|
Doc Brown's
Advanced Chemistry: Part 14.7
Isomers of a given molecular formula
The
constitutional-structural
isomers of molecular formulae C6H13F, C6H13Cl,
C6H13Br
and
C6H13I,
including carbon chain, positional & stereoisomerism
(1)
An Introduction to the
17 constitutional
isomers of molecular formula C6H13X
(2)
Details of the
isomers of C6H13X
(where X
=
F, Cl, Br and I)
(3)
Key revision points and extra notes on the
isomers of
C6H13X
(4)
Learning objectives - questions to be answered?
(5)
Exam practise questions based on the isomers of C6H13X
[Author
©
Dr
Phil Brown GRIC, PhD: Doc
Brown's advanced level organic chemistry exam revision notes suitable
for students of UK advanced A level chemistry courses, IB advanced
chemistry & US K12 grades 11-12 and AP honors chemistry courses: Molecular
spectroscopy and analysing the isomers of C6H13X
[page updated
RE-EDIT]
Associated organic chemistry page links
Index of sets of isomers for a given
molecular formula
This is a big chemistry website, please allow time
to explore it
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(1) Introduction to the
17 constitutional
isomers of molecular formula
C6H13X where X = a halogen atom
i.e. the formulae: C6H13F, C6H13Cl, C6H13Br
and
C6H13I
Relative molecular mass and
percent composition
based on atomic masses:
C 12.01,
H 1.01, F 19.00, Cl 35.45, Br 79.90,
I 126.90
|
Formula of compound |
Relative molecular
mass |
%
carbon |
%
hydrogen |
%
halogen |
|
C6H13F |
104.19 |
69.16 |
12.60 |
18.24 |
|
C6H13Cl |
120.64 |
59.73 |
10.88 |
29.39 |
|
C6H13Br |
165.09 |
43.65 |
7.95 |
48.40 |
|
C6H13I |
212.09 |
33.98 |
6.19 |
59.83 |
Empirical formula
= molecular formula
=
C6H13X
(where X = a single halogen atom)
If applicable
(see isomerism
summary at the end of the page)
How to work out the isomers of C6H13X (X =
F, Cl, Br and I)
(a) You work them out by starting a hexane carbon chain (3
isomers), then a 2-methylpentane chain (5 isomers), then a 3-methylpentane
chain (4 isomers) and finally a 2,2-dimethylbutane and a 2,3-dimethylbutane chain (3 and 2
isomers respectively).
(b) each time working out where a halogen substituent can
go.
(c) This gives 17 constitutional-structural formulae based
on substituting one halogen atom for a H in hydrocarbons of formula C6H14.
(d) Finally, check through the 17 structural formula for any
molecule with an asymmetric carbon atom (chiral carbon atom) which gives
rise to R/S optical isomerism - a pair of enantiomers.
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.
All the isomers are aliphatic saturated open chain
mono-substituted haloalkanes.
All the structural isomers are based on various carbon
chains and the different possible positions of the halogen atom.
There
is no functional group isomerism, but the haloalkane isomers (alkyl halide
isomers) may be classified as primary, secondary or tertiary.
Stereoisomerism is
where molecules have the same basic constitutional structural formula, but
isomers differ in the 2D/3D arrangement of the atoms. Applicable here.
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.
E/Z geometrical isomerism is not possible here because they
are open chain saturated compounds - no C=C double bond or substituted
aliphatic ring compounds, structures that can restrict free rotation.
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.
There are several examples of these haloalkanes exhibiting
R/S optical isomerism
NOTE
The images of
C6H13X (X =
F, Cl, Br and I)
presented are theoretical, in the sense that some may be
so unstable as not to exist, but you will find all are
stable and all found
on the internet.
The are
17
constitutional-structural isomers of molecular formula
C6H13X (X =
F, Cl, Br and I),
irrespective of any E/Z or R/S optical isomerism that may be possible,
though
E/Z isomerism isn't possible with these molecules.
However, 9 of the structural formulae exhibit R/S optical
isomerism,
and one of them, molecule (10) has two chiral centres!
This means there are
20 R/S optical stereoisomers for
C6H13X.
