Advanced Organic Chemistry: 1H NMR spectrum of 2-methylpropan-1-ol (CH3)2CHCH2OH

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Interpreting the 1H 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 1H NMR spectrum of 2-methylpropan-1-ol [updated October 16th 2025]

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 H-1 proton NMR spectroscopy - spectra index

Introductory note on the 1H NMR spectra of 2-methylpropan-1-ol

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

The chemical shift δ splitting pattern effects for 2-methylpropan-1-ol 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-methylpropan-1-ol 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-methylpropan-1-ol molecule.

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

low/high resolution 1H proton nmr spectrum of 2-methylpropan-1-ol C4H10O (CH3)2CHCH2OH analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for isobutyl alcohol explaining spin-spin coupling for line splitting doc brown's advanced organic chemistry revision notes

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 resonances, called chemical shifts, are measured with respect to the TMS, and depend on the individual (electronic) chemical environment of the hydrogen atoms in an organic molecule - 2-methylpropan-1-ol here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of 2-methylpropan-1-ol 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-methylpropan-1-ol molecule.

2-methylpropan-1-ol  C4H10O  (CH3)2CHCH2OH alcohols 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

Interpreting the H-1 NMR spectrum of 2-methylpropan-1-ol

In terms of spin-spin coupling from the possible proton magnetic orientations, for 2-methylpropan-1-ol I have only considered the interactions of non-equivalent protons on adjacent carbon atoms e.g. -CH2-CH3, -CH-CH3- protons etc. (problems with -OH proton resonance)

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

The hydrogen atoms (protons) of 2-methylpropan-1-ol occupy 4 different chemical environments so that the low resolution NMR spectra should show 4 principal peaks of different H-1 NMR chemical shifts (diagram above for 2-methylpropan-1-ol).

(CH3)2CHCH2OH

Note the proton ratio 6:1:2:1 of the 4 colours of the protons in the 4 chemically different environments

Chemical shifts (a) to (d) on the H-1 NMR spectrum diagram for 2-methylpropan-1-ol.

Although there are 10 hydrogen atoms in the molecule, there are only 4 possible different chemical environments for the hydrogen atoms in 2-methylpropan-1-ol molecule.

The integrated signal proton ratio 6:1:2:1 observed in the high resolution H-1 NMR spectrum, corresponds with the structural formula of 2-methylpropan-1-ol.

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

All low and high resolution spectra of 2-methylpropan-1-ol show 4 groups of proton resonances and in the 4 ratio expected from the formula of 2-methylpropan-1-ol.

The ppm quoted on the diagram represent the peak of resonance intensity for a particular proton group in the molecule of 2-methylpropan-1-ol - 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-methylpropan-1-ol below.

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

BUT ...

an important note about the hydroxyl group on 2-methylpropan-2-ol (for pre-university students):

Unless the alcohol is completely free of water (difficult), the hydrogen on the -O-H hydroxyl group and any hydrogens on the adjacent carbon don't interact to produce any spin-spin splitting. Therefore the -OH peak shows up as a singlet and you don't usually have to consider its effect on any hydrogen atoms, if present on the adjacent carbon atom (C-OH), and, neither do you have to consider the splitting effect of adjacent C-H protons on the hydrogen of the OH group.

(a) 1H Chemical shift ppm 0.92 ppm for the methyl protons: (CH3)2CHCH2OH

This 1H resonance is split into a 1:1 doublet by the adjacent CH proton (n+1 = 2).

Evidence for the presence of a CH group in the molecule of 2-methylpropan-1-ol.

The six protons of the two methyl groups in 2-methylpropan-1-ol are all equivalent to each other, so they exhibit the same chemical shift a (0.92 ppm), because the inhabit the same chemical environment.

(b) 1H Chemical shift 1.75 ppm for the CH proton: (CH3)2CHCH2OH

This 1H resonance is split into a nonet by the adjacent CH2 and 2 x CH3 protons (n+8 = 9).

Evidence for the presence of a (CH3)2CHCH2 grouping in the molecule of 2-methylpropan-1-ol

(c) 1H Chemical shift 3.39 ppm for the CH2 protons : (CH3)2CHCH2OH

This 1H resonance is split into a 1:1 doublet by the adjacent CH proton (n+1 = 2).

Evidence for the presence of a CH group in the molecule of 2-methylpropan-1-ol.

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

(d) 1H Chemical shift 2.07 ppm for the hydroxyl proton: (CH3)2CHCH2OH

This proton resonance is not split, and neither does this proton cause field splitting in the CH2 protons.

EXTRA NOTE on why the OH proton chemical shift is usually observed as a singlet in alcohols like 2-methylpropan-1-ol and how deuterium oxide can be used to identify the peak caused by the hydroxyl proton

Although extremely weak acids, there is constant exchanging of protons between alcohol molecules (R = alkyl groups of 2-methylpropan-1-ol).

R-O-H  +  H-O-R    R-O-H  +  H-O-R

The rate of proton transfer is increased by traces of water.

R-O-H  +  H-O-H    R-O-H  +  H-O-H

This cannot happen with the non-acidic C-H protons of alkyl groups in alcohols like 2-methylpropan-1-ol.

This rapid proton transfer interferes with the field splitting effects of the hydroxyl O-H protons and carbon C-H protons and the spin-spin coupling effects disappear.

This phenomena can be used to identify the O-H proton resonance from other C-H proton resonances in hydroxyl molecules like 2-methylpropan-1-ol.

If deuterium oxide (D2O, where D = 2H) is added to the NMR sample, the 1H protons are rapidly replaced by 2H protons in the 2-methylpropan-1-ol molecule.

