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Interpreting and
explaining the 1H
hydrogen-1 (proton) NMR spectrum of cyclopropane
[Author
©
Dr Phil Brown GRIC, 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
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1H NMR spectrum of
cyclo-C3H6
Links associated with cyclopropane
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H-1 proton 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 1H NMR spectra of cyclopropane
Students and teachers please note my explanation of the
proton NMR spectrum of cyclopropane is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
cyclopropane are
confined to a proton spin-spin
coupling effects analysed using the n+1 rule for adjacent
non-equivalent proton fields (n is the number of neighbouring
protons in a non-equivalent different chemical environment for the
cyclopropane molecule).
It is assumed that the integrated intensities of the
1H
NMR δ
chemical shifts give the ratio of the protons in the different
non-equivalent chemical environments of the cyclopropane molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like cyclopropane, is CDCl3 and other
deuterated solvents to avoid confusion with a 1H NMR
signal, 2D (2H) has a different NMR chemical
shift.
TMS is the acronym for tetramethylsilane, formula Si(CH3)4,
whose protons are arbitrarily given a chemical shift of 0.0 ppm.
This is the 'standard' in 1H NMR spectroscopy and all
other proton shifts, called chemical shifts, depend on the
individual (electronic) chemical environment of the hydrogen atoms
in an organic molecule - cyclopropane here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of cyclopropane represent the peaks of the intensity of
the chemical shifts of (which are often groups of split lines at
high resolution) AND the relative integrated areas under the peaks
gives you the ratio of protons in the different chemical
environments of the cyclopropane molecule.
Cyclopropane C3H6,
 ,
The molecular structure and
naming of alkanes
Interpreting the
H-1 NMR spectrum of
cyclopropane
All eight hydrogen atoms are equivalent as
cyclopropane is a highly symmetrical molecule, the three carbon
atoms are in the same plane with the protons distributed
symmetrically above and below the plane of the triangle of
carbon atoms.
All 3 hydrogen
atoms in cyclopropane are equivalent to each other and their
1H fields cannot cause spin-spin coupling
splitting effects in the hydrogen-1 NMR spectrum.
Therefore only one
1H
Chemical shift of 0.20 ppm is observed and with no splitting -
because there are no
neighbouring non-equivalent protons.
The presence of one
non-split proton H-1 NMR
resonance shows that all 6 protons occupy the same
chemical environment.
The molecule is
completely symmetrical with a C-C-C bond angle of 60o,
so a highly strained reactive ring.
Adding D2O to the sample under investigation,
dissolved in CDCl3, makes no difference to
the 1H NMR spectrum of cyclopropane because there are
no labile protons
to exchange with deuterium (2H) e.g. as in
alcohols (O-H)
or amines (N-H).
The splitting pattern from proton
spin-spin coupling effects is analysed using the n+1 rule for
adjacent non-equivalent proton fields (n is the number of
neighbouring protons in a non-equivalent different chemical
environment).
|
Number of protons 1H
causing splitting |
Splitting pattern produced from the
n+1 rule and the theoretical ratio of line intensities |
|
0
means no splitting |
|
|
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1 |
|
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|
|
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1
creates a doublet |
|
|
|
|
|
1 |
|
1 |
|
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2
creates a triplet |
|
|
|
|
1 |
|
2 |
|
1 |
|
|
|
|
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3
creates a quartet |
|
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|
1 |
|
3 |
|
3 |
|
1 |
|
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|
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4
creates a quintet |
|
|
1 |
|
4 |
|
6 |
|
4 |
|
1 |
|
|
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5
creates a sextet |
|
1 |
|
5 |
|
10 |
|
10 |
|
5 |
|
1 |
|
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6
creates a septet |
1 |
|
6 |
|
15 |
|
20 |
|
15 |
|
6 |
|
1 |
|
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. |
 |
 |
 |
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. |
|
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. |
 |
 |
 |
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. |
|
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. |
 |
 |
 |
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. |
|
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.. |
 |
 |
 |
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: Interpreting the proton H-1 NMR spectra of
cyclopropane, low resolution & high resolution proton
nmr spectra of cyclopropane, H-1 nmr spectrum of cyclopropane, understanding the
hydrogen-1 nmr spectrum of cyclopropane, explaining the line splitting patterns in the
high resolution H-1 nmr spectra of cyclopropane, revising the H-1 nmr spectrum of
cyclopropane,
proton nmr of cyclopropane, ppm chemical shifts of the H-1 nmr spectrum of
cyclopropane,
explaining and analyzing spin spin line splitting in the H-1 nmr spectrum, how
to construct the diagram of the H-1 nmr spectrum of cyclopropane, how to work out the
number of chemically different protons in the structure of the cyclopropane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of cyclopropane using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of cyclopropane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of cyclopropane
examining the 1H nmr spectrum of cyclopropane analysing the 1-H nmr spectrum of
cyclopropane how do you sketch and interpret the H-1 NMR spectrum of
cyclopropane interpreting interpretation of the H-1
proton NMR spectrum of cyclopropane
Molecular structure diagram of the
proton NMR diagram for the 1H NMR spectrum of cyclopropane. The proton ratio in the
1H NMR spectrum of cyclopropane. Deducing the number of different chemical
environments of the protons in the cyclopropane molecule from the 1H chemical shifts
in the hydrogen-1 NMR spectrum of cyclopropane. Analysing the high resolution 1H NMR
spectrum of cyclopropane. Analysing the low resolution 1H NMR spectrum of
cyclopropane. You
may need to know the relative molecular mass of cyclopropane to deduce the molecular
formula from the proton ratio of the 1H NMR spectrum of cyclopropane. Revision notes
on the proton NMR spectrum of cyclopropane. Matching and deducing the structure of
the cyclopropane molecule from its hydrogen-1 NMR spectrum.
How do you interpret the H-1 NMR spectrum of
cyclopropane How to interpret
the H-1 NMR spectrum of cyclopropane Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the cyclopropane
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of cyclopropane. How to explain the H-1 NMR spectrum of
cyclopropane. The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the cyclopropane molecule. How to work out the molecular
structure of the cyclopropane molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the
cyclopropane
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the cyclopropane
molecule? explaining the spin-spin proton coupling effects in the 1H
NMR spectrum of cyclopropane.
interpretation
diagram explaining the proton splitting
pattern produced from the n+1 rule and the theoretical ratio of chemical shift
and values of intensities for the proton NMR spectrum lines of cyclopropane
Links associated
with
cyclopropane
The chemistry of ALKANES
revision notes INDEX
The
infrared spectrum of cyclopropane
The mass
spectrum of cyclopropane
The
C-13 NMR spectrum of cyclopropane
H-1 proton NMR spectroscopy index
(Please
read 8 points at the top of the 1H NMR index page)
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the spectroscopy of cyclopropane - its 1H NMR spectrum is fully analysed
and
suitable for use of pre-university students studying AQA advanced level
chemistry, Edexcel advanced level chemistry, OCR advanced level
chemistry, IB advanced level chemistry, WJEC (Eduqas) advanced level
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chemistry courses and they will also prove useful to
1st year undergraduate students of chemistry. |
