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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
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Infrared spectroscopy - spectra index
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
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.
R-O–Hδ+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
Infrared spectroscopy index
ALL SPECTROSCOPY INDEXES
All Advanced Organic
Chemistry Notes
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