In situATR-IR spectroscopy: a powerful tool to elucidate the catalytic oxidation of veratryl alcohol in aqueous media

Abstract

The Co(salen) catalyzed oxidation of veratryl alcohol by molecular oxygen in aqueous media was studied by online ATR-IR spectroscopy. The introduction of dioxygen into the reaction mixture initiated the formation of the aldehyde. Only product observed was veratryl aldehyde and its amount was noted to increase linearly with reaction time when reaction conditions are not changed. Addition of NaOH during the reaction increases the reaction rate as the amount of active cobalt species increases. During the reaction a strong vibration is observed in the range of cobalt–oxygen complexes at frequencies 981–993 cm⁻¹. Based on these results we suggest here that in the catalytic oxidation of veratryl alcohol by Co(salen) complexes in basic aqueous solution, a cobalt–superoxo complex is formed, which can oxidize veratryl alcohol to veratraldehyde.