AQA a level chemistry notes for mechanism A2

3.3. 1 Optical Isomerism



of chirality in
Define optical isomerism which result molecules
A
farmay stereoisomerism occurs as a




Chirality
For a molecule to be considered chiral, it
must:

1. Have no plane of symmetry
2. Have I
diggerent groups attached to its chiralcentre




"I as
4 moleculeisn't chiral
This

it has a plane
of symmetry
. This chiral
moleculeis




H




Enantioners Optical isomers which are new superimposableimages
of each other




-"grus
⑯



How can we
distinguish enantioners from eachother?

-
shine prone polarised lightthrough the sample

observe the direction of the rotation oflight
-




Whatis
a racemic mixture Amitture with equal amounty both
enantiomers




I forms of steroisomerism 1)Geometric Isemerism

2) Optical (semer

, 3.3.7 Optical Isomerism


Define optical isomerism agormoy stereoisomerism arising asa

result of chirality inmolecules


Enantiomers blow can we differentiate between enantiomers?
'
H i H You observe their effect enplane polarised light
' '
'
'
c
toy :[ on plane polarised light through
-
You shine
"

no a
-




Chs ! CH }
the sample
-

if the light is rotated clockwise itis
,



non -




superimposed images tired enantiomer

light is rotated anticlockwise itis
of eachother if the
-

,



thet enantiomer



dgeuehaueceinixtureoyegual amounts of enantiomers.it is
calledraracemicmixturecracemate .




Why are racemic mixtures Because thlggectgthe.mn
optically inactive ? oytightcancelsoutr