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Advanced Organic Chemistry: Infrared spectrum of 3-hydroxybutanone

Interpreting the infrared spectrum of 3-hydroxybutanone  (acetoin)

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 3-hydroxybutanone

infrared spectrum of 3-hydroxybutanone C4H8O2 CH3COCH(OH)CH3 wavenumbers cm-1 functional group detection fingerprint pattern identification of acetoin doc brown's advanced organic chemistry revision notes 

Spectra obtained from a liquid film of 3-hydroxybutanone. The right-hand part of the of the infrared spectrum of 3-hydroxybutanone, wavenumbers ~1500 to 400 cm-1 is considered the fingerprint region for the identification of 3-hydroxybutanone and most organic compounds. It is due to a unique set of complex overlapping vibrations of the atoms of the molecule of 3-hydroxybutanone.

C4H8O2, 3-hydroxybutanone 3-hydroxybutan-2-one acetoin CH3COCH(OH)CH3 C4H8O2, 3-hydroxybutanone, 3-hydroxybutan-2-one, 'acetoin', CH3COCH(OH)CH3

Interpretation of the infrared spectrum of 3-hydroxybutanone

The most prominent infrared absorption lines of 3-hydroxybutanone.

3-hydroxybutanone has two functional groups, the carbonyl group C=O of a ketone and the hydroxyl group OH of an alcohol, so you expect both to feature in the infrared spectrum.

One of the most characteristic absorption bands 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.

In this case the O-H and C-H vibrations are clearly distinguishable - not always so, you often get quite an overlap to give an even larger broad absorption band.

infrared spectrum of ethanol diagram of intermolecular hydrogen bonding forces between liquid alcohol molecules doc brown A level organic chemistry revision notes R-OHδ+llllδ:O-R ... etc.

C-H stretching vibration absorption occurs ~2900 to 3000 cm-1, wavenumbers common to any molecule with alkyl groups.

The strongest and most characteristic absorption band of butanone is at wavenumbers ~1700 to 1725 cm-1 for the stretching vibrations of the carbonyl group bond C=O.

There are multiple C-H absorptions at wavenumbers ~1215 to 1435 cm-1, but non particularly characteristic of ketones or alcohols.

There are C-O stretching vibration absorption bands at wavenumbers ~1120 to 1030 cm-1. and 1350 to 1260 cm-1.

Other C-H stretching vibration absorptions appear at wavenumbers 1470 to 1370 cm-1.

The absence of other specific functional group bands will show that a particular functional group is absent from the 3-hydroxybutanone molecular structure.


Key words & phrases: C4H8O2 CH3COCH(OH)CH3 image and diagram explaining the infrared spectrum of 3-hydroxybutanone, complete infrared absorption spectrum of 3-hydroxybutanone, comparative spectra of 3-hydroxybutanone, prominent peaks/troughs for identifying functional groups in the infrared spectrum of 3-hydroxybutanone, important wavenumber values in cm-1 for peaks/troughs in the infrared spectrum of 3-hydroxybutanone, revision of infrared spectroscopy of 3-hydroxybutanone, fingerprint region analysis of 3-hydroxybutanone, how to identify 3-hydroxybutanone from its infrared spectrum, identifying organic compounds like 3-hydroxybutanone from their infrared spectrum, how to analyse the absorption bands in the infrared spectrum of 3-hydroxybutanone detection of ketone and hydroxyl functional groups in the 3-hydroxybutanone molecule example of the infrared spectrum of a molecule like 3-hydroxybutanone with a ketone and hydroxyl functional group  interpreting interpretation of the infrared spectrum of 3-hydroxybutanone shows presence of ketone and hydroxyl functional group 3-hydroxybutan-2-one acetoin


Links associated with 3-hydroxybutanone

The chemistry of ALCOHOLS revision notes INDEX

The chemistry of ALDEHYDES and KETONES revision notes INDEX

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