Advanced pre-university organic chemistry: 13C NMR spectrum of 1-bromopropane CH3CH2CH2Br

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Interpreting the 13C NMR spectrum of 1-bromopropane

[Author ©  Dr WP Brown PhD: Doc Brown's advanced level organic chemistry exam revision notes suitable for students of UK A level chemistry courses, IB chemistry & US K12 grade 11, grade 12 and AP honors chemistry courses: Molecular spectroscopy - analysing the C-13 NMR spectrum of 1-bromopropane [updated Mar 11th 2026 *]

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* LINKS associated with 1-bromopropane

* The chemistry of organic halogen compounds

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* C-13 NMR spectroscopy - spectra index

See also the Isomers of molecular formula C3H7X  (where X = F, Cl, Br or I)

Introductory note on the 13C NMR spectrum of 1-bromopropane

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

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

The most common solvent used for investigating the 13C NMR spectrum of compounds like 1-bromopropane, is CDCl3 and other deuterated solvents.

C3H7Br CH3CH2CH2Br C-13 nmr spectrum of 1-bromopropane analysis of chemical shifts ppm interpretation of 13C chemical shifts ppm of n-propyl bromide C13 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 - 1-bromopropane here.

1-bromopropane, C3H7Br, CH3CH2CH2Br, (c) doc b , (c) doc b

The molecular structure and naming of haloalkanes

Interpreting the C-13 NMR spectrum of 1-bromopropane

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

CH3CH2CH2Br

(Note the 3 different colours indicating the 3 different chemical environments of the carbon atoms in 1-bromopropane).

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

Note the decreasing effect on the chemical shift as the carbon atom is further from the more electronegative oxygen atom of 1-bromopropane.

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

Summary of the C-13 NMR spectrum of 1-bromopropane and extra comments

The ¹³C NMR spectrum of 1-bromopropane (CH3CH2CH2Br) with clarity, structure, and exam-ready precision.

Overview of Carbon Environments in 1-Bromopropane

1-bromopropane contains three distinct carbon environments:

  1. CH3 (methyl group at the end)
  2. CH2 (central methylene group)
  3. CH2Br (methylene group bonded to bromine)

Each carbon gives rise to a single peak in the ¹³C NMR spectrum due to their unique electronic environments.

Table of Chemical Shifts and Origins for the C-13 NMR spectrum of 1-bromopropane

Chemical Shift (δ, ppm) Carbon Type Environment Notes
~13–14, 13.0 ppm CH3 Terminal methyl group Most shielded; furthest upfield
~26–27, 26.4 ppm CH2 Central methylene Slightly deshielded by adjacent CH₃ and CH₂Br
~36, 35.8 ppm CH2 Adjacent to Br (CH2Br) Deshielded due to electronegative bromine

CH3CH2CH2Br

These values are consistent with experimental data and typical alkyl halide shifts.

Note: Exact chemical shifts may vary slightly depending on solvent and instrument, but the relative positions and patterns remain consistent.

Common Misconceptions about the C-13 NMR spectrum of 1-bromopropane (see also below)

  • Assuming symmetry reduces the number of signals: Unlike symmetrical molecules like 2-bromopropane, 1-bromopropane has three distinct carbon environments.
  • Expecting downfield shifts >50 ppm: Alkyl bromides don’t push carbon shifts as far downfield as oxygen-containing groups.
  • Confusing CH2Br with CH2OH: CH2Br appears around ~36 ppm, whereas CH2OH typically shifts further downfield (~60 ppm).

Exam Tips for questions involving the C-13 NMR spectrum of 1-bromopropane (see also above)
  • Count unique carbon environments: Use symmetry and bonding context to predict the number of signals.
  • Use electronegativity logic: Carbons bonded to electronegative atoms (like Br) shift downfield.
  • Compare with isomers: 2-bromopropane shows only two signals due to symmetry — a common exam distracter.
  • Don’t overinterpret minor shifts: Focus on relative positions and trends, not exact ppm values.

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Links associated with 1-bromopropane

The infrared spectrum of 1-bromopropane

The mass spectrum of 1-bromopropane (propyl bromide)

The H-1 NMR spectrum of 1-bromopropane

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C-13 NMR spectroscopy index

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