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Interpreting and explaining the
13C NMR spectrum of propene
('propylene')
[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 - analysing the 13C NMR spectra of
propene
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13C NMR spectrum of H2C=CHCH3
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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 propene
Students and teachers please note that my explanation of the
carbon-13 NMR spectrum of propene is designed for advanced, but
pre-university, chemistry courses.
The description does not involve
the chemical shift δ
spin-spin coupling effects for propene 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 propene molecule.
The most common solvent used for investigating the
13C
NMR
spectrum of compounds like propene, 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 - propene here.
Propene,
 ,
 ,
 ,
 ,
 ,
An alkene
The molecular structure and naming of alkenes
Interpreting the C-13 NMR spectrum of propene
As you can see from the diagram above there are
3 different 13C chemical shift lines in the C-13 NMR spectrum of
propene
indicating 3 different chemical environments of the 3 carbon
atoms of propene.
CH2=CH-CH3
(Note the 3 different colours indicating the
3 different chemical environments of the 3 carbon atoms in propene).
13C chemical shifts (a) to (c) ppm on the C-13 NMR
spectrum diagram for propene.
(a) 13C NMR shift of 116 ppm for the
end CH2 group carbon.
(b) 13C NMR shift of 136 ppm for the CH group carbon.
(c) 13C NMR shift of 18 ppm for the CH3 group carbon
The carbon-13 NMR spectra provides direct evidence of
3 different carbon atom environments for the 3 carbon atoms in the
propene molecule,
deduced from the presence of 3 different 13C NMR chemical
shifts (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. |
|
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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 |
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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 H2C=CHCH3 CH3CH=CH2
CH2=CHCH3 Interpreting the C-13 NMR spectra of
propene, C-13 nmr spectrum of propene, understanding the
carbon-13 nmr spectrum of propene, explaining the line pattern in the high
resolution C-13 nmr spectra of propene, revising the C-13 nmr spectrum of
propene, ppm
chemical shifts of the C-13 nmr spectrum of propene, how to construct the diagram of
the C-13 nmr spectrum of propene, how to analyse the chemical shifts in the
carbon-13 NMR spectrum of propene deducing the chemical environment of all the
carbon atoms in propene examining the c13 nmr spectrum of propene analysing the
13-c nmr spectrum of propene how do you sketch and interpret the C-13 NMR spectrum
of propene interpreting interpretation of the C-13 NMR spectrum of propene
assignment of chemical shifts in the 13C
NMR spectrum of propene alkene functional group propylene Molecular structure diagram of the
carbon-13 NMR diagram for the 13C NMR spectrum of propene. Deducing the number
of different chemical environments of the carbon atoms in the propene molecule
from the 13C chemical shifts in the carbon-13 NMR spectrum of propene. Revision
notes on the carbon-13 NMR spectrum of propene. Matching and deducing the
structure of the propene molecule from its 13C NMR spectrum. How do you interpret the chemical shifts of the C-13 NMR spectrum
of propene How to interpret the C-13 NMR spectrum of
propene Explanatory diagram of the 13C C-13 carbon-13 NMR spectrum of the number of different carbon atom
environments in the propene molecule from its carbon-13 NMR spectrum to
help work out the molecular structure of the propene molecule? The uses
and distinctive features of the carbon-13 NMR spectrum of the
propene
molecule explained. What do the number and values of the chemical
shifts from the c-13 carbon-13 NMR spectrum tell us about the
propene
molecule? explaining the decoupled carbon-13 NMR spectrum of propene
with a detailed interpretation diagram of all the C-13 chemical shifts and
intensities
Links associated
with
propene
The chemistry of ALKENES
revision notes INDEX
The infrared spectrum of
propene ('propylene')
The
mass spectrum of propene ('propylene')
The H-1 NMR spectrum of
propene ('propylene')
C-13
NMR spectroscopy index
ALL SPECTROSCOPY INDEXES
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chemistry of haloalkanes
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chemistry of carboxylic acids and derivatives The chemistry of
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spectroscopy (13C NMR spectra of propene,
diagnostic features, data analysed, useful infrared spectra exam revision
comments)
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
chemistry, CIE advanced level chemistry, CCEA advanced level chemistry, US grade 11-12 AP honors
chemistry courses and they will also prove useful to
1st year undergraduate students of chemistry. |
