Correlation charts infrared absorption frequency

To extract structural information from infrared spectra, you must be familiar with the frequencies at which various functional groups absorb. You may consult infrared correlation tables, which provide as much infonnation as is known about where the various functional groups absorb. The references listed at the end of this chapter contain extensive series of correlation tables. Sometimes the absorption information is presented in the form of a chart called a correlation chart. Table 2.3 is a simplified correlation table a more detailed chart appears in Appendix 1. 

It must be emphasized, however, that the frequencies listed in various inorganic structure-spectra correlation charts are for the ionic salts. There are many instances in which the polyatomic anion (c.., NO3, SO4 , col , IO3) becomes coordinated to the cation, and this causes a lowering of the symmetry of the anion. These are anions that have double or triple degenerate vibrations. This is reflected in the infrared spectrum by additional absorptions because of the removal of the degeneracy. Many examples of this are illustrated in the transition-metal complexes involving the above anions [ ]. 

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