Diels–Alder reactions of mass‐selected ions in an ion trap mass spectrometer

Abstract This Communication describes the use of a bench‐top ion trap mass spectrometer for the study of structurally diagnostic ion/molecule reactions. The power of the experiment is increased by the broad‐band ion‐isolation and tandem mass spectrometry capabilities of the ion trap which are used to isolate the reactant ion and study its reactions under controlled conditions. The availability of multiple‐stage mass spectrometry (MS n where n = number of stages) provides additional information on the nature of the productions. The compound to be ionized is conveniently introduced into the ion trap from aqueous solution using membrane introduction techniques while the neutral reagent is leaked into the trap through the calibration gas inlet. Polar Diels–Alder reactions of the [4 + 2 + ] type are investigated and comparisons are made between the reactions occurring in the ion trap and those in a pentaquadrupole mass spectrometer. Three‐stage tandem mass spectra (MS 3 ) are used to characterize the ion/molecule reaction products in the quadrupole ion trap.