Unimolecular fragmentation of some gaseous protonated amines

Eric J. Reiner, Raymond A. Poirier, Michael R. Peterson, I. Csizmadia, Alex G. Harrison

Research output: Contribution to journalArticle

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Abstract

The proton-transfer chemical ionization mass spectra of the C3 to C5 monoalkyl amines as well as a number of di- and tri-alkyl amines have been determined using H3 + and (in some cases) HCO+ as protonating agent. The RNH3 + ions fragment to form alkyl ions R+ and eliminate alkenes to form NH4 +. In addition, abundant immonium ions are observed in the CI mass spectra corresponding to elimination of alkane from RNH3 + or to direct alkide ion abstraction from RNH2; these ions serve to characterize the alkyl groups attached to the α-carbon atom of the amine. Although alkane elimination from RNH3 + is the thermochemically favoured reaction, only R+ and NH4+ are formed in decomposition of metastable RNH~i+o ns. The potential energy profile for fragmentation of i-C3H7NH3 + has been calculated by ab initio molecular orbital methods. These calculations show that CH4 elimination has a large energy barrier additional to the reaction endothermicity while formation of NH4 + has only a small additional barrier and formation of C3H7 + has no barrier additional to the endothermicity. It is concluded that the immonium ions probably arise primarily by direct alkide ion abstraction reactions.

Original languageEnglish
Pages (from-to)1652-1660
Number of pages9
JournalCanadian Journal of Chemistry
Volume64
Issue number8
Publication statusPublished - 1985

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Amines
Ions
Alkanes
Paraffins
Proton transfer
Energy barriers
Alkenes
Molecular orbitals
Potential energy
Olefins
Ionization
Carbon
Decomposition
Atoms

ASJC Scopus subject areas

  • Chemistry(all)
  • Organic Chemistry
  • Catalysis

Cite this

Reiner, E. J., Poirier, R. A., Peterson, M. R., Csizmadia, I., & Harrison, A. G. (1985). Unimolecular fragmentation of some gaseous protonated amines. Canadian Journal of Chemistry, 64(8), 1652-1660.

Unimolecular fragmentation of some gaseous protonated amines. / Reiner, Eric J.; Poirier, Raymond A.; Peterson, Michael R.; Csizmadia, I.; Harrison, Alex G.

In: Canadian Journal of Chemistry, Vol. 64, No. 8, 1985, p. 1652-1660.

Research output: Contribution to journalArticle

Reiner, EJ, Poirier, RA, Peterson, MR, Csizmadia, I & Harrison, AG 1985, 'Unimolecular fragmentation of some gaseous protonated amines', Canadian Journal of Chemistry, vol. 64, no. 8, pp. 1652-1660.
Reiner EJ, Poirier RA, Peterson MR, Csizmadia I, Harrison AG. Unimolecular fragmentation of some gaseous protonated amines. Canadian Journal of Chemistry. 1985;64(8):1652-1660.
Reiner, Eric J. ; Poirier, Raymond A. ; Peterson, Michael R. ; Csizmadia, I. ; Harrison, Alex G. / Unimolecular fragmentation of some gaseous protonated amines. In: Canadian Journal of Chemistry. 1985 ; Vol. 64, No. 8. pp. 1652-1660.
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