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Advanced Organic Chemistry: H-1 NMR spectrum of 2,2-dimethylpropane

The H-1 hydrogen-1 (proton) NMR spectrum of 2,2-dimethylpropane

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 2,2-dimethylpropane

See also comparing the infrared, mass, 1H NMR and 13C NMR spectra of the 3 alkane isomers of C5H12

low and high resolution H-1 proton nmr spectrum of 2,2-dimethylpropane analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 1-H nmr for neopentane 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 - 2,2-dimethylpropane here.

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

2,2-dimethylpropane C5H12 alkanes structure and naming (c) doc b , alkanes structure and naming (c) doc b , alkanes structure and naming (c) doc b

For more see The molecular structure and naming of alkanes

Interpreting the H-1 NMR spectrum of 2,2-dimethylpropane

For relatively simple molecules, the low resolution H-1 NMR spectrum of 2,2-dimethylpropane is a good starting point (low resolution diagram above).

All 12 hydrogen atoms (protons) of 2,2-dimethylpropane occupy the same 1H chemical environment so the NMR spectra only show one proton resonance line.

(CH3)4C

Note:

(i) Only one colour indicating the single chemical environment of the carbon atoms in 2,2-dimethylpropane

(ii) All the protons of the four methyl groups are in an identical chemical environment due to the symmetry of the molecule, the  >C< tetrahedral bond network from the central carbon atom and the symmetry of a methyl group too.

(iii) There is NO proton resonance splitting effect is non of the adjacent protons are 'non-equivalent'.


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 3 alkane isomers of C5H12

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 pentane, 2-methylbutane and 2,2-dimethylpropane image sizes.

Comparing the infrared spectra of pentane, 2-methylbutane and 2,2-dimethylpropane

Pentane, 2-methylbutane and 2,2-dimethylpropane are structural isomers of molecular formula C5H12

Pentane, 2-methylbutane and 2,2-dimethylpropane exemplify infrared spectra of  the alkane homologous series CnH2n+2  hydrocarbon molecules, where n = 5

INFRARED SPECTRA (above): There are, as expected, differences in the fingerprint region at wavenumbers 1500 to 400 cm-1, but there is no specific infrared absorption band for a functional group. The infrared spectra of pentane and 2-methylbutane seem very similar, but that of 2,2-dimethylpropane seems much simpler.

Comparing the mass spectra of pentane, 2-methylbutane and 2,2-dimethylpropane

Pentane, 2-methylbutane and 2,2-dimethylpropane are structural isomers of molecular formula C5H12

Pentane, 2-methylbutane and 2,2-dimethylpropane exemplify the mass spectra of  the alkane series CnH2n+2  hydrocarbon molecules, where n = 5

MASS SPECTRA (above): All three hydrocarbons show some similarities in their mass spectra e.g. m/z ions 27 to 29 for [C2Hx]+ (x = 2 and 4). The molecular ion peaks will be the same for all three isomers (m/z 72), but it is very tiny for 2,2-dimethypropane. The pattern ratios for m/z 39 to 43 are similar for pentane and 2-methylbutane, but m/z 42 and 43 ions are almost absent from the 2,2-dimethylpropane spectrum. The base peak ion for pentane is m/z 43, but for 2-methylbutane and 2,2-dimethylpropane it is m/z 57.

Comparing the 1H proton NMR spectra of pentane, 2-methylbutane and 2,2-dimethylpropane

Pentane, 2-methylbutane and 2,2-dimethylpropane are structural isomers of molecular formula C5H12

Pentane, 2-methylbutane and 2,2-dimethylpropane exemplify the 1H proton NMR spectra of the alkane homologous series CnH2n+2  hydrocarbon molecules where, n = 5

1H NMR SPECTRA (above): The 1H NMR spectra of all three molecules give different proton ratios for the different 1H chemical environments i.e. pentane's proton ratio is 3:2:1 (from 6:4:2 H's in the molecule). 2-methylbutane's proton ratio is 6:1:2:3 and 2,2-dimethylpropane's doesn't have a proton ratio, all hydrogen atoms are equivalent. This means all three isomeric C5H12 hydrocarbons can be distinguished from their 1H NMR spectra.

Comparing the carbon-13 NMR spectra of pentane, 2-methylbutane and 2,2-dimethylpropane

Pentane, 2-methylbutane and 2,2-dimethylpropane are structural isomers of molecular formula C5H12

Pentane, 2-methylbutane and 2,2-dimethylpropane exemplify the carbon-13 NMR spectra of members of  the alkane homologous series CnH2n+2  hydrocarbon molecules, where n = 5

13C NMR SPECTRA (above): The 13C NMR spectra of the three molecules show different numbers of carbon-13 chemical environments i.e different numbers of 13C NMR resonance lines. So, pentane gives three 13C chemical shifts, 2-methylbutane four and 2,2-dimethylpropane two. This means all three isomeric C5H12 hydrocarbons can be distinguished from their 13C NMR spectra.

Key words & phrases: neopentane dimethylpropane Interpreting the proton H-1 NMR spectra of 2,2-dimethylpropane, low resolution & high resolution proton nmr spectra of 2,2-dimethylpropane, H-1 nmr spectrum of 2,2-dimethylpropane, understanding the hydrogen-1 nmr spectrum of 2,2-dimethylpropane, explaining the line splitting patterns in the high resolution H-1 nmr spectra of 2,2-dimethylpropane, revising the H-1 nmr spectrum of 2,2-dimethylpropane, proton nmr of 2,2-dimethylpropane, ppm chemical shifts of the H-1 nmr spectrum of 2,2-dimethylpropane, 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 2,2-dimethylpropane, how to work out the number of chemically different protons in the structure of the 2,2-dimethylpropane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 2,2-dimethylpropane using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of 2,2-dimethylpropane deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 2,2-dimethylpropane examining the 1H nmr spectrum of  2,2-dimethylpropane analysing the 1-H nmr spectrum of 2,2-dimethylpropane how do you sketch and interpret the H-1 NMR spectrum of 2,2-dimethylpropane neopentane dimethylpropane

Molecular structure diagram of the proton NMR diagram for the 1H NMR spectrum of 2,2-dimethylpropane. The proton ratio in the 1H NMR spectrum of 2,2-dimethylpropane. Deducing the number of different chemical environments of the protons in the 2,2-dimethylpropane molecule from the 1H chemical shifts in the hydrogen-1 NMR spectrum of 2,2-dimethylpropane. Analysing the high resolution 1H NMR spectrum of 2,2-dimethylpropane. Analysing the low resolution 1H NMR spectrum of 2,2-dimethylpropane. You may need to know the relative molecular mass of 2,2-dimethylpropane to deduce the molecular formula from the proton ratio of the 1H NMR spectrum of 2,2-dimethylpropane. Revision notes on the proton NMR spectrum of 2,2-dimethylpropane. Matching and deducing the structure of the 2,2-dimethylpropane molecule from its hydrogen-1 NMR spectrum. Proton NMR spectroscopy of aliphatic alkanes, 1H NMR spectra of 2,2-dimethylpropane, an isomer of molecular formula C5H12


Links associated with 2,2-dimethylpropane

The chemistry of ALKANES revision notes INDEX

The infrared spectrum for 2,2-dimethylpropane

The mass spectrum for 2,2-dimethylpropane

The C-13 NMR spectrum for 2,2-dimethylpropane

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

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