Reactions of ionised methyl pent-4-enyl ether, CH2=CH(CH2)(3)OCH3 center dot+

The reactions of CH2=CH(CH2)(3)OCH3.+ are reported and discussed, with part icular emphasis on the behaviour of the metastable ions. The main reactions of the low energy title ions are elimination of CH3., C2H5., and CH3OH, ea ch occurring at similar rates; but loss of H2O, H-. and, to a lesser degree , C2H4, also occurs. The mechanisms of these reactions have been probed by examining collision-induced dissociation spectra and by extensive D-labelin g experiments. The site selectivity for the three main reactions and water elimination varies considerably. Thus, metastable CH2=CH(CH2)(3)OCD3. expel s almost exclusively CH3. (> 97% selectivity) and mainly C2H5. and CD3OH (s imilar to 90% selectivity); but H2O (similar to 37%), HOD (similar to 53%), and even D2O (similar to 10%) all occur in water loss. Tentative mechanism s are proposed for these processes, several of which must entail extensive hydrogen transfers and skeletal isomerisations. Loss of C2H5. and CH3. appe ar to involve rearrangements to species accessible to ionised cyclopentyl m ethyl ether, but expulsion of CH3OH and H2O do not. (C) 2001 Elsevier Scien ce B.V.