ELECTROCHEMISTRY IN LIQUID SO2 .9. OXIDATION OF N-ALKANES AND ALKYLAMMONIUM IONS AT PT ULTRAMICROELECTRODES IN LIQUID SO2

When csAsF6 is used as the supporting electrolyte in liquid SO2 the anodic solvent limit is about +6V vs. SCE. This very positive potential range allows the electrochemical oxidation of straight-chain hydrocarbons [CnH2n+2(n = 1-8)] and quaternary alkylammonium ions [R4N+(R = C2nH2n+1n - 3-16)] to be studied in this solvent system by cyclic voltammetry at Pt ultramicroelectrodes (10 and 25 µm). Single, totally irreversible, anodic voltammetric waves were observed. The peak potentials of these compounds became more negative with an increase in the length of the carbon chain. The peak potentials correlated with ionization potentials and the length of the carbon chain. Bulk electrolysis of n-hydrocarbons at low concentrations (1-5 mM) required 2 faradays per mole of hydrocarbon. However, when higher concentrations were employed (>10 mM), the electrolytic current did not fall to background levels. Some delocalization of the C σ—σ bonds is proposed to account for the negative peak potential shift with increasing length of the hydrocarbon chain. copyright. © 1990, The Electrochemical Society, Inc. All rights reserved.