In A-level Chemistry, infrared (IR) spectroscopy is usually taught as part of
organic analysis or analytical techniques.
What students are expected to know
Purpose of IR spectroscopy:
Bonds in molecules absorb infrared radiation at characteristic wavenumbers,
allowing chemists to identify substances.
Functional-group identification:
Students should be able to use IR spectra to identify particular bonds and therefore
recognise functional groups in organic compounds.
Reading spectra:
Students are expected to use wavenumber data tables or chemistry data sheets to match
absorption peaks to likely bonds.
Fingerprinting:
Spectra can be compared with known reference spectra to identify a molecule.
Impurities:
IR spectra may also be used to detect impurities in a sample.
Using IR with other methods:
IR evidence is often combined with mass spectrometry and NMR to deduce empirical,
molecular, and structural formulae.
Common absorptions students may need to recognise
C–H stretching in alkanes, alkenes, and aldehydes
C=C stretching in alkenes
O–H stretching in alcohols
C=O stretching in aldehydes and ketones
C=O stretching and broad O–H stretching in carboxylic acids
N–H stretching in amines
In summary: the A-level IR spectroscopy syllabus focuses on how bond
vibrations produce absorption peaks, how to identify key functional groups from spectra,
how fingerprinting works, and how IR data can be combined with other analytical evidence.
Exam-board examples
AQA: functional-group identification, impurity detection, fingerprinting, and greenhouse-gas absorption.
Edexcel: explicit recognition of several common IR absorptions and use of IR with other analytical data.
OCR A: IR spectroscopy included under analytical techniques in core organic chemistry.