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Interpreting and interpreting the Carbon-13 NMR spectrum of heptane
[Author
©
Dr
Phil Brown GRIC, PhD:
Doc Brown's advanced level
organic chemistry exam revision notes suitable for students of UK A
level chemistry courses & US K12 grade 11, grade 12 and AP honors
chemistry courses:
Molecular spectroscopy
analysis of
heptane
[spectra page updated
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13C spectrum
CH3(CH2)5CH3
Links associated with heptane
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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
Introductory note on the 13C NMR spectrum of heptane
Students and teachers please note that my explanation of the
carbon-13 NMR spectrum of heptane is designed for advanced, but
pre-university, chemistry courses.
The description does not involve
the chemical shift δ
spin-spin coupling effects for heptane 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 of the heptane molecule.
The most common solvent used for investigating the C13 NMR
spectrum of compounds like heptane, is CDCl3 and other
deuterated solvents.
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 shifts, called chemical shifts, depend on the
individual (electronic) chemical environment of the 13C atoms in
an organic molecule - heptane here.
Heptane,
C7H16 , CH3(CH2)5CH3
,
,
an alkane
For more
see The molecular structure,
classification and
naming of alkanes
Interpreting the C-13 NMR spectrum of heptane
As you can see from the diagram above there are
4 different 13C chemical shift lines in the C-13 NMR spectrum of
heptane
indicating 4 different chemical environments of the carbon atoms.
CH3CH2CH2CH2CH2CH2CH3
(Note the 4 colours indicating the
4 different chemical environments of the carbon atoms in heptane).
Chemical shifts
(a) to (d) on the C-13 NMR
spectrum diagram for heptane.
The carbon-13 NMR spectra a provides direct evidence of
4 different carbon atom environments for the 7 carbon atoms in the
symmetrical
heptane molecule,
deduced from the presence of 4 different 13C chemical
shifts (ppm).
Adding D2O to the sample under investigation,
dissolved in CDCl3, makes no difference to
the 13C NMR spectrum of heptane because
13C NMR does not detect proton resonances!
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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. |
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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) |
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heptane |
|
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4 δ: proton ratio: 3:2:2:1 (6:4:4:2 in the molecule) |
4 δ shifts |
|
2-methylhexane |
 |
 |
6 δ: proton ratio :
6:3:2:2:2:1 |
6 δ shifts |
|
3-methylhexane |
 |
 |
7 δ: proton ratio:
3:3:3:2:2:2:1 (simplification) ! |
7
δ shifts |
|
3-ethylpentane |
 |
 |
3 δ: proton ratio:
9:6:1 |
3 δ
shifts |
|
2,2-dimethylpentane |
 |
 |
4 δ: proton ratio:
9:3:2:2 |
5 δ shifts |
|
2,3-dimethylpentane |
 |
 |
6 δ: proton ratio:
6:3:3:2:1:1 (simplification) ! |
6 δ
shifts (simplification) !!! |
|
2,4-dimethylpentane |
 |
 |
3 δ: proton ratio:
12:2:2 |
3 δ
shifts |
|
3,3-dimethylpentane |
 |
 |
3 δ: proton ratio:
3:3:2 (6:4:4 in the molecule) |
4 δ
shifts |
|
2,2,3-trimethylbutane |
 |
 |
3 δ: proton ratio:
9:6:1 |
4 δ shifts |
Key words & phrases:
C7H16 Interpreting the C-13 NMR spectra of
heptane, C-13 nmr spectrum of heptane, understanding the
carbon-13 nmr spectrum of heptane, explaining the line pattern in the high
resolution C-13 nmr spectra of heptane, revising the C-13 nmr spectrum of
heptane, ppm
chemical shifts of the C-13 nmr spectrum of heptane, how to construct the diagram of
the C-13 nmr spectrum of heptane, how to analyse the chemical shifts in the
carbon-13 NMR spectrum of heptane deducing the chemical environment of all the
carbon atoms in heptane examining the c13 nmr spectrum of heptane analysing the
13-c nmr spectrum of heptane how do you sketch and interpret the C-13 NMR spectrum
of heptane interpreting interpretation of the C-13 NMR spectrum of heptane
13C NMR spectrum of heptane Molecular structure diagram of the
carbon-13 NMR diagram for the 13C NMR spectrum of heptane. Deducing the number
of different chemical environments of the carbon atoms in the heptane molecule
from the 13C chemical shifts in the carbon-13 NMR spectrum of heptane. Revision
notes on the carbon-13 NMR spectrum of heptane. Matching and deducing the
structure of the heptane molecule from its 13C NMR spectrum.
Carbon-13 NMR spectroscopy of aliphatic alkanes,
13C NMR spectra of heptane, a structural isomer of molecular formula C7H16
How do you interpret the chemical shifts of the C-13 NMR spectrum
of heptane How to interpret the C-13 NMR spectrum of heptane Explanatory diagram of the 13C C-13 carbon-13 NMR spectrum of the number of different carbon atom
environments in the heptane molecule from its carbon-13 NMR spectrum to
help work out the molecular structure of the heptane molecule? The uses
and distinctive features of the carbon-13 NMR spectrum of the
heptane
molecule explained. What do the number and values of the chemical
shifts from the c-13 carbon-13 NMR spectrum tell us about the
heptane
molecule? explaining the decoupled carbon-13 NMR spectrum of heptane
with a detailed interpretation diagram of all the C-13 chemical shifts and
intensities
Links associated
with
heptane
The infrared
spectrum of heptane
The H-1 NMR
spectrum of heptane
The mass
spectrum of heptane
The chemistry of ALKANES
revision notes INDEX
C-13
NMR spectroscopy index
ALL SPECTROSCOPY INDEXES
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Chemistry Notes
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Index of my advanced
(pre-college/university) organic
chemistry revision notes
Index
of all my spectroscopy pages
Index
of all my isomerism pages
The chemistry of
alkanes and the petrochemical
industry
The
chemistry of alkenes
The
chemistry of haloalkanes
The
chemistry of
alcohols
The chemistry of
aldehydes
and ketones The
chemistry of carboxylic acids and derivatives The chemistry of
organo-nitrogen compounds
The chemistry of
aromatic compounds
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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
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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
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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
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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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permitted. Exam revision summaries & references to science course specifications
are unofficial. These organic chemistry revision notes on
spectroscopy (13C NMR spectra of heptane, detailed analysis,
diagnostic features, data analysed, useful infrared spectra exam revision
comments)
suitable for use of pre-university students studying AQA advanced level
chemistry, Edexcel advanced level chemistry, OCR advanced level
chemistry, IB advanced level chemistry, WJEC (Eduqas) advanced level
chemistry, CIE advanced level chemistry, CCEA advanced level chemistry, US grade 11-12 AP honors
chemistry courses and they will also prove useful to
1st year undergraduate students of chemistry.
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