โ Scribed by W. Smit
No coin nor oath required. For personal study only.
CONWAY and Vijh'l have sharply criticised Eberson's2 attempt to calculate electrode potentials for the possible individual steps of the Kolbe reaction. According to them Eberson's treatment is fundamentally incorrect since the role of the electrode metal surface as an adsorbent for intermediates and as a catalyst for successive steps involving such intermediates has been completely neglected. In his defence, Eberson3 argues that mechanisms involving reactions between adsorbed radicals lead to wrong predictions about the stereochemistry of the products. The formation of optically inactive coupling products from optically active acids on Kolbe electrolysis is, according to Eberson, an indication of the formation of nonadsorbed intermediates. In the mechanism proposed by him he considers the electrode surface to become conditioned by the formation of an oxide film, which in his view does not participate further in the electrode reaction.
Conway and Vijh's* explanation of the formation of optically inactive products from optically active acids without the radicals becoming completely free must be considered rather unconvincing.
A support for the non-adsorbed intermediates postulated by Eberson may be derived from the steady-state measurements on platinum, gold and palladium anodes in nominally anhydrous potassium-acetate-acetic-acid solutions reported by Salzberg, Barnett and Kandler.6 These investigators concluded that above 10-4-lo6
A/cm2 a film of adsorbed acetic acid molecules is formed, on which the irreversible oxidation of molecular acetic acid proceeds.
Although not stated explicitly by them, their conclusions must imply that the intermediates are formed in a non-adsorbed state and, moreover, that the adsorbed film does not react with these intermediates.
We have come to analogous conclusions in our investigation of the formation of persulphate. 6 This investigation is based on the determination of current efficiencies and potentials at constant temperature and at various constant cds in dependence on the concentration of the sulphur-containing species in the solution.
For measuring the current efficiencies it has appeared essential to wait until the anode potential has reached a steady value, as in Salzberg's investigation.
We have concluded that at sufficiently high potentials a platinum anode placed in a sulphate-containing solution becomes covered by sulphate species, the oxidecovered platinum becoming limited to isolated patches.
These adsorbed sulphate species do not practically participate further in persulphate formation.
On the sulphate-covered parts, SOd2-ions are discharged (not HS04-ions as has almost generally been assumed hitherto).
The intermediates are formed in a non-adsorbed state and must considered to be free radicals as opposed to the assumption of Russian investigators. '
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I am a Virtue. Our kind is under attack and we are having to pull double duty to protect the earth as well as search for the ones who are attacking us from the inside. When I meet him, I mistakenly assume he is not one who deserves my protection. The way he makes me feel, is not the least bit virtuo