Anodic Oxidation of Iodobenzene and Iodobenzoic Acids in Acetic Acid Environment – Electrochemical Investigation and Density Functional Theory Study

Kinetic and mechanistic aspects of an anodic oxidation of iodobenzene and its selected derivatives leading to the corresponding iodosyl compounds, were investigated in anhydrous acidic acetic acid environment using boron-doped diamond electrode. The first electron removal leading to the formation of radical cation was identified as the rate determining step of the process. Oxidation potential values of the investigated compounds were rationalised by their solution phase ionisation energies (in conformation of the radical cations as products of the first electron removal), calculated by advanced DFT methods. Unexpectedly low oxidation potential of 2-iodobenzoic acid and its functional derivatives compared to iodobenzene, 3-iodo and 4-iodobenzoic acids was explained by decreased electron density at iodine atom leading to planar 2-iodobenzoic acid radical cation. This is connected with reordering of its frontier molecular orbitals compared to non-planar neutral molecule.