2.12b: use infrared spectra, or data from infrared spectra, to deduce functional groups present in organic compounds and predict infrared absorptions, given wavenumber data, due to familiar functional groups. This will be limited to: (i) C–H stretching absorptions in alkanes, alkenes and aldehydes (ii) O–H stretching absorption in alcohols and carboxylic acids (iii) N–H stretching absorption in amines (iv) C=O stretching absorption in aldehydes and ketones (v) C–X stretching absorption in halogenoalkanes (vi) as an analytical tool to show the change in functional groups during the oxidation of an alcohol to a carbonyl

Infrared spectroscopy is useful for identifying the functional groups present in a molecule

• provides a “fingerprint” of a known substance that can be compared with unknown substances to identify them and determine purity

An absorption spectrum shows how strongly a chemical absorbs radiation over a range of frequencies

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