Chapter 7
Q. 7.1
assigning E and Z Configurations to Substituted alkenes
Assign E or Z configuration to the double bond in the following compound:
S t r a t e g y
Look at the two substituents connected to each double-bond carbon, and determine their ranking using the Cahn–Ingold–Prelog rules. Then see whether the two higher-ranked groups are on the same or opposite sides of the double bond.
Step-by-Step
Verified Solution
The left-hand carbon has –H and –CH_3 substituents, of which –CH_3 ranks higher by sequence rule 1. The right-hand carbon has –CH(CH_3)_2 and –CH_2OH substituents, which are equivalent by rule 1. By rule 2, however, –CH_2OH ranks higher than –CH(CH_3)_2 because the substituent –CH_2OH has an oxygen
as its highest second atom, but –CH(CH_3)_2 has a carbon as its highest second atom. The two higher-ranked groups are on the same side of the double bond, so we assign Z configuration.
