The mechanisms of the elimination of a propene molecule from the molecular ions of a series of 3-and 4-substituted aryl n-propyl ethers (YC, H, OC, H,, Y= H, CH,, CF,, NO,, CH, S and CH, O) were examined with the use of deuterium labelling and tandem mass spectrometry. Propene loss dominates in the ion-source reactions and is the exclusive process observed for the metastable molecular ions of most of the aryl n-propyl ethers. ...