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The following table lists infrared spectroscopy absorptions by frequency regions.
The following table provides a collection of such data for the most common functional groups. Following the color scheme of the chart, stretching absorptions are listed in the blue-shaded section and bending absorptions in the green shaded part.
21 Οκτ 2024 · After completing this section, you should be able to use an infrared spectrum to determine the presence of functional groups, such as alcohols, amines and carbonyl groups, in an unknown compound, given a list of infrared absorption frequencies.
Table of Characteristic IR Absorptions m=medium, w=weak, s=strong, n=narrow, b=broad, sh=sharp frequency, cm –1 bond functional group 3640–3610 (s, sh) O–H stretch, free hydroxyl alcohols, phenols 3500–3200 (s,b) O–H stretch, H–bonded alcohols, phenols
Typical IR Absorption Frequencies For Common Functional Groups. Bond. Functional Group. Frequency in cm −1 (Intensity*) C–H. Alkane. 3000–2850 (s) –CH 3. 1450 and 1375 (m)
By learning where characteristic functional-group absorptions occur, it’s possible to get structural information from IR spectra. Table 12.1 lists the characteristic IR bands of some common functional groups.
Infrared spectra are generally informative about what functional groups are present, but not always. The 1H and 13C NMR’s are often just as informative about functional groups, and sometimes even more so in this regard.
