hw_14

Find the transition state and calculate the barrier height for CH3F + F → CH3F + F with following model.

Model:

Gas/Microsolvation/Continuum Model

method:

MP2/aug-cc-pVDZ (Data) 

Gas ( TS : input,output  Reactant : input,output  irc : output )

Gas phase    
TS -239.10423  
Reactant -239.10534  
Barrier Height 0.00111 Hartree
  0.7 kcal/mol

1

 

Microsolvation( TS : input,output  Reactant : input,output irc : output)

Microsolvation    
TS -315.37294  
Reactant -315.40634  
Barrier Height 0.03340 Hartree
  21.0 kcal/mol

1

 

Continuum Model ( TS : input,output  Reactant : input,output irc : output )

Continuum    
TS -239.18791  
Reactant -239.22035  
Barrier Height 0.03244 Hartree
  20.4 kcal/mol

s

Conclusion :

From the Microsolvation experimental data, it can be known that the solvent effect leads to an increase for energy barrier of sn2 reaction.

The Continuum model focuses on the charge distribution polarization of the solute molecules, this polarization produces an electric field called Reaction Field, and the electric field interacts with the charge distribution of solute molecules to further reduce the energy of solute molecules. This is called the electrostatic contribution of the solute effect. important contribution.