REDOX PROPERTIES OF 4-SUBSTITUTED ARYL METHYL CHALCOGENIDES IN WATER

The one-electron reduction potentials of 14 4-substituted aryl methyl chalcogenide radical cations in water have been measured by pulse radiolysis. The reduction potentials were plotted against the Brown substituent constant of the 4-substituent giving straight-lines with slopes close to zero. Aryl methyl chalcogenides with strongly electron-donating substituents deviated markedly from the general trend indicating a different nature of the radical cation. The results are compared with electrochemical results in organic solvents and with gas-phase ionization energies. This comparison shows that the substituent effect on the potential decreases with increasing polarity of the solvent. In addition, the redox properties of diaryl, dimethyl and aryl methyl sulfides are compared and discussed.