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H-1
hydrogen-1 (proton) NMR spectrum of 2-chlorobutane
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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 2-chlorobutane
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H-1 proton NMR spectroscopy -
spectra index
See also
Comparing infrared, mass, 1H NMR & 13C NMR
spectra of the 4 structural isomers of C4H9Cl
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 - 2-chlorobutane here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 2-chlorobutane 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 2-chlorobutane molecule.
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2-chlorobutane
For more see
Molecular structure, classification and
naming of
halogenoalkanes (haloalkanes)
Interpreting the
H-1 NMR spectrum of
2-chlorobutane
In terms of spin-spin coupling from the possible proton magnetic orientations,
for 2-chlorobutane I
have only considered the interactions of
non-equivalent protons on adjacent carbon atoms
e.g. -CH-CH3.
For relatively simple molecules, the low
resolution H-1 NMR spectrum of 2-chlorobutane is a good starting point
(low resolution diagram above).
The hydrogen atoms (protons) of 2-chlorobutane occupy
4
different chemical environments so that the low/high resolution NMR
spectra should show 4 principal peaks of different H-1 NMR chemical shifts (diagram above for
2-chlorobutane).
CH3CHClCH2CH3
Note the proton ratio 3:1:2:3 of the 4 colours of the protons
in the 4 chemically different environments
Chemical shifts (a) to (d) on the H-1 NMR
spectrum diagram for 2-chlorobutane.
Although there are 9 hydrogen atoms in the molecule,
there are only 4 possible different chemical
environments for the hydrogen atoms in 2-chlorobutane molecule.
The integrated signal proton ratio 3:1:2:3 observed
in the high resolution H-1 NMR spectrum, corresponds with
the structural formula of 2-chlorobutane.
The high resolution 1H NMR
spectrum of 2-chlorobutane
All low and high resolution spectra of
2-chlorobutane
show 4 groups of proton resonances and in the ratio expected from the
formula of 2-chlorobutane.
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of 2-chlorobutane - 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 2-chlorobutane below.
So, using the chemical shifts and applying the
n+1 rule to
2-chlorobutane
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
(a) 1H
Chemical shift 1.50 ppm, CH3 protons: CH3CHClCH2CH3
This 1H resonance is split by the
adjacent CH proton into a 1:1 doublet (n+1 = 2).
Evidence for the presence of a CH3 group
in the molecule of 2-chlorobutane
(b) 1H
Chemical shift 3.97 ppm, CH proton : CH3CHClCH2CH3
This 1H resonance is split by the
adjacent CH3 and CH2 protons into
a 1:5:10:10:5:1 sextet (n+1 = 6).
Evidence for the presence of a CH3-C-CH2 grouping
in the molecule of 2-chlorobutane
(c) 1H
Chemical shift 1.71 ppm, CH2 protons : CH3CHClCH2CH3
This 1H resonance is split by the
adjacent CH3 and CH protons into a 1:4:6:4:1
quintet (n+1 = 5).
Evidence for the presence of a CH3-C-CH group
in the molecule of 2-chlorobutane
(d) 1H
Chemical shift 1.02 ppm, CH3 protons : CH3CHClCH2CH3
This 1H resonance is split by the
adjacent CH2 protons into a 1:2:1 triplet
(n+1 = 3).
Evidence for the presence of a CH2 group
in the molecule of 2-chlorobutane
Note the decreasing effect on the 1H chemical shift as the
proton is further from the more electronegative chlorine atom in 2-chlorobutane.
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Comparing the infrared, mass, 1H NMR and 13C NMR
spectra of the 4 halogenoalkane isomers of C4H9Cl
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-chlorobutane,
2-chlorobutane, 1-chloro-2-methylpropane and 2-chloro-2-methylpropane
image sizes. These four molecules
are structural isomers of molecular formula C4H9Cl
and
exemplify the infrared, mass, 1H NMR and 13C NMR spectra of lower
aliphatic halogenoalkanes (haloalkanes, alkyl halides,
chloroalkanes, alkyl chlorides). |
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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. The infrared spectrum of
2-chloro-2-methylpropane is noticeably simpler in the
fingerprint region, perhaps due to
the greater symmetry of the molecule. |
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MASS SPECTRA (above):
Theoretically, all four can give the parent molecular ions of
m/z 92 and 94, but they are all relatively tiny peaks.
