Ring Breathing Vibrations

Figure 6.13 Illustration of (a) rocking, (b) twisting, (c) scissoring and (d) wagging vibrations in a CH2 group. Also shown are (e) the torsional vibration in ethylene, (f) the ring-breathing vibration in benzene and (g) the inversion, or umbrella, vibration in ammonia...

This explains the enhanced reactivity of D2 species toward water vapor compared to the structures responsible for the D1 and 430 cm 1 bands (Figure 7), which are assigned to ring breathing vibrations of unstrained four-membered and higher order rings, respectively. 

Many triazoles have been reported to have strong absorption bands in the region 1150-900 cm, which may be due to ring breathing vibrations. 

Azo compounds. These compounds exhibit stretching of the —N=N— bond giving rise to only weak absorption near 1600 cm-1, which is shifted to lower frequency by conjugation. In aromatic compounds the band is generally masked by the aromatic ring breathing vibrations. 

Eysel and Bertie (1988) considered the absolute normalized Raman scattering cross section of the ring breathing vibration of liquid benzene at 992 cm a standard for the measurement of relative Raman scattering cross sections of a number of compounds. When applying it as standard they made use of a divided spinning cell , developed by Kiefer and Topp (1974). 

Verstraeten has made the interesting suggestion that the ring-breathing vibration of the pyranoid ring causes infrared absorption (at 781 5 cm.- ) only when there is instability in the conformation adopted by the pyranose sugar, but the basis of this correlation was not explained. 

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