Talk:Mod:slau1991

Introduction Original introduction! In this tutorial, you are using HF and DFT which are quantum mechanics methods – to be able to describe breaking/forming bonds - and not molecular mechanics as written, which can't describe bonds being broken. (Good for conformational changes though). With experience, the errors are easier to find.

Cope rearrangement Be careful: Gaussview is a software that allows you to visualize the molecules, the molecular orbitals for example and to interact with Gaussian – Gaussian actually does the calculation not Gaussview. Good introduction for the Cope rearrangement exercise. All conformers were successfully identified. Good discussion about their relative energy. What are the different goals of running a frequency calculation? When optimizing a minimum, one should check there is no imaginary frequency at this point. Chair and Boat structures successfully identified with the different methods proposed. What do you conclude from the IRC calculation? Which conformers does the Transition State connect? Good interpretation about the preferred mechanism.

Diels-Alder What does the fact that the symmetry breaking mode has a real frequency suggest about the mechanism? Good use of correlation diagrams to illustrate fragment interactions. 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).