propane low high resolution H-1 proton nmr spectrum of analysis interpretation of chemical shifts ppm spin spin line splitting H1 propane 1-H nmr doc brown's advanced organic chemistry revision notes

Advanced Organic Chemistry: H-1 NMR spectrum of propane CH₃CH₂CH₃

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Interpreting and explaining the H-1 (proton) NMR spectrum of propane

[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 and AP honors chemistry courses: Molecular spectroscopy analysis of propane [spectra page updated Mar 26th 2026 *]

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H-1 proton NMR spectroscopy - spectra index

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Introductory note on the 1H NMR spectra of propane

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

The chemical shift δ splitting pattern effects for propane 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 propane 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 propane molecule.

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

low and high resolution H-1 proton nmr spectrum of propane analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 1-H nmr for propane 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 shifts, called chemical shifts, depend on the individual (electronic) chemical environment of the hydrogen atoms in an organic molecule - propane here.

In terms of spin-spin coupling from the possible proton magnetic orientations, for propane I have only considered the interactions of non-equivalent protons on adjacent carbon atoms e.g. -CH₂-CH₃ protons.

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

Propane C₃H₈, , , , alkane

Interpreting the H-1 NMR spectrum of propane (dissolved in CDCl₃)

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

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

CH₃CH₂CH₃

Note the integrated proton ratio of 6:2 = 3:1 of the two colours of the protons in the two chemically different environments

Although there are 8 hydrogen atoms in the molecule, there only 2 possible chemical environments for the hydrogen atoms in propane molecule.

The overall proton ratio 3:1 (6:2) observed, corresponds with the structural formula of propane.

The high resolution H-1 NMR spectrum of propane

All low and high resolution spectra of propane show two groups of protons and in the ratio 3:1 expected from the formula of propane.

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

So, using the chemical shifts and applying the n+1 rule to propane

Chemical shift δ (a) 0.90 ppm, the two groups of CH₃ protons: CH₃CH₂CH₃

This proton resonance split by the CH₂ protons into a 1:2:1 triplet (n+1 = 3)

Evidence for the presence of a CH₂ group in the molecule of propane

Chemical shift δ (b) 1.34 ppm, the one group of CH₂ protons: CH₃CH₂CH₃

The central CH₂ group protons are split on either side by a group of CH₃ protons (6 protons in total) into a 1:6:15:20:15:6:1 septet (n+1 = 7)

Evidence for the presence of a two CH₃ groups separated by a carbon atom with at least one proton on it in the molecule of propane i.e. CH₃-CH_x-CH₃ grouping.

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 propane.

Number of protons ¹H causing splitting	Splitting pattern produced from the n+1 rule 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

Comparing the infrared, mass, 1H NMR and 13C NMR spectra of propane, cyclopropane and propene NOTE: The images are linked to their original detailed spectral analysis pages AND can be doubled in size with touch screens to increase the definition to the original ethane and ethene image sizes.

	Comparing the infrared spectra of propane, propene and cyclopropane. Cyclopropane and propene are structural isomers of molecular formula C₃H₆. Propane and propene exemplify the infrared spectra of lower members of the alkane and alkene homologous series of C_nH_2n+2 and C_nH_2n hydrocarbon molecules where n = 3.
INFRARED SPECTRA (above): Apart from the significant differences in the fingerprint region at wavenumbers 1500 to 400 cm^-1, the most striking differences are: (i) propene shows the characteristic absorption at ~1700 cm^-1 for the C=C stretching vibrations, absent in the other two spectra, (ii) cyclopropane shows an absorption band at 2200 cm^-1, absent in the other two spectra, (iii) propane has an absorption band at ~750 cm^-1, absent in the other two spectra.

	Comparing the mass spectra of propane, propene and cyclopropane. Cyclopropane and propene are structural isomers of molecular formula C₃H₆. Propane and propene exemplify the mass spectra of lower members of the alkane and alkene homologous series of C_nH_2n+2 and C_nH_2n hydrocarbon molecules where n = 3.
MASS SPECTRA (above): All three hydrocarbons show some similarities in their mass spectra e.g. m/z ions 26 to 28 for [C₂H_x]⁺ (x = 2 to 4) and m/z 14 and 15 ions - but these are found in most aliphatic hydrocarbon spectra. The molecular ion peaks will be the same for the isomeric propene and cyclopropane (m/z 42) but that of propane will be 2 mass units higher at m/z 44. The base ion peak m/z values are all different, propane 29, propene 41 and cyclopropane 42.

