C4.1 Stereoisomerism Flashcards
Define Isomer
Isomers are compounds which have the same formula but different structures.
Isomers containing the same functional groups have different physical properties because…
the intermolecular forces rely on the sizes and shapes of molecules.
Structural isomerism
where the bonding pattern within the molecule is different
Stereoisomerism
bonding pattern is the same but the functional groups are arranged differently in space.
how does a molecule display Geometrical isomerism?
no rotation about C=C because of the π bond
How does a molecule show geometrical isomerism?
- draw R1R2-C=C-R3R4
- C=C must be present
- R1 ≠ R2
- R3 ≠ R4
How to determine geometrical isomerism.
- Circle the heaviest group on each C.
- if they’re together = Z
- if they’re apart = E
Optical isomerism
Optical isomerism exists where it’s impossible to superimpose a molecule on its mirror image
How to identify a chiral centre
C with 4 single bonds with 4 different functional groups. Denoted with a *
How to distinguish between 2 enantiomers?
Shine plane polarised light straight and perpendicular. One enantiomer will rotate the light clockwise and the other isomer rotates the light anticlockwise.
What denotes the 2 possible enantiomers in optical isomerism?
d and l
How would you construct the enantiomers in optical isomerism?
tetrahedral 109.5* bond angle
One _________ bond
One ————- bond
One ▶ bond
What standard is used to decide d and l isomers?
Glyceraldehyde
d enantiomers rotate light…
clockwise
l enantiomers rotate light…
anticlockwise
