[Author ©  Dr WP 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 spectrum of 2,3-dimethylbutane [updated October 31st 2025]

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Introductory note on the 1H NMR spectra of 2,3-dimethylbutane

Students and teachers please note my explanation of the proton NMR spectrum of 2,3-dimethylbutane is designed for advanced, but pre-university, chemistry courses.

The chemical shift δ splitting pattern effects for 2,3-dimethylbutane 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 2,3-dimethylbutane 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 2,3-dimethylbutane molecule.

The most common solvent used for investigating the 1H NMR spectrum of compounds like 2,3-dimethylbutane, is CDCl₃ and other deuterated solvents to avoid confusion with a ¹H NMR signal, ²D (²H) has a different NMR chemical shift.

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 - 2,3-dimethylbutane here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of 2,3-dimethylbutane 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 2,3-dimethylbutane molecule.

2,3-dimethylbutane C₆H₁₄  , ,

For more see The molecular structure, classification and naming of alkanes

Interpreting the H-1 NMR spectrum of 2,3-dimethylbutane

For relatively simple molecules, the low resolution H-1 NMR spectrum of 2,3-dimethylbutane is a good starting point (low resolution diagram above).

The hydrogen atoms (protons) of 2,3-dimethylbutane occupy only two different chemical environments so that the low resolution NMR spectra should show two peaks of different H-1 NMR chemical shifts (diagram above for 2,3-dimethylbutane).

(CH₃)₂CHCH(CH₃)₂ 

Note the ratio 12:2 (structural formula) = 6:1 (¹H spectrum) integrated ratio of the protons intensities of the protons in the two chemically different environments

Although there are 14 hydrogen atoms in the molecule, there only 2 possible chemical environments for the hydrogen atoms in the very symmetrical 2,3-dimethylbutane molecule.

The integrated signal proton ratio 6:1 observed, corresponds with the structural formula of 2,3-dimethylbutane.

The high resolution H-1 NMR spectrum of 2,3-dimethylbutane

In terms of spin-spin coupling from the possible proton magnetic orientations, for 2,3-dimethylbutane I have only considered the interactions of non-equivalent protons on adjacent carbon atoms

e.g. -CH₂-CH₃, -CH-CH₂- protons etc.

All low and high resolution spectra of 2,3-dimethylbutane show two groups of proton resonances and in the ratio expected from the formula of 2,3-dimethylbutane.

The ppm quoted on the diagram represent the peak of resonance intensity for a particular proton group in the molecule of 2,3-dimethylbutane - 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 2,3-dimethylbutane below.

So, using the chemical shifts and applying the n+1 rule to 2,3-dimethylbutane and make some predictions using some colour coding! (In problem solving you work the other way round!)

δ (a) ¹H Chemical shift 0.84 ppm of the 12 'blue' CH₃ protons (CH₃)₂CHCH(CH₃)₂ 

The CH₃ proton resonance is split into a 1:1 doublet by the adjacent CH protons (n+1 = 2). These 12 protons are all equivalent to each other - all in the same ¹H chemical environment.

Evidence for the presence of a CH group in the molecule of 2,3-dimethylbutane

δ (b) ¹H Chemical shift 1.39 ppm of the CH protons (CH₃)₂CHCH(CH₃)₂ 

At first sight you would think this CH proton resonance is split into an octet of resonance lines by the 2 x CH₃ and CH protons on either side (n+1 = 8).

However, theoretically, these particular pair of CH protons are equivalent to each other due to their central symmetry in the symmetrical 2,3-dimethylbutane molecule and their proton fields should not split each other's ¹H resonance.

These two protons are in the same ¹H chemical environment, but unlike the methyl protons, they are adjacent to each other.

Therefore, theoretically, the CH proton resonance is only split by the methyl protons into a 1:6:15:20:15:6:1 septet.

Key points about the ¹H NMR Spectrum of 2,3-Dimethylbutane

Despite its high symmetry, 2,3-dimethylbutane has two distinct proton environments:

• Four methyl (CH₃) groups: equivalent due to symmetry
• Two central methane (CH) protons: also equivalent

Proton Chemical Shifts (2) and Integration Table (12 : 2)

Chemical Shift (δ, ppm)	Proton Type	Environment	Integration	Multiplicity
~0.90, 0.84 ppm	CH3	Four equivalent methyls	12	Singlet
~1.50, 1.39 ppm	CH	Two equivalent methine CHs	2	Singlet

Total protons: 14. No splitting occurs due to lack of adjacent non-equivalent protons.

