Hydroperoxidation

Hydroperoxidation is a chemical process in which a hydroperoxide group (ROOH) is introduced into an organic substrate, most commonly through oxidation by molecular oxygen (autoxidation) or by entry of hydroperoxyl radicals. In many contexts it refers to the formation of lipid hydroperoxides during lipid peroxidation, which are the first stable products of the reaction between polyunsaturated fatty substrates and oxygen.

The mechanism is typically described as a radical chain process. Initiation generates a substrate radical (R•) and a peroxyl radical (ROO•) from O2. Propagation converts RH into ROOH with the transfer of a hydrogen atom, while ROO• can re-enter the chain by abstracting hydrogen from another substrate molecule. The process can continue until termination occurs by radical–radical combination or reaction with antioxidants. Alternative pathways include reactions with singlet oxygen to form hydroperoxides in specific substrates.

Biological and industrial relevance is broad. In biology, lipid hydroperoxides (LOOH) form in cellular membranes and serve as markers of oxidative stress; their decomposition yields reactive aldehydes such as malondialdehyde and 4-hydroxynonenal, which can disrupt cellular function. In foods and polymers, hydroperoxides contribute to rancidity and material degradation, influencing flavor, color, and mechanical properties. Antioxidants like vitamin E or synthetic BHT commonly act to slow hydroperoxidation.

Detection and analysis of hydroperoxides employ methods such as iodometric assays and the FOX (ferrous oxidation in xylenol orange) assay, as well as chromatographic techniques like LC-MS. Because hydroperoxides are often unstable, storage and handling typically require low temperatures and, in some cases, inert atmospheres to limit further oxidation.

Safety considerations include the potential explosive hazards of organic hydroperoxides under certain conditions, warranting careful storage away from heat and metal catalysts.