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Interpreting
and explaining the
H-1 hydrogen-1 (proton) NMR spectrum of but-1-ene (1-butene)
[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
spectrometry - analysing the 1H NMR spectra of
butan-1ene
[spectra page updated
April 3rd 2026 *]
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1H NMR spectrum of CH3CH2CH=CH2
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H-1 proton NMR spectroscopy -
spectra index
Introductory note on the 1H NMR spectra of but-1-ene
Students and teachers please note my explanation of the
proton NMR spectrum of but-1-ene is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
but-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
but-1-ene 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 but-1-ene molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like but-1-ene, 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 - but-1-ene here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of but-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 but-1-ene molecule.
But-1-ene,
 ,
,
The molecular structure and naming of alkenes
Interpreting the
H-1 NMR spectrum of
but-1-ene
In terms of spin-spin coupling from the possible proton magnetic orientations,
for but-1-ene I
have only considered the interactions of
non-equivalent protons on adjacent carbon atoms
e.g. -CH2-CH3, -CH-CH2-, protons
etc.
For relatively simple molecules, the low
resolution H-1 NMR spectrum of but-1-ene is a good starting point
(low resolution diagram above).
The 8 hydrogen atoms (protons) of but-1-ene seem
to occupy 4
different chemical environments in terms of the low resolution NMR
spectra, but the very spectrum shows the H2C= protons are
slightly different in terms of their H-1 NMR chemical shifts -
chemical environments (diagram above for
but-1-ene).
H2C=CH-CH2-CH3
Note the
proton ratio 2:1:2:3 of the 4 colours of the
8 protons of but-1-ene
in the 4 chemically different proton environments - for
the moment ignoring the small difference in the two H2C=
proton environments of but-1-ene. So you would expect
4 different chemical
shift lines.
Chemical shifts (a) to (e) on the H-1 NMR
spectrum diagram for but-1-ene.
The integrated signal proton ratio
2:1:2:3
observed in the low resolution H-1 NMR spectrum, corresponds with
the structural formula of but-1-ene, but at very high resolution
the ratio becomes 1:1:1:2:3 (university level analysis).
At pre-university level the low
resolution ratio will probably suffice.
BUT, the
H2C=
proton environments
are slightly different because of
two different groups attached to the other C of the C=C bond -
asymmetric field.
The high resolution 1H NMR
spectrum of but-1-ene
The high resolution spectra of but-1-ene
shows 4 groups of proton resonances and in the 2:1:2:3 ratio expected from the
structural
formula of but-1-ene, but technically the end H2C= protons
experence slightly different field effects because the asymmetry
of the =CH-CH2 groupings.
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of but-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 but-1-ene below.
So, using the chemical shifts and applying the
n+1 rule to
but-1-ene
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
Resonances
(a) and (b) 1H
Chemical shifts 4.90 and 4.95:
H2C=CH-CH2-CH3
At first you might expect to see the H2C=
proton resonance split into a 1:1 doublet by the
adjacent CH proton (n+1 = 2).
However, because the H2C=
protons have slightly different chemical environments
(0.05 ppm difference in chemical shifts), the result is
a more complex resonance line pattern because of the
lack of equivalence of these two protons (several
triplets?).
I presume the difference in the two H2C=
proton chemical shifts is due to slightly different
shielding effects from the asymmetry of the groups on
the other side of the double bond, about which there is
no free rotation.
Resonance
(c) 1H
Chemical shift 5.86 ppm: H2C=CH-CH2-CH3
Again, at first you might expect to see
the CH proton resonance split into a 1:4:6:4:1 quintet
by the adjacent H2C= and -CH2-
protons (n+1 = 5).
However, again, because the H2C=
protons have slightly different chemical environments
(0.05 ppm difference in chemical shifts), the result is
a more complex resonance line pattern because of the
lack of equivalence of these two protons (several
quartets?).
Resonance
(d) 1H
Chemical shift 2.04 ppm: H2C=CH-CH2-CH3
This CH2 proton resonance is
split by the adjacent CH and CH3 protons into
a 1:4:6:4:1 quintet (n+1 = 5).
Evidence for the presence of a CH-C-CH3 grouping
in the molecule of but-1-ene.
Resonance
(e) 1H Chemical shift 0.95 ppm: H2C=CH-CH2-CH3
This methyl group resonance is split by
the adjacent CH2 protons into a 1:2:1 triplet
(n+1 = 2).
Evidence for the presence of a CH2 group
in the molecule of but-1-ene
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
but-1-ene.
|
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:
C4H8
CH3CH2CH=CH3 Interpreting the proton H-1 NMR spectra of but-1-ene, low resolution & high resolution proton
nmr spectra of but-1-ene, H-1 nmr spectrum of but-1-ene, understanding the
hydrogen-1 nmr spectrum of but-1-ene, explaining the line splitting patterns from
spin-spin coupling in the
high resolution H-1 nmr spectra of but-1-ene, revising the H-1 nmr spectrum of
but-1-ene,
proton nmr of but-1-ene, ppm chemical shifts of the H-1 nmr spectrum of
but-1-ene,
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 but-1-ene, how to work out the
number of chemically different protons in the structure of the but-1-ene organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of but-1-ene using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of but-1-ene deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of but-1-ene
examining the 1H nmr spectrum of but-1-ene analysing the 1-H nmr spectrum of
but-1-ene
how do you sketch and interpret the H-1 NMR spectrum of but-1-ene interpreting
interpretation of the 1H proton spin-spin coupling causing line splitting in the
NMR spectrum of but-1-ene
assignment of chemical shifts in the
proton 1H NMR spectrum of but-1-ene formula explaining spin-spin coupling for
line splitting for but-1-ene
1-butene butylene butene alkene
functional group
How do you interpret the H-1 NMR spectrum of
but-1-ene How to interpret
the H-1 NMR spectrum of but-1-ene Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the but-1-ene
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of but-1-ene. How to explain the H-1 NMR spectrum of
but-1-ene. The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the but-1-ene molecule. How to work out the molecular
structure of the but-1-ene molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the but-1-ene
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the but-1-ene
molecule? explaining the spin-spin proton coupling effects in the 1H
NMR spectrum of but-1-ene. 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 but-1-ene
Links associated
with
but-1-ene
The chemistry of ALKENES
revision notes INDEX
The infrared spectrum of
but-1-ene
The mass spectrum of but-1-ene
The C-13 NMR spectrum of
but-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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