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Interpreting
and explaining the
H-1 hydrogen-1 (proton) NMR spectrum of N-methylethanamine
(ethylmethylamine)
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Dr Phil Brown PhD:
Doc Brown's advanced level organic chemistry exam revision notes
suitable for students of UK A level chemistry courses & US K12 grade
11, grade 12 and AP honors chemistry courses: Molecular
spectroscopy - analysing the 1H NMR spectra of ethylmethylamine
[spectra
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1H NMR spectrum of CH3NHCH2CH3
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H-1 proton NMR spectroscopy -
spectra index
Introductory note on the 1H NMR spectra of N-methylethanamine
(ethylmethylamine)
Students and teachers please note my explanation of the
proton NMR spectrum of N-methylethanamine (ethylmethylamine) is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
N-methylethanamine (ethylmethylamine) are
confined to a proton spin-spin
coupling effects analysed using the n+1 rule for adjacent
non-equivalent proton fields (n is the number of neighbouring
protons in a non-equivalent different chemical environment for the
N-methylethanamine (ethylmethylamine) molecule).
It is assumed that the integrated intensities of the
δ
chemical shifts give the ratio of the protons in the different
non-equivalent chemical environments of the N-methylethanamine
(ethylmethylamine) molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like N-methylethanamine (ethylmethylamine), is CDCl3 and other
deuterated solvents to avoid confusion with a 1H NMR
signal, 2D (2H) has a different chemical
shift.
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 - N-methylethanamine (ethylmethylamine) here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of N-methylethanamine (ethylmethylamine) 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 N-methylethanamine (ethylmethylamine) molecule.
N-methylethanamine, N-methylethylamine, ethylmethylamine,
 ,
The classification,
structure and naming of
organic nitrogen compounds
Interpreting the
H-1 NMR spectrum of
N-methylethanamine (ethylmethylamine)
In terms of spin-spin coupling from the possible proton magnetic orientations,
for N-methylethanamine (ethylmethylamine) I
have only considered the interactions of
non-equivalent protons on adjacent carbon atoms
e.g. -CH2-CH3
protons (but see note on problems with N-H proton resonance).
For relatively simple molecules, the low
resolution H-1 NMR spectrum of N-methylethanamine
(ethylmethylamine) is a good starting point
(low resolution diagram above).
The 9 hydrogen atoms (protons) of
N-methylethanamine (ethylmethylamine) occupy
4
different chemical environments so that the low resolution NMR
spectra should show 4 principal
1H peaks of different H-1 NMR chemical shifts (diagram above for
N-methylethanamine (ethylmethylamine)).
CH3NHCH2CH3
Note the proton ratio 3:1:2:3 of the 4 colours of the
9 protons of N-methylethanamine (ethylmethylamine)
in the 4 chemically different proton environments
Chemical shifts (a) to (d) on the H-1 NMR
spectrum diagram for N-methylethanamine (ethylmethylamine).
Although there are 9 hydrogen atoms in the molecule,
there are only 9 possible different chemical
environments for the hydrogen atoms in N-methylethanamine
(ethylmethylamine) 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 N-methylethanamine (ethylmethylamine).
The high resolution 1H NMR
spectrum of N-methylethanamine (ethylmethylamine)
The high resolution spectra of
N-methylethanamine (ethylmethylamine)
shows 4 groups of proton resonances and in the 3:1:2:3 ratio expected from the
structural
formula of N-methylethanamine (ethylmethylamine).
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of N-methylethanamine (ethylmethylamine) - 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 N-methylethanamine (ethylmethylamine) below.
So, using the chemical shifts and applying the
n+1 rule to
N-methylethanamine (ethylmethylamine)
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
(a) 1H
Chemical shift 2.30 ppm, methyl group protons: CH3NHCH2CH3
This resonance appears as a singlet
chemical shift, the adjacent amine protons do not
normally cause splitting.
(b) 1H
Chemical shift 1.20 ppm, amine group proton: CH3NHCH2CH3
This resonance appears as a singlet
chemical shift, the amine proton resonance is not
normally split by adjacent C-H protons.
If deuterium oxide (D2O,
where D = 2H) is added to the NMR amine sample
i.e. used as the solvent,
the 1H protons are rapidly replaced by
2H protons in the ethylmethylamine molecule.
