Question

The most stable conformational isomer of given compound will be

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

In given compound, the ethyl and methyl groups are in trans position in C1 and C2 position. So the possible cis isomer chair form will be two.
1. Both $C_2{H}_5$ and $C{H}_3$ are at axial position
2. Both $C_2{H}_5$ and $C{H}_3$ are at equatorial position

Larger size group sholud be at equatorial position to reduce the 1, 3 diaxial interaction.
Thus, both $C_2{H}_5$ and $C{H}_3$ in the equatorial position is the stable conformational isomer of the given compound.
Thus, option (c) is correct.