[tree234]

I am studying mcmurry organic chemisty of 6th edition
When I start to study additional problems. I have some problem of one question
The qustion want to expailn about why don't cyclohexene have a cis-trans isomer, but cyclodecene does?
I try to find the answer about this question on the internet.
I just get cyclodecene is so big enough to exist trans-cyclodecene, but cyclohexene dosen't. I can't understand just small explin about this question.
Someone help me to understand about this. Plz, recount about this question.

[lemonoman]

Check out the pictures rleung drew and posted on this similar thread:

http://www.chemicalforums.com/index.php?board=3;action=display;threadid=3855

Hopefully that shows you the cis/trans-iness of cyclodecene.

Notice the way the molecule is bent.  Can cyclohexene do anything like THAT to get a trans isomer?

[laotree]

Trans hexene? How great should the strain be?

[alphahydroxy]

Yep - the strain would be too great.

It is simply because the size of the ring cannot accomodate a trans double bond within it.

You could make a model (or draw it out, remembering to keep your bond angles reasonable). build the trans alkene unit, and try and build the ring around it - you'll have some trouble....

Now, if you try this with decene, you'll find it much easier.