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Interpreting the 13C NMR spectrum of
1-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 C-13 NMR spectrum of 1-chloro-2-methylpropane
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C-13 NMR 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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C-13
NMR spectroscopy - spectra index
See also
Comparing infrared, mass, 1H NMR & 13C NMR
spectra of the 4 structural isomers of C4H9Cl
Introductory note on the 13C NMR spectrum of
1-chloro-2-methylpropane
Students and teachers please note that my explanation of the
carbon-13 NMR spectrum of 1-chloro-2-methylpropane is designed for advanced, but
pre-university, chemistry courses.
The description does not involve
the chemical shift δ
spin-spin coupling effects for
1-chloro-2-methylpropane and the relative size of the carbon-13
NMR shifts does not give the ratio of the carbon atoms in the
different non-equivalent chemical environments of the
1-chloro-2-methylpropane molecule.
The most common solvent used for investigating the
13C
NMR
spectrum of compounds like 1-chloro-2-methylpropane, is CDCl3 and other
deuterated solvents.
TMS is the acronym for tetramethylsilane, formula Si(CH3)4,
whose 13C atoms are arbitrarily given a chemical shift of 0.0
ppm. This is the 'standard' in 13C NMR spectroscopy and all other
13C resonances, called chemical shifts, are measured with
respect to the TMS, and depend on the
individual (electronic) chemical environment of the 13C atoms in
an organic molecule - 1-chloro-2-methylpropane here.
 ,
 ,
 ,
 ,
1-chloro-2-methylpropane
For more see
Molecular structure, classification and
naming of
halogenoalkanes (haloalkanes)
Interpreting the C-13 NMR spectrum of 1-chloro-2-methylpropane
As you can see from the diagram above there are
3 different chemical shift lines in the C-13 NMR spectrum of
1-chloro-2-methylpropane
indicating 3 different chemical environments of the 4 carbon
atoms of 1-chloro-2-methylpropane.
(CH3)2CHCH2Cl
(Note the 3 different colours indicating the
3 different chemical environments of the carbon atoms in
1-chloro-2-methylpropane).
13C chemical shifts
(a) to (c) on the C-13 NMR
spectrum diagram for 1-chloro-2-methylpropane.
Note the decreasing effect on the
13C chemical shift as the
carbon atom is further from the more electronegative chlorine atom in 1-chloro-2-methylpropane.
The carbon-13 NMR spectra provides direct evidence of
3 different carbon atom environments for the 3 carbon atoms in the
1-chloro-2-methylpropane molecule,
deduced from the presence of 3 different 13C chemical
shifts (ppm).
Summary of the
C-13 NMR spectrum of 1-chloro-2-methylpropane and extra comments
The C-13 NMR spectrum of 1-chloro-2-methylpropane
with clarity and precision.
Overview of the
1-chloro-2-methylpropane molecule
1-chloro-2-methylpropane (also known as
isobutyl chloride) has the molecular formula C4H9Cl.
It contains three distinct carbon environments,
each giving rise to a separate signal in the C-13 NMR spectrum.
C-13
NMR Chemical Shifts Table for
1-chloro-2-methylpropane
| Carbon Label |
Environment |
Approx. δ
(ppm) |
Explanation |
| C1 |
CH2 directly bonded to Cl |
~45–50, 52.5 ppm |
Deshielded due to electronegative
chlorine pulling electron density |
| C2 |
CH connected to CH2 and CH3 |
~25–30, 31.1 ppm |
Slightly deshielded tertiary carbon |
| C3 = C4 |
CH3 attached to C2 |
~20–25, 20.1 ppm |
Methyl group on a secondary carbon |
(CH3)2CHCH2Cl
Note: C3 and C4 are equivalent methyl groups, so they appear as a
single peak in the spectrum.
Note: Exact chemical shifts may vary slightly depending on
solvent and instrument, but the relative positions and patterns
remain consistent.
Common
Misconceptions about the
C-13 NMR spectrum of 1-chloro-2-methylpropane
(see also below)
- “Only hydrogen atoms show up in NMR” — Not
true! C-13 NMR focuses on carbon environments.
