Question

Why propane has only one eclipsed confirmation while butane has three? Explain?

Answer 1

Conformationally, butane is more complex than ethane or propane. For ethane or propane, the three eclipsedforms are identical in energy, as are the three staggered forms. ... In the most stable conformation, the two methyl groups lie as far apart from each other as possible with a dihedral angle of 180 degrees.