Mass Spectra of Lepidopterous Sex Pheromones with a Conjugated Diene System

Abstract

Dodecadien-1-ols, tetradecadien-1-ols and hexadecadien-1-ols with a conjugated (E,E)- or (E)-diene system between the ωl,ω3- and ω5, ω7-positions, their acetates, and aldehẏde derivatives (lepidopterous sex pheromones and candidates) were analyzed by electron impact mass spectrometry, which was operated at 70 eV ionization voltage. Three functional derivatives with a same diene system presented a similar spectral pattern, except for the molecular ions (M⁺), [M − H₂O]⁺ of the alcohols and [M − CH₃CO₂H]⁺ of the acetates. Each isomer showed a characteristic fragment ion series of C_nH_2n−2⁺ ~C_nH_2n−5⁺ (C₄~C₉), which reflected the double-bond position in the molecule, indicating a method for determining the position of a natural diene pheromone by comparing its mass spectrum with those of the synthetic dienes. By this method, the natural pheromone of Hellula undalis was confirmed to be a ω3, ω5-diene. Furthermore, the fitness indexes proposed by Kuwahara et al. were calculated for some pheromone components, using the mass spectra of synthetic dienes, in order to examine the possibility and limitation for applications of those mass spectra to natural pheromone studies.