- “Each carbon gives a peak regardless of symmetry”
— Equivalent carbons (like the two CH₃ groups here) give one
combined signal.
- “Chlorine causes splitting” — In C-13 NMR,
proton decoupling is typically used, so peaks
appear as singlets.
Exam
Tips for questions involving the
C-13 NMR spectrum of 1-chloro-2-methylpropane
(see also above)
- Count unique carbon environments — symmetry
helps reduce the number of signals.
- Electronegative atoms like Cl shift signals downfield
— expect higher δ values.
- Use molecular structure to predict equivalence
— draw it out and label carbons.
- Don't confuse C-13 with H-1 NMR — they reveal
different types of information.
|
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 Interpreting the C-13 NMR spectra of
1-chloro-2-methylpropane, C-13 nmr spectrum of 1-chloro-2-methylpropane, understanding the
carbon-13 nmr spectrum of 1-chloro-2-methylpropane, explaining the line pattern in the high
resolution C-13 nmr spectra of 1-chloro-2-methylpropane, revising the C-13 nmr spectrum of
1-chloro-2-methylpropane, ppm
chemical shifts of the C-13 nmr spectrum of 1-chloro-2-methylpropane, how to construct the diagram of
the C-13 nmr spectrum of 1-chloro-2-methylpropane, how to analyse the chemical shifts in the
carbon-13 NMR spectrum of 1-chloro-2-methylpropane deducing the chemical environment of all the
carbon atoms in 1-chloro-2-methylpropane examining the c13 nmr spectrum of
1-chloro-2-methylpropane analysing the
13-c nmr spectrum of 1-chloro-2-methylpropane how do you sketch and interpret the C-13 NMR spectrum
of 1-chloro-2-methylpropane interpreting interpretation of the C-13 NMR spectrum
of 1-chloro-2-methylpropane
assignment of chemical shifts in the 13C
NMR spectrum of
isobutyl
chloride Molecular structure diagram of the
carbon-13 NMR diagram for the 13C NMR spectrum of 1-chloro-2-methylpropane. Deducing the number
of different chemical environments of the carbon atoms in the
1-chloro-2-methylpropane molecule
from the 13C chemical shifts in the carbon-13 NMR spectrum of
1-chloro-2-methylpropane. Revision
notes on the carbon-13 NMR spectrum of 1-chloro-2-methylpropane. Matching and deducing the
structure of the 1-chloro-2-methylpropane molecule from its 13C NMR spectrum.
Carbon-13 NMR spectroscopy of aliphatic
halogenoalkanes haloalkanes alkyl halides alkyl chlorides chloroalkanes,
13C NMR spectra of 1-chloro-2-methylpropane, an isomer of molecular formula
C4H9Cl How do you interpret the chemical shifts of the C-13 NMR spectrum
of 1-chloro-2-methylpropane How to interpret the C-13 NMR spectrum of
1-chloro-2-methylpropane Explanatory diagram of the 13C C-13 carbon-13 NMR spectrum of the
1-chloro-2-methylpropane molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in
the carbon-13 NMR spectrum of 1-chloro-2-methylpropane. How to explain the C-13 NMR
spectrum of 1-chloro-2-methylpropane. How to deduce the number of different carbon atom
environments in the 1-chloro-2-methylpropane molecule from its carbon-13 NMR spectrum to
help work out the molecular structure of the
1-chloro-2-methylpropane molecule? The uses
and distinctive features of the carbon-13 NMR spectrum of the
1-chloro-2-methylpropane
molecule explained. What do the number and values of the chemical
shifts from the c-13 carbon-13 NMR spectrum tell us about the
1-chloro-2-methylpropane
molecule?
Links associated
with
1-chloro-2-methylpropane
The chemistry of HALOGENOALKANES (haloalkanes)
revision notes INDEX
The infrared
spectrum of 1-chloro-2-methylpropane (isobutyl
chloride)
The mass
spectrum of 1-chloro-2-methylpropane (isobutyl
chloride)
The H-1 NMR
spectrum of 1-chloro-2-methylpropane (isobutyl
chloride)
C-13
NMR spectroscopy index
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