Re: Rotational energy barrier for CC triple bond

[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).

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Paul J. Franklin(moderator - sci.chem.organic.synthesis) 
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Georgia State University <[EMAIL PROTECTED]>
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