Chapter 4: 4.4 Stereoisomers II - Geometric or Cis/Trans Isomers

Question 1

When do geometric (cis/trans) isomers occur?

Answer 1

When there is a rigid bond (containing a minimum of one pi bond) between two atoms

Question 2

Define:

1. Cis isomers
2. Trans isomers

Answer 2

1. When substituents on the same side
2. When substituents are on opposite sides

Question 3

True or False:

The trans isomer is considered more stable

Answer 3

True, due to less steric repulsion

Question 4

What nomenclature is used with tri or tetrasubstituted alkenes?

Answer 4

E/Z nomenclature

Question 5

State:

Steps to assign E/Z nomenclature

Answer 5

1. Cut the alkene in half vertically
2. Assign high/low priorities on the two substituents using the Cahn-Ingold-Prelog rules
3. If the high priority groups are on the same side, the alkene is (Z)
4. If the high priority groups are on opposite sides, the alkene is (E)