Pearson BTEC Level 3 National Extended Diploma in Applied Science Understand types, structures, reactions, uses and properties of
isomers. This assignment is written to DIstinction standard. Acheived a Distinction for the whole of unit 13
Pearson BTEC Level 3 National Extended Certificate In Applied Science
Unit 14
Learning aim C - Understand types, structurers,
Reactions, uses and properties of isomers
Structural isomerism is molecules who share the same molecular formula but are
arranged in different orders they are 3 types chain isomerism, position isomerism, and
functional group isomerism
chain isomerism
in which the atoms are arranged differently example butane C4H10
In butane it shows how its a straight
carbon chain however in the second it
shows how the last CH3 group in the
carbon is moved to the 2 carbon in the
carbon chain inw which one hydrogen
from the second CH3 group is moved to
the third CH3 group to from
methylpropane/isobutane
It shows how the isobutane has a lower
boiling and melting point than butane
where isobutane has a boiling point -12C
and a melting point of -160C compared to butane in which has a boiling point of 0C and a
melting point of -138C in which this is due to the fact that straight carbon chains have a
higher melting and boiling point than branched chain isomers due to straight carbon
chains having stronger van der waals forces between the molecules than branched
carbon chains
,Pentane
In pentane C5H12 it shows how the first
isomer of pentane has a straight carbon
chain
However in the second isomer it shows
how the last CH3 group in pentane is
moved to bond with the 2 carbon in
which 1 hydrogen from the second CH3
group is moved to the third CH3 group
to form isopentane
It shows how isopentane has a lower
boiling and melting point than pentane
where isopentane has a boiling point
27.8C and a melting point -161C
compared to pentane which has a
boiling point of 36.1C and a melting
point of -129.8C in which this is due to the fact that pentane has stronger van der waals
forces between the molecules due to pentane having a straight carbon therefore more
molecules are in more contact with each other compared to isopentane which has a
branched carbon chain therefore less contact between molecules
Position isomerism
In position isomerism only functional groups are positioned around the carbon links
Example of 1-bromopropane 2-bromopropane = positional isomerism
In 1-bromopropane the bromine atom is at the end of the carbon chain however
In 2-bromopropane it shows how a Br atom
is moved to the second carbon in the carbon
chain In which one hydrogen from the
second CH2 group is moved to the last CH2
group
,It demonstrates how 1-bromopropane has a higher boiling and melting point than 2-
bromopropane where 1-bromopropane has a boiling point of 71C and a melting point of -
110C compared to 2-bromopropane in which has a boiling point 59 C and a melting point
of -128C in which this is due to the fact than 2-bromopropane has a branched shape
therefore reducing the contact between molecules decreasing the van der waals
compared to 1-bromopropane in which has a straight shape therefore increasing the
contact between molecules therefore having stronger van der waals forces
Example butan1-ol butan2-ol = positional isomerism
In butan-ol it shows how the OH group is as
the end of the carbon chain however in the
butan-2-ol it demonstrates how the how the OH
group is shifted to the second carbon on the
carbon forming the positional isomer butan-2-
ol
It suggest how butan-1 ol has a high melting
and boiling point than butan-2-ol where butan-1-ol melting point is -89.8C and boiling
point of 117.7C compared to butan-2-ol which has a melting point of -115C and a boiling
point of 100C as it implies how butanol has a straight carbon chain therefore has
stronger van der waals between molecules as well as more contact between the
molecules compared to butan-2-ol in whhc chas a branched carbon chain therefore
decreasing the amount of van der waal forces between molecules due to molecules
having less contact with each other
Functional group isomerism
In functional group isomerism isomers can contain the same molecular formula but can
contain different functional groups
Example C3H6O can be propanone or propanal
It shows how propanone has a higher boiling
and melting point than propanal where
propane has a boiling point of 56C due to
,propanone having an additional hydrogen bond therefore increasing the strength of the
forces between the molecules in propanone in which more energy is required to break
the molecules increasing the boiling point
Example C3H602 can be propanoic acid or methyl ethanoate
Propanoic acid has a higher
melting point methyl ethanoate
as it shows how propanoic acid
has more hydrogen bonds than
methyl ethanoate therefore
propinco acid have more
stronger van der waal forces
therefore requiring more energy
to break the bonds therefore
having a higher mp than methyl
ethanoate
Stereoisomerism
Stereoisomerism is molecules who have the same structural and molecular formula
however their atoms are still in different arrangements
Geometric isomerism
They occur due to restriction of rotation of carbon-carbon bonds.
Geometric isomers ar broken down into cis and trans form where in cis it shows how the
2 moelucles are on both sides of the carbon double bond whoever in trans it
deomstartes hwo the moelcules are on oppposite sides of the carbon double bond
Example 1,2 - dichloroethane
It shows how the two models of 1,2 - dichloroethane aren't the same as it demonstrates
how you cant get from one to the other due to being unable to twist the carbon bond due
to having a double bond these are therefore geometric isomers
,It implies how they are geometric isomers with complicated structure are broken down
into E and Z isomers, where it demonstrates in Z isomers the molecules with the higher
polarity are on the same side of the carbon double bond whereas the E isomers the
molecules with the higher polarity are on opposite sides of the carbon double bond . the
polarity is due to to molecules with a higher atomic number have a higher polarity than
molecules with a lower atomic number
Example
Geometric isomerism of
unsaturated fatty acids
example Oleic acid
, Example elaidic acid
It shows how in elaidic acid it shows how it is a trans (E) isomer as it shows how the the
2 groups with he higher polarity are on opposite sides of the carbon double bond as on
the left hand bond of elaidic acid the
carbon attached to to the double
bond c has a higher atomic number
than H therefore has a higher
polarity as well as on the right hand
side
Melting point of elaidic and oleic
acid
It shows how oleic acid has a higher
boiling point than elaidic acid where
oleic acid has a boiling point of 360C
and elaidic acid at 288C this is due
to the fact tha cis oleic acid is a polar moelcule compared to elaidic acid which is a non
polar moelcule therefore demonstrating how oleic acid conatins polar hydrogen bonds
on the same side of the double carbon carbon bond therefore inceasing diploe dipole
forces and ineteraations betwenen the hydrogen atoms in which needs extra energy to
break the forces increasing the boiling point comapred to elaidic acid in which the the
top hygoen on the right and the bottom hyrogen on the left share the same charge
therefore decreasing the polarity in which the moelucles only experience van deer wall
forces theerefore less enenrgy is required to break these forces reducing the boiling
point
Boiling point of elaidic acid and oleic acid
It shows how elaidic acid has a higher melting point than oleic acid where elaidic acid
has a melting point of 52C and oleic acid of 13C this is due to the fact elaidic is a trans
isomer and oleic is cis isomer in whihc trans isomers have a better packaging then cis
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