Question

$C_2$ is rotated anti-clockwise ${180}^o$ about $C_2-C_3$ bond. The resulting conformer is
$C_2$ is at the front and $C_3$ at the rear.

• A. Partially eclipsed
• B. Eclipsed
• C. Gauche
• D. Staggered

Answer 1

The correct option is B Eclipsed


Here, after the anti-clockwise rotation of ${180}^{\circ }$ about $C_2-C_3$ axis, the $-C{H}_3$ (bulky) groups on adjacent carbon are at diherdral angle of $0^{\circ }$. Thus, the anti-staggered conformer is converted to fully eclipsed conformer.