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Advanced Organic Chemistry: 1H NMR spectrum of 1,1-dibromoethane

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

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 1,1-dibromoethane

C2H4Br2 CH3CHBr2 low and high resolution 1H proton nmr spectrum of 1,1-dibromoethane analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for 1,1-dibromoethane 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 - 1,1-dibromoethane here.

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

1,1-dibromoethane, C2H4Br2, CH3CHBr2

Interpreting the H-1 NMR spectrum of 1,1-dibromoethane

In terms of spin-spin coupling from the possible proton magnetic orientations, for 1,1-dibromoethane I have only considered the interactions of non-equivalent protons on adjacent carbon atoms e.g. -CH-CH3 protons.

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

CH3CHBr2

Note the proton ratio 3:1 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 1,1-dibromoethane.

Although there are 4 hydrogen atoms in the molecule, but there are only 2 possible different chemical environments for the hydrogen atoms in 1,1-dibromoethane molecule.

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

The high resolution 1H NMR spectrum of 1,1-dibromoethane

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

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

(a) 1H Chemical shift 5.84 ppm, CH proton: CH3CHBr2

The CH proton resonance is split by the other CH3 protons into a 1:3:3:1 quartet (n+1 = 4)

Evidence for the presence of a CH3 group in the molecule of 1,1-dibromoethane

(b) 1H Chemical shift 2.46 ppm, -CH3 protons: CH3CHBr2

The CH3 protons resonance is split by the CH proton into a 1:1 doublet (n+1 = 2)

Evidence for the presence of a -CH- group in the molecule of 1,1-dibromoethane.


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: C2H4Br2 CH3CHBr2 Interpreting the proton H-1 NMR spectra of 1,1-dibromoethane, low resolution & high resolution proton nmr spectra of 1,1-dibromoethane, H-1 nmr spectrum of 1,1-dibromoethane, understanding the hydrogen-1 nmr spectrum of 1,1-dibromoethane, explaining the line splitting patterns from spin-spin coupling  in the high resolution H-1 nmr spectra of 1,1-dibromoethane, revising the H-1 nmr spectrum of 1,1-dibromoethane, proton nmr of 1,1-dibromoethane, ppm chemical shifts of the H-1 nmr spectrum of 1,1-dibromoethane, 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 1,1-dibromoethane, how to work out the number of chemically different protons in the structure of the 1,1-dibromoethane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 1,1-dibromoethane using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of 1,1-dibromoethane deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 1,1-dibromoethane examining the 1H nmr spectrum of  1,1-dibromoethane analysing the 1-H nmr spectrum of 1,1-dibromoethane how do you sketch and interpret the H-1 NMR spectrum of 1,1-dibromoethane interpreting interpretation of the 1H proton spin-spin coupling causing line splitting in the NMR spectrum of 1,1-dibromoethane  assignment of chemical shifts in the proton 1H NMR spectrum of 1,1-dibromoethane formula explaining spin-spin coupling for line splitting


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