Advanced Organic Chemistry: H-1 NMR spectrum of Methylbenzene (Toluene)

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H-1 hydrogen-1 (proton) NMR spectrum of Methylbenzene (Toluene)

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 methylbenzene

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H-1 proton NMR spectroscopy - spectra index

low and high resolution H-1 proton nmr spectrum of methylbenzene 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 - methylbenzene here.

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

Methylbenzene  C7H8, C6H5CH3 (c) doc b , (c) doc b , (c) doc b

Interpreting the H-1 NMR spectrum of Methylbenzene (Toluene)

For relatively simple molecules, the low resolution H-1 NMR spectrum of methylbenzene is a good starting point.

Theoretically the hydrogen atoms (protons) of methylbenzene occupy 4 different chemical environments,  but the H-1 proton low resolution NMR spectra shows only two peaks.

Apart from the side-chain methyl group, the ring protons can occupy the three different positions on the benzene ring (carbon atoms 2 = 6, 3 = 5 and 4 on the diagram).

However, the chemical shift lines from multiple spin - spin splitting of the ring protons are close together giving a bunch in the 7.00 to 7.38 ppm region.

No splitting of the methyl group protons are evident because the is no adjacent proton on carbon atom 1.

In fact even a moderately high resolution H-1 NMR of methyl benzene shows only two 'bunches' of lines (diagram above).

Therefore what you see is two groups of protons in the ration 5 in the benzene ring to 3 in the side-chain methyl group of methylbenzene.

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 methylbenzene, low resolution & high resolution proton nmr spectra of methylbenzene, H-1 nmr spectrum of methylbenzene, understanding the hydrogen-1 nmr spectrum of methylbenzene, explaining the line splitting patterns in the high resolution H-1 nmr spectra of methylbenzene, revising the H-1 nmr spectrum of methylbenzene, proton nmr of methylbenzene, ppm chemical shifts of the H-1 nmr spectrum of methylbenzene, 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 methylbenzene, how to work out the number of chemically different protons in the structure of the methylbenzene organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of methylbenzene

Associated links

The chemistry of AROMATIC COMPOUNDS revision notes INDEX

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


All Advanced Organic Chemistry Notes

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