ethyl ethanoate low high resolution H-1 proton 1H nmr spectrum of ethyl acetate analysis interpretation of chemical shifts ppm spin spin line splitting doc brown's advanced organic chemistry revision notes

Advanced Organic Chemistry: ¹H NMR spectrum of ethyl ethanoate CH₃COOCH₂CH₃

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Interpreting the 1H NMR spectrum of ethyl ethanoate (ethyl 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, IB chemistry & US K12 grade 11, grade 12 and AP honors chemistry courses: Molecular spectroscopy analysis of ethyl ethanoate [spectrum page updated RE-EDIT]

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H-1 proton NMR spectroscopy - spectra index

Introductory note on the 1H NMR spectrum of ethyl ethanoate

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

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

The most common solvent used for investigating the 1H NMR spectrum of compounds like ethyl ethanoate, 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 ethyl ethanoate analysis interpretation of chemical shifts ppm spin spin line splitting of ethyl acetate diagram 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 - ethyl ethanoate here.

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

Ethyl ethanoate C₄H₈O₂ , , ,

The molecular structure and naming of carboxylic acids and derivatives
Interpreting the H-1 NMR spectrum of ethyl ethanoate

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

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

CH₃COOCH₂CH₃

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

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

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

The high resolution spectrum of ethyl ethanoate

So, using the chemical shifts and applying the n+1 rule to ethyl ethanoate

(a) At 2.04 ppm the 'left-hand' CH₃ protons show no evident splitting shift by adjacent protons

Evidence that one of the CH₃ groups is not joined to another carbon atom with protons - as is the case with the ethyl ethanoate molecule.

The proton ratio in the 1H NMR spectrum allows the deduction of two methyl groups in the molecule.

(b) At 4.10 ppm the CH₂ proton line is split into a 1:3:3:1 quartet by the adjacent methyl group (n+3 = 4).

Evidence that there is indeed another CH₃ group joined to another carbon atom with protons - as is the case with ethyl ethanoate molecule.

(c) At 1.26 ppm the CH₂ protons split the 'right-hand' CH₃ shift into 1:2:1 triplet (n+2 = 3).

Evidence of the CH₂ group in the molecule of ethyl ethanoate

The 1H NMR pattern of chemical shifts can help distinguish isomers of ethyl ethanoate

See also Isomers of molecular formula C₄H₈O₂ for other isomeric structures and brief notes on the 1H NMR chemical shifts.

Practise exam questions based on the 1H NMR spectrum of ethyl ethanoate

Five multiple choice questions with worked out answers an full explanations based on the 1H NMR spectrum of ethyl ethanoate

These questions are an experiment of doc brown using AI to generate practice exam questions based on typical specifications of UK A-level chemistry exam boards - I have checked and re-edited the questions where necessary, if you think there is any error PLEASE email me at chem55555@hotmail.com asap.

I don't mind if students/teachers do a selected printout of these questions and answers.

