Cyclopentane eclipsed

[Alan Chien 1J]

When we are talking about the planar form of cyclopentane, does it have "5 pairs of eclipsed C-H bonds"? Also, when we say pairs does that refer to all the C-H bonds that are eclipsed between two carbon atoms?

Lastly, in a puckered cyclopentane (envelope conformation), I understand that the structure is dynamic and any of the carbons can flip up moving that carbon out of the plane into a staggered conformation. This would relieve any torsional strain between that carbon and the adjacent carbons. However, is there any torsional strain between any of the other four carbons?

[Chem_Mod]

Cyclopentane has 5 pairs of eclipsed C-H bonds.

Yes, some torsional strain remains. If you study the structure you can see some C-H bonds are still eclipsed.