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Interpreting the infrared
spectrum of 1-chloro-2-methylpropane
[Author
©
Dr
Phil Brown PhD:
Doc Brown's advanced level organic chemistry exam revision notes
suitable for students of UK A level chemistry courses & US K12 grade
11, grade 12 and AP honors chemistry courses: Molecular
spectroscopy - analysing the
infrared spectrum of
1-chloro-2-methylpropane
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infrared spectrum of
(CH3)2CHCH2Cl
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LINKS associated
with 1-chloro-2-methylpropane
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The
chemistry of organic halogen compounds
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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
Introductory note on the infrared spectrum of
1-chloro-2-methylpropane
Students and teachers please note
my explanation of the infrared
spectrum of 1-chloro-2-methylpropane is designed
for advanced, but pre-university, chemistry courses.
Based in
the infrared spectrum diagram for 1-chloro-2-methylpropane, only some of the most
prominent peaks for particular bond vibrations are discussed,
particularly if 1-chloro-2-methylpropane has a functional group with a particular
characteristic wavenumber peak.
The infrared spectrum of
1-chloro-2-methylpropane is
unique and the whole, or selected wavenumbers, can be used to
fingerprint its identity, sometimes analysing a mixture
containing 1-chloro-2-methylpropane or following its change of concentration in a
reaction.
Spectra obtained from a liquid film of
1-chloro-2-methylpropane. The right-hand part of the of the
infrared spectrum of 1-chloro-2-methylpropane, wavenumbers
~1500 to 400
cm-1 is considered the fingerprint region for the
identification of 1-chloro-2-methylpropane and most organic compounds. It is due to a unique set
of complex overlapping vibrations of the atoms of the molecule of
1-chloro-2-methylpropane.
 ,
 ,
 ,
 ,
1-chloro-2-methylpropane
For more see
Molecular structure, classification and
naming of
halogenoalkanes (haloalkanes)
Interpretation of
the infrared spectrum of 1-chloro-2-methylpropane
The most prominent infrared absorption lines of
1-chloro-2-methylpropane
For 1-chloro-2-methylpropane you observe 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-chloro-2-methylpropane with alkyl structures in them.
C-C-C skeletal vibrations from the CH3-C-CH3
grouping occur at wavenumbers ~1140 to 1175 cm-1. and 840
to 790 cm-1.
Characteristic groups of C-Cl vibration absorptions
at wavenumbers ~580 to 780 cm-1 that you expect in
halogenoalkane molecules like 1-chloro-2-methylpropane.
The absence of other specific functional group bands
will show that a particular functional group is absent from the
1-chloro-2-methylpropane
molecular
structure.
Summary of the
infrared spectrum of 1-chloro-2-methylpropane and extra comments
The infrared (IR) spectrum of
1-chloro-2-methylpropane (isobutyl chloride) with clarity and exam
precision.
Overview of the
infrared spectrum of 1-chloro-2-methylpropane
1-chloro-2-methylpropane is a saturated
alkyl halide, so its IR spectrum is dominated by:
- C–H stretching and bending
(from alkyl groups)
- C–Cl stretching
(from the chloro substituent)
- Fingerprint region
with overlapping vibrations
Prominent
Wavenumbers Table
for the
infrared spectrum of 1-chloro-2-methylpropane
| Bond Type /
Vibration |
Wavenumber
Range (cm⁻¹) |
Assignment /
Notes |
| C–H stretch (alkane) |
2950–2850 |
Strong, sharp peaks from
methyl/methylene groups |
| C–H bend (scissoring) |
1470–1450 |
Medium intensity |
| C–H bend (rocking, methyl) |
1370–1350 |
Often seen in branched alkanes |
| C–Cl stretch |
850–550 |
Variable intensity, key for halogen ID |
| C–H wag (-CH₂Cl) |
1300–1150 |
Overlaps with other bending modes |
| Fingerprint region |
1500–400 |
Complex overlapping vibrations |
Common
Misconceptions
about the
infrared spectrum of 1-chloro-2-methylpropane
(see also below)
- Misidentifying C–Cl stretch:
Students often overlook the C–Cl stretch due to its
variable intensity and overlap with other bands.
