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The H-1
hydrogen-1 (proton) NMR spectrum of 1,3-dimethylbenzene
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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-dimethylbenzene
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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-dimethylbenzene here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 1,3-dimethylbenzene 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-dimethylbenzene molecule.
1,3-dimethylbenzene, C8H10,
,
Interpreting the
H-1 NMR spectrum of
1,3-dimethylbenzene
For relatively simple molecules, the low
resolution H-1 NMR spectrum of 1,3-dimethylbenzene is NOT a good starting point
because the three 1H resonances from the benzene ring protons
are very close together.
From high resolution spectra you would expect the hydrogen atoms (protons) of
1,3-dimethylbenzene occupy 4 different chemical environments (diagram above for
1,3-dimethylbenzene).
Although there are 10 hydrogen atoms in the molecule,
there are only 4 possible different chemical
environments for the hydrogen atoms in 1,3-dimethylbenzene molecule.
The integrated signal proton ratio is
actually for
aryl:alkyl
protons:
1:2:1:6,
when observed
in the high resolution H-1 NMR spectrum, corresponding with
the structural formula of 1,3-dimethylbenzene.
What you can get from the spectrum is a
ratio of 2:3 for aryl/alkyl protons in 1,3-dimethylbenzene.
The high resolution H-1 NMR
spectrum of 1,3-dimethylbenzene
All low and high resolution spectra of
1,3-dimethylbenzene
show 4 groups of proton resonances and in the 4 ratio expected from the
formula of 1,3-dimethylbenzene.
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of 1,3-dimethylbenzene - 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-dimethylbenzene below.
(a) 1H
Chemical shift 7.11 ppm (ring carbon atom 5 proton)
Theoretically, the (a) proton resonance
will be split into a 1:2:1 triplet by the (b) protons
(n+1 = 3).
(b) 1H
Chemical shift 6.94 ppm (ring carbon atom protons 4 and 6)
Theoretically, the (b) proton resonance
will be split into a 1:1 doublet by the (a) protons (n+1
= 2).
(c) 1H
Chemical shift 6.96 ppm (ring carbon atom 2)
This resonance will not be split as
there are no adjacent protons on the neighbouring carbon
atoms.
1H resonances (a) to (c) are close
together at ~7 ppm and evidence for a disubstituted benzene ring -
four ring protons.
(d) 1H
Chemical shift 6.96 ppm (alkyl protons)
The two methyl groups consist of 6
equivalent protons and show no significant resonance
splitting as there is no proton on the adjacent carbon
atom of the benzene ring.
What you can get from the spectrum is a
ratio of
2:3 for
aryl:alkyl protons in 1,3-dimethylbenzene.
|
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: meta-xylene
C8H10 C6H4(CH3)2 Interpreting the proton H-1 NMR spectra of 1,3-dimethylbenzene, low resolution & high resolution proton
nmr spectra of 1,3-dimethylbenzene, H-1 nmr spectrum of 1,3-dimethylbenzene, understanding the
hydrogen-1 nmr spectrum of 1,3-dimethylbenzene, explaining the line splitting patterns in the
high resolution H-1 nmr spectra of 1,3-dimethylbenzene, revising the H-1 nmr spectrum of
1,3-dimethylbenzene,
proton nmr of 1,3-dimethylbenzene, ppm chemical shifts of the H-1 nmr spectrum of
1,3-dimethylbenzene,
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-dimethylbenzene, how to work out the
number of chemically different protons in the structure of the
1,3-dimethylbenzene organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 1,3-dimethylbenzene using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of 1,3-dimethylbenzene deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 1,3-dimethylbenzene
examining the 1H nmr spectrum of 1,3-dimethylbenzene analysing the 1-H nmr spectrum of
1,3-dimethylbenzene how do you sketch and interpret the H-1 NMR spectrum of
1,3-dimethylbenzene
interpreting interpretation of the H-1 proton NMR spectrum of
1,3-dimethylbenzene
m-xylene
Molecular structure diagram of the
proton NMR diagram for the 1H NMR spectrum of 1,3-dimethylbenzene. The proton ratio in the
1H NMR spectrum of 1,3-dimethylbenzene. Deducing the number of different chemical
environments of the protons in the 1,3-dimethylbenzene molecule from the 1H chemical shifts
in the hydrogen-1 NMR spectrum of 1,3-dimethylbenzene. Analysing the high resolution 1H NMR
spectrum of 1,3-dimethylbenzene. Analysing the low resolution 1H NMR spectrum of
1,3-dimethylbenzene. You
may need to know the relative molecular mass of 1,3-dimethylbenzene to deduce the molecular
formula from the proton ratio of the 1H NMR spectrum of 1,3-dimethylbenzene. Revision notes
on the proton NMR spectrum of 1,3-dimethylbenzene. Matching and deducing the structure of
the 1,3-dimethylbenzene molecule from its hydrogen-1 NMR spectrum.
Proton NMR spectroscopy of aromatic arenes,
1H NMR spectra of 1,3-dimethylbenzene, an isomer of molecular formula
C8H10
Links associated
with 1,3-dimethylbenzene
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
Chemistry Notes
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