Gas-phase reagents for carbon–carbon double bond location: new applications: II. Use of vinyl methyl ether chemical ionization mass spectrometry to characterize C 23 to C 33 insect cuticular alkenes

Abstract

The vinyl methyl ether (VME) reactivity towards alkenes R 1–CHCH–R 2 in the gas phase giving rise to substituted VME radical cations [R 1–CHCH–OCH 3] +°and/or [R 2–CHCH–OCH 3] +° is a well known and elegant approach for the localization of the carbon–carbon double bonds. However, and despite the improvements proposed in the past to increase its specificity, real applications have rarely (if ever) been reported. In this paper, we describe the applicability of GC–VME chemical ionization as a method directly performed on crude cuticular extracts of social insects (three ant species namely Myrmica alaskensis, Formicoxenus quebecensis and Formica selysi and the honey bee). Assignment of the double bond position is done without ambiguity for a number of Δ 8, Δ 9 and Δ 10 long chain alkenes (C 23 to C 33) on the basis of the obtained substituted VME radical cations and corresponding ions after loss of methanol.