Question

Question: Label each C-C double bond as E or Z. Kavain is a naturally occurring relaxant isolated from kava root.

Short answer

Answer

1. E isomer
2. Z isomer
3. Both are E isomers.

Step-by-step solution

E and Z naming

When there are more than two alkyl groups on either side of the double bond, they are named E or Z.

Rules for assigning E and Z designations

Assign priorities to the groups based on the following criteria:

• Divide the groups on either side of the double bonds with a vertical line and assign them priorities.
• The atom with a higher atomic number is assigned priority one.
• If two of the atoms directly bonded to the double-bonded carbon are the same, then priority is assigned based on the set of atoms attached to them.

Priority 1 is the highest, followed by priority 2.

If the higher priority groups appear on the same side of the double bond, the compound is named Z.

If the higher priority groups appear on the opposite sides of the double bond, the compound is named E.

 Step 3: Labelling the given compounds as E or Z

a. The two higher priority groups are on the same side. Hence, this is an E isomer.

Priorities labeled in a

b. The two higher priority groups are on opposite sides. Hence, this is a Z isomer.

Priorities labeled in b

c. In both double bonds, two higher priority groups are on the same side. Hence, both are E isomers.

Priorities labeled in c