Sources: https://sdbs.db.aist.go.jp/ diagram ¹H δ ppm spectral database of organic compounds

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Common Misconceptions in Exams

• Assuming one peak means one environment: Symmetry can mask the true number of atoms.
• Expecting splitting in symmetrical alkanes: No coupling occurs when neighbours are equivalent.
• Miscounting integration: Always match integration to actual proton count (e.g., 12:2, not 12:4).

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Exam Revision Tips

For AQA, Edexcel, OCR, WJEC, CCEA, CIE, IB, and US AP Chemistry:

•  Use symmetry to predict signal count: Fewer signals doesn’t mean fewer atoms.
•  Memorize typical shifts:
  • CH₃: ~0.9 ppm (¹H), ~15 ppm (¹³C)
  • CH: ~1.5 ppm (¹H), ~30 ppm (¹³C)
•  Practice integration analysis: Match peak area to proton count.
•  Compare isomers: Use NMR to distinguish between hexane, 2-methylpentane, and 2,3-dimethylbutane.
•  Link NMR to structure: Combine with IR and MS for full structural elucidation.

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Tips for spotting equivalent methyl group protons in ¹H NMR e.g. 4 methyl groups in 2,2-dimethylbutane

• Check for identical attachments: If two or more methyl groups are bonded to the same carbon and that carbon is not chiral, they are usually equivalent.
• Look for symmetry: Even partial symmetry can lead to equivalence.
• Use integration clues: If two methyl groups give a single peak with integration of 6H (3 gives 9H), that's a strong hint they are equivalent.
• Compare with isomers: Try contrasting with 2,2-dimethylbutane with isomeric 3-methylpentane, where methyl proton environments differ more clearly.

• Counting all methyls as separate signals: Leads to overestimating the number of peaks in ¹H NMR spectra.
• Assuming all methyls are equivalent: Not true in asymmetric or chiral environments.
• Ignoring branching effects: Branching can create or remove equivalence depending on the substitution pattern.

Comparing the infrared, mass, 1H NMR and 13C NMR spectra of the five structural alkane isomers of C6H14 NOTE: The images are linked to their original detailed spectral analysis pages AND can be doubled in size with touch screens to increase the definition to the original hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane and 2,3-dimethylbutane image sizes.  These five molecules are structural isomers of saturated alkanes of molecular formula C6H14 and exemplify the infrared, mass, 1H NMR and 13C NMR spectra of lower aliphatic alkanes (non-cyclic alkanes).
Infrared spectra below.
	INFRARED SPECTRA: Apart from the significant differences in the fingerprint region at wavenumbers 1500 to 400 cm-1, there are no other great striking differences, but each could be identified from its infrared spectrum. All the absorption bands are typical of molecules containing saturated alkyl structure and there are no characteristic infrared absorptions due to a specific functional group.
Infrared spectra above, mass spectra below.

 

Comparing the infrared, mass, 1H NMR and 13C NMR spectra of the five structural alkane isomers of C6H14 NOTE: The images are linked to their original detailed spectral analysis pages AND can be doubled in size with touch screens to increase the definition to the original hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane and 2,3-dimethylbutane image sizes.  These five molecules are structural isomers of saturated alkanes of molecular formula C6H14 and exemplify the infrared, mass, 1H NMR and 13C NMR spectra of lower aliphatic alkanes (non-cyclic alkanes).
Infrared spectra below.
	INFRARED SPECTRA: Apart from the significant differences in the fingerprint region at wavenumbers 1500 to 400 cm-1, there are no other great striking differences, but each could be identified from its infrared spectrum. All the absorption bands are typical of molecules containing saturated alkyl structure and there are no characteristic infrared absorptions due to a specific functional group.
Infrared spectra above, mass spectra below.
	MASS SPECTRA: Base ion peaks plus m/z comments. Hexane: m/z 57, 42 and 56 prominent 2-methylpentane: m/z 43, 42 and 71 prominent 3-methylpentane: m/z 57, 41 and 56 prominent 2,2-dimethylbutane: m/z 43, 41, 57 and 71 prominent 2,3-dimethylbutane: m/z 43, 41, 42 and 71 prominent
Mass spectra above, 1H NMR spectra below.
	1H NMR SPECTRA: They can all be distinguished by their different integrated proton ratios - need very high resolution. Hexane: 3 1H δ shifts, H ratio 3:2:2 (6:4:4 in formula) 2-methylpentane: 5 1H δ shifts, H ratio 6:3:2:2:1 3-methylpentane: 4 1H δ shifts, H ratio 6:4:3:1 2,2-dimethylbutane: 3 1H δ shifts, H ratio 9:3:2 2,3-dimethylbutane: 2 1H δ shifts, H ratio 6:1 (12:2 in formula)
1H NMR spectra above, 13C NMR spectra below.
	13C NMR SPECTRA: From the number of shifts, you can't distinguish (iii) and (iv) but you can distinguish them from (i), (ii) and (v). (i) Hexane: 3 13C δ shifts (ii) 2-methylpentane: 5 13C δ shifts (iii) 3-methylpentane: 4 13C δ shifts (iv) 2,2-dimethylbutane: 4 13C δ shifts (v) 2,3-dimethylbutane: 2 13C δ shifts
13C NMR spectra above.

