13.2 - Stereoisomerism

Question 1

Define stereoisomer

Answer 1

Same structural formula, different spatial arrangement

Question 2

What are the 2 types of stereoisomer?

Answer 2

E/Z isomer - occurs in compounds with C=C

Optical isomer - occurs in a wide range of compounds including alkanes with no functional groups

Question 3

What are the conditions for E/Z isomerism?

Answer 3

• C=C

- Different groups per carbon atom of the double bond

Question 4

What is the reason for the rigidity of a C=C bond?

Answer 4

The electron density above and below the sigma bond (the pi bond)

Question 5

What is cis-trans isomerism?

Answer 5

Special type of E/Z isomerism

• Molecules must have C=C
• Must have one of the 2 different groups on each carbon to be HYDROGEN

cis isomer is - z
trans isomer is - e

Question 6

What defines a z isomer?

Answer 6

Where the higher priority groups are on the same side of the double bond, and the low priority on the same side.

Question 7

What defines an e isomer?

Answer 7

When the high priority and low priority groups exist on the same side of the double bond.

Question 8

How do you assign priority?

Answer 8

1. On each carbon, the immediate atom with the higher atomic number is the high priority, and the other is the low priority.
2. If the priorities are the same along the groups, look for the first point of difference.