User talk:Zw3812

Make sure you check for imaginary frequency each time you optimise a structure whether it is a minimum or a TS and state what it means "A minimum structure is characterised by no imaginary frequency".

Did you optimise the geometries for butadiene and ethene? When considering bond distances a partially formed bond that is less than twice the van der waals radius indicates some covalent character. Are the cycloaddion reactions studied synchronous or asynchronous? Which reactant molecular orbitals were responsible for the transition state HOMO/LUMO? Your Jmol transition structures are showing the product not the transition state. Could examine the orbitals of the transition states to look for evidence of secondary ion overlap.