MS 900 - Conformers and Cyclohexane Practice

MS 900 - Conformers and Cyclohexane Practice

Textbook and Chapter: Carey and Giuliano 8th Ed. (2010), Chapter 3

Keywords: conformational analysis, cyclohexane chair forms

Description: Reviews cyclohexane chair forms and conformations of butane:

  • Which dimethylcyclohexane is more stable 1,2-cis or 1,2-trans? Why?
  • Drawing chair forms
  • E2 anti-coplanar conformation and chair forms
  • Newman projects

Total Problems: 4

  1. Problem # 317


    α-D-Glucose is shown below. Draw its two chair forms. Which conformation is more stable? Explain.

    I recommend using the common convention wedge = "up" and dash = "down."



  2. Problem # 318

    Two stereoisomers of trimethylcyclohexane are shown below (compounds A and B). Compare cyclohexane chair forms to determine which isomer has a lower heat of combustion. Explain your reasoning.


  3. Problem # 319

    For a molecule to undergo an E2 reaction, the leaving group and the beta-proton must be in an anti-coplanar conformation (one atom straight up, the other straight down). Based on this, which compound undergoes E2 reaction with KOtBu faster? Why?


  4. Problem # 320


    Let's perform conformational analysis on 2-methylbutane along the C2-C3 bond. We'll use the energy chart given below.


    First, draw out the Newman projections along the C2-C3 bond, rotating the front carbon (C-2) by 60 degrees clockwise each time while keeping the back carbon (C-3) stationary.

    According to the table above, how much energy does each conformation "cost?"


    Second, make a plot of the total energy value for each Newman projection versus its dihedral angle.