Advanced Organic Chemistry: H-1 NMR spectrum of 1,4-dimethylbenzene

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The H-1 hydrogen-1 (proton) NMR spectrum of 1,4-dimethylbenzene

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 1,4-dimethylbenzene

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H-1 proton NMR spectroscopy - spectra index

C8H10 low and high resolution H-1 proton nmr spectrum of 1,4-dimethylbenzene analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 1-H nmr for p-xylene 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 - 1,4-dimethylbenzene here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of 1,4-dimethylbenzene 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 1,4-dimethylbenzene molecule.

1,4-dimethylbenzene, C8H10, (c) doc b , (c) doc b

Interpreting the H-1 NMR spectrum of 1,4-dimethylbenzene

From the H-1 NMR spectrum, the hydrogen atoms (protons) of 1,4-dimethylbenzene occupy 2 different chemical environments so that the low/high resolution NMR spectra should show 2 peaks of different H-1 NMR chemical shifts (diagram above for 1,4-dimethylbenzene).

Although there are 10 hydrogen atoms in the molecule, because of the symmetry, there are only 2 possible different chemical environments for the hydrogen atoms in 1,4-dimethylbenzene molecule, which is the most symmetrical you can get with a disubstitued benzene ring compound with two identical substituents.

The integrated signal proton ratio 2:3 observed in the high resolution H-1 NMR spectrum, corresponds with the structural formula of 1,4-dimethylbenzene (actually 4 aryl protons: 6 alkyl methyl protons).

The high resolution H-1 NMR spectrum of 1,4-dimethylbenzene

The ppm quoted on the diagram represent the peak of resonance intensity for a particular proton group in the molecule of 1,4-dimethylbenzene - 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 1,4-dimethylbenzene below.

(a) 1H Chemical shift 2.30 ppm for the 2 x CH3 protons.

No splitting observed since there are no protons on the adjacent carbon atom of the benzene ring.

(b) 1H Chemical shift 7.05 ppm for the 4 benzene ring protons.

There doesn't seem to be any splitting observed by benzene ring protons on each other, because ....

... all four CH ring carbon atoms are equivalent to each other and equivalent protons do NOT split each other's resonance lines.

A bunch of chemical shifts ~7 ppm is indicative of benzene ring CH protons.

What you can get from the spectrum is an integrated proton ratio of 2:3 for aryl:alkyl protons in 1,4-dimethylbenzene.

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: para-xylene C8H10 C6H4(CH3)2 Interpreting the proton H-1 NMR spectra of 1,4-dimethylbenzene, low resolution & high resolution proton nmr spectra of 1,4-dimethylbenzene, H-1 nmr spectrum of 1,4-dimethylbenzene, understanding the hydrogen-1 nmr spectrum of 1,4-dimethylbenzene, explaining the line splitting patterns in the high resolution H-1 nmr spectra of 1,4-dimethylbenzene, revising the H-1 nmr spectrum of 1,4-dimethylbenzene, proton nmr of 1,4-dimethylbenzene, ppm chemical shifts of the H-1 nmr spectrum of 1,4-dimethylbenzene, 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 1,4-dimethylbenzene, how to work out the number of chemically different protons in the structure of the 1,4-dimethylbenzene organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 1,4-dimethylbenzene using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of 1,4-dimethylbenzene deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 1,4-dimethylbenzene examining the 1H nmr spectrum of  1,4-dimethylbenzene analysing the 1-H nmr spectrum of 1,4-dimethylbenzene how do you sketch and interpret the H-1 NMR spectrum of 1,4-dimethylbenzene interpreting interpretation of the H-1 proton NMR spectrum of 1,4-dimethylbenzene p-xylene Molecular structure diagram of the proton NMR diagram for the 1H NMR spectrum of 1,4-dimethylbenzene. The proton ratio in the 1H NMR spectrum of 1,4-dimethylbenzene. Deducing the number of different chemical environments of the protons in the 1,4-dimethylbenzene molecule from the 1H chemical shifts in the hydrogen-1 NMR spectrum of 1,4-dimethylbenzene. Analysing the high resolution 1H NMR spectrum of 1,4-dimethylbenzene. Analysing the low resolution 1H NMR spectrum of 1,4-dimethylbenzene. You may need to know the relative molecular mass of 1,4-dimethylbenzene to deduce the molecular formula from the proton ratio of the 1H NMR spectrum of 1,4-dimethylbenzene. Revision notes on the proton NMR spectrum of 1,4-dimethylbenzene. Matching and deducing the structure of the 1,4-dimethylbenzene molecule from its hydrogen-1 NMR spectrum. Proton NMR spectroscopy of aromatic arenes, 1H NMR spectra of 1,4-dimethylbenzene, an isomer of molecular formula C8H10

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