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The H-1
hydrogen-1 (proton) NMR spectrum of 3-methylhexane
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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 3-methylhexane
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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 - 3-methylhexane here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 3-methylhexane 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 3-methylhexane molecule.
3-methylhexane
C7H16
Interpreting the
H-1 NMR spectrum of
3-methylhexane
For relatively simple molecules, the low
resolution H-1 NMR spectrum of 3-methylhexane is NOT a good starting point
(relatively low resolution diagram above).
The hydrogen atoms (protons) of 3-methylhexane occupy
7
different chemical environments so that the low resolution NMR
spectra should show 7 principal peaks of different H-1 NMR chemical shifts (diagram above for
3-methylhexane).
CH3CH2CH(CH3)CH2CH2CH3
Note the proton ratio 3:2:1:3:2:2:3 of the
7 colours of the protons
in the 7 chemically different environments (but see last comment
in the notes below!).
Chemical shifts (a) to (g) on the H-1 NMR
spectrum diagram for 3-methylhexane.
Theoretically, although there are 16 hydrogen atoms in the molecule,
there are 7 possible different chemical environments for the
hydrogen atoms in 3-methylhexane molecule (but see last comment in the
notes below!).
The high resolution 1H NMR
spectrum of 3-methylhexane
A very high resolution spectrum of
3-methylhexane
will show 7 different resonances, though many of the chemical
shifts are close together.
I've quoted the chemical shift data, but
made no attempt to show the resonance splitting in terms of
major peaks and subsequent spin-spin coupling splitting
effects.
The full interpretation of the 1H NMR spectrum
of 3-methylhexane is beyond the scope of my pre-university
chemistry website.
There is also a further complications with
resonances (b) and (d).
Due to the asymmetry of the molecule, which
has a chiral carbon atom (*), the CH2
protons on either side of the chiral carbon are NOT equivalent
- two more chemical environments.
This means that technically, there are 9
different chemical environments for the 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 |
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2 |
|
1 |
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| 3
creates a quartet |
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1 |
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3 |
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3 |
|
1 |
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| 4
creates a quintet |
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|
1 |
|
4 |
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6 |
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4 |
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1 |
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| 5
creates a sextet |
|
1 |
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5 |
|
10 |
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10 |
|
5 |
|
1 |
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| 6
creates a septet |
1 |
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6 |
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15 |
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20 |
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15 |
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6 |
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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 |
|
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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 |
 |
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3 δ: proton ratio:
9:6:1 |
4 δ shifts |
Key words & phrases:
C7H16
Interpreting the proton H-1 NMR spectra of 3-methylhexane, low resolution & high resolution proton
nmr spectra of 3-methylhexane, H-1 nmr spectrum of 3-methylhexane, understanding the
hydrogen-1 nmr spectrum of 3-methylhexane, explaining the line splitting patterns in the
high resolution H-1 nmr spectra of 3-methylhexane, revising the H-1 nmr spectrum of
3-methylhexane,
proton nmr of 3-methylhexane, ppm chemical shifts of the H-1 nmr spectrum of
3-methylhexane,
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 3-methylhexane, how to work out the
number of chemically different protons in the structure of the 3-methylhexane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 3-methylhexane using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of 3-methylhexane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 3-methylhexane
examining the 1H nmr spectrum of 3-methylhexane analysing the 1-H nmr spectrum of
3-methylhexane how do you sketch and interpret the H-1 NMR spectrum of
3-methylhexane
interpreting interpretation of the 1H proton NMR spectrum of 3-methylhexane
CH3CH2CH(CH3)CH2CH2CH3
Molecular structure diagram of the
proton NMR diagram for the 1H NMR spectrum of 3-methylhexane. The proton ratio in the
1H NMR spectrum of 3-methylhexane. Deducing the number of different chemical
environments of the protons in the 3-methylhexane molecule from the 1H chemical shifts
in the hydrogen-1 NMR spectrum of 3-methylhexane. Analysing the high resolution 1H NMR
spectrum of 3-methylhexane. Analysing the low resolution 1H NMR spectrum of
3-methylhexane. You
may need to know the relative molecular mass of 3-methylhexane to deduce the molecular
formula from the proton ratio of the 1H NMR spectrum of 3-methylhexane. Revision notes
on the proton NMR spectrum of 3-methylhexane. Matching and deducing the structure of
the 3-methylhexane molecule from its hydrogen-1 NMR spectrum.
Proton NMR spectroscopy of aliphatic alkanes,
1H NMR spectra of 3-methylhexane, a structural isomer of molecular formula
C7H16
Links associated
with 3-methylhexane
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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Email doc b:
chem55555@hotmail.com
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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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