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Gas‐phase protonation of arylalkylamines. A metastable ion study
Author(s) -
Cardoso Ana M.,
Alexandre Sílvia M. G.,
Barros Cristina M. F.,
FerrerCorreia A. J.,
Nibbering Nico M. M.
Publication year - 1998
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19980715)12:13<825::aid-rcm243>3.0.co;2-k
Subject(s) - chemistry , protonation , proton affinity , deuterium , ion , chemical ionization , ring (chemistry) , amine gas treating , molecule , reagent , metastability , ammonia , mass spectrum , proton , aromatic amine , mass spectrometry , ionization , photochemistry , medicinal chemistry , organic chemistry , physics , chromatography , quantum mechanics
The unimolecular metastable decompositions of protonated arylalkylamines of general formula R 1 R 2 C 6 H 3 CHR 3 (CH 2 ) n NR 4 R 5 where R 1 =H or OH; R 2 =H, F, NO 2 , OH or OCH 3 ; R 3 =H or OH; R 4 and R 5 =H and/or CH 3 ; and n =1–3, generated by chemical ionization with water and ammonia as ionizing reagents, have been examined via the analysis of the mass‐analysed ion kinetic energy spectra of the protonated molecules. The mechanisms proposed have been probed by chemical ionization of the deuterated analogues of the amines with D 2 O and ND 3 . The results show that protonation occurs preferentially on the amino group leading to abundant ions due to ammonia (or amine) loss, although ions resulting from transfer of the proton from the amino group to the aromatic ring, to the hydroxy group para to the aliphatic chain and to the benzylic OH, are also observed. Experimental evidence for H/D exchange between the deuteronated amino group and the aromatic ring is presented, and discussed in terms of the internal energy content of the deuterated ions and structural features of the amines, such as aliphatic chain length and the presence of a second hydroxy group on the aromatic ring. © 1998 John Wiley & Sons, Ltd.