|
Doc Brown's
Advanced
Organic Chemistry: Part 14.7:
Isomers and extra notes on their properties and uses
The 5
constitutional-structural chain isomers of molecular formula C6H14
[Author
©
Dr
Phil Brown PhD: Doc
Brown's advanced level organic chemistry exam revision notes suitable
for students of UK advanced level chemistry courses, IB advanced
chemistry & US K12 grades 11-12 and AP honors chemistry courses: Molecular
spectroscopy and analysing the isomers of C6H14
[page updated Mar
1st
2026 *]
Associated organic chemistry page links
Index of sets of isomers for a given
molecular formula
email doc
brown - comments - query?
*
[privacy policy, cookies
and disclaimer]
This is a big chemistry website, please allow time
to explore it
Sub-index for this page on the isomers of
C6H14
(a)
Introduction to the isomers of C6H14
(b)
Details of the 5 constitutional isomers of C6H14
(c)
Summary of key points and extra notes on the isomers of molecular
formula C6H14
(d)
Learning objectives - questions to be answered?
(e)
Practise exam questions based on the isomers of
molecular formula C6H14
(a)
Introduction to the isomers of C6H14
The 5
alkane constitutional structural chain isomers of molecular formula C6H14
(Mr = 86)
Percent composition of
C6H14 based on atomic masses C= 12.01 H =
1.01 and Mr(C6H14) = 86.20
Element composition (to two dp): carbon =
83.60% hydrogen = 16.40%
Empirical formula = C3H7 and molecular
formula = C6H14
Structural isomerism
includes carbon chain variation (usually need a minimum of 4 C atoms), change in
position of a substituent or functional group and functional group isomerism
where the atoms have a different configuration, usually with significant
differences in chemical and physical properties.
Only carbon chain structural isomerism
applies to the isomers of C6H14.
Stereoisomerism is where
molecules have the same basic constitutional structural formula, but isomers
differ in the 2D/3D arrangement of the atoms. Neither types apply to the isomers
of C6H14.
E/Z
stereoisomerism was called 'geometrical isomerism' e.g. cis
and trans isomers of alkenes or disubstituted cyclic alkanes
where there are 3D spatial variations that are not mirror images and not super
imposable.
R/S
stereoisomerism was called 'optical isomerism', the pairs of
isomers are called enantiomers which are 3D non-superimposable
mirror image forms of the molecule. The molecule must have a chiral centre
(a stereocentre), that is an asymmetric carbon atom with four
different atoms/groups attached to it.
No E/Z or R/S isomers are possible
for molecular formula C6H14
NOTE
They are all open chain aliphatic
compounds of the alkane series of hydrocarbons.
The isomerism arises from the different
arrangements of the carbon atoms - from linear to highly
branched formations.
Note that many of
the structural formulae of the alkenes are
abbreviated/condensed.
e.g. CH3CH2CH2CH2CH2CH2
instead of CH3-CH2-CH2-CH2-CH2-CH2
No alkenes or
cycloalkane isomers are possible for molecular formula
C6H14
(b)
Details of the 5 constitutional isomers of C6H14
They are all saturated alkane isomers
(1)
or
 abbreviated structural formula for
hexane
(normal or n-hexane), and the linear skeletal formula is
Number of low resolution
NMR chemical shift
δ
signal peaks: 3 1H
and 3 13C
(email
if disagree?)
1H NMR ratio of peaks: 6
(3+3) : 4 (2+2) : 4
(2+2) = 3 : 2
: 2 (for equivalent protons)
See also spectra that can distinguish one C6H14
isomer from another
Spectra links for all 5
isomers of C6H14
The infrared spectrum of hexane
The infrared spectrum of
2-methylpentane
The infrared spectrum of
3-methylpentane
The infrared spectrum of
2,2-dimethylbutane
The infrared spectrum of
2,3-dimethylbutane
The mass spectrum of hexane
The mass spectrum of
2-methylpentane
The mass spectrum of
3-methylpentane
The mass spectrum of
2,2-dimethylbutane
The mass spectrum of
2,3-dimethylbutane
The H-1 NMR spectrum of hexane
The H-1 NMR spectrum of
2-methylpentane
The H-1 NMR spectrum of
3-methylpentane
The H-1 NMR spectrum of
2,2-dimethylbutane
The H-1 NMR spectrum of
2,3-dimethylbutane
The C-13 NMR spectrum of hexane
The C-13 NMR spectrum of
2-methylpentane
The C-13 NMR spectrum of
3-methylpentane
The C-13 NMR spectrum of
2,2-dimethylbutane
The C-13 NMR spectrum of
2,3-dimethylbutane
Index of 1H NMR spectra organic
compounds
and
Index of 13C NMR spectra organic
compounds
(2)
 or
 are abbreviated structural formula for
2-methylpentane (prefix numbers
definitely needed), and skeletal formula is
The simplest
branching possible for carbon chain structural
isomerism.
