Write 1,2,3-trimethylcyclohexane a conformational structure for in which all the methyl groups are axial and then show its more stable conformation.

Q2. Answer any TWO of the following parts: (a) Draw the two main conformations that exist for cyclohexane. Explain clearly why one conformer is more stable than the other. Using cis-1-ethyl-3-methylcyclohexane, as an example, explain how ring flipping occurs. Draw both conformers of cis-1-ethyl-3-methylcyclohexane and explain clearly which one predominates. (b) What is polarimetry? The specific rotation of (R)-carvone is - 61°. A chemist prepared a 750 mg mixture of (R)-carvone and its enantiomer in 10 ml of ethanol and placed the solution in a 10 cm polarimeter cell. The observed rotation was - 4.125°. Calculate the specific rotation for the above mixture. What is meant by enantiomeric excess? Then determine the % enantiomeric excess (% ee) in the mixture. (i) (ii) (iii) What % of the mixture is (R)-carvone and (S)-carvone?

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

Draw the four possible positions, the cis and trans positions of the methyl groups for both the chair and boat conformations, of 1,4-dimethylcyclohexane. Label each as cis or trans and identify the highest in energy.