CHEMISTRY COMMUNITY

In question 4.29, why does 1 have the largest dipole moment although the distance between the two chlorines is the smallest?

1 has the largest dipole moment because since the chlorines are positioned close to one side of the molecule, that side of the molecule will have a polarized charge in comparison to the other side with no chlorines. 3 has the smallest dipole moment because since the molecule is symmetrical, any charge the molecule might have would cancel each other out.

It is precisely because the two chlorines are positioned close together that they have the largest dipole moment, because then there is a stronger force of repulsion due to their close proximity. Figure 3 would have essentially no dipole moment, as the symmetry has the dipole moments "cancel each other out" so that the figure would be linear, is how I would interpret it.

I would always like to look at dipole moments as vectors. Looking at option 1, adding the two vectors (dipole moments) together gives us a resultant vector with a larger magnitude than the resultant vector for option 2.