[en] Upon collisional activation at high kinetic energy (8 keV), the molecular ions of pyridine N-oxides 1-5 undergo an unexpected loss of 16 mass units (oxygen) provided molecular oxygen or nitric oxide is used as the target gas instead of helium. Molecular i
R. Flammang, L. Gallez, Y. Van Haverbeke, M.W. Wong and C. Wentrup, Rapid Commun. Mass Spectrom. 10, 232 (1996).
G.A. McGibbon, P.C. Burgers and J.K. Terlouw, Int. J. Mass Spectrom. Ion Processes 136, 191 (1994).
C. Aubry and J.L. Holmes, J. Phys. Chem. A 102, 6441 (1998).
R. Flammang, P. Gerbaux and M. W. Wong, Chem. Phys. Lett. 300, 183 (1999).
P. Gerbaux, M. Barbieux-Flammang, Y. Van Haverbeke and R. Flammang, Rapid Commun. Mass Spectrom. 13, 1707 (1999).
D.J. Lavorato, J.K. Terlouw, G.A. McGibbon, T.K. Dargel, W. Koch and H. Schwarz, Int. J. Mass Spectrom. Ion Processes 179/180, 7 (1998).
(a) R. Grigg and B.G. Odell, J. Chem. Soc. (B) 218 (1966);
(b) D.A. Lightner, R. Nicoletti, G.B. Quistad and E. Irwin, Org. Mass Spectrom. 4, 571 (1970);
(c) A.M. Duffield and O. Buchardt, Acta Chem. Scand. 26, 2423 (1972).
R. Flammang, Y. Van Haverbeke, C. Braybrook and J. Brown, Rapid Commun. Mass Spectrom. 9, 795 (1995).
P. Gerbaux, R. Flammang, C.Th. Pedersen and M.W.Wong, J. Phys. Chem. A 103, 3666 (1999).
P. Gerbaux, Y. Van Haverbeke and R. Flammang, J. Mass Spectrom. 32, 1170 (1997).
P. Gerbaux, Y. Van Haverbeke and R. Flammang, Int. J. Mass Spectrom. 184, 39 (1999).
S.G. Lias, J.E. Bartmess, J.F. Liebman, J.L. Holmes, R.D. Levin and W.G. Mallard, J. Phys. Chem. Ref. Data 17, Supplement no. 1 (1988).
M.J. Frisch, G.W. Trucks, H.B. Schlegel, P.M.W. Gill, B.J. Johnson, M.A. Robb, J.R. Cheeseman, T.A. Keith, G.A. Peterson, J.A. Montgomery, K. Raghavachari, M.A. AI-Laham, V.G. Zakrzewski, J.V. Ortiz, J.B. Foresman, J. Cioslowski, B.B. Stefanow, A. Nanayaklara, M. Challacombe, C.Y. Peng, P.Y. Ayala, W. Chen, M.W. Wong, J.L. Andres, E.S. Replogle, R. Gomperts, R.L. Martin, D.J. Fox, J.S. Binkley, D.J. Defrees, J. Baker, J.P. Stewart, M. Head-Gordon, C. Gonzalez and J.A. Pople, Gaussian, Inc., Pittsburgh, PA (1995).
D. Lahem, R. Flammang, H.T. Le and M.T. Nguyen, Rapid Commun. Mass Spectrom. 12, 1972 (1998).
It has been suggested by the referees that the experimental results do not require the production of two different complexes, but only one with different internal energies. This situation appears, however, unlikely to us as the peaks at m/z 125 and 79 have similar intensities (see Figure 5) and the m/z 79 peak, not observed in the metastable ion spectrum of the m/z 125 ion, is only scarcely (0.5%) seen in the corresponding CA spectrum. Moreover, preliminary theoretical calculations have indicated that the addition of NO on the oxygen of pyridine oxide is exothermic by 150 kJ mol-1, possibly precluding the observation of such a complex. We recognize nevertheless that the question remains open.
M.A. Mendes, L.A.B. Moraes, R. Sparrapan, M.N. Eberlin, R. Kostiainen and T. Kothiaho, J. Am. Chem. Soc. 120, 7869 (1998).
For a recent review, see C.A. Schalley, G. Hornung, D. Schroder and H. Schwarz, Chem. Soc. Rev. 27, 91 (1998).
