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Structural Isomerization of the Gas‐Phase 2‐Norbornyl Cation Revealed with Infrared Spectroscopy and Computational Chemistry
Author(s) -
Mosley Jonathan D.,
Young Justin W.,
Agarwal Jay,
Schaefer Henry F.,
Schleyer Paul v. R.,
Duncan Michael A.
Publication year - 2014
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201311326
Subject(s) - 2 norbornyl cation , isomerization , chemistry , photodissociation , infrared spectroscopy , infrared , spectroscopy , infrared multiphoton dissociation , protonation , mass spectrometry , ion , analytical chemistry (journal) , photochemistry , gas phase , computational chemistry , stereochemistry , organic chemistry , physics , optics , quantum mechanics , chromatography , catalysis
In an attempt to produce the 2‐norbornyl cation (2NB + ) in the gas phase, protonation of norbornene was accomplished in a pulsed discharge ion source coupled with a supersonic molecular beam. The C 7 H 11 + cation was size‐selected in a time‐of‐flight mass spectrometer and investigated with infrared laser photodissociation spectroscopy using the method of “tagging” with argon. The resulting vibrational spectrum, containing sharp bands in the CH stretching and fingerprint regions, was compared to that predicted by computational chemistry. However, the measured spectrum did not match that of 2NB + , prompting a detailed computational study of other possible isomers of C 7 H 11 + . This study finds five isomers more stable than 2NB + . The spectrum obtained corresponds to the 1,3‐dimethylcyclopentenyl cation, the global minimum‐energy structure for C 7 H 11 + , which is produced through an unanticipated ring‐opening rearrangement path.