Rc. Dunbar et al., THE FRAGMENTATION-PATTERN OF 1,4-DIOXANE ION, International journal of mass spectrometry and ion processes, 128(1-2), 1993, pp. 21-30
Citations number
25
Categorie Soggetti
Spectroscopy,"Physics, Atomic, Molecular & Chemical
Fragmentation of 1,4-dioxane ions at low internal energies was studied
by photodissociation in the ion cyclotron resonance (ICR) ion trap. B
ranching ratios, rate-energy curves and kinetic parameters were assign
ed for the m/z 58, 57 and 45 fragment ions. M/z58 is formed through a
slightly tight rate-limiting transition state (E0 = 1.46 eV, DELTAS100
0K(dagger) = -1.4 e.u.) which probably corresponds to rupture of the d
ioxane ring. M/z45 is formed through a tight transition state (E0 = 1.
4 2eV, DELTAS1000K(double dagger) = -10.9 eV) which presumably reflect
s a cyclic rearrangement pathway. The kinetic data for formation of 57
are almost equally well fitted by assuming competitive (RRKM) fragmen
tation from the parent ion, or assuming sequential fragmentation throu
gh an intermediate 58 ion. If the mechanism is solely competitive, the
transition state is extraordinary loose (E0 = 1.87 eV, DELTAS1000K(do
uble dagger) = 14.8 e.u.) which would be very surprising for this rear
rangement dissociation. Accordingly we lean toward a sequential dissoc
iation mechanism leading to the 57 product, and suggest further experi
mental testing of this possibility via structural studies of the 57 fr
agment.