	Comparing the 1H proton NMR spectra of propane, propene and cyclopropane. Cyclopropane and propene are structural isomers of molecular formula C₃H₆. Propane and propene exemplify the 1H proton NMR spectra of lower members of the alkane and alkene homologous series of C_nH_2n+2 and C_nH_2n hydrocarbon molecules where n = 3.
1H NMR SPECTRA (above): The 1H NMR spectra of all three molecules give different proton ratios i.e. propane 3:1 (actually 6:2 in the molecule), propene 2:1:3 (spectrum and molecule) and cyclopropane just a singlet for the six protons, so all three can be distinguished from each other by their ¹H NMR spectra..

	Comparing the carbon-13 NMR spectra of propane, propene and cyclopropane. Cyclopropane and propene are structural isomers of molecular formula C₃H₆. Propane and propene exemplify the carbon-13 NMR spectra of lower members of the alkane and alkene homologous series of C_nH_2n+2 and C_nH_2n hydrocarbon molecules where n = 3.
13C NMR SPECTRA (above): The 13C NMR spectra of the three molecules show different numbers of carbon-13 chemical environments i.e propane 2, propene 3 and cyclopropane only 1, so all three could be distinguished from each other.

Key words & phrases: Interpreting the proton H-1 NMR spectra of propane C3H8 CH3CH2CH3, low resolution & high resolution proton nmr spectra of propane, H-1 nmr spectrum of propane, understanding the hydrogen-1 nmr spectrum of propane, explaining the line splitting patterns in the high resolution H-1 nmr spectra of propane, revising the H-1 nmr spectrum of propane, proton nmr of propane, ppm chemical shifts of the H-1 nmr spectrum of propane, 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 propane, how to work out the number of chemically different protons in the structure of the propane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of propane using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of propane deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of propane examining the 1H nmr spectrum of propane analysing the 1-H nmr spectrum of propane how do you sketch and interpret the H-1 NMR spectrum of propane Molecular structure diagram of the proton NMR diagram for the 1H NMR spectrum of propane. The proton ratio in the 1H NMR spectrum of propane. Deducing the number of different chemical environments of the protons in the propane molecule from the 1H chemical shifts in the hydrogen-1 NMR spectrum of propane. Analysing the high resolution 1H NMR spectrum of propane. Analysing the low resolution 1H NMR spectrum of propane. You may need to know the relative molecular mass of propane to deduce the molecular formula from the proton ratio of the 1H NMR spectrum of propane. Revision notes on the proton NMR spectrum of propane. Matching and deducing the structure of the propane molecule from its hydrogen-1 NMR spectrum. How do you interpret the H-1 NMR spectrum of propane How to interpret the H-1 NMR spectrum of propane Explanatory diagram of the chemical shifts of the 1H H-1 proton NMR spectrum of the propane molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the proton NMR spectrum of propane. How to explain the H-1 NMR spectrum of propane. The chemical shifts and integrated values of the proton ratios in the 1-H NMR spectrum of the propane molecule. How to work out the molecular structure of the propane molecule from its proton NMR spectrum. The uses and distinctive features of the proton NMR spectrum of the propane molecule explained. What does the H-1 proton NMR spectrum chemical shifts tell us about the structure and properties of the propane molecule? explaining the spin-spin proton coupling effects in the 1H NMR spectrum of propane. interpretation diagram explaining the proton splitting pattern produced from the n+1 rule and the theoretical ratio of chemical shift δ and values of intensities for the proton NMR spectrum lines of propane

Links associated with propane

The chemistry of ALKANES revision notes INDEX

The infrared spectrum of propane (Please read 8 points at the top of the ¹H NMR index page)

The mass spectrum of propane

The C-13 NMR spectrum of propane

H-1 proton NMR spectroscopy index

ALL SPECTROSCOPY INDEXES

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