ANSWERS

1. A peak at around 4.1 ppm appears as a quartet. Which protons does this signal correspond to?

A. The methyl group next to the carbonyl

B. The methyl group at the end of the ethyl chain

C. The methylene group next to the oxygen atom

D. The carbonyl carbon’s proton

2. A triplet at about 1.2 ppm is observed. What causes this splitting pattern?

A. No coupling — it is a singlet misread as a triplet

B. Coupling with three equivalent protons on a CH₃ group

C. Coupling with one proton on a CH group D.

D. Coupling with two equivalent protons on a CH₂ group

3. A singlet at around 2.0 ppm integrates to 3 protons. Which group produces this signal?

A. The methyl group attached directly to the carbonyl

B. The methylene group next to oxygen

C. The terminal methyl group of the ethyl chain

D. The hydroxyl proton

4. How many distinct proton environments appear in the ¹H NMR spectrum of ethyl ethanoate?

A. Two

B. Three

C. Four

D. Five

5. Which combination of chemical shift and splitting pattern uniquely identifies the –OCH2– group in ethyl ethanoate?

A. 1.2 ppm, triplet

B. 2.0 ppm, singlet

C. 4.1 ppm, quartet

D. 7.2 ppm, multiplet

ANSWERS

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

Key words & phrases: proton NMR of ethyl acetate Interpreting the proton H-1 NMR spectra of ethyl ethanoate, low resolution & high resolution proton NMR spectra of ethyl ethanoate, H-1 NMR spectrum of ethyl ethanoate, understanding the hydrogen-1 NMR spectrum of ethyl ethanoate, explaining the line splitting patterns in the high resolution H-1 NMR spectra of ethyl ethanoate, revising the H-1 NMR spectrum of ethyl ethanoate, proton NMR of ethyl ethanoate, ppm chemical shifts of the H-1 NMR spectrum of ethyl ethanoate, 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 ethyl ethanoate, how to work out the number of chemically different protons in the structure of the ethyl ethanoate organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of ethyl ethanoate using the n+1 rule to explain the spin - spin coupling splitting in the proton NMR spectrum of ethyl ethanoate deducing the nature of the protons from the chemical shifts ppm in the H-1 NMR spectrum of ethyl ethanoate explaining the proton 1H NMR spectrum of ethyl ethanoate How do you interpret the H-1 NMR spectrum of ethyl ethanoate How to interpret the H-1 NMR spectrum of ethyl ethanoate Explanatory diagram of the chemical shifts of the 1H H-1 proton NMR spectrum of the ethyl ethanoate molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the proton NMR spectrum of ethyl ethanoate. How to explain the H-1 NMR spectrum of ethyl ethanoate. The chemical shifts and integrated values of the proton ratios in the 1-H NMR spectrum of the ethyl ethanoate molecule. How to work out the molecular structure of the ethyl ethanoate molecule from its proton NMR spectrum. The uses and distinctive features of the proton NMR spectrum of the ethyl ethanoate molecule explained. What does the H-1 proton NMR spectrum chemical shifts tell us about the structure and properties of the ethyl ethanoate molecule? explaining the spin-spin proton coupling effects in the 1H NMR spectrum of ethyl ethanoate. 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 ethyl ethanoate

Links associated with ethyl ethanoate

The infrared spectrum of ethyl ethanoate

The mass spectrum of ethyl ethanoate (ethyl acetate)

The C-13 NMR spectrum of ethyl methanoate (ethyl formate)

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ANSWERS

Five multiple choice questions with worked out answers an full explanations based on the 1H NMR spectrum of ethyl ethanoate

I don't mind if students/teachers do a selected printout of these questions and answers.

Ethyl ethanoate (CH₃COOCH₂CH₃) Key 1H proton chemical environments:

CH₃CO– (singlet, ~2.0 ppm, 3H)
–OCH₂– (quartet, ~4.1 ppm, 2H, methylene group)
–CH₃ (ethyl) (triplet, ~1.2 ppm, 3H)

1. A peak at around 4.1 ppm appears as a quartet. Which protons does this signal correspond to?

A. The methyl group next to the carbonyl

B. The methyl group at the end of the ethyl chain

C. The methylene group next to the oxygen atom

D. The carbonyl carbon’s proton

Correct answer: C — The methylene group next to the oxygen atom

Explanation: Protons on –OCH₂– are strongly deshielded by the electronegative oxygen, giving a shift around 4.1 ppm. They appear as a quartet because they are split by the adjacent CH₃ group (3 protons → quartet).

Common misconception: Students often think the most downfield peak must be the carbonyl‑adjacent CH₃. But oxygen causes far greater deshielding than a carbonyl.

2. A triplet at about 1.2 ppm is observed. What causes this splitting pattern?

A. No coupling — it is a singlet misread as a triplet

B. Coupling with three equivalent protons on a CH₃ group

C. Coupling with one proton on a CH group D.

D. Coupling with two equivalent protons on a CH₂ group

Correct answer: A — Coupling with two equivalent protons on a CH2 group

Explanation: The terminal CH₃ of the ethyl group is split by the adjacent CH₂, giving a triplet (n+1 rule → 2+1 = 3). Chemical shift around 1.2 ppm is typical for an alkyl methyl group.

Common misconception: Students sometimes think a triplet must come from a CH2 group. But splitting depends on neighbouring protons, not the group itself.

3. A singlet at around 2.0 ppm integrates to 3 protons. Which group produces this signal?

A. The methyl group attached directly to the carbonyl

B. The methylene group next to oxygen

C. The terminal methyl group of the ethyl chain

D. The hydroxyl proton

Correct answer: A — The methyl group attached directly to the carbonyl

Explanation: The CH₃CO– group appears as a singlet because it has no neighbouring protons to split it. Its shift (~2.0 ppm) is typical for a methyl group adjacent to a carbonyl.

Common misconception: Students often expect splitting because “everything splits everything”. But the n+1 rule only applies when neighbouring protons exist — here, they do not.

4. How many distinct proton environments appear in the ¹H NMR spectrum of ethyl ethanoate?

A. Two

B. Three

C. Four

D. Five

Correct answer: B — Three

Explanation: Ethyl ethanoate contains three chemically distinct proton environments:

CH₃CO– (3H)
–OCH₂– (2H)
–CH₃ (ethyl) (3H)

Common misconception: Students sometimes count “carbonyl protons” — but carbonyl carbons have no hydrogens.

5. Which combination of chemical shift and splitting pattern uniquely identifies the –OCH2– group in ethyl ethanoate?

A. 1.2 ppm, triplet

B. 2.0 ppm, singlet

C. 4.1 ppm, quartet

D. 7.2 ppm, multiplet

Correct answer: C — 4.1 ppm, quartet

Explanation: The –OCH₂– group is:

strongly deshielded → ~4.1 ppm
split by the adjacent CH₃ → quartet

This combination is the most diagnostic feature of an ester’s ethoxy group.

Common misconception: Students often think “quartet = CH₂ always”, but CH₂ groups can produce many patterns depending on neighbours. Here, the chemical shift is the key clue.