Talk:Mod:ll4310 2

Introduction Short general introduction.

Cope rearrangement Good introduction for the Cope rearrangement exercise. All conformers were successfully identified. (Conformers: as well as more functions, have also changed method to B3LYP? So using combination B3LYP/6-31G*.) Good discussion about their relative energy. Frequency calculation well understood and interpreted. Chair and Boat structures successfully identified with the different methods proposed but “the additional keywords opt=noeigen inserted to stop the calculation from crashing if the guess wasn't close enough to the true structure and more than one negative second derivative was found” and not “one minimum value”. Good interpretation of the IRC calculation and about the preferred mechanism.

Diels-Alder The symmetry breaking mode has a real frequency showing that motion along this degree of freedom is uphill in energy (and thus symmetry is conserved through the TS as shown by the imaginary frequency). The parameter labeled as Delta G is in fact the energy of reaction. This value has no temperature dependence and corresponds to the difference in bare electronic energies E(elec) of the reactant and product. To get free energy we have do some conversions: G= H - TS, H=E+RT, E=E(elec)+E(ZPE)+E(vib)+E(rot)+E(trans) Secondary orbital overlaps are a way of explaining reactivity based on an AO FMO approach, however, calculations may not support it and whether they actually exist is a cause of debate (http://pubs.acs.org/doi/abs/10.1021/ar0000152).