The Model
Henry S. Rzepa and Christopher Leach
This was performed at the PM3 level with H2N=CH2 (+) as a hydride acceptor from a H-C-OH
system. Two transition states are currently identified, with energies of 101.2 and
97.8 kcal/mol, a difference of 3.4 kcal/mol. The details are shown below
| Low energy
|
|---|
| 97.8
|
|
| High Energy
|
|---|
| 101.2
|
|
Click on the diagram to activate RasMol. If you don't know how to do this, its
practice for my talk!!
The Theory
It looks uncannily like the reverse of the epoxidation system we published a year or so back.
There, the C-CF3 bond was in the plane of a ¼ system so as not to
deactivate the nucleophilic p orbitals towards the electrophile. Here, we have in effect
a nucleophilic hydride, and a C-F bond effectively orthogonal to an incipient ¼ system
system activating the p orbitals towards nucleophilic attack. Almost the exact oppposite of
before! The favoured ts has a "W", although the central CH2 is bent out of plane
by virtue of the conjugation of the hydroxyl group.
Next Steps
We want to repeat at the ab initio level, construct contour diagrams, try CF3 groups,
and replace the imino group with a proper NADH system.
But I think we have the start of a theory here.