1973 Volume 46 Issue 1 Pages 147-152
The behavior of ammonia and several amines at the dropping mercury electrode was studied in N,N-di-methylformamide containing 0.10M Et4NClO4 by means of DC polarography and amperometric titration. Ammonia gave a diffusion-controlled anodic wave, which was attributed to the reversible oxidation of mercury to the 1:2 complex of mercury(II) with ammonia. A dilute solution of methylamine or dimethylamine gave a diffusion-controlled anodic wave similar to that of ammonia. A concentrated solution of each amine gave a prewave due to the adsorption of the electrolysis product, Hg(am)22+, on the electrode surface. Trimethylamine also gave an anodic wave, but it was attributed to the oxidation of the amine itself to the corresponding cation radical. Ethylenediamine and 1,2-diaminopropane each gave a well-defined anodic wave over the concentration range examined. The wave was diffusion-controlled and was attributed to the reversible oxidation of mercury to the chelate compound of the Hg(diam)22+ type. No adsorption phenomena were observed in this case. Aromatic amines such as aniline and β-naphthylamine gave no anodic waves. The overall stability constants of the 1:2 complexes of mercury(II) with ammonia, methylamine, dimethylamine, ethylenediamine, and 1,2-diaminopropane were evaluated by the analyses of the waves to be 1016.9, 1017.1, 1015.0, 1023.5, and 1024.0M−1 respectively.
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