Talk:Mod:yahoot

Q1. Your calculation results all appear to be good. It is true to say that since the dimerisation gives the thermodynamically least stable product, the reaction must be under kinetic control; you can’t say for certain that the hydrogenation is under thermodynamic control because the thermodynamic product might also be the kinetic product. It is fair to say that molecular hydrogen small enough to avoid major steric interactions, but hydrogenations of this type are usually carried out using a transition metal catalyst by a mechanism that involves complexation of the double bond and transfer of a hydride group from the metal.Bending contributions comprise the biggest difference in the energy of 3 and 4 and you have correctly identified that this corresponds to deviation from ideal bond angles.

Q2. You appear to have minimised the structures of the two pyridinium compound correctly, as the carbonyl groups are pointing in the right direction. However, without the energy values you obtained, it is difficult to judge your calculation efforts. The selectivity of the Grignard attack is correctly explained, as is the reason for the selectivity of aniline attack. Aniline is of course a nucleophile not an electrophile as you wrote, but I imagine that was just a typo. You didn’t address the reason why it is not possible to include the Grignard reagent in the MM2 calculation: this is because the MM2 force field does not contain parameters for Mg and so it wouldn’t “know” what Mg should look like.

Q3. The CO down compound is indeed the lower energy isomer as you found, but your calculated values are a little off. Judging by the jmol it appears that the alkene geometry is incorrect in your model (the hydrogen and bridgehead group should be cis). Your explanation of the stability of the alkene is correct – that is the definition of a hyperstable olefin.

Q4. The MO diagrams appear correct and you have correctly identified the most nucleophilic alkene. The IR frequencies are correct and as you alluded to the C-Cl bond is weakened by an anti double bond due to donation into the sigma* orbital.

MINI PROJECT The compound appears to be a good choice for the activity due to its constrained structure. In the structures that you give you should specify the identity of the group R1. The calculated NMR values are in good agreement with the experimental data (mostly within 4 ppm). It might have been clearer if you had analysed the results in terms of the error between calculation and experimental; it would be interesting to see which isomer’s calculated data match the experimental data closest – this would show whether the computation could differentiate the isomers.