Which isomer has the lower energy and which is fiexible in cis and trans decalin ?

Explanation

To determine which isomer of decalin has lower energy and which is flexible, we need to analyze the structures of cis-decalin and trans-decalin.

### Step 1: Understand the Structures of Decalin Isomers
Decalin consists of two fused cyclohexane rings. There are two main isomers of decalin: cis-decalin and trans-decalin.

- **Cis-decalin**: In this isomer, the two hydrogen atoms on the bridgehead carbons are on the same side of the ring. This results in a more strained structure due to the axial and equatorial positions of the substituents.

- **Trans-decalin**: In this isomer, the two hydrogen atoms on the bridgehead carbons are on opposite sides. This configuration allows for a more stable arrangement where the substituents can occupy equatorial positions.
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