The compound 1,2-dichloroethane (C2H4CI2) is nonpolar, while cis-dichloroethylene (C2H2Cl2...

The compound 1,2-dichloroethane (C2H4CI2) is nonpolar, while cis-dichloroethylene (C2H2Cl2) has a dipole moment. The reason for the difference is that groups connected by a single bond can rotate with respect to each other, but no rotation occurs when a double bond connects the groups. On the basis of bonding considerations, explain why rotation occurs in 1,2-dichloroethane but not in cis-dichloroethylene.