[rleung]

Hi,

I just want to make sure here that there are no stereoisomers for 1-isopropyl-1-cyclopentene, right?  My book's solutions manual makes it sound like there is since it draws mirror images of both, but there is no chiral center in that molecule, and since the ring has only 6 carbons, it can only exist as cis, right?  Thanks so much.

[mike]

Are you sure you have the right structure? cyclopentene has 5 carbons not 6.

[rleung]

Yes, 5 carbons only.  

But even if it were 6 carbons, it still couldn't have stereoisomers, right?  I mean, unless you count the isopropyl group being in an axial vs. equatorial position, but those are just configurations vs. actual stereoisomers, right?  Thanks.

Ryan

[mike]

Yes I would tend to agree with you, I don't see any stereoisomers.

[Albert]

In my opinion, there can be E-Z isomers (also known as trans-cis).

[rleung]

Hmm, how can there be E-Z isomers since the ring is less than 8 carbons in length?

Ryan

[Albert]

Well, of course the Z isomer is not stable, but, if asked, I'd answer 1-isopropyl-1-cyclopentene is an E isomer. I mean, we can think of E and Z isomers for 1-isopropyl-1-cyclopentene, even if we cannot yield the Z one.