The electrochemical oxidation of ascorbic acid (AA) at a platinum electrode has been studied in 0.1 M HClO4, In situ infrared reflectance spectroscopy (SPAIRS and SNIFTIRS techniques) was used to investigate the reaction intermediates. The identification of the different electroreactive species and adsorbed intermediates allowed us to postulate a reaction mechanism for the transformation of AA into dehydroascorbic acid (DHA).