# What are the two isomers of the organic compound C2H4Br2?

You necessarily have a $C - C$ bond. How many ways can you arrange the 6 substituents, $4 \times H$, and $2 \times B r$, around the carbon centres.
You know that each $C$ will have the one $C - C$ bond (i.e. to each other); there are 2 ways in which the other 6 substituents can be arranged over those 2 carbon atoms. Care to hazard a guess?