low/high resolution 1H proton nmr spectrum of methyl ethanoate C3H6O2 CH3COOCH3 analysis interpretation of chemical shifts ppm spin spin line splitting H-1 methyl acetate 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 methyl ethanoate CH₃COOCH₃

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Interpreting and explaining the H-1 (proton) NMR spectrum of methyl ethanoate (methyl acetate)

[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 methyl ethanoate (methyl acetate) [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 methyl ethanoate

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

The chemical shift δ splitting pattern effects for methyl ethanoate 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 methyl ethanoate 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 methyl ethanoate molecule.

The most common solvent used for investigating the 1H NMR spectrum of compounds like methyl ethanoate, 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 methyl ethanoate low/high resolution diagrams C3H6O2 CH3COOCH3 analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for methyl acetate 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 - methyl ethanoate here.

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

methyl ethanoate (methyl acetate), , , ,

The molecular structure and naming of carboxylic acids and derivatives

Interpreting the H-1 NMR spectrum of methyl ethanoate

In terms of spin-spin coupling from the possible proton magnetic orientations, for methyl ethanoate I have only considered the interactions of non-equivalent protons on adjacent carbon atoms BUT this does not apply to methyl ethanoate

The hydrogen atoms (protons) of methyl ethanoate occupy 2 different chemical environments so that the low resolution NMR spectra should show 2 principal ¹H peaks of different H-1 NMR chemical shifts (diagram above for methyl ethanoate).

CH₃COOCH₃

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

Chemical shifts (a) to (b) on the H-1 NMR spectrum diagram for methyl ethanoate.

Although there are 6 hydrogen atoms in the molecule, there are only 2 possible different chemical environments for the hydrogen atoms in methyl ethanoate molecule.

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

The high resolution 1H NMR spectrum of methyl ethanoate

All low and high resolution spectra of methyl ethanoate show 2 groups of proton resonances and in the 1:1 ratio expected from the structural formula of methyl ethanoate.

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

Because there no protons on adjacent carbon atoms, the n+1 rule does not apply to methyl ethanoate.

The two 1H NMR resonances are therefore NOT split by spin - spin coupling and both appear on the spectrum as singlets in the proton ratio 1:1 (because there are to groups of CH3 protons, 3:3 = 1:1).

(a) ¹H Chemical shift 2.05 ppm single for methyl group protons: CH₃COOCH₃

(b) ¹H Chemical shift 3.66 ppm singlet: for methyl group protons: CH₃COOCH₃

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 methyl ethanoate.

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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Links associated with methyl ethanoate

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The mass spectrum of methyl ethanoate (methyl acetate)

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H-1 proton NMR spectroscopy index (Please read 8 points at the top of the ¹H NMR index page)

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