2-chlorobutane and 2-chloro-2-methylpropane give a base ion peak
of m/z 57. The base ion peak for 1-chlorobutane is m/z 56 and
that of 1-chloro-2-methylpropane is m/z 43. Each gives different
patterns of pairs of m/z values two mass units apart, in the
peak height ratio of 3:1, if the positive fragment contains a
chlorine atom (35Cl or 37Cl) e.g look for
m/z pairs 49/51, 63/65 and 77/79 in their mass spectra. |
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1H NMR SPECTRA
(above): The 1H NMR spectra of all four molecules give different
integrated proton ratios i.e.1-chlorobutane
four peaks of ratio 3:2:2:2; 2-chlorobutane four peaks of
ratio 3:3:2:1,
1-chloro-2-methylpropane three peaks of ratio 6:2:1 and
2-chloro-2-methylpropane gives just 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-chlorobutane and
2-chlorobutane show four 13C NMR resonances,
1-chloro-2-methylpropane three 13C NMR resonances and
2-chloro-2-methylpropane only two 13C resonances (3 and 2
chemical environments respectively. Therefore
1-chloro-2-methylpropane and 2-chloro-2-methylpropane can be
distinguished from the other three by their number of resonances
in their 13C NMR spectra, but 1-chlorobutane and 2-chlorobutane
cannot be distinguished from each other from their number of 13C
NMR resonance lines - other data would be required. |
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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:
C4H9Cl
CH3CHClCH2CH3 Interpreting the proton H-1 NMR spectra of 2-chlorobutane, low resolution & high resolution proton
nmr spectra of 2-chlorobutane, H-1 nmr spectrum of 2-chlorobutane, understanding the
hydrogen-1 nmr spectrum of 2-chlorobutane, explaining the line splitting patterns from
spin-spin coupling in the
high resolution H-1 nmr spectra of 2-chlorobutane, revising the H-1 nmr spectrum of
2-chlorobutane,
proton nmr of 2-chlorobutane, ppm chemical shifts of the H-1 nmr spectrum of
2-chlorobutane,
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 2-chlorobutane, how to work out the
number of chemically different protons in the structure of the 2-chlorobutane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 2-chlorobutane using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of 2-chlorobutane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 2-chlorobutane
examining the 1H nmr spectrum of 2-chlorobutane analysing the 1-H nmr spectrum of
2-chlorobutane how do you sketch and interpret the H-1 NMR spectrum of
2-chlorobutane
interpreting interpretation of the 1H proton spin-spin coupling causing line
splitting in the NMR spectrum of 2-chlorobutane
assignment of chemical shifts in the
proton 1H NMR spectrum of 2-chlorobutane formula explaining spin-spin coupling for line splitting
of sec-butyl chloride
Molecular structure diagram of the
proton NMR diagram for the 1H NMR spectrum of 2-chlorobutane. The proton ratio in the
1H NMR spectrum of 2-chlorobutane. Deducing the number of different chemical
environments of the protons in the 2-chlorobutane molecule from the 1H chemical shifts
in the hydrogen-1 NMR spectrum of 2-chlorobutane. Analysing the high resolution 1H NMR
spectrum of 2-chlorobutane. Analysing the low resolution 1H NMR spectrum of
2-chlorobutane. You
may need to know the relative molecular mass of 2-chlorobutane to deduce the molecular
formula from the proton ratio of the 1H NMR spectrum of 2-chlorobutane. Revision notes
on the proton NMR spectrum of 2-chlorobutane. Matching and deducing the structure of
the 2-chlorobutane molecule from its hydrogen-1 NMR spectrum.
Proton NMR spectroscopy of aliphatic
halogenoalkanes haloalkanes alkyl halides alkyl chlorides chloroalkanes,
1H NMR spectra of 2-chlorobutane, an isomer of molecular formula
C4H9Cl explaining the proton 1H NMR
spectrum of 2-chlorobutane
Links associated
with 2-chlorobutane
The chemistry of HALOGENOALKANES (haloalkanes)
revision notes INDEX
The
infrared spectrum of 2-chlorobutane (sec-butyl
chloride)
The mass
spectrum of 2-chlorobutane (sec-butyl
chloride)
The
C-13 NMR spectrum of 2-chlorobutane (sec-butyl
chloride)
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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