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Advanced Organic Chemistry: Carbon-13 NMR spectrum of propene

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Interpreting the Carbon-13 NMR spectrum of propene ('propylene')

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US K12 grade 11 grade 12 organic chemistry courses involving molecular spectroscopy analysing C-13 NMR spectra of propene

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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

13C nmr spectrum of propene C3H6 CH3CH=CH2 analysis of chemical shifts ppm interpretation of C-13 chemical shifts ppm of propene C13 13-C nmr doc brown's advanced organic chemistry revision notes 

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, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b, alkenes structure and naming (c) doc b

Interpreting the C-13 NMR spectrum of propene

As you can see from the diagram above there are 3 different 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 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).

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: 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.


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

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