Interpreting the
1H (proton) NMR spectrum of 1-iodobutane
(butyl iodide)
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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-iodobutane
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H-1 proton NMR spectroscopy -
spectra index
See also
comparison of the infrared, mass, 1H NMR and 13C NMR
spectra of the four isomers of C4H9I
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-iodobutane here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 1-iodobutane 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-iodobutane molecule.
1-iodobutane, (n-butyl
iodide), C4H9I,
CH3-CH2-CH2-CH2-I
Interpreting the
H-1 NMR spectrum of
1-iodobutane
In terms of spin-spin coupling from the possible proton magnetic orientations,
for 1-iodobutane I
have only considered the interactions of
non-equivalent protons on adjacent carbon atoms
e.g. -CH2-CH3, -CH2-CH2- protons
etc.
For relatively simple molecules, the low
resolution H-1 NMR spectrum of 1-iodobutane is a good starting point
(low resolution diagram above).
The 9 hydrogen atoms (protons) of 1-iodobutane occupy
4
different chemical environments so that the low resolution NMR
spectra should show 4 principal resonance peaks of different H-1 NMR chemical shifts (diagram above for
1-iodobutane).
CH3CH2CH2CH2I
Note the
proton ratio 3:2:2:2 of the 4 colours of the
9 protons of 1-iodobutane
in the 4 chemically different proton environments
Chemical shifts (a) to (d) on the H-1 NMR
spectrum diagram for 1-iodobutane.
Although there are 9 hydrogen atoms in the molecule, the
proton NMR spectrum shows there are only 4 possible different chemical
environments for the hydrogen atoms in 1-iodobutane molecule.
The integrated proton signal ratio
3:2:2:2 observed
in the high resolution H-1 NMR spectrum, corresponds with
the structural formula of 1-iodobutane.
The high resolution 1H NMR
spectrum of 1-iodobutane
The high resolution spectra of 1-iodobutane
shows 4 groups of proton resonances and in the
3:2:2:2
ratio expected from the
structural
formula of 1-iodobutane, but we can now consider the splitting of
resonance lines from the spin-spin coupling in the molecule of
1-iodobutane.
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of 1-iodobutane - 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-iodobutane below.
So, using the chemical shifts and applying the
n+1 rule to
1-iodobutane
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
1H NMR resonance
(a) 1H Chemical shift 0.93 ppm: CH3CH2CH2CH2I
This resonance is split into a 1:2:1
triplet by the adjacent CH2 protons (n+1 =
3).
Evidence for the presence of a CH2 group
in the molecule of 1-iodobutane
1H NMR resonance
(b) 1H
Chemical shift 1.42 ppm: CH3CH2CH2CH2I
This resonance is split into a
1:5:10:10:5:1 sextet by the adjacent CH3 and CH2 protons
(on either side, so n=1 = 6).
Evidence for the presence of a ? group
in the molecule of 1-iodobutane
1H NMR resonance
(c) 1H
Chemical shift 1.80 ppm: CH3CH2CH2CH2I
This resonance is split into a 1:4:6:4:1
quintet by the adjacent CH2 protons on either
side, so n=1 = 5.
Evidence for the presence of a CH2-CHx-CH2 grouping
in the molecule of 1-iodobutane (x = 1, or 2, as in this
case).
1H NMR resonance
(d) 1H
Chemical shift 3.20 ppm: CH3CH2CH2CH2I
This resonance is split into a 1:2:1
triplet by the adjacent CH2 protons (n+1 =
3).
Evidence for the presence of a at least
one other CH2 group
in the molecule of 1-iodobutane (see resonance (a)
above).
Note the decreasing effect on the 1H chemical
shift as the proton is further from the more electronegative iodine atom
in 1-iodobutane.