A positional
isomer based on the methyl substituent in pentane.
Number of low resolution
NMR chemical shift
δ
signal peaks: 5 1H
and 5 13C
(email
if disagree?)
1H NMR ratio of peaks: 6
(3+3) : 1 : 2 : 2
: 3 (for equivalent protons)
See spectra links for all
5 isomers of C6H14
(3)
 or
 are abbreviated structural formula for
3-methylpentane, and the skeletal
formula is
A positional
isomer based on the methyl substituent in pentane.
Number of low resolution
NMR chemical shift
δ
signal peaks: 4 1H
and 4 13C
(email
if disagree?)
1H NMR ratio of peaks: 6 : 4 : 1 : 3 (for equivalent protons)
See spectra links for all
5 isomers of C6H14
(4)
 or
 are abbreviated structural formula for
2,2-dimethylbutane and the skeletal
formula is
in which the carbon chain is even more branched.
A positional
isomer based on the methyl substituents in butane.
Number of low resolution
NMR chemical shift
δ
signal peaks: 3 1H
and 4 13C
(email
if disagree?)
1H NMR ratio of peaks: 9
(3x3) : 2 : 3 (for equivalent protons)
See spectra links for all
5 isomers of C6H14
(5)
 or  are abbreviated structural formula for
2,3-dimethylbutane, and the skeletal
formula is
, highly branched, but a very symmetrical molecule.
A positional
isomer based on the methyl substituents in butane.
Number of low resolution
NMR chemical shift
δ
signal peaks: 2 1H
and 2 13C
(email
if disagree?)
1H NMR ratio of peaks: 12
(4x3) : 2 (1+1) = 6 : 1 (for equivalent protons)
See spectra links for all
5 isomers of C6H14
(c) Summary of key points and extra notes on the isomers of molecular
formula C6H14
These isomers are based on C6H14
(hexane), a saturated hydrocarbon (alkane) with no rings or double bonds,
meaning no functional group or geometrical isomerism, only
carbon chain isomerism.
Types
of Isomerism for molecular formula C6H14
|
Type
of Isomerism |
Isomer
Examples |
Explanation |
|
Chain
Isomerism and positional isomerism of the methyl groups
|
Hexane,
2-Methylpentane, 3-Methylpentane, |
Varying carbon
branching—same molecular formula, different skeletons. |
|
2,3-Dimethylbutane, 2,2-Dimethylbutane |
Branching
increases → compact structure, lower boiling points. |
|
Conformational Isomerism |
All isomers |
Rotation around
C–C sigma bonds leads to staggered/eclipsed conformers. |
There are 5 constitutional isomers
of C6H14—each
with a unique connectivity pattern.
Physical Property Differences between the isomers molecular formula C6H14
|
Isomer |
Boiling Point (°C) |
Trend
Explanation |
|
n-Hexane |
~69 |
Straight-chain →
greater surface area → stronger London forces. |
|
2-Methylpentane |
~60 |
Slight branching
reduces surface contact. |
|
3-Methylpentane |
~63 |
Moderately
branched. |
|
2,3-Dimethylbutane |
~58 |
Highly branched →
weakest dispersion forces. |
|
2,2-Dimethylbutane |
~49 |
Most branched →
lowest boiling point. |
Density and melting points also vary due to
packing efficiency—less ordered structures tend to have lower
melting points.
Chemical Properties of the isomers molecular formula C6H14
As saturated alkanes, there are lots of chemical similarities
between the isomers:
-
Low reactivity under normal conditions.
-
Undergo free radical substitution (e.g.
halogenation with Cl2 or Br2 under UV).
-
No addition reactions (no C=C).
-
Resistant to oxidation unless under strong conditions.
Examples of the Industrial and Practical Uses of the isomers molecular formula C6H14
|
Isomer
Type |
Use/Application |
|
n-Hexane |
Solvent in labs
and industry (e.g. oil extraction). |
|
Branched
isomers |
Fuels and fuel
additives—higher octane ratings. |
|
General C6H14
mix |
Blended into
gasoline → energy-dense hydrocarbons. |
More branching → higher octane rating, more
desirable in fuel applications.
Common
Misconceptions the isomers molecular formula C6H14
(see also below)
-
"All alkanes are the same": Nope—branching
drastically impacts volatility and combustion.
-
"Hexane means one compound": “Hexane” often
refers to a mix of isomers unless specified.
-
"Can show E/Z": Impossible—no C=C → no
restricted rotation.
-
"Only one conformer matters":
Conformational isomerism affects molecular strain and thermodynamic
stability.
