Can carbon form a circular double-bond structure on its own?

[dakoad]

Hello!

I was wondering if there exists a form of arrangement of carbon atoms, where it is in a circle with double bonds at both sides of every C atom. Basically, something like a benzene ring, but each C atom, instead of forming 3 bonds with other carbons and 1 with hydrogen, forms a C=C bond on each side of it.

 

Thank you,

Daniel.

[hypervalent_iodine]

I assume you mean something like this?

 

 

H-C=C=C-H is a known compound, but you couldn't form a six-membered ring of only C=C=C... You have to consider the presence of pi bonds and what that does to the geometry of the carbons. For example, allene:

 

 

(Image from http://chemwiki.ucdavis.edu/Core/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Solution_Manual/Chapter_01_Solutions )

 

As you can see, the central carbon has two pi bonds, one extending to one carbon along the z axis and the other to the second bonded carbon along the y axis. The overall affect of this is that the geometry becomes locked in place and the C-C-C angle has to be 180o. You could never form a ring from cumulated polyenes like this simply because you'd be placing too much angular strain on the bonds and the geometry doesn't allow it.

[dakoad]

Thank you very much!

[John Cuthber]

If the ring was big enough the bending strain might not be an insurmountable hurdle.

But there would be no credible way to synthesise it.

[hypervalent_iodine]

If the ring was big enough the bending strain might not be an insurmountable hurdle.

But there would be no credible way to synthesise it.

 

 

I was thinking this as I wrote my post. I would imagine it would have to be quite big, though I'm not familiar with exactly how distorted such an arrangement could get before it cracked.

[Elite Engineer]

I assume you mean something like this?

 

image.png

 

H-C=C=C-H is a known compound, but you couldn't form a six-membered ring of only C=C=C... You have to consider the presence of pi bonds and what that does to the geometry of the carbons. For example, allene:

 

image.png

 

(Image from http://chemwiki.ucdavis.edu/Core/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Solution_Manual/Chapter_01_Solutions )

 

As you can see, the central carbon has two pi bonds, one extending to one carbon along the z axis and the other to the second bonded carbon along the y axis. The overall affect of this is that the geometry becomes locked in place and the C-C-C angle has to be 180o. You could never form a ring from cumulated polyenes like this simply because you'd be placing too much angular strain on the bonds and the geometry doesn't allow it.

I just scrolled down and saw "I suppose you mean something like this" and saw the cyclohexane and just cracked up

[hypervalent_iodine]

I just scrolled down and saw "I suppose you mean something like this" and saw the cyclohexane and just cracked up

I think you mean cyclohexahexene