In vitro reducing abilities towards chromate of various hydroxy-containing compounds, including saccharides and their derivatives

Abstract

The reduction of potassium chromate has been carried out with a variety of OH-containing compounds as reductants, which include pentoses, polyols, glycols, and sugar derivatives. The corresponding reactions were followed using UV-vis and EPR spectroscopies and electrochemistry. The progress of the chromate reduction reactions has been monitored by measuring UV-vis and EPR spectra as a function of time. The observed pseudo first-order reaction rate constants are derived based on the changes in the intensities of the Cr(VI), Cr(V), and Cr(III) signals. Cyclic voltammograms of the simple reductants and their final Cr(III) products formed from the reactions of chromate have also been measured. The reductive abilities of all these reductants have been derived from the spectral data and are discussed on a comparative basis. Based on the results, the aspects that makes a particular reductant more efficient has been addressed. The results obtained from UV-vis, EPR, and cyclic voltammetry are found to be mutually dependent and exhibit among themselves a linear correlation, suggesting that both the reducing and complexing nature of these molecules play important roles in the chromate reduction.