Three distinct constitutional or geometric isomers share the formula C2H2Cl2: 1,1-dichloroethene, cis-1,2-dichloroethene, and trans-1,2-dichloroethene. The C=C bond is rigid and planar in each isomer.
(a) Draw a valid Lewis diagram for each isomer and identify the approximate geometry around each carbon atom.
(b) For each isomer, state whether the molecule possesses an overall dipole moment. If a net dipole is present, indicate its general direction within the molecular plane.
(c) Arrange the three isomers in order of increasing magnitude of net dipole moment. Justify the ordering by referring explicitly to the relative orientation of the C–Cl bond dipoles in each structure.