S. Dohmeierfischer et al., REARRANGEMENT BY INTERMEDIATE ION NEUTRAL COMPLEXES DURING THE MCLAFFERTY FRAGMENTATION OF UNSATURATED-KETONES/, European mass spectrometry, 1(1), 1995, pp. 3-10
Citations number
43
Categorie Soggetti
Spectroscopy,"Physics, Atomic, Molecular & Chemical
The fragmentation of 1-phenylhex-5-ene-1-one 1 was studied by mass ana
lyzed ion kinetic energy spectrometry of its deuterium and ''carbon la
belled derivatives as a further example of interactions within ion/neu
tral complexes, The analysis of the MIKE spectra demonstrate two impor
tant reaction channels of metastable molecular ions, The first one is
a McLafferty rearrangement by elimination of a 1,3-butadiene molecule,
The second energetically even more favoured fragmentation corresponds
to the loss of an ethyl radical. The MIKE spectra of labelled molecul
ar ions, especially that of the (13)carbon labelled compound, indicate
a skeletal rearrangement specifically of the butenyl moiety of the al
kyl side chain by interchanging the terminal carbon atoms C-6 and C-5
with the inner C atoms C-3 and C-4 prior to the loss of the ethyl radi
cal, This specific skeletal rearrangement is explained by an internal
return within an intermediate ion/neutral complex f, consisting of the
acetophenone enol radical cation and the neutral butadiene, by additi
on of the enol radical cation to the remote double bond of the diene,
The second reaction channel is the irreversible cyclization of an inte
rmediate distonic ion c leading to the formation of an ionized ethyl-a
lpha-dihydronaphthol d. This ion is stabilized by loss of an ethyl rad
ical resulting in protonated alpha-naphthol e.