- Assuming absence of functional
groups means no IR activity:
Even simple alkanes and halides show distinct C–H and C–X vibrations.
- Confusing fingerprint region with
noise: The fingerprint region
is rich in diagnostic detail, especially for compound identification.
Exam Tips for
questions involving
the
infrared spectrum of 1-chloro-2-methylpropane
(see also above)
- Use the C–Cl stretch to
confirm halogen presence — especially when comparing isomers or unknowns.
- Compare with known spectra:
IR is most powerful when used comparatively (e.g. with
2-chloro-2-methylpropane).
- Don’t ignore weak bands:
Even low-intensity peaks can be diagnostic in halogenated compounds.
- Label spectra clearly: In
exams, annotate key peaks with bond types and wavenumbers to show
understanding.
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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:
C4H9Cl
(CH3)2CH2Cl image and diagram explaining the infrared spectrum
of 1-chloro-2-methylpropane, complete infrared absorption spectrum of
1-chloro-2-methylpropane, comparative spectra of
1-chloro-2-methylpropane, prominent peaks/troughs for identifying functional groups in the infrared spectrum of
1-chloro-2-methylpropane,
important wavenumber values in cm-1 for peaks/troughs in the infrared spectrum
of 1-chloro-2-methylpropane, revision of infrared spectroscopy of
1-chloro-2-methylpropane, fingerprint region analysis of
1-chloro-2-methylpropane, how to identify 1-chloro-2-methylpropane from its infrared spectrum, identifying organic
compounds like 1-chloro-2-methylpropane from their infrared spectrum,
how to analyse the absorption bands in the infrared spectrum of
1-chloro-2-methylpropane detection of functional groups in the
1-chloro-2-methylpropane molecule example of the infrared spectrum of a
molecule like 1-chloro-2-methylpropane with a functional group
interpreting interpretation of the infrared spectrum of
1-chloro-2-methylpropane shows presence
of functional group
isobutyl
chloride Diagram of absorption of wavenumber peaks in the infrared spectrum of
1-chloro-2-methylpropane. Characteristic peak wavenumbers in the infrared
spectrum of 1-chloro-2-methylpropane. Finger print identification pattern using
the infrared spectrum of 1-chloro-2-methylpropane. Revision notes on the
infrared spectrum of 1-chloro-2-methylpropane. Matching and deducing the
structure of the 1-chloro-2-methylpropane molecule from its infrared
spectrum. Infrared spectroscopy of aliphatic halogenoalkanes haloalkanes alkyl
halides alkyl chlorides chloroalkanes, infrared spectra of
1-chloro-2-methylpropane, an isomer of molecular formula C4H9Cl How do you
interpret the infrared absorption spectrum of 1-chloro-2-methylpropane How to
interpret the infrared spectrum of 1-chloro-2-methylpropane Explanatory diagram
of the infrared spectrum of the 1-chloro-2-methylpropane molecule in terms of
its molecular structure. Listing data of the prominent main wavenumber peaks
troughs in the infrared spectrum of 1-chloro-2-methylpropane. How to explain the
infrared spectrum of 1-chloro-2-methylpropane. Use of the infrared spectrum of
1-chloro-2-methylpropane, identification of 1-chloro-2-methylpropane from its
infrared spectrum - fingerprint wavenumber pattern to identify the
1-chloro-2-methylpropane molecule. The uses of the infrared spectrum of the
1-chloro-2-methylpropane molecule. The distinctive features of the infrared
spectrum of the 1-chloro-2-methylpropane molecule explained. explaining the
peaks-trough of the transmittance of the infrared spectrum of
1-chloro-2-methylpropane what does the infrared spectrum tell you about the
structure and properties of the 1-chloro-2-methylpropane molecule?
Links associated with 1-chloro-2-methylpropane
The chemistry of HALOGENOALKANES (haloalkanes)
revision notes INDEX
The mass
spectrum of 1-chloro-2-methylpropane (isobutyl
chloride)
The H-1 NMR
spectrum of 1-chloro-2-methylpropane (isobutyl
chloride)
The C-13
NMR spectrum of 1-chloro-2-methylpropane (isobutyl
chloride)
Infrared spectroscopy index
ALL SPECTROSCOPY INDEXES
All Advanced Organic
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