THE FAR-INFRARED VAPOR PHASE SPECTRA OF SOME HALO-SUBSTITUTED ANILINES
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Date
1978
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Ohio State University
Abstract
Vapor phase far-infrared spectra from 35 to $675\, cm^{-1}$ of the nine ortho-, meta- and para-substituted fluoro-, chloro- and bromoanilines obtained with an interferometer are reported. The $v_{1}=1,2,$ and 3 levels of the amino group inversion vibration are established from the observed transitions, and the barriers to inversion are derived from these, using a simple double minimum harmonic well potential with a Gaussian barrier. Calculated barrier heights range between $385.9\, cm^{-1}$ (2-bromoaniline) and $599.9\, cm^{-1}$ (4-fluoroaniline), and these are discussed in terms of the electronic effects of the halogen substituents. Intramolecular hydrogen bonds and/or steric effects lead to remarkably low inversion barriers in 2-chloro- and 2-bromoaniline- The following out-of-plane vibrations are also assigned: amino group wag, substituent wag, and ring deformation. The $\nu_{\tau}\pm \nu_{i}$ combinations lead to deduced frequencies for the torsional vibration, $v_{\tau}$, in a number of cases.
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Author Institution: Department of Chemistry, University of Calgary