Talk:Mod:3080ecm10mod3

Introduction

Very good introduction.

Cope rearrangement

All conformers were successfully identified with a short discussion about their relative energy. But you could have labeled the conformer in the way as in the instruction wiki! Good interpretation of the frequency calculation. Chair and Boat structures successfully identified with the different methods proposed. Be careful: “Despite such similarly, the structures generated by Gaussian for each optimisations are very different. The first one, corresponding to the Hartree-Fock method, has one and a half bonds across each C-C bond (single + dotted), whereas the second optimisation just has double bonds across all C- C bonds. Structurally, the latter bond structure is incorrect with respect to the number of hydrogen atoms “As can be seen in the above table, the central oxygen on the maleic anhydride contributes less to the overall bonding and antibonding of the LUMO and HOMO for the exo product than the endo product. This is due to oxygen being highly electronegative. ” Oxygen is equally eletronegative in both isomers. each carbon is bound to.” -> the chemical bonds are drawn by Gaussview according to the atomic distances. You thus should not refer to them to get information about the electron density. Good interpretation of the IRC calculation. What do you conclude about the preferred mechanism?

Diels-Alder

The symmetries of the butadiene and ethene fragments are given wrt the wrong plane. There is an orthogonal plane which gives information on the reactivity (think about the plane of symmetry present in the TS). How does the forming bond length compare to the average C(sp3)-C(sp3) bond length. How does this compare to 2x the van der waals distance of a carbon atom. “The first real vibration, in comparison, is merely the rotation of the two molecules in opposite directions about the same axis - it does not yield much information about the transition state; it even suggests that the formation of the bonds would be asynchronous.” But because it is associated with a real frequency it suggests that moving along this degree of freedom is uphill in energy and so symmetry breaking is not present through the TS. MO diagram shows correct fragments but is not complete. LUMO of butadiene also interacts with HOMO of ethane. Can you illustrate the presence of secondary orbital overlap in your computed MOs. How does this compare to your hypothetical FMO illustration.