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Low‐Frequency CH Stretch Vibrations of Free Alkoxide Ions
Author(s) -
Oomens Jos,
Berden Giel,
Morton Thomas Hellman
Publication year - 2017
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.201609437
Subject(s) - alkoxide , hyperconjugation , ion , chemistry , hydrocarbon , molecule , electron , molecular vibration , natural bond orbital , computational chemistry , crystallography , chemical physics , photochemistry , physics , organic chemistry , quantum mechanics , catalysis
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.