Therefore there is a
total of 17 + 11 = 28
distinct unique isomers for
C6H13X
(of all types)
Some internet sources say 26, but that does not include two
extra stereoisomers from molecule (10) which has two non-equivalent chiral
centres, highlighted in
blue
CH3CHXCH(CH3)CH2CH3
As explained above, they are all open chain aliphatic
compounds derived from halogen mono-substitution products of saturated alkane hydrocarbons
(hexane, methylpentanes and dimethylbutanes)
with the formula C6H14 and remember for all the images,
X
= a halogen atom from group 7/17 of the periodic table.
(2) Details of the
isomers of
C6H13X
(X
=
F, Cl, Br and I)
The abbreviated
structural formulae have been matched to the skeleton formulae.
(1)
CH3CH2CH2CH2CH2CH2X
structural formula,
, skeletal formula
1-fluorohexane, 1-chlorohexane, 1-bromohexane, 1-iodohexane
Primary haloalkane (primary halogenoalkane,
primary alkyl halide) e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 6 1H
and 6 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 2 : 2 : 2 : 2
: 2 (for equivalent protons)
Several of these chemical shifts will be close
together.
One of the least symmetrical isomer, giving the
maximum number of six NMR chemical shifts.
Index of
1H NMR spectra organic
compounds and
Index of
13C NMR spectra organic
compounds
(2)
CH3CH2CH2CH2CHXCH3,
abbreviated structural formula,
, skeletal formula
2-fluorohexane, 2-chlorohexane, 2-bromohexane, 2-iodohexane
Exhibits R/S optical isomerism, carbon atom
C2 is chiral.
Secondary haloalkane (secondary halogenoalkane,
secondary alkyl halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 6 1H
and 6 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 2 : 2 : 2 : 1
: 3 (for equivalent protons, right to left)
One of the least symmetrical isomer, giving the maximum number
of six NMR chemical shifts.
(3)
CH3CH2CH2CHXCH2CH3,
abbreviated structural formula,
 ,
skeletal formula
3-fluorohexane, 3-chlorohexane, 3-bromohexane, 3-iodohexane
Exhibits R/S optical isomerism, carbon atom
C3 is chiral.
Secondary haloalkane (secondary halogenoalkane, secondary
alkyl halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 6 1H
and 6 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 2 : 2 : 1 : 2
: 3 (for equivalent protons, right to left)
One of the least symmetrical isomer, giving the
maximum number of six NMR chemical shifts.
(4)
CH3CH2CH2CH(CH3)CH2X,
abbreviated structural formula,
 ,
skeletal formula
1-fluoro-2-methylpentane, 1-chloro-2-methylpentane, 1-bromo-2-methylpentane, 1-iodo-2-methylpentane
Exhibits R/S optical isomerism, carbon atom
C2 is chiral.
Primary haloalkane (primary halogenoalkane, primary alkyl
halide)
Number of low resolution
NMR chemical shift
δ
signal peaks: 6 1H
and 6 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 2 : 2 : 1 : 3
: 2 (for equivalent protons)
One of the least symmetrical isomer, giving the
maximum number of six NMR chemical shifts.
(5)
CH3CH2CH2CX(CH3)2,
abbreviated structural formula,
 ,
skeletal formula
2-fluoro-2-methylpentane, 2-chloro-2-methylpentane, 2-bromo-2-methylpentane, 2-iodo-2-methylpentane
Tertiary haloalkane (tertiary halogenoalkane, tertiary
alkyl halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 4 1H
and 5 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 2 : 2 : 6
(3+3) (for equivalent protons)
(6)
CH3CH2CHXCH(CH3)2,
abbreviated structural formula,
 ,
skeletal formula
3-fluoro-2-methylpentane, 3-chloro-2-methylpentane, 3-bromo-2-methylpentane, 3-iodo-2-methylpentane
Exhibits R/S optical isomerism, carbon atom
C3 is chiral.
