Hydroxyl radical induced decomposition of aliphatic acids in oxygenated and deoxygenated aqueous solutions

The aim of this work was to study the oxidation of aliphatic acids by radicals resulting from the protolysis of hydrogen peroxide. Experiments carried out in dilute aqueous solutions (pH = 2.9−3.5) of mono and dicarboxylic acids with 1 to 4 carbon atoms showed (i) the oxidation of the carboxylic group is slow, (ii) the hydroxyl group of hydroxylated acids activates the adjacent CH bond and leads, after hydrogen atoms abstraction, O2 addition and HO2 removal, to the carbonyl group, (iii) a CC bond cleavage occurs after hydrogen atom abstraction and oxygen addition for unsubstituted dicarboxylic acids. Except for oxalic acid, the mechanism of oxidation into CO2 of the acids studied involves oxygen consumption and O2−/HO2 release.