Problem 1.1:
Please draw the most stable conformations of the following molecules as 3D
chair representations. When relevant, please indicate side chain conformations
as well.
Problem 1.2:
The isomers of dimethylcyclohexane present an interesting opportunity to
examine steric interactions in cyclic compounds. Please rationalize the
following thermodynamic data by (i) drawing out both chair conformations
of each compound, and (ii) indicating the presence of any unfavorable steric
interactions.
Problem 1.3:
Please circle the more stable compound in each of the following pairs and give
a brief rationale for your choice:
Problem 1.4:
Monosubstituted cyclohexanes always prefer to orient their substituent in an
equatorial
position in order to minimize 1,3-diaxial interactions. Consider the following
free
energy data:
Notice that there is relatively little change in going from Me to Et to
I-Pr, but that
there is a large increase in free energy in going to
t-Bu. Draw 3D
conformations of all four
compounds in axial conformations (including side-chain conformations) and
rationalize
this trend. (Optional: What is the name given to the "extra" interaction in
the t-Bu
compound?)