Secondary haloalkane (secondary halogenoalkane, secondary
alkyl halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 5 1H
and 5 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 2 : 1 : 1 : 6
(3+3) (for equivalent protons, right to left)
(7)
CH3CHXCH2CH(CH3)2,
abbreviated structural formula,
 ,
skeletal formula
2-fluoro-4-methylpentane, 2-chloro-4-methylpentane,
2-bromo-4-methylpentane, 2-iodo-4-methylpentane
Exhibits R/S optical isomerism, carbon atom
C2 is chiral.
Secondary haloalkane (secondary halogenoalkane, secondary
alkyl halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 5 1H
and 5 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 1 : 2 : 1 : 6
(3+3) (for equivalent protons, right to left)
(8)
XCH2CH2CH2CH(CH3)2,
abbreviated structural formula,
 ,
skeletal formula
1-fluoro-4-methylpentane, 1-chloro-4-methylpentane,
1-bromo-4-methylpentane, 1-iodo-4-methylpentane
Primary haloalkane (primary halogenoalkane, primary alkyl
halide)
Number of low resolution
NMR chemical shift
δ
signal peaks: 5 1H
and 5 13C
(email
if disagree?)
1H NMR ratio of peaks: 2 : 2 : 2 : 1 : 6
(3+3) (for equivalent protons, right to left)
 ,
 ,
(9)
XCH2CH2CH(CH3)CH2CH3,
abbreviated structural formula,
 ,
skeletal formula
1-fluoro-3-methylpentane, 1-chloro-3-methylpentane, 1-bromo-3-methylpentane, 1-iodo-3-methylpentane
Exhibits R/S optical isomerism, carbon atom
C3 is chiral.
Primary haloalkane (primary halogenoalkane, primary alkyl
halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 6 1H
and 6 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 2 : 2 : 1 :
3
: 2 (for equivalent protons)
One of the least symmetrical isomer, giving the
maximum number of six NMR chemical shifts.
(10)
CH3CHXCH(CH3)CH2CH3,
abbreviated structural formula,
 ,
skeletal formula
2-fluoro-3-methylpentane, 2-chloro-3-methylpentane, 2-bromo-3-methylpentane, 2-iodo-3-methylpentane
Exhibits R/S optical isomerism, carbon atoms
C2 and
C3 are chiral,
so the stereoisomer situation is a bit more complicated with two chiral centres.
A molecule with two non-equivalent R/S chiral centres is denoted by four
possible combinations of configurations.
Therefore can form two pairs of R/S optical isomers (enantiomers), carbon atoms 2 and 3 are both asymmetric
(chiral), but not identical stereocentres.
There will four possibilities of
optically active stereoisomers: RR', RS', SR' and SS', but this is
university level analysis.
Secondary haloalkane (secondary halogenoalkane, secondary
alkyl halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 6 1H
and 6 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 1 : 1 : 3 : 2
: 3 (for equivalent protons, right to left)
One of the least symmetrical isomer, giving the
maximum number of six NMR chemical shifts.
(11)
CH3CH2CX(CH3)CH2CH3,
abbreviated structural formula,
 ,
skeletal formula
3-fluoro-3-methylpentane, 3-chloro-3-methylpentane, 3-bromo-3-methylpentane, 3-iodo-3-methylpentane
Tertiary haloalkane (tertiary halogenoalkane, tertiary
alkyl halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 3 1H
and 4 13C
(email
if disagree?)
1H NMR ratio of peak areas: 6
(3+3) : 4 (2+2) : 3 (for equivalent protons)
One of the most symmetrical isomers, giving a lower
number of NMR chemical shifts.
(12)
CH3CH2CH(CH2X)CH2CH3,
abbreviated structural formula,
 ,
skeletal formula
3-(fluoromethyl)pentane, 3-(chloromethyl)pentane, 3-(bromomethyl)pentane, 3-(iodomethyl)pentane
(NOT 1-chloro-2-ethylbutane etc., NOT using longest carbon
chain of 5 atoms)
Primary haloalkane (primary halogenoalkane, primary alkyl
halide)
Number of low resolution
NMR chemical shift
δ
signal peaks: 4 1H
and 4 13C
(email
if disagree?)
