# Dipole moments of dibromoethene isomers

There was an exercise in my textbook asking to compare the dipole moments of 1,1-dibromoethene and 1,2-dibromoethene(Z). The answer in the textbook says that the dipole moment of 1,1-dibromoethene is greater than that of 1,2-dibromoethene.

This seems counter-intuitive as the angle between the dipole moments of the two $$\ce{C-Br}$$ bonds in 1,1-dibromoethene is $$120°$$ and that in 1,2-dibromoethene(Z) is $$60°$$. A little physics tells us that the net dipole moment of 1,2-dibromoethene should be greater than that of 1,1-dibromoethene which contradicts the answer in the textbook. I want to know whether I am correct or not.

• There is also the dipole moment of C-C bond. – Ivan Neretin Sep 14 at 17:16