|
Interpreting the
1H NMR spectrum of 3-methylhexane
[Author
©
Dr WP Brown PhD:
Doc Brown's advanced level organic chemistry exam revision notes
suitable for students of UK A level chemistry courses & US K12 grade
11, grade 12 and AP honors chemistry courses: Molecular
spectroscopy - analysing the
1H NMR spectrum of
3-methylhexane
[updated
October 26th 2025]
Links associated
with
3-methylhexane
email doc
brown
Re-edit
1H NMR spectrum
CH3CH2CH(CH3)CH2CH2CH3
The chemistry of ALKANES and the petrochemical
industry
This is a BIG
website, PLEASE take time to explore it
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
Introductory note on the 1H NMR spectra of 3-methylhexane
Students and teachers please note my explanation of the
proton NMR spectrum of 3-methylhexane is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
3-methylhexane are
confined to a proton spin-spin
coupling effects analysed using the n+1 rule for adjacent
non-equivalent proton fields (n is the number of neighbouring
protons in a non-equivalent different chemical environment for the
3-methylhexane molecule).
It is assumed that the integrated intensities of the
1H
NMR δ
chemical shifts give the ratio of the protons in the different
non-equivalent chemical environments of the 3-methylhexane molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like 3-methylhexane, is CDCl3 and other
deuterated solvents to avoid confusion with a 1H NMR
signal, 2D (2H) has a different NMR chemical
shift.
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.
In terms of spin-spin coupling from the possible proton magnetic orientations,
for 3-methylhexane I
have only considered the interactions of
non-equivalent protons on adjacent carbon atoms
e.g. -CH2-CH3
or >CH-CH3
or R-CH2-CH2-X
protons etc.
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
The molecular structure and
naming of alkanes
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.
The protons occupy
similar 'alkyl' environments, so show similar H-1 NMR chemical
shifts.
There is also a further complications with
resonances
(b) and (d).
CH3CH2C*H(CH3)CH2CH2CH3
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, meaning that technically, there are 9
different chemical environments for the protons in the
3-methylhexane molecule - but this now university level
analysis.
Key points about the 1H NMR spectrum of 3-methylspectrum
The ¹H NMR spectrum of 3-methylhexane shows multiple alkyl proton
environments with chemical shifts between 0.8–1.6 ppm, reflecting
methyl and methylene groups in distinct branching contexts.
Integration and splitting patterns help distinguish these
environments, but complex here.
Theoretical
¹H NMR Spectrum of 3-Methylhexane
3-Methylhexane (C7H16)
contains 16 protons distributed across 7
distinct chemical environments, due to its asymmetric
branching.
All signals appear in the
upfield region (δ ≈ 0.8–1.6 ppm), but subtle differences in
shielding and coupling make the spectrum complex.
| Chemical Shift
(δ, ppm) |
Proton Type |
Environment |
Integration |
Splitting
Pattern |
| ~0.85 |
CH3 |
Terminal methyl (C–CH3) |
3H |
Triplet |
| ~0.88 |
CH3 |
Methyl on branch
(CH(CH₃)–) |
3H |
Doublet |
| ~0.95 |
CH3 |
Other terminal methyl |
3H |
Triplet |
| ~1.20 |
CH2 |
Linear chain methylene |
2H |
Multiplet |
| ~1.30 |
CH2 |
Methylene adjacent to
branch |
2H |
Multiplet |
| ~1.40 |
CH2 |
Methylene near central
carbon |
2H |
Multiplet |
| ~1.55 |
CH |
Methine (central C–H in
branch) |
1H |
Multiplet (complex
coupling) |
Note: Chemical shifts may vary
slightly depending on solvent and field strength. Overlapping multiplets
are common.
https://sdbs.db.aist.go.jp/
diagram δ ppm spectral database of organic
compounds
Why So
Complex?
- No symmetry:
The methyl and methylene groups are in subtly different environments
due to branching.
- Spin-spin coupling:
Each proton couples with adjacent protons, creating overlapping
multiplets.
- Close chemical shifts:
All signals fall within a narrow window, making resolution
difficult.
Common
Misconceptions
- Assuming fewer signals:
Students often expect 3–4 peaks, missing subtle non-equivalence.
- Misidentifying overlapping
multiplets: Multiplets
may appear as broad humps or unresolved clusters.
- Ignoring integration:
Integration confirms the number of protons per signal — critical for
peak assignment.
- Expecting downfield peaks:
Without electronegative atoms or π systems, all signals are upfield.
Exam Tips
for ¹H NMR Interpretation
- Use integration first:
Match proton counts to signal areas before assigning chemical
shifts.
- Sketch the molecule:
Label each proton environment to predict the number of signals.
- Practice with isomers:
Compare 3-methylhexane vs. 2-methylhexane or n-heptane to see how
branching affects spectra.
- Annotate spectra:
Label δ, integration, and splitting — this helps structure answers
in exams.
- Expect complexity:
Even simple alkanes can produce crowded spectra due to subtle
non-equivalence.
The splitting pattern from proton
spin-spin coupling effects is analysed using the n+1 rule for
adjacent non-equivalent proton fields (n is the number of
neighbouring protons in a non-equivalent different chemical
environment).
|
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
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. |
|
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 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
spin
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
How do you interpret the H-1 NMR spectrum of
3-methylhexane How to interpret
the H-1 NMR spectrum of 3-methylhexane Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the 3-methylhexane
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of 3-methylhexane. How to explain the H-1 NMR spectrum of
3-methylhexane. The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the 3-methylhexane molecule. How to work out the molecular
structure of the 3-methylhexane molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the
3-methylhexane
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the 3-methylhexane
molecule? explaining the spin-spin proton coupling effects in the 1H
NMR spectrum of 3-methylhexane. interpretation
diagram explaining the proton splitting
pattern produced from the n+1 rule and the theoretical ratio of chemical shift
and values of intensities for the proton NMR spectrum lines of 3-methylhexane
Links associated
with
3-methylhexane
The
infrared spectrum of 3-methylhexane
The mass
spectrum of 3-methylhexane
The
C-13 NMR spectrum of 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
Use My Google search site box
Email doc b:
chem55555@hotmail.com
|
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
|
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
|
|
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
|
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
|
Website content © Dr
Phil Brown 2000+. All copyrights reserved on revision notes, images,
quizzes, worksheets etc. Copying of Doc Brown's pre-university
advanced level chemistry website material is NOT
permitted. Exam revision summaries & references to science course specifications
are unofficial. These organic chemistry revision notes on
spectroscopy are
suitable for use of pre-university students studying AQA advanced level
chemistry, Edexcel advanced level chemistry, OCR advanced level
chemistry, IB advanced level chemistry, WJEC (Eduqas) advanced level
chemistry, CIE advanced level chemistry, US grade 11-12 AP honors
chemistry courses and they will also prove useful to
1st year undergraduate students of chemistry.
|
