Discipline: Chemistry and Chemical Sciences
Subcategory: Chemistry (not Biochemistry)
Room: Exhibit Hall
Chantele Owusu - Regis University
Co-Author(s): Grecia Anaya, Regis University, Denver, CO 80221;Manveer Singh, Regis University, Denver, CO 80221;and Surendra Mahapatro, Regis University, Denver, CO 80221
Potassium permanganate is a strong oxidizing agent and has multiples uses in organic synthesis and in water treatment and purification. It oxidizes a wide range of organic compounds that include aromatic hydrocarbons, alcohols, hydroxyl-acids, DNA-nucleotide bases and carbohydrates. Permanganate oxidation of inorganic and organic substrates show a rich diversity of oxidation states that include green Mn(VI), blue Mn(V), tobacco yellow soluble-Mn(IV) and red Mn(III). In acid medium, permanganate undergoes a 5-electron reduction to Mn(II), while in alkaline medium it suffers a three –electron change resulting in black MnO2. The express purpose of this study is to gain insight into the structure and reactivity of manganese intermediates in the oxidation of hydroxy-carboxylic acids as a function of pH. Specifically, we have studied the pH dependence in the oxidation of citric acid (TCA cycle), malic and lactic acids, 2-hydroxy-2-ethyl-butanoic acid (HEBA) and mandelic acid. In acidic medium (pH 1), kinetic curves monitored at 526 nm showed a slow phase (induction period) followed by a rapid autocatalytic phase. In the presence of added Mn(II) perchlorate, regular exponential decay curves were observed. In alkaline pH (≥ 13), a stoichiometric green Mn(VI) intermediate (λmax = 606 nm; green) is rapidly formed which then decays in a slow second step resulting in black MnO2. In the case of mandelic acid, at neutral pH, a tobacco yellow, soluble(colloidal) Mn(IV) intermediate is observed at 418 nm. The primary carbonyl products (3-ketoglutarate, 3-pentanone, benzaldehyde and phenylglyoxylic acid), are characterized by their 2,4-dinitrophenylhydrazone derivatives. We will report reverse –phase HPLC product studies for carbonyl products and determination of manganese oxidation states by iodometric titrations.
Funder Acknowledgement(s): "This research is supported by the Western Alliance to Expand Student Opportunities (WAESO) Louis Stokes Alliance for Minority Participation (LSAMP) National Science Foundation (NSF) Cooperative Agreement No. HRD-1619524."
Faculty Advisor: Dr. Surendra Mahapatro, email@example.com
Role: My contribution to this research project include developing solution to oxidize citric acid at a pH of 1 and 13. These solutions were also used to analyze autocatalysis and permanganate intermediate changes through the kinetic curves in acidic and basic medium.