AS Level Chemistry Isomerism (FULL)

All Isomers; including diagrams, desciptions, effects, causes, reasons. 

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  • Created by: sanjay cj
  • Created on: 13-05-11 13:21
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Isomerism
Isomers are molecules that have the same molecular formula, but have a
different arrangement of the atoms in space. That excludes any
different arrangements which are simply due to the molecule rotating as
a whole, or rotating about particular bonds.
Sanjay 12I

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Structural isomers
In structural isomerism, the atoms are arranged in a completely different order.
Chain isomerism
Different arrangement of the carbon skeleton
Similar chemical properties
Slightly different physical properties
More branching = lower boiling point
These isomers arise because of the possibility of
branching in carbon chains. In the picture above (left), 3
chain isomers of pentane are shown. In the top one,
the carbons lie in a horizontal line (linear), without
branching. However, the others have branching.…read more

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Molecules have same molecular formula
Molecules have different functional groups
Molecules have different chemical
properties
Molecules have different physical properties
These isomers have the same molecular formula
but different functional groups. This usually means they have very different sets of chemical
reactions based on the functional group and there can be significant differences in
melting/boiling points and solubility.
For example, a molecular formula C3H6O could be either propanal (an aldehyde) or propanone
(a ketone).
Another common example is illustrated by the
molecular formula C3H6O2.…read more

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Stereo isomers are molecules that have the same molecular formula, but the atoms are
joined to each other in a different spacial arrangement ­ they occupy a different position in
3-dimensional space.
Geometrical
isomerism
An example of stereoisomerism
Found in some, but not all, alkenes
Occurs due to restricted rotation of
C=C bonds
Found in two forms CIS and TRANS
CIS: Groups/atoms are on the same side of the double bond.
TRANS: Groups/atoms are on opposite
sides across the double bond.…read more

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Another form of stereoisomerism
Occurs when compounds have non-superimposable mirror images
The two isomers are known as optical isomers or enantiomers
They occur when molecules have a chiral centre
A chiral centre contains an asymmetric carbon atom
An asymmetric carbon atom has four different atoms (or groups) arranged
tetrahedrally around it.
If a carbon has more than one of
any atom/group attached, it
cannot be chiral
Two forms exist which are
non-superimposable mirror images of each
other.…read more

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