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Interpreting
13C NMR spectrum of
2,2-dimethylpentane
[Author
©
Dr WP Brown 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 - analysing the
13C NMR spectrum of
2,2-dimethylpentane
[updated
October 29th 2025]
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CH3CH2CH2C(CH3)3
Links associated with 2,2-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
Introductory note on the 13C NMR spectrum of 2,2-dimethylpentane
Students and teachers please note that my explanation of the
carbon-13 NMR spectrum of 2,2-dimethylpentane is designed for advanced, but
pre-university, chemistry courses.
The description does not involve
the chemical shift δ
spin-spin coupling effects for 2,2-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 of the
2,2-dimethylpentane molecule.
The most common solvent used for investigating the C13 NMR
spectrum of compounds like 2,2-dimethylpentane, 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 resonances, called chemical shifts, depend on the
individual (electronic) chemical environment of the 13C atoms in
an organic molecule - 2,2-dimethylpentane here.
2,2-dimethylpentane C7H16
The molecular structure and
naming of alkanes
Interpreting the C-13 NMR spectrum of 2,2-dimethylpentane
As you can see from the diagram above there are
5 different chemical shift lines in the C-13 NMR spectrum of
2,2-dimethylpentane
indicating 5 different chemical environments of the carbon atoms.
(CH3)3CCH2CH2CH3
(Note the 5 different colours indicating the
5 different chemical environments of the carbon atoms in
2,2-dimethylpentane).
13C NMR chemical shifts
(a) to (e) on the C-13 NMR
spectrum diagram for 2,2-dimethylpentane.
The carbon atoms of the three methyl groups of the
C(CH3)3 grouping are all chemically equivalent to
each other in the 2,2-dimethylpentane molecule i.e. they occupy
the same chemical environment, and so give the same C-13 NMR
chemical shift.
The carbon-13 NMR spectra a provides direct evidence of
5 different carbon atom environments (5 different 13C chemical
shifts observed) for the 7 carbon atoms in the
2,2-dimethylpentane molecule,
deduced from the presence of 5 different 13C chemical
shifts (ppm).
Key
points about the 13C NMR spectrum of 2,2-dimethypentane
2,2-Dimethylpentane
shows five distinct ¹³C NMR signals due to symmetry, all in the alkane
region (~10–40 ppm).
The
spectrum highlights equivalent methyl and methylene carbons, with the
quaternary carbon appearing furthest downfield.
Key ¹³C NMR
Features of 2,2-Dimethylpentane
This branched alkane (C7H16)
contains seven carbon atoms but only five unique
carbon environments due to symmetry. All signals appear in the
upfield region typical of saturated hydrocarbons.
| Carbon Type |
Chemical Shift (ppm) |
Environment |
Notes |
| CH3 (C5) |
~14–15,
15.1 ppm |
Terminal methyl |
Single methyl |
| CH3 (C2
methyls) |
~22–23,
29.5 ppm |
3 methyls |
Equivalent trio |
| CH₂ (C3, C4) |
~27–30,
17.9 ppm |
Methylene C4 |
Slightly different shifts if resolved |
| CH (C2) |
~35–38,
47.0 ppm |
Methylene C3 |
Attached to two methyls and two CH₂s |
| C (C2 central) |
~40–45,
30.4 ppm |
Quaternary carbon (C(CH3)3) |
Most deshielded due to branching |
Sources:
Master Organic Chemistry,
Organic Chemistry Data
https://sdbs.db.aist.go.jp/
diagram 13C
δ ppm spectral database of
organic compounds
Common
Misconceptions in ¹³C NMR Interpretation
- Expecting seven signals for seven
carbons: Symmetry reduces the
number of observable signals.
- Misidentifying quaternary carbons:
These appear downfield (~40–50 ppm) but lack attached protons.
- Assuming all methyls are
equivalent: Only the two on C2
are equivalent; terminal methyls are distinct but may overlap.
- Ignoring chemical shift ranges:
Alkanes typically appear between 10–50 ppm; shifts above this suggest
unsaturation or electronegative atoms.
Exam Revision Tips
(AQA, Edexcel, OCR, WJEC, CCEA, CIE, IB, AP)
- Count environments, not atoms:
Use symmetry to determine the number of signals.
