Determination of enolization rates and overall stoichiometry from < sup> 1 H NMR records of the methylmalonic acid Belousov-Zhabotinsky reaction

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In this paper we have determined the methylmalonic acid enolization rate constant in 1 M sulfuric acid directly from 1H NMR records of the corresponding oscillatory Belousov-Zhabotinsky (BZ) reaction. The obtained rate constant value is in excellent agreement with earlier determinations obtained from the isolated component system. The overall stoichiometry of the methylmalonic acid Belousov-Zhabotinsky reaction was found to be as predicted by the Field-Körös-Noyes theory, i.e., with a final bromomethylmalonic acid (BrMeMA)/acetic acid (HAc) concentration ratio of 3/2. We found that independent of the initial methylmalonic acid concentration the BrMeMA/HAc concentration ratio starts at a high initial value (between 2 and 5) and decreases during the reaction to its equilibrium value of 1.5. Several possibilities to explain this behavior are discussed. We are also able to show that 1H NMR chemical shift data of the water peak during the BZ reaction are related to the changes in BrO3- and H+ concentrations and follow the overall stoichiometry predicted by Field, Körös, and Noyes. © 1989 American Chemical Society.

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Journal of Physical Chemistry