Talk:Mod:hl1910 1

Introduction

Good general introduction but be careful Gaussian is the software that computes the calculations; Gaussview is only the graphical interface.

Cope rearrangement

All conformers successfully optimised. Good discussion about their relative energy. Be careful when interpreting the frequency calculations “Negative values indicates that the vibration is imaginary and either something has gone wrong with the optimisation or frequency analysis.”: all positive frequencies mean the optimised geometry is a minimum on the potential energy surface

The lowest real mode indicates symmetry breaking is uphill in energy and so the reactiwhereas one imaginary frequency means it is a transition state. You must check that for each geometry optimisation. TS successfully optimised but be careful when discussing the methods “both Hartree Fock and Freeze Coordinate method are similar”: computing the force constant at the beginning or using redundant coordinates are 2 ways of optimising the TS. In both ways, you use the quantum chemistry method Hartree-Fock.

There is clearly a mistake in the way you compute activation energies!

Diels Alder

“Only MO with the same symmetry are allowed to react” FMO theory says MOs with the same symmetry interact. The MOs themselves do not react, only molecules do ­ MOs are a way of interpreting the wavefunction of the molecule. The important bond length to look at is the interfragment C­C bond that is forming during the reaction. Where on the PES does this suggest the TS lies with respect to reactants and products? What does the imaginary frequency suggest about symmetry conservation in this reaction? How does that compare to the lowest real frequency.