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

Abstract

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.

Capturing the Elusive [RuV═O]+ Intermediate in Water Oxidation

“…The rhombic EPR signal observed at X-band (ν = 9.106 GHz) frequency for the species To provide evidence for the generation of elusive Ru V from 2 chemically, EPR spectra were recorded for 2 in MeCN in the presence of the two-electron oxidizing agent iodosyl benzene (PhIO) (1:6 ratio of 2 and PhIO; Figures 4 and S21). 69,70 It is evident from the comparison of the EPR spectra of 2 and 2 + PhIO that new EPR signals are formed, which are successfully simulated with the following spin-Hamiltonian parameters; g = [1.905 2.106 2.249]; Voigtian broadening = [2.9 1.9] mT; and HStrain = [0 102 208] MHz, again consistent with S = 1/2 Ru V species. The g-values observed for the electrochemically generated and chemically generated Ru V species are similar but not identical, however, distinctly different from 2.…”

Hypervalent Halogen Compounds in Electrochemical Reactions: Advantages and Prospects

“… [16a] Anodic oxidation of aryl iodides in an undivided batch cell using TFE in the presence of excess nucleophiles (NuH) furnished common hypervalent iodine reagents such as PIDA, (dichloroiodo)arenes, iodosylbenzenes and benziodoxoles. Other researchers have synthesized analogous iodine(III) reagents in the absence of fluorinated alcohols [16b] …”