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Interpreting the infrared
spectrum of 3,3-dimethylpentane
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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 infrared spectra of 3,3-dimethylpentane
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Infrared spectroscopy - spectra index
See also
comparing the
1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16
Spectra obtained from a liquid film of 3,3-dimethylpentane. The right-hand part of the of the
infrared spectrum of 3,3-dimethylpentane, wavenumbers
~1500 to 400
cm-1 is considered the fingerprint region for the
identification of 3,3-dimethylpentane and most organic compounds. It is due to a unique set
of complex overlapping vibrations of the atoms of the molecule of
3,3-dimethylpentane.
3,3-dimethylpentane C7H16
Interpretation of
the infrared spectrum of 3,3-dimethylpentane
The most prominent infrared absorption lines of
3,3-dimethylpentane
Strong C-H stretching vibration absorptions at
wavenumbers 2940 to 2880 cm-1 for the CH2 and
CH3 groups in 3,3-dimethypentane.
Several strong C-H deformation vibration absorptions
at wavenumbers 1480 to 1365 cm-1 for the CH2
and CH3 groups in 3,3-dimethypentane.
Several strong C-C skeletal vibration
absorptions associated with a C-(CH3)2
group occur at wavenumbers 840 to 790 and 1175 to 1140 cm-1.
There are no specific characteristic lines for
alkanes like heptane because C-C and C-H vibrations are common to so
many organic molecules and alkanes like 3,3-dimethypentane have no functional
group that gives a characteristic vibration.
The absence of other specific functional group bands
will show that a particular functional group is absent from the
3,3-dimethylpentane
molecular
structure.
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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 image and diagram explaining the infrared spectrum
of 3,3-dimethylpentane, complete infrared absorption spectrum of
3,3-dimethylpentane, comparative spectra of
3,3-dimethylpentane, prominent peaks/troughs for identifying functional groups in the infrared spectrum of
3,3-dimethylpentane,
important wavenumber values in cm-1 for peaks/troughs in the infrared spectrum
of 3,3-dimethylpentane, revision of infrared spectroscopy of 3,3-dimethylpentane, fingerprint region analysis of
3,3-dimethylpentane, how to identify 3,3-dimethylpentane from its infrared spectrum, identifying organic
compounds like 3,3-dimethylpentane from their infrared spectrum,
how to analyse the absorption bands in the infrared spectrum of
3,3-dimethylpentane detection of no functional groups in the
3,3-dimethylpentane molecule example of the infrared spectrum of a
molecule like 3,3-dimethylpentane with no functional group
interpreting interpretation of the infrared spectrum of 3,3-dimethylpentane shows presence
of no functional groups
CH3CH2C(CH3)2CH2CH3 Stick diagram of the relative abundance
of ionised fragments in the fingerprint pattern of the mass spectrum of
xyz. Table of the m/e m/z values and formula of the ionised fragments in the
mass spectrum of xyz. The m/e m/z value of the molecular ion peak in the
mass spectrum of xyz. The m/e m/z value of the base ion peak in the
mass spectrum of xyz. Possible examples of equations showing the formation
of the ionised fragments in xyz. Revision notes on the mass spectrum of xyz.
Matching and deducing the structure of the xyz molecule from its mass
spectrum. Mass spectroscopy of
aliphatic alkanes,
mass spectra of xyz, a structural isomer of molecular formula
C7H16
Links associated with 3,3-dimethylpentane
The chemistry of ALKANES
revision notes INDEX
Infrared spectroscopy index
ALL SPECTROSCOPY INDEXES
All Advanced Organic
Chemistry Notes
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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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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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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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