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Advanced Organic Chemistry: H-1 NMR spectrum of methyl methanoate

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The H-1 hydrogen-1 (proton) NMR spectrum of methyl methanoate

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 methanoate

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H-1 proton NMR spectroscopy - spectra index

See also comparing the infrared, mass, 1H and 13C NMR spectra of the isomers of C2H4O2

low and high resolution H-1 proton nmr spectrum of methyl methanoate analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 1-H nmr for methyl formate 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 - methyl methanoate here.

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

Methyl methanoate (methyl formate) C2H4O2(c) doc b , (c) doc b , (c) doc b

For more see Structure and naming of CARBOXYLIC ACIDS and DERIVATIVES, including isomers

Interpreting the H-1 NMR spectrum of methyl methanoate

For relatively simple molecules, the low or high resolution H-1 NMR spectrum of methyl methanoate shows two peaks (diagram above).

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

HCOOCH3

Note the ratio 1:3 of the two colours of the protons in the two chemically different environments

Although there are four hydrogen atoms in the molecule, there only 2 possible chemical environments for the hydrogen atoms in methyl methanoate molecule.

The integrated proton ratio integrated 1:3 ratio observed, corresponds with the structural formula of methyl methanoate.

The two 1H chemical environments in the methyl methanoate molecule are the methyl group protons (CH3, 3.75 ppm chemical shift) and the CH proton (8.07 ppm chemical shift).

Neither proton resonance signal is split because there are no protons on an adjacent carbon atom, the carbon atoms/protons are separated by an oxygen atom.

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
Comparing the infrared, mass, 1H NMR and 13C NMR spectra of the 2 isomers of C2H4O2

NOTE: The images are linked to their original detailed spectral analysis pages AND can be doubled in size with touch screens to increase the definition to the original ethanoic acid (acetic acid) and methyl methanoate (methyl formate) image sizes.

INFRARED SPECTRA: Apart from the significant differences in the fingerprint region at wavenumbers 1500 to 400 cm-1, the most striking difference is the broad O-H stretching band ~3200 cm-1, found in the infrared spectrum of carboxylic acids, but absent in the infrared spectrum of esters.

MASS SPECTRA: Apart from the m/z of 60 for the parent molecular ion and m/z 15 ion [CH3]+, both ethanoic acid and methyl methanoate show few similarities in their mass spectra. Their base ion peaks are quite different - for ethanoic acid it is m/z 43 and for methyl methanoate it is m/z 31.

1H NMR SPECTRA: The 1H NMR spectra of ethanoic acid and methyl methanoate are similar with two 'wide-apart' chemical shift singlet peaks in the integrated proton ratio of 3:1 (meaning 2 different 1H chemical environments). However, although no splitting is observed, the 1H chemical shifts for the two molecules are different, those of methyl methanoate are much closer together.

13C NMR SPECTRA: The 13C NMR spectra of ethanoic acid and methyl methanoate are similar, both molecules give two C-13 NMR spectral lines (meaning 2 different 13C chemical environments).


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Links associated with methyl methanoate

The chemistry of CARBOXYLIC ACIDS and DERIVATIVES revision notes INDEX

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

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