[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 13C NMR spectrum of 2,3-dimethylbutane [updated October 31st 2025]

 email doc brown  Re-edit (CH₃)₂CHCH(CH₃)₂

Introductory note on the 13C NMR spectrum of 2,3-dimethylbutane

Students and teachers please note that my explanation of the carbon-13 NMR spectrum of 2,3-dimethylbutane is designed for advanced, but pre-university, chemistry courses.

The description does not involve the chemical shift δ spin-spin coupling effects for 2,3-dimethylbutane and the relative size of the carbon-13 NMR shifts does not give the ratio of the carbon atoms in the different non-equivalent chemical environments of the 2,3-dimethylbutane molecule.

The most common solvent used for investigating the C13 NMR spectrum of compounds like 2,3-dimethylbutane, is CDCl₃ and other deuterated solvents.

2,3-dimethylbutane C₆H₁₄  , ,

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

Key points about the ¹³C NMR Spectrum of 2,3-Dimethylbutane

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

Total carbon atoms: 6, but only 2 signals due to symmetry.

The ¹³C NMR spectrum of 2,3-dimethylbutane shows only two signals due to its high symmetry: one for the four equivalent methyl (CH₃) carbons and one for the two equivalent methine (CH) carbons.

Key Features of the ¹³C NMR Spectrum of 2,3-Dimethylbutane

2,3-Dimethylbutane (C₆H₁₄) is a highly symmetrical branched alkane. Despite having six carbon atoms, its ¹³C NMR spectrum shows only two distinct signals because:

• Four CH₃ groups are chemically equivalent.
• Two central CH groups are also equivalent.
• No CH₂ groups are present in the molecule.

This makes it an excellent example for teaching chemical equivalence and symmetry in NMR.

Carbon-13 Chemical Shifts Table

Common Misconceptions in Exams

• Expecting six signals for six carbons: Symmetry reduces the number of observed signals.
• Confusing CH₃ and CH signals: CH₃ carbons are more shielded (lower ppm); CH carbons appear slightly downfield (higher ppm).
• Assuming more signals means more atoms: Signal count reflects unique environments, not atom count.
• Overlooking quaternary carbons: While not present here, quaternary (C with no H) carbons often give weaker signals.

Exam Revision Tips

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

• Count environments, not atoms: Use symmetry to predict the number of signals.
• Use symmetry to predict signal count: Fewer signals can indicate high symmetry.
•  Memorize typical alkane shifts:
  • CH₃: ~10–15 ppm
  • CH₂: ~20–40 ppm
  • CH: ~25–50 ppm
•  Practice drawing and labeling environments: Helps visualize equivalence or non-equivalence.
•  Compare isomers: ¹³C NMR is powerful for distinguishing between hexane, 2-methylpentane, and 2,3-dimethylbutane.
•  Link to ¹H NMR and mass spectrometry: Use all spectra together for full structural elucidation.

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.

Key words & phrases: Interpreting the C-13 NMR spectra of 2,3-dimethylbutane, C-13 nmr spectrum of 2,3-dimethylbutane, understanding the carbon-13 nmr spectrum of 2,3-dimethylbutane, explaining the line pattern in the high resolution C-13 nmr spectra of 2,3-dimethylbutane, revising the C-13 nmr spectrum of 2,3-dimethylbutane, ppm chemical shifts of the C-13 nmr spectrum of 2,3-dimethylbutane, how to construct the diagram of the C-13 nmr spectrum of 2,3-dimethylbutane, how to analyse the chemical shifts in the carbon-13 NMR spectrum of 2,3-dimethylbutane deducing the chemical environment of all the carbon atoms in 2,3-dimethylbutane examining the c13 nmr spectrum of  2,3-dimethylbutane analysing the 13-c nmr spectrum of 2,3-dimethylbutane how do you sketch and interpret the C-13 NMR spectrum of 2,3-dimethylbutane interpreting interpretation of the C-13 NMR spectrum of 2,3-dimethylbutane Molecular structure diagram of the carbon-13 NMR diagram for the 13C NMR spectrum of 2,3-dimethylbutane. Deducing the number of different chemical environments of the carbon atoms in the 2,3-dimethylbutane molecule from the 13C chemical shifts in the carbon-13 NMR spectrum of 2,3-dimethylbutane. Revision notes on the carbon-13 NMR spectrum of 2,3-dimethylbutane. Matching and deducing the structure of the 2,3-dimethylbutane molecule from its 13C NMR spectrum. Carbon-13 NMR spectroscopy of  aliphatic alkanes, 13C NMR spectra of 2,3-dimethylbutane, a structural isomer of molecular formula C6H14 How do you interpret the chemical shifts of the C-13 NMR spectrum of  2,3-dimethylbutane How to interpret the C-13 NMR spectrum of  2,3-dimethylbutane Explanatory diagram of the 13C C-13 carbon-13 NMR spectrum of the  number of different carbon atom environments in the  2,3-dimethylbutane molecule from its carbon-13 NMR spectrum to help work out the molecular structure of the  2,3-dimethylbutane molecule? The uses and distinctive features of the carbon-13 NMR spectrum of the  2,3-dimethylbutane molecule explained. What do the number and values of the chemical shifts from the c-13 carbon-13 NMR spectrum tell us about the  2,3-dimethylbutane molecule? explaining the decoupled carbon-13 NMR spectrum of  2,3-dimethylbutane  with a detailed interpretation diagram of all the C-13 chemical shifts and intensities

---

The chemistry of ALKANES revision notes INDEX

The infrared spectrum of 2,3-dimethylbutane

The mass spectrum of 2,3-dimethylbutane

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

C-13 NMR spectroscopy index

ALL SPECTROSCOPY INDEXES

All Advanced Organic Chemistry Notes

Use My Google search site box

Email doc b: chem55555@hotmail.com