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Interpreting and explaining the
Carbon-13 NMR spectrum of cyclopropane
[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 analysis of
cyclopropane
[spectra page updated
Mar 23rd 2026 *]
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13C NMR spectrum of
cyclo-C3H6
Links associated with cyclopropane
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C-13
NMR spectroscopy - spectra index
See also
comparing the infrared, mass, 1H
NMR and 13C NMR
spectra of propane, cyclopropane and propene
Introductory note on the 13C NMR spectrum of cyclopropane
Students and teachers please note that my explanation of the
carbon-13 NMR spectrum of cyclopropane is designed for advanced, but
pre-university, chemistry courses.
The description does not involve
the chemical shift δ
spin-spin coupling effects for cyclopropane 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 cyclopropane molecule.
The most common solvent used for investigating the C13 NMR
spectrum of compounds like cyclopropane, 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 - cyclopropane here.
Cyclopropane C3H6,
 ,
The molecular structure and
naming of alkanes
Interpreting the C-13 NMR spectrum of cyclopropane
As you can see from the diagram above there is only
one chemical shift line in the C-13 NMR spectrum of
cyclopropane
indicating only one chemical environments of the 3 carbon
atoms of cyclopropane, because of its simple symmetry.
13C chemical shift
(a) -2.7 ppm on the C-13 NMR
spectrum diagram for cyclopropane.
Note that you can have a negative carbon-13 NMR
chemical shift.
All three carbon
atoms in cyclopropane are equivalent to each other and their
13C fields cannot cause spin-spin coupling splitting
effects in the carbon-13 NMR spectrum.
The carbon-13 NMR spectra provides direct evidence of
only one carbon atom environment for the 3 carbon atoms in the
cyclopropane molecule,
deduced from the presence of only one13C NMR chemical
shift (ppm).
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Comparing the infrared, mass, 1H NMR and 13C NMR
spectra of propane, cyclopropane and propene
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 ethane and
ethene image sizes. |
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Comparing the
infrared
spectra of propane, propene and cyclopropane.
Cyclopropane and propene are structural isomers of molecular formula C3H6.
Propane
and propene exemplify the infrared spectra of lower members of the alkane
and alkene homologous series of CnH2n+2 and CnH2n
hydrocarbon
molecules where n = 3. |
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INFRARED SPECTRA
(above):
Apart from the significant differences in the fingerprint region at
wavenumbers 1500 to 400 cm-1, the most striking
differences are: (i) propene shows the characteristic absorption
at ~1700 cm-1 for the C=C stretching vibrations,
absent in the other two spectra, (ii) cyclopropane shows an absorption band
at 2200 cm-1, absent in the other two spectra, (iii)
propane has an absorption band at ~750 cm-1, absent
in the other two spectra. |
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Comparing the
mass
spectra of propane, propene and cyclopropane.
Cyclopropane and propene are structural isomers of molecular formula C3H6.
Propane
and propene exemplify the mass spectra of lower members of the alkane
and alkene homologous series of CnH2n+2 and CnH2n
hydrocarbon
molecules where n = 3. |
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MASS SPECTRA (above):
All three hydrocarbons show some similarities in their mass
spectra e.g. m/z ions 26 to 28 for [C2Hx]+
(x = 2 to 4) and m/z 14 and 15 ions - but these are found in
most aliphatic hydrocarbon spectra. The molecular ion peaks will
be the same for the isomeric propene and cyclopropane (m/z 42)
but that of propane will be 2 mass units higher at m/z 44. The
base ion peak m/z values are all different, propane 29, propene
41 and cyclopropane 42. |
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Comparing the
1H proton NMR
spectra of propane, propene and cyclopropane.
Cyclopropane and propene are structural isomers of molecular formula C3H6.
Propane
and propene exemplify the 1H proton NMR spectra of lower members of the alkane
and alkene homologous series of CnH2n+2 and CnH2n
hydrocarbon
molecules where n = 3. |
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1H NMR SPECTRA (above): The 1H NMR spectra of
all three molecules give different proton ratios i.e. propane
3:1 (actually 6:2 in the molecule), propene 2:1:3 (spectrum and
molecule) and cyclopropane just a singlet for the six protons,
so all three can be distinguished from each other by their
1H NMR spectra.. |
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Comparing the
carbon-13 NMR
spectra of propane, propene and cyclopropane.
Cyclopropane and propene are structural isomers of molecular formula C3H6.
Propane
and propene exemplify the carbon-13 NMR spectra of lower members of the alkane
and alkene homologous series of CnH2n+2 and CnH2n
hydrocarbon
molecules where n = 3. |
|
13C NMR SPECTRA
(above): The
13C NMR spectra of the three molecules show different numbers of
carbon-13 chemical environments i.e propane 2, propene 3 and cyclopropane
only 1, so all three could be distinguished from each other. |
Key words & phrases: C3H6 Interpreting the C-13 NMR spectra of
cyclopropane, C-13 nmr spectrum of cyclopropane, understanding the
carbon-13 nmr spectrum of cyclopropane, explaining the line pattern in the high
resolution C-13 nmr spectra of cyclopropane, revising the C-13 nmr spectrum of
cyclopropane, ppm
chemical shifts of the C-13 nmr spectrum of cyclopropane, how to construct the diagram of
the C-13 nmr spectrum of cyclopropane, how to analyse the chemical shifts in the
carbon-13 NMR spectrum of cyclopropane deducing the chemical environment of all the
carbon atoms in cyclopropane examining the c13 nmr spectrum of
cyclopropane analysing the
13-c nmr spectrum of cyclopropane how do you sketch and interpret the C-13 NMR spectrum
of cyclopropane interpreting interpretation of the C-13 NMR spectrum of
cyclopropane
assignment of chemical shifts in the 13C
NMR spectrum of cyclopropane type cycloalkane functional group
Molecular structure diagram of the
carbon-13 NMR diagram for the 13C NMR spectrum of cyclopropane. Deducing the number
of different chemical environments of the carbon atoms in the cyclopropane molecule
from the 13C chemical shifts in the carbon-13 NMR spectrum of cyclopropane. Revision
notes on the carbon-13 NMR spectrum of cyclopropane. Matching and deducing the
structure of the cyclopropane molecule from its 13C NMR spectrum.How do you interpret the chemical shifts of the C-13 NMR spectrum
of cyclopropane How to interpret the C-13 NMR spectrum of
cyclopropane Explanatory diagram of the 13C C-13 carbon-13 NMR spectrum of the number of different carbon atom
environments in the cyclopropane molecule from its carbon-13 NMR spectrum to
help work out the molecular structure of the cyclopropane molecule? The uses
and distinctive features of the carbon-13 NMR spectrum of the
cyclopropane
molecule explained. What do the number and values of the chemical
shifts from the c-13 carbon-13 NMR spectrum tell us about the
cyclopropane
molecule? explaining the decoupled carbon-13 NMR spectrum of
cyclopropane
with a detailed interpretation diagram of all the C-13 chemical shifts and
intensities
Links associated
with
cyclopropane
The chemistry of ALKANES
revision notes INDEX
The
infrared spectrum of cyclopropane
The mass
spectrum of cyclopropane
The H-1 NMR of cyclopropane
C-13
NMR spectroscopy index
ALL SPECTROSCOPY INDEXES
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Chemistry Notes
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