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Advanced Organic Chemistry: 1H NMR spectrum of heptane

The H-1 hydrogen-1 (proton) NMR spectrum of heptane

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US K12 grade 11 grade 12 organic chemistry courses involving molecular spectroscopy analysing H-1 NMR spectra of heptane

See also comparing the 1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16

C7H16 low and high resolution 1H proton nmr spectrum of heptane analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for heptane 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 - heptane here.

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

Heptane, C7H16 , CH3(CH2)5CH3 , alkanes structure and naming (c) doc b , alkanes structure and naming (c) doc b

For more see The molecular structure, classification and naming of alkanes

Interpreting the H-1 NMR spectrum of heptane

For relatively simple molecules, the low resolution H-1 NMR spectrum of heptane is a limited, but not useless, starting point.

The hydrogen atoms (protons) of heptane occupy 4 different chemical environments so that the very high resolution NMR spectra should show 4 peaks of different H-1 NMR chemical shifts (diagram above for heptane), BUT three of the chemical shifts are very close together, so even at moderate resolution (diagram above) you see two main peaks in the proton ration 3:5 for CH3:CH2 protons..

CH3CH2CH2CH2CH2CH2CH3

Note the proton ratio 6:4:4:2 (3:2:2:1) of the four colours of the protons in the four chemically different environments, but, even a moderate resolution spectrum (diagram above) shows two main peaks in the ratio of 3:5 for the CH3:CH2 protons.

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

Although there are 16 hydrogen atoms in the molecule, there are, theoretically, only 4 possible different chemical environments for the hydrogen atoms in heptane molecule.

The high resolution 1H NMR spectrum of heptane

All low and high resolution spectra of heptane show 4 groups of proton resonances and in the 3:2:2:1 ratio expected from the formula of heptane.

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

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

(a) 1H Chemical shift 0.88 ppm, CH3 proton resonance, CH3CH2CH2CH2CH2CH2CH3

The CH3 proton resonance is split into a 1:2:1 triplet by the neighbouring CH2 protons.

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

(b) to (d) are very similar and would need very high resolution to resolve the complex splitting patterns involved.

Resonances (a):(b)+(c)+(d) give the ratio 3:5 for the CH3:CH2 proton ratio

(b) 1H Chemical shift 1.30 ppm, CH2 proton resonance, CH3CH2CH2CH2CH2CH2CH3

Theoretically this resonance is split into a sextet (n+1 = 6) by the neighbouring CH3 and CH2 protons.

(c) 1H Chemical shift 1.27 ppm, CH2 proton resonance, CH3CH2CH2CH2CH2CH2CH3

Theoretically this resonance is split into a quintet (n+1 = 5) by the neighbouring CH2 and CH2 protons.

(d) 1H Chemical shift 1.27 ppm, CH2 proton resonance, CH3CH2CH2CH2CH2CH2CH3

Theoretically this resonance is split into a quintet (n+1 = 5) by the neighbouring CH2 and CH2 protons.


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

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.

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 structural formula skeletal formula alkanes molecular structure naming (c) doc b heptane skeletal formula alkanes molecular structure naming (c) doc b 4 δ: proton ratio: 3:2:2:1 (6:4:4:2 in the molecule) 4 δ shifts
2-methylhexane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2-methylhexane skeletal formula alkanes molecular structure naming (c) doc b 6 δ: proton ratio : 6:3:2:2:2:1 6 δ shifts
3-methylhexane structural formula skeletal formula alkanes molecular structure naming (c) doc b 3-methylhexane skeletal formula alkanes molecular structure naming (c) doc b 7 δ: proton ratio: 3:3:3:2:2:2:1 (simplification) !!! 7 δ shifts
3-ethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 3-ethylpentane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 9:6:1 3 δ shifts
2,2-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,2-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 4 δ: proton ratio: 9:3:2:2 5 δ shifts
2,3-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,3-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 6 δ: proton ratio: 6:3:3:2:1:1 (simplification) !!! 6 δ shifts (simplification) !!!
2,4-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,4-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 12:2:2 3 δ shifts
3,3-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 3,3-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 3:3:2 (6:4:4 in the molecule) 4 δ shifts
2,2,3-trimethylbutane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,2,3-trimethylbutane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 9:6:1 4 δ shifts

