Autocatalysed Oxidative Decarboxylation of Succinic Acid by Permanganate Ion - A Kinetic Study

Brijesh Pare, R. S. Verma and V. R. Shastry

Madhav Science College, Vikram University, Ujjain- 456 010 (India)

A study of oxidative decarboxylation of Succinic acid by permanganate ion in moderately concentrated acidic medium has been found to be two-stage i.e. slow first stage followed by relatively faster second stage. The log (a-x) versus t curve displays an inflection. In both the stages the reaction follows first order behavior with respect to each, substrate and the oxidant. The cause of autocatalysis has been attributed to Mn(II) ions, which was further substantiated by the initial addition of MnSO4. The oxidation reactions are acid catalysed and therefore, various hypotheses for the mechanism of acid catalysis were tested. Thus, the role of water molecule as proton abstracting agent is established. On addition of flouride ions a known complexing agent, there is a decrease in the reaction rate. The stoichiometry for the succinic acid reaction is (CH2COOH)2 + 2 MnO4- + 6H+ 2 5 HCOOH + 10 H2O + 5 CO2 + 2 Mn2+. The effect of variation of ionic strength has also been studied. Thermodynamic parameters have been computed by studying the reaction at different temperatures. On the basis of the various observations and product characterization a most plausible mechanism has been envisaged.

Inflection; decarboxylation; autocatalysis