Advanced Organic Chemistry: Carbon-13 NMR spectrum of 2,2,3-trimethylbutane (CH3)2CHC(CH3)3 HOME PAGE * SEARCH * GCSE Level Chemistry age ~14-16 * Advanced Level Chemistry age ~16-19
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Interpreting the 13C NMR spectrum of 2,2,3-trimethylbutane [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 & AP honors chemistry courses: Molecular spectroscopy - analysing 13C NMR spectrum of 2,2,3-trimethylbutane [spectra updated Mar 19th 2026 *] Re-edit 13C NMR spectrum of (CH3)3CCH(CH3)2This is a BIG website, PLEASE take time to explore it Links associated with 2,2,3-trimethylbutane C-13 NMR spectroscopy - spectra index * [privacy, cookies & disclaimer policies] See also comparing the 1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16 Introductory note on the 13C NMR spectrum of 2,2,3-trimethylbutane
2,2,3-trimethylbutane C7H16
For more see The molecular structure, classification and naming of alkanes
Key points about the 13C NMR spectrum of 2,2,3-trimethylbutane and a practice question
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| Chemical Shift (δ, ppm) | Carbon Type | Environment | Notes |
|---|---|---|---|
| ~8–10?, 27.2 ppm | CH3 (methyl) | 3× methyl groups on C2 (tertiary carbon) | Equivalent due to symmetry |
| ~11–13, 17.9 ppm | CH3 (methyl) | 2× methyl groups on C3 (secondary carbon) | Slightly different environment |
| ~27–30, 37.7 ppm | CH (methine) | Central carbon at C3 | Deshielded due to branching |
| ~35–38, 32.7 ppm | C (quaternary) | Central C2 bonded to three methyls | Most deshielded due to no H and high substitution |
Total signals = 4
No splitting in standard ¹³C NMR (proton-decoupled) — all signals appear as singletsSource: https://sdbs.db.aist.go.jp/ diagram 13C δ ppm spectral database of organic compounds
Common Misconceptions
| Misconception | Clarification |
|---|---|
| "Each carbon gives a separate peak" | Only if they’re in distinct environments — symmetry reduces the number of signals |
| "All methyl carbons are equivalent" | Not true — methyls on tertiary versus secondary carbons differ in chemical shift |
| "13C NMR shows splitting like 1H NMR" | Standard ¹³C spectra are proton-decoupled — no splitting is observed |
| "More peaks = more atoms" | Peak count reflects unique environments, not atom count |
Exam Revision Tips
- Count environments, not atoms: Use symmetry and bonding to identify equivalent carbons.
- Chemical shift ranges:
- CH3: ~8–20 ppm
- CH2: ~20–40 ppm
- CH: ~25–50 ppm
- Quaternary C: ~30–50 ppm (often more deshielded)
- Use with ¹H NMR: ¹³C NMR complements proton NMR — helps confirm carbon skeleton.
- Compare isomers: Isomers show different numbers of peaks and shifts — useful in structure elucidation.
Tips for spotting equivalent methyl group carbons in 13C NMR
- 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 (like in 2,2-dimethylpentane) can lead to equivalence.
- Use integration clues: If two methyl groups give a single peak with integration of 6H, that’s a strong hint they’re equivalent.
- Compare with isomers: Try contrasting 2,2,3-trimethylbutane with 3,3-dimethylpentane with 2,2-dimethylpentane with 3-methylhexane, where methyl carbon environments differ more clearly.
- Counting methyls as separate signals: Leads to overestimating the number of peaks in ¹³C 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.
Practice Question
Q:
The ¹³C NMR spectrum of a hydrocarbon shows four singlets at δ = 9 ppm, 12 ppm,
28 ppm, and 36 ppm.
Which of the following is the most likely identity of the compound?