Exam
Tips for questions involving the isomers molecular formula C6H14
(see also above)
-
When asked to name or draw isomers: check IUPAC priority and
avoid duplicates.
-
Use tabulated boiling points to support discussion of
intermolecular forces.
-
Watch for questions on fuel performance and octane
rating—branching is key.
-
Avoid “geometrical isomerism” traps—remind students that
it needs C=C, not just a similar formula.
(d)
Learning objectives - questions to be answered?
How do you work out the
IUPAC names of the isomers of molecular formula C6H14?
How do you draw the structural formula
and skeletal formula of the isomers of molecular formula C6H14?
How many aliphatic structural isomers
are there of molecular formula C6H14?
How many aliphatic carbon chain isomers
are there of molecular formula C6H14?
How many positional isomers are there
of molecular formula C6H14?
How many R/S (optical) isomers
(enantiomers) of molecular formula C6H14?
Are there any aliphatic open chain
alkene isomers of molecular formula C6H14?
Are there any alicyclic cycloalkane
isomers of molecular formula C6H14?
Are there any functional group isomers
with a molecular formula C6H14?
Are there any R/S (optical) isomers
(enantiomers) with a molecular formula C6H14?
Does C6H14 have any stereoisomers?
This page
will answer these questions for molecular formula C6H14
|
(e) Practise exam questions based on the
isomers of molecular formula C6H14
Jot
down your responses and check out the answers
ANSWERS
to the questions based on the isomers of
C6H14
If you think there are
any errors, please email me asap at
chem55555@hotmail.com
I don't mind if students/teachers do a selected printout
of these questions and answers.
Given the five skeletal formulae of the isomers of molecular
formula C6H16, for each question
answer provide brief reasoning.
Q1 Name all five isomers
of molecular formula C6H14
Q2 Which isomer of C6H14
is most likely to have the highest boiling point?
Q3 Which isomer of C6H14 is most
likely to have the lowest boiling point?
Q4 Which molecule will display:
(a) The least number of principal 1H
chemical shifts?
(b) The least number of principal 13C
chemical shifts?
(c) The most number of principal 1H
chemical shifts?
(d) The most number of principal 13C
chemical shifts?
Q5 On mono-chlorination (via Cl2/uv):
(a) Which isomer will give a maximum of only two
different mono-chloroalkanes?
(b) Which isomer can yield a maximum of five different
mono-chloroalkanes?
ANSWERS
to the questions based on the isomers of
C6H14
|
Associated organic chemistry links
Advanced Level pre-university
organic chemistry notes
IR, mass and H-1 & C-13 NMR
spectra of organic compounds
Comparison of the ir, mass, 1H and 13C NMR spectra of the isomers of C6H14 (via
a 1H NMR
spectrum page)
Index of sets of isomers for a given
molecular formula
The molecular structure and
naming of ALKANES
Index of revision notes
on the chemistry of ALKANES and the petrochemical
industry
For isomerism in organic chemistry, see also the
notes
Isomerism: introduction, structural isomerism - chain,
positional, functional group, tautomerism
Stereoisomerism:
introduction, definition,
priority rules, E/Z isomerism (cis/trans isomerism)
Stereoisomerism - R/S isomerism (optical
isomerism) -
definition - examples explained
This is a big chemistry website, please allow time
to explore it
Index of my advanced
(pre-college/university) organic
chemistry revision notes
The
main index for all my spectroscopy pages
The
main index for 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
|
Website
content © Dr Phil Brown 2000+. All copyrights reserved on Doc
Brown's Chemistry revision notes, images, quizzes, worksheets etc.
Copying of website material is NOT permitted. Advanced
level pre-university/college organic chemistry
revision notes
isomerism of molecular formula C6H14.
All
suitable for
chemistry students taking the WJEC advanced A level chemistry, CCEA
advanced A level chemistry, Cambridge CIE advanced A level chemistry, AQA
advanced A level chemistry, Edexcel advanced A level chemistry, OCR
advanced A level chemistry, Salters advanced A level chemistry, IB
advanced level chemistry, US grade 11-12 K12 AP Honors chemistry courses |
Keywords or phrases: how many isomers are
there of molecular formula C6H14? how do you name the isomers of
molecular formula C6H14? what is the molecular structure of the
isomers of C6H14, what type of isomerism is exhibited by molecules
of formula C6H14, how do you work out the isomers of molecular
formula C6H14, what are the structural isomers of C6H14, the carbon chain
isomers of C6H14 in the homologous series of alkanes, comparing
the spectra of isomers of molecular formula C6H14 how many
structural isomers of C6H14 can you draw? how many structural
isomers does C6H14 have? what are the possible isomers of C6H14?
