Question

Which of the two conformation among the following represents staggered form of ethane?

• A. 1 and 4
• B. 2 and 3
• C. 1 and 2
• D. 1 and 3

Answer 1

The correct option is C 1 and 2

In staggered conformation, atoms/substituents attached to adjacent carbons are as far as possible.

In ethane, H atoms on adjacent carbons are present at dihedral angle of ${60}^o$ ( ${180}^o$ or ${300}^o$ ) to have staggered conformation.
In (1) and (2), the dihedral angle is ${60}^o$.
In (3), it is in skew conformation (dihedral angle is < ${60}^o$).
In (4), the ethane is in eclipse conformation where the dihedral angle is $0^o$.