[cthompso]

I'm studying for my orgo exam and I feel pretty confident about chiral centers, but still have a few points of confusion, so if anyone could help clear them up it'd be greatly appreciated. Thanks!

Is the molecule 4-bromo-4-chlorocyclopentene chiral? It doesn't seem to have a plane of symmetry, but potential chiral carbon is attached to: Br, Cl, and 2 equivalent CH2CH atoms. So is it achiral?

[Honclbrif]

When assessing chirality of a site in a ring, my preferred method is to go around the ring clockwise (what functionality do you encounter in what order?), then go around the ring counterclockwise. If the clockwise circuit is the same as the counterclockwise circuit, you can count them as being the same and the site is achiral.

So for 4-bromo-4-chlorocyclopentene, starting from the halogenated carbon we get
Clockwise:  CH2-CH=CH-CH2
Counterclockwise: CH2-CH=CH-CH2

What would happen if it was 4-bromo-4-chloro-1-methylcyclopentene?

[cthompso]

Sooo if it contained the methyl group than it would be chiral, but without it it's achiral, right?

[Honclbrif]

Since without the methyl, both trips around the ring are the same, you can basically consider each trip to be and "identical substituent". With the methyl group there the two trips are different and can be considered "different substituents". After that the chloride and the bromide each count as different substituents.