1H NMR ratio of peak areas: 6
(3+3) : 4 (2+2) : 1 : 2 (for equivalent protons)
(13)
CH3CH2C(CH3)2CH2X,
abbreviated structural formula,
 ,
skeletal formula
1-fluoro-2,2-dimethylbutane, 1-chloro-2,2-dimethylbutane, 1-bromo-2,2-dimethylbutane, 1-iodo-2,2-dimethylbutane
Primary haloalkane (primary halogenoalkane, primary alkyl
halide)
Number of low resolution
NMR chemical shift
δ
signal peaks: 4 1H
and 5 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 2 : 6
(3+3) : 2 (for equivalent protons)
(14)
CH3CHXC(CH3)3,
abbreviated structural formula,
 ,
skeletal formula
Two sets of names are common on the
internet
2-fluoro-3,3-dimethylbutane,
2-chloro-3,3-dimethylbutane, 2-bromo-3,3-dimethylbutane,
2-iodo-3,3-dimethylbutane (I think these are
the more correct IUPAC names)
3-fluoro-2,2-dimethylbutane, 3-chloro-2,2-dimethylbutane,
3-bromo-2,2-dimethylbutane, 3-iodo-2,2-dimethylbutane
These molecules will exhibit R/S 'optical' isomerism, as
carbon atom
C2 is chiral, a stereocentre, resulting in a pair of
non-superimposable mirror image forms - enantiomers.
Two sets of names seem to be accepted for these molecules
(on the internet).
Secondary haloalkane (secondary halogenoalkane, secondary
alkyl halide)
Number of low resolution
NMR chemical shift
δ
signal peaks: 3 1H
and 4 13C
(email
if disagree?)
1H NMR ratio of peak areas: 3 : 1 : 9
(3x3) (for equivalent protons)
One of the more symmetrical isomers, giving a lower number
of NMR chemical shifts.
(15)
XCH2CH2C(CH3)3,
abbreviated structural formula,
 ,
skeletal formula
1-fluoro-3,3-dimethylbutane, 1-chloro-3,3-dimethylbutane, 1-bromo-3,3-dimethylbutane, 1-iodo-3,3-dimethylbutane
Primary haloalkane (primary halogenoalkane, primary alkyl
halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 3 1H
and 4 13C
(email
if disagree?)
1H NMR ratio of peak areas: 2 : 2 : 9
(3x3) (for equivalent protons, from right to left)
One of the more symmetrical isomers, giving a lower
number of NMR chemical shifts.
(16)
XCH2CH(CH3)CH(CH3)2,
abbreviated structural formula,
 ,
skeletal formula
1-fluoro-2,3-dimethylbutane, 1-chloro-2,3-dimethylbutane, 1-bromo-2,3-dimethylbutane, 1-iodo-2,3-dimethylbutane
Exhibits R/S optical isomerism, carbon atom
C2 is chiral.
Primary haloalkane (primary halogenoalkane, primary alkyl
halide)
e.g.
 ,
 ,
Number of low resolution
NMR chemical shift
δ
signal peaks: 5 1H
and 5 13C
(email
if disagree?)
1H NMR ratio of peak areas: 2 : 1 : 3 : 1 : 6
(3+3) (for equivalent protons)
(17)
(CH3)2CXCH(CH3)2,
abbreviated structural formula,
 ,
skeletal formula
2-fluoro-2,3-dimethylbutane, 2-chloro-2,3-dimethylbutane, 2-bromo-2,3-dimethylbutane, 2-iodo-2,3-dimethylbutane
Tertiary haloalkane (tertiary halogenoalkane, tertiary
alkyl halide)
Number of low resolution
NMR chemical shift
δ
signal peaks: 3 1H
and 4 13C
(email
if disagree?)
1H NMR ratio of peak areas: 6
(3+3) : 1 : 6 (3+3) (for equivalent protons)
One of the more symmetrical isomers, giving a lower
number of NMR chemical shifts.
