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Advanced Organic Chemistry: 1H NMR spectrum of ethene (ethylene)

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Interpreting the H-1 hydrogen-1 (proton) NMR spectrum of ethene (ethylene)

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 H-1 NMR spectra of ethene

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H-1 proton NMR spectroscopy - spectra index

See also comparing the infrared, mass, 1H NMR and 13C NMR spectra of ethane and ethene

1H proton nmr spectrum of ethene low/high resolution diagrams C2H4 CH2=CH2 analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for ethylene explaining spin-spin coupling for line splitting doc brown's advanced organic chemistry revision notes

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 resonances, called chemical shifts, are measured with respect to the TMS, and depend on the individual (electronic) chemical environment of the hydrogen atoms in an organic molecule - ethene here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of ethene 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 ethene molecule.

Ethene  C2H4 alkenes structure and naming (c) doc b  displayed formula of ethene alkenes structure and naming (c) doc b skeletal formula is only alkenes structure and naming (c) doc b

Interpreting the H-1 NMR spectrum of ethene

In terms of spin-spin coupling from the possible proton magnetic orientations, for ethene, no such interactions can take place due to the symmetry of the molecule.

The 4 hydrogen atoms (protons) of ethene occupy the same chemical environment so that the high or low resolution NMR spectra only shows one principal singlet peak for one H-1 NMR chemical shift only. (diagram above for ethene).

CH2=CH2

Chemical shift (a) 5.25 ppm on the H-1 NMR spectrum diagram for ethene.

Although there are 4 hydrogen atoms in the molecule, there is only one possible chemical environment for the hydrogen atoms in the ethene molecule.

So, there is no need to apply the n+1 rule to ethene because all the protons are equivalent to each other and therefore cannot cause splitting of their common single resonance line.


Number of directly adjacent protons 1H causing splitting Splitting pattern produced from the n+1 rule on spin-spin coupling and the theoretical ratio of line intensities
0 means no splitting             1            
1 creates a doublet           1   1          
2 creates a triplet         1   2   1        
3 creates a quartet       1   3   3   1      
4 creates a quintet     1   4   6   4   1    
5 creates a sextet   1   5   10   10   5   1  
6 creates a septet 1   6   15   20   15   6   1
Comparing the infrared, mass, 1H NMR and 13C NMR spectra of ethane and ethene

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.

INFRARED SPECTRA: Apart from the significant differences in the fingerprint region at wavenumbers 1500 to 400 cm-1, the most striking differences are (i) the band at ~1900 cm-1 for ethene, absent in the ethane spectrum, (ii) the bands at 800 cm-1 for ethane (CH3 vibrations), absent or much weaker in ethene, and (iii) the strong absorptions at ~1000 cm-1 for ethene, completely absent in the ethane spectrum.

MASS SPECTRA: Both ethane and ethene show some similarities in their mass spectra e.g. m/z ions 25 to 28 for [C2Hx]+ (x = 1 to 4) ions and in both cases the base ion peak has an m/z of 28. However, the molecular ion peaks will be different because of their different relative molecular masses i.e. ethane m/z 30 and ethene m/z 28. Ethane also has a prominent m/z ion peak of 29, which is tiny in the ethene mass spectrum (and only due to 1% 13C atoms in the parent molecular ion).

1H NMR SPECTRA: The 1H NMR spectra of ethane and ethene are similar in that that both give one single singlet resonance line in their proton NMR spectra. All the protons in each molecule are equivalent to each other and occupy the same chemical environment due to the symmetry of the molecule, so no resonance splitting. However the two 1H chemical shifts are significantly different due the different shielding effects of the -CH3 and =CH2 groupings respectively. Ethene has a much greater 1H NMR chemical shift.

13C NMR SPECTRA: The 1C NMR spectra of ethane and ethene are similar in that that both give one single resonance line in their carbon-13 NMR spectra. In both molecules the two carbon atoms occupy the same chemical environment due to the symmetry of the molecule.  However the two 13C chemical shifts are significantly different due the different shielding effects of the -CH3 and =CH2 groupings respectively.

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Links associated with ethene

The chemistry of ALKENES revision notes INDEX

The infrared spectrum of ethene ('ethylene')

The mass spectrum of ethene ('ethylene')

The C-13 NMR spectrum of ethene ('ethylene')

H-1 proton NMR spectroscopy index  (Please read 8 points at the top of the 1H NMR index page)

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