Highly efficient oxidation of alcohols using Oxone® as oxidant catalyzed by ruthenium complex under mild reaction conditions

HOO• as the Chain Carrier for the Autocatalytic Photooxidation of Benzylic Alcohols

The oxidation of benzylic alcohols is an important transformation in modern organic synthesis. A plethora of photoredox protocols have been developed to achieve the aerobic oxidation of alcohols into carbonyls. Recently, several groups described that ultraviolet (UV) or purple light can initiate the aerobic oxidation of benzylic alcohols in the absence of an external catalyst, and depicted different mechanisms involving the photoinduction of •O2- as a critical reactive oxygen species (ROS). However, based on comprehensive mechanistic investigations, including control experiments, radical quenching experiments, EPR studies, UV-vis spectroscopy, kinetics studies, and density functional theory calculations (DFT), we elucidate here that HOO•, which is released via the H2O2 elimination of α-hydroxyl peroxyl radicals [ArCR(OH)OO•], serves as the real chain carrier for the autocatalytic photooxidation of benzylic alcohols. The mechanistic ambiguities depicted in the precedent literature are clarified, in terms of the crucial ROS and its evolution, the rate-limiting step, and the primary radical cascade. This work highlights the necessity of stricter mechanistic analyses on UV-driven oxidative reactions that involve aldehydes' (or ketones) generation.

Highly efficient degradation of ofloxacin by UV/Oxone/Co2+ oxidation process

INTRODUCTION

In this study, UV/Oxone/Co(2+) oxidation process was applied to degradation of ofloxacin (OFL) in the presence of Co(2+) as the catalytic and Oxone as the oxidant. The operation parameters including pH, temperature, dosages of reagents, and reaction time were studied in detail.

RESULTS

The results showed that the optimum conditions for the UV/Oxone/Co(2+) processes were determined as follows: temperature = 25°C, pH = 5.0, [Oxone] = 0.6 mmol/L, [Oxone]/[Co(2+)] = 1,000, and reaction time = 60 min. Under these conditions, 100% of the OFL degraded. The kinetics was also studied, and degradation of OFL by the UV/Oxone/Co(2+) process could be described by first-order kinetics.

CONCLUSIONS

Mineralization of the process was investigated by measuring the total organic carbon (TOC), and the TOC decreased by 87.0% after 60 min. This process could be used as a pretreatment method for wastewater containing ofloxacin.