revision notes on isomerism of C6H14 molecules
E/Z isomers cis trans stereoisomers of C6H14,
isomers of C6H14 of molecular mass 86
open carbon chain aliphatic alkane molecules isomeric of molecular formula
C6H14,
ester molecules isomeric with molecular formula C6H14, structural isomers of molecular
formula C6H14, optical isomers R/S enantiomers isomeric with molecular
formula C6H14, positional isomers isomeric with molecular formula
C6H14,
which types of isomerism are exhibited by molecules isomeric with
molecular formula C6H14 alkyl positional isomers of C6H14 branched
carbon chain alkane isomers of C6H14
cyclic alkanes of formula
C6H14 E/Z isomers of molecular formula C6H14 (geometric cis/trans
isomers) alkene molecules isomeric of molecular formula C6H14,
molecules isomeric with molecular formula C6H14, structural isomers of molecular
formula C6H14, optical isomers R/S enantiomers isomeric with molecular
formula C6H14, positional isomers isomeric with molecular formula
C6H14,
alicyclic alkanes of formula C6H14 which types of isomerism are exhibited by molecules isomeric with
molecular formula C6H14 alkyl positional isomers of C6H14 branched
carbon chain alkene isomers of C6H14 cycloalkanes of molecular formula
C6H14 which are isomeric with alkenes of molecular formula C6H14
stereoisomers of molecular formula C6H14 cycloalkane functional
group isomers of C6H14 are there alkyne isomers of C6H14? are
there cycloalkanes of formula C6H14? are there cycloalkenes of
formula C6H14 chain isomers of C6H14 functional group isomers of
C6H14 substituent and functional group positional isomers of
C6H14 open carbon chain aliphatic alkane molecules isomeric of molecular formula
C6H14,
hydrocarbon molecules isomeric with molecular formula C6H14, structural isomers of molecular
formula C6H14, optical isomers R/S enantiomers isomeric with molecular
formula C6H14, positional isomers isomeric with molecular formula
C6H14,
which types of isomerism are exhibited by molecules isomeric with
molecular formula C6H14 alkyl positional isomers of C6H14 branched
carbon chain alkane isomers of C6H14
cycloalkane molecules isomeric of molecular formula C6H14,
cycloalkane molecules isomeric with molecular formula C6H14, structural isomers of molecular
formula C6H14, optical isomers R/S enantiomers isomeric with molecular
formula C6H14, positional isomers isomeric with molecular formula
C6H14,
which types of isomerism are exhibited by molecules isomeric with
molecular formula C6H14 alkyl positional isomers of C6H14 branched
carbon chain cycloalkane isomers of molecular formula C6H14
|
ANSWERS
I don't mind if students/teachers do a selected printout of
these questions and answers.
Practise exam questions based on the isomers of molecular
formula C6H14
If you think there are
any errors, please email me asap at
chem55555@hotmail.com
Given the five skeletal formulae of the isomers of molecular
formula C6H16 and for each question
answer provide brief reasoning.
For
each question answer provide brief reasoning.
Q1 Name all five isomers
of molecular formula C6H14
ANSWERS: hexane,
2-methylpentane, 3-methylpentane,
2,2-dimethylbutane and 2,3-dimethylbutane
Q2 Which isomer of C6H14
is most likely to have the highest boiling point?
ANSWER A:
The least branched and most polarizable molecule,
intermolecular bonding maximised.
Q3 Which isomer of C6H14 is most
likely to have the lowest boiling point?
ANSWER D or E: Most branched, more compact
molecules, less polarizable, reduces intermolecular bonding,
D is probably the most compact.
Q4 Which molecule will display:
(a) The least number of principal 1H
chemical shifts?
ANSWER E: 2, most symmetrical isomer, only two
chemical environments
(b) The least number of principal 13C
chemical shifts?
ANSWER E: 2, most symmetrical isomer,
only two chemical environments
(c) The most number of principal 1H
chemical shifts?
ANSWER B: 5, least symmetrical isomer, 5 different
chemical environments
(d) The most number of principal 13C
chemical shifts?
ANSWER E: 5, least symmetrical isomer,
5 different chemical environments
Q5 On mono-chlorination (e.g. via Cl2/uv):
(a) Which isomer will give a maximum of only two
different mono-chloroalkanes?
ANSWER E: Only two different alkyl group
situations (CH and -CH3), substitution at C1 or
C2 are the only different substituent positions for the
chlorine atoms, again, relate this to the high symmetry of
isomer E.
(b) Which isomer can yield a maximum of five different
mono-chloroalkanes?
ANSWER B: Five different alkyl group situations,
so substitution at C1 to C5 gives different products, five
different positions of the chlorine atom, again, relate this
to the low symmetry of isomer B. |
|