Comparing the infrared, mass, 1H NMR and 13C NMR
spectra of the 4 halogenoalkane isomers of C4H9I
NOTE: The images are linked to their
original detailed spectral analysis pages AND can be doubled in
size with touch screens to
increase the definition to the original 1-iodobutane,
2-iodobutane, 1-iodo-2-methylpropane and 2-iodo-2-methylpropane
image sizes. These four molecules
are structural isomers of molecular formula C4H9I
and
exemplify the infrared, mass, 1H NMR and 13C NMR spectra of lower
aliphatic halogenoalkanes (haloalkanes, alkyl halides,
iodoalkanes, alkyl iodides). |
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INFRARED SPECTRA
(above):
Apart from the significant differences in the fingerprint region at
wavenumbers 1500 to 400 cm-1, there are no other
great striking differences, but each could be identified from
its infrared spectrum. |
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MASS SPECTRA (above):
All four give the parent molecular ion of m/z 184, but it is
only a relatively tiny peak for 2-iodo-2-methylpropane. All four
give the base ion peak of m/z 57. All four give prominent peaks
for m/z ions 29 and 41 and all give a tiny peak from an ionised
iodine atom at m/z 127. They look quite similar to me and lack a
clear fingerprint fragmentation pattern. |
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1H NMR SPECTRA (above): The 1H NMR spectra of
all three molecules give different proton ratios i.e.1-iodobutane
four peaks 3:2:2:2, 2-iodobutane four peaks 3:3:2:1,
1-iodo-2-methylpropane three peaks 6:2:1 and
2-iodo-2-methylpropane one peak '1' (effectively no ratio
involved), so all four molecular structures can be distinguished from each other by their
1H NMR spectra proton ratios, numbers of peaks and (n+1)
rule splitting patterns. |
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13C NMR SPECTRA
(above): The
13C NMR spectra of the four molecules show various numbers of
carbon-13 chemical environments i.e 1-iodobutane and
2-iodobutane show four 13C NMR resonances,
1-iodo-2-methylpropane three 13C NMR resonances and
2-iodo-2-methylpropane only two 13C resonances. Therefore
1-iodo-2-methylpropane and 2-iodo-2-methylpropane can be
distinguished from the other three by their number of resonances
in their 13C NMR spectra, but 1-iodobutane and 2-iodobutane
cannot be distinguished from each other from their number of 13C
NMR resonance lines - other data would be required. |
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 |
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1 |
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1
creates a doublet |
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1 |
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1 |
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2
creates a triplet |
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1 |
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2 |
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1 |
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3
creates a quartet |
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1 |
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3 |
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3 |
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1 |
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4
creates a quintet |
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1 |
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4 |
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6 |
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4 |
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1 |
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5
creates a sextet |
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1 |
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5 |
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10 |
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10 |
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5 |
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1 |
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6
creates a septet |
1 |
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6 |
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15 |
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20 |
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15 |
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6 |
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1 |
Key words & phrases:
isomer
of molecular formula C4H9I CH3CH2CH2CH2I
Interpreting the proton H-1 NMR spectra of 1-iodobutane, low resolution & high
resolution proton nmr spectra of 1-iodobutane, H-1 nmr spectrum of 1-iodobutane, understanding the
hydrogen-1 nmr spectrum of 1-iodobutane, explaining the line splitting patterns from
spin-spin coupling in the high resolution H-1 nmr spectra of 1-iodobutane, revising
the H-1 nmr spectrum of 1-iodobutane, proton nmr of 1-iodobutane, ppm chemical shifts of the H-1
nmr spectrum of 1-iodobutane, explaining and analyzing spin spin line splitting in the
H-1 nmr spectrum, how to construct the diagram of the 1H nmr spectrum of
1-iodobutane, how to work out the
number of chemically different protons in the structure of the 1-iodobutane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 1-iodobutane using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of 1-iodobutane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 1-iodobutane
examining the 1H nmr spectrum of 1-iodobutane analysing the 1H nmr spectrum of
1-iodobutane
how do you sketch and interpret the H-1 NMR spectrum of 1-iodobutane
interpreting interpretation of the 1H proton spin-spin coupling causing line
splitting in the NMR spectrum of 1-iodobutane
assignment of chemical shifts in the
proton 1H NMR spectrum of 1-iodobutane formula explaining spin-spin coupling for
line splitting for 1-iodobutane
functional group
haloalkane halogenoalkane alkyl bromide n-butyl
iodide Molecular structure diagram of the
proton NMR diagram for the 1H NMR spectrum of 1-iodobutane. The proton ratio in the
1H NMR spectrum of 1-iodobutane. Deducing the number of different chemical
environments of the protons in the 1-iodobutane molecule from the 1H chemical shifts
in the hydrogen-1 NMR spectrum of 1-iodobutane. Analysing the high resolution 1H NMR
spectrum of 1-iodobutane. Analysing the low resolution 1H NMR spectrum of
1-iodobutane. You
may need to know the relative molecular mass of 1-iodobutane to deduce the molecular
formula from the proton ratio of the 1H NMR spectrum of 1-iodobutane. Revision notes
on the proton NMR spectrum of 1-iodobutane. Matching and deducing the structure of
the 1-iodobutane molecule from its hydrogen-1 NMR spectrum.
Proton NMR spectroscopy of halogenoalkanes iodoalkanes,
1H NMR spectra of 1-iodobutane, an isomer of molecular formula
C4H9I
Links associated
with 1-iodobutane
The chemistry of HALOGENOALKANES (haloalkanes)
revision notes INDEX
The infrared spectrum of 1-iodobutane
(n-butyl iodide)
The mass
spectrum of 1-iodobutane (n-butyl iodide)
The
C-13 NMR spectrum of 1-iodobutane (n-butyl iodide)
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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