Key words & phrases: C7H16 Interpreting the proton H-1 NMR spectra of heptane, low resolution & high resolution proton nmr spectra of heptane, H-1 nmr spectrum of heptane, understanding the hydrogen-1 nmr spectrum of heptane, explaining the line splitting patterns in the high resolution H-1 nmr spectra of heptane, revising the H-1 nmr spectrum of heptane, proton nmr of heptane, ppm chemical shifts of the H-1 nmr spectrum of heptane, 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 heptane, how to work out the number of chemically different protons in the structure of the heptane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of heptane using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of heptane deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of heptane examining the 1H nmr spectrum of  heptane analysing the 1-H nmr spectrum of heptane how do you sketch and interpret the H-1 NMR spectrum of heptane interpreting interpretation of the 1H proton NMR spectrum of heptane

Molecular structure diagram of the proton NMR diagram for the 1H NMR spectrum of heptane. The proton ratio in the 1H NMR spectrum of heptane. Deducing the number of different chemical environments of the protons in the heptane molecule from the 1H chemical shifts in the hydrogen-1 NMR spectrum of heptane. Analysing the high resolution 1H NMR spectrum of heptane. Analysing the low resolution 1H NMR spectrum of heptane. You may need to know the relative molecular mass of heptane to deduce the molecular formula from the proton ratio of the 1H NMR spectrum of heptane. Revision notes on the proton NMR spectrum of heptane. Matching and deducing the structure of the heptane molecule from its hydrogen-1 NMR spectrum. Proton NMR spectroscopy of aliphatic alkanes, 1H NMR spectra of heptane, a structural isomer of molecular formula C7H16


Links associated with heptane

The chemistry of ALKANES revision notes INDEX

H-1 proton NMR spectroscopy index  (Please read 8 points at the top of the 1H NMR index page)

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Infrared spectra of the isomers of C7H16

The infrared spectrum of heptane

The infrared spectrum of 2-methylhexane

The infrared spectrum of 3-methylhexane

The infrared spectrum of 3-ethylpentane

The infrared spectrum of 2,2-dimethylpentane

The infrared spectrum of 2,3-dimethylpentane

The infrared spectrum of 2,4-dimethylpentane

The infrared spectrum of 3,3-dimethylpentane

The infrared spectrum of 2,2,3-trimethylbutane

Mass spectra of the isomers of C7H16

The mass spectrum of heptane

The mass spectrum of 2-methylhexane

The mass spectrum of 3-methylhexane

The mass spectrum of 3-ethylpentane

The mass spectrum of 2,2-dimethylpentane

The mass spectrum of 2,3-dimethylpentane

The mass spectrum of 2,4-dimethylpentane

The mass spectrum of 3,3-dimethylpentane

The mass spectrum of 2,2,3-trimethylbutane

H-1 proton NMR spectra of ALKANES

1H NMR spectra of the isomers of C7H16

The H-1 NMR spectrum of heptane

The H-1 NMR spectrum of 2-methylhexane

The H-1 NMR spectrum of 3-methylhexane

The H-1 NMR spectrum of 3-ethylpentane

The H-1 NMR spectrum of 2,2-dimethylpentane

The H-1 NMR spectrum of 2,3-dimethylpentane

The H-1 NMR spectrum of 2,4-dimethylpentane

The H-1 NMR spectrum of 3,3-dimethylpentane

The H-1 NMR spectrum of 2,2,3-trimethylbutane

C-13 carbon-13 NMR spectra of ALKANES

13C NMR spectra of the isomers of C7H16

The C-13 NMR spectrum of heptane

The C-13 NMR spectrum of 2-methylhexane

The C-13 NMR spectrum of 3-methylhexane

The C-13 NMR spectrum of 3-ethylpentane

The C-13 NMR spectrum of 2,2-dimethylpentane

The C-13 NMR spectrum of 2,3-dimethylpentane

The C-13 NMR spectrum of 2,4-dimethylpentane

The C-13 NMR spectrum of 3,3-dimethylpentane

The C-13 NMR spectrum of 2,2,3-trimethylbutane

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