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Advanced Organic Chemistry: 1H NMR spectrum of methyl 2-hydroxybenzoate

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Interpreting the H-1 hydrogen-1 (proton) NMR spectrum of methyl 2-hydroxybenzoate

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 methyl 2-hydroxybenzoate (methyl salicylate)

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H-1 proton NMR spectroscopy - spectra index

1H proton nmr spectrum of methyl 2-hydroxybenzoate low/high resolution diagrams C8H8O3 analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for methyl salicylate explaining spin-spin coupling for line splitting oil of wintergreen 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 resonances, called chemical shifts, are measured with respect to the TMS, and depend on the individual (electronic) chemical environment of the hydrogen atoms in an organic molecule - methyl 2-hydroxybenzoate here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of methyl 2-hydroxybenzoate 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 methyl 2-hydroxybenzoate molecule.

C8H8O3, (c) doc b or , methyl 2-hydroxybenzoate (methyl salicylate, 'oil of wintergreen'

For more see The molecular structure and naming of carboxylic acids and derivatives

For more see The molecular structure and naming of aromatic compounds

Interpreting the H-1 NMR spectrum of methyl 2-hydroxybenzoate

For relatively simple molecules, the low resolution H-1 NMR spectrum of methyl 2-hydroxybenzoate is a good starting point (low resolution diagram above).

The 8 hydrogen atoms (protons) of methyl 2-hydroxybenzoate occupy 6 different chemical environments so that the low resolution NMR spectra should show 6 principal resonance peaks of different H-1 NMR chemical shifts (diagram above for methyl 2-hydroxybenzoate).

Note the proton ratio 3:1:1:1:1:1 of the 8 protons of methyl 2-hydroxybenzoate in the 6 chemically different proton environments

Chemical shifts (a) to (f) on the H-1 NMR spectrum diagram for methyl 2-hydroxybenzoate.

Although there are 8 hydrogen atoms in the molecule, the proton NMR spectrum shows there are only 6 possible different chemical environments for the hydrogen atoms in methyl 2-hydroxybenzoate molecule.

The integrated proton signal ratio of 3:1:1:1:1:1 observed in the high resolution H-1 NMR spectrum, corresponds with the structural formula of methyl 2-hydroxybenzoate.

The high resolution 1H NMR spectrum of methyl 2-hydroxybenzoate (methyl salicylate)

In terms of spin-spin coupling from the possible proton magnetic orientations, for methyl 2-hydroxybenzoate I have only considered the interactions of non-equivalent protons on adjacent carbon atoms

The high resolution spectra of methyl 2-hydroxybenzoate shows 6 groups of proton resonances and in the ratio expected from the structural formula of methyl 2-hydroxybenzoate, but we can now consider the splitting of resonance lines from the spin-spin coupling in the molecule of methyl 2-hydroxybenzoate.

The ppm quoted on the diagram represent the peak of resonance intensity for a particular proton group in the molecule of methyl 2-hydroxybenzoate - 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 methyl 2-hydroxybenzoate below.

So, using the chemical shifts and applying the n+1 rule to methyl 2-hydroxybenzoate and make some predictions using some colour coding! (In problem solving you work the other way round!)

1H NMR resonance (a) 1H Chemical shift δ 3.93 ppm:

A singlet resonance for the methyl protons, since no protons on an adjacent carbon atom.

1H NMR resonance (b) 1H Chemical shift δ 10.74 ppm:

A singlet for the hydroxyl proton, since no protons on an adjacent carbon atom.

1H NMR resonance (c) 1H Chemical shift δ 6.97 ppm:

The ring carbon 3 proton resonance is split into a doublet by the ring carbon 4 proton (n+1 = 2). The split (c) resonance overlap with the split (e) resonances.

A series of singlets and doublets in the region of δ 6.4 and 8.2 ppm is indicative of benzene ring protons - you can see this in 1H NMR resonances (c) to (f) in the spectrum of methyl 2-hydroxybenzoate.

1H NMR resonance (d) 1H Chemical shift δ 7.43 ppm:

The ring carbon 4 proton resonance is split into a triplet by the ring carbon protons 3 and 5 (n+2 = 3).

1H NMR resonance (e) 1H Chemical shift δ 6.87 ppm:

The ring carbon 5 proton resonance is split into a triplet by the ring carbon protons 4 and 6 (n+2 = 3).

1H NMR resonance (e) 1H Chemical shift δ 7.81 ppm:

The ring carbon 6 proton resonance is split into a doublet by the ring carbon 5 proton (n+1 = 2).


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: isomer of molecular formula C8H8O3 Interpreting the proton H-1 NMR spectra of methyl 2-hydroxybenzoate, low resolution & high resolution proton nmr spectra of methyl 2-hydroxybenzoate, H-1 nmr spectrum of methyl 2-hydroxybenzoate, understanding the hydrogen-1 nmr spectrum of methyl 2-hydroxybenzoate, explaining the line splitting patterns from spin-spin coupling  in the high resolution H-1 nmr spectra of methyl 2-hydroxybenzoate, revising the H-1 nmr spectrum of methyl 2-hydroxybenzoate, proton nmr of methyl 2-hydroxybenzoate, ppm chemical shifts of the H-1 nmr spectrum of methyl 2-hydroxybenzoate, explaining and analyzing spin spin line splitting in the H-1 nmr spectrum, how to construct the diagram of the 1H nmr spectrum of methyl 2-hydroxybenzoate, how to work out the number of chemically different protons in the structure of the methyl 2-hydroxybenzoate organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of methyl 2-hydroxybenzoate using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of methyl 2-hydroxybenzoate deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of methyl 2-hydroxybenzoate examining the 1H nmr spectrum of methyl 2-hydroxybenzoate analysing the 1H nmr spectrum of methyl 2-hydroxybenzoate how do you sketch and interpret the H-1 NMR spectrum of methyl 2-hydroxybenzoate interpreting interpretation of the 1H proton spin-spin coupling causing line splitting in the NMR spectrum of methyl 2-hydroxybenzoate  assignment of chemical shifts in the proton 1H NMR spectrum of methyl 2-hydroxybenzoate formula explaining spin-spin coupling for line splitting for methyl salicylate old names ester phenol functional group


Links associated with methyl 2-hydroxybenzoate

The infrared spectrum of methyl 2-hydroxybenzoate (methyl salicylate)

The mass spectrum of methyl 2-hydroxybenzoate (methyl salicylate)

The C-13 NMR spectrum of methyl 2-hydroxybenzoate (methyl salicylate)

INDEX of all revision notes on CARBOXYLIC ACIDS and DERIVATIVES

INDEX of all AROMATIC COMPOUND chemistry revision notes

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

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