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Interpreting
and explaining the
H-1 proton NMR spectrum: 2-methylpropene
(2-methylprop-1-ene)
[Author
©
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 spectra of
methylpropene, 2-methylpropene
[spectra
page updated
April 4th 2026 *]
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brown
Re-edit the 1H NMR spectrum of H2C=C(CH3)2
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H-1 proton NMR spectroscopy -
spectra index
Introductory note on the 1H NMR spectra of 2-methylpropene
Students and teachers please note my explanation of the
proton NMR spectrum of 2-methylpropene is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
2-methylpropene 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-methylpropene molecule).
It is assumed that the integrated intensities of the
δ
chemical shifts give the ratio of the protons in the different
non-equivalent chemical environments of the 2-methylpropene molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like 2-methylpropene, is CDCl3 and other
deuterated solvents to avoid confusion with a 1H NMR
signal, 2D (2H) has a different 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 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 - 2-methylpropene here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 2-methylpropene 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-methylpropene molecule.
2-methylpropene,
 ,
 ,
,
The molecular structure and naming of alkenes
Interpreting the
H-1 NMR spectrum of
2-methylpropene
In terms of spin-spin coupling from the possible proton magnetic orientations,
for 2-methylpropene I
have only considered the interactions of
non-equivalent protons on adjacent carbon atoms
e.g. -CH2-CH3,
R-CH2-CH2-X
protons etc, BUT this does not apply to the molecular structure of
2-methylpropene.
For relatively simple molecules, the low
resolution H-1 NMR spectrum of 2-methylpropene is a good starting point
(low resolution diagram above).
The 8 hydrogen atoms (protons) of
2-methylpropene occupy 2
different chemical environments so that the low resolution NMR
spectra should show 2 principal
1H resonance peaks of different H-1 NMR chemical shifts (diagram above for
2-methylpropene).
(CH3)2C=CH2
Note the proton ratio 6:2 of the 2 colours of the
8 protons of 2-methylpropene
in the 2 chemically different proton environments
Chemical shifts
(a) to (b) on the H-1 NMR
spectrum diagram for 2-methylpropene.
Although there are 8 hydrogen atoms in the molecule, the
proton NMR spectrum shows there are only 2 possible different chemical
environments for the hydrogen atoms due to the symmetry of the 2-methylpropene molecule.
The integrated proton signal ratio of 3:1 observed
in the high resolution H-1 NMR spectrum, corresponds with
the structural formula of 2-methylpropene.
The high resolution 1H NMR spectrum of 2-methylpropene
The high resolution spectra of 2-methylpropene
shows 2 groups of proton resonances and in the 3:1 ratio expected from the
structural
formula of 2-methylpropene, but we can now consider the splitting of
resonance lines from the spin-spin coupling in the molecule of
2-methylpropene.
However, there are no adjacent protons on two adjacent carbon
atom, so applying the n+1 rule
to 2-methylpropene
isn't necessary! (but important in working the other
way round to deduce the structure of 2-methylpropene or other
molecule - everything is a clue!)
1H NMR resonance
(a) 1H Chemical shift δ 1.75 ppm:
(CH3)2C=CH2
The methyl group protons are detected as
a single singlet resonance.
All these 6 protons are equivalent to
each other, and equivalent protons do not split each
other's resonances.
Evidence for the presence of a CHx grouping,
that is not next to another CHx grouping,
in the molecule of 2-methylpropene (x = 1 to 3).
1H NMR resonance
(b) 1H
Chemical shift δ 4.70 ppm:
(CH3)2C=CH2
The =CH2 protons are detected
as a single singlet resonance.
Both protons are equivalent to each
other, and equivalent protons do not split each other's
resonances.
Evidence for the presence of a second CHx grouping
(different 1H chemical shift), that is not next to
another CHx grouping,
in the molecule of 2-methylpropene (x = 1 to 3).
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-methylpropene.
|
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 |
Key words & phrases:
isomer
of molecular C4H8
(CH3)2C=CH2 formula
Interpreting the proton H-1 NMR spectra of 2-methylpropene, low resolution & high
resolution proton nmr spectra of 2-methylpropene, H-1 nmr spectrum of
2-methylpropene, understanding the
hydrogen-1 nmr spectrum of 2-methylpropene, explaining the line splitting patterns from
spin-spin coupling in the high resolution H-1 nmr spectra of
2-methylpropene, revising
the H-1 nmr spectrum of 2-methylpropene, proton nmr of 2-methylpropene, ppm chemical shifts of the H-1
nmr spectrum of 2-methylpropene, explaining and analyzing spin spin line splitting in the
H-1 nmr spectrum, how to construct the diagram of the 1H nmr spectrum of
2-methylpropene, how to work out the
number of chemically different protons in the structure of the 2-methylpropene organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 2-methylpropene using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of 2-methylpropene deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 2-methylpropene
examining the 1H nmr spectrum of 2-methylpropene analysing the 1H nmr spectrum of
2-methylpropene
how do you sketch and interpret the H-1 NMR spectrum of 2-methylpropene
interpreting interpretation of the 1H proton spin-spin coupling causing line
splitting in the NMR spectrum of 2-methylpropene
assignment of chemical shifts in the
proton 1H NMR spectrum of 2-methylpropene formula explaining spin-spin coupling
for line splitting for
alkene functional group
2-methylpropene 2-Methylprop-1-ene methylpropene isobutene isobutylene
2-methylpropylene How do you interpret the H-1 NMR spectrum of
2-methylpropene How to interpret
the H-1 NMR spectrum of 2-methylpropene Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the 2-methylpropene
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of 2-methylpropene. How to explain the H-1 NMR spectrum of
2-methylpropene. The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the 2-methylpropene molecule. How to work out the molecular
structure of the 2-methylpropene molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the
2-methylpropene
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the 2-methylpropene
molecule? explaining the spin-spin proton coupling effects in the 1H
NMR spectrum of 2-methylpropene. interpretation
diagram explaining the proton splitting pattern produced from the
n+1 rule and the theoretical ratio of chemical shift
δ and values of
intensities for the proton NMR spectrum lines of 2-methylpropene
Links associated
with
2-methylpropene
The chemistry of ALKENES
revision notes INDEX
The
infrared spectrum of 2-methylpropene
(2-methylprop-1-ene)
The mass
spectrum of 2-methylpropene (2-methylprop-1-ene)
The
C-13 NMR spectrum of 2-methylpropene
(2-methylprop-1-ene)
H-1 proton NMR spectroscopy index
(Please
read 8 points at the top of the 1H NMR index page)
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