 They exhibit a sharp band associated with vibration of the C–O vibration bond ("ν"C=O) between 1680 and 1725 cm−1.A characteristic "ν"O–H band appears as a broad peak in the 2500 to 3000 cm−1 region.By 1H NMR spectrometry, the hydroxyl hydrogen appears in the 10–13 ppm region, although it is often either broadened or not observed owing to exchange with traces of water.