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Interpreting the infrared spectrum of
1-chlorobutane
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
1-chlorobutane
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Infrared spectroscopy - spectra index
See also
Comparing infrared, mass, 1H NMR & 13C NMR
spectra of the 4 structural isomers of C4H9Cl
Spectra obtained from a liquid film of 1-chlorobutane. The right-hand part of the of the
infrared spectrum of 1-chlorobutane, wavenumbers
~1500 to 400
cm-1 is considered the fingerprint region for the
identification of 1-chlorobutane and most organic compounds. It is due to a
unique set
of complex overlapping vibrations of the atoms of the molecule of
1-chlorobutane.
 ,
 ,
 ,
 ,
1-chlorobutane
For more see
Molecular structure, classification and
naming of
halogenoalkanes (haloalkanes)
Interpretation of
the infrared spectrum of 1-chlorobutane
The most prominent infrared absorption lines of
1-chlorobutane
For 1-chlorobutane you observe infrared C-H stretching vibrations at wavenumbers ~2880 to
3080 cm-1,
and C-H bending vibrations at wavenumbers ~1300 to 1500
cm-1.
These are typical infrared absorptions of molecules
like 1-chlorobutane with alkyl structures in them.
Characteristic groups of C-Cl vibrations at
wavenumbers ~580 to 780 cm-1
that you expect in halogenoalkane molecules like 1-chlorobutane.
The absence of other specific functional group bands
will show that particular functional group is absent from the
1-chlorobutane
molecular
structure.
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Comparing the infrared, mass, 1H NMR and 13C NMR
spectra of the 4 halogenoalkane isomers of C4H9Cl
NOTE: The images are linked to their
original detailed spectral analysis pages AND can be doubled in
size with touch screens to
increase the definition to the original 1-chlorobutane,
2-chlorobutane, 1-chloro-2-methylpropane and 2-chloro-2-methylpropane
image sizes. These four molecules
are structural isomers of molecular formula C4H9Cl
and
exemplify the infrared, mass, 1H NMR and 13C NMR spectra of lower
aliphatic halogenoalkanes (haloalkanes, alkyl halides,
chloroalkanes, alkyl chlorides). |
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INFRARED SPECTRA
(above):
Apart from the significant differences in the fingerprint region at
wavenumbers 1500 to 400 cm-1, there are no other
great striking differences, but each could be identified from
its infrared spectrum. The infrared spectrum of
2-chloro-2-methylpropane is noticeably simpler in the
fingerprint region, perhaps due to
the greater symmetry of the molecule. |
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MASS SPECTRA (above):
Theoretically, all four can give the parent molecular ions of
m/z 92 and 94, but they are all relatively tiny peaks.
2-chlorobutane and 2-chloro-2-methylpropane give a base ion peak
of m/z 57. The base ion peak for 1-chlorobutane is m/z 56 and
that of 1-chloro-2-methylpropane is m/z 43. Each gives different
patterns of pairs of m/z values two mass units apart, in the
peak height ratio of 3:1, if the positive fragment contains a
chlorine atom (35Cl or 37Cl) e.g look for
m/z pairs 49/51, 63/65 and 77/79 in their mass spectra. |
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1H NMR SPECTRA
(above): The 1H NMR spectra of all four molecules give different
integrated proton ratios i.e.1-chlorobutane
four peaks of ratio 3:2:2:2; 2-chlorobutane four peaks of
ratio 3:3:2:1,
1-chloro-2-methylpropane three peaks of ratio 6:2:1 and
2-chloro-2-methylpropane gives just one peak '1' (effectively no ratio
involved), so all four molecular structures can be distinguished from each other by their
1H NMR spectra proton ratios, numbers of peaks and (n+1)
rule splitting patterns. |
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13C NMR SPECTRA
(above): The
13C NMR spectra of the four molecules show various numbers of
carbon-13 chemical environments i.e 1-chlorobutane and
2-chlorobutane show four 13C NMR resonances,
1-chloro-2-methylpropane three 13C NMR resonances and
2-chloro-2-methylpropane only two 13C resonances (3 and 2
chemical environments respectively. Therefore
1-chloro-2-methylpropane and 2-chloro-2-methylpropane can be
distinguished from the other three by their number of resonances
in their 13C NMR spectra, but 1-chlorobutane and 2-chlorobutane
cannot be distinguished from each other from their number of 13C
NMR resonance lines - other data would be required. |
Key words & phrases: image and diagram of the infrared spectrum
of 1-chlorobutane, complete infrared absorption spectrum of 1-chlorobutane, comparative spectra of
1-chlorobutane, prominent peaks/troughs for identifying functional groups in the infrared spectrum of
1-chlorobutane,
important wavenumber values in cm-1 for peaks/troughs in the infrared spectrum
of 1-chlorobutane, revision of infrared spectroscopy of 1-chlorobutane, fingerprint region analysis of
1-chlorobutane, how to identify 1-chlorobutane from its infrared spectrum, identifying organic
compounds like 1-chlorobutane from their infrared spectrum, how to analyse the
absorption bands in the infrared spectrum of 1-chlorobutane
n-butyl chloride Diagram of absorption of wavenumber
peaks in the infrared spectrum of 1-chlorobutane. Characteristic peak wavenumbers in the infrared
spectrum of 1-chlorobutane. Finger print identification pattern using the infrared
spectrum of 1-chlorobutane. Revision notes on the infrared spectrum of
1-chlorobutane. Matching
and deducing the structure of the 1-chlorobutane molecule from its infrared
spectrum. Infrared spectroscopy of aliphatic
halogenoalkanes haloalkanes alkyl halides alkyl chlorides chloroalkanes, infrared spectra of
1-chlorobutane, an isomer of molecular formula C4H9Cl explaining the
infrared spectrum of 1-chlorobutane
Associated links
The chemistry of HALOGENOALKANES (haloalkanes)
revision notes INDEX
The mass spectrum of 1-chlorobutane
(n-butyl chloride)
The H-1 NMR spectrum of 1-chlorobutane
(n-butyl chloride)
The C-13 NMR
spectrum of 1-chlorobutane
(n-butyl chloride)
Infrared spectroscopy index
ALL SPECTROSCOPY INDEXES
All Advanced Organic
Chemistry Notes
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