|
Interpreting the
1H NMR spectrum of 3,3-dimethylpentane
[Author
©
Dr
Phil 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 & AP honors chemistry courses: Molecular
spectroscopy - analysing
1H NMR spectrum of
3,3-dimethylpentane
[spectra updated
Mar 19th 2026 *]
email doc
brown
Re-edit 1H NMR
spectrum of CH3CH2C(CH3)2CH2CH3
This is a BIG
website, PLEASE take time to explore it
Links associated with
3,3-dimethylpentane
*
[privacy,
cookies & disclaimer policies]
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
Introductory note on the 1H NMR spectra of 3,3-dimethylpentane
Students and teachers please note my explanation of the
proton NMR spectrum of 3,3-dimethylpentane is designed for advanced, but
pre-university, chemistry courses.
The chemical shift
δ splitting pattern effects for
3,3-dimethylpentane are
confined to a proton spin-spin
coupling effects analysed using the n+1 rule for adjacent
non-equivalent proton fields (n is the number of neighbouring
protons in a non-equivalent different chemical environment for the
3,3-dimethylpentane molecule).
It is assumed that the integrated intensities of the
1H
NMR δ
chemical shifts give the ratio of the protons in the different
non-equivalent chemical environments of the 3,3-dimethylpentane molecule.
The most common solvent used for investigating the 1H NMR
spectrum of compounds like 3,3-dimethylpentane, is CDCl3 and other
deuterated solvents to avoid confusion with a 1H NMR
signal, 2D (2H) has a different NMR chemical
shift.
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 - 3,3-dimethylpentane here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 3,3-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 3,3-dimethylpentane molecule.
3,3-dimethylpentane C7H16
The molecular structure and
naming of alkanes
Interpreting the
H-1 NMR spectrum of
3,3-dimethylpentane
For relatively simple molecules, the low
resolution H-1 NMR spectrum of 3,3-dimethylpentane is NOT a good starting point
(low resolution diagram above).
Two of the 1H resonances of
3,3-dimethylpentane, for the two sets of methyl protons, are
very close together, and can only be resolved with a very
high resolution spectrometer.
So, theoretically, the 16 hydrogen atoms (protons) of
3,3-dimethylpentane can only occupy 3
different chemical environments.
CH3CH2C(CH3)2CH2CH3
Note the
proton ratio 6:6:4 of the 3 colours of the protons
in the 3 chemically different environments
Chemical shifts
(a) to (c) on the H-1 NMR
spectrum diagram for 3,3-dimethylpentane.
The high resolution 1H NMR
spectrum of 3,3-dimethylpentane
All low and high resolution spectra of
3,3-dimethylpentane
show 3 groups of proton resonances and in the 3 ratio expected from the
formula of 3,3-dimethylpentane (you would observe a proton ratio
of 3:3:2 for the three chemically different environments.
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of 3,3-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 3,3-dimethylpentane below.
So, using the chemical shifts and applying the
n+1 rule to
3,3-dimethylpentane
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
(a) 1H
Chemical shift 0.79 ppm, CH3 protons: CH3CH2C(CH3)2CH2CH3
All six
protons are equivalent to each other, in the same
chemical environment, giving the same 1-H NMR chemical
shift.
Theoretically, this 1H resonance is
split into a triplet by the neighbouring CH2
protons (n+1 = 3)
Evidence for the presence of a CH2 group
in the molecule of 3,3-dimethylpentane.
(b) 1H
Chemical shift 1.20 ppm: CH3CH2C(CH3)2CH2CH3
All four
protons are equivalent to each other, in the same
chemical environment, giving the same 1-H NMR chemical
shift.
Theoretically, this 1H resonance is
split into a quartet by the neighbouring CH3
protons (n+1 = 4), but it looks more complicated than
this on the spectrum diagram?
Evidence for the presence of a CH3 group
in the molecule of 3,3-dimethylpentane
(c) 1H
Chemical shift 0.80 ppm,
CH3 protons:CH3CH2C(CH3)2CH2CH3
All six
protons are equivalent to each other, in the same
chemical environment, giving the same 1-H NMR chemical
shift.
This resonance would not readily show
splitting because there are no protons on the
neighbouring carbon atom - a singlet is theoretically
observed.
