HOME PAGE * KS3 SCIENCES * GCSE BIOLOGY CHEMISTRY PHYSICS * ADVANCED LEVEL CHEMISTRY

SPECTROSCOPY INDEXES  *  All Advanced Organic Chemistry Notes  *  [SEARCH BOX]

Advanced Organic Chemistry: 1H NMR spectrum of ethylamine

Interpreting the H-1 (proton) NMR spectrum of ethylamine (ethanamine)

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 ethylamine

1H proton nmr spectrum of ethylamine low/high resolution diagrams formula analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for ethanamine explaining spin-spin coupling for line splitting 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 - ethylamine here.

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

Ethylamine (aminoethane, ethanamine), C2H7N,  (c) doc b, (c) doc b, (c) doc b, (c) doc b

Interpreting the H-1 NMR spectrum of ethylamine

In terms of spin-spin coupling from the possible proton magnetic orientations, for ethylamine I have only considered the interactions of non-equivalent protons on adjacent carbon atoms e.g. -CH2-CH3 (but see note alter on N-H protons).

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

The hydrogen atoms (protons) of ethylamine occupy 3 different chemical environments so that the low resolution NMR spectra should show 3 principal peaks of different H-1 NMR chemical shifts (diagram above for ethylamine).

CH3CH2NH2

Note the proton ratio 3:2:2 of the 3 colours of the 8 protons in the 3 chemically different proton environments

Chemical shifts (a) to (c) on the H-1 NMR spectrum diagram for ethylamine.

Although there are 7 hydrogen atoms in the molecule, there are only 3 possible different chemical environments for the hydrogen atoms in ethylamine molecule.

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

The high resolution 1H NMR spectrum of ethylamine

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

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

(a) 1H Chemical shift 1.10 ppm, methyl protons: CH3CH2NH2

This resonance is split into a 1:2:1 triplet by the adjacent CH2 protons (n+1 = 3).

Evidence for the presence of a CH2 group in the molecule of ethylamine

(b) 1H Chemical shift 2.61 ppm, CH2 protons: CH3CH2NH2

This resonance is split into a 1:3:3:1 quartet by the adjacent CH3 protons (n+1 = 4), but not by the N-H protons.

I have assumed the N-H protons do NOT cause splitting (see (c)).

Evidence for the presence of a CH3 group in the molecule of ethylamine.

Resonances (a) and (b) provide evidence for the ethyl group in ethylamine.

(c) 1H Chemical shift 1.04 ppm, amine group protons: CH3CH2NH2

This resonance appears as a singlet chemical shift for ethylamine.

I have assumed the adjacent CH2 group protons do NOT cause splitting of the N-H proton resonance, therefore the amine group proton resonance is not split by the adjacent CH2 protons, so appears a singlet.

The lack of resonance splitting is due to exchange of protons between the amine group of the amine molecules which inhibits the coupling between amine group protons and any adjacent alky group protons (and vice versa) - even a trace of water catalyses this effect.

e.g. for aliphatic primary/secondary aliphatic amines, if R = H or alkyl

R2N-H  +  H-O-H  (c) doc b  H-R2N-H+  +  OH-  (c) doc b  R2N-H  +  H-O-H


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: C2H7N CH3CH2NH2 Interpreting the proton H-1 NMR spectra of ethylamine, low resolution & high resolution proton nmr spectra of ethylamine, H-1 nmr spectrum of ethylamine, understanding the hydrogen-1 nmr spectrum of ethylamine, explaining the line splitting patterns from spin-spin coupling  in the high resolution H-1 nmr spectra of ethylamine, revising the H-1 nmr spectrum of ethylamine, proton nmr of ethylamine, ppm chemical shifts of the H-1 nmr spectrum of ethylamine, 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 ethylamine, how to work out the number of chemically different protons in the structure of the ethylamine organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of ethylamine using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of ethylamine deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of ethylamine examining the 1H nmr spectrum of  ethylamine analysing the 1-H nmr spectrum of ethylamine how do you sketch and interpret the H-1 NMR spectrum of ethylamine interpreting interpretation of the 1H proton spin-spin coupling causing line splitting in the NMR spectrum of ethylamine  assignment of chemical shifts in the proton 1H NMR spectrum of ethylamine formula explaining spin-spin coupling for line splitting for ethylamine primary aliphatic amine functional group ethanamine


Links associated with ethylamine

The chemistry of ORGANIC NITROGEN COMPOUNDS revision notes INDEX

H-1 proton NMR spectroscopy index

ALL SPECTROSCOPY INDEXES

All Advanced Organic Chemistry Notes

Use My Google search site box

Email doc b: chem55555@hotmail.com

TOP OF PAGE

 Doc Brown's Chemistry 

*

TOP OF PAGE