Advanced Organic Chemistry: 1H NMR spectrum of 1-bromo-2-chloroethane

The H-1 hydrogen-1 (proton) NMR spectrum of 1-bromo-2-chloroethane

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-bromo-2-chloroethane

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H-1 proton NMR spectroscopy - spectra index

C2H4BrCl BrCH2CH2Cl low and high resolution 1H proton nmr spectrum of 1-bromo-2-chloroethane analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for 1-bromo-2-chloroethane 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 - 1-bromo-2-chloroethane here.

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

1-bromo-2-chloroethane,  C2H4BrCl,  BrCH2CH2Cl

Interpreting the H-1 NMR spectrum of 1-bromo-2-chloroethane

In terms of spin-spin coupling from the possible proton magnetic orientations, for 1-bromo-2-chloroethane I have only considered the interactions of non-equivalent protons on adjacent carbon atoms e.g. here Br-CH2-CH2-Cl.

Theoretically, the four hydrogen atoms (protons) of 1-bromo-2-chloroethane occupy 2 different chemical environments so principal peaks of different H-1 NMR chemical shifts should be observed.

BrCH2CH2Cl

Note the proton ratio 2:2 (observed as 1:1) of the 2 colours of the protons in the 2 chemically different environments

Chemical shifts (a) to (b) on the H-1 NMR spectrum diagram for 1-bromo-2-chloroethane.

The high resolution 1H NMR spectrum of 1-bromo-2-chloroethane

The ppm quoted on the diagram represent the peak of resonance intensity for a particular proton group in the molecule of 1-bromo-2-chloroethane - 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-bromo-2-chloroethane below.

However, the two resonances are very close together and you need very high resolution to the two peak values - I've sketched this on the diagram above.

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

(a) 1H Chemical shift 2.82 ppm: BrCH2CH2Cl

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

Evidence for the presence of a CH2 group in the molecule of 1-bromo-2-chloroethane

(b) 1H Chemical shift 2.98 ppm: BrCH2CH2Cl

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

Evidence for the presence of a 2nd CH2 group in the molecule of 1-bromo-2-chloroethane

Note the increased effect on the 1H chemical shift by the more electronegative chlorine atom - compared to the less electronegative bromine.

The two chemical shifts, and subsequent splitting into triplets, is caused the bromine and chlorine atoms creating different chemical environments for the two sets of CH2 protons.

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: C2H4BrCl BrCH2CH2Cl Interpreting the proton H-1 NMR spectra of 1-bromo-2-chloroethane, low resolution & high resolution proton nmr spectra of 1-bromo-2-chloroethane, H-1 nmr spectrum of 1-bromo-2-chloroethane, understanding the hydrogen-1 nmr spectrum of 1-bromo-2-chloroethane, explaining the line splitting patterns from spin-spin coupling  in the high resolution H-1 nmr spectra of 1-bromo-2-chloroethane, revising the H-1 nmr spectrum of 1-bromo-2-chloroethane, proton nmr of 1-bromo-2-chloroethane, ppm chemical shifts of the H-1 nmr spectrum of 1-bromo-2-chloroethane, 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-bromo-2-chloroethane, how to work out the number of chemically different protons in the structure of the 1-bromo-2-chloroethane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 1-bromo-2-chloroethane using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of 1-bromo-2-chloroethane deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 1-bromo-2-chloroethane examining the 1H nmr spectrum of  1-bromo-2-chloroethane analysing the 1-H nmr spectrum of 1-bromo-2-chloroethane how do you sketch and interpret the H-1 NMR spectrum of 1-bromo-2-chloroethane interpreting interpretation of the 1H proton spin-spin coupling causing line splitting in the NMR spectrum of 1-bromo-2-chloroethane  assignment of chemical shifts in the proton 1H NMR spectrum of 1-bromo-2-chloroethane formula explaining spin-spin coupling for line splitting

Links associated with 1-bromo-2-chloroethane

The chemistry of HALOGENOALKANES (haloalkanes) revision notes INDEX

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

ALL SPECTROSCOPY INDEXES

All Advanced Organic Chemistry Notes

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