How many isomers?

Question

How many isomers (including all stereoisomers) exist for dibromopentadiene?

No, you do not have to draw out every single one. It is using the 2^n formul, where n=chiral centers along with subtraction for meso structures. I know you also have to factor in cis and trans possibilities with the structures as well.

I thought I'd put this in the right category, since I screwed up before.

Answer 1

Quite a lot.

First, draw out all the possible isomers for pentane.

Then put in one double bond and draw the isomers for pentene. Remember to show cis and trans (or E and Z) as distinct. Then put in the second double bond (care! at this stage, you will be making lots of duplicates), and then the two bromine atoms, one at a time.

The 2^n formula does not tell you the number of structural or geometric isomers, which is what you say you are looking for. It only tells you the effect of the chiral centres.