(3) Key revision points and extra notes on the
isomers of
C6H13F,
C6H13Cl, C6H13Br and C6H13I
Summary of the origin of the isomerism C6H13X
molecules
-
Chain Isomerism: The
carbon chain itself can be arranged in different ways (e.g., a straight
chain, a chain with a single methyl branch, or a chain with two methyl
branches). The skeleton can be a derivative of:
-
Hexane (1-halohexane,
2-chalohexane,
3-halohexane)
-
2-Methylpentane (5
isomers)
-
3-Methylpentane (4
isomers)
-
2,2-Dimethylbutane (3
isomers)
-
2,3-Dimethylbutane (2
isomers)
-
Positional Isomerism: For
a given carbon skeleton, the chlorine atom can be attached to
different carbon atoms (e.g., 1-halohexane,
2-halohexane,
and 3-halohexane).10
Among
the 17 structural constituent isomers, 9 possess one or more
chiral centres (asymmetric carbon atoms—a carbon atom bonded to four
different groups), giving rise to optical isomerism (a type of
stereoisomerism).
-
These
chiral molecules exist as non-superimposable mirror images called
enantiomers
-
Eight of the structural isomers
have one chiral centre, each contributing two optical isomers (2
enantiomers $\times$ 8 isomers = 16 optical isomers).
-
One structural
isomer (2-halo-3-methylpentane) has two chiral centres,
potentially contributing four optical isomers. However, due to the
specific structure, it contributes four stereoisomers.
The
total number of distinct molecules (all isomers) is 28.
Comprising 17
constitutional structural isomers + 11 additional stereoisomers that
arise from 9 of the constitutional structural isomers that exhibit R/S
optical stereoisomerism).
The structural isomers
without a chiral centre are counted as one isomer, and the 9 structural
isomers that are chiral are counted as their multiple stereoisomer forms
(enantiomers).
Overview of
aspects of the chemistry of haloalkanes of formula
Halogenoalkane isomers of C6H13X
(X = F, Cl, Br, I) differ in boiling points, reactivity, and uses due to
variations in halogen size, bond strength, and carbon chain structure.
Branched isomers are
generally more volatile; iodine-containing compounds are most reactive.
Structural Overview of
C6H13F,
C6H13Cl, C6H13Br and C6H13I
Isomers
Each halogenoalkane series (C6H13X)
has:
-
Straight-chain isomers: e.g.
1-chlorohexane, 2-chlorohexane
-
Branched isomers: e.g. 2-methylpentyl
halides, 3-methylpentyl halides
-
Positional isomers: halogen attached to
different carbon atoms
Physical Property Differences
of C6H13X
|
Property |
Fluoro (F) |
Chloro (Cl) |
Bromo (Br) |
Iodo (I) |
|
Boiling Point |
Lowest |
↑ |
↑↑ |
Highest |
|
Density |
Low |
Moderate |
High |
Very High |
|
Volatility |
High |
↓ |
↓↓ |
Lowest |
|
Solubility in Water |
Poor (all) |
Poor |
Poor |
Poor |
|
Dipole Moment |
Highest |
↓ |
↓↓ |
Lowest |
Key Insight: Boiling point increases with
halogen size due to stronger London dispersion forces. Branched isomers have
lower boiling points than straight-chain ones.
Chemical Reactivity and Mechanisms
|
Halogen |
Bond Strength
(C–X) |
Reactivity |
Typical Reaction |
|
F |
Very strong |
Very low |
Rarely reacts |
|
Cl |
Moderate |
Moderate |
SN1/SN2 |
|
Br |
Weaker |
High |
SN1/SN2 |
|
I |
Weakest |
Very high |
SN1 preferred |
Exam Tip: C–I bond breaks most easily,
making iodoalkanes fastest in nucleophilic substitution.
Uses and Applications
|
Compound Type |
Common Uses |
|
Fluoroalkanes |
Refrigerants (e.g. CFC
replacements), Teflon precursors |
|
Chloroalkanes |
Solvents (e.g. dry
cleaning), intermediates in PVC production |
|
Bromoalkanes |
Organic synthesis,
flame retardants |
|
Iodoalkanes |
Diagnostic agents
(e.g. contrast media), lab synthesis |
Note: Environmental concerns limit chloro-
and bromoalkane use due to ozone depletion.
