Characteristic Group Frequencies

the identical or nearly identical vibrational frequencies of specific groups of atoms in various molecules that correspond to specific chemical bonds, such as C—H, C—C, C═C, C—Cl.

The stability of such frequencies is associated with the preservation of the dynamic properties of identical groups of atoms in different molecules. In many cases, it is possible to determine theoretically whether a given chemical group possesses characteristic group frequencies. The intensities of the spectral lines corresponding to the characteristic group frequencies of a particular chemical group in various molecules often have similar values. The existence of characteristic group frequencies in molecular spectra makes it possible to draw conclusions about molecular structure; the frequencies are of great importance in spectral analysis. The rates of chemical processes can be evaluated on the basis of changes in intensity of characteristic group frequencies.