Advanced Organic Chemistry: Carbon-13 NMR spectrum of 3,3-dimethylpentane

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Interpreting the Carbon-13 NMR spectrum of 3,3-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 C-13 NMR spectra of 3,3-dimethylpentane

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C-13 NMR spectroscopy - spectra index

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


13C NMR 3,3-dimethylpentane spectra note: Students and teachers please note that my explanation of the carbon-13 NMR spectrum of 3,3-dimethylpentane is designed for advanced, but pre-university, chemistry courses. The description does not involve the chemical shift δ spin-spin coupling effects for 3,3-dimethylpentane and the relative size of the carbon-13 NMR shifts does not give the ratio of the carbon atoms in the different non-equivalent chemical environments.

C7H16 C-13 nmr spectrum of 3,3-dimethylpentane analysis of chemical shifts ppm interpretation of 13C chemical shifts ppm of 3,3-dimethylpentane C13 13-C nmr doc brown's advanced organic chemistry revision notes 

TMS is the acronym for tetramethylsilane, formula Si(CH3)4, whose 13C atoms are arbitrarily given a chemical shift of 0.0 ppm. This is the 'standard' in 13C NMR spectroscopy and all other 13C resonances, called chemical shifts, are measured with respect to the TMS, and depend on the individual (electronic) chemical environment of the 13C atoms in an organic molecule - 3,3-dimethylpentane here.

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

As you can see from the diagram above there are 4 different chemical shift lines in the C-13 NMR spectrum of 3,3-dimethylpentane indicating 4 different chemical environments of the carbon atoms.

CH3CH2C(CH3)2CH2CH3

(Note the 4 different colours indicating the 4 different chemical environments of the carbon atoms in 3,3-dimethylpentane).

Chemical shifts (a) to (d) on the C-13 NMR spectrum diagram for 3,3-dimethylpentane.

Note there are three pairs of carbon atom in the same chemical environment (a-a, b-b and c-c) and will therefore give the same C-13 NMR chemical shift i.e. of 8.4, 33.8 and 26.2 ppm respectively.

Only the central carbon atom (d), has a unique chemical environment and with a chemical shift of 32.8

Both theses situations arise from the high symmetry of the 3,3-dimethylbutane molecule.

The carbon-13 NMR spectra a provides direct evidence of 4 different carbon atom environments for the 7 carbon atoms in the 3,3-dimethylpentane molecule, deduced from the presence of 4 different 13C chemical shifts (ppm).

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 C-13 NMR spectra of 3,3-dimethylpentane, C-13 nmr spectrum of 3,3-dimethylpentane, understanding the carbon-13 nmr spectrum of 3,3-dimethylpentane, explaining the line pattern in the high resolution C-13 nmr spectra of 3,3-dimethylpentane, revising the C-13 nmr spectrum of 3,3-dimethylpentane, ppm chemical shifts of the C-13 nmr spectrum of 3,3-dimethylpentane, how to construct the diagram of the C-13 nmr spectrum of 3,3-dimethylpentane, how to analyse the chemical shifts in the carbon-13 NMR spectrum of 3,3-dimethylpentane deducing the chemical environment of all the carbon atoms in 3,3-dimethylpentane examining the c13 nmr spectrum of  3,3-dimethylpentane analysing the 13-c nmr spectrum of 3,3-dimethylpentane how do you sketch and interpret the C-13 NMR spectrum of 3,3-dimethylpentane interpreting interpretation of the C-13 NMR spectrum of 3,3-dimethylpentane 13C NMR spectrum of 3,3-dimethylpentane CH3CH2C(CH3)2CH2CH3 Molecular structure diagram of the carbon-13 NMR diagram for the 13C NMR spectrum of 3,3-dimethylpentane. Deducing the number of different chemical environments of the carbon atoms in the 3,3-dimethylpentane molecule from the 13C chemical shifts in the carbon-13 NMR spectrum of 3,3-dimethylpentane. Revision notes on the carbon-13 NMR spectrum of 3,3-dimethylpentane. Matching and deducing the structure of the 3,3-dimethylpentane molecule from its 13C NMR spectrum. Carbon-13 NMR spectroscopy of aliphatic alkanes, 13C NMR spectra of 3,3-dimethylpentane, a structural isomer of molecular formula C7H16 How do you interpret the chemical shifts of the C-13 NMR spectrum of  3,3-dimethylpentane How to interpret the C-13 NMR spectrum of  3,3-dimethylpentane Explanatory diagram of the 13C C-13 carbon-13 NMR spectrum of the  number of different carbon atom environments in the  3,3-dimethylpentane molecule from its carbon-13 NMR spectrum to help work out the molecular structure of the  3,3-dimethylpentane molecule? The uses and distinctive features of the carbon-13 NMR spectrum of the  3,3-dimethylpentane molecule explained. What do the number and values of the chemical shifts from the c-13 carbon-13 NMR spectrum tell us about the  3,3-dimethylpentane molecule? explaining the decoupled carbon-13 NMR spectrum of  3,3-dimethylpentane  with a detailed interpretation diagram of all the C-13 chemical shifts and intensities


Links associated with 3,3-dimethylpentane

The infrared spectrum of 3,3-dimethylpentane

The mass spectrum of 3,3-dimethylpentane

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

The chemistry of ALKANES revision notes INDEX

C-13 NMR spectroscopy index

ALL SPECTROSCOPY INDEXES

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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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