Common Student Misconceptions
-
Misidentifying SN1 versus SN2: Confusing
conditions and substrate types
-
Assuming all halogenoalkanes are equally reactive:
Reactivity varies with halogen and structure
-
Overestimating water solubility:
Halogenoalkanes are largely nonpolar
-
Ignoring steric hindrance: Branched isomers
hinder SN2 reactions
Exam Revision Tips
-
Compare C–X bond strengths: Use bond
enthalpy data to explain reactivity
-
Practice mechanism diagrams: Label
nucleophile, leaving group, and transition states
-
Use boiling point trends: Link to molecular
mass and branching
-
Apply to real-world contexts: E.g.
refrigerants, solvents, pharmaceuticals
-
Revise isomer types: Structural,
positional, chain isomerism
(4)
Learning objectives - questions to be answered?
How do you draw the structural formula
and skeletal formula of the isomers of molecular formula C6H13F C6H13Cl
C6H13Br C6H13I? There are a total of 28 distinct isomers based on 17 constitutional
isomers and 20 R/S optical isomers
How many aliphatic structural isomers
are there of halogen compounds with molecular formula C6H13F C6H13Cl
C6H13Br C6H13I? 17 constitutional isomers
Can you give the IUPAC names of the isomers of
C6H13F C6H13Cl C6H13Br C6H13I?
How many aliphatic carbon chain isomers
are there of halogen compounds with molecular formula C6H13F C6H13Cl
C6H13Br C6H13I? 17 constitutional isomers
How many positional isomers are there
of organic halogen molecules with molecular formula C6H13F C6H13Cl
C6H13Br C6H13I? 17 constitutional isomers
How many E/Z (geometrical) isomers are
there of molecular formula C6H13F C6H13Cl C6H13Br C6H13I? none
How many R/S (optical)
isomers (enantiomers) of molecular formula C6H13F C6H13Cl C6H13Br
C6H13I? there are 20 R/S isomers
Are there any halocycloalkene isomers of
formula C6H13F C6H13Cl C6H13Br C6H13I? none
Are there any cyclic haloalkene isomers
of formula C6H13F C6H13Cl C6H13Br C6H13I? none
Are there any cyclo haloalkane isomers
of formula C6H13F C6H13Cl C6H13Br C6H13I? none
Are there any halodiene isomers of
molecular formula C6H13F C6H13Cl C6H13Br C6H13I? none
Are there any haloalkyne isomers of
molecular formula C6H13F C6H13Cl C6H13Br C6H13I? none
Are there any functional group isomers
with a molecular formula C6H13F C6H13Cl C6H13Br C6H13I? none
Do C6H13F C6H13Cl
C6H13Br C6H13I organic halogen molecules have any stereoisomers? Yes
there are 20 R/S optical
isomers, total of 28 isomers all together
This page
will answer these questions for molecular formula
C6H13F,
C6H13Cl, C6H13Br and
C6H13I
(5) Exam
practise questions based on the isomers of
C6H13F,
C6H13Cl, C6H13Br and
C6H13I
|
QUESTIONS
(5) Exam practise questions based on the isomers of
C6H13F,
C6H13Cl, C6H13Br and
C6H13I
Practise exam questions
based on isomers of molecular formula C6H13X
Jot
down your responses and check out the answers
ANSWERS
to the questions based on the isomers of
C6H13X
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 six
selected isomers of molecular formula
C6H13X
where X = halogen atom
...
... answer
the question plus as much reasoning as possible!
Q1
Classify A to F in terms of primary, secondary or
tertiary haloalkanes.
Q2
Which of A to F can exhibit R/S ('optical')
isomerism and identify the chiral centres.
Q3 (a)
Which can be hydrolysed to yield a primary alcohol?
(b)
Draw the skeletal formula structure of the alcohols
and name them.
Q4 Which of these isomers would be the most reactive
towards NaOH(aq)?
Q5 Which isomers, if any, can exhibit E/Z
('geometrical') isomerism?
Q6 For isomer F, if X
= Br,
write the reaction
equation on refluxing it with aqueous sodium
hydroxide and name the product (in words and
skeletal formula. What type of reaction mechanism is
taking place?
Q7 If X = I for the
six sets of isomers
(a) theoretically,
which sets of the isomers would give a single alkene
product when refluxed with ethanolic potassium
hydroxide? What type of reaction is taking place?
