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Oxidative decarboxylation of 2‐oxoacids by hydroperoxides can be used to lower peroxide values in citrus oils
Author(s) -
Calandra Michael J.,
Wang Ying
Publication year - 2020
Publication title -
flavour and fragrance journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.393
H-Index - 70
eISSN - 1099-1026
pISSN - 0882-5734
DOI - 10.1002/ffj.3543
Subject(s) - chemistry , iodometry , terpene , decarboxylation , moiety , oxidative decarboxylation , organic chemistry , peroxide , autoxidation , catalysis
Many terpenes may autoxidize under certain conditions to form terpene hydroperoxides, which have been reported to be skin sensitizers that may cause allergic contact dermatitis. The fragrance industry is currently required to monitor terpene hydroperoxide levels in many raw materials by iodometric titration (aka; the peroxide value, or POV test), and to reject lots that exceed a specification limit. We have found that compounds containing the 2‐oxoacid moiety (the “pyruvic acid” moiety) react readily with organic hydroperoxides via an oxidative decarboxylation mechanism. The reaction products include an alcohol corresponding to the reduced hydroperoxide, carbon dioxide, and a carboxylic acid that is one carbon shorter than the starting 2‐oxoacid. Because the hydroperoxide is irreversibly consumed by this reaction, the POV of a 2‐oxoacid‐treated sample is effectively lowered. It follows that the skin sensitizing potential of the treated sample should also be lowered as a result of the hydroperoxide removal.