Trimerization ofEarias insulana sex pheromone, (E,E)-10,12-Hexadecadienal, A phenomenon affecting trapping efficiency

The sex pheromone ofEarias insulana, (E,E)-10,12-hexadecadienal, may trimerize extensively to form a crystalline trioxane derivative. The structure of the trimer was deduced from its CI-MS and NMR spectra. Capillary GC analysis resulted in the thermal decomposition of the trimer to the monomer. This process could be studied on a 2-m packed column under specific conditions. A convenient separation between the pheromone and its trimer was achieved by TLC. The trimer was inactive in the field, and it has a harmful effect on the performance of the polyethylene dispenser. Material which contains large amounts of the trimer is unsuitable for field use, even if applied at high dosage. The pheromone should be analyzed by NMR or TLC in addition to GC in order to detect the presence of its trimer. The trimerization process is catalyzed by acid which should therefore be completely eliminated from the storing vessels.