The far-infrared vapor phase spectra of some halosubstituted anilines

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 vi=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). The following out-of-plane vibrations are also assigned: amino group wag, substituent wag, and ring deformation. The ντ±νi combinations lead to deduced frequencies for the torsional vibration ντ in a number of cases.