Resonance
(a) and (c) are almost
identical and on the spectrum around ~0.80 ppm is an
overlap of a singlet and a triplet.
Key
points about the 1H NMR spectrum of 3,3-dimethylpentane
Structural
Overview: 3,3-Dimethylpentane
Molecular formula:
C7H16
- Quaternary carbon (C3)
has no hydrogen atoms.
- All protons are on
CH3
and CH2
groups.
- Symmetry
reduces the number of unique proton environments.
¹H NMR
Chemical Shift Table
| Proton
Environment |
Description |
Approx. δ
(ppm) |
Integration |
Notes |
| CH3–CH2–
(C1 & C5) |
Terminal methyl
groups next to CH2 |
~0.90,
0.79 ppm |
6H |
Equivalent |
| CH2–C(CH3)2–CH2
(C2 & C4) |
Methylene groups
adjacent to CH3
and quaternary C |
~1.30,
1.20 ppm |
4H |
Equivalent |
| CH3–C(CH3)2–
(C6 & C7) |
Methyl groups
bonded to quaternary carbon |
~0.85,
0.80 ppm |
6H |
Equivalent |
Total number of signals:
3
Total protons: 16
Integration ratio:
6 : 4 : 6
Sources: SpectraBase and
https://sdbs.db.aist.go.jp/
diagram 1H
δ ppm
spectral database of organic compounds
Common
Misconceptions
| Misconception |
Clarification |
| Each hydrogen gives a
separate peak |
Not true—equivalent
protons give one signal. |
| Quaternary carbon
contributes a signal |
No—no protons
on C3, so no ¹H signal. |
| All methyl groups
appear at the same shift |
Not always—chemical
environment affects δ. |
| More peaks = more
atoms |
Not necessarily—symmetry
reduces the number of signals. |
| Splitting always
occurs |
Not in simplified
spectra—many exam boards use idealized or
decoupled spectra. |
Exam
Revision Tips
- Draw the structure
and identify symmetry to group equivalent protons.
- Quaternary carbons
do not appear in ¹H NMR.
- Integration
reflects number of protons, not number of peaks.
- Chemical shift
for alkyl protons typically lies between 0.8–1.6 ppm.
- Practice with branched
alkanes—they often
hide symmetry and confuse peak counting.
- No splitting
in standard exam spectra unless explicitly shown.
Tips for
spotting equivalent methyl group protons in 1H NMR
e.g. 4 methyl groups in 2,2-dimethylpentane
- 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 (2,2-dimethylpentane) can lead to
equivalence.
- Use integration clues:
If two methyl groups give a single peak with integration of 6H (3
gives 9H), that's a strong hint they are equivalent.
- Compare with isomers:
Try contrasting with
2,2-dimethylpentane
with 3-methylhexane, where methyl
proton environments differ more clearly.
- Counting methyls as
separate signals:
Leads to overestimating the number of peaks in ¹H 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.
Practice
Question (Exam Style)
Question:
3,3-Dimethylpentane has the
molecular formula C7H16.
(a) Predict the number of signals in its ¹H NMR spectrum.
(b) Explain why this number is less than the number of hydrogen atoms.
(c) Estimate the chemical shift and integration for the methyl groups
attached to the quaternary carbon.
(d) Which environment gives rise to the signal at ~1.30 ppm?
Model
Answer
(a)
3 signals
(b) Due to symmetry, several hydrogen
atoms are chemically equivalent and give the same
signal.
- C1 ≡ C5 (CH3) → 6H
- C2 ≡ C4 (CH2)
→ 4H
- C6 ≡ C7 (on C3 there are 2 x CH3)
→ 6H
(c) The methyl groups on the quaternary carbon
appear around 0.85 ppm with integration of
6H.
(d) The signal at ~1.30 ppm corresponds to the
methylene (CH2) groups adjacent to the
quaternary carbon.
