Question - Explain What Is Meant By "c2 Symmetry" And "mirror Plane Symmetry". Can A Molecule With "mirror Plane Symmetry" Ever Be Chiral? 
          
        
        Answer - 
        
"C2 symmetry" means that 180o rotation about an axis through the molecule results in a geometry equivalent to the starting geometry. "Mirror plane symmetry" means that one half of the molecule can be perfectly reflected into the other half through a symmetry plane. Molecules with mirror plane symmetry cannot be chiral.