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 radi olysis. The reduction potentials were plotted against the Brown substi tuent constant of the 4-substituent giving straight-lines with slopes close to zero. Aryl methyl chalcogenides with strongly electron-donati ng 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 ionizat ion energies. This comparison shows that the substituent effect on the potential decreases with increasing polarity of the solvent. In addit ion, the redox properties of diaryl, dimethyl and aryl methyl sulfides are compared and discussed.