Talk:Organic:whoisthedaddy

Q1. Your results are all good. As you pointed out, the exo dimerisation product is thermodynamically more stable; since the endo product is the one actually formed, that indicates the reaction must be under kinetic control. Bending is indeed the major difference in energy contributions for the hydrogenated compounds, but this relates to deviation from ideal bond angle, not steric interactions.

Q2. I think you mean that the 4 position is the most ELECTROPHILIC position. Your calculation for the first pyridinium is a little off, but the rest is fine. The Grignard reagent adds on the opposite face to the carbonyl group for the reasons you discuss, but the reason the aniline nucleophile attacks the opposite side is due to electrostatic repulsion between lone pairs on the nitrogen and the carbonyl oxygen.

Q3. Technically what you used to minimise the energies was molecular mechanics (not molecular dynamics). Your energy for the “up” isomer is about right, but the other isomer should be lower; the lower energy “down” isomer can be obtained by optimising the cyclohexane unit. The alkene is indeed a hyperstable alkene the full definition is that the strain experienced by the unsaturated system (e.g. the alkane) is greater than for the saturated system (e.g. the alkene).

Q4. Your calculations and MO diagrams appear to be good and you have correctly identified the most nucleophilic alkene. Your discussion of the changes in the IR spectrum are correct, but perhaps it would be useful to show the differences in stretches and bond lengths depending on whether there are one or two double bonds.

MINI PROJECT You correctly identified that the molecules could be told apart by the appearance of an OH stretch in the IR spectrum – also you would see the disappearance of the carbonyl stretch. To distinguish between the two isomers of the product, analysis of the J coupling may be useful, but I you won’t see a coupling between the OH proton and a proximal CH proton because the location of the OH proton will become averaged due to its lability. Your calculated data of the down isomer certainly seem to fit the experimental values most closely than the up isomer; it might have been interesting to see a table of differences between calculated and experimental values to show this.