A Study of the Kinetics of a Reaction between VO(HEDTA)-1 and Hydrogen Peroxide

• Main Author: Campbell, Elaina B
• Format: Others
• Published: Digital Commons @ East Tennessee State University 2015
• Subjects: vanadium; hydrogen peroxide; hedta; peroxyvanadium; haloperoxidase; kinetics; Inorganic Chemistry
• Online Access: https://dc.etsu.edu/honors/255; https://dc.etsu.edu/cgi/viewcontent.cgi?article=1301&context=honors

Vanadium is commonly used as an agent to make tools rust-resistant. As a transition metal, it can be used as a catalyst due to its ability to change oxidation states. VO(HEDTA)-1, a complex of the vanadyl ion, VO2+ and HEDTA (N-(2-Hydroxyethyl)ethylenediamine-N,N’,N’-triacetic acid) was readily formed. This complex containing vanadium in the +4 oxidation state was reacted with hydrogen peroxide to form a vanadate complex. This vanadate complex was formed as a first step in simulating the vanadate(V)-dependent haloperoxidases in marine algae, a yet uncharacterized reaction. Electron absorption spectroscopy (UV-Vis) was used to observe the oxidation of V(IV) in the complex to V(V) through the color change of the complex from blue to yellow. This color change was observed through the formation of a peak at 450nm. By changing the initial concentrations of VO(HEDTA)-1, hydrogen peroxide, and hydronium ion, the change in absorbance at 450nm during the first minutes of the reaction was correlated with time to determine the initial rates for each reactant. Using this method, a rate equation for the reaction was determined. The rate of reaction was determined to be first order with respected to VO(HEDTA)-1 and H2O2, and 1/2 order with respect to H+. This half-order indicates that the hydronium ion is engaged in a reversible reaction. The involvement of hydroxyl radicals produced by the reaction, as shown by the effect of free radical scavengers to inhibit the reaction was also studied.