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Interpreting the
H-1 hydrogen-1 (proton) NMR spectrum of ethane
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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
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.
The alkane
ethane
 yes! just a dash!
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.
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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 |
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1 |
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| 1
creates a doublet |
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1 |
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1 |
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| 2
creates a triplet |
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1 |
|
2 |
|
1 |
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| 3
creates a quartet |
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1 |
|
3 |
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3 |
|
1 |
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| 4
creates a quintet |
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|
1 |
|
4 |
|
6 |
|
4 |
|
1 |
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|
| 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. |
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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. |
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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). |
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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. |
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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. |
Key words & phrases:
C2H6
CH3CH3 Interpreting the proton H-1 NMR spectra of ethane, low resolution & high resolution proton
nmr spectra of ethane, H-1 nmr spectrum of ethane, understanding the
hydrogen-1 nmr spectrum of ethane, explaining the line splitting patterns from
spin-spin coupling in the
high resolution H-1 nmr spectra of ethane, revising the H-1 nmr spectrum of
ethane,
proton nmr of ethane, ppm chemical shifts of the H-1 nmr spectrum of ethane,
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 ethane, how to work out the
number of chemically different protons in the structure of the ethane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of ethane using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of ethane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of ethane
examining the 1H nmr spectrum of ethane analysing the 1-H nmr spectrum of
ethane
how do you sketch and interpret the H-1 NMR spectrum of ethane interpreting
interpretation of the 1H proton spin-spin coupling causing line splitting in the
NMR spectrum of ethane
assignment of chemical shifts in the
proton 1H NMR spectrum of ethane formula explaining spin-spin coupling for line
splitting for ethane alkane
functional group
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)
ALL SPECTROSCOPY INDEXES
All Advanced Organic
Chemistry Notes
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