene) with the exclusion of overoxidation processes

Abstract The electrostability of the poly(3-methylthiophene) film prepared in nitrobenzene provided the opportunity to study its redox transformations in an extended anodic potential region with the exclusion of the overoxidation. From spectroelectrochemical results a capacitive region could be separated in the highly oxidized state of the layer which exhibited a large capacitance. This pattern—assumed to be related to charge separation/redistribution within the film at high potential field connected to solvent movements—is promising from the point of view of symmetric p-type/n-type superconductors.

Redox anion doped polypyrolle films; electrochemical behaviour of polypyrrole prepared in Fe(CN)6 solution

Polypyrrole films were formed with hexacyano-ferrate (HCF) anions as exclusive dopants. It was observed that a portion of the built-in HCF displayed reversible electro-chemistry, but the majority of the doping anions are non-electroactive, while they are inside the polymers. Calculations showed that one excess positive charge on the polymer backbone was compensated by one HCF ion, thus, the entrapment of these multivalent anions was accompanied by the inclusion of a large amount of cations as well. These films were sensitive for the size of the cations present in the solution.

Role of chloronium complex in the electrochemical chlorination of c-hexene in nitromethane

Abstract The anodic chlorination of c -hexene in NM solution having 150 ppm water content involves three charge-transfer reactions. The effect of potential on change in product distribution is more effective at the beginning of electrolysis. A mechanism for the process is suggested.

Influence of water content on the product distribution in the electrochemical chlorination of c-hexene in nitromethane

Abstract Effect of water content on product distribution in electrochemical chlorination of c-hexene in nitromethane solution was studied. Formation of 1-chloro, c-hexanone which occurs at the beginning of electrolysis is more effective at lower water content.

Cyclic spectrovoltammetry of conductive polymers

Abstract A new spectroelectrochemical method based on factor analysis of spectra is described and applied to the anodic and cathodic doping of poly(3-methylthiophene). The method reveals the existence of at least three components in both processes. Cathodic doping is greatly dependent on both the cations and the anions used.

Spectroelectrochemical study of the anion effect on the transient redox behavior of poly(N-methylpyrrole) in anhydrous acetonitrile

Abstract Polymerization of N-methylpyrrole and the transient redox behaviour of the polymeric film were studied by spectroelectrochemical methods in the presence of BF4−, ClO4− and PF6− in an acetonitrile solution containing 10 ± 1 ppm of water. The doping levels and the rate of absorbance changes at different potentials were determined and compared with those obtained for polypyrrole. In poly(N-methylpyrrole) BF4− behaves in a similar way to ClO4−, in contrast with polypyrrole. This is interpreted as evidence that the BF4−-polymer interaction in polypyrrole occurs via the NH bonds which are absent in poly(N-methylpyrrole).

The role of water in the electrochemical chlorination of cycloolefins in nitromethane solution

Abstract The effect of water in the electrochemical chlorination of cycloolefins in nitromethane solution has been studied and different aspects of its role as reactant, solvent and inhibitor are discussed. Experimental results led to the conclusion that in the process two intermediates exist, formed with the participation of both atomic and molecular chlorine. First, at low water concentrations, the hydration of chloride ions is dominant; then, at higher concentrations, that of the intermediates is favoured. The extent of hydration was estimated from the potential shift of the oxidation steps after convolution of the current—potential curves. On the basis of the results, a scheme of the electrochemical chlorination of cycloolefins in nitromethane of low water content is suggested where two parallel reaction routes via two hydrated intermediates are considered.

Application of the convolution potential sweep voltammetric method to the chlorine evolution reaction in nitromethane

Abstract The convolution potential sweep voltammetric method was applied to the chlorine evolution reaction on a Pt electrode in nitromethane solution. In agreement with the results of galvanostatic measurements, the process can be described according to a recombination mechanism of the adsorbed Cl∓ atoms. In a smaller range of overpotential, Langmuir-type adsorption is valid, while consideration of lateral interaction extended the validity of the equations to a larger range of overpotential.

Effect of the oxide layer on chloro-ketone formation in the electrochemical chlorination of cyclohexene on Pt electrode

Abstract Experimental evidence is given concerning the oxide layer formation on Pt electrode in wet nitromethane solutions. The results are connected to the possibility of the formation of a chloro-ketone derivative in the electrochemical chlorination of c -hexene.