Insect sex pheromones: Evaporation rates of alcohols and acetates from natural rubber septa

Abstract

The half-lives (t _1/2) of alcohol sex pheromones, 1-alkanols, acetate sex pheromones, and an epoxide (disparlure) were determined on natural rubber septa. Thet _1/2 values for the homologous alcohols from decanol to heptadecanol increased regularly from 2.2 to 1117 days, but thet _1/2 of octadecanol was 609 days. Thet _1/2 values of (Z)7-, (E)7-, and (Z)9-tetradecen-1-ol acetates were 154, 168, and 199 days, respectively, whereas those of five other tested 14-carbon acetates ranged from 310 to 350 days. The dependence oft _1/2 values on chain length and double-bond position is consistent with the hypothesis that molecular size is an important variable affectingt _1/2 values. Also, in accordance with the hypothesis, when aZ-alkenyl compound has a much shortert _1/2 than the corresponding saturated compound, thet _1/2 values of theZ compound and itsE isomer may be quite different. Thus, (E)-9-tetradecen-l-ol acetate had at _1/2 of 331 days. Thet _1/2 of disparlure was 180 days. The effect of thecis-7,8 epoxide group is apparently similar to that of the olefin group in lowering thet _1/2 below the value that would be expected solely on the basis of chain length.