Advanced Organic pre-university/college Chemistry: The 1H NMR spectrum of benzene C6H6

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Interpreting and explaining the 1H NMR spectrum of benzene C6H6 

[Author ©  Dr Phil Brown GRIC, 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 & AP honors chemistry courses: Molecular spectroscopy of benzene [spectrum page updated RE-EDIT]

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 H-1 proton NMR spectroscopy index

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Introductory note on the 1H NMR spectra of benzene

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

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

The most common solvent used for investigating the 1H NMR spectrum of compounds like benzene, 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 benzene analysis interpretation of chemical shifts ppm spin spin line splitting diagram 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 - benzene here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of benzene represent the peaks of the intensity of the chemical shifts of benzene (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 benzene molecule.

aromatic benzene C6H6, skeletal formula (c) doc b , structural/displayed formula

The molecular structure and naming of aromatic compounds

Interpreting the H-1 NMR spectrum of benzene C6H6

As you can see from the diagram above there is only one chemical shift line in the H-1 NMR spectrum of benzene (at 7.3 ppm) indicating only one chemical environment of all six carbon atoms.

C6H6

So, all six ring protons are equivalent to each other and no splitting of the proton resonance is observed because of the high symmetry of the molecule and equivalent protons do not split each other's proton fields.

This 1H NMR spectrum of benzene fits in with the modern view of it being a completely symmetrical planar hexagonal molecule with all the hydrogen atoms in the same chemical environment (diagram below).

So all you see is one singlet 1H NMR chemical shift at 7.3 ppm.

Take care in presenting the H-1 NMR spectrum of benzene as evidence of the true aromatic structure i.e. the symmetrical hexagon of carbon atoms with a C-C bond order of 1.5 (), with the circular common pi bonding ring of electrons. The hydrogen atoms of the theoretical Kekule structures shown on the right are theoretically all in the same chemical environment too. Since the protons of benzene are equivalent to each other, their proton fields will not split each other.

explaining the 1H proton NMR spectrum of benzene diagram of the rings of pi orbitals of benzene aromatic compounds aromaticity above and below a hexagonal ring of carbon atoms

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).

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

Key words & phrases: Interpreting the proton H-1 NMR spectra of benzene, low resolution & high resolution proton nmr spectra of benzene, H-1 nmr spectrum of benzene, understanding the hydrogen-1 nmr spectrum of benzene, explaining the line splitting patterns in the high resolution H-1 nmr spectra of benzene, revising the H-1 nmr spectrum of benzene, proton nmr of benzene, ppm chemical shifts of the H-1 nmr spectrum of benzene, 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 benzene, how to work out the number of chemically different protons in the structure of the benzene organic molecule How do you interpret the H-1 NMR spectrum of benzene How to interpret the H-1 NMR spectrum of benzene Explanatory diagram of the 1H H-1 proton NMR spectrum of the benzene molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the proton NMR spectrum of benzene. How to explain the H-1 NMR spectrum of benzene. The values of the integrated proton ratios in the 1-H NMR spectrum of the benzene molecule. How to work out the molecular structure of the benzene molecule from its proton NMR spectrum. The uses and distinctive features of the proton NMR spectrum of the benzene molecule explained. What does the H-1 proton NMR spectrum tell us about the structure and properties of the benzene molecule? How do you interpret the H-1 NMR spectrum of benzene How to interpret the H-1 NMR spectrum of benzene Explanatory diagram of the chemical shifts of the 1H H-1 proton NMR spectrum of the benzene molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the proton NMR spectrum of benzene. How to explain the H-1 NMR spectrum of benzene. The chemical shifts and  integrated values of the proton ratios in the 1-H NMR spectrum of the benzene molecule. How to work out the molecular structure of the benzene molecule from its proton NMR spectrum. The uses and distinctive features of the proton NMR spectrum of the benzene molecule explained. What does the H-1 proton NMR spectrum chemical shifts tell us about the structure and properties of the benzene molecule? explaining the spin-spin proton coupling effects in the 1H NMR spectrum of benzene. interpretation 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 benzene

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