4-20

Question

Which isomer is more stable, cis-decalin or trans-decalin? Explain.

Step-by-Step Solution

Verified
Answer

Trans-decalin is more stable as it shows fewer steric interactions.

1Cis and trans conformation of decalin

In cis-decalin, the hydrogen atoms at the bridgehead carbons are on the same face of the rings; in trans-decalin, the bridgehead hydrogens are on opposite faces.

2Axial and equatorial positions

Axial bonds are the bonds that are perpendicular or vertical to the ring plane. Equatorial bonds are approximately horizontal in the plane of the ring.

3Conformation stability


                                     Cis- and trans-decalin, respectively

Trans-decalin is more stable than cis-decalin because the rings are at a maximum distance in trans-decalin, and in cis-decalin show steric interactions and hence, decreases its stability.