Ring and Other Group Vibrations

We shall also find good group frequencies for rings, such as those in benzene compounds. In most instances the vibration involves a CH group, so that again the small mass of hydrogen is the prime factor which makes these vibrations retain fairly constant spectral positions.  

Groups such as —C—NH2 also have distinctive group frequencies. Analysis of these group frequencies indicates that they are partly due to a combination of NH and C—or C=0 vibrations. Again, the force constants and mass factors involved in such a vibration remain fairly constant for the compounds in which the vibration is a good group frequency. 

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