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Interpreting the infrared
spectrum of 2-chloro-2-methylpropane
[Author
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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
2-chloro-2-methylpropane
[updated
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infrared spectrum of (CH3)3CCl
(tert-butyl chloride)
Links associated
with 2-chloro-2-methylpropane
The
chemistry of organic halogen compounds
This is a BIG
chemistry website, please take time to explore it
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
2-chloro-2-methylpropane
Students and teachers please note
my explanation of the infrared
spectrum of 2-chloro-2-methylpropane is designed
for advanced, but pre-university, chemistry courses.
Based in
the infrared spectrum diagram for 2-chloro-2-methylpropane, only some of the most
prominent peaks for particular bond vibrations are discussed,
particularly if 2-chloro-2-methylpropane has a functional group with a particular
characteristic wavenumber peak.
The infrared spectrum of
2-chloro-2-methylpropane is
unique and the whole, or selected wavenumbers, can be used to
fingerprint its identity, sometimes analysing a mixture
containing 2-chloro-2-methylpropane or following its change of concentration in a
reaction.
Spectra obtained from a liquid film of
2-chloro-2-methylpropane. The right-hand part of the of the
infrared spectrum of 2-chloro-2-methylpropane, wavenumbers
~1500 to 400
cm-1 is considered the fingerprint region for the
identification of 2-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
2-chloro-2-methylpropane.
 ,
 ,
 ,
 ,
2-chloro-2-methylpropane
For more see
Molecular structure, classification and
naming of
halogenoalkanes (haloalkanes)
Interpretation of
the infrared spectrum of 2-chloro-2-methylpropane
The most prominent infrared absorption lines of
2-chloro-2-methylpropane
For 2-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 2-chloro-2-methylpropane with alkyl structures in them.
C-C-C skeletal vibrations from the C-(CH3)3
grouping occur at wavenumbers ~1255 to 1200 cm-1 and 750
to 720 cm-1.
Characteristic groups of C-Cl vibration absorptions
at wavenumbers ~580 to 780 cm-1 that you expect in
halogenoalkane molecules like 2-chloro-2-methylpropane.
The absence of other specific functional group bands
will show that a particular functional group is absent from the
2-chloro-2-methylpropane
molecular
structure.
Summary of the
infrared
spectrum of 2-chloro-2-methylpropane and extra comments
A structured breakdown of the
infrared spectrum of 2-chloro-2-methylpropane (tert-butyl chloride),
tailored for exam clarity and misconception-busting.
Prominent IR
Absorptions
the infrared
spectrum of 2-chloro-2-methylpropane
| Bond /
Vibration Type |
Wavenumber
Range (cm⁻¹) |
Interpretation / Notes |
| C–H stretching (alkyl) |
2880–3080 |
Present in methyl and tertiary alkyl
groups |
| C–H bending (CH3
deformation) |
1350–1470 |
Symmetric and asymmetric bending of
methyl groups |
| C–C skeletal vibrations |
1255–1200 and 750–720 |
From the (CH3)3C–
group; useful in fingerprinting |
| C–Cl stretching (halogenoalkane) |
580–780 |
Key diagnostic peak for chloroalkanes |
| Fingerprint region |
1500–400 |
Simplified due to molecular symmetry |
Common
Misconceptions
about the infrared
spectrum of 2-chloro-2-methylpropane
(see also below)
- Expecting an O–H stretch:
Some students assume all small organic molecules show a broad O–H stretch
(~3200–3600 cm⁻¹). Remind them tert-butyl chloride lacks hydroxyl groups.
- Confusing C–Cl with C–O:
The C–Cl stretch (~580–780 cm⁻¹) may be misidentified as C–O (~1000–1300
cm⁻¹). Emphasize the absence of oxygen.
- Overinterpreting the fingerprint
region: Learners may try to
assign every peak. Encourage focus on functional group regions unless
comparing known spectra.
Exam Tips for
questions involving
the infrared
spectrum of 2-chloro-2-methylpropane
(see also above)
- Functional group identification:
Highlight the presence of C–Cl and absence of O–H or C=O. This helps
eliminate alcohols or carbonyls in MCQs.
