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The H-1
hydrogen-1 (proton) NMR spectrum of heptane
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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 heptane
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H-1 proton NMR spectroscopy -
spectra index
See also
comparing the
1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16
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 shifts, called chemical shifts, depend on the
individual (electronic) chemical environment of the hydrogen atoms
in an organic molecule - heptane here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of heptane 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 heptane molecule.
Heptane,
C7H16 , CH3(CH2)5CH3
,
,
For more
see The molecular structure,
classification and
naming of alkanes
Interpreting the
H-1 NMR spectrum of
heptane
For relatively simple molecules, the low
resolution H-1 NMR spectrum of heptane is a limited, but not
useless, starting point.
The hydrogen atoms (protons) of heptane occupy 4
different chemical environments so that the very high resolution NMR
spectra should show 4 peaks of different H-1 NMR chemical shifts (diagram above for
heptane), BUT three of the chemical shifts are very close
together, so even at moderate resolution (diagram above) you see
two main peaks in the proton ration 3:5 for CH3:CH2
protons..
CH3CH2CH2CH2CH2CH2CH3
Note the proton ratio 6:4:4:2 (3:2:2:1) of the
four colours of the protons
in the four chemically different environments, but, even a
moderate resolution spectrum (diagram above) shows two main
peaks in the ratio of 3:5 for the CH3:CH2
protons.
Chemical shifts (a) to (d) on the H-1 NMR
spectrum diagram for heptane.
Although there are 16 hydrogen atoms in the molecule,
there are, theoretically, only 4 possible different chemical
environments for the hydrogen atoms in heptane molecule.
The high resolution 1H NMR
spectrum of heptane
All low and high resolution spectra of heptane
show 4 groups of proton resonances and in the 3:2:2:1 ratio expected from the
formula of heptane.
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of heptane - since the peak' is at the apex of a band of
H-1 NMR resonances due to spin - spin coupling field splitting effects - see high resolution
notes on heptane below.
So, using the chemical shifts and applying the
n+1 rule to
heptane
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
(a) 1H
Chemical shift 0.88 ppm, CH3 proton resonance, CH3CH2CH2CH2CH2CH2CH3
The CH3 proton resonance is
split into a 1:2:1 triplet by the neighbouring CH2
protons.
Evidence for the presence of a CH2
group in the molecule of heptane
(b) to (d) are very similar and would need very high resolution to
resolve the complex splitting patterns involved.
Resonances (a):(b)+(c)+(d) give the
ratio 3:5 for the CH3:CH2 proton
ratio
(b) 1H
Chemical shift 1.30 ppm, CH2 proton resonance, CH3CH2CH2CH2CH2CH2CH3
Theoretically this resonance is split
into a sextet (n+1 = 6) by the neighbouring CH3
and CH2 protons.
(c) 1H
Chemical shift 1.27 ppm, CH2 proton resonance, CH3CH2CH2CH2CH2CH2CH3
Theoretically this resonance is split
into a quintet (n+1 = 5) by the neighbouring CH2
and CH2 protons.
(d) 1H
Chemical shift 1.27 ppm, CH2 proton resonance, CH3CH2CH2CH2CH2CH2CH3
Theoretically this resonance is split
into a quintet (n+1 = 5) by the neighbouring CH2
and CH2 protons.
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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 |
|
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 |
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Comparing the
1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16
You can distinguish all 9 isomers from a data combination of their number of
1H NMR
chemical shifts,
and their resulting integrated 1H proton ratios, plus, their number of
13C
chemical shifts. |
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Name of the alkane structural isomer of molecular
formula C7H16 |
Abbreviated structural formulae
of the nine isomers of molecular formula C7H16 (interpretation complications with 3-methylhexane and
2,3-dimethylpentane because they exhibit R/S isomerism due to a
chiral carbon) |
Skeletal formula of the
nine
alkane isomers of
molecular formula C7H16 |
Number of 1H NMR chemical shifts (δ) and
proton ratio (links
to spectrum) |
Number of 13C chemical shifts (δ)
(links
to spectrum) |
| heptane |
|
|
4 δ: proton ratio: 3:2:2:1 (6:4:4:2 in the molecule) |
4 δ shifts |
| 2-methylhexane |
 |
 |
6 δ: proton ratio :