(b) Write equations for the reactions (skeletal
formula style), and what is the relationship between
the products?
If you think there are
any errors, please email me asap at
chem55555@hotmail.com
|
Associated organic chemistry links
Index of sets of isomers for a given
molecular formula
The molecular structure and naming of
HALOALKANES (how
to name and draw alkane structures)
The molecular structure and
naming of ALKANES (how
to name and draw alkane structures)
The molecular structure and naming
of ALKENES
(how to name and draw alkene structures)
Index of revision notes on the chemistry
HALOALKANES
including reactions
Index of revision notes
on the chemistry of ALKANES and the petrochemical
industry
Index of revision notes on the chemistry ALKENES
including reactions and polymers
Advanced Level pre-university
organic chemistry notes
IR, mass and H-1 and C-13 NMR
spectra of organic compounds
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 optical 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
Index
of all my spectroscopy pages
Index
of 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
A summary chart of isomerism
|
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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 the isomers of C6H13F,
C6H13Cl,
C6H13Br and
C6H13I with names, structures, types
of isomerism and a few spectroscopy details 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, CCEA advanced level chemistry, US grade 11-12 AP honors
chemistry courses and they will also prove useful to
1st year undergraduate students of chemistry. |
Keywords or phrases: how many isomers are
there of halogen compounds of molecular formula C6H13F C6H13Cl
C6H13Br C6H13I? what is the
structure of the halogen compound isomers of molecular formula how do you name the isomers of
molecular formula C6H13F C6H13Cl C6H13Br C6H13I? what is the molecular structure of the
isomers of C6H13F C6H13Cl C6H13Br C6H13I, what type of isomerism is exhibited by molecules
of formula C6H13F C6H13Cl C6H13Br C6H13I, how do you work out the isomers of haloalkanes
formula C6H13F C6H13Cl C6H13Br C6H13I, what are the structural isomers of
C6H13F C6H13Cl C6H13Br C6H13I, the carbon chain
isomers of C6H13F C6H13Cl C6H13Br C6H13I in the homologous series of alkanes, comparing
the many structural isomers does C6H13F C6H13Cl C6H13Br C6H13I have?
what are the possible isomers of C6H13F C6H13Cl C6H13Br C6H13I? revision notes on
isomerism of C6H13F C6H13Cl C6H13Br C6H13I molecules, the molecular structure of
the isomers of C6H13F C6H13Cl C6H13Br C6H13I how to draw the
structural formula of isomers of C6H13F C6H13Cl C6H13Br C6H13I, how to draw the displayed
formula of isomers of C6H13F C6H13Cl C6H13Br C6H13I, how to draw the skeletal formula of
halogenoalkane compound isomers of formula C6H13F C6H13Cl
C6H13Br C6H13I, how to name the isomers of molecular formula
C6H13F C6H13Cl C6H13Br C6H13I,
R/S optical isomers enantiomers of C6H13F C6H13Cl C6H13Br C6H13I isomeric with molecular formula
C6H13F C6H13Cl C6H13Br C6H13I, structural isomers of molecular
formula C6H13F C6H13Cl C6H13Br C6H13I, optical isomers R/S enantiomers isomeric with molecular
formula C6H13F C6H13Cl C6H13Br C6H13I, positional isomers isomeric with halocycloalkenes,
haloalkanes, haloalkynes, haloalkenes of molecular formula
C6H13F C6H13Cl C6H13Br C6H13I,
which types of isomerism are exhibited by molecules of formula
C6H13F C6H13Cl C6H13Br C6H13I alkyl positional isomers of C6H13F
C6H13Cl C6H13Br C6H13I branched carbon chain
isomers of C6H13F C6H13Cl C6H13Br C6H13I,
stereoisomers of molecular formula C6H13F C6H13Cl C6H13Br C6H13I,
optical isomers R/S enantiomers isomeric with molecular formula
C6H13F C6H13Cl C6H13Br C6H13I, positional isomers isomeric with
molecular formula C6H13F C6H13Cl C6H13Br C6H13I, which types of
isomerism are exhibited by C6H13F C6H13Cl C6H13Br C6H13I halogen
atom positional isomers of C6H13F C6H13Cl C6H13Br C6H13I, how to
work out the halogen compound names of isomers of C6H13F C6H13Cl
C6H13Br C6H13I There are 17 constitutional isomers and 20 R/S optical isomers., a total of 28
isomers all
together.