- Heptane
- 2,2,3-Trimethylbutane
- 3-Methylhexane
- Cycloheptane
Model Answer
Correct answer: B. 2,2,3-Trimethylbutane
Justification:
- Four signals → matches four distinct carbon environments due to partial symmetry
- Chemical shifts → consistent with methyls (~9 & ~12 ppm), methine (~28 ppm), and quaternary carbon (~36 ppm)
- Other options would show more signals due to less symmetry and more varied environments
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Comparing the 1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16 You can distinguish all 9 isomers from a data combination of their number of 1H NMR chemical shifts, and their resulting integrated 1H proton ratios, plus, their number of 13C chemical shifts. |
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| Name of the alkane structural isomer of molecular formula C7H16 | Abbreviated structural formulae of the nine isomers of molecular formula C7H16 (interpretation complications with 3-methylhexane and 2,3-dimethylpentane because they exhibit R/S isomerism due to a chiral carbon) | Skeletal formula of the nine alkane isomers of molecular formula C7H16 | Number of 1H NMR chemical shifts (δ) and proton ratio (links to spectrum) | Number of 13C chemical shifts (δ) (links to spectrum) |
| heptane |
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4 δ: proton ratio: 3:2:2:1 (6:4:4:2 in the molecule) | 4 δ shifts |
| 2-methylhexane |
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6 δ: proton ratio : 6:3:2:2:2:1 | 6 δ shifts |
| 3-methylhexane |
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7 δ: proton ratio: 3:3:3:2:2:2:1 (simplification) ! | 7 δ shifts |
| 3-ethylpentane |
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3 δ: proton ratio: 9:6:1 | 3 δ shifts |
| 2,2-dimethylpentane |
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4 δ: proton ratio: 9:3:2:2 | 5 δ shifts |
| 2,3-dimethylpentane |
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6 δ: proton ratio: 6:3:3:2:1:1 (simplification) ! | 6 δ shifts (simplification) !!! |
| 2,4-dimethylpentane |
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3 δ: proton ratio: 12:2:2 | 3 δ shifts |
| 3,3-dimethylpentane |
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3 δ: proton ratio: 3:3:2 (6:4:4 in the molecule) | 4 δ shifts |
| 2,2,3-trimethylbutane |
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3 δ: proton ratio: 9:6:1 | 4 δ shifts |
Key words & phrases: C7H16 Interpreting the C-13 NMR spectra of 2,2,3-trimethylbutane, C-13 nmr spectrum of 2,2,3-trimethylbutane, understanding the carbon-13 nmr spectrum of 2,2,3-trimethylbutane, explaining the line pattern in the high resolution C-13 nmr spectra of 2,2,3-trimethylbutane, revising the C-13 nmr spectrum of 2,2,3-trimethylbutane, ppm chemical shifts of the C-13 nmr spectrum of 2,2,3-trimethylbutane, how to construct the diagram of the C-13 nmr spectrum of 2,2,3-trimethylbutane, how to analyse the chemical shifts in the carbon-13 NMR spectrum of 2,2,3-trimethylbutane deducing the chemical environment of all the carbon atoms in 2,2,3-trimethylbutane examining the c13 nmr spectrum of 2,2,3-trimethylbutane analysing the 13-c nmr spectrum of 2,2,3-trimethylbutane how do you sketch and interpret the C-13 NMR spectrum of 2,2,3-trimethylbutane interpreting interpretation of the C-13 NMR spectrum of 2,2,3-trimethylbutane 13C NMR spectrum of 2,2,3-trimethylbutane (CH3)3CCH(CH3)2 (H3C)3CCH(CH3)2 Molecular structure diagram of the carbon-13 NMR diagram for the 13C NMR spectrum of 2,2,3-trimethylbutane. Deducing the number of different chemical environments of the carbon atoms in the 2,2,3-trimethylbutane molecule from the 13C chemical shifts in the carbon-13 NMR spectrum of 2,2,3-trimethylbutane. Revision notes on the carbon-13 NMR spectrum of 2,2,3-trimethylbutane. Matching and deducing the structure of the 2,2,3-trimethylbutane molecule from its 13C NMR spectrum. Carbon-13 NMR spectroscopy of aliphatic alkanes, 13C NMR spectra of 2,2,3-trimethylbutane, a structural isomer of molecular formula C7H16 How do you interpret the chemical shifts of the C-13 NMR spectrum of 2,2,3-trimethylbutane How to interpret the C-13 NMR spectrum of 2,2,3-trimethylbutane Explanatory diagram of the 13C C-13 carbon-13 NMR spectrum of the number of different carbon atom environments in the 2,2,3-trimethylbutane molecule from its carbon-13 NMR spectrum to help work out the molecular structure of the 2,2,3-trimethylbutane molecule? The uses and distinctive features of the carbon-13 NMR spectrum of the 2,2,3-trimethylbutane molecule explained. What do the number and values of the chemical shifts from the c-13 carbon-13 NMR spectrum tell us about the 2,2,3-trimethylbutane molecule? explaining the decoupled carbon-13 NMR spectrum of 2,2,3-trimethylbutane with a detailed interpretation diagram of all the C-13 chemical shifts and intensities
Links associated with 2,2,3-trimethylbutane
The infrared spectrum of 2,2,3-trimethylbutane
The mass spectrum of 2,2,3-trimethylbutane
All Advanced Organic Chemistry Notes
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