WOLFGANG QUAPP, JOSEP MARIA BOFILL   and  Antoni Aguilar-Mogas

for TCA 2011  

Exploration of Cyclopropyl Radical Ring Opening to Allyl Radical
     by Newton Trajectories:
Importance of Valley-Ridge Inflection Points to Understand the Topography.


Abstract:

Valley-ridge inflection points (VRI) on the potential energy surface for
the ring opening of the cyclopropyl radical to allyl radical are determined
using the tool of Newton trajectories 
  [Quapp, W.; Schmidt, B. Theor Chem Acc 2011, 128, 47].
VRIs play a role in the understanding of bifurcating reactions. The region 
where the bifurcation takes place is usually governed by a VRI point. 
For this important ring opening, the knowledge of the VRI point after the
transition state was demanded some years ago 
  [Mann, D.J.; Hase, W.L. J Am Chem Soc 2002, 124, 3208].
Because the transition state is not symmetric, also the 
steepest descent from the transition state is not along a symmetry axis,
and in such cases the steepest descent can fail the VRI point.
That is the case here, indeed, though the pathway of the steepest descent
goes near to a VRI point downhill. 
However, an electronic intersection seam disturbs the relations. 
The exploration of the notorious curvilinear potential energy surface of 
this ring opening has delivered some further VRI points, which are reported.
They give a frame for possible ring opening channels including the
conrotatory case.