GENERAL FEATURES OF INFRARED SPECTRA

Almost all organic compounds contain C-H bonds and this means that there is invariably an absorption band in the IR spectrum between 2900 and 3100 cm at the C-H stretching frequency. 

Molecules generally have a large number of bonds and each bond may have several IR-active vibrational modes. IR spectra are complex and have many overlapping absorption bands. IR spectra are sufficiently complex that the spectmm for each compound is unique and this makes IR spectra very useful for identifying compounds by direct comparison with spectra from authentic samples fingerprinting ). 

The characteristic IR vibrations are influenced strongly by small changes in molecular structure, thus making it difficult to identify stmctural fragments from IR data alone. However, there are some groups of atoms that are readily recognised from IR spectra. IR chromophores are most useful for the determination of structure if  

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