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

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Interpreting the H-1 hydrogen-1 (proton) NMR spectrum of 2,2-dimethylpentane

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-dimethylpentane

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H-1 proton NMR spectroscopy - spectra index

See also comparing the 1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16


1H NMR 2,2-dimethylpentane spectra note: Students and teachers please note my explanation of the proton NMR spectrum of 2,2-dimethylpentane is designed for advanced, but pre-university, chemistry courses. The chemical shift δ spin-spin coupling effects for 2,2-dimethylpentane are confined to adjacent non-equivalent protons analysed using the n+1 splitting rule. It is assumed that the integrated intensities of the δ chemical shifts give the ratio of the protons in the different non-equivalent chemical environments in the 2,2-dimethylpentane molecule.

C7H16 low and high resolution 1H proton nmr spectrum of 2,2-dimethylpentane analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for 2,2-dimethylpentane 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-dimethylpentane here.

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

2,2-dimethylpentane C7H16 alkanes structure and naming (c) doc b alkanes structure and naming (c) doc b alkanes structure and naming (c) doc b

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

For relatively simple molecules, the low resolution H-1 NMR spectrum of 2,2-dimethylpentane is a good, but limited starting point.

Theoretically, the 16 hydrogen atoms (protons) of 2,2-dimethylpentane occupy 4 different chemical environments so that the low resolution NMR spectra should show 4 principal peaks of different H-1 NMR chemical shifts (diagram above for 2,2-dimethylpentane).

BUT, as you can see, you get only 2 principal peaks in the integrated proton ratio observed of 3:1 for the CH3:CH2 proton ratio.

(CH3)3CCH2CH2CH3

Note the 'real' proton ratio 9:2:2:3 of the 4 colours of the protons in the 4 chemically different environments

Chemical shifts (a) to (d) on the H-1 NMR spectrum diagram for 2,2-dimethylpentane.

Although there are 16 hydrogen atoms in the molecule, there are only 4 possible different chemical environments for the hydrogen atoms in 2,2-dimethylpentane molecule.

The high resolution 1H NMR spectrum of 2,2-dimethylpentane

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

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

(a) 1H Chemical shift 0.86 ppm for the -C(CH3)3 protons: (CH3)3CCH2CH2CH3

Resonance (a) would not be readily split, since no protons on the adjacent carbon atom on the right - this theoretically gives a singlet.

All nine protons on these three methyl group of 2,2-dimethylpentane are equivalent to each other and their proton fields cannot split each i.e. they occupy identical chemical environments and absorb at the same chemical shift.

(b) and (c) 1H Chemical shift 1.18 ppm for the -CH2- protons: (CH3)3CCH2CH2CH3

These are almost identical, but theoretically different - you would need very high resolution spectra to sort them out.

(b) is split into a 1:2:1 triplet by the neighbouring (c) CH2 protons (n+1 = 3).

Evidence of a CH2 group in the molecule.

(c) is split into a sextet by the neighbouring CH2 and CH3 protons (n+1 =6).

Evidence of a CH2-C-CH3 grouping in the molecule.

(d) 1H Chemical shift 0.88 ppm for the 'lone' CH3 group: (CH3)3CCH2CH2CH3

(d) is split into a 1:2:1 triplet by the neighbouring (c) CH2 protons (n+1 = 3).

Evidence of a 2nd CH2 group in the molecule.

Very similar to 1H resonance (a) and you would need very high resolution spectra to resolve (a) and (d).


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 1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16

You can distinguish all 9 isomers from a data combination of their number of 1H NMR chemical shifts,

and their resulting integrated 1H proton ratios, plus, their number of 13C chemical shifts.

Name of the alkane structural isomer of molecular formula C7H16 Abbreviated structural formulae of the nine isomers of molecular formula C7H16 (interpretation complications with 3-methylhexane and 2,3-dimethylpentane because they exhibit R/S isomerism due to a chiral carbon) Skeletal formula of the nine alkane isomers of  molecular formula C7H16 Number of 1H NMR chemical shifts (δ) and proton ratio (links to spectrum) Number of 13C chemical shifts (δ) (links to spectrum)
heptane structural formula skeletal formula alkanes molecular structure naming (c) doc b heptane skeletal formula alkanes molecular structure naming (c) doc b 4 δ: proton ratio: 3:2:2:1 (6:4:4:2 in the molecule) 4 δ shifts
2-methylhexane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2-methylhexane skeletal formula alkanes molecular structure naming (c) doc b 6 δ: proton ratio : 6:3:2:2:2:1 6 δ shifts
3-methylhexane structural formula skeletal formula alkanes molecular structure naming (c) doc b 3-methylhexane skeletal formula alkanes molecular structure naming (c) doc b 7 δ: proton ratio: 3:3:3:2:2:2:1 (simplification) ! 7 δ shifts
3-ethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 3-ethylpentane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 9:6:1 3 δ shifts
2,2-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,2-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 4 δ: proton ratio: 9:3:2:2 5 δ shifts
2,3-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,3-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 6 δ: proton ratio: 6:3:3:2:1:1 (simplification) ! 6 δ shifts (simplification) !!!
2,4-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,4-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 12:2:2 3 δ shifts
3,3-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 3,3-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 3:3:2 (6:4:4 in the molecule) 4 δ shifts
2,2,3-trimethylbutane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,2,3-trimethylbutane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 9:6:1 4 δ shifts

