# Energy of eclipsed and staggered conformations of ethane and propane

Which points on the given energy diagram represents eclipsed confirmation of ethane and staggered confirmation of propane respectively?

Attempt: Eclipsed configuration is unstable because of repulsions between filled $\sigma$ or bonding orbital and the anti or staggered configuration is more stable due to interactions between filled $\sigma$ orbital and empty $\sigma^*$ orbital.

From the given diagram, either R or S could represent eclipsed confirmation of ethane and P or Q could represent staggered confirmation of propane.

Since they are different compounds, they should lie on different energy diagrams. So the answer could be (R,Q) or (S,P). Which one is correct?