Reactions of low-energy pentenyl methyl ether radical cations C2H5CHCHCH2OCH3+, CH2CHCH(C2H5)OCH3+ and CH2C(C2H5)CH2OCH3+

The mechanisms for isomerisation and dissociation of the title ions have been probed by a combination of mass spectrometric techniques. In contrast to the other 10 ionised methyl pentenyl ethers, each of which has a unique and characteristic reactivity, these three isomers show many common features. Elimination of an ethyl radical, a methyl radical and a molecule of methanol occur at similar relative rates. Selective labelling experiments are broadly consistent with the conclusion that interconversion of these three C5H9OCH3+ radical cations competes effectively with dissociation. This enhanced rate of interconversion, compared to that for the other 10 ionised ethers, is explained in terms of facile 1,2-H and 1,2-C2H5 shifts and, in some instances, skeletal rearrangements involving ionised ethylmethoxycyclopropane.