Phenylmalonic Acid Reaction with Iodine and Behavior in a Briggs-Rauscher Oscillator

Article abstract of DOI:10.1021/j100344a024

Phenylmalonic acid (PhMA) reacts via an enol mechanism with aqueous iodine to form rather reactive iodophenylmalonic acid.The rate at 25 degC in 0.1 M acid can be described by -d/dt (M s^-1) = 126 /(1 + (3.8*1E4)).This iodo product can undergo hydrolysis, decarboxylation, and oxidation.Oxidants that oxidize iodide to iodine also regenerate iodine quantitatively from iodophenylmalonic acid, seemingly via an attack by HOI.When manganous ion and hydrogen peroxide are present, iodophenylmalonic acid reacts fairly rapidly by a different mechanism, giving up iodide ions.In a mixture with acidic iodate, hydrogen peroxide, and manganous ions, PhMA can serve as a substrate for a Briggs-Rauscher-type oscillating reaction.The iodo product is much less stable than the iodo product with typical Briggs-Rauscher substrates such as malonic acid or acetone, and any proposed oscillatory mechanism must be able to account for fairly rapid decomposition and iodine regeneration.