R2N-H
+ D-O-D
R2N-D
+ D-O-H
The 2H chemical shift frequency is
different to the 1H chemical shift
frequency, so the effect of D2O is to
remove
(or reduce intensity of)
the chemical shift for the NH proton from the 1H NMR
spectrum of ethylmethylamine, thereby identifying the original
1H chemical shift as belonging to the
amine group N-H protons and not a C-H proton of the
ethylmethylamine molecule.
(c) 1H
Chemical shift 2.65 ppm, CH2 group protons: CH3NHCH2CH3
This resonance is spilt into a 1:3:3:1
quartet by the adjacent CH3 protons (n+1 =
3), the adjacent amine protons do not normally cause
splitting.
Evidence for the presence of a CH3 group
in the molecule of N-methylethanamine (ethylmethylamine)
(d) 1H
Chemical shift 1.10 ppm, methyl group protons: CH3NHCH2CH3
This resonance is spilt 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 N-methylethanamine (ethylmethylamine)
The splitting pattern from proton
spin-spin coupling effects is analysed using the n+1 rule for
adjacent non-equivalent proton fields (n is the number of
neighbouring protons in a non-equivalent different chemical
environment) and applied to the 1H NMR spectrum of
N-methylethanamine (ethylmethylamine).
|
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:
isomer
of C3H9N CH3NHCH2CH3 CH3CH2NHCH3 Interpreting the proton H-1 NMR spectra of N-methylethanamine
(ethylmethylamine), low resolution & high resolution proton
nmr spectra of N-methylethanamine (ethylmethylamine), H-1 nmr spectrum of
N-methylethanamine (ethylmethylamine), understanding the
hydrogen-1 nmr spectrum of N-methylethanamine (ethylmethylamine), explaining the line splitting patterns from
spin-spin coupling in the
high resolution H-1 nmr spectra of N-methylethanamine (ethylmethylamine), revising the H-1 nmr spectrum of
N-methylethanamine (ethylmethylamine),
proton nmr of N-methylethanamine (ethylmethylamine), ppm chemical shifts of the H-1 nmr spectrum of
N-methylethanamine (ethylmethylamine),
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 N-methylethanamine
(ethylmethylamine), how to work out the
number of chemically different protons in the structure of the
N-methylethanamine (ethylmethylamine) organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of N-methylethanamine (ethylmethylamine) using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of N-methylethanamine (ethylmethylamine) deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of N-methylethanamine
(ethylmethylamine)
examining the 1H nmr spectrum of N-methylethanamine (ethylmethylamine) analysing the 1-H nmr spectrum of
N-methylethanamine (ethylmethylamine)
how do you sketch and interpret the H-1 NMR spectrum of N-methylethanamine
(ethylmethylamine) interpreting interpretation of the 1H proton spin-spin
coupling causing line splitting in the NMR spectrum of N-methylethanamine
(ethylmethylamine)
assignment of chemical shifts in the
proton 1H NMR spectrum of N-methylethanamine (ethylmethylamine) formula
explaining spin-spin coupling for line splitting for N-methylethanamine
(ethylmethylamine) old names
functional group
N-methylethylamine How do you interpret the H-1 NMR spectrum of
N-methylethanamine (ethylmethylamine) How to interpret
the H-1 NMR spectrum of N-methylethanamine (ethylmethylamine) Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the N-methylethanamine
(ethylmethylamine)
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of N-methylethanamine (ethylmethylamine). How to explain the H-1 NMR spectrum of
N-methylethanamine (ethylmethylamine). The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the N-methylethanamine (ethylmethylamine) molecule. How to work out the molecular
structure of the N-methylethanamine (ethylmethylamine) molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the N-methylethanamine
(ethylmethylamine)
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the N-methylethanamine
(ethylmethylamine)
molecule? explaining the spin-spin proton coupling effects in the 1H
NMR spectrum of N-methylethanamine (ethylmethylamine). interpretation
diagram explaining the proton splitting pattern produced from the
n+1 rule and the theoretical ratio of chemical shift
δ and values of
intensities for the proton NMR spectrum lines of N-methylethanamine
(ethylmethylamine)
Links associated
with
N-methylethanamine (ethylmethylamine)
The infrared spectra
of N-methylethylamine (N-methylethanamine, ethylmethylamine)
The mass
spectra of N-methylethylamine (N-methylethanamine,
ethylmethylamine)
The C-13 NMR
spectra of N-methylethylamine (N-methylethanamine,
ethylmethylamine)
The chemistry of ORGANIC NITROGEN COMPOUNDS revision notes INDEX
H-1 proton NMR spectroscopy index
(Please
read 8 points at the top of the 1H NMR index page)
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