1H proton nmr spectrum of ethylamine C2H7N CH3CH2NH2 low/high resolution analysis interpretation of chemical shifts ppm spin spin line splitting H-1 ethanamine 1-H nmr explaining spin-spin coupling for line splitting doc brown's advanced organic chemistry revision notes

Advanced Organic Chemistry: The ¹H NMR spectrum of ethylamine CH₃CH₂NH₂

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Interpreting and explaining the H-1 (proton) NMR spectrum of ethylamine (ethanamine)

[Author © 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 ethylamine [spectra page updated April 3rd 2026 *]

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H-1 proton NMR spectroscopy - spectra index

Introductory note on the 1H NMR spectra of ethylamine

Students and teachers please note my explanation of the proton NMR spectrum of ethylamine is designed for advanced, but pre-university, chemistry courses.

The chemical shift δ splitting pattern effects for ethylamine 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 ethylamine molecule).

It is assumed that the integrated intensities of the ¹H NMR δ chemical shifts give the ratio of the protons in the different non-equivalent chemical environments of the ethylamine molecule.

The most common solvent used for investigating the 1H NMR spectrum of compounds like ethylamine, is CDCl₃ and other deuterated solvents to avoid confusion with a ¹H NMR signal, ²D (²H) has a different NMR chemical shift.

1H proton nmr spectrum of ethylamine low/high resolution diagrams formula analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for ethanamine explaining spin-spin coupling for line splitting doc brown's advanced organic chemistry revision notes

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 - ethylamine here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of ethylamine 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 ethylamine molecule.

Ethylamine (aminoethane, ethanamine), C₂H₇N, , , (c) doc b

The classification, structure and naming of organic nitrogen compounds

Interpreting the H-1 NMR spectrum of ethylamine

In terms of spin-spin coupling from the possible proton magnetic orientations, for ethylamine I have only considered the interactions of non-equivalent protons on adjacent carbon atoms e.g. -CH₂-CH₃ (but see note alter on N-H protons).

For relatively simple molecules, the low resolution H-1 NMR spectrum of ethylamine is a good starting point (low resolution diagram above).

The hydrogen atoms (protons) of ethylamine occupy 3 different chemical environments so that the low resolution NMR spectra should show 3 principal ¹H peaks of different H-1 NMR chemical shifts (diagram above for ethylamine).

CH₃CH₂NH₂

Note the integrated proton ratio 3:2:2 of the 3 colours of the 8 protons in the 3 chemically different proton environments

Chemical shifts (a) to (c) on the H-1 NMR spectrum diagram for ethylamine.

Although there are 7 hydrogen atoms in the molecule, there are only 3 possible different chemical environments for the hydrogen atoms in ethylamine molecule.

The integrated signal proton ratio 3:2:2 observed in the high resolution H-1 NMR spectrum, corresponds with the structural formula of ethylamine.

The high resolution 1H NMR spectrum of ethylamine

The ppm quoted on the diagram represent the peak of resonance intensity for a particular proton group in the molecule of ethylamine - 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 ethylamine below.

So, using the chemical shifts and applying the n+1 rule to ethylamine and make some predictions using some colour coding! (In problem solving you work the other way round!)

(a) ¹H Chemical shift 1.10 ppm, methyl protons: CH₃CH₂NH₂

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 ethylamine

(b) ¹H Chemical shift 2.61 ppm, CH₂ protons: CH₃CH₂NH₂

This resonance is split into a 1:3:3:1 quartet by the adjacent CH₃ protons (n+1 = 4), but not by the N-H protons.

I have assumed the N-H protons do NOT cause splitting (see (c)).

Evidence for the presence of a CH₃ group in the molecule of ethylamine.

Resonances (a) and (b) provide evidence for the ethyl group in ethylamine.

(c) ¹H Chemical shift 1.04 ppm, amine group protons: CH₃CH₂NH₂

This resonance appears as a singlet chemical shift for ethylamine.

I have assumed the adjacent CH₂ group protons do NOT cause splitting of the N-H proton resonance, therefore the amine group proton resonance is not split by the adjacent CH₂ protons, so appears a singlet.

The lack of resonance splitting is due to exchange of protons between the amine group of the amine molecules which inhibits the coupling between amine group protons and any adjacent alky group protons (and vice versa) - even a trace of water catalyses this effect.

e.g. for aliphatic primary/secondary aliphatic amines, if R = H or alkyl

R₂N-H + H-O-H H-R₂N-H⁺ + OH^- R₂N-H + H-O-H

If deuterium oxide (D₂O, where D = ²H) is used as the NMR amine sample solvent, the ¹H protons are rapidly replaced by ²H protons in the ethylamine molecule.

R-N-H₂ + D-O-D R-N-D₂ + H-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 ethylamine, thereby identifying the original ¹H chemical shift as belonging to the amine group N-H protons and not a C-H proton of the ethylamine molecule.

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 ethylamine.

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

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