CH 241F EXPERIMENT #2 CHEMICAL RESOLUTION OF (±)-PHENYLSUCCINIC ACID WITH (-)-PROLINE Prelab Week 1 2. Provide the structures for the group abbreviations “Ph” and “CO2H”. O
Ph
CO2H
=
= OH
3. The (-) form of phenylsuccinic acid has the R-configuration and the (+) form has the S-configuration. Draw the two enantiomers in your notebook, clearly showing the configuration around the stereogenic atom.
H
HOOC CH2 COOH
HOOC
CH2 COOH H
R form
S form
4. Determine the configuration of (-)-proline whose structure is given on the first page of this handout. O H N (S)
OH H
(-) proline
5. Draw the structure of the bis proline salt of (+)-phenylsuccinic acid. Remember that the salt formation is just an acid-base reaction (Hints: Reread the introduction. Which atom in (-) proline can abstract the acidic proton from (+)-phenylsuccinic acid?). O
H2 N
O
OH
Ph H
O O
O
H2 N
O
OH H
6. Prepare a flow chart that summarizes the resolution of racemic phenylsuccinic acid. The flow chart should include the protocol for either recovering enriched (-) phenylsuccinic acid or for purifying the (-)-phenylsuccinic acid, whichever, you plan on doing in lab.
(rac)-phenylsuccinic acid Add (–)-proline, filter
mother liquor
solid
enriched (–)-phenylsuccinic acid and (–)-proline acidify and filter
enriched (–)-phenylsuccinic acid
Bis-proline salt of (+)-phenylsuccinic acid acidify and filter
(+)-phenylsuccinic acid
