Advanced Organic Chemistry: Infrared 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 infrared 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 infrared spectrum of 2,2,3-trimethyl butane [spectra updated Mar 19th 2026 *] Re-edit infrared spectrum of (CH3)3CCH(CH3)2This is a BIG website, PLEASE take time to explore it Links associated with 2,2,3-trimethylbutane Infrared 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 infrared 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 infrared spectrum of 2,2,3-trimethylbutane and a practice question
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| Wavenumber (cm⁻¹) | Bond Type | Vibration Mode | Notes |
|---|---|---|---|
| ~2950–2850 | C–H (sp³) stretch | Asymmetric & symmetric | Strong, broad region typical of alkanes |
| ~1470–1450 | C–H bending (scissoring) | Medium intensity | Often appears as a pair of peaks |
| ~1380–1365 | C–H bending (methyl symmetric deformation) | Medium–strong | Characteristic of –CH3 groups |
| ~720 | C–H rocking (long-chain methylene) | Weak–medium | May be weak or absent in branched alkanes |
No absorption above 3000 cm⁻¹ (no =C–H or O–H), and no strong peaks in the fingerprint region from polar groups.
Common Misconceptions
| Misconception | Clarification |
|---|---|
| "All organic molecules show strong IR peaks" | Not true—saturated hydrocarbons like 2,2,3-trimethylbutane show only weak-to-moderate C–H features |
| "Fingerprint region always helps identify the molecule" | For simple alkanes, the fingerprint region is not very diagnostic |
| "No peaks = no molecule" | A lack of strong peaks (e.g. no O–H, C=O) doesn't mean no molecule—just that it's non-polar or lacks IR-active groups |
Exam Revision Tips
- Know what’s absent: For alkanes like 2,2,3-trimethylbutane, the absence of O–H (~3300 cm⁻¹), C=O (~1700 cm⁻¹), C=C (~1620-1680 cm⁻¹) or C≡C/C≡N (~2100–2260 cm⁻¹) is as important as what’s present.
- Focus on C–H stretches: Recognize the 2950–2850 cm⁻¹ region as typical of saturated hydrocarbons.
- Compare spectra: Be ready to distinguish between alkanes, alkenes, alcohols, and ketones based on key peaks.
- Use IR with other data: IR alone won’t distinguish between isomers—combine with NMR or MS in multi-technique questions.
Practice Question
Q:
The IR spectrum of a hydrocarbon shows strong absorptions at 2960 cm⁻¹ and 2870
cm⁻¹, medium peaks at 1465 cm⁻¹ and 1375 cm⁻¹, and no significant absorption
above 3000 cm⁻¹ or around 1700 cm⁻¹.
Which of the following is the most likely identity of the compound?
- 2,2,3-Trimethylbutane
- Cyclohexanone
- 1-Hexene
- Butan-2-ol
Model Answer
Correct answer: A. 2,2,3-Trimethylbutane
Justification:
- 2960 & 2870 cm⁻¹ → C–H stretches of sp³ hybridized carbons (alkane)
- 1465 & 1375 cm⁻¹ → C–H bending (methyl and methylene groups)
- No O–H (~3300 cm⁻¹) → rules out alcohols (D)
- No C=O (~1700 cm⁻¹) → rules out ketones (B)
- No =C–H (~3100 cm⁻¹) or C=C (~1650 cm⁻¹) → rules out alkenes (C)
Thus, the spectrum is consistent with a branched alkane like 2,2,3-trimethylbutane.
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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 image and diagram explaining the infrared spectrum of 2,2,3-trimethylbutane, complete infrared absorption spectrum of 2,2,3-trimethylbutane, comparative spectra of 2,2,3-trimethylbutane, prominent peaks/troughs for identifying functional groups in the infrared spectrum of 2,2,3-trimethylbutane, important wavenumber values in cm-1 for peaks/troughs in the infrared spectrum of 2,2,3-trimethylbutane, revision of infrared spectroscopy of 2,2,3-trimethylbutane, fingerprint region analysis of 2,2,3-trimethylbutane, how to identify 2,2,3-trimethylbutane from its infrared spectrum, identifying organic compounds like 2,2,3-trimethylbutane from their infrared spectrum, how to analyse the absorption bands in the infrared spectrum of 2,2,3-trimethylbutane detection of ? functional groups in the 2,2,3-trimethylbutane molecule example of the infrared spectrum of a molecule like 2,2,3-trimethylbutane with no functional group interpreting interpretation of the infrared spectrum of 2,2,3-trimethylbutane shows presence of no functional group (CH3)3CCH(CH3)2 (H3C)3CCH(CH3)2 Diagram of absorption of wavenumber peaks in the infrared spectrum of 2,2,3-trimethylbutane. Characteristic peak wavenumbers in the infrared spectrum of 2,2,3-trimethylbutane. Finger print identification pattern using the infrared spectrum of 2,2,3-trimethylbutane. Revision notes on the infrared spectrum of 2,2,3-trimethylbutane. Matching and deducing the structure of the 2,2,3-trimethylbutane molecule from its infrared spectrum. Infrared spectroscopy of aliphatic alkanes, infrared spectra of 2,2,3-trimethylbutane, a structural isomer of molecular formula C7H16 How do you interpret the infrared absorption spectrum of 2,2,3-trimethylbutane How to interpret the infrared spectrum of 2,2,3-trimethylbutane Explanatory diagram of the infrared spectrum of the 2,2,3-trimethylbutane molecule in terms of its molecular structure. Listing data of the prominent main wavenumber peaks troughs in the infrared spectrum of 2,2,3-trimethylbutane. How to explain the infrared spectrum of 2,2,3-trimethylbutane. Use of the infrared spectrum of 2,2,3-trimethylbutane, identification of 2,2,3-trimethylbutane from its infrared spectrum - fingerprint wavenumber pattern to identify the 2,2,3-trimethylbutane molecule. The uses of the infrared spectrum of the 2,2,3-trimethylbutane molecule. The distinctive features of the infrared spectrum of the 2,2,3-trimethylbutane molecule explained interpretation diagram explaining the peaks-trough of the transmittance of the infrared spectrum of 2,2,3-trimethylbutane what does the infrared spectrum tell you about the structure and properties of the 2,2,3-trimethylbutane molecule? How is infrared spectrum of 2,2,3-trimethylbutane used to identify 2,2,3-trimethylbutane?
Links associated with 2,2,3-trimethylbutane
The mass spectrum of 2,2,3-trimethylbutane
The H-1 NMR spectrum of 2,2,3-trimethylbutane
The C-13 NMR spectrum of 2,2,3-trimethylbutane
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