Unusual reaction paths of SN2 nucleophile substitution reactions
ch4+h^- -- > ch4+h^- and ch4+f^-  -- > ch3F+h^-: 
Quantum chemical calculations

Ruslan. M. Minyaev a*, Wolfgang Quapp b*, Benjamin Schmidt b, 
Ilya V. Getmanskii a,  Vitaliy V. Koval a


a Institute of Physical and Organic Chemistry, Southern Federal University,
  194/2 Stachka Ave., Rostov-on-Don 344090, Russian Federation;
b Leipzig University, Mathematical Institute, Augustusplatz, D-04109
  Leipzig, Germany


Abstract

Quantum chemical (CCSD(full)/6-311++G(3df,2pd),
CCSD(T)(full)/6-311++G(3df,2pd)) and density function theory
(B3LYP/6-311++G(3df,3pd))  calculations were performed for the  sn2
nucleophile substitution reactions ch4+h^- -- > ch4+h^- and 
ch4+f^- -- > ch3F+h^-. The calculated gradient reaction pathways for both 
reactions have an unusual behavior.  An unusual saddle point of index 2 
lies on the gradient reaction path. 
Using Newton trajectories for the reaction path, we can detect VRI points 
at which the reaction path branches. 

submitted to Chemical Physics 2013