Chemical and electrochemical oxidations in two phases

Tait, Stephen John David (1981) Chemical and electrochemical oxidations in two phases. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

This thesis examines the oxidation of a range of organic compounds by dichromate and persulphate in organic media using phase transfer catalysis. The electrogeneration of both oxidising agents has been investigated with a view to linking it to the organic oxidation. Dichromate is found to oxidise a wide range of alcohols to carbonyl compounds both rapidly and in high yield. The reactions are shown to be sensitive to changes in pH, reaction stoichiometry and the presence of a phase transfer catalyst. Some aromatic hydrocarbons can also be oxidised in good yield by the same method. Similar studies using persulphate show that its reactions in organic media are very slow but many organic compounds, particularly methylbenzenes, can be oxidised to their aldehydes in high yield in the presence of a AgN03 catalyst. The reaction probably occurs at the water/organic interface and the rate and selectivity of the oxidation is found to depend on the A & (i) concentration, temperature and mixing conditions. Conditions for the high current densities and efficiencies for the electrogeneration of dichromate on lead dioxide were also defined by altering parameters such as temperature, substrate concentration, electrolysis potential and surface preparation. The effect of the latter prompted a separate study of the formation of lead dioxide on antimonial lead by several methods. Cyclic voltamietry and electron microscopy were used to investigate the resulting Pb02 layers. Satisfactory conditions for the generation of persulphate on a platinum anode were achieved by a similar study. Attempts to combine the electrochemical and organic reactions in a 'one-pot' reactor were not successful.

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