IS it correct to think that the eclipsed conformation is less stable meaning it has more energy because the dihedral angle is zero thus the bonds are not as far as they can possibly be?  or are those 2 things unrelated? (Eclipsed conformations always correspond to local maxima of potential energy (where the first derivative of potential energy by the dihedral angle is zero, and the second derivative is negative), which is why they are unstable. They usually have higher energy than staggered conformations (local minima where the first derivative of potential energy by the dihedral angle is zero, and the second derivative is positive), which is\also contributing to their instability. - GS).