Advanced Organic Chemistry: Carbon-13 NMR spectrum 2-methylpropan-1-ol (CH3)2CHCH2OH

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Interpreting the 13C NMR spectrum of 2-methylpropan-1-ol (isobutyl alcohol)

[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 C-13 NMR spectrum of 2-methylpropan-1-ol [updated October 16th 2025]

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Introductory note on the 13C NMR spectrum of 2-methylpropan-1-ol

Students and teachers please note that my explanation of the carbon-13 NMR spectrum of 2-methylpropan-1-ol is designed for advanced, but pre-university, chemistry courses.

The description does not involve the chemical shift δ spin-spin coupling effects for 2-methylpropan-1-ol 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-methylpropan-1-ol molecule.

The most common solvent used for investigating the C13 NMR spectrum of compounds like 2-methylpropan-1-ol, is CDCl3 and other deuterated solvents.

13C nmr spectrum of 2-methylpropan-1-ol C4H10O (CH3)2CHCH2OH analysis of chemical shifts ppm interpretation of 13C chemical shifts ppm of isobutyl alcohol C-13 13-C nmr doc brown's advanced organic chemistry revision notes 

TMS is the acronym for tetramethylsilane, formula Si(CH3)4, whose 13C atoms are arbitrarily given a chemical shift of 0.0 ppm. This is the 'standard' in 13C NMR spectroscopy and all other 13C resonances, called chemical shifts, are measured with respect to the TMS, and depend on the individual (electronic) chemical environment of the 13C atoms in an organic molecule - 2-methylpropan-1-ol here.

2-methylpropan-1-ol  C4H10O  (CH3)2CHCH2OHalcohols and ether structure and naming (c) doc b    alcohols and ether structure and naming (c) doc b    alcohols and ether structure and naming (c) doc b

The molecular structure and naming of aliphatic alcohols and ethers

The molecular structure and naming of alkanes

Interpreting the C-13 NMR spectrum of 2-methylpropan-1-ol

As you can see from the diagram above there are 3 different chemical shift lines in the C-13 NMR spectrum of 2-methylpropan-1-ol indicating 3 different chemical environments of the 4 carbon atoms of 2-methylpropan-1-ol.

(CH3)2CHCH2OH

(Note the 3 different colours indicating the 3 different chemical environments of the 4 carbon atoms in 2-methylpropan-1-ol).

13C chemical shifts (a) to (c) on the C-13 NMR spectrum diagram for 2-methylpropan-1-ol.

The two carbon atoms of the methyl groups in 2-methylpropan-1-ol are equivalent to each other, so they exhibit the same chemical shift a (19.0 ppm), because the inhabit the same chemical environment.

Note the decreasing effect on the 13C chemical shift as the carbon atom is further from the more electronegative oxygen atom in 2-methylpropan-1-ol.

The carbon-13 NMR spectra provides direct evidence of 3 different carbon atom environments for the 4 carbon atoms in the 2-methylpropan-1-ol molecule, deduced from the presence of 3 different 13C NMR chemical shifts (ppm).

Summary of the 13C NMR spectrum of 2-methylpropan-1-ol (isobutyl alcohol)

The ¹³C NMR spectrum of 2-methylpropan-1-ol (isobutyl alcohol) shows three distinct carbon environments, with chemical shifts between ~10 and ~60 ppm.

These reflect methyl, methylene, methine, and hydroxyl-bearing carbon atoms in a branched primary alcohol.

Key ¹³C NMR Chemical Shifts of 2-Methylpropan-1-ol

Chemical Shift (δ, ppm) Carbon Type Environment Notes
~10–12, 19.0 ppm CH3 Two equivalent methyl groups (C3 & C4) Appear as one signal due to symmetry
~25–28, 30.8 ppm CH Methine carbon (C2, bonded to CH3 ×2 and CH2) Slightly deshielded due to branching
~60–65, 69.8 ppm CH2–OH Methylene carbon (C1, bonded to OH) Deshielded by electronegative O atom, the most downfield due to C–O bond

Source: ChemicalBook ¹³C NMR spectrum of 2-methylpropan-1-ol

Common Misconceptions about 13C NMR spectra like that of 2-methylpropan-2-ol

  • Expecting four signals for four carbons: The two methyl groups are chemically equivalent, giving one signal.
  • Confusing CH2 and C–OH signals: The carbon bonded to OH is more deshielded and appears further downfield.
  • Assuming splitting patterns: ¹³C NMR spectra are typically proton-decoupled, so all signals appear as singlets.

Exam Revision Tips for questions involving 13C NMR spectra like that of 2-methylpropan-2-ol

These tips align with AQA, Edexcel, OCR, WJEC, CCEA, CIE, IB, and US AP Chemistry syllabi:

  • Count unique environments, not atoms: Use symmetry to predict signal count.
  • Know typical shift ranges:
    • Alkyl CH3/CH2/CH: δ = 10–40 ppm
    • C–OH (alcohols): δ = 50–65 ppm
    • C=O (carbonyls): δ = 160–220 ppm
  • Draw and label: Sketch the molecule and assign each carbon to its expected shift.
  • Use DEPT spectra if available: Helps distinguish CH₃, CH₂, and CH signals.
  • Compare with isomers: Practice with 1-butanol, 2-butanol, and tert-butanol to see how branching affects shifts.
  • Combine with ¹H NMR and IR: Exams often require multi-technique analysis.

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Links associated with 2-methylpropan-1-ol

The infrared spectrum of 2-methylpropan-1-ol

The mass spectrum of 2-methylpropan-1-ol

The H-1 NMR spectrum of 2-methylpropan-1-ol

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