Stereoisomers

Question 1

What are stereoisomers?

Answer 1

• Stereo isomers are compounds with the same structural formula but with a different arrangement in space.
• Some alkenes have stereoisomers because there is a lack of rotation around C=C.
• There are E-isomers and Z-isomers.

Question 2

E/Z isomerism

Answer 2

• This is when the double bonded carbon atoms each have 2 different atoms/groups attached to them and when there is restricted rotation.
• Each of the groups linked to C=C is given priority.
• E-isomers when the priority groups are opposite(E).
• Z-isomers when priority groups are on the (Z)ame.

Question 3

Cis-trans isomerism

Answer 3

• Special case of E/Z isomerism where the 2 carbons in the double bond have at least 1 group in common and the other attached is H.
• Cis-isomer has the 2 identical groups on same side.
• Trans-isomer has the 2 identical groups on opposite sides.

Question 4

Cahn-Ingold-Prelog priority rules

Answer 4

• Highest priority group of each of the C=C carbons is the one which has the atom w/ the highest atomic number DIRECTLY bonded to the carbon atoms.
• If the atoms directly bonded are the same (e.g methyl and ethyl), look at the next atom along in each group.