Letter: Reactions of the Allyl and 2-Propenyl Cations Isomers with D 2 O: Separation and Titration of Mixed Isomers by Fourier Transform-Ion Cyclotron Resonance

(a) Bowers M.T. Shuying L. Kemper P. Stradling R. Webb H. Aue D.H. Gilbert J.R. and Jennings K.R. , J. Am. Chem. Soc. 102, 4830 (1980); (b) Burgers P.C. Holmes J.L. Mommers A.A. and Szulejko J.E. , Org. Mass Spectrom. 18, 596 (1983).

Lay J.O. and Gross M.L. , J. Am. Chem. Soc. 105, 3445 (1983).

Fornarini S. Speranza M. Attina M. Cacace F. and Giacomello P. , J. Am. Chem. Soc. 106, 2498 (1984).

Bowen R.D. Williams D.H. Schwarz H. and Wesdemiotis C. , J. Am. Chem. Soc. 101, 4681 (1979).

Stams D.A. Johri K.K. and Morton T.H. , J. Am. Chem. Soc. 110, 699 (1988).

Riveros J.M. and Zhu Z. , Rapid Commun. Mass Spectrom. 5, 387 (1991).

(a) Radom L. Hariharan P.C. Pople J.A. and Schleyer P.v.R. , J. Am. Chem. Soc. 95, 6531 (1973); (b) Raghavachari K. Whiteside R.A. Pople J.A. and Schleyer P.v.R. , J. Am. Chem. Soc. 103, 5649 (1981).

Lias S.G. Bartmess J.E. Liebman J.F. Holmes J.L. Levin R.D. and Mallard W.G. , J. Phys. Chem. Ref. Data 17, Supplement 1 (1988).

Mass selected m/z 41 ions produced in the external ion source by electron impact on various neutral precursors, are allowed to react with deuterated water (2–3 × 10⁻⁸ mbar) for a preselected time. An argon gas bath (2 × 10⁻⁷ mbar) is used to collisionally relax the ions to near thermal energies. The standard ionization energy was 20 eV.

When the non-exchanging C₃H₅+ is isolated after a long reaction time with D₂O, it does not react any further. Bouchoux G. Penaud-Berruyer F. Audier H.E. Mourgues P. and Tortajada J. , J. Mass Spectrom. 32, 188 (1997).

According to results from Burgers the proportion of allyl cation in the mixture depends on the ionization energy, because too much energy would allow isomerization of the cations. Thus, we have worked at a comparatively low ionization energy (20 eV).

Aue D.H. Davidson W.R. and Bowers M.T. , J. Am. Chem. Soc. 98, 6700 (1976).

These are the values cited by Aue Proton affinity scales have been revised since: Reference 8 gives for MeOH PA = 761.1 kJ mol⁻¹ and for H₂S PA = 712.1 kJ mol⁻¹, which means that these values should be lowered by about 21 kJ mol⁻¹.

Developed by Millié P. at the CEA–Saclay Research Center, for a further description see Brenner V. Zehnacker A. Lahmani F. and Millié P. , J. Phys. Chem. 41, 97 (1993).