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Advanced Organic Chemistry: 1H NMR spectrum: 2-bromo-2-methylpropane

Interpreting1H NMR spectrum: 2-bromo-2-methylpropane (tert-butyl bromide)

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 proton NMR spectra of 2-bromo-2-methylpropane

See also comparing infrared, mass, 1H NMR & 13C NMR spectra of 4 halogenoalkane isomers of C4H9Br

1H proton nmr spectrum of 2-bromo-2-methylpropane low/high resolution diagrams C4H9Br (CH3)3CBr analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for tert-butyl bromide 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 - 2-bromo-2-methylpropane here.

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

2-bromo-2-methylpropane (tert-butyl bromide), C4H9Br, (CH3)3C-Br

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

In terms of spin-spin coupling from the possible proton magnetic orientations, for 2-bromo-2-methylpropane there no interactions of non-equivalent protons on adjacent carbon atoms e.g. no -CH2-CH3 or -CH2-CH2-, proton situations etc.

Due to the symmetry of the 2-bromo-2-methylpropnae molecule, all 9 protons occupy the same chemical environment and as a consequence there no splitting of the 1H NMR resonance.

Therefore both high or low resolution spectra will only show a single singlet 1H NMR resonance line.

(CH3)3C-Br

One colour for the 9 protons of 2-bromo-2-methylpropane, as all the hydrogen atoms are in the same chemical environment.

Chemical shift (a) of 1.80 ppm on the H-1 NMR spectrum diagram for 2-bromo-2-methylpropane above.

No need for the n+1 rule, life couldn't be simpler!


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
Comparing the infrared, mass, 1H NMR and 13C NMR spectra of the 4 halogenoalkane isomers of C4H9Br

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 1-bromobutane, 2-bromobutane, 1-bromo-2-methylpropane and 2-bromo-2-methylpropane image sizes.  These four molecules are structural isomers of molecular formula C4H9Br and exemplify the infrared, mass, 1H NMR and 13C NMR spectra of lower aliphatic halogenoalkanes (haloalkanes, alkyl halides, bromoalkanes, alkyl bromides).

INFRARED SPECTRA (above): Apart from the significant differences in the fingerprint region at wavenumbers 1500 to 400 cm-1, there are no other great striking differences, but each could be identified from its infrared spectrum.

MASS SPECTRA (above): All four give the parent molecular ions of m/z 136 and 138, but it is only a relatively tiny peak for 2-bromobutane and 2-bromo-2-methylpropane. All four give the base ion peak of m/z 57. All four give prominent peaks for m/z ions 27, 29, 39 and 41 and all give a tiny peak from an ionised iodine atom at m/z 127. They look quite similar to me and lack a clear fingerprint fragmentation pattern. There are small differences in the relative abundances (peak heights) for pairs of ions involving 79Br/81Br isotopes e.g. m/z 93/95, 107/109 and 121/123. 1-bromo-2-methylpropane is the only one of the four to have a prominent peak for the m/z 43 ion.

1H NMR SPECTRA (above): The 1H NMR spectra of all four molecules give different integrated proton ratios i.e.1-bromobutane four peaks of ratio 3:2:2:2; 2-bromobutane four peaks of ratio 3:3:2:1, 1-bromo-2-methylpropane three peaks of ratio 6:2:1 and 2-bromo-2-methylpropane gives just one peak '1' (effectively no ratio involved), so all four molecular structures can be distinguished from each other by their 1H NMR spectra proton ratios, numbers of peaks and (n+1) rule splitting patterns.

13C NMR SPECTRA (above): The 13C NMR spectra of the four molecules show various numbers of carbon-13 chemical environments i.e 1-bromobutane and 2-bromobutane show four 13C NMR resonances, 1-bromo-2-methylpropane three 13C NMR resonances and 2-bromo-2-methylpropane only two 13C resonances. Therefore 1-bromo-2-methylpropane and 2-bromo-2-methylpropane can be distinguished from the other three by their number of resonances in their 13C NMR spectra, but 1-bromobutane and 2-bromobutane cannot be distinguished from each other from their number of 13C NMR resonance lines - other data would be required.

Key words & phrases: C4H9Br (CH3)3CBr Interpreting the proton H-1 NMR spectra of 2-bromo-2-methylpropane, low resolution & high resolution proton nmr spectra of 2-bromo-2-methylpropane, H-1 nmr spectrum of 2-bromo-2-methylpropane, understanding the hydrogen-1 nmr spectrum of 2-bromo-2-methylpropane, explaining the line splitting patterns from spin-spin coupling  in the high resolution H-1 nmr spectra of 2-bromo-2-methylpropane, revising the H-1 nmr spectrum of 2-bromo-2-methylpropane, proton nmr of 2-bromo-2-methylpropane, ppm chemical shifts of the H-1 nmr spectrum of 2-bromo-2-methylpropane, explaining and analyzing spin spin line splitting in the H-1 nmr spectrum, how to construct the diagram of the 1H nmr spectrum of 2-bromo-2-methylpropane, how to work out the number of chemically different protons in the structure of the 2-bromo-2-methylpropane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 2-bromo-2-methylpropane using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of 2-bromo-2-methylpropane deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 2-bromo-2-methylpropane examining the 1H nmr spectrum of 2-bromo-2-methylpropane analysing the 1H nmr spectrum of 2-bromo-2-methylpropane how do you sketch and interpret the H-1 NMR spectrum of 2-bromo-2-methylpropane interpreting interpretation of the 1H proton spin-spin coupling causing line splitting in the NMR spectrum of 2-bromo-2-methylpropane  assignment of chemical shifts in the proton 1H NMR spectrum of 2-bromo-2-methylpropane formula explaining spin-spin coupling for line splitting for 2-bromo-2-methylpropane tert-butyl bromide alkyl halide haloalkane alkyl bromide bromoalkane functional group

Molecular structure diagram of the proton NMR diagram for the 1H NMR spectrum of 2-bromo-2-methylpropane. The proton ratio in the 1H NMR spectrum of 2-bromo-2-methylpropane. Deducing the number of different chemical environments of the protons in the 2-bromo-2-methylpropane molecule from the 1H chemical shifts in the hydrogen-1 NMR spectrum of 2-bromo-2-methylpropane. Analysing the high resolution 1H NMR spectrum of 2-bromo-2-methylpropane. Analysing the low resolution 1H NMR spectrum of 2-bromo-2-methylpropane. You may need to know the relative molecular mass of 2-bromo-2-methylpropane to deduce the molecular formula from the proton ratio of the 1H NMR spectrum of 2-bromo-2-methylpropane. Revision notes on the proton NMR spectrum of 2-bromo-2-methylpropane. Matching and deducing the structure of the 2-bromo-2-methylpropane molecule from its hydrogen-1 NMR spectrum. Proton NMR spectroscopy of halogenoalkanes bromoalkanes alkyl bromides, 1H NMR spectra of 2-bromo-2-methylpropane, an isomer of molecular formula C4H9Br


Links associated with 2-bromo-2-methylpropane

The chemistry of HALOGENOALKANES (haloalkanes) revision notes INDEX

The infrared spectrum of 2-bromo-2-methylpropane (tert-butyl bromide)

The mass spectrum of 2-bromo-2-methylpropane (tert-butyl bromide)

The C-13 NMR spectrum of 2-bromo-2-methylpropane (tert-butyl bromide)

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

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