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Advanced Organic Chemistry: 1H NMR spectrum of 2,3-dimethylpentane

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The H-1 hydrogen-1 (proton) NMR spectrum of 2,3-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 2,3-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

C7H16 low and high resolution 1H proton nmr spectrum of 2,3-dimethylpentane analysis interpretation of chemical shifts ppm spin spin line splitting diagram H1 H-1 nmr for 2,3-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 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 - 2,3-dimethylpentane here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of 2,3-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 2,3-dimethylpentane molecule.

2,3-dimethylpentane C7H16 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, classification and naming of alkanes

Interpreting the H-1 NMR spectrum of 2,3-dimethylpentane

(CH3)2CHCH(CH3)CH2CH3

From the structural formula, you might expect the 16 protons to occupy 6 different chemical environments in the ratio 6:1:1:3:2:3.

Apparently this is not the case, and protons a1 and a2 are not equivalent despite the fact that the two methyl groups are attached to the same CH group carbon atom, but giving two different chemical shifts.

Not only that, the two protons e1 an e2, on the same carbon atom, are also not equivalent, giving two different chemical shifts.

So, is this due to the effect of the chiral carbon atom of proton c giving rise to R/S isomers with different sets of chemical shifts?

I think this is a university level situation, so I'm leaving it at that, as My advanced organic chemistry notes are designed for pre-university students.

I would value other opinions on interpreting the 1H NMR spectrum of 2,3-dimethylpentane.


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 2,3-dimethylpentane, low resolution & high resolution proton nmr spectra of 2,3-dimethylpentane, H-1 nmr spectrum of 2,3-dimethylpentane, understanding the hydrogen-1 nmr spectrum of 2,3-dimethylpentane, explaining the line splitting patterns in the high resolution H-1 nmr spectra of 2,3-dimethylpentane, revising the H-1 nmr spectrum of 2,3-dimethylpentane, proton nmr of 2,3-dimethylpentane, ppm chemical shifts of the H-1 nmr spectrum of 2,3-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 2,3-dimethylpentane, how to work out the number of chemically different protons in the structure of the 2,3-dimethylpentane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 2,3-dimethylpentane using the n+1 rule to explain the spin - spin coupling ine splitting in the proton nmr spectrum of 2,3-dimethylpentane deducing the nature of the protons from the chemical shifts ppm in the H-1 nmr spectrum of 2,3-dimethylpentane examining the 1H nmr spectrum of  2,3-dimethylpentane analysing the 1-H nmr spectrum of 2,3-dimethylpentane how do you sketch and interpret the H-1 NMR spectrum of 2,3-dimethylpentane interpreting interpretation of the 1H proton NMR spectrum of 2,3-dimethylpentane (CH3)2CHCH(CH3)CH2CH3 Molecular structure diagram of the proton NMR diagram for the 1H NMR spectrum of 2,3-dimethylpentane. The proton ratio in the 1H NMR spectrum of 2,3-dimethylpentane. Deducing the number of different chemical environments of the protons in the 2,3-dimethylpentane molecule from the 1H chemical shifts in the hydrogen-1 NMR spectrum of 2,3-dimethylpentane. Analysing the high resolution 1H NMR spectrum of 2,3-dimethylpentane. Analysing the low resolution 1H NMR spectrum of 2,3-dimethylpentane. You may need to know the relative molecular mass of 2,3-dimethylpentane to deduce the molecular formula from the proton ratio of the 1H NMR spectrum of 2,3-dimethylpentane. Revision notes on the proton NMR spectrum of 2,3-dimethylpentane. Matching and deducing the structure of the 2,3-dimethylpentane molecule from its hydrogen-1 NMR spectrum. Proton NMR spectroscopy of aliphatic alkanes, 1H NMR spectra of 2,3-dimethylpentane, a structural isomer of molecular formula C7H16


Links associated with 2,3-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)

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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

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

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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