91Ó°ÊÓ

Label the two stereogenic centers in each compound and draw all possible stereoisomers: (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}(\mathrm{Cl}) \mathrm{CH}(\mathrm{OH}) \mathrm{CH}_{2} \mathrm{CH}_{3} ;\) (b) \(\mathrm{CH}_{3} \mathrm{CH}(\mathrm{Br}) \mathrm{CH}_{2} \mathrm{CH}(\mathrm{Cl}) \mathrm{CH}_{3}\).

Which group in each pair is assigned the higher priority in \(R, S\) nomenclature? a. \(-\mathrm{OH},-\mathrm{NH}_{2}\) d. \(-\mathrm{CH}_{2} \mathrm{Cl},-\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}\) b. \(-\mathrm{CD}_{3},-\mathrm{CH}_{3}\) e. \(-\mathrm{CHO},-\mathrm{COOH}\) c. \(-\mathrm{CH}\left(\mathrm{CH}_{3}\right)_{2},-\mathrm{CH}_{2} \mathrm{OH}\) f. \(-\mathrm{CH}_{2} \mathrm{NH}_{2},-\mathrm{NHCH}_{3}\)

Draw the two enantiomers for the amino acid leucine, \(\mathrm{HOOCCH}\left(\mathrm{NH}_{2}\right) \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right)_{2}\), and label each enantiomer as \(R\) or \(\mathrm{S}\). Only the \(S\) isomer exists in nature, and it has a bitter taste. Its enantiomer, however, is sweet.

The \([\alpha]\) of pure quinine, an antimalarial drug, is \(-165 .\) a. Calculate the ee of a solution with the following \([\alpha]\) values: \(-50,-83\), and \(-120\). b. For each ee, calculate the percent of each enantiomer present. c. What is \([\alpha]\) for the enantiomer of quinine? d. If a solution contains \(80 \%\) quinine and \(20 \%\) of its enantiomer, what is the ee of the solution? e. What is \([\alpha]\) for the solution described in part (d)?