Understanding Stereoisomerism in C5H10 with One Cyclopropane Ring

[tandoorichicken]

How many stereocenter containing isomers of c5h10 are there where the molecule must contain one ring?

I identified the cis and trans forms of 1,2-dimethylcyclopropane, but I think my TA said there was one more form containing a cyclopropane ring... but I can't remember for sure. Is C1 on 1,1-dimethylcyclopropane a stereocenter? It doesn't seem to have four different substituents.

So confusing.

 

[dav2008]

You're right that the C1 on 1,1-dimethylcyclopropane doesn't have four different substituents.

I can't seem to think of any other C₅H₁₀ cyclic molecules that would have a stereocenter.

The isomers of C₅H₁₀ with rings I can think of would be cyclopentane, methylcyclobutane, 1,1-dimethylcyclopropane, 1,2-dimethylcyclopropane, and ethylcyclopropane. The only ones with stereocenters are the isomers of 1,2-dimethylcyclopropane as you mentioned.

 

[tandoorichicken]

Hey, I got it.

There are cis and trans versions of 1,2-dimethylcyclopropane. But, within the trans isomer, there are also (S) and (R) enantiomers that are nonsuperimposable (by definition).

Hopefully I will remember all of this on the midterm