Re: Rotational energy barrier for CC triple bond

Uncle Al <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> [EMAIL PROTECTED] wrote:

> > I am trying to get a "quick and dirty" value for the rotational energy
> > barrier in a CC triple bond.  As a first guess, I would say about
> > twice the value for a CC double bond.   Any data  that speak
> > against this or for it?

>   1) The CC triple bond is rigid - LCAO model with two orthogonal
> pairs of overlapping pi orbitals.
>   2) The CC triple bond has unhindered rotation - MO theory with a
> symmetric cylinder of bonding pi-electron density. 

> Perhaps somebody ought to do a quadrupole moment measurement of
> acetylene.  Being a synthetic organiker, my heart is with (1) but my
> head is with (2).

> Uncle Al
> http://www.mazepath.com/uncleal/
>  (Toxic URL! Unsafe for children and most mammals)
> "Quis custodiet ipsos custodes?"  The Net!



Symmetry says it.  It is linear.  There is no way to tell whether you
have "rotate" that bond or not let alone the energy for such process.
so (3) there is no such kind of rotation.

bch


-- 
Paul J. Franklin(moderator - sci.chem.organic.synthesis) 
http://organicworldwide.net/sci.chem.organic.synthesis
Georgia State University <[EMAIL PROTECTED]>
Atlanta, GA
-- 
Paul J. Franklin(moderator - sci.chem.organic.synthesis) 
http://organicworldwide.net/sci.chem.organic.synthesis
Georgia State University <[EMAIL PROTECTED]>
Atlanta, GA