Reactions unimoleculaires des cations radicaux [CH3(CH2)n-1-NH2]+ en phase gazeuse

Determination of Tuaminoheptane in Doping Control Urine Samples

“…Most importantly, rearrangements of the carbon skeleton forming cyclic intermediates were reported that initiated the shift of the amino function to adjacent carbons. 32,34 The compounds investigated in the present study formed most prominent fragment ions at m/z 44 and 70 in case of underivatised and derivatised tuaminoheptane, respectively ( Figure 1) and corresponding ions were also observed with additional derivatives as listed in Table 1. The molecular ions of tuaminoheptane and its condensation products with various aldehydes and acetone were not detected, which is a well known issue of EI-MS-based assays for primary and secondary amines such as amphetamine and ephedrine.…”

The chemistry of CnH2n+2N+ ions

“…This ion arises by methylene loss from 5, which affords CHFNHZ; in contrast, 3 and 4 showed negligible and very small m/z 30 signals, respectively, in their CID spectra (92). Isomerization of 5 to 3 was proposed to take place via the relatively high-energy open-chain carbonium ion +CH2CH2NH2 (6) (55,92); this is accesible to 5 by r h g opening via rupture of a C-N bond, or to 3 via a 1,Zhydride shift (Scheme 111).…”

“…Immonium ions can also be formed from ionized amines by processes other than a-cleavage. The most important of these routes is "pseudo-a-cleavage" (4)(5)(6), in which isomerization of the original ionized amine by intramolecular hydrogen transfer via distonic (7)(8)(9)(10) radical cations precedes dissociation. The rearranged ionized amine eventually fragments to yield a more stable immonium ion than that which would have been accessible by direct cleavage of the initial structure.…”

Hydrogen radical abstraction by small ionized molecules, distonic ions and ionized carbenes in the gas phase

“…They can be formed by a first H • transfer from the chain to an ionized heteroatom [5] or by ring opening as studied by Tabet and coworkers [9]. From experiment [5,9,10] and from calculation [11], it has been also shown that the energy barrier for the transfers to a carbon radical site decreases from the 1,2-H • migration up to the 1,5 one. More generally, the energy barrier for intramolecular 1,n-H • transfers is the lowest when the hydrogen to be transferred, the acceptor atom and donor atom are in line in the transition state.…”

“…Experiment shows that intramolecular 1,2-H • transfers to an ionized heteroatom are generally not observed (see for instance Ref. [5]), 1,3-H • transfers are rare and irreversible when observed [6], while 1,4-and a fortiori 1,5-and 1,6-H • transfers are easier and often reversible. This has been confirmed by calculations carried out on ionized amines [7] as well as on ionized alcohols [8].…”