Advanced level pre-university organic chemistry: 1H NMR spectrum of 1,3,5-trimethylbenzene (mesitylene)

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Interpreting and explaining the 1H NMR spectrum of 1,3,5-trimethylbenzene (mesitylene)

[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 and AP honors chemistry courses: Molecular spectroscopy analysis of 1,3,5-trimethylbenzene [spectrum page updated RE-EDIT]

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 Links associated with 1,3,5-trimethylbenzene (mesitylene)

See also Isomers of molecular formula C9H12 (only aromatic hydrocarbons)

Introductory note on the 1H NMR spectra of 1,3,5-trimethylbenzene (mesitylene)

Students and teachers please note my explanation of the proton NMR spectrum of 1,3,5-trimethylbenzene (mesitylene) is designed for advanced, but pre-university, chemistry courses.

The chemical shift δ splitting pattern effects for 1,3,5-trimethylbenzene (mesitylene) 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 1,3,5-trimethylbenzene (mesitylene) 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 1,3,5-trimethylbenzene (mesitylene) molecule.

The most common solvent used for investigating the 1H NMR spectrum of compounds like 1,3,5-trimethylbenzene (mesitylene), is CDCl3 and other deuterated solvents to avoid confusion with a 1H NMR signal, 2D (2H) has a different NMR chemical shift.

C9H12 low and high resolution H-1 proton nmr spectrum of 1,3,5-trimethylbenzene (mesitylene) analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 1-H nmr for 1,3,5-trimethylbenzene (mesitylene) 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 - 1,3,5-trimethylbenzene (mesitylene) here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of 1,3,5-trimethylbenzene (mesitylene) 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 1,3,5-trimethylbenzene (mesitylene) molecule.

structural formula 1,3,5-trimethylbenzene mesitylene molecular structure molecular formula C9H12 C6H3(CH3)3

The molecular structure and naming of aromatic compounds

Interpreting the H-1 NMR spectrum of 1,3,5-trimethylbenzene (mesitylene)

Because of the symmetry of the molecule, the hydrogen atoms (protons) of 1,3,5-trimethylbenzene (mesitylene) can only occupy 2 different chemical environments so that the low/high resolution NMR spectra should show only 2 peaks of different 1H NMR chemical shifts (diagram above for 1,3,5-trimethylbenzene (mesitylene)).

Although there are 12 hydrogen atoms in the molecule, there are only 2 possible different chemical environments for the hydrogen atoms in 1,3,5-trimethylbenzene (mesitylene) molecule - a very symmetrical molecule.

The integrated signal proton ratio 1:3 observed in the high resolution H-1 NMR spectrum, corresponds with the structural formula of 1,3,5-trimethylbenzene (mesitylene) in terms of the aryl:alkyl protons.

The high resolution H-1 NMR spectrum of 1,3,5-trimethylbenzene (mesitylene)

The ppm quoted on the diagram represent the peak of resonance intensity for a particular proton group in the molecule of 1,3,5-trimethylbenzene (mesitylene) - 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 1,3,5-trimethylbenzene (mesitylene) below.

(a) 1H Chemical shift 6.78 ppm resonance from the benzene ring protons.

All three aromatic protons are equivalent and no significant splitting observed, so a singlet peak is observed.

(b) 1H Chemical shift 2.26 ppm from the methyl protons, so a singlet peak is observed.

All nine alkyl protons are equivalent and no significant splitting observed, so again, a singlet peak is observed.

What you get from the spectrum is a ratio of 1:3 (3:9 in actual proton numbers) for aryl:alkyl protons in 1,3,5-trimethylbenzene.

The relatively small number of 1H NMR chemical shifts is due to the very high symmetry of the 1,3,5-trimethylbenzene molecule (mesitylene).

Adding D2O to the sample under investigation, dissolved in CDCl3, makes no difference to the 1H NMR spectrum of 1,3,5-trimethylbenzene (mesitylene) because there are no labile protons to exchange with deuterium (2H) e.g. as in alcohols (O-H) or amines (N-H).

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 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

Key words & phrases: C9H12 C6H3(CH3)3 Interpreting the proton H-1 NMR spectra of 1,3,5-trimethylbenzene (mesitylene), low resolution & high resolution proton nmr spectra of 1,3,5-trimethylbenzene (mesitylene), H-1 nmr spectrum of 1,3,5-trimethylbenzene (mesitylene), understanding the hydrogen-1 nmr spectrum of 1,3,5-trimethylbenzene (mesitylene), explaining the line splitting patterns in the high resolution H-1 nmr spectra of 1,3,5-trimethylbenzene (mesitylene), revising the H-1 nmr spectrum of 1,3,5-trimethylbenzene (mesitylene), proton nmr of 1,3,5-trimethylbenzene (mesitylene), ppm chemical shifts of the H-1 nmr spectrum of 1,3,5-trimethylbenzene (mesitylene), 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 1,3,5-trimethylbenzene (mesitylene), how to work out the number of chemically different protons in the structure of the 1,3,5-trimethylbenzene (mesitylene) organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 1,3,5-trimethylbenzene (mesitylene) using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of 1,3,5-trimethylbenzene (mesitylene) deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 1,3,5-trimethylbenzene (mesitylene) examining the 1H nmr spectrum of  1,3,5-trimethylbenzene (mesitylene) analysing the 1-H nmr spectrum of 1,3,5-trimethylbenzene (mesitylene) how do you sketch and interpret the H-1 NMR spectrum of 1,3,5-trimethylbenzene (mesitylene) interpreting interpretation of the H-1 proton NMR spectrum of 1,3,5-trimethylbenzene (mesitylene) How do you interpret the H-1 NMR spectrum of mesitylene How to interpret the H-1 NMR spectrum of mesitylene Explanatory diagram of the chemical shifts of the 1H H-1 proton NMR spectrum of the mesitylene molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the proton NMR spectrum of mesitylene. How to explain the H-1 NMR spectrum of mesitylene. The chemical shifts and  integrated values of the proton ratios in the 1-H NMR spectrum of the mesitylene molecule. How to work out the molecular structure of the mesitylene molecule from its proton NMR spectrum. The uses and distinctive features of the proton NMR spectrum of the mesitylene molecule explained. What does the H-1 proton NMR spectrum chemical shifts tell us about the structure and properties of the mesitylene molecule? explaining the spin-spin proton coupling effects in the 1H NMR spectrum of mesitylene. 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 mesitylene

Links associated with 1,3,5-trimethylbenzene (mesitylene)

See also Isomers of molecular formula C9H12 (only aromatic hydrocarbons)

The mass spectrum of 1,3,5-trimethylbenzene

The C-13 NMR spectrum of 1,3,5-trimethylbenzene

The infrared spectrum of 1,3,5-trimethylbenzene

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