Model experiments about the formation of volatile carbonyl compounds

Abstract Autoxidation of linoleic acid, 9‐hydroperoxy‐10, 12‐octadecadienoic acid (9‐HPOD), 13‐hydroperoxy‐9, 11‐octadecadienoic acid (13‐HPOD), 2‐octenal and 2,4‐decadienal at 38 C were investigated with respect to the formation of volatile carbonyl compounds. The 13‐HPOD and all compounds having a double bond in ω‐6‐position produce hexanal. After initiating by small amounts of alkoxy radicals, both hexanal and 2,4‐decadienal autoxideize further. While, individually, hexanal reacts somewhat faster than 2,4‐decadienal, forming the corresponding acid, in a mixture of the two aldehydes, hexanal is protected to a certain extent by the unsaturated aldehyde against autoxidation. This explains the predominance of hexanal among the volatile carbonyl compounds resulting from linoleic acid autoxidation. Small amounts of 2‐octenal originate from both the 9‐HPOD and the 2,4‐decadienal as a result of oxidation of the ω‐8‐double bond of these compounds. Aside from its acid as main autoxidation product, 2‐octenal yields heptanal and hexanal as volatile compounds.