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Interpreting the
1H NMR spectrum of 2-methylbut-1-ene
[Author
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Dr
Phil 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
2-methylbut-1-ene
[spectra
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1H NMR spectrum of
CH3CH2C(CH3)=CH2
Links associated
with 2-methylbut-1-ene
The
chemistry of alkenes
This is a BIG
chemistry website, please take time to explore it
H-1 proton NMR spectroscopy -
spectra index
Introductory note on the 1H NMR spectra of 2-methylbut-1-ene
(2-methyl-1-butene)
Students and teachers please note my explanation of the
proton NMR spectrum of 2-methylbut-1-ene is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
2-methylbut-1-ene 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
2-methylbut-1-ene 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 2-methylbut-1-ene molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like 2-methylbut-1-ene, 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 - 2-methylbut-1-ene here.
In terms of spin-spin coupling from the possible proton magnetic orientations,
for 2-methylbut-1-ene I
have only considered the interactions of
non-equivalent protons on adjacent carbon atoms
e.g. -CH2-CH3
protons etc.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 2-methylbut-1-ene 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 2-methylbut-1-ene molecule.
2-methylbut-1-ene C5H10,
 ,
The molecular structure and naming of alkenes
Interpreting the
H-1 NMR spectrum of
2-methylbut-1-ene
For relatively simple molecules, the low
resolution H-1 NMR spectrum of 2-methylbut-1-ene is a good starting point
(low resolution diagram above).
The hydrogen atoms (protons) of
2-methylbut-1-ene occupy 4
different chemical environments so that the low resolution NMR
spectra should show 4 peaks of different H-1 NMR chemical shifts (diagram above for
2-methylbut-1-ene).
H2C=C(CH3)CH2CH3
Note the proton ratio
of 2:3:2:3 of the four colours of the protons
in the four chemically different environments
Although there are 10 hydrogen atoms in the molecule,
there only 4 possible different chemical
environments for the hydrogen atoms in 2-methylbut-1-ene molecule.
The integrated signal proton ratio ? observed, corresponds with
the structural formula of 2-methylbut-1-ene.
The high resolution H-1 NMR
spectrum of 2-methylbut-1-ene
All low and high resolution spectra of
2-methylbut-1-ene
show ? groups of proton resonances and in the ratio expected from the
formula of 2-methylbut-1-ene.
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of 2-methylbut-1-ene - 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 2-methylbut-1-ene below.
So, using the chemical shifts and applying the
n+1 rule to
2-methylbut-1-ene
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
(a) 1H
Chemical shift 4.67 ppm CH2 protons
H2C=C(CH3)CH2CH3
The 'blue' CH2 proton
resonance is not affected by any directly adjacent
protons, so a singlet is observed.
(b) 1H
Chemical shift 1.73 ppm CH3 protons
H2C=C(CH3)CH2CH3
The 'purple' CH3 proton
resonance is not affected by any directly adjacent
protons,
so a singlet is observed.
(c) 1H
Chemical shift 2.02 ppm CH2 protons
H2C=C(CH3)CH2CH3
The 'green' CH2 proton
resonance is split into a 1:3:3:1 quartet by the 'brown'
CH3 protons (n+1 = 4).
Evidence for the presence of a CH3 group
in the molecule of 2-methylbut-1-ene
(d) 1H
Chemical shift 1.03 ppm CH3 protons
H2C=C(CH3)CH2CH3
The 'brown' CH3 proton
resonance is split into a 1:2:1 triplet by the 'green'
CH2 protons (n+1 = 3).
Evidence for the presence of a CH2 group
in the molecule of 2-methylbut-1-ene
Summary of key points for the 1H NMR spectrum of 2-methylbut-1-ene plus
extra exam revision comments
A structured breakdown of the ¹H NMR spectrum of
2-methylbut-1-ene, tailored for advanced A-level and IB
Chemistry exam boards. This includes chemical shifts, proton
environments, integration ratios, misconceptions, and revision tips.
Molecular
Overview
- Structure: CH2=C(CH3)CH2CH3
- Molecular formula: C5H10
- Key features: Terminal alkene, methyl branch,
ethyl chain
Proton
Environments & Chemical Shifts for
the 1H NMR spectrum of 2-methylbut-1-ene
|
Label |
Proton Type |
Environment |
δ (ppm) |
Splitting |
Integration |
Notes |
|
a |
=CH2
(vinylic) |
Terminal alkene |
~4.6–4.7, 4.67 ppm |
Singlet |
2 |
Deshielded by C=C |
|
c |
–CH2– |
Next
to alkene |
~2.0, 2.02 ppm |
Multiplet |
2 |
Allylic position |
|
b |
–CH3
(methyl branch) |
Attached to C=C |
~1.7, 1.73 ppm |
Singlet |
3 |
Allylic methyl |
|
d |
–CH3
(ethyl terminal) |
Ethyl group |
~0.9, 1.03 ppm |
Triplet |
3 |
Coupled with adjacent CH₂ |
H2C=C(CH3)CH2CH3
These values are approximate and may vary slightly depending on
solvent and conditions (typically CDCl3).
