Chemical Forums

Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Elnaz on January 24, 2013, 03:36:08 PM

Title: Cyclic diyne
Post by: Elnaz on January 24, 2013, 03:36:08 PM
Hi there,

I need to know what is the smallest cyclic diyne?

thanks
Title: Re: Cyclic diyne
Post by: curiouscat on January 25, 2013, 12:59:13 AM
This?

C1#CCCC#CCC1

Or

C1#CC#CCCCC1
Title: Re: Cyclic diyne
Post by: Elnaz on January 26, 2013, 01:43:03 PM
thanks curiosecat, could you write the source please?
Title: Re: Cyclic diyne
Post by: Arkcon on January 26, 2013, 03:56:16 PM
I don't believe there's likely to be a source dedicated to just this question.  I would have suggested you try ever smaller diyne and see if they exist.  Its not likely a cyclic diyne exits if the complementary cyclic diene doesn't exist, and there's ring strain even on smaller cyclic alkanes.  Unless you're looking for theoretical predictions based on bond lengths and hybridizations, but that's a pretty advanced topic.  I'm also guessing, since you need a source or citation, you'd not be satisfied with buying a molecular modeling kit and seeing how small of one you can make without the model popping apart.
Title: Re: Cyclic diyne
Post by: curiouscat on January 26, 2013, 04:07:13 PM
I don't believe there's likely to be a source dedicated to just this question.  I would have suggested you try ever smaller diyne and see if they exist.  Its not likely a cyclic diyne exits if the complementary cyclic diene doesn't exist, and there's ring strain even on smaller cyclic alkanes.  Unless you're looking for theoretical predictions based on bond lengths and hybridizations, but that's a pretty advanced topic.  I'm also guessing, since you need a source or citation, you'd not be satisfied with buying a molecular modeling kit and seeing how small of one you can make without the model popping apart.

One relatively cheap option might be to use something like Gaussian to calculate relative stabilities. Though not sure how you'd use that to say if or not they exist.
Title: Re: Cyclic diyne
Post by: AWK on January 26, 2013, 05:39:47 PM
http://onlinelibrary.wiley.com/doi/10.1002/hlca.19750580121/abstract

1,3-cyclooctadiyne cannot exist.