November 17, 2008
Infrared (IR) spectrometry can serve as a simple method to gather information on the presence of OH. Characteristic OH absorptions occur around the ranges of 3700-3200 cm-1 (OH stretching) and 1200-1000 cm-1 (OH bending). In the case of hydrogen-bonded OH, the band in the region 3700-3200 cm-1 generally appears broad and sometimes can go unnoticed.
Below is the IR spectrum for butanoic acid. The presence of the two bands at 3582 cm-1 and 1150 cm-1 suggest that an OH group is present.
TIP: An incorrect interpretation may occur for samples that contain impurities with OH groups, for example, water.