4. Alkanes and Cycloalkanes

Estimate the equilibrium composition of the chair conformers of the following cyclohexanes at room temp:

cis-1,3-diethylcyclohexane

Estimate the equilibrium composition of the chair conformers of trans-1-methyl-3-phenylcyclohexane at room temperature.

The ∆G° for conversion of “axial” fluorocyclohexane to “equatorial” fluorocyclohexane at 25 °C is -0.25kcal>mol. Calculate the percentage of fluorocyclohexane molecules that have the fluoro substituent in an equatorial position at equilibrium.

b. Why is the percentage of molecules with the substituent in an equatorial position greater for

isopropylcyclohexane than for fluorocyclohexane?

(••) The A value of a substituent on a cyclohexane ring is essentially the ∆G° for a substituent going from the equatorial to the axial position in a chair–chair interconversion. Because most substituents prefer to be in the equatorial position, A values are, by definition, positive numbers. Use the table of A values to calculate ∆G° and K_eq for the chair–chair interconversions shown. <IMAGE>

(a) <IMAGE>