UNIMOLECULAR REACTIONS OF ISOLATED ORGANIC IONS - REACTIONS OF THE IMMONIUM IONS CH2=N+(CH3)CH(CH3)2, CH2=N+(CH3)CH2CH2CH3 AND CH2=N+(CH2CH2CH3)2

The reactions of metastable CH2=N+(CH3)C3H, immonium ions have been in vestigated by means of H-2-labelling experiments and kinetic energy re lease measurements. Loss of C3H6, with specific beta-H transfer, is th e sole channel for dissociation of CH2=N+(CH3)CH(CH3)2. This process g ives rise to a Gaussian metastable peak. The isomeric ion, CH2=N+(CH3) CH2CH2CH3, also expels C3H6; however, both alpha-H and gamma-H as well as beta-H transfer occurs in this case, and the reaction proceeds wit h an increased kinetic energy release. The role of ion-neutral complex es in C3H6 loss from CH2=N+(CH3)C3H7 ions is discussed. In addition, C H2=N+(CH3)CH2CH2CH3 eliminates C2H4. This fragmentation yields a broad dish-topped metastable peak, corresponding to a very large kinetic en ergy release (T1/2 approximately 73 kJ mol-1), and it involves specifi c and unidirectional gamma-H transfer. A potential energy profile summ arising the reactions of CH2=N+(CH3) CH2CH2CH3 and CH2=N+-(CH3)CH(CH3) 2 is constructed. The mechanisms by which immonium ions of this genera l class eliminate C3H6 and C2H4 have been further probed by studying t he behaviour of the higher homologue, CH2=N+(CH2CH2CH3)2. The mechanis tic conclusions derived from this work are found to be in excellent qu alitative agreement with those of previous studies.