Key words & phrases: C7H16 Interpreting the proton H-1 NMR spectra of 2,2-dimethylpentane, low resolution & high resolution proton nmr spectra of 2,2-dimethylpentane, H-1 nmr spectrum of 2,2-dimethylpentane, understanding the hydrogen-1 nmr spectrum of 2,2-dimethylpentane, explaining the line splitting patterns in the high resolution H-1 nmr spectra of 2,2-dimethylpentane, revising the H-1 nmr spectrum of 2,2-dimethylpentane, proton nmr of 2,2-dimethylpentane, ppm chemical shifts of the H-1 nmr spectrum of 2,2-dimethylpentane, 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-dimethylpentane, how to work out the number of chemically different protons in the structure of the 2,2-dimethylpentane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 2,2-dimethylpentane using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of 2,2-dimethylpentane deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 2,2-dimethylpentane examining the 1H nmr spectrum of  2,2-dimethylpentane analysing the 1-H nmr spectrum of 2,2-dimethylpentane how do you sketch and interpret the H-1 NMR spectrum of 2,2-dimethylpentane interpreting interpretation of the 1H proton NMR spectrum of 2,2-dimethylpentane (CH3)3CCH2CH2CH3 Molecular structure diagram of the proton NMR diagram for the 1H NMR spectrum of 2,2-dimethylpentane. The proton ratio in the 1H NMR spectrum of 2,2-dimethylpentane. Deducing the number of different chemical environments of the protons in the 2,2-dimethylpentane molecule from the 1H chemical shifts in the hydrogen-1 NMR spectrum of 2,2-dimethylpentane. Analysing the high resolution 1H NMR spectrum of 2,2-dimethylpentane. Analysing the low resolution 1H NMR spectrum of 2,2-dimethylpentane. You may need to know the relative molecular mass of 2,2-dimethylpentane to deduce the molecular formula from the proton ratio of the 1H NMR spectrum of 2,2-dimethylpentane. Revision notes on the proton NMR spectrum of 2,2-dimethylpentane. Matching and deducing the structure of the 2,2-dimethylpentane molecule from its hydrogen-1 NMR spectrum. Proton NMR spectroscopy of aliphatic alkanes, 1H NMR spectra of 2,2-dimethylpentane, a structural isomer of molecular formula C7H16 How do you interpret the H-1 NMR spectrum of 2,2-dimethylpentane How to interpret the H-1 NMR spectrum of 2,2-dimethylpentane Explanatory diagram of the chemical shifts of the 1H H-1 proton NMR spectrum of the 2,2-dimethylpentane molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the proton NMR spectrum of 2,2-dimethylpentane. How to explain the H-1 NMR spectrum of 2,2-dimethylpentane. The chemical shifts and  integrated values of the proton ratios in the 1-H NMR spectrum of the 2,2-dimethylpentane molecule. How to work out the molecular structure of the 2,2-dimethylpentane molecule from its proton NMR spectrum. The uses and distinctive features of the proton NMR spectrum of the 2,2-dimethylpentane molecule explained. What does the H-1 proton NMR spectrum chemical shifts tell us about the structure and properties of the 2,2-dimethylpentane molecule? explaining the spin-spin proton coupling effects in the 1H NMR spectrum of 2,2-dimethylpentane. interpretation diagram explaining the proton splitting pattern produced from the n+1 rule and the theoretical ratio of chemical shift and values of intensities for the proton NMR spectrum lines of 2,2-dimethylpentane


Links associated with 2,2-dimethylpentane

The infrared spectrum of 2,2-dimethylpentane

The mass spectrum of 2,2-dimethylpentane

The C-13 NMR spectrum of 2,2-dimethylpentane

The chemistry of ALKANES 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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Infrared spectra of the isomers of C7H16

The infrared spectrum of heptane

The infrared spectrum of 2-methylhexane

The infrared spectrum of 3-methylhexane

The infrared spectrum of 3-ethylpentane

The infrared spectrum of 2,2-dimethylpentane

The infrared spectrum of 2,3-dimethylpentane

The infrared spectrum of 2,4-dimethylpentane

The infrared spectrum of 3,3-dimethylpentane

The infrared spectrum of 2,2,3-trimethylbutane

Mass spectra of the isomers of C7H16

The mass spectrum of heptane

The mass spectrum of 2-methylhexane

The mass spectrum of 3-methylhexane

The mass spectrum of 3-ethylpentane

The mass spectrum of 2,2-dimethylpentane

The mass spectrum of 2,3-dimethylpentane

The mass spectrum of 2,4-dimethylpentane

The mass spectrum of 3,3-dimethylpentane

The mass spectrum of 2,2,3-trimethylbutane

H-1 proton NMR spectra of ALKANES

1H NMR spectra of the isomers of C7H16

The H-1 NMR spectrum of heptane

The H-1 NMR spectrum of 2-methylhexane

The H-1 NMR spectrum of 3-methylhexane

The H-1 NMR spectrum of 3-ethylpentane

The H-1 NMR spectrum of 2,2-dimethylpentane

The H-1 NMR spectrum of 2,3-dimethylpentane

The H-1 NMR spectrum of 2,4-dimethylpentane

The H-1 NMR spectrum of 3,3-dimethylpentane

The H-1 NMR spectrum of 2,2,3-trimethylbutane

C-13 carbon-13 NMR spectra of ALKANES

13C NMR spectra of the isomers of C7H16

The C-13 NMR spectrum of heptane

The C-13 NMR spectrum of 2-methylhexane

The C-13 NMR spectrum of 3-methylhexane

The C-13 NMR spectrum of 3-ethylpentane

The C-13 NMR spectrum of 2,2-dimethylpentane

The C-13 NMR spectrum of 2,3-dimethylpentane

The C-13 NMR spectrum of 2,4-dimethylpentane

The C-13 NMR spectrum of 3,3-dimethylpentane

The C-13 NMR spectrum of 2,2,3-trimethylbutane

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