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Interpreting the H-1
hydrogen-1 (proton) NMR spectrum of (1-methylethyl)benzene,
2-phenylpropane
(cumene,
isopropylbenzene)
[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 analysis of
cumene
[spectra page updated
Mar 22nd 2026 *]
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Re-edit 1H
NMR spectrum of cumene
C6H5CH(CH3)2
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H-1 proton NMR spectroscopy -
spectra index
Introductory note on the 1H NMR spectra of cumene
Students and teachers please note my explanation of the
proton NMR spectrum of cumene is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
cumene 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
cumene 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 cumene molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like cumene, 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 - (1-methylethyl)benzene (cumene) here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of (1-methylethyl)benzene (cumene) 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 (1-methylethyl)benzene (cumene) molecule.
(1-methylethyl)benzene,
2-phenylpropane,
C9H12,
, (cumene)
The
molecular structure
and naming of aromatic compounds
Interpreting the
H-1 NMR spectrum of
(1-methylethyl)benzene (2-phenylpropane, cumene)
For relatively simple molecules, the low
resolution H-1 NMR spectrum of (1-methylethyl)benzene
(cumene) is NOT a good starting point (diagram above).
The 1H resonances for the benzene ring protons
are very close together, but you can get the ratio of aryl:alkyl
protons of 5:7 i.e. from two 'bunches' of chemical shifts close
together.
From high resolution spectra, you can observe the hydrogen atoms (protons) of
(1-methylethyl)benzene (cumene) occupy 5 different chemical
environments but that the low resolution NMR
spectra only shows three (diagram above for
(1-methylethyl)benzene (cumene).
Although there are 12 hydrogen atoms in the molecule,
there are only 5 possible different chemical
environments (5
1H shifts) for the hydrogen atoms in (1-methylethyl)benzene (cumene) molecule.
The high resolution H-1 NMR
spectrum of (1-methylethyl)benzene (cumene)
The very high resolution spectra of
(1-methylethyl)benzene (cumene)
should show 5 groups of proton resonances and in the
1:2:2:1:6 ratio
for
aryl:alkyl expected from the
formula of (1-methylethyl)benzene (cumene).
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of (1-methylethyl)benzene (cumene) - 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 (1-methylethyl)benzene (cumene) below.
So, using the chemical shifts and applying the
n+1 rule to
(1-methylethyl)benzene (cumene)
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
(a) to (c) 1H
Chemical shift 7.02 to 7.34 ppm for benzene ring protons
These 1H resonances are close together
You need
very high resolution to sort (a) to (c) and this 'bunch' of chemical shifts are indicative of benzene ring
protons and a monosubstituted benzene compound too.
(d) 1H
Chemical shift
δ 2.88 ppm side-chain CH proton
This resonance is split into a
1:6:15:20:15:6:1 septet by the six methyl protons of the
two adjacent carbon atoms (n+1 = 7).
Evidence for the presence of a CH3CHxCH3
alkyl group
in the molecule of (1-methylethyl)benzene (cumene)
(e) 1H
Chemical shift
δ 1.24 ppm for the side-chain 2 x CH3
protons.
This resonance is split into a doublet
by the CH proton (n+1 = 2).
Evidence for the presence of a CH group
in the molecule of (1-methylethyl)benzene (cumene).
What you can get from the spectrum is a ratio of
5:7
for
aryl:alkyl
protons in 1(1-methylethyl)benzene (2-phenylpropane).
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 |
Key words & phrases:
C9H12
C6H5CH(CH3)2 Interpreting the proton H-1 NMR spectra of (1-methylethyl)benzene
(cumene), low resolution & high resolution proton
nmr spectra of (1-methylethyl)benzene (cumene), H-1 nmr spectrum of
(1-methylethyl)benzene (cumene), understanding the
hydrogen-1 nmr spectrum of (1-methylethyl)benzene (cumene), explaining the line splitting patterns in the
high resolution H-1 nmr spectra of (1-methylethyl)benzene (cumene), revising the H-1 nmr spectrum of
(1-methylethyl)benzene (cumene),
proton nmr of (1-methylethyl)benzene (cumene), ppm chemical shifts of the H-1 nmr spectrum of
(1-methylethyl)benzene (cumene),
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 (1-methylethyl)benzene
(cumene), how to work out the
number of chemically different protons in the structure of the
(1-methylethyl)benzene (cumene) organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of (1-methylethyl)benzene (cumene) using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of (1-methylethyl)benzene (cumene) deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of (1-methylethyl)benzene
(cumene)
examining the 1H nmr spectrum of (1-methylethyl)benzene (cumene) analysing the 1-H nmr spectrum of
(1-methylethyl)benzene (cumene) how do you sketch and interpret the H-1 NMR
spectrum of (1-methylethyl)benzene (cumene)
interpreting interpretation of the H-1 proton NMR spectrum of
(1-methylethyl)benzene (cumene)
2-phenylpropane
How do you interpret the H-1 NMR spectrum of
cumene C9H12 How to interpret
the H-1 NMR spectrum of cumene C9H12 Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the cumene C9H12
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of cumene C9H12. How to explain the H-1 NMR spectrum of
cumene C9H12. The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the cumene C9H12 molecule. How to work out the molecular
structure of the cumene C9H12 molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the cumene
C9H12
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the cumene C9H12
molecule? explaining the spin-spin proton coupling effects in the 1H
NMR spectrum of cumene C9H12.
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 cumene C9H12
Links associated
with
(1-methylethyl)benzene (cumene)
The
infrared spectrum of
(1-methylethyl)benzene or 2-phenylpropane (Cumene)
The mass
spectrum of (1-methylethyl)benzene or 2-phenylpropane (Cumene)
The C-13 NMR spectrum of
(1-methylethyl)benzene or 2-phenylpropane (Cumene)
The chemistry of AROMATIC COMPOUNDS
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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