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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Key words & phrases: Interpreting the proton H-1 NMR spectra of 2,3-dimethylbutane, low resolution & high resolution proton nmr spectra of 2,3-dimethylbutane, H-1 nmr spectrum of 2,3-dimethylbutane, understanding the hydrogen-1 nmr spectrum of 2,3-dimethylbutane, explaining the line splitting patterns in the high resolution H-1 nmr spectra of 2,3-dimethylbutane, revising the H-1 nmr spectrum of 2,3-dimethylbutane, proton nmr of 2,3-dimethylbutane, ppm chemical shifts of the H-1 nmr spectrum of 2,3-dimethylbutane, 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 2,3-dimethylbutane, how to work out the number of chemically different protons in the structure of the 2,3-dimethylbutane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 2,3-dimethylbutane using the n+1 rule to explain the spin - spin coupling spin splitting in the proton nmr spectrum of 2,3-dimethylbutane deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 2,3-dimethylbutane examining the 1H nmr spectrum of  2,3-dimethylbutane analysing the 1-H nmr spectrum of 2,3-dimethylbutane how do you sketch and interpret the H-1 NMR spectrum of 2,3-dimethylbutane interpreting interpretation of the H-1 proton NMR spectrum of 2,3-dimethylbutane Molecular structure diagram of the proton NMR diagram for the 1H NMR spectrum of 2,3-dimethylbutane. The proton ratio in the 1H NMR spectrum of 2,3-dimethylbutane. Deducing the number of different chemical environments of the protons in the 2,3-dimethylbutane molecule from the 1H chemical shifts in the hydrogen-1 NMR spectrum of 2,3-dimethylbutane. Analysing the high resolution 1H NMR spectrum of 2,3-dimethylbutane. Analysing the low resolution 1H NMR spectrum of 2,3-dimethylbutane. You may need to know the relative molecular mass of 2,3-dimethylbutane to deduce the molecular formula from the proton ratio of the 1H NMR spectrum of 2,3-dimethylbutane. Revision notes on the proton NMR spectrum of 2,3-dimethylbutane. Matching and deducing the structure of the 2,3-dimethylbutane molecule from its hydrogen-1 NMR spectrum. Proton NMR spectroscopy of  aliphatic alkanes, 1H NMR spectra of 2,3-dimethylbutane, a structural isomer of molecular formula C6H14 How do you interpret the H-1 NMR spectrum of  2,3-dimethylbutane How to interpret the H-1 NMR spectrum of  2,3-dimethylbutane Explanatory diagram of the chemical shifts of the 1H H-1 proton NMR spectrum of the  2,3-dimethylbutane molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the proton NMR spectrum of  2,3-dimethylbutane. How to explain the H-1 NMR spectrum of  2,3-dimethylbutane. The chemical shifts and  integrated values of the proton ratios in the 1-H NMR spectrum of the  2,3-dimethylbutane molecule. How to work out the molecular structure of the  2,3-dimethylbutane molecule from its proton NMR spectrum. The uses and distinctive features of the proton NMR spectrum of the  2,3-dimethylbutane molecule explained. What does the H-1 proton NMR spectrum chemical shifts tell us about the structure and properties of the  2,3-dimethylbutane molecule? explaining the spin-spin proton coupling effects in the 1H NMR spectrum of  2,3-dimethylbutane. interpretation diagram explaining the proton splitting pattern produced from the n+1 rule and the theoretical ratio of chemical shift and values of intensities for the proton NMR spectrum lines of  2,3-dimethylbutane

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Links associated with 2,3-dimethylbutane

The chemistry of ALKANES revision notes INDEX

The infrared spectrum of 2,3-dimethylbutane

The mass spectrum of 2,3-dimethylbutane

The C-13 NMR spectrum of 2,3-dimethylbutane

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

ALL SPECTROSCOPY INDEXES

All Advanced Organic Chemistry Notes

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