Question

НСІ 1-methyl-2-vinylcyclobutane 8. In Chem3D draw 5-ethyl-1-methyl-1,3-cyclopentadiene. Find an "energy minimum" of the molecule using an MM2 calculation (button contains black arrow). What is the total steric energy? Provide a 3D model looking down the bond between carbon 5 and the first carbon of the ethyl group. Do you think this is the "most stable" conformation or "global minimum”? Run a few MM2 Dynamics (button contains green-headed arrow) simulations to see if you can jostle the molecule into a more stable conformation upon MM2 minimization. Provide any other results, giving the energies for each.

Answer 1

- H₃C CH₃ The CEC is protonated to give secondary carboncation. That results into sigma bond migration. The driving force for this is releasing ring strain. The resulting secondary carbocation further gives 1,2-hydride shift to give mosre stable 3° carbocation. Finally chloride attacks on this to form C-Cl bond. CH3 CH3 CH3 -CH₃ tr CH34 CH3 H

Upon running the MM2 calculations: Total steric energy = 8.1766 kcal/mol Stretch: Bend: Stretch-Bend: Torsion: Non-1,4 VDW: 1,4 VDW: Dipole/Dipole: Total Energy: Calculation ended 0.2374 8.1992 -0.1018 -0.4133 -1.4541 1.7631 -0.0549 8.1756 kcal/mol This is normal view of the molecule. a 3D view while looking down the bond between C5 and the first carbon of the ethyl group.

After running multiple MM2 dynamics simulations the energy remains the same.