|
The H-1
hydrogen-1 (proton) NMR spectrum of 2,2-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 2,2-dimethylpentane
email doc
brown
Use your
mobile phone or ipad etc. in 'landscape' mode
This is a BIG
website, you need to take time to explore it
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
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 shifts, called chemical shifts, depend on the
individual (electronic) chemical environment of the hydrogen atoms
in an organic molecule - 2,2-dimethylpentane here.
The chemical shifts quoted in ppm on the diagram of
the H-1 NMR spectrum of 2,2-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 2,2-dimethylpentane molecule.
2,2-dimethylpentane C7H16
Interpreting the
H-1 NMR spectrum of
2,2-dimethylpentane
For relatively simple molecules, the low
resolution H-1 NMR spectrum of 2,2-dimethylpentane is a good,
but limited starting point.
Theoretically, the 16 hydrogen atoms (protons) of
2,2-dimethylpentane occupy 4
different chemical environments so that the low resolution NMR
spectra should show 4 principal peaks of different H-1 NMR chemical shifts (diagram above for
2,2-dimethylpentane).
BUT, as you can see, you get only 2 principal
peaks in the integrated proton ratio observed of 3:1 for the CH3:CH2
proton ratio.
(CH3)3CCH2CH2CH3
Note the 'real' proton ratio 9:2:2:3 of the 4 colours of the protons
in the 4 chemically different environments
Chemical shifts (a) to (d) on the H-1 NMR
spectrum diagram for 2,2-dimethylpentane.
Although there are 16 hydrogen atoms in the molecule,
there are only 4 possible different chemical
environments for the hydrogen atoms in 2,2-dimethylpentane molecule.
The high resolution 1H NMR
spectrum of 2,2-dimethylpentane
The ppm quoted on the diagram represent the peak
of resonance intensity for a particular proton group in the
molecule of 2,2-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 2,2-dimethylpentane below.
So, using the chemical shifts and applying the
n+1 rule to
2,2-dimethylpentane
and make some predictions using some colour coding! (In problem
solving you work the other way round!)
(a) 1H
Chemical shift 0.86 ppm for the -C(CH3)3 protons: (CH3)3CCH2CH2CH3
Resonance (a) would not be readily
split, since no protons on the adjacent carbon atom on
the right - this theoretically gives a singlet.
(b) and (c) 1H
Chemical shift 1.18 ppm for the -CH2- protons: (CH3)3CCH2CH2CH3
These are almost identical, but
theoretically different - you would need very high
resolution spectra to sort them out.
(b) is split into a 1:2:1 triplet by the
neighbouring (c) CH2 protons (n+1 = 3).
Evidence of a CH2 group
in the molecule.
(c) is split into a sextet by the
neighbouring CH2 and CH3 protons
(n+1 =6).
Evidence of a CH2-C-CH3
grouping in the molecule.
(d) 1H
Chemical shift 0.88 ppm for the 'lone' CH3 group: (CH3)3CCH2CH2CH3
(d) is split into a 1:2:1 triplet by the
neighbouring (c) CH2 protons (n+1 = 3).
Evidence of a 2nd CH2
group in the molecule.
Very similar to 1H resonance (a) and
you would need very high resolution spectra to resolve (a)
and (d).
|
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 2,2-dimethylpentane, low resolution & high resolution proton
nmr spectra of 2,2-dimethylpentane, H-1 nmr spectrum of 2,2-dimethylpentane, understanding the
hydrogen-1 nmr spectrum of 2,2-dimethylpentane, explaining the line splitting patterns in the
high resolution H-1 nmr spectra of 2,2-dimethylpentane, revising the H-1 nmr spectrum of
2,2-dimethylpentane,
proton nmr of 2,2-dimethylpentane, ppm chemical shifts of the H-1 nmr spectrum of
2,2-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 2,2-dimethylpentane, how to work out the
number of chemically different protons in the structure of the
2,2-dimethylpentane organic
molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR
spectrum of 2,2-dimethylpentane using the n+1 rule to explain the spin - spin coupling ine
splitting in the proton nmr spectrum of 2,2-dimethylpentane deducing the nature of the protons
from the chemical shifts ppm in the H-1 nmr spectrum of 2,2-dimethylpentane
examining the 1H nmr spectrum of 2,2-dimethylpentane analysing the 1-H nmr spectrum of
2,2-dimethylpentane how do you sketch and interpret the H-1 NMR spectrum of
2,2-dimethylpentane
interpreting interpretation of the 1H proton NMR spectrum of 2,2-dimethylpentane
(CH3)3CCH2CH2CH3 Molecular structure diagram of the
proton NMR diagram for the 1H NMR spectrum of 2,2-dimethylpentane. The proton ratio in the
1H NMR spectrum of 2,2-dimethylpentane. Deducing the number of different chemical
environments of the protons in the 2,2-dimethylpentane molecule from the 1H chemical shifts
in the hydrogen-1 NMR spectrum of 2,2-dimethylpentane. Analysing the high resolution 1H NMR
spectrum of 2,2-dimethylpentane. Analysing the low resolution 1H NMR spectrum of
2,2-dimethylpentane. You
may need to know the relative molecular mass of 2,2-dimethylpentane to deduce the molecular
formula from the proton ratio of the 1H NMR spectrum of 2,2-dimethylpentane. Revision notes
on the proton NMR spectrum of 2,2-dimethylpentane. Matching and deducing the structure of
the 2,2-dimethylpentane molecule from its hydrogen-1 NMR spectrum.
Proton NMR spectroscopy of aliphatic alkanes,
1H NMR spectra of 2,2-dimethylpentane, a structural isomer of molecular formula
C7H16
Links associated
with 2,2-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
TOP OF PAGE
|
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
|
|
