[wereworm73]

I had this nutty idea for an experiment a few years back:

If just CaC₂ and water can be used to make acetylene, then the carbide is a fully deprotonated ethylyne.  If you mix this with 1,5-dichloropentane, then the C₂^2- anion should do a nucleophilic attack on the dichloropentane to form a heptynide anion.  Because cycloheptyne is so unstable due to ring strain, I would think the anion would seek another dichloropentane molecule to form a neutral 12-carbon species (1,12-dichloro-6-dodecyne).

2 Cl-CH₂-CH₂-CH₂-CH₂-CH₂-Cl + CaC₂ ---> Cl-(CH₂)₅-C:::C-(CH₂)₅-Cl

Cl-(CH₂)₅-C:::C-(CH₂)₅-Cl + CaC₂ ---> Cl-(CH₂)₅-C:::C-(CH₂)₅-C:::C-(CH₂)₅-Cl


And it looks like could be elongated further with more calcium carbide, but is it possible for it to react with itself form a very large cycloalkyne (maybe as the tetramer, pentamer or hexamer)?  At some point, wouldn't the angle strain be small enough to allow this intramolecular reaction, especially if there's very little 1,5-dichloropentane & carbide present?

And if such a thing could be made, I wonder if it would be useful for supramolecular chemistry purposes.  I guess it could work like a crown ether but maybe better suited for hosting nonpolar molecules (since it's just a big ring of carbons & hydrogens). 

So, what you think?

[movies]

Sounds good to me.  That's a very nice idea.  I bet that you would end up with mostly linear polymer though; once the ring size gets to big it becomes very hard for the ends to find one another.

[wereworm73]

I was thinking of ways around the linear polymer formation.  Aside from keeping the carbide concentration low enough to keep the whole elongation reaction under control, I also figure maybe certain frequencies of IR radiation could bend the C-C:::C bonds to curl the oligomer into reacting with itself.