- Draw and label the molecule:
Helps visualize equivalent carbons and predict signal count.
- Know typical shift ranges:
- CH3: ~10–25 ppm
- CH2: ~20–40 ppm
- CH: ~30–50 ppm
- C (quaternary): ~35–50 ppm
- Practice with spectra:
Compare linear versus branched alkanes to understand how branching affects
shifts and signal count.
Tips for spotting
equivalent methyl group carbons in 13C NMR
e.g. 4 methyl groups on C2 of 2,2-dimethypentane
- Check for identical attachments:
If two or more methyl groups are bonded to the same carbon and that carbon is not
chiral, they are usually equivalent.
- Look for symmetry: Even
partial symmetry (like in
2,2-dimethylpentane) can lead to equivalence.
- Use integration clues:
If two methyl groups give a single peak with integration of 6H, that’s a
strong hint they’re equivalent.
- Compare with isomers:
Try contrasting with
2,2-dimethylpentane with
3-methylhexane, where methyl
carbon environments differ more clearly.
- Counting methyls as separate
signals: Leads to
overestimating the number of peaks in ¹³C NMR spectra.
- Assuming all methyls are
equivalent: Not true in
asymmetric or chiral environments.
- Ignoring branching effects:
Branching can create or remove equivalence depending on the substitution
pattern.
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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) |
|
heptane |
 |
 |
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
2,2-dimethylpentane, C-13 nmr spectrum of 2,2-dimethylpentane, understanding the
carbon-13 nmr spectrum of 2,2-dimethylpentane, explaining the line pattern in the high
resolution C-13 nmr spectra of 2,2-dimethylpentane, revising the C-13 nmr spectrum of
2,2-dimethylpentane, ppm
chemical shifts of the C-13 nmr spectrum of 2,2-dimethylpentane, how to construct the diagram of
the C-13 nmr spectrum of 2,2-dimethylpentane, how to analyse the chemical shifts in the
carbon-13 NMR spectrum of 2,2-dimethylpentane deducing the chemical environment of all the
carbon atoms in 2,2-dimethylpentane examining the c13 nmr spectrum of
2,2-dimethylpentane analysing the
13-c nmr spectrum of 2,2-dimethylpentane how do you sketch and interpret the C-13 NMR spectrum
of 2,2-dimethylpentane interpreting interpretation of the C-13 NMR spectrum of
2,2-dimethylpentane
13C NMR spectrum of 2,2-dimethylpentane
(CH3)3CCH2CH2CH3 Molecular structure diagram of the
carbon-13 NMR diagram for the 13C NMR spectrum of 2,2-dimethylpentane. Deducing the number
of different chemical environments of the carbon atoms in the
2,2-dimethylpentane molecule
from the 13C chemical shifts in the carbon-13 NMR spectrum of
2,2-dimethylpentane. Revision
notes on the carbon-13 NMR spectrum of 2,2-dimethylpentane. Matching and deducing the
structure of the 2,2-dimethylpentane molecule from its 13C NMR spectrum.
Carbon-13 NMR spectroscopy of aliphatic alkanes,
13C NMR spectra of 2,2-dimethylpentane, a structural isomer of molecular formula
C7H16
How do you interpret the chemical shifts of the C-13 NMR spectrum
of 2,2-dimethylpentane How to interpret the C-13 NMR spectrum of
2,2-dimethylpentane Explanatory diagram of the 13C C-13 carbon-13 NMR spectrum of the number of different carbon atom
environments in the 2,2-dimethylpentane molecule from its carbon-13 NMR spectrum to
help work out the molecular structure of the
2,2-dimethylpentane molecule? The uses
and distinctive features of the carbon-13 NMR spectrum of the
2,2-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
2,2-dimethylpentane
molecule? explaining the decoupled carbon-13 NMR spectrum of
2,2-dimethylpentane
with a detailed interpretation diagram of all the C-13 chemical shifts and
intensities
Links associated
with
2,2-dimethylpentane
The infrared spectrum of
2,2-dimethylpentane
The mass spectrum of
2,2-dimethylpentane
The H-1 NMR spectrum of
2,2-dimethylpentane
The chemistry of ALKANES
revision notes INDEX
C-13
NMR spectroscopy index
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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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