Comparing methylene blue-photosensitized oxidation of methyl-conjugated linoleate and methyl linoleate

The photooxidations of methyl-conjugated linoleate (MCL) and methyl linoleate (ML) were compared using methylene blue as a sensitizer in ethanol solutions. MCL was lost to a lower extent and yielded less hydroperoxide but bleached methylene blue at a higher rate than ML. The different isomers of MCL were not equally lost, and the photooxidation of MCL was accompanied by interisomerization. The results suggested that different mechanisms were involved in the photooxidations of MCL and ML.