G. Bouchoux, Y. Hoppilliard, P. Jaudon
Mar 25, 1985
Citations
0
Influential Citations
6
Citations
Journal
International Journal of Mass Spectrometry and Ion Processes
Abstract
Abstract The metastable molecular ion of 4-methyl-2-pentanone loses competitively a methyl radical and an ethylene molecule. The mechanisms of these eliminations are deduced from the unimolecular dissociation spectra of the deuterated derivatives (1, 1, 1-d3, 3-d1, 4′, 4′, 4′-d3, 5, 5, 5-d3 and 1, 1, 1, 3-d4. The methyl loss gives the hydroxycarbenium ion [a]+, [CH3C(OH)CHCHCH3]+, and the acylium ion [b]+, [CH3CH2CH(CH3)CO]+. The mechanism leading to the former cation is demonstrated to involve a 1,4 hydrogen transfer and a 1, 2 CH3COH migration. The McLafferty rearrangement, giving [CH3C(OH)CHCH3]+·, is preceded by a significant hydrogen exchange between positions 1 and 5. The thermochemical aspect of the isomerisation-dissociation pattern is discussed in conjunction with MNDO molecular orbital calculations.