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The H-1
hydrogen-1 (proton) NMR spectrum of 1,3,5-trimethylbenzene (mesitylene)
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Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study
Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US
K12 grade 11 grade 12 organic chemistry courses involving molecular
spectroscopy analysing H-1 NMR spectra of 1,3,5-trimethylbenzene
(mesitylene)
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H-1 proton NMR spectroscopy -
spectra index
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 - 1,3,5-trimethylbenzene (mesitylene) here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 1,3,5-trimethylbenzene (mesitylene) 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 1,3,5-trimethylbenzene (mesitylene) molecule.
Interpreting the
H-1 NMR spectrum of
1,3,5-trimethylbenzene (mesitylene)
Because of the symmetry of the molecule, the hydrogen atoms (protons) of
1,3,5-trimethylbenzene (mesitylene) can only occupy 2
different chemical environments so that the low/high resolution NMR
spectra should show 2 peaks of different H-1 NMR chemical shifts (diagram above for
1,3,5-trimethylbenzene (mesitylene)).
Although there are 12 hydrogen atoms in the molecule,
there are only 2 possible different chemical
environments for the hydrogen atoms in 1,3,5-trimethylbenzene
(mesitylene) molecule - a very symmetrical molecule.
The integrated signal proton ratio 1:3 observed
in the high resolution H-1 NMR spectrum, corresponds with
the structural formula of 1,3,5-trimethylbenzene (mesitylene) in
terms of the aryl:alkyl protons.
The high resolution H-1 NMR
spectrum of 1,3,5-trimethylbenzene (mesitylene)
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of 1,3,5-trimethylbenzene (mesitylene) - 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 1,3,5-trimethylbenzene (mesitylene) below.
(a) 1H
Chemical shift 6.78 ppm resonance from the benzene ring protons.
All four aromatic protons are equivalent
and no significant splitting observed
(b) 1H
Chemical shift 2.26 ppm from the methyl protons.
All six alkyl protons are equivalent and
no significant splitting observed
What you get from the spectrum is a ratio of
1:3
(actually
3:9)
for
aryl:alkyl
protons in 1,3,5-trimethylbenzene.
|
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
C6H3(CH3)3 Interpreting the proton H-1 NMR spectra of 1,3,5-trimethylbenzene
(mesitylene), low resolution & high resolution proton
nmr spectra of 1,3,5-trimethylbenzene (mesitylene), H-1 nmr spectrum of
1,3,5-trimethylbenzene (mesitylene), understanding the
hydrogen-1 nmr spectrum of 1,3,5-trimethylbenzene (mesitylene), explaining the line splitting patterns in the
high resolution H-1 nmr spectra of 1,3,5-trimethylbenzene (mesitylene), revising the H-1 nmr spectrum of
1,3,5-trimethylbenzene (mesitylene),
proton nmr of 1,3,5-trimethylbenzene (mesitylene), ppm chemical shifts of the H-1 nmr spectrum of
1,3,5-trimethylbenzene (mesitylene),
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 1,3,5-trimethylbenzene
(mesitylene), how to work out the
number of chemically different protons in the structure of the
1,3,5-trimethylbenzene (mesitylene) organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 1,3,5-trimethylbenzene (mesitylene) using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of 1,3,5-trimethylbenzene (mesitylene) deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 1,3,5-trimethylbenzene
(mesitylene)
examining the 1H nmr spectrum of 1,3,5-trimethylbenzene (mesitylene) analysing the 1-H nmr spectrum of
1,3,5-trimethylbenzene (mesitylene) how do you sketch and interpret the H-1 NMR
spectrum of 1,3,5-trimethylbenzene (mesitylene)
interpreting interpretation of the H-1 proton NMR spectrum of
1,3,5-trimethylbenzene (mesitylene)
Links associated
with 1,3,5-trimethylbenzene (mesitylene)
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)
ALL SPECTROSCOPY INDEXES
All Advanced Organic
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