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Advanced Organic Chemistry: 1H proton NMR spectrum of ethane

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

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 ethane

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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 ethane low/high resolution diagrams C2H6 CH3CH3 analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for ethane 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 - ethane here.

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

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Interpreting the H-1 NMR spectrum of ethane

In terms of spin-spin coupling from the possible proton magnetic orientations, for ethane there are no non-equivalent protons on adjacent carbon atoms

CH3CH3

All six protons are equivalent to each other and no line splitting occurs.

All you see is one chemical shifts (a) of 0.74 ppm on the H-1 NMR spectrum diagram for ethane.

Although there are 6 hydrogen atoms in the molecule, there is only 1 possible chemical environment for the hydrogen atoms in ethane molecule.

(No need for the n+1 rule to ethane and make some predictions using some colour coding!

The appearance of just one peak in the H-1 NMR spectrum of ethane, tells you unambiguously, that all the protons are equivalent to each other - in the same chemical environment, albeit as 2 x CH3 methyl groups. which do NOT split each other.

BEWARE of diagrams on the internet via Google images - I came across one example of the proton NMR spectrum of ethane drawn as a 1:3:3:1 quartet, which is completely wrong, it is just a single singlet resonance line.

Note that the even simpler molecule of methane CH4, will also only give one singlet peak on a H-1 proton NMR spectrum.


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. The 1H chemical shift for ethane is much lower.

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 ethane

The chemistry of ALKANES revision notes INDEX

The infrared spectrum of ethane

The mass spectrum of ethane

The C-13 NMR spectrum of ethane

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

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