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Interpreting
and explaining
the H-1
hydrogen-1 (proton) NMR spectrum of propylbenzene
(1-phenlypropane)
[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
propylbenzene
[spectra updated
Mar 28th
2026 *]
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brown
Re-edit 1H NMR spectrum of C6H5CH2CH2CH3
Links associated with propylbenzene
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H-1 proton NMR spectroscopy -
spectra index
Introductory note on the 1H NMR spectra of propylbenzene
Students and teachers please note my explanation of the
proton NMR spectrum of propylbenzene is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
propylbenzene 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
propylbenzene 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 propylbenzene molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like propylbenzene, 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 - propylbenzene here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of propylbenzene 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 propylbenzene molecule.
propylbenzene,
1-phenylpropane, C9H12
, C6H5CH2CH2CH3
,
,
The
molecular structure
and naming of aromatic compounds
The molecular structure and
naming of alkanes
Interpreting the
H-1 NMR spectrum of
propylbenzene
For relatively simple molecules, the low
resolution H-1 NMR spectrum of propylbenzene is a NOT a good
starting point.
The hydrogen atoms (protons) of propylbenzene
actually occupy 6 different chemical environments so that the
very high resolution NMR
spectra should show 6 peaks of different
1H NMR chemical shifts (diagram above for
propylbenzene).
Although there are 12
hydrogen atoms in the molecule, there are
theoretically 6 possible different chemical
environments for the hydrogen atoms in propylbenzene molecule,
but they are observed as two closely related groups - aryl and alky
group carbon atoms.
C6H5CH2CH2CH3
The low resolution integrated signal
proton ratio 5:2:2:3 is observed
in the above spectrum, but the true 'very high resolution' ratio
is
1:2:2:2:2:3
for the
5 aryl
and
7 alkyl
protons in propylbenzene.
The high resolution H-1 NMR
spectrum of propylbenzene
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of propylbenzene - 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 propylbenzene below.
So, using the chemical shifts and applying the
n+1 rule to
propylbenzene
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 7.40 ppm, aromatic ring proton resonances
There are three proton resonances close
together originating from the benzene ring protons - see
diagram above.
Very high resolution would produce three
peaks in the ratio
(a) 1 :
(b)
2 :
(c) 2 and no doubt
splitting will be observed.
1H resonances
(a) to (c) and indicative
of benzene ring protons and a monosubstituted benzene
compound too.
(d) 1H
Chemical shift 2.57 ppm side-chain CH2 nearest
the benzene ring
This is split into a triplet by the
adjacent CH2 protons.
Evidence for the presence of a CH2 group
in the molecule of propylbenzene
(e) 1H
Chemical shift 1.64 ppm
resonance from the 2nd side-chain CH2
This is split into a 1:5:10:10:5:1
sextet by the CH2 and CH3 protons
from each side (n+1 = 6).
Evidence for the presence of an alkyl
group with adjacent CH2 and CH3 group
either side
in the molecule of propylbenzene
(f) 1H
Chemical shift 0.94 ppm resonance from the side-chain methyl
group.
This is split into a 1:2:1 triplet by
the adjacent CH2 protons (n+1 = 3).
Evidence for another CH2
group in the molecule - see (d).
(d) to (f) provide evidence of a propyl
group in the molecule.
What you can get from the spectrum is a ratio of
5:7
for
aryl:alkyl
protons in propylbenzene (1-phenylpropane) and
evidence of a propyl group in the alkyl side-chain.
Note the arene aromatic protons of the
benzene ring have significantly larger
1H NMR
chemical shifts than the propyl alkyl group of carbon atoms, so
you get two 'bunches' of
1H NMR chemical shifts in propylbenzene.
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
propylbenzene.
|
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
1-phenlypropane
C9H12
C6H5CH2CH2CH3 Interpreting the proton H-1 NMR spectra of propylbenzene, low resolution & high resolution proton
nmr spectra of propylbenzene, H-1 nmr spectrum of propylbenzene, understanding the
hydrogen-1 nmr spectrum of propylbenzene, explaining the line splitting patterns in the
high resolution H-1 nmr spectra of propylbenzene, revising the H-1 nmr spectrum of
propylbenzene,
proton nmr of propylbenzene, ppm chemical shifts of the H-1 nmr spectrum of
propylbenzene,
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 propylbenzene, how to work out the
number of chemically different protons in the structure of the propylbenzene organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of propylbenzene using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of propylbenzene deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of propylbenzene
examining the 1H nmr spectrum of propylbenzene analysing the 1-H nmr spectrum of
propylbenzene how do you sketch and interpret the H-1 NMR spectrum of
propylbenzene
interpreting interpretation of the H-1 proton NMR spectrum of propylbenzene
1-phenylpropane C6H5C3H7
How do you interpret the H-1 NMR spectrum of
propylbenzene How to interpret
the H-1 NMR spectrum of propylbenzene Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the propylbenzene
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of propylbenzene. How to explain the H-1 NMR spectrum of
propylbenzene. The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the propylbenzene molecule. How to work out the molecular
structure of the propylbenzene molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the
propylbenzene
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the propylbenzene
molecule? explaining the spin-spin proton coupling effects in the 1H
NMR spectrum of propylbenzene. 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 propylbenzene
1-phenlypropane
Links associated
with
propylbenzene
The infrared spectrum of
propylbenzene
The mass
spectrum of propylbenzene
TheC-13 NMR spectrum
of Propylbenzene
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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spectroscopy (on the 1H NMR spectrum of propylbenzene,
1-phenylpropane) 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, CCEA advanced level chemistry, US grade 11-12 AP honors
chemistry courses and they will also prove useful to
1st year undergraduate students of chemistry. |
