Newman projection | Cycloalkanes
Draw a Newman projection of all the different staggered and eclipsed conformations of the 1,2-dibromoethane.
Rank them acoording to their stability.
Which conformation has the largest dipole moment? The smallest one?
Eclipsed (Syn) conformation has the largest dipole moment (the two C-Br polar bond go in the same direction).
Staggered (Anti) conformation has the smallest dipole moment (the two C-Br polar bond go in the opposite direction: the dipole moment is equal to zero).