1H proton nmr spectrum of methylamine CH5N CH3NH2 low/high resolution analysis interpretation of chemical shifts ppm spin spin line splitting H-1 methylamine 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 methylamine (methanamine) CH₃NH₂

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Interpreting and explaining the H-1 hydrogen-1 (proton) NMR spectrum of methylamine

[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 methylamine (methanamine) [spectra page updated April 4th 2026 *]

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H-1 proton NMR spectroscopy - spectra index

Introductory note on the 1H NMR spectra of methanamine (methylamine)

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

The chemical shift δ splitting pattern effects for methanamine (methylamine) 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 methanamine (methylamine) 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 methanamine (methylamine) molecule.

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

1H proton nmr spectrum of methylamine low/high resolution diagrams CH5N CH3NH2 analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for methylamine 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 - methylamine here.

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

Methylamine CH₅N

The classification, structure and naming of organic nitrogen compounds

Interpreting the H-1 NMR spectrum of methylamine

In terms of spin-spin coupling from the possible proton magnetic orientations, for methylamine I have only considered the interactions of non-equivalent protons on adjacent carbon atoms, BUT this doesn't apply to methylamine.

For relatively simple molecules, the low resolution H-1 NMR spectrum of methylamine is not a good starting point (low resolution diagram above) because both proton resonances have a similar chemical shift of ~2.4 ppm.

CH₃NH₂

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

Theoretically, only two ¹H chemical shifts (a) to (b) on the H-1 NMR spectrum diagram for methylamine.

Although there are 5 hydrogen atoms in the molecule, there are only 2 possible different chemical environments for the hydrogen atoms in methylamine molecule.

The high resolution 1H NMR spectrum of methylamine

In the case of some amines applying the n+1 rule is sometimes not applicable because unless the amine is ultra-pure, the N-H proton resonance is not split by adjacent alkyl group protons and neither are the adjacent alkyl proton resonance split by the N-H protons.

(a) ¹H Chemical shift ~2.4 ppm, methyl group protons: CH₃NH₂

A singlet, assuming no splitting of the resonance due to the amine group protons.

(b) ¹H Chemical shift ~2.4 ppm, amine group protons: CH₃NH₂

A singlet, assuming no splitting of the resonance due to the methyl group protons.

So what you observe is a singlet, which is actually two singlet ¹H resonances close together.

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 - even trace of water catalyses this effect.

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 methanamine (methylamine).

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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