Interpreting the infrared spectrum of phenol

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US K12 grade 11 grade 12 organic chemistry courses involving molecular spectroscopy analysing infrared spectra of phenol

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Spectra obtained from a liquid film of phenol. The right-hand part of the of the infrared spectrum of phenol, wavenumbers ~1500 to 400 cm^-1 is considered the fingerprint region for the identification of phenol and most organic compounds. It is due to a unique set of complex overlapping vibrations of the atoms of the molecule of phenol.

Interpretation of the infrared spectrum of phenol

The most prominent infrared absorption lines of phenol

The most characteristic absorption band is the broad O-H stretching vibration bands at wavenumbers ~3550 to 3230 cm^-1, the breadth is caused by interference of hydrogen bonding interactions, common to all hydrogen bonded molecules with a hydroxyl group.

The intermolecular hydrogen bond C₆H₅-O^δ--H^δ+ǁǁǁ:O^δ--C₆H₅ in phenol.

There are C-O stretching vibration absorption bands at wavenumbers 1410 to 1310 and 1230 to 1140 cm^-1.

The absence of other specific functional group bands will show that a particular functional group is absent from the phenol molecular structure.