The splitting pattern from proton
spin-spin coupling effects is analysed using the n+1 rule for
adjacent non-equivalent proton fields (n is the number of
neighbouring protons in a non-equivalent different chemical
environment).
|
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 |
 |
 |
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 proton H-1 NMR spectra of 3,3-dimethylpentane, low resolution & high resolution proton
nmr spectra of 3,3-dimethylpentane, H-1 nmr spectrum of 3,3-dimethylpentane, understanding the
hydrogen-1 nmr spectrum of 3,3-dimethylpentane, explaining the line splitting patterns in the
high resolution H-1 nmr spectra of 3,3-dimethylpentane, revising the H-1 nmr spectrum of
3,3-dimethylpentane,
proton nmr of 3,3-dimethylpentane, ppm chemical shifts of the H-1 nmr spectrum of
3,3-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 3,3-dimethylpentane, how to work out the
number of chemically different protons in the structure of the
3,3-dimethylpentane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 3,3-dimethylpentane using the n+1 rule to explain the spin - spin coupling
spin
splitting in the proton nmr spectrum of 3,3-dimethylpentane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 3,3-dimethylpentane
examining the 1H nmr spectrum of 3,3-dimethylpentane analysing the 1-H nmr spectrum of
3,3-dimethylpentane how do you sketch and interpret the H-1 NMR spectrum of
3,3-dimethylpentane
interpreting interpretation of the 1H proton NMR spectrum of 3,3-dimethylpentane
formula
CH3CH2C(CH3)2CH2CH3 Molecular structure diagram of the
proton NMR diagram for the 1H NMR spectrum of 3,3-dimethylpentane. The proton ratio in the
1H NMR spectrum of 3,3-dimethylpentane. Deducing the number of different chemical
environments of the protons in the 3,3-dimethylpentane molecule from the 1H chemical shifts
in the hydrogen-1 NMR spectrum of 3,3-dimethylpentane. Analysing the high resolution 1H NMR
spectrum of 3,3-dimethylpentane. Analysing the low resolution 1H NMR spectrum of
3,3-dimethylpentane. You
may need to know the relative molecular mass of 3,3-dimethylpentane to deduce the molecular
formula from the proton ratio of the 1H NMR spectrum of 3,3-dimethylpentane. Revision notes
on the proton NMR spectrum of 3,3-dimethylpentane. Matching and deducing the structure of
the 3,3-dimethylpentane molecule from its hydrogen-1 NMR spectrum.
Proton NMR spectroscopy of aliphatic alkanes,
1H NMR spectra of 3,3-dimethylpentane, a structural isomer of molecular formula
C7H16
How do you interpret the H-1 NMR spectrum of
3,3-dimethylpentane How to interpret
the H-1 NMR spectrum of 3,3-dimethylpentane Explanatory diagram of the chemical
shifts of the 1H H-1 proton NMR spectrum of the
3,3-dimethylpentane
molecule in terms of its molecular structure. Listing data of all the chemical shift peaks in ppm in the
proton NMR spectrum of 3,3-dimethylpentane. How to explain the H-1 NMR spectrum of
3,3-dimethylpentane. The chemical shifts and integrated values of the proton ratios in the 1-H NMR
spectrum of the 3,3-dimethylpentane molecule. How to work out the molecular
structure of the 3,3-dimethylpentane molecule from its proton NMR spectrum. The uses
and distinctive features of the proton NMR spectrum of the
3,3-dimethylpentane
molecule explained. What does the H-1 proton NMR spectrum chemical
shifts tell us about the
structure and properties of the 3,3-dimethylpentane
molecule? explaining the spin-spin proton coupling effects in the 1H
NMR spectrum of 3,3-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
3,3-dimethylpentane
Links associated
with
3,3-dimethylpentane
The infrared spectrum of
3,3-dimethylpentane
The mass spectrum of
3,3-dimethylpentane
The C-13 NMR spectrum of
3,3-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)
ALL SPECTROSCOPY INDEXES
All Advanced Organic
Chemistry Notes
Use My Google search site box
Email doc b:
chem55555@hotmail.com
|
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
|
Website content © Dr
Phil Brown 2000+. All copyrights reserved on revision notes, images,
quizzes, worksheets etc. Copying of Doc Brown's pre-university
advanced level chemistry website material is NOT
permitted. Exam revision summaries & references to science course specifications
are unofficial. These organic chemistry revision notes on
spectroscopy are
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, US grade 11-12 AP honors
chemistry courses and they will also prove useful to
1st year undergraduate students of chemistry.
|