How to deduce the isomers of
organic halogen molecules with the formula C6H13Cl C6H13Br C6H13I C6H13F, How to write, draw and name the
substituted halogen compounds
isomers of molecular formula C6H13Cl C6H13Br C6H13I C6H13F,
How to deduce if the isomers of
C6H13Cl C6H13Br C6H13I C6H13F organic halogen compounds can exhibit R/S optical isomerism, How to deduce if the isomers of
C6H13Cl C6H13Br C6H13I C6H13F can exhibit E/Z geometrical isomerism (do C6H13Cl C6H13Br C6H13I C6H13F have cis/trans geometric
isomers?), number of structural isomers of C6H13Cl C6H13Br C6H13I C6H13F, number of
stereoisomers of C6H13Cl C6H13Br C6H13I C6H13F
|
ANSWERS
(5) Exam
practise questions based on the isomers of
C6H13F,
C6H13Cl, C6H13Br
and
C6H13I
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 six
selected isomers of molecular formula
C6H13X
where X = halogen atom
...
... answer
the question plus as much reasoning as possible!
Q1
Classify A to F in terms of primary, secondary or
tertiary haloalkanes.
ANSWERS:
A (sec), B (tert), C (prim), D (tert), E (prim) and
F (sec)
Haloalkane classification: primary RCH2X,
secondary R2CHX and tertiary R3CX
where R = alkyl
Q2
Which of A to F can exhibit R/S ('optical')
isomerism and identify the chiral centres.
ANSWERS: A (C2) and F (C2 and C3), a
chiral carbon atom has four different atoms/groups
attached to the same carbon atom, note F has two
asymmetric carbon atom chiral centres.
Q3 (a)
Which can be hydrolysed to yield a primary alcohol?
ANSWERS: C and E, primary haloalkanes
yield primary alcohols by hydrolysis of the terminal
halogen group on C1
(b)
Draw the skeletal formula structure of the alcohols
and name them.
ANSWERS: C will give 4-methylpentan-1-ol
and E will yield 2-ethylbutan-1-ol.
and
Q4 Which of these isomers would be the most reactive
towards NaOH(aq)?
ANSWERS:
B and D, general reactivity trend for haloalkanes
towards nucleophiles is tert > sec > prim
Q5 Which isomers, if any, can exhibit E/Z
('geometrical') isomerism?
ANSWER:
None, free rotation of groups allowed around all C-C
bonds in these isomeric molecules, there is no
restricted rotation like you get around the C=C
bonds.
Q6 For isomer F, if X
= Br,
write the reaction
equation on refluxing it with aqueous sodium
hydroxide and name the product (in words and
skeletal formula. What type of reaction mechanism is
taking place?
ANSWERS:
2-bromo-3-methylpentane + hydroxide ion
===> 3-methylpentan-2-ol + bromide ion
A nucleophilic
substitution reaction.
Q7 If X = I for the
six sets of isomers
(a) theoretically,
which sets of the isomers would give a single alkene
product when refluxed with ethanolic potassium
hydroxide? What type of reaction is taking place?
ANSWERS:
C and E, the terminal halogen atom means only one
alkene can be formed by an elimination reaction. All
the others will give two isomeric alkenes depending
on where the H and I (as HI) are eliminated from
adjacent carbon atoms in the carbon chain.
(b) Write equations for the reactions (skeletal
formula style), and what is the relationship between
the products?
ANSWERS
For C:
1-iodo-4-methylpentane
+ hydroxide ion ===> 4-methylpent-1-ene
+ iodide ion + water
and
For E:
1-iodo-2-ethylbutane
+ hydroxide ion ===> 2-ethylbut-1-ene +
iodide ion + water
The product is also
more correctly IUPAC named 3-methylidenepentane or
3-methylenepentane, just make sure you get the
structure.
Obviously the two
alkene products are isomers of C6H12.
If you think there are
any errors, please email me asap at
chem55555@hotmail.com
|
|
