Question 8.10: Predict whether the molecule dichloromethane, CH2Cl2, has a ......
Predict whether the molecule dichloromethane, CH_{2}Cl_{2}, has a net dipole moment.
The Lewis formula for a CH_{2}Cl_{2} molecule is
\begin{matrix} :\overset{..}{\underset{|}{Cl}}:\ \ \\H-C-\overset{..}{\underset{..}{Cl}}: \\ \overset{|}{H} \ \ \ \end{matrix}
There are four bonding pairs and no lone pairs of electrons around the carbon atom; thus, we conclude from VSEPR theory that the molecular geometry is tetrahedral. The C–Cl bond dipole moments point from the Cl atom to the C atom because the electronegativity of the Cl atom is greater than that of a C atom. The C–H bond dipole moments point from the C atom to the H atom, because the electronegativity of a C atom is greater than that for a H atom. Thus, the resultant of the two C–Cl bond dipole moments and the resultant of the two C–H bond dipole moments point in the same direction, as indicated by the blue arrow representing the overall dipole moment.
Thus, we predict (correctly) that a dichloromethane molecule is polar.