6:3:2:2:2:1 |
6 δ shifts |
| 3-methylhexane |
 |
 |
7 δ: proton ratio:
3:3:3:2:2:2:1 (simplification) !!! |
7
δ shifts |
| 3-ethylpentane |
 |
 |
3 δ: proton ratio:
9:6:1 |
3 δ
shifts |
| 2,2-dimethylpentane |
 |
 |
4 δ: proton ratio:
9:3:2:2 |
5 δ shifts |
|
2,3-dimethylpentane |
 |
 |
6 δ: proton ratio:
6:3:3:2:1:1 (simplification) !!! |
6 δ
shifts (simplification) !!! |
|
2,4-dimethylpentane |
 |
 |
3 δ: proton ratio:
12:2:2 |
3 δ
shifts |
| 3,3-dimethylpentane |
 |
 |
3 δ: proton ratio:
3:3:2 (6:4:4 in the molecule) |
4 δ
shifts |
| 2,2,3-trimethylbutane |
 |
 |
3 δ: proton ratio:
9:6:1 |
4 δ shifts |
Key words & phrases:
C7H16
Interpreting the proton H-1 NMR spectra of heptane, low resolution & high resolution proton
nmr spectra of heptane, H-1 nmr spectrum of heptane, understanding the
hydrogen-1 nmr spectrum of heptane, explaining the line splitting patterns in the
high resolution H-1 nmr spectra of heptane, revising the H-1 nmr spectrum of
heptane,
proton nmr of heptane, ppm chemical shifts of the H-1 nmr spectrum of heptane,
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 heptane, how to work out the
number of chemically different protons in the structure of the heptane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of heptane using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of heptane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of heptane
examining the 1H nmr spectrum of heptane analysing the 1-H nmr spectrum of
heptane how do you sketch and interpret the H-1 NMR spectrum of heptane
interpreting interpretation of the 1H proton NMR spectrum of heptane
Molecular structure diagram of the
proton NMR diagram for the 1H NMR spectrum of heptane. The proton ratio in the
1H NMR spectrum of heptane. Deducing the number of different chemical
environments of the protons in the heptane molecule from the 1H chemical shifts
in the hydrogen-1 NMR spectrum of heptane. Analysing the high resolution 1H NMR
spectrum of heptane. Analysing the low resolution 1H NMR spectrum of heptane. You
may need to know the relative molecular mass of heptane to deduce the molecular
formula from the proton ratio of the 1H NMR spectrum of heptane. Revision notes
on the proton NMR spectrum of heptane. Matching and deducing the structure of
the heptane molecule from its hydrogen-1 NMR spectrum.
Proton NMR spectroscopy of aliphatic alkanes,
1H NMR spectra of heptane, a structural isomer of molecular formula
C7H16
Links associated
with heptane
The chemistry of ALKANES
revision notes INDEX
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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Infrared spectra of the isomers of C7H16
The infrared
spectrum of heptane
The
infrared spectrum of 2-methylhexane
The
infrared spectrum of 3-methylhexane
The
infrared spectrum of 3-ethylpentane
The infrared spectrum of
2,2-dimethylpentane
The infrared spectrum of
2,3-dimethylpentane
The infrared spectrum of
2,4-dimethylpentane
The infrared spectrum of
3,3-dimethylpentane
The infrared spectrum
of 2,2,3-trimethylbutane
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Mass spectra of the isomers of C7H16
The mass
spectrum of heptane
The mass
spectrum of 2-methylhexane
The mass
spectrum of 3-methylhexane
The
mass spectrum of 3-ethylpentane
The mass spectrum of
2,2-dimethylpentane
The mass spectrum of
2,3-dimethylpentane
The mass spectrum of
2,4-dimethylpentane
The mass spectrum of
3,3-dimethylpentane
The mass
spectrum of 2,2,3-trimethylbutane
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H-1 proton NMR spectra of ALKANES
1H NMR spectra of the isomers of C7H16
The H-1 NMR
spectrum of heptane
The
H-1 NMR spectrum of 2-methylhexane
The
H-1 NMR spectrum of 3-methylhexane
The
H-1 NMR spectrum of 3-ethylpentane
The H-1 NMR spectrum of
2,2-dimethylpentane
The H-1 NMR spectrum of
2,3-dimethylpentane
The H-1 NMR spectrum of
2,4-dimethylpentane
The H-1 NMR spectrum of
3,3-dimethylpentane
The H-1
NMR spectrum of 2,2,3-trimethylbutane
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C-13 carbon-13 NMR spectra
of ALKANES
13C NMR spectra of the isomers of C7H16
The C-13 NMR
spectrum of heptane
The
C-13 NMR spectrum of 2-methylhexane
The
C-13 NMR spectrum of 3-methylhexane
The
C-13 NMR spectrum of 3-ethylpentane
The C-13 NMR spectrum of
2,2-dimethylpentane
The C-13 NMR spectrum of
2,3-dimethylpentane
The C-13 NMR spectrum of
2,4-dimethylpentane
The C-13 NMR spectrum of
3,3-dimethylpentane
The
C-13 NMR spectrum of 2,2,3-trimethylbutane
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