identical,

For which isomer would you expect a greater equilibrium percentage of molecules with the alkyl group in the axial position, isopropylcyclohexane or propylcyclohexane? Explain. Isopropylcyclohexane Propylcyclohexane

We have learned that isomers (molecules with the same molecular formula) can have different relationships, and these relationships can be made more clear by comparing IUPAC names. Constitutional isomers will differ in the main part of the name. Stereoisomers will differ only in the stereochemical prefix part of the name (cis/trans). Conformational isomers will actually have the same name, but different energies. Two structures that have the same names and the same energies are identical. What is the relationship between these two structures?

(a) All Isomers have the same molecular formulae. Explain this further. Hint what does it mean to have the same molecular formulae? (b) What is Constitutional (structural) isomerism? Hint, isomers are different, so what is different between a pair of constitutional isomers (see the chart on the last page for examples). (c) What is Conformational isomerism?

How do you account for the difference in energies between the two staggered conformations of 1,2-dichloroethane? How about for the two eclipsed conformations? Draw all four conformations and, on your drawing, indicate sources of strain – torsional, steric (gauche), steric eclipsed.

Chemistry Determine how many substituents in the axial position does the most stable conformer of (1R,2S,4R)-4-bromo-1,2-dimethylcyclohexane have?

(a) What is the IUPAC name for the following molecule (including absolute configurations if required)? (b) Draw the Newman projections looking down the C3-C4 bond that represent all the three staggered conformations for the molecule shown above. (c) Given that the strain energies below, calculate the strain energies for each conformer and identify which is the most stable. Gauche interaction Strain Energy HOCH3 0.0 kJ mol- HOCH;CH; |0.4 kJ mol- 3.8 kJ mol- | 4.3 kJ mol- CH;CH3 CH;CH2CH3 |CH2CH; CH2CH; 4.6 kJ mol- Newman Projection of Conformer 1 Strain Energy of Conformer 1 Newman Projection of Conformer 2 Strain Energy of Conformer 2 Newman Projection of Conformer 3 Strain Energy of Conformer 3

Which of the following is an accurate conformational drawing for compound Z? Z