title: Low-Frequency CH Stretch Vibrations of Free Alkoxide Ions.
abstract: CH stretches in hydrocarbon cations often shift to lower frequencies relative to neutral molecules, because they do not have sufficient electrons to give every bond an electron pair. A parallel effect in negatively charged species has not been previously observed. Here we show that CH bond weakening occurs in alkoxide anions as a consequence of hyperconjugation. The reasoning differs somewhat from the case of positively charged ions, but the net effect is the same: to lower CH stretching frequencies by hundreds of wavenumbers.
authors.affiliation: Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED, Nijmegen, The Netherlands.|van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098XH, Amsterdam, The Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.affiliation: Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED, Nijmegen, The Netherlands.
authors.forename: Giel
authors.initials: G
authors.lastname: Berden
authors.affiliation: Department of Chemistry, University of California, Riverside, Riverside, CA, 92521-0403, USA.
authors.forename: Thomas Hellman
authors.identifier: 0000-0002-4122-4583
authors.initials: TH
authors.lastname: Morton
keywords: IR spectroscopy; IRMPD action spectroscopy; anions; hyperconjugation; mass spectrometry