- Compare with t-butanol:
A classic contrast—t-butanol shows a broad O–H stretch and C–O stretch, both
absent in tert-butyl chloride.
- Use symmetry clues:
The simplified fingerprint region due to tert-butyl symmetry can help
distinguish it from less symmetrical isomers.
- Watch for distractors:
IR questions often include spectra with overlapping alkyl features. Train to
spot the unique C–Cl stretch.
|
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)3CCl image and diagram explaining the infrared spectrum
of 2-chloro-2-methylpropane, complete infrared absorption spectrum of
2-chloro-2-methylpropane, comparative spectra of
2-chloro-2-methylpropane, prominent peaks/troughs for identifying functional groups in the infrared spectrum of
2-chloro-2-methylpropane,
important wavenumber values in cm-1 for peaks/troughs in the infrared spectrum
of 2-chloro-2-methylpropane, revision of infrared spectroscopy of
2-chloro-2-methylpropane, fingerprint region analysis of
2-chloro-2-methylpropane, how to identify 2-chloro-2-methylpropane from its infrared spectrum, identifying organic
compounds like 2-chloro-2-methylpropane from their infrared spectrum,
how to analyse the absorption bands in the infrared spectrum of
2-chloro-2-methylpropane detection of functional groups in the
2-chloro-2-methylpropane molecule example of the infrared spectrum of a
molecule like 2-chloro-2-methylpropane with a functional group
interpreting interpretation of the infrared spectrum of
2-chloro-2-methylpropane shows presence
of functional group
tert-butyl chloride Diagram of absorption of wavenumber
peaks in the infrared spectrum of 2-chloro-2-methylpropane. Characteristic peak wavenumbers in the infrared
spectrum of 2-chloro-2-methylpropane. Finger print identification pattern using the infrared
spectrum of 2-chloro-2-methylpropane. Revision notes on the infrared spectrum of
2-chloro-2-methylpropane. Matching
and deducing the structure of the 2-chloro-2-methylpropane molecule from its infrared
spectrum. Infrared spectroscopy of aliphatic
halogenoalkanes haloalkanes alkyl halides alkyl chlorides chloroalkanes, infrared spectra of
2-chloro-2-methylpropane, an isomer of molecular formula C4H9Cl How do you interpret the infrared absorption spectrum of
2-chloro-2-methylpropane How
to interpret the infrared spectrum of 2-chloro-2-methylpropane Explanatory diagram of the infrared spectrum of the
2-chloro-2-methylpropane molecule
in terms of its molecular structure.
Listing data of the prominent main wavenumber peaks troughs in the infrared
spectrum of 2-chloro-2-methylpropane. How to explain the infrared spectrum of
2-chloro-2-methylpropane. Use of
the infrared spectrum of 2-chloro-2-methylpropane, identification of
2-chloro-2-methylpropane from its
infrared spectrum - fingerprint wavenumber pattern to identify the
2-chloro-2-methylpropane
molecule. The uses of the infrared spectrum of the
2-chloro-2-methylpropane molecule. The
distinctive features of the infrared spectrum of the
2-chloro-2-methylpropane molecule
explained. explaining the peaks-trough of the transmittance of the infrared
spectrum of 2-chloro-2-methylpropane what does the infrared spectrum tell you about the
structure and properties of the 2-chloro-2-methylpropane molecule?
How is infrared spectrum of 2-chloro-2-methylpropane used to identify
2-chloro-2-methylpropane?
Links associated with 2-chloro-2-methylpropane
The chemistry of HALOGENOALKANES (haloalkanes)
revision notes INDEX
The mass
spectrum of 2-chloro-2-methylpropane (tert-butyl
chloride)
The H-1 NMR
spectrum of 2-chloro-2-methylpropane (tert-butyl
chloride)
The C-13
NMR spectrum of 2-chloro-2-methylpropane (tert-butyl
chloride)
Infrared spectroscopy index
ALL SPECTROSCOPY INDEXES
All Advanced Organic
Chemistry Notes
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revision notes on the spectroscopy of
2-chloro-2-methylpropane - its infrared spectrum are
suitable for use of pre-university students studying AQA
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advanced level chemistry, IB advanced level chemistry, WJEC
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