butanone low high resolution H-1 proton nmr spectrum of butanone analysis interpretation of chemical shifts ppm spin spin line splitting for 2-butanone butan-2-one doc brown's advanced organic chemistry revision notes

Advanced pre-university organic chemistry: ¹H NMR spectrum of butanone (2-butanone) CH₃CH₂COCH₃

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Interpreting the H-1 (proton) NMR spectrum of butanone (butan-2-one)

[Author © Dr Phil Brown PhD: Doc Brown's advanced level organic chemistry exam revision notes suitable for students of UK A level chemistry courses, IB chemistry & US K12 grade 11, grade 12 and AP honors chemistry courses: Molecular spectroscopy analysis of butanone [updated Mar 20th 2026 *] [privacy policy, cookies & disclaimer]

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Links associated with butanone

H-1 proton NMR spectroscopy - spectra index

See also the Isomers of molecular formula C₄H₈O (M_r = 72)

Introductory note on the 1H NMR spectra of butanone

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

The chemical shift δ splitting pattern effects for butanone 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 butanone 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 butanone molecule.

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

low and high resolution H-1 proton nmr spectrum of butanone analysis interpretation of chemical shifts ppm spin spin line splitting diagram for 2-butanone butan-2-one 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 shifts, called chemical shifts, depend on the individual (electronic) chemical environment of the hydrogen atoms in an organic molecule - butanone here.

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

Butanone C₄H₈O, , , , ketone

The molecular structure and naming of aldehydes and ketones
Interpreting the H-1 NMR spectrum of butanone

For relatively simple molecules, the low resolution H-1 NMR spectrum of butanone is a good starting point.

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

CH₃COCH₂CH₃

(Note the ratio 3:2:3 of the three colours of the protons in the 3 chemically different environments)

Although there are 8 hydrogen atoms in the molecule, there only 3 possible chemical environment for the hydrogen atoms.

The proton ratio observed 3:2:3, corresponds with the structural formula of butanone.

The high resolution spectrum of butanone

So, using the chemical shifts and applying the n+1 rule to CH₃COCH₂CH₃:

(a) The chemical shift at 2.16 ppm is for the 'left' methyl group and no splitting is evident because there s no adjacent proton on a the carbonyl (C=O) carbon atom.

(b) The CH₂ protons are split into a 1:3:3:1 quartet by the 'right-hand' CH₃ group at 2.45 ppm - evidence of a CH₃ group in the molecule.

(c) The 'right-hand' CH₃ protons are split into a 1:2:1 triplet by the CH₂ group at 1.06 ppm - evidence of a CH₂ group in the molecule.

Note that the 'real spectra' intensity ratios e.g. 1:2:1 and 1:3:3:1 are not perfect, but do look something like the theory predicts for butanone!

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).

Number of protons ¹H causing splitting	Splitting pattern produced from the n+1 rule 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 butanone

The infrared spectrum of butanone

The mass spectrum of butanone

The C-13 NMR spectrum of butanal (butyraldehyde)

The chemistry of ALDEHYDES and KETONES 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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