Common
Misconceptions about
the 1H NMR spectrum of 2-methylbut-1-ene
- Mistaking vinylic protons for aromatic: Vinylic
protons (~4.6 ppm) are often confused with aromatic (~7 ppm).
- Overlooking methyl singlets: Students may
assume all methyl groups split — but isolated methyls (like C) often
appear as singlets.
- Misinterpreting integration: Integration
reflects relative number of protons, not peak
height.
- Ignoring coupling patterns: Ethyl groups show
characteristic quartet-triplet patterns (D and E).
Exam
Revision Tips for questions involving
the 1H NMR spectrum of 2-methylbut-1-ene
(AQA, Edexcel, OCR, WJEC, CCEA, CIE, IB)
Peak Identification Strategy
- Start with integration: Match peak areas to
proton counts (e.g. 3H = CH₃).
- Use chemical shift ranges: Know typical δ
values for alkene, alkyl, allylic, and vinylic protons.
- Check splitting patterns: Apply n+1
rule to deduce adjacent protons.
Common Question Types
- “How many proton environments are present?”
- “Explain the splitting pattern of peak X.”
- “Suggest a structure consistent with this spectrum.”
- “Compare spectra of isomers (e.g. 2-methylbut-1-ene versus
2-methylbut-2-ene).”
Integration & Ratios
- Practice reading integration traces or ratios
(e.g. 2:2:3:2:3).
- Use ratios to confirm molecular formula or
identify symmetry.
Cross-Technique Integration
- Combine with IR (C=C stretch ~1650 cm⁻¹) and
mass spec (m/z 70 M⁺) for full analysis.
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) and applied to the 1H NMR spectrum of
2-methylbut-1-ene.
|
Number of protons 1H
causing splitting |
Splitting pattern produced from the
n+1 rule 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 |
Key words & phrases: 2-methyl-1-butene
Interpreting the proton H-1 NMR spectra of 2-methylbut-1-ene, low resolution & high resolution proton
nmr spectra of 2-methylbut-1-ene, H-1 nmr spectrum of 2-methylbut-1-ene, understanding the
hydrogen-1 nmr spectrum of 2-methylbut-1-ene, explaining the line splitting patterns in the
high resolution H-1 nmr spectra of 2-methylbut-1-ene, revising the H-1 nmr spectrum of
2-methylbut-1-ene,
proton nmr of 2-methylbut-1-ene, ppm chemical shifts of the H-1 nmr spectrum of
2-methylbut-1-ene,
explaining and analyzing spin line splitting in the H-1 nmr spectrum, how
to construct the diagram of the H-1 nmr spectrum of 2-methylbut-1-ene, how to work out the
number of chemically different protons in the structure of the 2-methylbut-1-ene organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 2-methylbut-1-ene using the n+1 rule to explain the spin - spin coupling splitting in the proton nmr spectrum of 2-methylbut-1-ene deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 2-methylbut-1-ene
examining the 1H nmr spectrum of 2-methylbut-1-ene analysing the 1-H nmr spectrum of
2-methylbut-1-ene how do you sketch and interpret the H-1 NMR spectrum of
2-methylbut-1-ene
interpreting interpretation of the H-1 proton NMR spectrum of 2-methylbut-1-ene
2-methyl-1-butene How do you interpret the H-1 NMR spectrum of
2-methylbut-1-ene (2-methyl-1-butene) How to interpret
the H-1 NMR spectrum of 2-methylbut-1-ene (2-methyl-1-butene) Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the 2-methylbut-1-ene
(2-methyl-1-butene)
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of 2-methylbut-1-ene (2-methyl-1-butene). How to explain the H-1 NMR spectrum of
2-methylbut-1-ene (2-methyl-1-butene). The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the 2-methylbut-1-ene (2-methyl-1-butene) molecule. How to work out the molecular
structure of the 2-methylbut-1-ene (2-methyl-1-butene) molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the
2-methylbut-1-ene (2-methyl-1-butene)
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the 2-methylbut-1-ene
(2-methyl-1-butene)
molecule? explaining the spin-spin proton coupling effects in the 1H
NMR spectrum of 2-methylbut-1-ene (2-methyl-1-butene). 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 2-methylbut-1-ene
(2-methyl-1-butene)
Links associated
with
2-methylbut-1-ene
The Infrared spectrum of
2-methylbut-1ene
The mass spectrum of 2-methylbut-1ene
The C-13 NMR spectrum of
2-methylbut-1ene
The chemistry of ALKENES
revision notes INDEX
H-1 proton NMR spectroscopy index
(Please
read 8 points at the top of the 1H NMR index page)
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