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Infrared Absorption Features of Gaseous Isopropyl Carbocations
Author(s) -
Chiavarino Barbara,
Crestoni Maria E.,
Fornarini Simonetta,
Lemaire Joel,
Mac Aleese Luke,
Maître Philippe
Publication year - 2004
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400295
Subject(s) - infrared multiphoton dissociation , chemistry , fourier transform ion cyclotron resonance , ion , infrared spectroscopy , photochemistry , infrared , mass spectrometry , cyclopropane , analytical chemistry (journal) , organic chemistry , ring (chemistry) , physics , chromatography , optics
C 3 H 7 + ions were formed in the cell of a Fourier transform ion cyclotron resonance mass spectrometer and assayed by their multiphoton dissociation (MPD) behavior, triggered by the absorption of tunable IR radiation from a free‐electron laser source providing a high fluence. The derived experimental IRMPD spectrum, which reflects the active vibrational modes of the ion, was compared with the IR spectra calculated for the optimized structures of the most‐stable species on the C 3 H 7 + potential energy surface, namely, a chiral i C 3 H 7 + ion of C 2 symmetry and an asymmetric corner‐protonated cyclopropane, c C 3 H 7 + . The significant features in the IRMPD spectra of both the unlabeled and the perdeuterated ions obtained by ionization and fragmentation of isobutane or 2‐chloro[D 7 ]propane confirm the presence of the isopropyl cation, the ground‐state isomer, whose IR spectroscopic features can thus be comparatively checked in the gas phase and in condensed superacid media. Details of the IRMPD features are suggested to result from the nearly barrierless interconversion of the two C 2 enantiomers.