R-O-H  +  D-O-D    R-O-D  +  H-O-D

The 2H chemical shift frequency is different to the 1H chemical shift frequency, so the effect of D2O is to remove the chemical shift for the OH proton from the 1H NMR spectrum of 2-methylpropan-1-ol, thereby identifying the original 1H chemical shift as belonging to the hydroxyl group O-H proton and not a C-H proton of the 2-methylpropan-1-ol molecule.

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

The ¹H NMR spectrum of 2-methylpropan-1-ol (isobutyl alcohol) shows four distinct proton environments: a broad singlet for the –OH proton, a doublet for the methyl group, a multiplet for the methylene group, and a septet for the methine proton.

These signals confirm the branched alcohol structure.

Key Proton Environments in 2-Methylpropan-1-ol

Chemical Shift (δ, ppm) Proton Type Environment Integration Multiplicity
~3.4, 3.39 ppm CH2–OH Methylene next to –OH (C1) 2H Multiplet
~2.1, 2.07 ppm OH Hydroxyl proton 1H Broad singlet
~1.75, 1.75 ppm CH Methine (C2, attached to CH3 and CH2) 1H Septet
~0.9, 0.92 ppm CH3 Methyl groups (C3 and C4, equivalent) 6H Doublet

Sources: ChemicalBook NMR spectrum

Common Misconceptions for 1H NMR spectra like that of 2-methylpropan-1-ol

  • Mistaking the OH proton for a CH signal: The OH proton appears as a broad singlet and may exchange with D2O, disappearing in deuterated solvents.
  • Assuming all methyl groups are distinct: In 2-methylpropan-1-ol, the two methyl groups are equivalent due to symmetry.
  • Ignoring coupling patterns: The methine proton (CH) shows a septet due to coupling with six equivalent methyl protons (3H × 2).

Exam Revision Tips for questions involving 1H NMR spectra like that of 2-methylpropan-1-ol

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

  • Use integration to count protons: Total integration should match the molecular formula C4H10O (10 protons).
  • Apply the n+1 rule: Predict multiplicity based on adjacent protons:
    • CH3 next to CH → doublet
    • CH next to CH2 ×2 → septet
    • CH2 next to OH and CH → multiplet
  • Recognise exchangeable protons: OH protons may broaden or disappear—use D2O shake test if available.
  • Draw and label: Sketch the molecule and assign each proton environment.
  • Compare with isomers: Practice distinguishing 1-butanol, 2-butanol, and tert-butanol by their NMR patterns.
  • Link to IR and MS: Exams often require multi-spectral interpretation for full structural analysis.

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) and applied to the 1H NMR spectrum of 2-methylpropan-1-ol.
Number of directly adjacent protons 1H causing splitting Splitting pattern produced from the n+1 rule on spin-spin coupling 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

Key words & phrases: C4H10O (CH3)2CHCH2OH  Interpreting the proton H-1 NMR spectra of 2-methylpropan-1-ol, low resolution & high resolution proton nmr spectra of 2-methylpropan-1-ol, H-1 nmr spectrum of 2-methylpropan-1-ol, understanding the hydrogen-1 nmr spectrum of 2-methylpropan-1-ol, explaining the line splitting patterns from spin-spin coupling  in the high resolution H-1 nmr spectra of 2-methylpropan-1-ol, revising the H-1 nmr spectrum of 2-methylpropan-1-ol, proton nmr of 2-methylpropan-1-ol, ppm chemical shifts of the H-1 nmr spectrum of 2-methylpropan-1-ol, 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-methylpropan-1-ol, how to work out the number of chemically different protons in the structure of the 2-methylpropan-1-ol organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 2-methylpropan-1-ol using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of 2-methylpropan-1-ol deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 2-methylpropan-1-ol examining the 1H nmr spectrum of  2-methylpropan-1-ol analysing the 1-H nmr spectrum of 2-methylpropan-1-ol how do you sketch and interpret the H-1 NMR spectrum of 2-methylpropan-1-ol interpreting interpretation of the 1H proton spin-spin coupling causing line splitting in the NMR spectrum of 2-methylpropan-1-ol  assignment of chemical shifts in the proton 1H NMR spectrum of 2-methylpropan-1-ol formula explaining spin-spin coupling for line splitting for isobutyl alcohol How do you interpret the H-1 NMR spectrum of 2-methylpropan-1-ol How to interpret the H-1 NMR spectrum of 2-methylpropan-1-ol Explanatory diagram of the chemical shifts of the 1H H-1 proton NMR spectrum of the 2-methylpropan-1-ol molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the proton NMR spectrum of 2-methylpropan-1-ol. How to explain the H-1 NMR spectrum of 2-methylpropan-1-ol. The chemical shifts and  integrated values of the proton ratios in the 1-H NMR spectrum of the 2-methylpropan-1-ol molecule. How to work out the molecular structure of the 2-methylpropan-1-ol molecule from its proton NMR spectrum. The uses and distinctive features of the proton NMR spectrum of the 2-methylpropan-1-ol molecule explained. What does the H-1 proton NMR spectrum chemical shifts tell us about the structure and properties of the 2-methylpropan-1-ol molecule? explaining the spin-spin proton coupling effects in the 1H NMR spectrum of 2-methylpropan-1-ol. 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-methylpropan-1-ol

Links associated with 2-methylpropan-1-ol

The infrared spectrum of 2-methylpropan-1-ol

The mass spectrum of 2-methylpropan-1-ol

The C-13 NMR spectrum of 2-methylpropan-1-ol

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