Adsorption Of Derivatives Of The Pyridine Bases
ADSORPTION OF DERIVATIVES OF THE PYRIDINE BASES
ON THE SURFACE OF COPPER ELECTRODE
G.S. Shapoval, A.S. Bandurenko, V.F. Gromovaya
Institute of Bioorganic Chemistry and Petroleum Chemistry, Ukrainian National Academy of Sciences, Murmanska ul. 1, 02094 Kyiv, Ukraine
The interaction of nicotinic acid and its derivatives (nicotinamid and emoxipin) with oxygen and products of its reduction has been investigated by electrochemical methods.
To find out whether the specified reactions proceed in the volume of a solution or on the surface of an electrode adsorption of these compounds and of the oxygen on the copper cathode has been investigated. For this purpose capacity measurements of a double electrical layer of a copper electrode in 0.1М NaCl as a background solution with and without oxygen as well as nicotinic acid and its derivatives in the cathode range of potentials (from 0 V to –1.2 V vs Ag/AgCl) has been carried out. As a result it has been established that without oxygen the dependencies of the capacity of the copper electrode double electrical layer on the potential represent the curves, smoothly rising concerning an axis of abscissa up to potential –0.8 V, followed by much sharper rise of curves. With oxygen the character of curves is similar.
Without oxygen the addition of nicotinamid into the derivative solution does not practically influence the character of curves, while the addition of nicotinic acid or emoxipin causes certain increase of the double electrical layer capacity in the whole investigated range of potentials. The increase of their concentration (from 2×10-4 mol/l to 1.6×10-3 mol/l) results in an additional rise of capacity at potentials -0.5 ¸ -0.7 V. It testifies to the adsorption of these compounds on the electrode surface and of their reorientation with the concentration increase.
With oxygen the general increase of a capacity curve of a background solution is observed as compared with the curve, obtained without oxygen. Oxygen is apparently adsorbed on the surface of electrode. In this case addition of substances, being investigated, practically does not cause changes of the double electrical layer capacity. It allows us to suppose that with oxygen in the given range of potentials the present compounds are not practically adsorbed on the electrode and their interaction with oxygen proceeds not on the electrode surface, but in the diffusion layer of the solution.
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