Rep:Mod:PhysicalLS

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Ls2510 14:12, 22 October 2012 (BST)

The Cope Rearrangement (tutorial)

Mechanism for the Cope rearrangement

Anti Peri-planar Optimisation with HF/3-21G Method/Basis Set

• Energy = -231.69253527 a.u.
• Point Group = Ci

Gauche Optimisation with HF/3-21G Method/Basis Set

• Energy = -231.69166701 a.u.
• Point Group = C2

Optimisation of Ci anti 2 with HF/3-21G Method/Basis Set

• Energy = -231.69253522 a.u. (similar result to the table in Appendix 1)
• Point Group = Ci

Optimisation of Ci anti 2 with B3LYP/6-31* Method/Basis Set

• Energy = -234.61170273 a.u.
• Point group = Ci

The structure hasn't visibly changed from using the HF/3-21G method and basis set, but the energy given is far lower.

Frequency Analysis of 1,5-hexadiene Ci Conformer

• Table of low frequencies shows that there are no negative frequencies - so the optimisation has worked and the structure is at a minimum on the potential energy surface:

 Low frequencies ---  -18.8158  -11.7228   -0.0007   -0.0003   -0.0001    1.7045
 Low frequencies ---   72.7089   80.1376  120.0097

• Energy sums: (extract from .log file)

 Sum of electronic and zero-point Energies=           -234.469212
 Sum of electronic and thermal Energies=              -234.461856
 Sum of electronic and thermal Enthalpies=            -234.460912
 Sum of electronic and thermal Free Energies=         -234.500822

Optimizing the "Chair" and "Boat" Transition Structures

Optimisation of CH2CHCH2 alyl fragment using HF/3-21G Method/Basis Set

• Item table proving the optimisation worked below:

         Item               Value     Threshold  Converged?
 Maximum Force            0.000044     0.000450     YES
 RMS     Force            0.000018     0.000300     YES
 Maximum Displacement     0.000175     0.001800     YES
 RMS     Displacement     0.000073     0.001200     YES
 Predicted change in Energy=-1.235912D-08
 Optimization completed.
    -- Stationary point found.