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The H-1
hydrogen-1 (proton) NMR spectrum of 1,1-dibromoethane
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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 1,1-dibromoethane
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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 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 - 1,1-dibromoethane here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 1,1-dibromoethane 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 1,1-dibromoethane molecule.
1,1-dibromoethane,
C2H4Br2,
CH3CHBr2
Interpreting the
H-1 NMR spectrum of
1,1-dibromoethane
In terms of spin-spin coupling from the possible proton magnetic orientations,
for 1,1-dibromoethane I
have only considered the interactions of
non-equivalent protons on adjacent carbon atoms
e.g. -CH-CH3
protons.
Theoretically the hydrogen atoms (protons) of
1,1-dibromoethane occupy 2
different chemical environments so that the low/high resolution NMR
spectra should show 2 principal peaks of different H-1 NMR chemical shifts (diagram above for
1,1-dibromoethane).
CH3CHBr2
Note the proton ratio 3:1 of the 2 colours of the protons
in the 2 chemically different environments
Chemical shifts (a) to (b) on the H-1 NMR
spectrum diagram for 1,1-dibromoethane.
Although there are 4 hydrogen atoms in the molecule,
but there are only 2 possible different chemical
environments for the hydrogen atoms in 1,1-dibromoethane molecule.
The integrated signal proton ratio 3:1 observed
in the high resolution H-1 NMR spectrum, corresponds with
the structural formula of 1,1-dibromoethane.
The high resolution 1H NMR
spectrum of 1,1-dibromoethane
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of 1,1-dibromoethane - 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 1,1-dibromoethane below.
So, using the chemical shifts and applying the
n+1 rule to
1,1-dibromoethane
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
(a) 1H
Chemical shift 5.84 ppm, CH proton: CH3CHBr2
The CH proton resonance is split by the
other CH3 protons into a 1:3:3:1 quartet (n+1
= 4)
Evidence for the presence of a CH3 group
in the molecule of 1,1-dibromoethane
(b) 1H
Chemical shift 2.46 ppm, -CH3 protons: CH3CHBr2
The CH3 protons resonance is
split by the CH proton into a 1:1 doublet (n+1 = 2)
Evidence for the presence of a -CH- group
in the molecule of 1,1-dibromoethane.
|
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:
C2H4Br2
CH3CHBr2 Interpreting the proton H-1 NMR spectra of 1,1-dibromoethane, low resolution & high resolution proton
nmr spectra of 1,1-dibromoethane, H-1 nmr spectrum of 1,1-dibromoethane, understanding the
hydrogen-1 nmr spectrum of 1,1-dibromoethane, explaining the line splitting patterns from
spin-spin coupling in the
high resolution H-1 nmr spectra of 1,1-dibromoethane, revising the H-1 nmr spectrum of
1,1-dibromoethane,
proton nmr of 1,1-dibromoethane, ppm chemical shifts of the H-1 nmr spectrum of
1,1-dibromoethane,
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 1,1-dibromoethane, how to work out the
number of chemically different protons in the structure of the 1,1-dibromoethane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 1,1-dibromoethane using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of 1,1-dibromoethane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 1,1-dibromoethane
examining the 1H nmr spectrum of 1,1-dibromoethane analysing the 1-H nmr spectrum of
1,1-dibromoethane how do you sketch and interpret the H-1 NMR spectrum of
1,1-dibromoethane
interpreting interpretation of the 1H proton spin-spin coupling causing line
splitting in the NMR spectrum of 1,1-dibromoethane
assignment of chemical shifts in the
proton 1H NMR spectrum of 1,1-dibromoethane formula explaining spin-spin coupling for line splitting
Links associated
with 1,1-dibromoethane
The chemistry of HALOGENOALKANES (haloalkanes)
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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